Single-tooth impl ants

Single-tooth impl ants in the aesthetic zone A clinical trial of different implant neck designs and immediate loading L aurens den Hartog Single-to...
Author: Caitlin Weaver
6 downloads 4 Views 6MB Size
Single-tooth impl ants in the aesthetic zone A clinical trial of different implant neck designs and immediate loading

L aurens den Hartog

Single-tooth implants in the aesthetic zone A clinical trial of different implant neck designs and immediate loading

The research presented in this thesis was performed at the Department of Oral and Maxillofacial Surgery, University Medical Center Groningen, The Netherlands. This research project was supported by: Nobel Biocare; study contract: Single tooth replacements with dental implants in the aesthetic zone (Study number 2004-288) Oral-maxillofacial Reconstructive and Implant Surgery related Research Foundation (ORIS Research Foundation) Publication of this thesis was supported by: Tandtechnisch en Maxillofaciaal Laboratorium Gerrit van Dijk E.S. Healthcare NV (www.isus.be) Biomet 3i Netherlands BV (www.biomet3i.nl) Dentsply Friadent Benelux NV (www.dentsply-friadent.nl) Nobel Biocare Nederland BV (www.nobelbiocare.nl) Straumann BV (www.straumann.nl) Dent-Med Materials BV (Geistlich Bio-Oss®, Geistlich Bio-Gide®) (www.dent-medmaterials.nl) Nederlandse Vereniging voor Orale Implantologie (www.nvoi.nl) Nederlandse Maatschappij tot bevordering der Tandheelkunde (www.nmt.nl) Nederlandse Vereniging voor Gnathologie en Prothetische Tandheelkunde (www.nvgpt.nl) Nederlandse Vereniging voor Mondziekten, Kaak- en Aangezichtschirurgie (www.nvmka.nl) Dental Union (www.dentalunion.nl) Van Velthuysen Liebrecht, financiele dienstverleners (www.velthuysen.nl) University of Groningen (www.rug.nl) Lay-out & Cover: Saar de Vries Printing: Drukkerij van der eems Heerenveen Publisher: Laurens den Hartog, Groningen ISBN: 978-90-367-4759-2

©Laurens den Hartog, 2010 All rights reserved. No part of this publication may be reported or transmitted, in any form or by any means, without prior permission of the author.

rijksuniversiteit groningen

Single-tooth implants in the aesthetic zone A clinical trial of different implant neck designs and immediate loading

Proefschrift ter verkrijging van het doctoraat in de Medische Wetenschappen aan de Rijksuniversiteit Groningen op gezag van de Rector Magnificus, dr. F. Zwarts, in het openbaar te verdedigen op woensdag 26 januari 2011 om 16.15 uur door

Laurens den Hartog geboren op 9 september 1980 te Steenwijk

Promotores:

Prof. dr. G.M. Raghoebar Prof. dr. H.J.A. Meijer Prof. dr. A. Vissink

Beoordelingscommissie:

Prof. dr. G.J. Meijer Prof. dr. E. Rompen Prof. dr. D. Wismeijer

Paranimfen:

Drs. H.J. Santing Dr. N. Tymstra

1.

Among people, there are many opinions about the contribution of teeth to aesthetic appearance. This is illustrated in a recent newspaper article (Blandy 2009) in which a popular phenomenon was described among some youngsters in Cape Town, South Africa, in whom their healthy incisors had been extracted as fashion statement: “The laughing young man has a perfect set of teeth…..Suddenly he pops out a pair of dentures, revealing a gap-toothed smile, a common sight among mixedrace Capetonians that has spawned outrageous myths and stereotypes. […] “It is fashion, everyone has it,” said 21-year-old Yazeed Adams, who insists he had to take out his healthy incisors because they were “huge”. Ronald de Villiers, 45: “my 11 year-old and 14 year-old had already had their teeth out “to look a bit prettier”….. In contrast to this phenomenon, in Western world, a missing anterior tooth is not considered as being an image of beauty and might have a serious impact on the individual’s life. Usually, these individuels have a strong wish for a prosthetic replacement to rehabilitate function and aesthetics. Dental implants have conquered a prominent role in contemporary dentistry when it comes to single-tooth replacements. Excellent long-term survival rates (Scheller et al. 1998, Romeo et al. 2002), psychological benefits for the patient and tooth structure conservation, attribute to the growing popularity of dental implants at the cost of conventional bridgework, resin-bonded restorations and removable partial dentures. When primarily the focus was on survival of the implant, currently creation of a high quality restoration for the long-term, satisfying the criteria that reflect function and aesthetics is the ultimate ambition, particularly in aesthetically delicate areas. It is accepted that after implant placement and through time of function, implants will display some extent of bone loss (Albrektsson et al. 1986, Laurell & Lundgren 2009). However, peri-implant marginal bone loss should be limited, since bone loss may induce pocket formation, which could be unfavorable for long-term health of the peri-implant tissues (Rams et al. 1984, Heydenrijk et al. 2002). From an aesthetic point of view, it is also important to minimize marginal 7

Introduction

Introduction

1

Chapter

1

bone loss. Namely, the level of the peri-implant marginal bone is strongly related to the level of the peri-implant mucosa (Bengazi et al. 1996, Hermann et al. 1997, Chang et al. 1999, Hermann et al. 2000, Hermann et al. 2001). Loss of marginal bone might therefore affect the level of the peri-implant mucosa, which, in turn, is commonly considered as a major factor determining the aesthetic outcome (Furhauser et al. 2005, Meijer et al. 2005). There is evidence that the design of the implant neck influences the extent of marginal peri-implant bone loss (Shin et al. 2006, Lee et al. 2007, McAllister 2007, Bratu et al. 2009, Nickenig et al. 2009). Although the traditional smooth implant neck is accompanied by the least accumulation of plaque (Teughels et al. 2006, Baldi et al. 2009), several studies found that a rough-surfaced implant neck was accompanied by a significant reduction of marginal bone loss when compared with a smooth implant neck (Shin et al. 2006, Bratu et al. 2009, Nickenig et al. 2009). It has been suggested that an increase in implant surface roughness improves bone integration in terms of the quantity and quality of bone formation at the implant-bone interface (Cooper 2000). It is likely that, when incorporated in the implant neck, these rough surface qualities are responsible for reducing marginal bone loss. Furthermore, it has been reported that retention elements at the implant neck, such as grooves or microthreads, favor the preservation of marginal bone (Palmer et al. 2000, Shin et al. 2006, Lee et al. 2007). It is believed that these microthreads bring about a major decrease in interfacial shear stress on the cortical bone, resulting in less marginal bone loss (Hansson 1999). In addition to the surface characteristics of the implant neck, it has been suggested that a scalloped implant platform might preserve proximal marginal bone (Wohrle 2003, Kan et al. 2007, McAllister 2007). This hypothesis was based on the thought that a scalloped implant neck mirrors the natural alveolar ridge curvature, particularly in the anterior zone, and consequently a more non-violent position of the implant-abutment interface can be realized compared to common flat platform implant designs. Apart from the role of the implant neck design, the concept of immediate loading has gained attention in contemporary implantology. This concept is defined as the application of a load by means of a restoration within 48 hours after implant placement (Laney 2007) and deviates from the conventional load-free healing period of several months. Patients in need for an anterior single-tooth replacement may benefit from immediate loading. Placement of the (provisional) implant crown immediately after implant placement reduces overall treatment time, avoids a second-stage operation and offers immediate oral comfort as there is no need for a provisional removable prosthesis during the healing phase. Furthermore, it has been hypothesized that immediate loading might be advantageous for the appearance of the peri-implant soft tissue, since healing occurs 8

The specific aims of this thesis were: to review systematically the literature regarding the efficacy of single implant therapy in the aesthetic zone (Chapter 2); - to compare the marginal bone level change and clinical outcome of implants with a 1.5 mm smooth neck, a rough neck with grooves and a scalloped rough neck with grooves used for single-tooth replacements in the maxillary aesthetic region (Chapter 3); - to evaluate the aesthetic outcome of the above mentioned implant neck designs from a professional’s and patient’s perception (Chapter 4); - to compare immediate loading with conventional loading of single-tooth implants in the aesthetic zone for marginal bone level change, clinical and aesthetic outcome and patient satisfaction (Chapter 5). -

The immediate loading protocol of our study is illustrated in a detailed clinical report (Chapter 6). Furthermore, a chapter is devoted to how to treat a trauma to an anterior implant crown (Chapter 7).

9

Introduction

against a natural form immediately after implant surgery (Glauser et al. 2006). Besides the beneficial effects of immediate loading, this loading concept has also some inherent thought disadvantages. Amongst others, immediate loading may induce micromotion and instability of the implant (Gapski et al. 2003, Trisi et al. 2009). Next, implant instability may result in fibrous encapsulation of the implant and failing osseointegration (Lioubavina-Hack et al. 2006). There is, however, a paucity of well-designed trials addressing the effect of the implant neck design on bone and soft tissue parameters. Furthermore, the aesthetic outcome and patient satisfaction are underexposed in anterior single implant research (Belser et al. 2004). The same shortcomings apply to trials investigating immediate implant loading as being a reliable strategy to replace an anterior tooth (Gapski et al. 2003). To gain more insight into the questions raised in this and the previous paragraphs, the general aims of this thesis were: - to compare the treatment outcome of single-tooth implants with different neck designs placed in the maxillary aesthetic zone; - to compare the treatment outcome of immediate loading with conventional loading of single-tooth implants placed in the maxillary aesthetic zone.

1

References Albrektsson, T., Zarb, G., Worthington, P. & Eriksson, A.R. (1986) The long-term efficacy of currently used dental implants: a review and proposed criteria of success. International Journal of Oral and Maxillofacical Implants 1, 11-25. Baldi, D., Menini, M., Pera, F., Ravera, G. & Pera, P. (2009) Plaque accumulation on exposed titanium surfaces and periimplant tissue behavior. A preliminary 1-year clinical study. International Journal of Prosthodontics 22, 447-455. Belser, U.C., Schmid, B., Higginbottom, F. & Buser, D. (2004) Outcome analysis of implant restorations located in the anterior maxilla: a review of the recent literature. International Journal of Oral and Maxillofacical Implants 19 Suppl, 30-42.

Chapter

1

A histometric evaluation of unloaded non-submerged and submerged implants in the canine mandible. Journal of Periodontology 71, 1412-1424. Hermann, J.S., Buser, D., Schenk, R.K., Schoolfield, J.D. & Cochran, D.L. (2001) Biologic Width around one- and two-piece titanium implants. Clinical Oral Implants Research 12, 559-571. Hermann, J.S., Cochran, D.L., Nummikoski, P.V. & Buser, D. (1997) Crestal bone changes around titanium implants. A radiographic evaluation of unloaded nonsubmerged and submerged implants in the canine mandible. Journal of Periodontology 68, 1117-1130. Heydenrijk, K., Meijer, H.J., van der Reijden, W.A., Raghoebar, G.M., Vissink, A. & Stegenga, B. (2002) Microbiota around root-form endosseous implants: a review of the literature. International Journal of Oral and Maxillofacical Implants 17, 829-838.

Bengazi, F., Wennstrom, J.L. & Lekholm, U. (1996) Recession of the soft tissue margin at oral implants. A 2-year longitudinal prospective study. Clinical Oral Implants Research 7, 303-310. Blandy, F. (2009) Cape Town’s passion gap: sexual myth or fashion victimhood? Telegraph.co.uk Bratu, E.A., Tandlich, M. & Shapira, L. (2009) A rough surface implant neck with microthreads reduces the amount of marginal bone loss: a prospective clinical study. Clinical Oral Implants Research 20, 827-832. Chang, M., Wennstrom, J.L., Odman, P. & Andersson, B. (1999) Implant supported single-tooth replacements compared to contralateral natural teeth. Crown and soft tissue dimensions. Clinical Oral Implants Research 10, 185-194. Cooper, L.F. (2000) A role for surface topography in creating and maintaining bone at titanium endosseous implants. Journal of Prosthetic Dentistry 84, 522-534. Furhauser, R., Florescu, D., Benesch, T., Haas, R., Mailath, G. & Watzek, G. (2005) Evaluation of soft tissue around single-tooth implant crowns: the pink esthetic score. Clinical Oral Implants Research 16, 639-644. Gapski, R., Wang, H.L., Mascarenhas, P. & Lang, N.P. (2003) Critical review of immediate implant loading. Clinical Oral Implants Research 14, 515-527. Glauser, R., Zembic, A. & Hammerle, C.H. (2006) A systematic review of marginal soft tissue at implants subjected to immediate loading or immediate restoration. Clinical Oral Implants Research 17 Suppl 2, 82-92. Hansson, S. (1999) The implant neck: smooth or provided with retention elements. A biomechanical approach. Clinical Oral Implants Research 10, 394-405. Hermann, J.S., Buser, D., Schenk, R.K. & Cochran, D.L. (2000) Crestal bone changes around titanium implants.

10

Kan, J.Y., Rungcharassaeng, K., Liddelow, G., Henry, P. & Goodacre, C.J. (2007) Periimplant tissue response following immediate provisional restoration of scalloped implants in the esthetic zone: a one-year pilot prospective multicenter study. Journal of Prosthetic Dentistry 97, S109-S118. Laney, W.R. (2007) Glossary of Oral and Maxillofacial Implants. Berlin:Quintessence. Laurell, L. & Lundgren, D. (2009) Marginal Bone Level Changes at Dental Implants after 5 Years in Function: A Meta-Analysis. Clinical Implant Dentistry and Related Research 3 [Epub ahead of print]. Lee, D.W., Choi, Y.S., Park, K.H., Kim, C.S. & Moon, I.S. (2007) Effect of microthread on the maintenance of marginal bone level: a 3-year prospective study. Clinical Oral Implants Research 18, 465-470. Lioubavina-Hack, N., Lang, N.P. & Karring, T. (2006) Significance of primary stability for osseointegration of dental implants. Clinical Oral Implants Research 17, 244-250. McAllister, B.S. (2007) Scalloped implant designs enhance interproximal bone levels. International Journal of Periodontics and Restorative Dentistry 27, 9-15. Meijer, H.J., Stellingsma, K., Meijndert, L. & Raghoebar, G.M. (2005) A new index for rating aesthetics of implantsupported single crowns and adjacent soft tissues--the Implant Crown Aesthetic Index. Clinical Oral Implants Research 16, 645-649. Nickenig, H.J., Wichmann, M., Schlegel, K.A., Nkenke, E. & Eitner, S. (2009) Radiographic evaluation of marginal bone levels adjacent to parallel-screw cylinder machined-neck implants and rough-surfaced microthreaded implants using digitized panoramic radiographs. Clinical Oral Implants Research 20, 550-554.

Palmer, R.M., Palmer, P.J. & Smith, B.J. (2000) A 5-year prospective study of Astra single tooth implants. Clinical Oral Implants Research 11, 179-182. Rams, T.E., Roberts, T.W., Tatum, H., Jr. & Keyes, P.H. (1984) The subgingival microbial flora associated with human dental implants. Journal of Prosthetic Dentistry 51, 529-534.

Introduction

Romeo, E., Chiapasco, M., Ghisolfi, M. & Vogel, G. (2002) Long-term clinical effectiveness of oral implants in the treatment of partial edentulism. Seven-year life table analysis of a prospective study with ITI dental implants system used for single-tooth restorations. Clinical Oral Implants Research 13, 133-143. Scheller, H., Urgell, J.P., Kultje, C., Klineberg, I., Goldberg, P.V., Stevenson-Moore, P., Alonso, J.M., Schaller, M., Corria, R.M., Engquist, B., Toreskog, S., Kastenbaum, F. & Smith, C.R. (1998) A 5-year multicenter study on implantsupported single crown restorations. International Journal of Oral and Maxillofacical Implants 13, 212-218.

1

Shin, Y.K., Han, C.H., Heo, S.J., Kim, S. & Chun, H.J. (2006) Radiographic evaluation of marginal bone level around implants with different neck designs after 1 year. International Journal of Oral and Maxillofacical Implants 21, 789-794. Teughels, W., Van Assche, N., Sliepen, I. & Quirynen, M. (2006) Effect of material characteristics and/or surface topography on biofilm development. Clinical Oral Implants Research 17 Suppl 2, 68-81. Trisi, P., Perfetti, G., Baldoni, E., Berardi, D., Colagiovanni, M. & Scogna, G. (2009) Implant micromotion is related to peak insertion torque and bone density. Clinical Oral Implants Research 20, 467-471. Wohrle, P.S. (2003) Nobel Perfect esthetic scalloped implant: rationale for a new design. Clinical Implant Dentistry and Related Research 5 Suppl 1, 64-73.

11

2. Treatment outcome of immediate, early and conventional single-tooth implants in the aesthetic zone A systematic review to survival, bone level, soft tissue, aesthetics and patient satisfaction

This chapter is an edited version of the manuscript: Den Hartog, L., Huddleston Slater J.J., Vissink, A., Meijer, H.J., Raghoebar, G.M. Treatment outcome of immediate, early and conventional singletooth implants in the aesthetic zone. A systematic review to survival, bone level, soft tissue, aesthetics and patient satisfaction. Journal of Clinical Periodontology 2008; 35: 1073 - 1086

Abstract Aim: To evaluate, through a systematic review of the literature, the outcome of single-tooth implants in the aesthetic zone with natural adjacent teeth, thereby addressing immediate, early and conventional implant approaches. Material and Methods: MEDLINE (1950-2008), EMBASE (1966-2008), and CENTRAL (1800-2008) were searched to identify eligible studies. Two reviewers independently assessed the methodological quality using specific study-design related assessment forms.

Chapter

2

Results: Out of 86 primarily selected articles, 19 studies fulfilled the inclusion criteria. A meta-analysis showed an overall survival rate of 95.5% (95% CI: [93.0 – 97.1]) after one year. A stratified meta-analysis revealed no differences in survival between immediate, early and conventional implant strategies. Minor marginal peri-implant bone resorption was found together with low incidence of biological and technical complications. No significant differences in outcome measures were reported in clinical trials comparing immediate, early or conventional implant strategies. Conclusion: The included literature suggest that promising short-term results can be achieved for immediate, early and conventional single-tooth implants in the aesthetic zone. However, important parameters as aesthetic outcome, soft tissue aspects and patient satisfaction were clearly underexposed. The question whether immediate and early single implant therapies will result in better treatment outcomes remains inconclusive due to lack of well-designed controlled clinical studies.

14

The application of dental implants for single-tooth replacements has evolved into a viable prosthodontic alternative to conventional fixed bridgework, resin-bonded restorations or removable partial dentures. Long-term studies have reported excellent implant survival rates when applied for single-tooth replacements (Scheller et al. 1998, Romeo et al. 2002). Psychological benefits and tooth structure conservation adjacent to the tooth to be replaced, are among the advantages of implant supported restorations. In the anterior zone, the success of single-tooth implant therapy is not only determined by high survival rates, but even more by the (long-term) quality of survival, dictated by a mixture of several factors. Preferably, the appearance of the peri-implant soft tissue should be in harmony with the mucosa around the adjacent teeth and the implant crown should be in balance with the neighbouring dentition (Meijer et al. 2005). Various implant treatment strategies have been proposed for the accomplishment of optimal aesthetics. These include approaches to rehabilitate the underlying bone structures by augmentation procedures with autologous bone and/or bone substitutes (Weber et al. 1997, Jensen et al. 2006, Pelo et al. 2007), techniques to manipulate and enhance the architecture of the periimplant soft tissue (Zetu & Wang 2005, Esposito et al. 2007) and methods for alveolar ridge preservation following tooth extraction (Lekovic et al. 1997, Irinakis & Tabesh 2007). Furthermore, implants and abutments with specific configurations have been introduced to sustain the hard and soft tissue (Wohrle 2003, Morton et al. 2004, Lazzara & Porter 2006, Maeda et al. 2007, Noelken et al. 2007) together with provisionalization techniques to restore the soft tissue contour (Jemt 1999, Al-Harbi & Edgin 2007), and the introduction of ceramic customized abutments and ceramic implant crowns (Canullo 2007, Schneider 2008). Traditionally, dental implants were placed in healed extraction sites according to a two-stage surgical procedure and an undisturbed load-free period of three to six months. In contemporary implantology, however, installation of implants in fresh extraction sockets and reducing the load-free period by immediate restoring implants after insertion have gained attention. Besides shortening of total treatment time, fewer surgical interventions and eliminating the need for a temporary prosthesis, these immediate approaches might lead to a reduction of peri-implant crestal bone loss and a better soft tissue healing thus possibly improving the aesthetics (Esposito et al. 2006, Glauser et al. 2006, Harvey 2007). On the other hand, there are potential risk factors involved with these techniques such as enhanced possibility of infection, mismatch between socket wall and implant leading to gap creation and induction of fibrous tissue formation around the bone-implant interface caused by implant micromovement during eventful wound healing (Gapski et al. 2003, Esposito et al. 2006). These risk factors may 15

Systematic review

Introduction

2

Chapter

2

worsen the treatment outcome. This discrepancy needs further study. The outcome of a single-tooth implant with natural neighbouring teeth may be dissimilar to cases in which multiple adjacent teeth are replaced by dental implants, because dimensions of the hard and soft tissue between adjacent implants differ significantly from dimensions found in single implant cases. Single implant cases take benefit of tissue support of the adjacent dentition (Grunder 2000, Kan et al. 2003b, Belser et al. 2004). When considering the heights of inter-implant papillae for instance, studies indicated that these papillae might show inadequacy for complete enclosure of the inter-implant area with soft tissue, thereby failing to duplicate the interproximal soft tissue appearance of the adjacent teeth (Tarnow et al. 1992, Tarnow et al. 2003, Lee et al. 2005). This deficiency may affect the aesthetic outcome unfavorably. The soft tissue height proximal to single-tooth implants is on average higher and is suggested to be related to the interproximal bone level of the adjacent teeth (Grunder 2000, Kan et al. 2003b). Hence, singletooth implant therapy may lead to more favorable treatment outcomes compared to a therapy in which adjacent implants are involved. To date, several reviews have been published regarding the clinical outcome of immediate and conventional implant supported single-tooth restorations in partially edentulous patients (Creugers et al. 2000, Berglundh et al. 2002, Belser et al. 2004, Glauser et al. 2006, Jung et al. 2008). Most of these reviews have mainly converged on implant survival and addressed to a lesser degree other outcome measures that determine the quality of survival. Furthermore, none of these reviews systematically analyzed the literature concerning the efficacy of single-tooth implants in the aesthetic zone neither did these reviews concentrate explicitly on the outcome of single implants with natural neighbouring teeth, applied to replace one missing tooth. However, it is worthwhile for patients and clinicians to know whether an immediate or conventional single-tooth implant represents a predictive, reliable and effectual therapy to re-establish function and aesthetics subsequent to the loss of a single anterior tooth. Therefore, the objective of this study was to evaluate, through a systematic review of the literature, the outcome of single-tooth replacements by dental implants in the aesthetic zone in cases in which the adjacent teeth are natural, thereby focussing on immediate, early and conventional implant treatment strategies.

Material and Methods Types of studies Longitudinal studies (Randomized controlled trials (RCTs), clinical trials, cohortstudies and case series) were considered for evaluation. Retrospective studies were excluded. Only case series that investigated at least five patients were contemplated 16

for inclusion. No time restrictions were implemented. Language was restricted to papers published in English, German, French, Spanish, Italian and Dutch.

Types of intervention - immediate implant placement: defined as implant placement immediately following extraction of a tooth; - early implant placement: defined as installation of the implant 4 to 8 weeks after extraction; - conventional implant placement: implant placement ≥ 8 weeks post-extraction; - immediate loading: application of a load by means of a restoration within 48 hours of implant placement; - early loading: application of a load by means of a restoration after 48 hours but less than 3 months after implant placement; - conventional loading: application of a load by means of a restoration ≥ 3 months after implant placement (Laney 2007). For studies to be eligible in this review, they had to evaluate endosseous root-form dental implants with a follow-up of at least 1 year after placement of the implant crown.

- - - -

- -

Types of outcome measures implant survival, defined as presence of the implant at time of follow-up examinations; changes in marginal peri-implant bone level assessed on radiographs; aesthetics evaluated by dental professionals; aspects of the peri-implant structures, i.e. level of marginal gingiva, papilla index (Jemt 1997), probing pocket depth, presence of plaque, bleeding on probing; patient satisfaction including aesthetics; biological and technical complications.

Search Strategy For this review, a thorough search of the literature was conducted in databases of MEDLINE (1950-2008 (via PUBMED) and EMBASE (1966 – 2008). The search 17

Systematic review

Type of participants Patients who were treated with an implant-retained single-tooth replacement in the aesthetic zone neighbored with natural teeth, could be included. The aesthetic zone was defined as the region in the maxilla or mandible, ranging from second premolar to second premolar (teeth 15-25 and teeth 35-45).

2

was supplemented with a systematic search in the ‘Cochrane Central Register of Controlled Trials’ (CENTRAL) (1800–2008). The search strategy used, was a combination of MeSH terms and free text words and is summarized in Table 1. The search was complemented by checking references of relevant review articles and eligible studies for additional useful publications. Titles and abstracts of the searches were scanned independently by two examiners. Full-text documents were obtained for all possibly relevant articles. Full text analysis was performed for second selection by two reviewers independently against the stated inclusion criteria. In case of disagreement, consensus was reached by discussion, if necessary in consultation with a third reviewer. Table 1. Search strategy.

Chapter

2

#1 Search “Dental Implants”[MeSH] OR “Dental Implantation”[MeSH] OR implant* #2 Search “single implant*” OR “single tooth” OR “single teeth” OR “single crown*” OR “single restoration*” #3 Search “aesthetic*” OR “esthetic*” OR “anterior*” OR “front*” OR “incisor*” #4 Search #1 AND #2 AND #3 Run data search: June 2008.

Quality assessment Methodological quality was assessed using specific study-design related forms designed by the Dutch Cochrane Collaboration. As there was no checklist available for the assessment of the quality of case series, a quality-assessment tool was specifically developed for this review, adapted from the quality form used for clinical trials (Table 2). Two observers independently generated a score for the included articles, expressed in the number of plusses given. It was decided that studies scoring 5 or more plusses were considered to be methodological ‘acceptable’. Data extraction and synthesis For each trial the following data were extracted by two review authors independently and recorded in a data sheet: - number of patients, implants placed, drop-outs and follow-up time. For all included longitudinal studies of more than one year, follow-up time was calculated as person-years; - details of type of intervention; - details of the outcomes stated, including method of assessment. Agreement was reached by a consensus discussion and if necessary a third reviewer was consulted. If feasible, a meta-analysis was carried out if the outcome measures could be meaningfully combined. 18

Table 2. Quality assessment of case series. Item

+

-

?

1. Are the characteristics of the study group clearly described? 2. Is there a high risk of selection bias? Are the inclusion and exclusion criteria clearly described?

4. Are the outcomes clearly described? Are adequate methods used to assess the outcome? 5. Is blinding used to assess the outcome? 6. Is there a sufficient follow-up? 7. Can selective loss-to follow-up sufficiently be excluded? 8. Are the most important confounders or prognostic factors identified and are these taken into consideration with respect to the study design and analysis? Five or more plusses = methodologically acceptable.

Statistical analysis With respect to the quality assessment, agreement between both reviewers was calculated using Cohen’s kappa (κ) statistics. For the meta-analysis the statistical software package “Meta-analysis” was used (Comprehensive Meta-analysis Version 2.2, Biostat, Englewood NJ (2005), www.meta-analysis.com). For the calculation of the overall effects for the included studies, weighted rates together with random effects models were used. Stratification procedures were applied for follow-up time and type of intervention. Within each stratum, heterogeneity between included studies was checked by human eyeball criteria.

Results Description of studies The MEDLINE search provided 610 hits, the EMBASE search 23 hits and the CENTRAL search 27 hits. After scanning of titles and abstracts, 86 articles were selected and screened as full text articles. Reference-checking of relevant reviews and included studies revealed one additional article (Hall et al. 2006). However, this report showed to be a shortened version of a later publication (Hall et al. 2007) and did not contain any new information. A number of 41 studies did not satisfy 19

Systematic review

3. Is the intervention clearly described? Are all patients treated according to the same intervention?

2

the inclusion criteria because data of single-tooth implants in anterior and posterior zones was not presented separately or adjacent implants were also included, making it not possible to extract proper data. Furthermore, 14 studies were excluded due to improper study design (not longitudinal or not prospective) and 5 studies because of a follow-up < 1 year. A total of 26 articles fulfilled the inclusion and exclusion criteria and were assessed methodologically. Of these 26 studies, 7 studies were excluded. Reasons for exclusion are depicted in Table 3. Table 3. Studies excluded after quality assessment and reasons for exclusion. Study

Study design

Reasons for exclusion

Henriksson 2004

Clinical trial

Heterogeneity in clinical procedure (different implants, different load-free periods), in/exclusion criteria unclear, no blinding used, prognostic factors/ confounders not considered.

Lorenzoni 2003

Case series

Patients not treated according to same intervention (immediate and conventional placement included), in/ exclusion criteria unclear, no blinding used, prognostic factors/confounders not considered.

Ferrara 2006

Case series

High risk of selection bias (implants with insufficient primary stability were excluded; method to assess stability not clear), outcomes not clearly described, methods used to assess the outcome unclear, no blinding used, prognostic factors/confounders not considered.

Grunder 2000

Case series

Patients characteristics unclear, in/exclusion criteria unclear, no blinding used, prognostic factors/confounders not considered.

Locante 2004

Case series

Patients not treated according to same intervention (immediate and conventional placement included), high risk of selection bias (implants with insufficient primary stability were excluded; method to assess stability not clear), in/exclusion criteria unclear, no adequate methods used to assess the outcome, no blinding used, follow-up routine unclear, prognostic factors/confounders not considered.

Groisman 2003

Case series

Patient characteristics unclear, high risk of selection bias (only favorable cases selected), method of assessment not clear, no blinding used, prognostic factors/ confounders not considered, follow-up routine unclear.

Barone 2006

Case series

Patient characteristics not clear, high risk of selection bias (only favorable cases selected), no blinding used, prognostic factors/confounders not considered.

Chapter

2

20

Figure 1. Algorithm of study selection procedure. Identified articles - MEDLINE search: n = 610 - EMASE search: n = 23 - CENTRAL search: n = 27

Systematic review

The κ-value for inter-assessor agreement on the methodological quality was 0.89. Disagreements were generally caused by slight differences in interpretation and were easily resolved in a consensus meeting. Finally, 19 publications remained for data extraction. Figure 1 outlines the algorithm of the study selection procedure. Of the included studies, 5 were RCTs, 2 were clinical trials and 12 were case series. Six publications presented outcomes of the same patient population, but differed in follow-up (Palmer et al. 1997, 2000, Cooper et al. 2001, 2007, Jemt & Lekholm 2003, 2005) and results of one study group were reported in two different publications addressing different topics (Schropp et al. 2005a, 2005b).

2 Excluded articles • Improper study design • Non-topic related • No abstract available • Follow-up < 1 year

Included for full text analysis n = 86 Excluded articles • Required data not presented • Improper study design • Follow-up < 1 year Included for methodological appraisal n = 26

Excluded articles Grunder 2000; Groisman et al., 2003; Lorenzoni et al., 2003; Locante et al., 2004; Henriksson et al., 2004; Ferrara et al. , 2006; Barone et al., 2006

Included for data analysis n = 19

Most of the studies only evaluated maxillary implants, but three studies did also include implants placed in the mandible (38 implants in total) (Schropp et al. 2005a, Schropp et al. 2005b, Romeo et al. 2008). Furthermore, implants were installed mostly in completely healed extraction sockets or early after extraction (10 days to 4 weeks) and subsequently were restored according to immediate, early (1 to 3 weeks after implant placement) or conventional loading protocols. Restorations that were seated immediate or early after implant placement, were 21

Immediate placement and immediate loading

Immediate placement and immediate loading

Immediate placement vs conventional placement

Early placement vs conventional placement

Early placement vs conventional placement

Early placement vs conventional placement

Immediate placement

De Rouck 2008

Lindeboom 2006

Schropp 2005 (a)

Schropp 2005 (b)

Gotfredsen 2004

Romeo 2008

Intervention

Kan 2003

Study

CS

CT

RCT

RCT

RCT

CS

CS

T C

T C

T C

T C

Design

48/48

10/10 10/10

23/23 23/23

23/23 22/22

25/25 25/25

30/30

35/35

No. of patients/ implants

ITI

Astra Tech

3i

3i

Frialit-2

Replace Select

Replace Select

Implant system

Caries/endodontic with root or crown fracture (NR)

Root fracture (15), agenesis (3), trauma (2)

Root fracture (NR), endodontic failure (NR), periodontitis (NR), advanced caries lesions (NR)

Root fracture (NR), endodontic failure (NR), periodontitis (NR), advanced caries lesions (NR)

NR

Fracture (10), caries/ endodontic (9), periodontal (7), root resorption (4)

Fracture (15), endodontic failure (12), root resorption (8)

Reason(s) for tooth loss (no.)

1

5

2

2

1

1

1

Followup period (yrs)

0

0 0

3 2

NR

2 0

1

0

No. of implant dropouts**

100

100 100

91 96

NR

92 100

97

100

Survival rate (%)

Table 4. Study characteristics and outcomes of included studies, arranged according to type of intervention and study design.

22

NR

- 0.34 ± 0.57 ¶ - 0.26 ± 0.38 ¶

- 0.8 ± NR ‡ - 0.7 ± NR ‡

NR

- 0.51 ± 0.12* # - 0.52 ± 0.15* #

- 0.88 ± 0.52* #

- 0.24 ± 0.35* #

Change in marginal bone level ± SD (mm)

Intervention

Immediate loading vs conventional loading

Immediate loading vs conventional loading

Early loading

Early loading

Early loading

Conventional

Conventional

Conventional

Conventional

Conventional

Conventional

Conventional

Study

Hall 2007

Ericsson 2000

Cooper 2001

Cooper 2007

Andersen 2002

Meijndert 2007

Jemt 2003

Jemt 2005

Zarone 2006

Palmer 1997

Palmer 2000

Cardaropoli 2006

Table 4. (Continued)

CS

CS

CS

CS

CS

CS

RCT

CS

CS

CS

CT

RCT

T C

T C

Design

16/16

15/15

15/15

30/34

10/10

10/10

93/93

8/8

48/54

48/54

14/14 8/8

14/14 14/14

No. of patients/ implants

Brånemark

Astra Tech

Astra Tech

ITI

Brånemark

Brånemark

ITI

ITI

Astra Tech

Astra Tech

Brånemark

Southern Implants

Implant system

NR

NR

NR

Agenesis (30)

Trauma (10)

Trauma (10)

NR

NR

NR

NR

NR

NR

Reason(s) for tooth loss (no.)

1

5

2

2 - 3.2

6

3

1

5

3

1

1.5

1

Followup period (yrs)

5

1

1

1

2

1

2

0

11

3

2 0

1 2

No. of implant dropouts**

100

100

100

100

100

100

97.8

100

94.4

94.4

85.7 100

93 100

Survival rate (%)

- 1.6 ± 0.57* #

+ 0.12 ± 0.49* ¶

+ 0.01 ± 0.50* ¶

- 1.2 ± 0.61 §

- 0.3 ± 0.24 ¶

- 0.3 ± 0.36 ¶

NR

+ 0.53 ± NR§

-0.42 ± 0.59§

- 0.4 ± NR §

- 0.14 ± 0.36 ¶ - 0.07 ± 0.79 ¶

- 0.63 ± 1.00 ¶ - 0.78 ± 1.01 ¶

Change in marginal bone level ± SD (mm)

*Standard deviation calculated. ** Defined as implants that did not survive and implants lost to follow-up. # From implant placement. ‡ From healing abutment placement. §From temporary crown placement. ¶From definitive crown placement. Abbreviations: NR= not reported, RCT=randomized clinical trial, CT= clinical trial, CS = case series, T = test group, C = control group.

23

NR

T C

T

Lindeboom 2006

Schropp 2005 (a)

C

T

Ericsson 2000

NR

NR

T C

Hall 2007

5.9 (2.9 - 9.5) 8.4 (6.1 - 9.7)

NR

T C

Gotfredsen 2004

NR

Romeo 2008

T C

Schropp 2005 (b)

C

NR

De Rouck 2008

NR

9.9 (9 - 10)

NR

Kan 2003

All patients satisfied All patients satisfied

NR

NR

9.6 (7.1 - 10)† 9.1 (5.1 - 10)†

NR

NR

NR

9.3 (8.2-10)

Patient satisfaction (range)

Aesthetics (range)

Study

NR

resp. 18%,51%,31% score 1,2,3 (pooled data) No sign. diffs.

NR

-0.67 ± 0.49 § -0.33 ± 0.78 §

NR

- 0.3 ± 0.5 ¶ + 0.3 ± 0.6 ¶

NR

67% score 3 *

NR

50% proper level

83% proper level

61% proper level 84% proper level

-0.53 ± 0.76 ‡

-0.55 ± 0.53 ‡

Level of marginal gingiva ± SD (mm)

NR

resp. 8%,35%,57% score 0,1,2 * resp. 3%,34%,63% score 0,1,2 *

22 % score 2, 78% score 3 28% score 2, 72% score 3

NR

NR

Papilla index

25%

25%

No sign. diffs.

No sign. diffs. NR

NR

21% (pooled data)

NR

NR

NR

NR

4.2 ± 1.4 # 4.1 ± 1.1 #

NR

NR

17%

3.46 ± 0.69 NR

26%

Presence of plaque

NR

Probing depth ± SD (mm)

Table 5. Outcomes of included studies, arranged according to type of intervention and study design.

24

25%

17%

No sign. diffs.

NR

38% (pooled data)

NR

NR

NR

41%

NR

Bleeding on probing

1 temporary crown loosened twice

1 temporary crown fractured

No complications

2 soft tissue dehiscences, 1 fistula, 2 abutments loosened

1 fistula, exposure of metal margins in 4 cases

NR

NR

1 crown loosened

4 fistula, 2 temporary abutments loosened

Complications

NR

NR

66% acceptable

NR

NR

Meijndert 2007

Jemt 2005

Jemt 2003

8.5 ( 6-10)

NR

Andersen 2002

NR

NR

NR

Palmer 1997

Palmer 2000

Cardaropoli 2006

NR

NR

NR

NR

resp. 14%,68%,18% score 1,2,3

NR

NR

resp. 6%,12%,82% score 1,2,3

NR

50% score 2, 50% score 3

NR

NR

NR

NR

-0.6 ± 0.7 ¶

No recession

No recession

-0.6 ± NR §

- 0.1 ± NR ¶

NR

NR

NR

+ 0.51 ± 1.42 §

+ 0.34 ± 0.94 §

NR

NR

2.4 ± 0.8

NR

NR

NR

18%

NR

NR 2.6 ± 0.2 #

NR

NR

NR

NR

NR

NR

NR

NR

0.5% of sites examined

NR

9%

Rare

No bleeding

No bleeding

NR

NR

NR

NR

NR

NR

NR

See above. No new complications reported

No soft tissue complications. 1 crown loosened, 1 porcelain fracture

No implant-related complications.

No complications

No complications

NR

1 fistula, 3 crowns loosened

See above. No new complications reported

1 adjacent tooth migrated, 1 peri-implant mucositis, 1 implant discomfort, 3 crowns loosened; 4 fractured

placement. ¶From definitive crown placement. Abbreviations: T=test group, C = control group, NR = not reported.

*Modification of Papilla Index. † Mean VAS-scores for aesthetic appearance and general function. #Standard deviation calculated. ‡ From implant placement. § From temporary crown

3% not satisfactory

Zarone 2006

NR

NR

NR

Cooper 2007

NR

NR

Cooper 2001

Table 5. (Continued)

25

all kept out of direct occlusal contact. Two studies reported on immediately restored implants placed directly after tooth extraction. All clinical trials except one compared the outcome of immediate or early implant placement and immediate or early implant loading with conventional approaches. This RCT focused on different bone augmentation procedures and all implants were placed and restored conventionally according to the same protocol (Meijndert et al. 2007). Characteristics of the included studies are presented in Table 4 and are arranged according to type of intervention and study design. Due to methodological diversity of the ‘acceptable’ studies, only data on implant survival and to a limited degree marginal bone resorption could be meaningfully combined in a meta- analysis. Therefore, the outcomes are mainly presented as a descriptive review in the subsequent sections and are depicted in Table 4 and 5.

Chapter

2

Implant survival The implant survival rate was defined as the percentage of implants that was still present at follow-up. All implants that were lost, failed within the first six months after placement. In some studies implant mobility was detected at second stage surgery (seven implants) (Schropp et al. 2005b, Lindeboom et al. 2006, Meijndert et al. 2007) or occurred following placement of the provisional restoration (one implant) (Cooper et al. 2001), whereas other implants were already in function when they appeared not to be osseointegrated (six implants) (Ericsson et al. 2000, Cooper et al. 2001, Hall et al. 2006, De Rouck et al. 2008). Altogether, a total number of 509 single-tooth implants was originally installed in 499 patients of which 13 patients and 13 implants were lost to follow-up and no information on survival was available regarding these implants. A total of 14 implants did not survive. Since it is generally known that implant loss is most often observed early after implant installation and/or implant restoration, event rates and survival rates were calculated in a stratified manner. To that end, results are presented for implants that were followed up to one year after implant restoration (including implants that were lost before restoration and consequently were not yet in function) and implants with an observation period of more than one year after restoration (with a correction for implants that were lost within the first year after restoration). Results of the weighted meta-analysis (for study size) of implant loss within one year, expressed as event rates, are shown in Figure 2. The overall event rate was calculated as 0.045 (95% conficende interval (CI): 0.029 – 0.070) and can be expressed as a survival rate of 95.5% (95% CI: 93.0 – 97.1). The weighted meta-analysis (for person-years and study-size) regarding loss of implants that are more than one year in function, showed an event rate of 0.007 (95% CI: 0.003 – 0.019).

26

Figure 2. Meta-analysis of implant loss within one year after restoration. "OEFSTFO $BSEBSPQPMJ $PPQFS

Systematic review

%F3PVDL &SJDTTPO (PUGSFETFO )BMM +FNU 

2

,BO -JOEFCPPN .FJKOEFSU 1BMNFS 

3PNFP 4DISPQQ C

;BSPOF



 &WFOUSBUF



 $*

Globally four different treatment strategies could be identified. In this matter, survival outcomes of immediate and early placed implants that were restored conventionally were combined as well as implants that were installed conventionally but were restored immediately or early. Results of the weighted (for studysize) stratified meta-analysis are presented in Table 6, revealing no differences in survival rate after one-year follow-up. Focussing on the studies individually, no statistically significant differences in implant survival were found in clinical trials comparing immediate or early implant procedures with conventional ones. 27

Table 6. Stratified meta-analysis of implant survival after one-year. Intervention

Immediate placement and immediate loading Immediate/early placement, conventional loading

Chapter

2

Conventional placement, immediate/early loading Conventional placement, conventional loading

No. of patients/ implants

No. of studies included

No. of implants lost to follow-up*

No. of implants that not survived

Calculated survival rate (%) [95% CI]

65/65

2

1

1

97.5 [88.3 99.5]

106/106

4

1

4

93.6 [85.4 97.3]

84/90

4

0

6

92.4 [84.4 96.4]

244/248

11

11

3

96.8 [85.7 97.2]

* These implants were not included in the analysis. Abbreviations: CI=convidence interval.

Marginal bone level changes All articles except three reported on changes in marginal peri-implant bone levels determined radiographically. Most of the studies used intra-oral radiographs obtained according to a standardized paralleling technique, although it was questionable whether Cooper et al. (2001), Jemt and Lekholm (2003, 2005), Palmer et al. (1997, 2000) and Gotfredsen (2004) used standardized radiography for their measurements. There was variety in the peri-implant bone level evaluation over time since studies used different starting points for their analysis. In the various studies, the first radiographic examinations had been performed just after implant placement, after healing abutment connection, at provisional crown placement or at definitive crown placement. Because of this heterogeneity, it was not possible to perform an analysis from which conclusions could be drawn concerning differences in marginal bone changes between the several treatment strategies. However, some insight could be gained into crestal bone changes occurring from definitive crown placement to one year thereafter in patients treated conventionally. The five studies included for this weighted (for study-size) meta-analysis (viz. Palmer et al. 1997, Ericsson et al. 2000, Gotfredsen 2004, Jemt & Lekholm 28

Figure 3. Meta-analysis of marginal bone level changes 1 year after installation of the definitive crown. &SJDTTPO 1BMNFS 

(PUGSFETFO +FNU 

$BSEBSPQPMJ

 

 

  *

#POFMPTT NN

 

 

* * #POFJODSFBTF NN

.FBOCPOFMPTTNN $*¬  

Aesthetics Albeit all implants reviewed were inserted in the aesthetic zone, only three studies included the aesthetic outcome in their analysis. Zarone et al. (2006) considered one implant not being satisfactory because of exposure of the titanium neck. It was, however, unclear how the aesthetics were measured. At the threeyear control visit Gotfredsen (2004) asked an independent dentist to evaluate the aesthetic appearance of the implant crowns using a visual analog scale (VAS) ranging from ‘very unsatisfied’ (score 0) to ‘very satisfied’ (score 10). In the study by Meijndert et al. (2007), a prosthodontist rated the aesthetics on colour photographs using an objective rating index. It appeared that 34% of the cases were judged as poor aesthetics. 29

Systematic review

2005, Cardaropoli et al. 2006) (in total 52 implants) revealed a mean marginal bone loss of 0.20 mm (95% CI: 0.034 – 0.36) during the first year after installation of the definitive crown (see Figure 3). Data from radiographic examinations were mostly presented as mean values and consequently no frequency distributions were given. Cooper et al. (2001) considered the incidence of marginal bone loss of 48 implants one year after insertion. The latter authors found that after one year eight implants showed a cortical bone loss of 1.0 to 2.0 mm and three implants more than 2.0 mm. Finally, the bone level changes detected in the experimental and conventional study groups of the included clinical trials were not significantly different.

2

Chapter

2

Peri-implant structures To evaluate the quantity of the interproximal gingival papillae, some studies made use of the papilla index according to Jemt (1997) or a slight modification of this classification (Schropp et al. 2005a, Romeo et al. 2008). It revealed that in these studies an increase of tissue volume in the embrasures could be observed during follow-up. For instance, Jemt and Lekholm (2003) found a mean papilla index of 1.1 at crown placement (score 1 and 2 denote, respectively, less than half of the height and at least half of the height of the proximal area filled by soft tissue) while at two-year follow-up a mean score of 2.4 was found (score 3: complete closure of proximal space with soft tissue). The majority of the papillae analyzed were associated with papilla index scores of 2 or 3 after follow-up, but no significant differences were observed between the different test and control groups. With respect to the marginal peri-implant mucosal level, Schropp et al. (2005a) reported that the clinical crown height was acceptable in significantly more cases in the early placement group than in the conventional group at follow-up; of the latter almost two-thirds of the crowns were assessed to be too short. The same difference was found by Gotfredsen (2004), although not reported as significant. Lindeboom et al. (2006) observed that gingival recession was more prominent in the immediately-placed implant group, but the sample size was too small to demonstrate a significant difference. Hall et al. (2006) found no statistical significant differences between immediately or conventionally restored implants. Jemt and Lekholm (2005) reported that implant crowns were on average 0.7 mm longer than the contralateral natural crowns after five-year follow-up. The same value was recorded by Gotfredsen (2004) after five-year and he found that 17 of the 20 implant crowns were too long. The studies by De Rouck et al. (2008) and Kan et al. (2003) measured the levels of the midfacial gingival level before tooth removal and after immediate implant placement and restoration. After one-year follow-up, both studies reported a significant soft tissue loss of respectively 0.53 mm and 0.55 mm at the midfacial aspect. Only a few studies recorded peri-implant probing pocket depths. Schropp et al. (2005b) observed a mean reduction in probing depth of 0.5 mm during the twoyear observation period to a mean probing depth of 4.2 mm. The mean probing depths presented by other studies were clearly lower. Studies that assessed the presence of plaque on the surfaces of the implant restoration showed high variance in outcome from 0.5 % to 61% of sites examined. According to bleeding on probing, the same phenomenon could be observed. Patient satisfaction Four studies assessed patient satisfaction regarding the final aesthetics and one study (Gotfredsen, 2004) also evaluated the general functioning of the implant 30

Complications The complications described in the various articles were subdivided in biological and technical ones. With respect to biological complications, the authors reported on fistula formations, peri-implant mucositis and soft tissue dehiscences. All fistula subsided after placement of the definitive restoration (Andersen et al. 2002, Kan et al. 2003a) or after non-invasive therapy (Gotfredsen 2004, Schropp et al. 2005b). In the study by Schropp et al. (2005b) exposure of metal margins was found in four patients. In three cases, the margin became exposed during the observation period because of soft tissue recession. In one case, the metal margin of the crown was present just after crown placement, but became covered with peri-implant mucosa during function. Technical complications that were notified were loosening of (temporary) abutments and loosening or fractures of (temporary) crowns. In most of the cases, abutments could be retightened and crowns could be recemented easily. In the study by Andersen et al. (2002) three out of eight definitive crowns loosened after approximately one year. In two of these cases, this was a direct result of a new trauma. It could be noticed that not all studies provided data regarding complications other than implant loss and crestal bone resorption. Concerning the comparative studies, only Gotfredsen (2004) found more complications in the experimental ‘early placement’ study group. However, these implants were restored with standard abutments, while preparable abutments were used for the conventional implants and the author believed that the technical complications were probably more related to this difference.

Discussion This systematic review assessed the outcome of single-tooth implants in terms of implant survival, marginal bone level changes, aesthetics, soft tissue aspects, patient satisfaction and complications. Aside from the traditional approaches of implant installation and restoration, more progressive treatment strategies of immediate or early implant placement and immediate or early loading were considered for evaluation. Unfortunately, we could not draw firm conclusions regarding the most preferable treatment strategy, owing to the lack of controlled clinical trials. 31

Systematic review

restoration. High satisfaction scores were reported. Three studies (Gotfredsen 2004, Meijndert et al. 2007, De Rouck et al. 2008) made use of a VAS (range 0-10), one study (Kan et al. 2003a) of a scale ranging from very unsatisfied (score 0) to very satisfied (score 10), and in one study (Ericsson et al. 2000) patients were asked about their satisfaction with the aesthetic outcome.

2

Chapter

2

Notwithstanding these limitations, promising results were reported for immediate, early and conventional single-tooth implant procedures in the aesthetic zone. The implant survival meta-analysis on implants in the aesthetic zone up to one year after implant restoration, revealed an overall survival rate of 95.5% (95% CI: [93.0 – 97.1]) irrespective of the type of intervention. It should be stated that, with respect to the loss of implants that are more than one year in function, a very low event rate was calculated (0.007 (95% CI: [0.003 – 0.019]). In general, late implant losses are attributed to fracture of the implant, overload and peri-implantitis in particular (Quirynen et al. 2007). In reference to the last, the strict in- and exclusion criteria implemented in most of the included trials such as good oral hygiene, uncontrolled periodontal disease or smoking concomitant with close follow-up routines, could limit the development of peri-implantitis and thereupon late implant failure. Of course, in this view, the relative short follow-up periods of the included studies have to be taken into account. The high implant survival rate (95.5% after one year) reported in the present review, are in line with other reviews reporting on survival rates of single-tooth implants (Creugers et al. 2000, Berglundh et al. 2002, Jung et al. 2008). However, the last two reviews only included studies with follow-up periods of at least five year, justifying that a comparison with our calculated survival rate should only be made with caution. Furthermore, these reviews aggregated implant survival of diverging indications, including anterior and posterior, and maxillary and mandibular single-tooth replacements. Particularly the posterior maxilla constitutes an area of challenge due to the presence of the maxillary sinus and the low bone density frequently found here. Long-term implant survival studies have even indicated that the posterior maxilla presents the lowest survival rate (Graziani et al. 2004). Apparently, this does not count for the survival of maxillary anterior single-tooth implants. The more progressive protocols, where implants are immediately installed in fresh extraction sockets or immediately loaded, scored comparable survival percentages as the conventional protocol of installation and restoration. Although no differences were noted neither in the stratified meta-analysis nor in the included clinical trials, these results should only be conceived as a tendency, since these were based on only a few (randomized) controlled trials and a low number of patients. Two studies were included investigating the most escalating approach, viz. immediately loading of immediately placed implants. All implants integrated successfully. In these case series only patients were enrolled satisfying strict inclusion and exclusion criteria like presence of adequate bone volume without the necessity of bone grafting, an intact labial bony plate after tooth extraction, complementary soft tissue dimensions and ability to achieve good implant stability. It implies that 32

33

Systematic review

this modality should be implemented with caution and should be preceded by careful patient selection and treatment planning. The same hold true for immediate or early implant loading of implants placed in healed sites. Studies investigating these approaches, pointed out the importance of good initial implant stability before loading and all provisional crowns were cleared from occlusion. It was only possible to combine the outcome measures of implant survival and to a limited degree crestal bone changes in a stratified meta-analysis. Reasons were that different outcomes or time points were used or some variables were not taken into consideration. With reference to the clinical trials, for only one outcome measure a significant difference was observed. Schropp et al. (2005a) reported that the level of the marginal peri-implant mucosa was acceptable in significantly more cases where implants were installed in early healed extraction sites compared to conventionally healed sites; of the latter almost two-thirds of the crowns were assessed to be too short. All other clinical trials failed to show any significant differences. Remarkably, only three studies assessed the aesthetic outcome of which only one study made use of an objective aesthetic index. The lack of documentation of well-defined aesthetic parameters in anterior implant research was demonstrated earlier by Belser et al. (2004). Nowadays, two instruments are available that aim to objectify the aesthetic outcome of single-tooth implant crowns, namely the Implant Crown Aesthetic Index to measure the aesthetics of crown and mucosa (Meijer et al. 2005) and the Pink Esthetic Score (Furhauser et al. 2005) which focuses on soft tissue solely. It was concluded that both indexes showed reproduciblity, based on calculations of intra- and interobserver agreement. However, the validity of these indexes was not investigated and although they show good face validity, the construct validity in particular needs further research. Because these indexes were developed fairly recently, this could be a prominent reason that only Meijndert et al. (2007) used the Implant Crown Aesthetic Index, apart from the fact that the latter authors introduced this index (Meijer et al., 2005). Meijndert et al. (2007) reported that in 34% of the cases, the aesthetics were not acceptable, which is a rather high percentage. It must be noted, however, that in all cases a local bone augmentation procedure was needed prior to implantation because of severe bone deficiencies. This implies again the significance of the aesthetic appearance before implant treatment and that the final aesthetics might be strongly related to that appearance. To illustrate, when the starting point is favorable, favorable aesthetics could be expected from an implant based singletooth replacement, both from the patient’s and professional’s perspectives, while an unfavorable starting point might lead to satisfactory results from the patient’s perspective while the professionals objective judgement might be unfavorable. This incongruity might lead easily to bias in aesthetic implant research.

2

Chapter

2

It is widely accepted that randomized controlled trials (RCTs) provide ‘gold standard’ evidence of the effectiveness of therapies. However, there is scarcity of existing RCTs in implant research, probably caused by medical-ethical reasons, costs or workload involved in this type of research. Nevertheless, relevant information is not exclusively provided by RCTs for matters of longevity. Cohortstudies, case series and clinical trials could also provide valuable longitudinal information. Therefore, these types of studies were considered for evaluation too. It appeared that seven eligible comparative trials could be included, of which four studies examined immediate or early implant placement, two studies immediate implant loading and one study focussed on different bone augmentation procedures prior to implantation. Sample sizes were relatively small and presumably underpowered to demonstrate significant differences between experimental and conventional single-tooth implant approaches. Furthermore, not all clinical trials randomly allocated patients to the study groups and for three trials it was unclear if the outcome assessors were blinded. Probably, some trials were confounded by the type of prosthetic restoration as Schropp et al. (2005b) and Gotfredsen (2004) made use of different types of abutments and Ericsson et al. (2000) reported that ceramic or metal-ceramic crowns were utilized. Probably, these variances could have their influence on parameters like the aesthetic outcome and patient satisfaction. The remaining studies included for this review, could be classified as case series and as a consequence were of a lower level of evidence. Although these studies were well documented and methodological acceptable within their framework, results of these studies should be interpreted with caution. Selection and measurement bias will always be present in case series, together with a potential risk of incorporation bias, favoring the final outcome of the intervention. Moreover, for most of the case series it was not reported or unclear whether consecutive recruitment was used. Non-consecutive enrolment may lead to selection of patients with more favorable pre-operative conditions. Besides the low number of RCTs and small study groups, one of the major drawbacks of the reviewed literature was the lack of sufficient follow-up. Eight of the included studies followed their patients for only one year. It is noteworthy that, on the other hand, only a small number of patients were lost to follow-up. In our opinion, the follow-up periods were too short to lead to definitive conclusions as to whether a single-tooth implant in the aesthetic zone is a reliable therapy over the long term. However, since there is sufficient evidence in present implantology that implant losses predominately occur within the first months after placement, the favorable short term survival rates of single implant replacements in the anterior zone might justify the expectations of a successful long-term survival. For other parameters including aspects of the peri-implant mucosa, aes34

35

Systematic review

thetic outcome and patient satisfaction, more long-term research is needed, such as cohort-studies. In conclusion, evidence from the included literature suggest that single-tooth implants in the aesthetic zone with natural adjacent teeth will lead to (short-term) successful treatment outcomes regarding implant survival, marginal bone level changes and incidence of biological and technical complications. However, with reference to quality of study design, number of patients included and follow-up duration, the included studies showed inadequacies. Moreover, other parameters of utmost importance as the aesthetic outcome, soft tissue aspects, and patient satisfaction were clearly underexposed. The question whether immediate and early implant placement or immediate and early implant loading will result in comparable – or even better – treatment outcomes than conventional implant protocols of installation and restoration, remains inconclusive. Thus, more well-designed (randomized) comparative trials are needed investigating objective aesthetic and satisfaction parameters in particular, to verify these treatment strategies.

2

References

(2000) Immediate functional loading of Branemark single tooth implants. An 18 months’ clinical pilot follow-up study. Clinical Oral Implants Research 11, 26-33.

Al-Harbi, S.A. & Edgin, W.A. (2007) Preservation of soft tissue contours with immediate screw-retained provisional implant crown. Journal of Prosthetic Dentistry 98, 329-332. Andersen, E., Haanaes, H.R. & Knutsen, B.M. (2002) Immediate loading of single-tooth ITI implants in the anterior maxilla: a prospective 5-year pilot study. Clinical Oral Implants Research 13, 281-287. Barone, A., Rispoli, L., Vozza, I., Quaranta, A. & Covani, U. (2006) Immediate Restoration of Single Implants Placed Immediately After Tooth Extraction. Journal of Periodontology 77, 1914-1920.

Chapter

2

Belser, U.C., Schmid, B., Higginbottom, F. & Buser, D. (2004) Outcome analysis of implant restorations located in the anterior maxilla: a review of the recent literature. International Journal of Oral and Maxillofacial Implants 19 Suppl, 30-42. Berglundh, T., Persson, L. & Klinge, B. (2002) A systematic review of the incidence of biological and technical complications in implant dentistry reported in prospective longitudinal studies of at least 5 years. Journal of Clinical Periodontology 29 Suppl 3, 197-212. Canullo, L. (2007) Clinical outcome study of customized zirconia abutments for single-implant restorations. International Journal of Prosthodontics 20, 489-493. Cardaropoli, G., Lekholm, U. & Wennstrom, J.L. (2006) Tissue alterations at implant-supported single-tooth replacements: a 1-year prospective clinical study. Clinical Oral Implants Research 17, 165-171. Cooper, L., Felton, D.A., Kugelberg, C.F., Ellner, S., Chaffee, N., Molina, A.L., Moriarty, J.D., Paquette, D. & Palmqvist, U. (2001) A multicenter 12-month evaluation of single-tooth implants restored 3 weeks after 1-stage surgery. International Journal of Oral and Maxillofacial Implants 16, 182-192. Cooper, L.F., Ellner, S., Moriarty, J., Felton, D.A., Paquette, D., Molina, A., Chaffee, N., Asplund, P., Smith, R. & Hostner, C. (2007) Three-year evaluation of single-tooth implants restored 3 weeks after 1-stage surgery. International Journal of Oral and Maxillofacial Implants 22, 791-800. Creugers, N.H., Kreulen, C.M., Snoek, P.A. & De Kanter, R.J. (2000) A systematic review of single-tooth restorations supported by implants. Journal of Dentistry 28, 209-217. De Rouck, T., Collys, K., Cosyn, J. (2008) Immediate singletooth implants in the anterior maxilla: a 1-year case cohort study on hard and soft tissue response. Journal of Clinical Periodontology 35, 649-657. Ericsson, I., Nilson, H., Lindh, T., Nilner, K. & Randow, K.

36

Esposito, M., Grusovin, M.G., Maghaireh, H., Coulthard, P. & Worthington, H.V. (2007) Interventions for replacing missing teeth: management of soft tissues for dental implants. Cochrane Database of Systematic Reviews CD006697. Esposito, M.A., Koukoulopoulou, A., Coulthard, P. & Worthington, H.V. (2006) Interventions for replacing missing teeth: dental implants in fresh extraction sockets (immediate, immediate-delayed and delayed implants). Cochran Database of Systematic Reviews CD005968. Ferrara, A., Galli, C., Mauro, G. & Macaluso, G.M. (2006) Immediate provisional restoration of postextraction implants for maxillary single-tooth replacement. International Journal of Periodontics and Restorative Dentistry 26, 371-377. Furhauser, R., Florescu, D., Benesch, T., Haas, R., Mailath, G. & Watzek, G. (2005) Evaluation of soft tissue around single-tooth implant crowns: the pink esthetic score. Clinical Oral Implants Research 16, 639-644. Gapski, R., Wang, H.L., Mascarenhas, P. & Lang, N.P. (2003) Critical review of immediate implant loading. Clinical Oral Implants Research 14, 515-527. Glauser, R., Zembic, A. & Hammerle, C.H. (2006) A systematic review of marginal soft tissue at implants subjected to immediate loading or immediate restoration. Clinical Oral Implants Research 17 Suppl 2, 82-92. Gotfredsen, K. (2004) A 5-year prospective study of singletooth replacements supported by the Astra Tech implant: a pilot study. Clinical Implant Dentistry and Related Research 6, 1-8. Graziani, F., Donos, N., Needleman, I., Gabriele, M. & Tonetti, M. (2004) Comparison of implant survival following sinus floor augmentation procedures with implants placed in pristine posterior maxillary bone: a systematic review. Clinical Oral Implants Research 15, 677-682. Groisman, M., Frossard, W.M., Ferreira, H.M., Menezes Filho, L.M. & Touati, B. (2003) Single-tooth implants in the maxillary incisor region with immediate provisionalization: 2-year prospective study. Practical Procedures Aesthetic Dentistry Journal 15, 115-22, 124. Grunder, U. (2000) Stability of the mucosal topography around single-tooth implants and adjacent teeth: 1-year results. International Journal of Periodontics and Restorative Dentistry 20, 11-17. Hall, J.A., Payne, A.G., Purton, D.G. & Torr, B. (2006) A randomized controlled clinical trial of conventional and immediately loaded tapered implants with screw-retained crowns. International Journal of Prosthodontics 19, 17-19.

Harvey, B.V. (2007) Optimizing the esthetic potential of implant restorations through the use of immediate implants with immediate provisionals. Journal of Periodontology 78, 770-776. Henriksson, K. & Jemt, T. (2004) Measurements of soft tissue volume in association with single-implant restorations: a 1-year comparative study after abutment connection surgery. Clinical Implant Dentistry and Related Research 6, 181-189. Irinakis, T. & Tabesh, M. (2007) Preserving the socket dimensions with bone grafting in single sites: an esthetic surgical approach when planning delayed implant placement. Journal of Oral Implantology 33, 156-163. Jemt, T. (1997) Regeneration of gingival papillae after single-implant treatment. International Journal of Periodontics and Restorative Dentistry 17, 327-333 Jemt, T. (1999) Restoring the gingival contour by means of provisional resin crowns after single-implant treatment. International Journal of Periodontics and Restorative Dentistry 19, 20-29. Jemt, T. & Lekholm, U. (2003) Measurements of buccal tissue volumes at single-implant restorations after local bone grafting in maxillas: a 3-year clinical prospective study case series. Clinical Implant Dentistry and Related Research 5, 63-70. Jemt, T. & Lekholm, U. (2005) Single implants and buccal bone grafts in the anterior maxilla: measurements of buccal crestal contours in a 6-year prospective clinical study. Clinical Implant Dentistry and Related Research 7, 127-135. Jensen, O.T., Kuhlke, L., Bedard, J.F. & White, D. (2006) Alveolar segmental sandwich osteotomy for anterior maxillary vertical augmentation prior to implant placement. Journal of Oral and Maxillofacial Surgery 64, 290-296. Jung, R.E., Pjetursson, B.E., Glauser, R., Zembic, A., Zwahlen, M. & Lang, N.P. (2008) A systematic review of the 5-year survival and complication rates of implant-supported single crowns. Clinical Oral Implants Research 19, 119-130. Kan, J.Y., Rungcharassaeng, K. & Lozada, J. (2003a) Immediate placement and provisionalization of maxillary anterior single implants: 1-year prospective study. International Journal of Oral and Maxillofacial Implants 18, 31-39.

Laney, W.R. (2007) Glossary of oral and maxillofacial implants. Berlin. Quintessence. Lazzara, R.J. & Porter, S.S. (2006) Platform switching: a new concept in implant dentistry for controlling postrestorative crestal bone levels. International Journal of Periodontics and Restorative Dentistry 26, 9-17. Lee, D.W., Park, K.H. & Moon, I.S. (2005) Dimension of keratinized mucosa and the interproximal papilla between adjacent implants. Journal of Periodontology 76, 1856-1860. Lekovic, V., Kenney, E.B., Weinlaender, M., Han, T., Klokkevold, P., Nedic, M. & Orsini, M. (1997) A bone regenerative approach to alveolar ridge maintenance following tooth extraction. Report of 10 cases. Journal of Periodontology 68, 563-570. Lindeboom, J.A., Tjiook, Y. & Kroon, F.H. (2006) Immediate placement of implants in periapical infected sites: a prospective randomized study in 50 patients. Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology and Endodontics 101, 705-710. Locante, W.M. (2004) Single-tooth replacements in the esthetic zone with an immediate function implant: a preliminary report. Journal of Oral Implantology 30, 369-375. Lorenzoni, M., Pertl, C., Zhang, K., Wimmer, G. & Wegscheider, W.A. (2003) Immediate loading of single-tooth implants in the anterior maxilla. Preliminary results after one year. Clinical Oral Implants Research 14, 180-187. Maeda, Y., Miura, J., Taki, I. & Sogo, M. (2007) Biomechanical analysis on platform switching: is there any biomechanical rationale? Clinical Oral Implants Research 18, 581-584. Meijer, H.J., Stellingsma, K., Meijndert, L. & Raghoebar, G.M. (2005) A new index for rating aesthetics of implantsupported single crowns and adjacent soft tissues--the Implant Crown Aesthetic Index. Clinical Oral Implants Research 16, 645-649. Meijndert, L., Meijer, H.J., Stellingsma, K., Stegenga, B. & Raghoebar, G.M. (2007) Evaluation of aesthetics of implantsupported single-tooth replacements using different bone augmentation procedures: a prospective randomized clinical study. Clinical Oral Implants Research 18, 715-719. Morton, D., Martin, W.C. & Ruskin, J.D. (2004) Single-stage Straumann dental implants in the aesthetic zone: considerations and treatment procedures. Journal of Oral and Maxillofacial Surgery 62, 57-66.

Kan, J.Y., Rungcharassaeng, K., Umezu, K. & Kois, J.C. (2003b) Dimensions of peri-implant mucosa: an evaluation

Noelken, R., Morbach, T., Kunkel, M. & Wagner, W. (2007) Immediate function with NobelPerfect implants in the anterior dental arch. International Journal of Periodontics and Restorative Dentistry 27, 277-285.

of maxillary anterior single implants in humans. Journal of Periodontology 74, 557-562.

Palmer, R.M., Palmer, P.J. & Smith, B.J. (2000) A 5-year

37

Systematic review

Hall, J.A., Payne, A.G., Purton, D.G., Torr, B., Duncan, W.J. & De Silva, R.K. (2007) Immediately restored, single-tapered implants in the anterior maxilla: prosthodontic and aesthetic outcomes after 1 year. Clinical Implant Dentistry and Related Research 9, 34-45.

2

prospective study of Astra single tooth implants. Clinical Oral Implants Research 11, 179-182. Palmer, R.M., Smith, B.J., Palmer, P.J. & Floyd, P.D. (1997) A prospective study of Astra single tooth implants. Clinical Oral Implants Research 8, 173-179. Pelo, S., Boniello, R., Gasparini, G., Longobardi, G. & Amoroso, P.F. (2007) Horizontal and vertical ridge augmentation for implant placement in the aesthetic zone. International Journal of Oral and Maxillofacial Surgery 36, 944-948. Quirynen, M., Abarca, M., Van,Assche, N., Nevins, M. & Van Steenberghe, D. (2007) Impact of supportive periodontal therapy and implant surface roughness on implant outcome in patients with a history of periodontitis. Journal of Clinical Periodontology 34, 805-815.

Chapter

2

Romeo, E., Chiapasco, M., Ghisolfi, M. & Vogel, G. (2002) Long-term clinical effectiveness of oral implants in the treatment of partial edentulism. Seven-year life table analysis of a prospective study with ITI dental implants system used for single-tooth restorations. Clinical Oral Implants Research 13, 133-143. Romeo, E., Lops, D., Rossi, A., Storelli, S., Rozza, R. & Chiapasco, M. (2008) Surgical and Prosthetic management of interproximal region with single-implant restorations: 1-year prospective study. Journal of Periodontology 79, 1048-1055. Scheller, H., Urgell, J.P., Kultje, C., Klineberg, I., Goldberg, P.V., Stevenson-Moore, P., Alonso, J.M., Schaller, M., Corria, R.M., Engquist, B., Toreskog, S., Kastenbaum, F. & Smith, C.R. (1998) A 5-year multicenter study on implantsupported single crown restorations. International Journal of Oral and Maxillofacial Implants 13, 212-218. Schneider, R. (2008) Implant replacement of the maxillary central incisor utilizing a modified ceramic abutment (Thommen SPI ART) and ceramic restoration. Journal of Esthetic and Restorative Dentistry 20, 21-27. Schropp, L., Isidor, F., Kostopoulos, L. & Wenzel, A. (2005a) Interproximal papilla levels following early versus delayed placement of single-tooth implants: a controlled clinical trial. International Journal of Oral and Maxillofacial Implants 20, 753-761. Schropp, L., Kostopoulos, L., Wenzel, A. & Isidor, F. (2005b) Clinical and radiographic performance of delayedimmediate single-tooth implant placement associated with peri-implant bone defects. A 2-year prospective, controlled, randomized follow-up report. Journal of Clinical Periodontology 32, 480-487. Tarnow, D., Elian, N., Fletcher, P., Froum, S., Magner, A., Cho, S.C., Salama, M., Salama, H. & Garber, D.A. (2003) Vertical distance from the crest of bone to the height of the interproximal papilla between adjacent implants. Journal of Periodontology 74, 1785-1788.

38

Tarnow, D.P., Magner, A.W. & Fletcher, P. (1992) The effect of the distance from the contact point to the crest of bone on the presence or absence of the interproximal dental papilla. Journal of Periodontology 63, 995-996. Weber, H.P., Fiorellini, J.P. & Buser, D.A. (1997) Hardtissue augmentation for the placement of anterior dental implants. Compendium Continuing Education in Dentistry 18, 779-8, 790. Wohrle, P.S. (2003) Nobel Perfect esthetic scalloped implant: rationale for a new design. Clinical Implant Dentistry and Related Research 5 Suppl 1, 64-73. Zetu, L. & Wang, H.L. (2005) Management of inter-dental/ inter-implant papilla. Journal of Clinical Periodontology 32, 831-839.

2

39 Systematic review

3. Single-tooth implants with different neck designs in the aesthetic zone: a randomized clinical trial

This chapter is an edited version of the manuscript: Den Hartog, L., Meijer, H.J., Stegenga, B., Tymstra, N., Vissink, A., Raghoebar, G.M. Single-tooth implants with different neck designs in the aesthetic zone: a randomized clinical trial. Clinical Oral Implants Research (accepted for publication, 2010)

Abstract Aim: To compare single-tooth implants in the aesthetic zone with different neck designs for marginal bone level changes and clinical outcome measures. Material and Methods: 93 patients with a missing anterior tooth in the maxilla were randomly assigned to be treated with an implant with a 1.5 mm smooth neck (‘smooth group’), a moderately rough neck with grooves (‘rough group’) or a scalloped moderately rough neck with grooves (‘scalloped group’). Implants were installed in healed sites and were loaded after 3 months. Follow-up visits were conducted at 6 and 18 months after implant placement.

Chapter

3

Results: The scalloped group showed significantly more radiographic bone loss from implant placement to 18 months (2.01 ± 0.77 mm) compared to the smooth group (1.19 ± 0.82 mm) and rough group (0.90 ± 0.57 mm). Furthermore, the scalloped group showed significantly deeper probing pocket depths and a significantly higher bleeding score. There were no between-group differences in soft tissue levels. Survival rates were 97% for the smooth group and 100% for the rough and scalloped groups (P>0.05). No significant differences in outcome measures were found between the smooth group and rough group. Conclusion: For anterior tooth replacements, implants with a scalloped neck show more marginal bone loss and less favorable clinical outcome compared to implants with a 1.5 mm smooth neck or implants with a rough neck.

42

A lost or congenitally missing tooth in the anterior region usually requires prosthetic replacement for functional and aesthetic reasons. The aesthetic outcome is determined by the appearance of the crown and the surrounding soft tissue, which should be harmonious with the adjacent dentition. Currently, dental implants are widely used for dental rehabilitation, even in aesthetically delicate areas as the anterior maxilla. The level of the peri-implant marginal bone is related to the level of the peri-implant mucosa (Bengazi et al. 1996; Hermann et al. 1997, 2000, 2001; Chang et al. 1999) which, in turn, is commonly considered a major factor determining the aesthetic outcome (Furhauser et al. 2005; Meijer et al. 2005). Loss of peri-implant marginal bone could therefore affect the level of the peri-implant mucosa and hence the final aesthetic outcome. Furthermore, marginal bone loss may induce pocket formation, which could be unfavorable for long-term health of the peri-implant tissue (Rams et al. 1984; Heydenrijk et al. 2002). There is evidence that the design of the implant neck influences the amount of marginal peri-implant bone loss (Shin et al. 2006; Lee et al. 2007; McAllister 2007; Bratu et al. 2009; Nickenig et al. 2009). Although the traditional smooth implant neck is accompanied by the least accumulation of plaque (Teughels et al. 2006; Baldi et al. 2009), several studies have shown more marginal bone loss around these implants compared to implants with a rough surface topography at the implant neck ����������������������������������������������������������������� (Shin et al. 2006; Bratu et al. 2009; Nickenig et al. 2009). Fur���� thermore, it has been reported that retention elements at the implant neck, such as grooves or microthreads, favor the preservation of marginal bone (Palmer et al. 2000; Shin et al. 2006; Lee et al. 2007). In addition, it has been suggested that an implant neck with a scalloped implant platform might preserve proximal marginal bone (Wohrle 2003; Kan et al. 2007; McAllister 2007). Such a scalloped implant neck would mirror the natural alveolar ridge curvature, particularly in the anterior zone, and consequently a more non-violent position of the implant-abutment interface could be realized compared to common flat platform implant designs. There is, however, a paucity of well-designed trials addressing the influence of the implant neck design on bone and soft tissue parameters in single implant cases in the aesthetic zone (Den Hartog et al. 2008). Therefore, the main objective of our study was to compare the marginal bone level change around singletooth implants in the maxillary aesthetic zone with a 1.5 mm smooth neck, a moderately rough neck with grooves and a scalloped moderately rough neck with grooves. In addition, the influence of the implant neck architecture on soft tissue levels and clinical outcome variables was taken into consideration.

43

Implant neck designs

Introduction

3

Material and Methods Patients Patients referred to the department of Oral and Maxillofacial Surgery (University Medical Center Groningen, University of Groningen, Groningen, the Netherlands) for single implant treatment in the maxillary anterior region were considered for inclusion if they fulfilled the following criteria: - at least 18 years of age; - one missing tooth being an incisor, canine or first premolar in the maxilla with adjacent natural teeth; - adequate oral hygiene, i.e. modified plaque index score (Mombelli et al. 1987) and modified sulcus bleeding index score ≤ 1 (Mombelli et al. 1987); - mesial-distal width of diastema at least 6 mm.

Chapter

3

- - - - -

Exclusion criteria were: ASA score ≥ III (Smeets et al. 1998); presence of clinically active periodontal disease as expressed by probing pocket depths ≥ 4 mm and bleeding on probing (index score > 1); p����������������������������������������������������������������������������� resence of peri-apical lesions or any other abnormalities in the anterior region as detected on a radiograph; smoking; a history of radiotherapy to the head and neck region.

Study design This prospective, randomized clinical trial was approved by the Medical Ethical Committee of the University Medical Center Groningen. Patients were included between January 2005 and February 2008. A written informed consent was obtained from all eligible patients before enrolment. A specifically designed locked computer software program was used to randomly assign patients to one of three study groups to be treated with: - a 1.5 mm smooth (‘machined’) implant neck (Replace Select Tapered, Nobel Biocare AB, Göteborg, Sweden) – ‘smooth’ group (Figure 1a); - a moderately rough implant neck with grooves (NobelReplace Tapered Groovy, Nobel Biocare AB) – ‘rough’ group (Figure 1b); - a scalloped moderately rough implant neck with grooves (NobelPerfect Groovy, Nobel Biocare AB) – ‘scalloped’ group (Figure 1c). Randomization by minimization (Altman 1991) was used to balance possible prognostic variables between the three treatment groups. Minimization was used for the variables age (≤30 years, >31 ≤ 60 years, > 60 years), location of the implant site (central or lateral incisor, canine or first premolar) and whether or not a

44

Intervention procedure All implants were placed in healed sites. A minimal period of three months after tooth removal was adopted allowing the extraction site to heal. When bone volume was insufficient for implant placement, a bone augmentation procedure was carried out. As a grafting material, autogenous bone was used together with anorganic bovine bone (Geistlich Bio-Oss®, Geistlich Pharma AG, Wolhusen, Switzerland) covered with a Geistlich Bio-Gide® membrane (Geistlich Pharma AG). Implants were inserted three months after the augmentation procedure. One day prior to implant surgery, patients started taking antibiotics (amoxicillin 500 mg, 3 times daily for 7 days or clindamycin 300 mg, 4 times daily for 7 days in case of amoxicillin allergy) and using a 0.2% chlorhexidine mouthwash (2 times daily for seven days) for oral disinfection. Following local anaesthesia, a slightly palatal crest-incision was made with extensions through the buccal and palatal sulcus of the adjacent teeth and a divergent relieving incision at the distal tooth. A minimal mucoperiosteal flap was prepared to expose the alveolar ridge. The implant site was prepared by using a surgical template that was fabricated in the dental laboratory, based on the prospective implant crown in its ideal position. All implants were installed with a torque controller (OsseoCare, Nobel Biocare AB) adjusted to an insertion torque of 45 Ncm and by using a manual torque wrench (Nobel Biocare AB) for fine-tuning of the implant depth. The shoulder of the implant was placed at a depth of 3 mm apical to the most facial and cervical aspect of the prospective clinical crown for proper emergence profile. For the scalloped implants the mid-facial part of the implant shoulder was taken as a reference. In all cases the alveolar bone was levelled to the implant shoulder. When part of the implant remained uncovered or when the bone wall thickness facially to the implant was < 2mm, a local augmentation procedure was performed with autogenous bone chips collected during implant bed preparation and anorganic bovine bone (Geistlich Bio-Oss®) covered with a Geistlich Bio-Gide® membrane. The wound was closed with Ethilon 5-0 nylon sutures (Johnson & Johnson Gateway, Piscatatway, United States). During the healing phase, patients were wearing a removable partial denture that did not interfere with the wound. After three months, implants were uncovered and a healing abutment (Nobel Biocare AB) was installed. One week after the second stage operation, an implant-level impression was made. In the dental laboratory, a screw-retained provisional crown was fabricated 45

Implant neck designs

pre-implant augmentation procedure was indicated based on a clinical and diagnostic cast assessment. The allocation result was kept in a locked computer file that was not accessible for the examiner and the practitioners. The surgeon that inserted the implants was informed about the allocation on the day of surgery.

3

Chapter

3

by means of an engaging temporary abutment and composite (Solidex, Shofu inc., Kyoto, Japan). The provisional crowns were screwed directly onto the implant with 32 Ncm as indicated by a manual torque wrench (Nobel Biocare AB). After a provisional phase of three months (i.e., six months post-implant placement), a final impression was taken on implant level. In the laboratory, a waxing of the definitive crown was made that was cut back to the desired form of the abutment. The wax-up was scanned to retrieve individualized zirconia abutments (Procera, Nobel Biocare AB) for the implants in the smooth group and rough group and individualized titanium abutments (Procera, Nobel Biocare AB) for the implants in the scalloped group, since zirconia abutments were not available for these implants. A zirconica Procera coping (Procera, Nobel Biocare AB) was luted over the titanium abutments in order to create an abutment with a zirconia outside. Depending on the location of the screw access hole, the final crown was either cement-retained using a zirconia coping (Procera, Nobel Biocare AB) or screw-retained by fusing porcelain directly to the abutment. Abutment screws were torqued with 32 Ncm. Cement-retained crowns were cemented with glass ionomer cement (Fuji Plus, GC Europe, Leuven, Belgium). For more details regarding product specifications, we refer to a previous clinical report (Den Hartog et al. 2009). All surgical procedures were performed by a single experienced oral and maxillofacial surgeon. The prosthetic procedure was accomplished by two experienced prosthodontists and all crowns were fabricated by one dental technician.

Outcome measures The primary outcome measure of this study was marginal bone level change proximal to the implant 18 months after implant placement measured on radiographs. Secondary outcome measures were implant survival, change in peri-implant mucosal level and its position compared with the gingival level of the contralateral tooth, papilla volume (papilla index), amount of plaque (plaque index), bleeding after probing (bleeding index) and probing pocket depth. In addition to the implant, also the adjacent teeth were analyzed. The operationalization of variables is described below. Radiographic and photographic assessments After implant placement (baseline, T0) and after 6 (T6m, after definitive crown placement, equals 3 months of functional loading) and 18 months (T18m, equals 12 months after definitive crown placement and 15 months of functional loading), standardized digital intra-oral radiographs were taken according to a long-cone paralleling technique and with a device as described by Meijndert and colleagues (Meijndert et al. 2004). The same device was used to gather standardized digital photographs (camera: Fuji-film FinePix S3 Pro) before implant placement (Tpre) 46

Clinical assessments Before implant placement (Tpre), and 6 (T6m) and 18 months after implant placement (T18m), patients were seen for clinical data collection. Both the implant and the adjacent teeth were analyzed at the facial aspect. All data were retrieved by one examiner according to a specified protocol. The following variables were evaluated: - plaque, using the modified plaque index (Mombelli et al. 1987): 0 = no detection of plaque, 1 = plaque can be detected by running a probe across the surface of the crown, 2 = plaque visible with the naked eye, and 3 = abundance 47

Implant neck designs

and at T6m and T18m, together with digital photographs of the implant and contralateral tooth at T18m taken with the same camera. For calibration of the photographs, a calibrated probe was held in close contact and parallel to the long axis of a tooth adjacent to the implant. By using the same device, both the radiographs and the photographs were taken from the same horizontal and vertical angulation. All measurements were performed by one examiner and were blinded for the photographs. The radiographic examination could not be blinded, since the type of implant neck could be derived directly from the radiographs. Full-screen analysis of the radiographs was performed using specifically designed software. First, the radiographs were calibrated according to the known diameter of the implant. Next, different reference points were marked and marginal bone levels proximal to the implant were measured according to the first bone-to-implant contact together with marginal bone levels of the adjacent teeth (Figures 1a,b,c). Full-screen analysis of the photographs was performed using Adobe Photoshop (Adobe Photoshop CS3 Extended, Adobe Systems Inc., San Jose, USA). After calibration, mid-facial mucosal and papilla levels of the implant were measured after definitive crown placement (at T6m and T18m). Mid-facial gingival levels of the adjacent teeth were measured from Tpre. The incisal edges of the implant crown and adjacent teeth were used as reference. To assess the reliability of the radiographic and photographic examinations, 14 radiographs and 14 photographs from each study group (i.e., 15% of all radiographs and photographs) were randomly selected and were measured by two examiners and by one examiner twice with a two-week interval. The intra-observer agreement of the photographic examination was tested earlier and reported as good with a mean difference of 0.11±0.02 mm between both times of measurements (Meijndert et al. 2004). The facial peri-implant mucosal level (PML) was compared with the gingival level of the contralateral tooth on photographs taken at T18m and was judged as follows: identical level; slight deviation 45Ncm). Details about the surgical and prosthetic procedures applied in the various treatment groups are depicted in table 1. In two patients (one in the smooth group and one in the scalloped group) a pre-implant augmentation procedure, which was not indicated beforehand appeared to be necessary during implant surgery and the implants were inserted three months later. All patients attended the follow-up visits at T18m. One patient in the scalloped group did not attend the recall visit at T6m. Reliability of radiographic and photographic assessments The assessment of the intra-observer agreement of the radiographic examination, revealed a mean difference between the repeated measurements of -0.01 ± 0.25 mm (limits of agreement: - 0.50 mm and 0.50 mm). A difference in the range of -0.2 to 0.2 mm was found in 70.7% of the measurements and a difference in the range of -0.5 to 0.5 mm in 92.8% of the measurements (we considered 0.5 mm as a relevant difference in our power analysis). The assessments of the radiographic and photographic inter-observer agreement, showed mean differences between the observers of 0.08 ± 0.31 mm for the radiographs (limits of agreement: -0.69 and 0.54 mm) and -0.02 ± 0.18 mm for the photographs (limits of agreement: -0.38 and 0.34 mm). For the radiographs, an inter-observer difference in the range of -0.2 to 0.2 mm and in the range of -0.5 to 0.5 mm was found in 54.2% and 89.5 % of the measurements respectively. For the photographs, these percentages were 83.5% and 96.1%. The intraclass correlation coefficients were 0.96 and 0.99 for the radiographic inter- and intra-observer agreement, respectively, and 0.99 for the photographic inter-observer agreement, all signifying high levels of agreement. 50

Smooth group (n=31)

Rough group (n=31)

Scalloped group (n=31)

Mean age ± standard deviation (range)

37.2 ± 12.9 (18-60)

40.1 ± 14.4 (18-67)

40.1 ± 17.2 (19-80)

Male/female ratio

15/16

17/14

14/17

Implant site location I1 / I2 / C / P1

20 / 7 / 1 / 3

18 / 8 / 3 / 2

18 / 6 / 3 / 4

Cause of tooth absence Fracture (crown or root) Agenesis Endodontic failure Periodontal failure Root resorption

19 3 2 1 6

15 4 8 2 2

21 3 2 2 3

12

11

10

Implant-tooth distance (mm) Mean ± SD Range

2.36 ± 0.76 0.70 – 4.59

2.17 ± 0.77 0.45 - 5.26

2.30 ± 0.65 0.56 ± 5.15

Type of final restoration Screw-retained Cement-retained

15 14

12 19

11 20

Variable

Augmentation before implant surgery*

*implant was placed 3 months later

Change in marginal bone level The total amount of mean marginal bone loss (mesial and distal implant sides combined) between baseline (T0, implant placement) and T18m (18 months after implant placement) was 1.19 ± 0.82 mm in the smooth group [95% confidence interval (CI): 0.89-1.49], 0.90 ± 0.57 mm in the rough group [95% CI: 0.70-1.10] and 2.01 ± 0.77 mm in the scalloped group [95% CI: 1.74-2.28] and was significantly different (Figure 2). The scalloped group showed significantly more marginal bone loss from T0 to T18m at both proximal implant sides compared to the other study groups (Table 2). There were no significant differences between the smooth and rough study groups. The most extensive marginal bone loss was observed during the first evaluation period (from T0 to T6m, mesial and distal sides combined: smooth group 1.05 ± 0.69, rough group 0.80 ± 0.57, scalloped group 1.77 ± 0.82) and was significantly lower for the second evaluation period (from T6m to T18m: 51

Implant neck designs

Table 1. Baseline characteristics and treatment specifications per study group.

3

smooth group 0.13 ± 0.31, rough group 0.11 ± 0.28, scalloped group 0.23 ± 0.43). Marginal bone loss at the adjacent teeth was limited, and there were no significant differences between the study groups. Figure 2. Error plot of marginal bone loss from implant placement to 18 months thereafter.

Chapter

3

$*.FBOCPOFMPTT55

 

 

 

 

  4NPPUIHSPVQ O

3PVHIHSPVQ O

4DBMMPQFEHSPVQ O

1BUJFOUHSPVQ

Clinical outcomes One implant in the smooth group was lost five months after implant placement during the provisional phase. It appeared that this implant was not integrated. The implant survival rate at T18m was 96.8 % for the smooth group and 100% for the rough and scalloped study groups. The photographic assessments did not yield between-group differences in midfacial peri-implant mucosal levels and papilla levels during follow-up (Table 2). After definitive crown placement, the level of the mid-facial peri-implant mucosa remained stable, while a gain in papilla height was observed (Table 2). The midfacial gingival level of the adjacent teeth showed a mean recession of 0.18±0.45 mm, 0.28±0.36 mm and 0.25±0.29 mm in the smooth, rough and scalloped groups, respectively. It appeared that the level of the peri-implant mucosa (PML) was identical to the contralateral tooth in 14 cases (48%) in the smooth group, 13 (42%) in the rough group, and 18 (58%) in the scalloped group. A major discrepancy (≥ 1.5 mm) was found in 4 cases (14%) in the smooth group, 4 in the rough group (13%) and 2 in the scalloped group (6%). Differences were not significant. 52

-1.15 ± 0.82

-0.23 ± 0.45

-0.20 ± 0.42

Distal of implant

Mesial tooth side

Distal tooth side

37.5

14.6

1-2 mm

≥ 2 mm

-0.37 ± 0.53

0.02 ± 0.23

-0.14 ± 0.39

Distal tooth

-0.33 ± 0.51

-0.10 ± 0.26

-0.14 ± 0.31

Mesial tooth

-0.19 ± 0.23

-0.09 ± 0.23

Mid-facial of implant -0.13 ± 0.38

0.14 ± 0.35

0

3.9

96.1

0.02 ± 0.28

-0.01 ± 0.25

-0.13 ± 0.47

-0.13 ± 0.45

Smooth (n=30)†

Distal implant papilla

44.0

38.0

18.0*

-0.29 ± 0.44

-0.30 ± 0.50

-1.70 ± 0.98*

-1.84 ± 0.93*

Scalloped (n=31)

0.12 ± 0.44

3.2

33.9

62.9

-0.18 ± 0.34

-0.25 ± 0.38

-0.81 ± 0.76

-0.79 ± 0.62

Rough (n=31)

Baseline#-T6m

Mesial implant papilla

Marginal soft tissue level changes (mm)

47.9

≤ 1 mm

Implant bone loss (%)§

-0.96 ± 0.76

Smooth (n=30)†

Mesial of implant

Marginal bone level changes (mm)

Variable

0.00 ± 0.30

-0.09 ± 0.25

-0.09 ± 0.34

0.35 ± 0.52

0.19 ± 0.29

0

0

100

-0.03 ± 0.42

0.03 ± 0.28

-0.09 ± 0.41

-0.13 ± 0.40

Rough (n=31)

T6m- T18m

0.10 ± 0.21

-0.02 ± 0.25

0.03 ± 0.22

0.24 ± 0.43

0.27 ± 0.47

0

5.8

94.2

0.02 ± 0.24

0.02 ± 0.25

-0.30 ± 0.46

-0.16 ± 0.58

Scalloped (n=30)‡

-0.12 ± 0.44

-0.24 ± 0.50

10.9

47.8

41.3

-0.17 ± 0.44

-0.24 ± 0.50

-1.27 ± 1.09

-1.10 ± 0.83

Smooth (n=30)†

-0.33 ± 0.36

-0.22 ± 0.36

4.8

38.7

56.5

-0.29 ± 0.50

-0.17 ± 0.40

-0.90 ± 0.77

-0.91 ± 0.66

Rough (n=31)

Baseline#- T18m

-0.28 ± 0.44

-0.21 ± 0.36

52.6

35.1

12.3*

-0.27 ± 0.54

-0.28 ± 0.50

-2.00 ± 1.01*

-2.01 ± 0.74*

Scalloped (n=31)

Table 2. Changes in marginal bone level and marginal soft tissue level and probing pocket depths at implant and tooth sides from baseline to 18 months.

53

Smooth

1.40 ± 0.53

1.92 ± 0.49

3.07 ± 0.74

3.50 ± 0.82

3.03 ± 0.89

Rough

T6m

1.28 ± 0.37

1.92 ± 0.39

3.47 ± 0.97

3.67 ± 0.99

3.80 ± 1.24*

Scalloped

Plus-minus values are means ± standard deviations. #After implant placement for bone levels, before implant placement for soft tissue levels and probing pocket depths. † One implant was lost. ‡ One patient did not attend follow-up visit T6m. * P < 0.05, between-group comparison. § Mesial and distal sides combined. Abbreviations: T6m = 6 months post-implant placement, T18m = 18 months post-implant placement.

1.29 ± 0.39

Mid-facial of teeth

1.45 ± 0.44

1.27 ± 0.39

Proximal of teeth§ 1.37 ± 0.39

3.34 ± 0.72 2.18 ± 0.37

2.20 ± 0.57

Mid-facial of implant

3.41 ± 1.05

2.11 ± 0.50

Scalloped

Distal of implant

2.03 ± 0.51

Rough

3.45 ± 0.87

Smooth

Baseline#

Mesial of implant

Pocket depth (mm)

Table 2. (continued)

54

1.24 ± 0.32

2.15 ± 0.41

3.10 ± 0.82

3.24 ± 0.79

3.34 ± 1.20

Smooth

1.37 ± 0.34

1.99 ± 0.60

3.32 ± 0.79

3.81 ± 1.28

3.19 ± 0.91

Rough

T18m

1.37 ± 0.39

1.99 ± 0.65

3.65 ± 0.92*

4.63 ± 1.13*

4.42 ± 1.18*

Scalloped

Figure 3. Frequency distribution of bleeding index scores of implants and adjacent teeth at 18 months after implant placement. #MFFEJOH*OEFY5N 

TDPSF OPCMFFEJOH 

 





TDPSF JTPMBUFECMFFEJOHTQPUT



TDPSF DPOGMVFOUMJOFPGCMPPE  



TDPSF QSPGVTFCMFFEJOH









 

  

4NPPUI

3PVHI 4DBMMPQFE

5FFUI

4NPPUI



3PVHI

*NQMBOU

55



4DBMMPQFE

Implant neck designs

Between-group analyses showed significant differences for probing pocket depths at T18m at all sides and mesially at T6m (Table 2). Post-hoc analyses revealed significantly deeper probing pocket depths in the scalloped group at T18m compared to the smooth group at all sides and compared to the rough group at both proximal sides. At T6m at mesial sides, significantly deeper probing pocket depths were found in the scalloped group compared to the rough group. Bleeding index scores were significantly higher for the scalloped group at T18m (Figure 3). There were no between-group differences in plaque scores and papilla index scores (Figure 4) at both follow-up examinations and no differences in bleeding scores at T6m. Plaque index scores were low at both follow-up visits. At T18m, a plaque score of 1 was assigned to one implant in the smooth group and 3 implants in the other study groups. All other implants did not show any plaque. With regard to between-group comparisons of the adjacent teeth, no differences in clinical outcomes were found. Bleeding index scores of the adjacent teeth were significantly lower compared to the scores of the implants.

3

Figure 4. Frequency distribution of papilla index scores at 6 and 18 months after implant placement.

1BQJMMB*OEFY  



TDPSF OPQBQJMMB

 







TDPSF MFTTUIBOIBMGPGUIFQBQJMMB TDPSF BUMFBTUIBMGPGUIFQBQJMMB



 





Chapter

3



TDPSF DPNQMFUFQBQJMMB







 



4NPPUI

3PVHI 4DBMMPQFE

4NPPUI









3PVHI 4DBMMPQFE

5N

5N

Within-group analyses showed that the volume of the papillae, expressed in papilla index scores, increased significantly during follow-up (smooth implants, both papillae; rough implants, distal papillae; scalloped implants, distal papillae) (Figure 4). The scalloped implants showed significantly higher bleeding index scores at T18m compared to T6m. The adjacent teeth showed significantly higher plaque scores at Tpre versus T6m and T18m. Complications that arose during the restorative phase and after placement of the definitive crown are depicted in Table 3. The scalloped implants showed the most complications. All complications could be successfully resolved. The complications of biological origin were treated with a minimally invasive surgical approach. For the patient that developed peri-implantitis (symptoms: implant probing depth 6 mm with profuse bleeding, progressive radiographic bone loss, pain) cement-remnants together with a moderate oral hygiene and recommenced smoking, probably were the etiologic factors. During treatment of one fistula, cement remnants were removed, while the etiology of the other fistula was unclear.

56

Smooth group (n=30)†

Rough group (n=31)

Scalloped group (n=31)

Mobile provisional crown

2

1

2

Fracture of provisional crown

0

1

1

Mobile definitive crown

0

0

3

Porcelain fracture

0

2

6 (2 in one patient)

Bent fixation screw (after trauma)

1

0

0

Peri-implantitis

0

1

0

Fistula

0

0

2

Complication

† One implant was lost.

Regression and correlation analysis The regression analysis revealed that only the type of implant neck was significantly associated with the change in marginal bone level (Table 4). The other independent variables did not contribute significantly. The implant site could not be included in the analysis, since there were not enough cases in which a tooth other than a central incisor was replaced. The correlation analysis showed that the amount of marginal bone loss at both proximal sides was positively related to probing pocket depth at that side (correlation coefficient mesial side 0.27; distal side 0.32). Furthermore, the total amount of marginal bone loss (mesial and distal sides combined) was positively correlated to probing pocket depth mid-facially with a coefficient of 0.34. No other significant correlations were found.

57

Implant neck designs

Table 3. Complications during 18 months of follow-up.

3

Table 4.

Outcome of multiple regression analysis. B

SE B

ß

Constant

2.01

0.13

Type of implant Scalloped vs. Rough Scalloped vs. Smooth

-1.12 -0.83

0.18 0.18

1.93

0.52

-1.07 -0.94

0.18 0.18

-0.61* -0.52*

Augmentation before implant surgery

-0.02

0.16

-0.02

Implant-tooth distance

0.20

0.11

0.17

Step 1

-0.62* -0.46*

Step 2 Constant Type of implant Scalloped vs. Rough Scalloped vs. Smooth

Chapter

3

Type of definitive crown

-0.15

0.15

-0.09

Age

-0.01

0.01

-0.14

0.12

0.15

0.07

Gender

R = 0.33 for Step 1; Δ R = 0.06 for Step 2 (P>0.05). * P < 0.05 Abbreviations: SE = Standard Error. 2

2

Discussion This study compared the effect of three different implant neck designs on preservation of marginal bone for single-tooth implants in the maxillary aesthetic zone. Implants had a 1.5 mm smooth implant neck (‘smooth group’), a moderately rough implant neck with grooves (‘rough group’) and a scalloped moderately rough implant neck with grooves (‘scalloped group’). The results of our study showed that after 18 months of follow-up, there was a significant difference in radiographic marginal bone loss between the study groups that could entirely be attributed to the scalloped group. In addition to more bone loss, the scalloped group revealed deeper probing pocket depths and higher bleeding scores than the smooth group and rough group. Post-hoc analyses did not reveal significant differences in outcome between the smooth group and rough group. The smooth and rough group revealed favorable treatment outcomes in terms of bone loss, implant survival, complications and soft tissue aspects, which are in line with values reported in other studies on single-tooth implants placed in the anterior maxilla (Den Hartog et al. 2008). 58

59

Implant neck designs

Although not supported by our data, several other studies have demonstrated significantly more marginal bone loss around implants with a smooth neck compared to a rough neck (Hermann et al. 2000; Shin et al. 2006; Schwarz et al. 2008; Bratu et al. 2009; Nickenig et al. 2009; Stein et al. 2009). Also, ��������������������� it has been reported that retention elements, such as microthreads or grooves, could decrease marginal bone resorption (Shin et al. 2006; Lee et al. 2007; Nickenig et al. 2009). Since these studies mainly focused on posterior tooth replacements or were nonclinical of origin, it is questionable whether these results can be extrapolated to our findings. For instance, Nickenig et al. (2009) compared smooth and rough implants for restoring missing mandibular molars. They reported that from implant placement to two years thereafter, the rough implant neck with grooves was superior to the smooth neck in reducing radiographic marginal bone loss (mean bone loss 0.5 mm vs 1.1 mm, standard deviation not reported, however). We found 0.90 ± 0.57 mm marginal bone loss around the moderately rough implant neck and 1.19 mm ± 0.82 mm around the smooth implant neck. In our study, all implants were placed at a 3 mm depth from the implant shoulder to the buccal and cervical aspect of the prospective clinical crown. All implants were levelled with the alveolar bone crest so that the whole implant neck was covered with bone (in some cases, an additional augmentation procedure was performed to cover the implant neck). It has been found that the position of the implant-abutment interface relative to the bone crest at the time of implant placement is a significant factor for marginal bone loss (Hermann et al. 2000; Broggini et al. 2006; Jung et al. 2008). An inflammatory reaction at the implantabutment interface due to microbial leakage seems to be a major factor for this bone loss. A more apical position of the implant-abutment interface will increase the inflammatory reaction and will induce more marginal bone loss. Since in our study the implant-abutment interface was closely related to the bone crest, possibly surface roughness or grooves could not realize less marginal bone resorption than a smooth surface. We found significantly more marginal bone loss around the scalloped implant neck compared to the other implants with common flat platforms. To date, only case reports and cases series have been published addressing the outcome of scalloped implants (Mitrani et al. 2005; Nowzari et al. 2006; Kan et al. 2007; McAllister 2007; Noelken et al. 2007). Unfortunately, no other clinical trials on the scalloped implant have been published�������������������������������������� . ������������������������������������ Since case series are highly susceptible to bias, results of these studies should be interpreted with caution. When placed in healed extraction sites, the mean radiographic bone loss ranged from 1.5 to 2.1 mm (standard deviations around 1 mm) between implant placement and 12 months thereafter (Nowzari et al. 2006; Kan et al. 2007; McAllister 2007). These values were found for the original version of the scalloped implant with a

3

Chapter

3

1.5 mm smooth collar. We observed a mean bone loss of 2.0 ± 0.77 mm around the scalloped neck after 18 months, although it was equipped with a moderately rough surface and grooves, which could favor marginal bone preservation. We do not have a proper explanation for the finding that the scalloped implant showed more radiographic bone loss than the other study groups. One reason might be that peri-implant bone is mainly formed in a horizontal plane. As a result, bone at the proximal side of the implant might tend to be lost to equilibrate the more apical level of the mid-facial and mid-palatal peri-implant bone crest. Another reason could be inferred from a biomechanical point of view. Too much stress at the implant neck after loading, and shear stresses in particular, induces initial marginal bone resorption (Oh et al. 2002; Schrotenboer et al. 2008). It has been hypothesized that after this initial resorption, bone loss slows down at the first thread when shear stresses change into more favorable compressive forces induced by the thread itself (Oh et al. 2002). It might be that the stress distribution from the scalloped implant to the bone was unfavorable and too high, leading to the amount of marginal bone loss as was observed during the first evaluation period. In this context, the complex connection between implant and abutment could play a role. However, stress models of scalloped implants are lacking. We do not feel that the radiographic analysis had shortcomings in detecting the small and less dense proximal bone peak around the scalloped implant, as has been suggested in some studies (Wohrle 2006; McAllister 2007). In this view, the clinical observation of deeper probing pocket depths can be adduced. As was expected from other studies (Cardaropoli et al. 2006; Den Hartog et al. 2008; Meijndert et al. 2008; Bratu et al. 2009; Nickenig et al. 2009), the most extensive marginal bone loss was observed during the first evaluation period (i.e., from implant placement to T6m). During the next 12 months (at T18m), only minor marginal bone loss was noticed. This is consistent with the stable level of the mid-facial peri-implant mucosa as measured during the second evaluation period. The level of the papilla, however, was not stable but gained some height. Expressed in papilla index scores, this resulted in higher scores at T18m compared to T6m for all implant groups. This phenomenon has been reported in several single-tooth implant studies reporting comparable papilla index scores (Jemt & Lekholm 2003, Schropp et al. 2005a; Den Hartog et al. 2008; Meijndert et al. 2008). Neither ������������������������������������������������������������������������ from these studies nor from the current study could this phenomenon be validly explained. Within the whole study population, the changes in marginal peri-implant bone level were not correlated with the volume of the papilla expressed in papilla index scores neither with the facial peri-implant mucosal level (PML) compared to the contralateral tooth. At T18m, the scalloped group did not show lower volume of the papilla expressed in papilla index scores and no higher discrepancies in PML than 60

61

Implant neck designs

observed in the other study groups. With respect to the volume of the papilla, it should be realized that the bone level at the adjacent teeth may play a significant role. It is known that the level of the papilla is highly related to the bone level next to the adjacent teeth (Choquet et al. 2001; Kan et al. 2003; Romeo et al. 2008). We observed only minor marginal bone loss at the adjacent teeth without differences between study groups. This prominent role of the adjacent teeth may also apply to the preservation of the PML. Besides, for this variable, the soft tissue level before implant placement could be more relevant to the future PML while the future PML is to a lesser degree related to the amount of marginal bone loss around the implant neck. All implants were placed in healed extraction sites, one third of which were augmented. This might have had a significant effect on the level of the PML before implant placement. We measured deeper pocket depths around the scalloped implants together with higher bleeding scores at T18m compared to the other study groups. These values increased significantly within the scalloped group during follow-up, despite radiographic marginal bone levels remaining stable. It seems that the peri-implant tissue in the scalloped group developed more marginal inflammation with time as confirmed by the higher bleeding scores. However, the few studies on single-tooth implants in the anterior maxillary region that have considered pocket depths, reported comparable pocket depths as we observed around the scalloped implants (Den Hartog et al. 2008). Although there is no evidence that pocket depth is a risk factor for developing peri-implantitis and deteriorates the prognosis (Schropp et al. 2005b; Heitz-Mayfield 2008), we believe that pocket depths should be limited and remain stable over time to facilitate healthy peri-implant tissue. From this study, it can be concluded that there are differences between anterior single-tooth implants with a 1.5 mm smooth neck, a moderately rough neck with grooves and with a scalloped moderately rough neck with grooves in preserving marginal bone as measured on radiographs. This effect can be attributed entirely to the implants with a scalloped neck, showing significantly more marginal bone loss than the other implant designs studied. Furthermore, deeper probing pockets depths and more bleeding were observed around these implants. Post-hoc analyses revealed no differences between the implants with a smooth neck and implants with a moderately rough neck with grooves in preserving marginal bone, and no differences in survival, soft tissue aspects and complications. Besides, these implants showed favorable results as compared to what has been established in other studies on anterior single-tooth implants. We therefore suggest the use of either an implant with a 1.5 mm smooth neck or an implant with a moderately rough neck with grooves for replacement of a single missing anterior tooth as the scalloped implant design showed more bone loss and less favorable clinical performance.

3

References

relation and regression analyses. Behavior Research Methods 41, 1149-1160.

Altman, D.G. (1991) Practical Statistics for Medical Research. London: Chapman & Hall. Baldi, D., Menini, M., Pera, F., Ravera, G. & Pera, P. (2009) Plaque accumulation on exposed titanium surfaces and periimplant tissue behavior. A preliminary 1-year clinical study. International Journal of Prosthodontics 22, 447-455. Bengazi, F., Wennstrom, J.L. & Lekholm, U. (1996) Recession of the soft tissue margin at oral implants. A 2-year longitudinal prospective study. Clinical Oral Implants Research 7, 303-310. Bratu, E.A., Tandlich, M. & Shapira, L. (2009) A rough surface implant neck with microthreads reduces the amount of marginal bone loss: a prospective clinical study. Clinical Oral Implants Research 20, 827-832.

Chapter

3

Broggini, N., McManus, L.M., Hermann, J.S., Medina, R., Schenk, R.K., Buser, D. & Cochran, D.L. (2006) Periimplant inflammation defined by the implant-abutment interface. Journal of Dental Research 85, 473-478. Cardaropoli, G., Lekholm, U. & Wennstrom, J.L. (2006) Tissue alterations at implant-supported single-tooth replacements: a 1-year prospective clinical study. Clinical Oral Implants Research 17, 165-171. Chang, M., Wennstrom, J.L., Odman, P. & Andersson, B. (1999) Implant supported single-tooth replacements compared to contralateral natural teeth. Crown and soft tissue dimensions. Clinical Oral Implants Research 10, 185-194. Choquet, V., Hermans, M., Adriaenssens, P., Daelemans, P., Tarnow, D.P. & Malevez, C. (2001) Clinical and radiographic evaluation of the papilla level adjacent to single-tooth dental implants. A retrospective study in the maxillary anterior region. Journal of Periodontology 72, 1364-1371. Den Hartog, L., Slater, J.J., Vissink, A., Meijer, H.J. & Raghoebar, G.M. (2008) Treatment outcome of immediate, early and conventional single-tooth implants in the aesthetic zone: a systematic review to survival, bone level, soft tissue, aesthetics and patient satisfaction. Journal of Clinical Periodontology 35, 1073-1086. Den Hartog, L., Raghoebar, G.M., Stellingsma, K. & Meijer, H.J. (2009) Immediate loading and customized restoration of a single implant in the maxillary esthetic zone: a clinical report. Journal of Prosthetic Dentistry 102, 211-215. Furhauser, R., Florescu, D., Benesch, T., Haas, R., Mailath, G. & Watzek, G. (2005) Evaluation of soft tissue around single-tooth implant crowns: the pink esthetic score. Clinical Oral Implants Research 16, 639-644. Faul, F., Erdfelder, E., Buchner, A., & Lang, A.G. (2009) Statistical power analyses using G*Power 3.1: Tests for cor-

62

Gehrke, P., Lobert, M. & Dhom, G. (2008) Reproducibility of the pink esthetic score--rating soft tissue esthetics around single-implant restorations with regard to dental observer specialization. Journal of Esthetic and Restorative Dentistry 20, 375-384. Heitz-Mayfield, L.J. (2008) Peri-implant diseases: diagnosis and risk indicators. Journal of Clinical Periodontology 35, 292-304. Hermann, J.S., Buser, D., Schenk, R.K. & Cochran, D.L. (2000) Crestal bone changes around titanium implants. A histometric evaluation of unloaded non-submerged and submerged implants in the canine mandible. Journal of Periodontology 71, 1412-1424. Hermann, J.S., Buser, D., Schenk, R.K., Schoolfield, J.D. & Cochran, D.L. (2001) Biologic Width around one- and two-piece titanium implants. Clinical Oral Implants Research 12, 559-571. Hermann, J.S., Cochran, D.L., Nummikoski, P.V. & Buser, D. (1997) Crestal bone changes around titanium implants. A radiographic evaluation of unloaded nonsubmerged and submerged implants in the canine mandible. Journal of Periodontology 68, 1117-1130. Heydenrijk, K., Meijer, H.J., van der Reijden, W.A., Raghoebar, G.M., Vissink, A., Stegenga, B. (2002) Microbiota around root-form endosseous implants: a review of the literature. International Journal of Oral and Maxillofacial Implants 17, 829-838. Jemt, T. (1997) Regeneration of gingival papillae after single-implant treatment. International Journal of Periodontics and Restorative Dentistry 17, 326-333. Jemt, T. & Lekholm, U. (2003) Measurements of buccal tissue volumes at single-implant restorations after local bone grafting in maxillas: a 3-year clinical prospective study case series. Clinical Implant Dentistry and Related Research 5, 63-70. Jung, R.E., Jones, A.A., Higginbottom, F.L., Wilson, T.G., Schoolfield, J., Buser, D., Hammerle, C.H. & Cochran, D.L. (2008) The influence of non-matching implant and abutment diameters on radiographic crestal bone levels in dogs. Journal of Periodontology 79, 260-270. Kan, J.Y., Rungcharassaeng, K., Liddelow, G., Henry, P. & Goodacre, C.J. (2007) Periimplant tissue response following immediate provisional restoration of scalloped implants in the esthetic zone: a one-year pilot prospective multicenter study. Journal of Prosthetic Dentistry 97, S109-S118. Kan, J.Y., Rungcharassaeng, K., Umezu, K. & Kois, J.C. (2003) Dimensions of peri-implant mucosa: an evaluation of maxillary anterior single implants in humans. Journal of Periodontology 74, 557-562.

McAllister, B.S. (2007) Scalloped implant designs enhance interproximal bone levels. International Journal of Periodontics and Restorative Dentistry 27, 9-15. Meijer, H.J., Stellingsma, K., Meijndert, L. & Raghoebar, G.M. (2005) A new index for rating aesthetics of implantsupported single crowns and adjacent soft tissues--the Implant Crown Aesthetic Index. Clinical Oral Implants Research 16, 645-649. Meijndert, L., Meijer, H.J., Raghoebar, G.M. & Vissink, A. (2004) A technique for standardized evaluation of soft and hard peri-implant tissues in partially edentulous patients. Journal of Periodontology 75, 646-651. Meijndert, L., Raghoebar, G.M., Meijer, H.J. & Vissink, A. (2008) Clinical and radiographic characteristics of singletooth replacements preceded by local ridge augmentation: a prospective randomized clinical trial. Clinical Oral Implants Research 19, 1295-1303. Mitrani, R., Adolfi, D. & Tacher, S. (2005) Adjacent implantsupported restorations in the esthetic zone: understanding the biology. Journal of Esthetic and Restorative Dentistry 17, 211-222. Mombelli, A., van Oosten, M.A., Schurch E Jr & Land, N.P. (1987) The microbiota associated with successful or failing osseointegrated titanium implants. Oral Microbiology and Immunology 2, 145-151. Nickenig, H.J., Wichmann, M., Schlegel, K.A., Nkenke, E. & Eitner, S. (2009) Radiographic evaluation of marginal bone levels adjacent to parallel-screw cylinder machined-neck implants and rough-surfaced microthreaded implants using digitized panoramic radiographs. Clinical Oral Implants Research 20, 550-554. Noelken, R., Morbach, T., Kunkel, M. & Wagner, W. (2007) Immediate function with NobelPerfect implants in the anterior dental arch. International Journal of Periodontics and Restorative Dentistry 27, 277-285. Nowzari, H., Chee, W., Yi, K., Pak, M., Chung, W.H. & Rich, S. (2006) Scalloped dental implants: a retrospective analysis of radiographic and clinical outcomes of 17 NobelPerfect implants in 6 patients. Clinical Implant Dentistry and Related Research 8, 1-10. Oh, T.J., Yoon, J., Misch, C.E. & Wang, H.L. (2002) The causes of early implant bone loss: myth or science? Journal of Periodontology 73, 322-333. Palmer, R.M., Palmer, P.J. & Smith, B.J. (2000) A 5-year prospective study of Astra single tooth implants. Clinical Oral Implants Research 11, 179-182.

Rams, T.E., Roberts, T.W., Tatum, H. Jr, Keyes, P.H. (1984) The subgingival microbial flora associated with human dental implants. Journal of Prosthetic Dentistry 51, 529-534 Romeo, E., Lops, D., Rossi, A., Storelli, S., Rozza, R. & Chiapasco, M. (2008) Surgical and prosthetic management of interproximal region with single-implant restorations: 1-year prospective study. Journal of Periodontology 79, 1048-1055. Schropp, L., Isidor, F., Kostopoulos, L. & Wenzel, A. (2005a) Interproximal papilla levels following early versus delayed placement of single-tooth implants: a controlled clinical trial. International Journal of Oral and Maxillofacial Implants 20, 753-761. Schropp, L., Kostopoulos, L., Wenzel, A. & Isidor, F. (2005b) Clinical and radiographic performance of delayed-immediate single-tooth implant placement associated with peri-implant bone defects. A 2-year prospective, controlled, randomized follow-up report. Journal of Clinical Periodontology 32, 480-487. Schrotenboer, J., Tsao, Y.P., Kinariwala, V. & Wang, H.L. (2008) Effect of microthreads and platform switching on crestal bone stress levels: a finite element analysis. Journal of Periodontology 79, 2166-2172. Schwarz, F., Herten, M., Bieling, K. & Becker, J. (2008) Crestal bone changes at nonsubmerged implants (Camlog) with different machined collar lengths: a histomorphometric pilot study in dogs. International Journal of Oral and Maxillofacial Implants 23, 335-342. Shin, Y.K., Han, C.H., Heo, S.J., Kim, S. & Chun, H.J. (2006) Radiographic evaluation of marginal bone level around implants with different neck designs after 1 year. International Journal of Oral and Maxillofacial Implants 21, 789-794. Smeets, E.C., de Jong, K.J., Abraham-Inpijn, L. (1998) Detecting the medically compromised patient in dentistry by means of the medical risk-related history. A survey of 29,424 dental patients in The Netherlands. Preventive Medicine 27, 530-535. Stein, A.E., McGlmphy, E.A., Johnston, W.M. & Larsen, P.E. (2009) Effects of implant design and surface roughness on crestal bone and soft tissue levels in the esthetic zone. International Journal of Oral and Maxillofacial Implants 24, 910-919. Teughels, W., Van Assche, N., Sliepen, I. & Quirynen, M. (2006) Effect of material characteristics and/or surface topography on biofilm development. Clinical Oral Implants Research 17 Suppl 2, 68-81. Wohrle, P.S. (2003) Nobel Perfect esthetic scalloped implant: rationale for a new design. Clinical Implant Dentistry and Related Research 5 Suppl 1, 64-73. Wohrle, P.S. (2006) Commentary on “Scalloped dental implants: a retrospective analysis of radiographic and clinical outcomes of 17 NobelPerfect implants in 6 patients”. Clinical Implant Dentistry and Related Research 8, 54-58.

63

Implant neck designs

Lee, D.W., Choi, Y.S., Park, K.H., Kim, C.S. & Moon, I.S. (2007) Effect of microthread on the maintenance of marginal bone level: a 3-year prospective study. Clinical Oral Implants Research 18, 465-470.

3

4. Single-tooth implants with different neck designs in the aesthetic zone: a randomized clinical trial evaluating the aesthetic outcome

This is an edited version of the manuscript: Den Hartog, L., Raghoebar, G.M., Huddleston Slater, J.J., Stellingsma, K., Vissink, A., Meijer, H.J. Single-tooth implants in the aesthetic zone with different neck designs: a randomized clinical trial to the evaluating aesthetic outcome (submitted for publication, 2010).

Abstract Aim: To ���������������������������������������������������������������������� evaluate the aesthetic outcome of single-tooth implants in the aesthetic zone with different neck designs from a professional’s and patient’s perception.

Chapter

4

Material and Methods: 93 patients with a missing anterior tooth in the maxilla were randomly assigned to be treated with an implant with a smooth neck, a rough neck with grooves or a scalloped rough neck with grooves. Implants were installed in healed sites. One year after definitive crown placement, photographs were taken and the aesthetic outcome was assessed by professionals according to two objective aesthetic indexes (PES/WES and Implant Crown Aesthetic Index (ICAI)). A questionnaire was used to assess the aesthetic outcome and general satisfaction from a patient’s perception. Results: One implant was lost. There were no differences in aesthetic outcome between the implant neck designs. According to the professional’s assessment using PES/WES and ICAI, respectively 79.3% and 62% of the cases showed acceptable crown aesthetics and 59.8% and 56.5% acceptable mucosa aesthetics. Overall, patients were satisfied about the aesthetics of the mucosa (>80%) and crown (>93%) and general patient satisfaction was high (9.0 ± 1.0) out of a maximum of 10). The professional’s assessment revealed that a pre-implant augmentation procedure was associated with less favorable aesthetics of the mucosa. Conclusion: This study shows that the aesthetic outcome of single-tooth implants in the maxillary aesthetic zone appears to be independent on the implant neck designs applied, but dependent on the need for pre-implant surgery.

66

The focus of attention in contemporary implantology has shifted from implant survival towards the quality of implant survival. Particularly in the anterior region, the aesthetic outcome has been considered to be of significance for the overall treatment success (Den Hartog et al. 2008, Annibali et al. 2009, Belser et al. 2009). Both the appearance of the implant crown and the peri-implant mucosa contribute to the final aesthetic outcome (Meijer et al. 2005, Belser et al 2009). The level of the peri-implant mucosa is an important aspect determining the aesthetic outcome (Meijer et al. 2005, Belser et al 2009). The level of the peri-implant marginal bone has been associated with the level of the peri-implant mucosa (Bengazi et al. 1996, Hermann et al. 1997, Hermann et al. 2001). After implant placement, it is accepted that some peri-implant marginal bone loss will occur (Laurell et al. 2009). Hence, loss of peri-implant marginal bone might affect the level of the peri-implant mucosa and with that the final aesthetic outcome. The design of the implant neck is considered to be of relevance for preservation of marginal peri-implant bone (Hermann et al. 1997, Lee et al. 2007, Bratu et al. 2009). It has been reported that an implant neck with a roughened surface or with retention elements might result in less marginal peri-implant bone resorption than a traditional smooth implant neck. (Shin et al. 2006, Lee et al. 2007, Bratu et al. 2009) As a consequence, novel implant designs are often provided with a roughened surface and retention elements at the implant neck to induce maximum bone preservation, particularly when to be applied in aesthetically sensitive cases. Apart from the capacity of a rough implant neck to preserve marginal peri-implant bone, it has been suggested that an implant neck with a scalloped implant platform might preserve marginal peri-implant bone, particularly at the proximal side (Wohrle et al. 2003, Kan et al. 2007). Such a scalloped implant neck would mirror the alveolar ridge curvature, which is lower on the facial and oral aspects but rises in the proximal areas. As a consequence, a more non-violant position of the implant-abutment interface could be realised compared to common flat-platform implant designs. To assess the aesthetic outcome of implant therapy, both the opinion of the professional and patient have to be considered. From a professional’s perception, the aesthetic outcome should be explored using an objective rating instrument. Such an instrument will facilitate a thorough analysis of the final result to improve surgical or prosthetic treatment aspects. Furthermore, it can be of value to assess treatment strategies longitudinally or to identify host factors. Recently, two instruments have been introduced to measure the aesthetics of the crown and mucoca, namely The Implant Crown Aesthetic Index (ICAI) (Meijer et al. 2005) and the Pink Esthetic Sore/White Esthetic Score (PES/WES) (Belser et al. 2009). As the patient is the final user of implant therapy, the opinion of the patient 67

Implant neck designs

Introduction

4

is also of importance (Esposito et al., 2009). A method to assess the subjective aesthetic outcome from a patient’s perspective is the use of questionnaires (Levi et al. 2003, Schropp et al. 2004, Pjetursson et al. 2005). Inherent to the recent shift in implantology towards the quality of implant survival, only a few studies on implant therapy in the anterior dentition inquired into the aesthetic outcome (Den Hartog et al. 2008, Annibali et al. 2009). To our best knowledge, no clinical trials have yet been published addressing the aesthetic outcome of different implant neck designs. Furthermore, little is known about predisposing factors associated with the final aesthetic outcome. Therefore, the aim of this trial was to assess from a professionals and patient’s perception, the aesthetic outcome of anterior single-tooth implants with three different neck designs.

Material and Methods Chapter

4

Patients All patients with a single missing tooth in the maxillary aesthetic zone (incisor, canine or first premolar) who were referred for implant treatment to the department of Oral and Maxillofacial Surgery (University Medical Center Groningen, University of Groningen, Groningen, the Netherlands) were considered for inclusion. Patients had to be at least 18 years of age. The width of the diastema was at least 6 mm and was neighboured with natural teeth. Oral hygiene had to be adequate (modified plaque index and modified sulcus bleeding index scores ≤ 1 (Mombelli et al. 1987). Exclusion criteria were smoking, ASA score ≥ III, presence of an active periodontal disease as expressed by probing pocket depths ≥ 4 mm and bleeding on probing (index score > 1) and a history of radiotherapy to the head and neck region. Study design The study protocol of this prospective randomized clinical trial was approved by the Medical Ethical Committee of the University Medical Center Groningen and written informed consent was obtained from all eligible patients before enrolment. Patients were included between January 2005 and February 2008. By means of a specifically designed locked computer program, patients were randomly assigned to one of three study groups to be treated with an implant with - a 1.5 mm smooth (‘machined’) implant neck (Replace Select Tapered, Nobel Biocare AB, Göteborg, Sweden) – ‘smooth’ group; - a rough implant neck with grooves (NobelReplace Tapered Groovy, Nobel Biocare AB) – ‘rough’ group; - a scalloped rough implant neck with grooves (NobelPerfect Groovy, Nobel Biocare AB) – ‘scalloped’ group. 68

Intervention procedure Implants were inserted in healed sites at least three months after tooth removal. When bone volume was insufficient for implant placement, a bone augmentation procedure was carried out in a separate session. As a grafting material, autogenous intra-oral bone was used together with anorganic bovine bone (Geistlich Bio-Oss®, Geistlich Pharma AG, Wolhusen, Switzerland). Implants were inserted three months after the augmentation procedure. At implant surgery, a slightly palatal crest-incision with extensions through the buccal and palatal sulcus of the adjacent teeth and a divergent relieving incision at the distal tooth were made. A minimal mucoperiosteal flap was prepared to expose the alveolar ridge. The implant site was prepared by using a surgical template that was fabricated in the dental laboratory, based on the prospective implant crown in its ideal position. The shoulder of the implant was placed at a depth of 3 mm apical to the most apical aspect of the surgical template for optimal emergence profile. For the scalloped implants the mid-facial part of the implant shoulder was taken as reference. In all cases the alveolar bone was levelled to the implant neck. An implant dehiscence, fenestration or bone wall thickness 31 ≤ 60 years, > 60 years), location of the implant site (central or lateral incisor, canine or first premolar) and whether or not a pre-implant augmentation procedure in a separate session was indicated beforehand. The surgeon that inserted the implants was informed about the allocation on the day of surgery.

4

of a zirconia Procera coping (Nobel Biocare AB) or screw-retained by fusing porcelain directly to the abutment. Cemented-retained crowns were cemented with glass ionomer cement (Fuji Plus, GC Europe, Leuven, Belgium). In seven patients the contralateral tooth received a new all-ceramic zirconia crown (Procera) in the same procedure (two in the smooth group and rough group, three in the scalloped group). For more details regarding product specifications, we refer to a previous clinical report (Den Hartog et al. 2009). All surgical procedures were performed by a single experienced surgeon. The prosthetic procedure was accomplished by two experienced prosthodontists and all crowns were fabricated by one dental technician.

Chapter

4

Aesthetic assessment The aesthetic outcome was assessed on digital photographs that were taken one year after placement of the definitive crown (18 months after implant placement) (camera: Fuji-film FinePix S3 Pro). The implant and adjacent dentition were captured on one photograph which was centered at the midline. Of implants that replaced a lateral incisor, canine or first premolar, two additional photographs were taken on which the implant and contralateral tooth were centered. The Implant Crown Aesthetic Index (ICAI) (Meijer et al. 2005) and the Pink Esthetic Sore/White Esthetic Score (PES/WES) (Belser et al. 2009) were used to determine the aesthetics of the peri-implant mucosa and implant crown. Both indexes were used, to allow for comparison with data from other studies. Both indexes are composed of aesthetically related items based on the anatomic form, colour and surface characteristics of the implant crown and peri-implant soft tissue. The ICAI contains nine items, of which five related to the crown and four related to the peri-implant mucosa. For each item, penalty points of 0, 1 and 5 can be given representing respectively no, minor and major deviations compared to the contralateral tooth and adjacent dentition. The total score for crown and mucosa leads to the following corresponding judgement about the aesthetic outcome: 0 points, excellent; 1 or 2, satisfactory; 3 or 4, moderate; 5 or more, poor aesthetics (note: one item with a major deviation leads to poor aesthetics). In this study, the ICAI was slightly modified and has been used to analyze the aesthetics of the crown (ICAI crown) and the aesthetics of the mucosa (ICAI mucosa) separately. The PES/WES contains ten items, five for crown and mucosa each. In contrast to the ICAI, the PES/WES reward items with points instead of utilizing penalty points. Taking the contralateral tooth as a reference, on each item 0, 1, or 2 points can be assigned representing major, minor or no discrepancies respectively. The highest possible score for the crown (WES) and for the mucosa (PES) is 10. A threshold of clinical acceptability has been defined for the PES/WES, which is set at 6 points for the WES and 6 points for the PES. 70

Patient satisfaction Patient satisfaction was assessed using a self-administered questionnaire. The questionnaire comprized of four questions regarding patient’s aesthetic satisfaction with the colour and shape of the crown and mucosa. These questions could be answered on a 5-point rating scale ranging from ‘very dissatisfied’ (score 1) to ‘very satisfied’ (score 5). Furthermore, patients were asked to mark their general satisfaction on a 10 cm Visual Analogue Scale (VAS) having end phrases ‘very dissatisfied’ (0) on the left end and ‘very satisfied’ (10) on the right end. Data analysis ICAI crown scores, ICAI mucosa scores, PES scores and WES scores were analyzed separately. To assess the inter-observer agreement of both aesthetic evaluation instruments, linear weighted kappa (κ) values were calculated. Per patient, ICAI and PES/WES scores of both observers were averaged. For the ICAI, the average score was subsequently transposed to the corresponding judge (i.e. excellent, satisfactory, moderate, poor aesthetics). For between-group comparisons Kruskal-Wallis tests were used followed by post-hoc Mann-Whitney tests in case of statistical significance. To identify ������������� factors associated with the aesthetic outcome, regression analyses were performed. The following factors were explored: implant type, age, gender and whether or not a pre-implant augmentation procedure was performed. Correlations between the aesthetic outcome and patient’s aesthetic satisfaction were determined with Spearman’s correlation tests. In all analyses, a significant level of 0.05 was chosen. Data were analysed using the Statistical Package for Social Sciences (version 16.0, SPSS Inc, Chicago, USA).

Results Patients A total of 93 patients was included. Details regarding patient characteristics are depicted in Table 1. One implant in the smooth group was lost five months after implant placement. The implant survival rate at 18 months after implant placement was 96.8 % (1 implant lost) for the smooth group and 100% for the rough and scalloped study groups. All patients attended the follow-up visit at one year after definitive crown placement. 71

Implant neck designs

Measurements were done by two observers that were blinded to the group allocation. The intra-observer agreement of the ICAI and PES/WES has been shown to be acceptable in the studies in which these indexes were introduced (Meijer et al 2005, Belser et al. 2009).

4

Table 1.

Baseline characteristics per study group. Smooth group

Rough group

Scalloped group

(n=31)

(n=31)

(n=31)

37.2 ± 12.9 (18-60)

40.1 ± 14.4 (18-67)

40.1 ± 17.2 (19-80)

15/16

17/14

14/17

Implant site location I1 / I2 / C / P1

20 / 7 / 1 / 3

18 / 8 / 3 / 2

18 / 6 / 3 / 4

Augmentation before implant surgery*

12

11

10

Variable Mean age (years) ± standard deviation Range (years) Male/female ratio

*Implants were installed after three months.

Chapter

4 Aesthetic assessments The PES/WES showed a satisfactory inter-observer agreement. A weighted κ-value of 0.69 was calculated for the PES and a value of 0.62 for the WES. The ICAI showed satisfactory inter-observer agreement for the soft tissue assessment (κ-value 0.64), whereas moderate agreement was found for the assessment of the crown (κ-value 0.39). Because of this moderate agreement, the ICAI crown assessment was not used in the statistical analyses. There were no differences between study groups regarding the aesthetic outcome of the crown and peri-implant mucosa (Table 2). Furthermore, a per-item analysis of both indexes showed no differences between study groups. According to the PES/WES, in 59.8 % of the cases the mucosa showed acceptable aesthetics (PES-score ≥ 6) and in 79.3% of the cases the aesthetics of the crown were acceptable (WES-score ≥ 6). According to the ICAI, 56.5% of the cases showed satisfactory mucosa aesthetics (satisfactory and excellent) and 62% showed satisfactory crown aesthetics. For both indexes, the crown item ‘colour of the crown’ showed the lowest score and most penalty points. According to the WES, 69% of the crowns showed a discrepancy in colour and according to the ICAI this percentage was 68% (mean values of both observers). The soft tissue item ‘level of the facial mucosa’ showed the most penalty points of the ICAI (54 % on average showed deviation) and the second lowest score of the PES (61% on average showed deviation). The PES-item ‘root convexity, soft tissue colour and texture’ was assigned the lowest score (76% showed deviation). Multivariate linear regression analysis revealed that a pre-implant augmentation procedure was significantly associated with a lower PES score and ICAI mucosa score (regression coefficient respectively 1.27 and 0.55 for PES and ICAI). 72

Smooth (n=30)†

Rough (n=31)

Scalloped (n=31)

Overall (n=92)

PES Mean ± SD Range

6.0 ± 1.9 1.5 - 9.5

6.3 ± 1.7 3.5 - 9.5

6.6 ± 1.6 3.5 - 9

6.3 ± 1.7 1.5 - 9.5

WES Mean ± SD Range

7.2 ± 1.5 4.5 - 9.5

7.4 ± 1.6 4 - 10

7.2 ± 1.6 4.5 - 10

7.3 ± 1.5 4 - 10

ICAI Mucosa Excellent Satisfactory Moderate Poor

2 (6.7%) 14 (46.7%) 8 (26.7%) 6 (20%)

0 (0%) 15 (48.4%) 6 (19.4%) 10 (32.3%)

0 (0%) 21 (67.7%) 4 (12.9%) 6 (19.4%)

2 (2.2%) 50 (54.3%) 18 (19.6%) 22 (23.9%)

ICAI Crown Excellent Satisfactory Moderate Poor

1 (3.3%) 17 (56.7%) 10 (33.3%) 2 (6.7%)

1 (3.2%) 18 (58.1%) 10 (32.3%) 2 (6.5%)

1 (3.2%) 19 (61.3%) 7 (22.6%) 4 (12.9%)

3 (3.3%) 54 (58.7%) 27 (29.3%) 8 (8.7%)

One implant was lost. Abbreviations: SD=Standard deviation, PES=Pink Esthetic Score, WES=White Esthetic Score, ICAI=Implant Crown Aesthetic Index.



The factor age contributed significantly to the outcome of WES (regression coefficient -0.048), whereas implant type and gender were not associated with the aesthetic outcome.

Patient satisfaction Patient satisfaction was high (Table 3) and there were no between-group differences. General patient satisfaction scores using VAS ranged from 5.5 to 10. Patient’s aesthetic satisfaction with the appearance of the mucosa (colour and shape) was correlated with the outcome of PES. The outcome of all questions was correlated with general patient satisfaction.

Discussion This clinical trial assessed the aesthetic outcome of single-tooth implants in the anterior dentition with three different neck designs as an independent factor, 73

Implant neck designs

Table 2. PES, WES, ICAI mucosa and ICAI crown scores per study group and for the whole study population.

4

Table 3. Patient satisfaction per study group and for the whole study population. Number of patients being satisfied (%)* Smooth (n=30)†

Rough (n=31)

Scalloped (n=31)

Overall

Colour of the crown

28 (93.3%)

30 (96.8%)

28 (90.0%)

86 (93.3%)

Form of the crown

28 (93.3%)

31 (100%)

29 (93.5%)

88 (95.7%)

Colour of the mucosa around the implant

26 (86.7%)

27 (87.1%)

26 (83.9%)

79 (85.9%)

Form of the mucosa around the implant

24 (80.0%)

27 (87.1%)

24 (77.4%)

75 (81.5%)

8.8 ± 1.1

8.9 ± 1.0

9.1 ± 0.8

9.0 ± 1.0

General patient satisfaction (VAS-score; mean ± SD)

4

*Measured on 5-point scale (4 or 5 equals satisfied and very satisfied respectively) One implant was lost. Abbreviations: SD=standard deviation, VAS=visual analogue scale.

Chapter



using two established indexes for rating the objective aesthetic outcome and a questionnaire to subjectively evaluate the aesthetics from the patient’s perception. No differences were observed between the aesthetic outcome of the three implant neck designs included in this trial. Patient satisfaction was high and it revealed that there was a discrepancy between the patient’s aesthetic satisfaction and the objective aesthetic outcome according to the indexes. With regard to the aesthetic outcome of the peri-implant mucosa, no differences were notified between the three implant neck designs. Furthermore, none of the separate soft tissue items showed differences between the study groups. Beforehand, we hypothesized that the design of the implant neck might have an effect on the level of the peri-implant mucosa. However, using both indexes, such an effect could not be shown in our study. One reason for this might be that the difference in marginal bone resorption between the scalloped group and the other study groups brought about a clinical effect that was too little to be observed with the aesthetic indexes we applied (See Chapter 3 for more details regarding marginal bone loss). A second reason might be attributed to the role of the periodontium of the adjacent teeth. It is assumed that the bone level next to the adjacent teeth is highly related to at least the future level of the papillae (Choquet et al. 2001, Romeo et al. 2008). Possibly, the periodontium also acts on other aesthetically related aspects as the level of the facial mucosa. The aesthetic assessment of the crown did not reveal differences between 74

75

Implant neck designs

study groups. We believe that the implant neck designs we investigated are of less importance for the final crown aesthetics. Implants in the study groups were restored according to the same procedure. The only difference was that for the implants in the scalloped group, titanium abutments had to be used instead of zirconia abutments in the smooth and rough group. However, the titanium abutments were modified by means of a zirconia layer. Besides, all crowns in this study were all-ceramic. As a result from the recent introduction of the PES/WES and ICAI, published studies using these indexes for aesthetic evaluation are scarce. Only two studies could be identified that reported the aesthetic outcome of anterior single-tooth replacements using the PES/WES (Belser et al. 2009, Buser et al. 2009) and only one study using the ICAI (Meijndert et al. 2007). To our best knowledge, these are the only available instruments to rate the aesthetics of both crown and mucosa. In the first study on the PES/WES (Belser et al. 2009), the reproducibility of this index was analyzed on the basis of 45 maxillary single-tooth implants installed according to an early implant placement procedure. A mean PES-score of 7.7 ± 1.3 was reported and no implant scored lower than 6 points, the predefined level of clinical acceptability. In a second study from the same research group (Buser et al. 2009), a PES-score of 8.1 ± 1.75 was reported for 20 early placed implants and only one case showed less than 6 points. In our study, the aesthetics of the mucosa were judged with a mean score of 6.3 and 40.2 % of the cases scored less than 6 points, thus were clinical unacceptable. Most likely, a less favorable preoperative situation was the underlying factor for these lower PES-scores. In our study, all implants were inserted in healed extraction sites and teeth had already been extracted at the first consultation without having opportunities to perform socket preservation techniques. It is known that after tooth removal, the walls of the alveolus undergo substantial resorption at the facial aspect, affecting the soft tissue anatomy (Schropp et al. 2003, Araujo & Lindhe 2005). Early implant placement and simultaneous guided bone regeneration according to which the implants in the abovementioned studies were inserted, might favor the facial soft tissue anatomy. For instance, it was demonstrated in these studies that the level of the contralateral reference tooth was identical in 77.8 % (35 of 45) (Belser et al. 2009) and 90% (18 of 20) (Buser et al. 2009) of the cases. In our study however, this item showed the second lowest score of all items and in 36 of 92 patients (39%) the level of the mucosa was identical. The less favorable preoperative situation in our study is also reflected in the frequency of pre-implant augmentation procedures, necessary to allow for proper implant installation three months later. In our study, a pre-implant augmentation procedure was needed in one-third of the patients and the regression analysis showed that this procedure was significantly associated with a lower PES-score. A

4

Chapter

4

study to the aesthetic outcome of anterior single-tooth implants installed after a separate augmentation procedure, confirmed the negative effect of a pre-implant placement augmentation procedure on the appearance of the mucosa (Meijndert et al. 2007). With regard to the assessments of the implant crown, in the study by Belser et al. (2009) crowns were judged with a mean WES-score of 6.9 ± 1.5 which is in line with the score of 7.3 ± 1.5 as we observed. However, in the other study from the same research group, the mean WES-score was 8.7 ± 1.0. It was argued that this higher WES-score could be explained by the fact that only one dental technician was involved having excellent expertise in the field of esthetic restorations versus multiple joining technicians in the other study. Compared to our study, this difference in white aesthetics might be explained from the fact that in our study the contralateral tooth received a new crown less frequently (in the study by Buser et al. (2009), 5 of 20 contralateral teeth received a new crown, in our study 7 of 92). Since the contralateral tooth serves as a reference tooth in assessing the white aesthetics, it is easier to reach a higher aesthetic judge when these teeth are provided with a new crown too, particularly on the variables colour, translucency and texture. Furthermore, it should be realized that the less favorable pink aesthetics we observed, could affect the outcome of the white aesthetics. Less voluminous papillae for instance or an undercontoured alveolar process might be compensated by overcontouring the anatomy of the crown. Regarding the colour of the crown, this will remain a challenging item to fulfil without any discrepancy. In our study and in the study by Buser et al. (2009), this item showed the lowest appreciation. It should be realized however that the aesthetics were assessed on photographs. It might be that in a direct assessment of the patient, the colour of the crown shows more favorable resemblance with the adjacent dentition. As was expected from other studies, patient satisfaction was high (Schropp et al. 2004, Pjetursson et al. 2005, Den Hartog et al. 2008). Although the outcome of PES was correlated to patient satisfaction with the appearance of the mucosa, most of the patients were satisfied with the appearance of the mucosa (> 80%) and even more patients were satisfied with the appearance of the crown (> 93%). This discrepancy between the aesthetic outcome from a professional’s and patient’s perception, has been demonstrated in earlier studies (Chang et al. 1999, Meijndert et al. 2007, Esposito et al 2009). This difference might be explained by the finding that factors considered by professionals to be relevant for the esthetic outcome may not be of decisive importance for patient’s aesthetic satisfaction. (Chang et al. 1999) Furthermore, it might be that for the final appreciation of the patient, the pre-operative situation plays a role of significance and gives weight to the final judgment. When the pre-operative situation is compromized and patient’s expectations are realistic, patients might ������������������������������������� be satisfied even when the aes76

77

Implant neck designs

thetic outcome according to an objective index is poor. The aesthetic indexes do not take the preoperative situation into account. With respect to the reproducibility of the ICAI, controversial degrees of intra- and interobserver agreement have been reported. At the introduction of the ICAI, two prosthodontists showed acceptable intra- and interobserver agreement. Gehrke et al. (Gehrke et al. 2009), however, reported poor to moderate reliability for the ICAI when applied by different professionals including prosthodontists. In our study, the ICAI was slightly modified and was used to generate a separate judgment for the crown and mucosa instead of an overall judgement. It was found that the reliability of the mucosa assessment was acceptable and of the crown assessment was moderate. Apparently, the crown is more prone to disagreement than the mucosa. We believe that this moderate reproducibility might be caused by the scoring system of the ICAI and the corresponding final judgement. Namely, when an item deviates majorly in the observer’s eyes, the aesthetics will be judged automatically as being poor. However, when this deviation is minor according to another observer, large differences in final judgment will occur. Furthermore, the ICAI is based on comparing the implant crown with the contralateral tooth and the adjacent dentition as well. This might lead to more variation in observer interpretation. Since the PES/WES applies a different scoring system and the contralateral tooth is the only reference, this index might be less sensitive for disagreement and subsequently showed higher reliability. However, this might also lead to shortcomings, since a major discrepancy on an item yet might lead to acceptable aesthetics and in some cases it would be more plausible to involve the adjacent dentition in the analyses as well (for instance when the contralateral tooth shows compromised aesthetics). More studies would be helpful to further develop a reproducible and valid aesthetic index, which should be commonly applied in implant research. This study shows that at one year after definitive crown placement, there are no differences in aesthetic outcome between the different implant necks of single-tooth implants applied in the aesthetic zone. According to the most reproducible index (the PES/WES), the peri-implant mucosa was judged as being not acceptable in 40% of the cases whereas 20% of the implant crowns were not acceptable. However, patient’s aesthetic satisfaction regarding colour and shape of crown and mucosa was high. It should be realized that in this study all implants were installed in healed sites, at least three months after extraction and one third of the cases had to be augmented before implant placement. Since we found that a pre-implant augmentation procedure has a detrimental effect on the objective aesthetic outcome (using PES/WES), this underlines the need to prevent a separate augmentation procedures, possibly by extracting hopeless teeth in an earlier stage or by performing socket preservation techniques.

4

References

Agreement of quantitative subjective evaluation of esthetic changes in implant dentistry by patients and practitioners. International Journal of Oral and Maxillofacial Implants 24, 309-315.

Annibali, S., Bignozzi, I., La Monaca, G. & Cristalli, M.P. (2009) Usefulness of the Aesthetic Result as a Success Criterion for Implant Therapy: A Review. Clinical Implant Dentistry and Related Research Araujo, M.G. & Lindhe, J. (2005) Dimensional ridge alterations following tooth extraction. An experimental study in the dog. Journal of Clinical Periodontology. 32, 212-218. Belser, U.C., Grutter, L., Vailati, F., Bornstein, M.M., Weber, H.P. & Buser, D. (2009) Outcome evaluation of early placed maxillary anterior single-tooth implants using objective esthetic criteria: a cross-sectional, retrospective study in 45 patients with a 2- to 4-year follow-up using pink and white esthetic scores. Journal of Periodontology 80, 140-151.

Chapter

4

Bengazi, F., Wennstrom, J.L. & Lekholm, U. (1996) Recession of the soft tissue margin at oral implants. A 2-year longitudinal prospective study. Clinical Oral Implants Research 7, 303-310. Bratu, E.A., Tandlich, M. & Shapira, L. (2009) A rough surface implant neck with microthreads reduces the amount of marginal bone loss: a prospective clinical study. Clinical Oral Implants Research 20, 827-832. Buser, D., Halbritter, S., Hart, C., Bornstein, M.M., Grutter, L., Chappuis, V. & Belser, U.C. (2009) Early implant placement with simultaneous guided bone regeneration following single-tooth extraction in the esthetic zone: 12-month results of a prospective study with 20 consecutive patients. Journal of Periodontology 80, 152-162. Chang, M., Odman, P.A., Wennstrom, J.L. & Andersson, B. (1999) Esthetic outcome of implant-supported single-tooth replacements assessed by the patient and by prosthodontists. International Journal of Prosthodontics 12, 335-341. Choquet, V., Hermans, M., Adriaenssens, P., Daelemans, P., Tarnow, D.P. & Malevez, C. (2001) Clinical and radiographic evaluation of the papilla level adjacent to single-tooth dental implants. A retrospective study in the maxillary anterior region. Journal of Periodontology 72, 1364-1371. Den Hartog, L., Raghoebar, G.M., Stellingsma, K. & Meijer, H.J. (2009) Immediate loading and customized restoration of a single implant in the maxillary esthetic zone: a clinical report. Journal of Prosthetic Dentistry 102, 211-215. Den Hartog, L., Slater, J.J., Vissink, A., Meijer, H.J. & Raghoebar, G.M. (2008) Treatment outcome of immediate, early and conventional single-tooth implants in the aesthetic zone: a systematic review to survival, bone level, soft tissue, aesthetics and patient satisfaction. Journal of Clinical Periodontology 35, 1073-1086. Esposito, M., Grusovin, M.G. & Worthington, H.V. (2009)

78

Gehrke, P., Degidi, M., Lulay-Saad, Z. & Dhom, G. (2009) Reproducibility of the implant crown aesthetic index--rating aesthetics of single-implant crowns and adjacent soft tissues with regard to observer dental specialization. Clinical Implant Dentistry and Related Research 11, 201-213. Hermann, J.S., Buser, D., Schenk, R.K., Schoolfield, J.D. & Cochran, D.L. (2001) Biologic Width around one- and two-piece titanium implants. Clinical Oral Implants Research 12, 559-571. Hermann, J.S., Cochran, D.L., Nummikoski, P.V. & Buser, D. (1997) Crestal bone changes around titanium implants. A radiographic evaluation of unloaded nonsubmerged and submerged implants in the canine mandible. Journal of Periodontology 68, 1117-1130. Kielbassa, A.M., Martinez-de Fuentes, R., Goldstein, M., Arnhart, C., Barlattani, A., Jackowski, J., Knauf, M., Lorenzoni, M., Maiorana, C., Mericske-Stern, R., Rompen, E. & Sanz, M. (2009) Randomized controlled trial comparing a variablethread novel tapered and a standard tapered implant: interim one-year results. Journal of Prosthetic Dentistry 101, 293-305. Laurell, L. & Lundgren, D. (2009) Marginal Bone Level Changes at Dental Implants after 5 Years in Function: A Meta-Analysis. Clinical Implant Dentistry and Related Research Lee, D.W., Choi, Y.S., Park, K.H., Kim, C.S. & Moon, I.S. (2007) Effect of microthread on the maintenance of marginal bone level: a 3-year prospective study. Clinical Oral Implants Research 18, 465-470. Levi, A., Psoter, W.J., Agar, J.R., Reisine, S.T. & Taylor, T.D. (2003) Patient self-reported satisfaction with maxillary anterior dental implant treatment. International Journal of Oral and Maxillofacical Implants 18, 113-120. Meijer, H.J., Stellingsma, K., Meijndert, L. & Raghoebar, G.M. (2005) A new index for rating aesthetics of implantsupported single crowns and adjacent soft tissues--the Implant Crown Aesthetic Index. Clinical Oral Implants Research 16, 645-649. Meijndert, L., Meijer, H.J., Stellingsma, K., Stegenga, B. & Raghoebar, G.M. (2007) Evaluation of aesthetics of implantsupported single-tooth replacements using different bone augmentation procedures: a prospective randomized clinical study. Clinical Oral Implants Research 18, 715-719. Mombelli, A., van Oosten, M.A., Schurch E Jr & Land, N.P. (1987) The microbiota associated with successful or failing osseointegrated titanium implants. Oral Microbiology and Immunology 2, 145-151.

Pjetursson, B.E., Karoussis, I., Burgin, W., Bragger, U. & Lang, N.P. (2005) Patients’ satisfaction following implant therapy. A 10-year prospective cohort study. Clinical Oral Implants Research 16, 185-193. Romeo, E., Lops, D., Rossi, A., Storelli, S., Rozza, R. & Chiapasco, M. (2008) Surgical and prosthetic management of interproximal region with single-implant restorations: 1-year prospective study. Journal of Periodontology 79, 1048-1055.

Implant neck designs

Schropp, L., Isidor, F., Kostopoulos, L. & Wenzel, A. (2004) Patient experience of, and satisfaction with, delayed-immediate vs. delayed single-tooth implant placement. Clinical Oral Implants Research 15, 498-503. Schropp, L., Wenzel, A., Kostopoulos, L. & Karring, T. (2003) Bone healing and soft tissue contour changes following single-tooth extraction: a clinical and radiographic 12month prospective study. International Journal of Periodontics and Restorative Dentistry 23, 313-323.

4

Shin, Y.K., Han, C.H., Heo, S.J., Kim, S. & Chun, H.J. (2006) Radiographic evaluation of marginal bone level around implants with different neck designs after 1 year. International Journal of Oral and Maxillofacical Implants 21, 789-794. Wohrle, P.S. (2003) Nobel Perfect esthetic scalloped implant: rationale for a new design. Clinical Implant Dentistry and Related Research 5 Suppl 1, 64-73.

79

5. Immediate loading of single-tooth implants in the aesthetic zone: a randomized clinical trial

This is an edited version of the manuscript: Den Hartog, L., Raghoebar, G.M., Stellingsma, K., Vissink, A., Meijer, H.J. Immediate loading of single implants in the aesthetic zone: a randomized clinical trial. Journal of Clinical Periodontology (accepted for publication, 2010)

Abstract Aim: To compare the outcome of immediate loading with conventional loading for single-tooth implants in the maxillary aesthetic zone. It was hypothesized that immediate loading is not inferior to conventional loading.

Chapter

5

Materials and Methods: 62 patients with a missing maxillary anterior tooth were randomly assigned to be treated with an implant that was either restored with a non-occluding temporary crown within 24 hours after implant placement (‘immediate group’) or was restored according to a two-stage procedure after three months (‘conventional group’). All implants were installed in healed sites. Follow-up visits were conducted after 6 and 18 months post-implant placement. Outcome measures were radiographic marginal bone level changes, survival, soft tissue aspects (probing depth, plaque, bleeding, soft tissue level), aesthetics and patient satisfaction. Results: No significant differences were found between both study groups regarding marginal bone loss (immediate group 0.91±0.61 mm, conventional group 0.90±0.57 mm), survival (immediate group 96.8%: 1 implant lost, conventional group 100%), soft tissue aspects, aesthetic outcome and patient satisfaction. Conclusion: Within the limitations of this study (sample size, follow-up duration) it can be concluded that, for single-tooth implants in the anterior maxilla, the outcome of immediate loading is not less favorable than conventional loading.

82

Dental implants are commonly applied to replace missing teeth. Traditionally, implants were subjected to a load-free healing period of several months, allowing the implant to osseointegrate without being exposed to external forces. Over the last years, the concept of immediate loading has gained attention. This concept is defined as the application of a load by means of a restoration within 48 hours after implant placement (Laney 2007). Patients with a missing anterior tooth may benefit from immediate loading. Placement of the (provisional) implant crown immediately after implant placement reduces overall treatment time, avoids a second-stage operation and offers immediate comfort as there is no need for a provisional removable prosthesis during the healing phase. Besides the beneficial effects of immediate loading, this concept has also some inherent thought disadvantages. E.g., immediate loading might induce micromotion and instability of the implant (Gapski et al. 2003, Trisi et al. 2009). Implant instability might result in fibrous encapsulation of the implant and failing osseointegration (Lioubavina-Hack et al. 2006). Albeit yet applied on implants placed in mandibles to support bridges or bar-retained overdentures (Esposito et al. 2009), immediate loading of maxillary single-tooth implants might involve more risk. The quality of bone is poorer in the maxilla than in the mandible in the context of achieving primary implant stability (Mesa et al. 2008, Trisi et al. 2009, Roze et al. 2009). Thus implants in this region might be more susceptible to micromotion. Furthermore, force distribution to other implants by splinting is not possible for single-tooth implants. In contrast to the mandible, well-designed clinical trials on immediate loading of single-tooth implants in the anterior maxilla are scarce (Den Hartog et al. 2008, Esposito et al. 2009, Grutter & Belser 2009) and there is limited evidence regarding the effect of immediate loading on peri-implant marginal bone and soft tissue responses (Glauser et al. 2006, Den Hartog et al. 2008, Grutter & Belser 2009). Therefore, the aim of this study was to compare the outcome of immediate loading with that of conventional loading of implants applied for a missing anterior maxillary tooth. It was hypothesized that immediate loading is not inferior to conventional loading.

Material and Methods Patients Patients referred to the department of Oral and Maxillofacial Surgery (University Medical Center Groningen, University of Groningen, Groningen, the Netherlands) for anterior single implant treatment were considered for inclusion 83

Immediate loading

Introduction

5

Chapter

5

if they fulfilled the following criteria: - at least 18 years of age; - one missing tooth being an incisor, canine or first premolar in the maxilla with adjacent natural teeth; - adequate oral hygiene, i.e. modified plaque index score and modified sulcus bleeding index score ≤ 1 (Mombelli et al. 1987); - mesial-distal width of diastema at least 6 mm; - vertical occlusal dimensions allow for creation of a non-occluding provisional crown. Exclusion criteria were: - ASA score ≥ III (Smeets et al. 1998); - presence of active clinical periodontal disease������������������������������ as expressed by probing pocket depths ≥ 4 mm and bleeding on probing; - presence of peri-apical lesions or any other abnormalities in the maxillary anterior region as determined on a radiograph; - smoking; - a history of radiotherapy to the head and neck region.

Study design This randomized clinical trial was approved by the ethics committee of the University Medical Center Groningen. A written informed consent was obtained from patients before enrollment. Patients were included between January 2005 and February 2008. A specifically designed locked computer software program was used to randomly assign patients to one of two study groups to receive an implant with an anodized surface (NobelReplace Tapered Groovy, Nobel Biocare AB, Göteborg, Sweden) that was either restored within 24 hours after implant placement (‘immediate group’) or was restored according to a two-stage procedure after three months of healing (‘conventional group’).������������������������������������ Randomization by minimization (Altman 1991) was used to balance possible prognostic variables between the treatment groups. Minimization was used for the variables age (≤30 years, >31 ≤ 60 years, > 60 years), location of the implant site (central or lateral incisor, canine or first premolar) and whether or not a pre-implant augmentation procedure was indicated based on a clinical and diagnostic cast assessment. The allocation result was kept in a locked computer file that was not accessible for the examiner and the practitioners. The surgeon that inserted the implants was informed about the allocation on the day of surgery. Interventions All implants were placed in healed sites at least three months after tooth remov84

85

Immediate loading

al, allowing the extraction site to heal. When bone volume was insufficient for implant insertion, a bone augmentation procedure was carried out. As a grafting material, autogenous bone was used together with anorganic bovine bone (Geistlich Bio-Oss®, Geistlich Pharma AG, Wolhusen, Switzerland) covered with a Geistlich Bio-Gide® membrane (Geistlich Pharma AG). Implants were inserted three months after the augmentation procedure. Implants were placed and restored according to the protocol as described in detail in a previous clinical report (Den Hartog et al. 2009). Briefly, a surgical template was used to install the implants at a depth of 3 mm apical to the buccal and cervical aspect of the prospective clinical crown. All implants were installed with a torque controller (OsseoCare, Nobel Biocare AB) adjusted to an insertion torque of 45 Ncm. A manual torque controller (Nobel Biocare AB) was used to realize proper implant depth if this torque value was reached before the implant had reached its planned position. In the immediate group, an implant-level impression was made. A healing abutment was connected to the implants in the immediate group and a cover screw to the implants in the conventional group. Before wound closure and if necessary, in both study groups implant dehiscences or fenestrations were covered with autogenous bone chips collected during implant bed preparation and anorganic bovine bone (Geistlich Bio-Oss®) overlaid with Geistlich Bio-Gide®. Within 24 hours, a screw-retained provisional crown was placed in the immediate group. This crown was free from centric and eccentric contacts with the antagonist teeth. Patients were instructed to follow a soft diet and to avoid exerting force on the provisional restoration. Patients in the conventional group were wearing a removable partial prosthesis that did not interfere with the wound. These implants were uncovered after three months and restored with a provisional crown according to the same procedure as in the immediate group. After a provisional phase of three months for the conventional group and six months for the immediate group (to allow for six months post-implant placement for both study groups), a definitive crown was made consisting of an individually fabricated zirconia abutment (Procera, Nobel Biocare AB). Depending on the location of the screw access hole, crowns were either screw-retained by fusing porcelain directly to the abutment or cement-retained by means of a zirconia Procera coping (Nobel Biocare AB). Cemented-retained crowns were cemented with glass ionomer cement (Fuji Plus cement, GC Europe, Leuven, Belgium). All surgical procedures were performed by a single experienced oral and maxillofacial surgeon. The prosthetic procedure was accomplished by two experienced prosthodontists, and all crowns were fabricated by one dental technician.

5

Outcome measures The primary outcome measure of this study was marginal bone level change proximal to the implant 18 months after implant placement as measured on radiographs. Secondary outcome measures were implant survival, change in peri-implant mucosal level, aesthetic outcome, papilla volume, amount of plaque, bleeding after probing, probing pocket depth and patient satisfaction. Both the implant and adjacent teeth were analyzed. The operationalization of variables is described below.

Chapter

5

Radiographic and photographic assessments After implant placement (baseline, T0), and after 6 (T6m, after definitive crown placement) and 18 months (T18m), standardized digital intra-oral radiographs were taken with a long-cone paralleling technique. Standardized digital photographs (camera: Fuji-film FinePix S3 Pro) were gathered before implant placement (Tpre) and at T6m and T18m. The radiographic and photographic procedure has been described in detail by Meijndert et al. (Meijndert et al. 2004). For calibration of the photographs, a calibrated probe was held in close contact and parallel to the long axis of a tooth adjacent to the implant. All measurements were done by one and the same examiner. The examiner was blinded for the photographs and the radiographs taken at T6m and T18m. The radiographic examination could not be blinded for the radiographs collected after implant placement (baseline, T0), since the study group could be deduced from these radiographs. Full-screen analysis of the radiographs was performed using specifically designed software. Radiographs were calibrated according to the known diameter of the implant. Reference points were marked and marginal bone levels proximal to the implant were measured according to the first bone-to-implant contact together with marginal bone levels of the adjacent teeth (Figure 1). Full-screen analysis of the photographs was performed using Adobe Photoshop (Adobe Photoshop CS3 Extended, Adobe Systems Inc., San Jose, USA). After calibration, mid-facial mucosal and papilla levels of the implant were measured after definitive crown placement (from T6m). Mid-facial gingival levels of the adjacent teeth were measured from Tpre. The incisal edges of the implant crown and adjacent teeth were used as reference.

86

Immediate loading

Figure 1. Schematic drawing of the radiographic assessment.

5 A and B, distances from reference line to marginal bone levels of implant and adjacent teeth. Abbreviations: ref=reference line.

To assess the reliability of the radiographic and photographic examination, 30 radiographs and photographs (15 from each study group) were randomly selected and were measured by two examiners and by one examiner twice with a two-week interval. The intra-observer agreement of the photographic examination was tested earlier and reported as good with a mean difference of 0.11 ± 0.02 mm between both times of measurements (Meijndert et al. 2004).

Clinical assessments At Tpre (before implant placement), T6m and T18m patients were seen for clinical data collection. Both the implant and the adjacent teeth were analyzed at the facial aspect. All data were retrieved by one and the same examiner. Variables were: plaque, using the modified plaque index (Mombelli et al. 1987), bleeding, using the modified sulcus bleeding index (Mombelli et al. 1987), volume of the interproximal papilla, using the papilla index (Jemt 1997) and probing pocket depth, measured to the nearest 1 mm using a manual periodontal probe (Williams Color-Coded Probe������������������������������������������������������������������������� , Hu-Friedy, Chicago, USA). During follow-up, implant survival was registered (defined as the existence of an implant in the oral cavity (Laney 2007). Aesthetic assessments The aesthetics of the peri-implant mucosa and implant crown were determined on photographs taken at T18m by using the Implant Crown Aesthetic Index (ICAI) 87

(Meijer et al. 2005) and the Pink Esthetic Score-White Esthetic Score (PES/WES) (Belser et al. 2009). Measurements were done by one observer who was blinded for the group allocation. The inter-observer reliability was assessed according to 10 randomly selected photographs from each study group (20 in total) that were judged by two observers and by one observer with a two-week interval. The intraobserver reliability has been reported as acceptable in earlier studies (Meijer et al. 2005, Belser et al. 2009).

Chapter

5

Patient satisfaction Patient satisfaction was assessed using a self-administered questionnaire to be completed at T6m and T18m. The questionnaire comprised of questions or statements that could be answered on a 5-point rating scale ranging from ‘very dissatisfied’ and ‘not in agreement’ (score 1) to ‘very satisfied’ and ‘in agreement’ (score 5). Topics were aesthetics, function and treatment procedure. Furthermore, patients were asked to mark their overall satisfaction on a 10 cm Visual Analogue Scale (VAS) having end phrases ‘very dissatisfied’ (0) on the left end and ‘very satisfied’ (10) on the right end. Data analysis A non-inferiority analysis was used to compare immediate loading with conventional loading. Non-inferiority of immediate to conventional loading was defined as less than 0.5 mm mean marginal bone loss (both proximal sides combined). It was assumed that a mean marginal bone loss of 1.0 ± 0.6 mm would occur from implant placement to 18 months thereafter for implants restored according to a conventional protocol (Den Hartog et al. 2008). With a one-sided significance level of 5% and a power of 90%, a minimum of 26 patients per group was required. The number of patients per group was set at 31 to deal with withdrawal. The intra-and interobserver agreement for the radiographic and photographic assessments were expressed as the 95% limits of agreement (Altman 1991), representing the interval containing 95% of the differences between the observations to be compared. In addition, intraclass correlation coefficients were calculated for continuous variables and linear weighted kappa (κ) for categorical variables. For between-group comparisons of numeric and normally distributed variables (assessed using Kolmogorov-Smirnov test), t-tests were used. Variables that were not normally distributed were statistically explored with Mann-Whitney tests. Friedman tests were applied for several within-group comparisons and Wilcoxon signed-rank tests to compare two dependant conditions. In all analyses, a significant level of 0.05 was chosen. Data were analysed using the Statistical Package for Social Sciences (version 16.0, SPSS Inc, Chicago, IL, USA). 88

Results A total of 62 patients were allocated to the study groups of this trial (Table 1). Most of the teeth that were lost had a history of trauma. All implants were placed with a minimum insertion torque of 45 Ncm. Details about the surgical and prosthetic procedures are depicted in Table 1. There were no drop-outs and all patients attended the follow-up visits.

Immediate loading (n=31)

Conventional loading (n=31)

38.4 ± 14.0 18 - 66

40.1 ± 14.4 18 - 67

Immediate loading

Table 1. Baseline characteristics and treatment specifications of 62 patients treated with an immediate or conventional implant procedure.

Male/female ratio

9 / 22

17/14

5

Tooth gap position I1 / I2 / C / P1

14 / 10 / 4 / 3

18 / 8 / 3 / 2

22 6 1 2 9

15 4 8 2 2 11

10 21

10 21

4 27

2 29

2.16 ± 0.66 0.54 – 4.37

2.17 ± 0.77 0.45 – 5.26

12 18

12 19

Variable Mean age Range (years)

Cause of tooth absence Fracture (crown or root) Agenesis Endodontic failure Periodontal failure Root resorption Augmentation before implant surgery* Implant diameter 3.5 mm 4.3 mm Implant length 13 mm 16 mm Implant-tooth distance Mean ± SD (mm) Range Final restoration Screw-retained Cement-retained *Implants were installed after three months. Abbreviations: SD = standard deviation.

Reliability of radiographic and photographic assessments For the intra-observer agreement of the radiographic examination, the mean difference between the observations was 0.03 ± 0.23 mm (limits of agreement: -0.43 mm and 0.49 mm). For the inter-observer agreement, the mean difference 89

Marginal soft tissue level changes (mm) Mesial implant papilla Distal implant papilla Mid-facial of implant Mesial tooth Distal tooth

Implant bone loss (%)‡ ≤1 mm 1-2 mm ≥2 mm

Marginal bone level changes (mm) Mesial of implant Distal of implant Mesial tooth side Distal tooth side

-0.20 ± 0.38 -0.41 ± 0.52

71.6 25 3.3

-0.73 ± 0.54 -0.75 ± 0.68 -0.20 ± 0.39 -0.26 ± 0.47

Imm. (n=30)#

-0.13 ± 0.39 -0.33 ± 0.51

62.9 33.9 3.2

-0.79 ± 0.62 -0.81 ± 0.76 -0.25 ± 0.38 -0.18 ± 0.34

Conv. (n=31)

Baseline* -T6m

0.41 ± 0.49 0.27 ± 0.49 0.06 ± 0.42 -0.04 ± 0.23 0.10 ± 0.30

96.7 1.7 1.7

-0.13 ± 0.55 -0.19 ± 0.35 -0.02 ± 0.22 0.02 ± 0.45

Imm. (n=30)#

T6m- T18m

0.19 ± 0.29 0.35 ± 0.52 -0.09 ± 0.34 -0.09 ± 0.25 0.00 ± 0.30

100 0 0

-0.13 ± 0.40 -0.09 ± 0.41 0.03 ± 0.28 -0.03 ± 0.42

Conv. (n=31)

-0.25 ± 0.42 -0.32 ± 0.51

63.3 30 6.7

-0.87 ± 0.55 -0.95 ± 0.84 -0.22 ± 0.38 -0.24 ± 0.40

Imm. (n=30)#

-0.22 ± 0.36 -0.33 ± 0.36

56.5 38.7 4.8

-0.91 ± 0.66 -0.90 ± 0.77 -0.17 ± 0.40 -0.29 ± 0.50

Conv. (n=31)

Baseline*- T18m

Table 2. Changes in marginal bone level and marginal soft tissue level at implant and tooth sides from baseline to 18 months

Baseline*

2.03 ± 0.44 1.35 ± 0.37

Imm.

2.03 ± 0.51 1.37 ± 0.39

Conv. 3.07 ± 0.91 3.37 ± 0.93 2.78 ± 0.58 1.81 ± 0.45 1.45 ± 0.70

Imm.

T6m

3.03 ± 0.89 3.50 ± 0.82 3.07 ± 0.74 1.92 ± 0.49 1.40 ± 0.42

Conv. 3.28 ± 1.03 3.62 ± 1.12 3.14 ± 0.92 1.87 ± 0.56 1.55 ± 0.75

Imm.

Plus-minus values are means ± SD. * After implant placement for bone levels and before implant placement for gingival levels and pocket depths. # One implant was lost three weeks after implant placement. ‡ Mesial and distal sides combined. Abbreviations: Imm=immediate loading, Conv=conventional loading, T6m= 6 months after implant placement, T18m= 18 months after implant placement.

Probing pocket depth (mm) Mesial of implant Distal of implant Mid-facial of implant Proximal of teeth‡ Mid-facial of teeth

Table 2. (Continued) T18m

3.19 ± 0.91 3.81 ± 1.28 3.32 ± 0.79 1.99 ± 0.60 1.37 ± 0.34

Conv.

for the radiographs and photographs was -0.02 ± 0.33 mm (limits of agreement: -0.68 and 0.64 mm) and -0.02 ± 0.18 mm (limits of agreement: – 0.38 and 0.34 mm), respectively. The intraclass correlation coefficients were 0.95 and 0.98 for the radiographic inter- and intra-observer agreement, respectively, and 0.99 for the photographic inter-observer agreement, all signifying high levels of agreement.

Chapter

5

Marginal bone level change The mean marginal bone loss (mesial and distal implant sides combined) from implant placement (baseline, T0) to 18 months thereafter (T18m) was 0.91 ± 0.61 mm in the immediate group [95% confidence interval (CI): 0.69-1.13] and 0.90 ± 0.57 mm in the conventional group [95% CI: 0.70-1.10] (P > 0.05)(Table 2). In both study groups the amount of bone loss proximal to the implant had decreased significantly after the second follow-up visit (T6m) (Table 2). There were no significant differences between both study groups regarding bone level changes at the adjacent teeth. Clinical outcome One implant in the immediate group was lost three weeks after placement due to high mobility. The implant survival rate at T18m was 96.8 % for the immediate group and 100% for the conventional group (P>0.05). No between-group differences in soft tissue levels changes around the implants and adjacent teeth were observed (Table 2). After definitive crown placement, the level of the mid-facial peri-implant mucosa remained stable while a mean gain of the papilla level of 0.34 ± 0.49 mm and 0.27 ± 0.42 mm was observed in the immediate and conventional group, respectively (P>0.05) (Table 2). From Tpre to T18m, the mid-facial gingival level of the adjacent teeth showed a mean recession of 0.29 ± 0.44 mm in the immediate group and 0.28 ± 0.36 mm in the conventional group (P>0.05), which predominately occurred during the first evaluation period. The clinical assessments yielded no significant differences between both groups for probing pocket depth (Table 2), plaque index, bleeding index and papillae index. Bleeding index scores of the adjacent teeth were significantly lower compared to the scores of the implants (Figure 2). The volume of the distal papillae, expressed in papilla index scores, increased significantly during follow-up (Figure 3). Plaque index scores were low at both follow-up visits. At T18m, a plaque score of 1 was assigned to three implants in both study groups. All other implants did not show any plaque. Within-group analysis revealed lower plaque scores for the adjacent teeth at T6m and T18m compared to the preoperative situation (Tpre)(P0.05). The pink aesthetics were judged with a mean PES of 7.1±1.5 (range 3-10) and 6.5±1.63 (range 4-10) for the immediate and conventional group, respectively. According to the ICAI, the pink aesthetics were satisfactory in 24 cases (80%) in the immediate group and 19 cases in the conventional group (62%), of which 1 case in both groups showed excellent pink aesthetics. The white aesthetics in the immediate group were judged with a mean WES of 7.8±1.5 (range 4-10) and in the conventional group with a mean of 7.6±1.6 (range 4-10). Patient satisfaction Patient satisfaction was high in both study groups and no differences were observed between the groups (Table 3). At both follow-up visits (T6m and T18m) onethird of the patients in the conventional group mentioned the healing time of the implant as long.

Discussion This randomized clinical trial revealed that the treatment outcome of immediate loading of a single-tooth implant in the maxillary anterior zone is not less favorable than conventional loading. After 18 months of follow-up, both treatment strategies showed an equal amount of radiographic peri-implant marginal bone loss and similar outcomes regarding survival, soft tissue aspects, aesthetic outcome and patient satisfaction. Studies on immediate loading are often founded on implant survival rates. This is indeed a major outcome determining treatment success to a high extent. In our study, survival rates were 96.8% for the immediate group (one implant failed) and 100% for the conventional group. These high survival rates were confirmed by other studies on immediately loaded implants, even when inserted in fresh extraction sockets (Den Hartog et al. 2008). We realize that the sample size of our study was too small to demonstrate whether immediate loading was noninferior to conventional loading with respect to implant survival. Additional (longterm) studies would be helpful to draw firm conclusions regarding the potential 94

26 3 0 100

Conv.

100 97 90 80

94 94

9.0 ± 1.0

% In agreement*

9.2 ± 0.8

n.a. 0 0 97

Imm.

100 93 97 87

97 97

Conv. (n=31)

32 10 0 100

Conv.

97 100 87 87

97 100

Conv. (n=31)

8.9 ± 1.0

% In agreement*

9.3 ± 0.9

n.a. 3 0 100

Imm.

93 100 97 87

100 100

Imm. (n=30)**

T18m % Satisfied*

Abbreviations: Imm=Immediate loading, Conv= Conventional loading, T6m= 6 months after implant placement, T18m= 18 months after implant placement, n.a., not applicable, VAS= visual analogue scale.

* Represents percent satisfied or in agreement on 5-point scale (4 or 5 equals satisfied or in agreement). ** One implant was lost three weeks after placement.

General satisfaction (VAS-score; mean±SD)

Treatment procedure The healing time of the implant was long I didn’t like the visits to the dentist to make the crown I regret that I choose this treatment I would recommend the treatment to other patients

Aesthetics Colour of the crown Form of the crown Colour of the mucosa around the crown Form of the mucosa around the crown

Function Eating Speaking

Imm. (n=30)**

T6m % Satisfied*

Table 3. Patient satisfaction regarding function, aesthetics, treatment procedure and general satisfaction.

Chapter

5

hazardous effect of immediate loading on the process of osseointegration. No differences were observed between immediate and conventional loading regarding marginal bone loss at 6 and 18 months post-implant placement and the values we found were consistent with what has been reported in other studies on immediate and conventional single-tooth implants in the anterior zone (Hall et al. 2007, Den Hartog et al. 2008, Degidi et al. 2009). Since it is known that the proximal bone level next to the adjacent teeth is highly relevant for the level of the proximal papillae of the implant (Choquet et al. 2001, Kan et al. 2003, Block et al. 2009), also these bone levels were taken into consideration as an important predictor for the aesthetic outcome. In both study groups, only a small amount of bone loss at the adjacent teeth was noticed during follow-up. It is questionable whether this amount of bone loss affected the level of the implant papillae, which gained height during follow up. However, it should be realized that implant therapy is not without consequences for the mid-facial level of the adjacent teeth, showing a recession of about 0.3 mm in both groups with an even standard deviation. There is growing evidence that immediate loading of implants inserted in fresh extraction sockets would lead to more favorable soft tissue levels compared to a delayed strategy (De Rouck et al. 2009, Block et al. 2009). These studies showed that i����������������������������������������������������������������������������� mmediate stabilization of the soft tissue after tooth removal by means of immediate implant placement and immediate placement of the provisional crown, revealed 0.75 to 1 mm more soft tissue preservation mid-facially. However, the reliability of this strategy should be established by more well-designed studies (Den Hartog et al. 2008). In our study, all implants were inserted in healed sites. After tooth removal, the walls of the alveolus undergo substantial resorption affecting the soft tissue anatomy (Schropp et al. 2003, Araujo & Lindhe 2005). It could be that for healed sites, the potential positive effect of an immediate (provisional) crown on soft tissue preservation subsided. When using the PES and ICAI as instruments to express soft tissue aesthetics, at least no significant difference between immediate and conventionally loaded implants was observed. The same applied to the volume of the papilla assessed with the papilla index. This index in particular could, however, be more related to the bone level of the adjacent teeth as discussed earlier. More clinical trials are needed investigating the influence of an immediately placed (provisional) crown on soft tissue parameters. Overall patient satisfaction was high in both study groups and patients were satisfied regarding function, aesthetics and treatment procedure. Other studies on anterior single-tooth implants reported comparable overall satisfaction scores of 8.8 and higher (also using VAS) (Schropp et al. 2004, Den Hartog et al. 2008). As confirmed by other studies (Levi et al. 2003, Schropp et al. 2004), a substantial percentage of conventionally treated patients (30%) experienced the healing 96

97

Immediate loading

time of the implant as long. Although, Levi et al. (2003) found that treatment time was not a critical factor for overall satisfaction, the shorter treatment time of immediate loading might serve these patients. It is important to reach sufficient primary implant stability before performing immediate loading. However, the threshold for sufficient primary stability has not been adopted uniformly in studies on immediate single-tooth implant loading. Furthermore, different methods were used to assess primary implant stability or the method to assess stability was not reported (Den Hartog et al. 2008). We utilized insertion torque as a diagnostic tool to express implant stability. Since it has been reported that insertion torque is related to the amount of micromotion (Trisi et al. 2009), we believe that this is a viable method. In our study, all implants could be installed with a minimum insertion torque of 45 Ncm. Although a lower value was not considered as an exclusion criterion beforehand, this may introduce a higher risk of implant failure. A minimum torque value of 35 Ncm has been successfully adopted in other studies on immediate loading, even when inserted in fresh extraction sites (Wang et al. 2006, De Rouck et al. 2009). In our study, provisional crowns were free from centric and eccentric contacts with the antagonist teeth. This strategy has been defined as immediate non-functional loading (Laney 2007) and loading occurs from lip and tongue pressure and contact with food, but not from contact with the opposing dentition. Results from single implant studies on immediate functional loading with a (provisional) crown in centric occlusion, suggest that this might lead to comparable survival rates as immediate non-functional loading (Rao & Benzi 2007, Glauser et al. 2007, Schincaglia et al. 2008). However, these studies focussed on tooth replacements in posterior regions in particular where implants were subjected to more vertically directed forces. In the anterior region, the lateral component of occlusal force is more dominant and could act as a disrupting factor in the process of implant integration (Katona et al. 1993, Lin et al. 2007). We did not experience any problems to create a non-occluding provisional crown with acceptable aesthetics and therefore recommend this more reserved strategy above a functional loading concept. Furthermore, a dominant role should be ascribed to carefully instructing the patient to follow a soft diet and to avoid exerting force on the provisional restoration. In conclusion, this study demonstrates that - on the short term - immediate loading of a single-tooth implant in the maxillary aesthetic zone leads to a treatment outcome that is not less favorable than conventional loading. As immediate loading reduces the treatment time and could offer more comfort for the patient, we recommend this strategy to be considered as an alternative to conventional loading. However, the concept of immediate loading should be performed according to a specified protocol with attention to adequate primary implant stability, a non-occluding provisional crown and careful patient instruction.

5

References

Critical review of immediate implant loading. Clinical Oral Implants Research 14, 515-527.

Altman D.G., (1991) Practical Statistics for Medical Research. London: Chapman & Hall. Araujo, M.G. & Lindhe, J., (2005) Dimensional ridge alterations following tooth extraction. An experimental study in the dog. Journal of Clinical Periodontology 32, 212-218. Belser, U.C., Grutter, L., Vailati, F., Bornstein, M.M., Weber, H.P. & Buser, D. (2009) Outcome evaluation of early placed maxillary anterior single-tooth implants using objective esthetic criteria: a cross-sectional, retrospective study in 45 patients with a 2- to 4-year follow-up using pink and white esthetic scores. Journal of Periodontology 80, 140-151. Block, M.S., Mercante, D.E., Lirette, D., Mohamed, W., Ryser, M. & Castellon, P. (2009) Prospective evaluation of immediate and delayed provisional single tooth restorations. Journal of Oral and Maxillofacial Surgery 67, 89-107.

Chapter

5

Choquet, V., Hermans, M., Adriaenssens, P., Daelemans, P., Tarnow, D.P. & Malevez, C. (2001) Clinical and radiographic evaluation of the papilla level adjacent to single-tooth dental implants. A retrospective study in the maxillary anterior region. Journal of Periodontology 72, 1364-1371. Cox, J.F. & Zarb, G.A. (1987) The longitudinal clinical efficacy of osseointegrated dental implants: a 3-year report. International Journal of Oral and Maxillofacial Implants 2, 91-100. De Rouck, T., Collys, K., Wyn, I. & Cosyn, J. (2009) Instant provisionalization of immediate single-tooth implants is essential to optimize esthetic treatment outcome. Clinical Oral Implants Research 20, 566-570. Degidi, M., Nardi, D. & Piattelli, A. (2009) Immediate versus one-stage restoration of small-diameter implants for a single missing maxillary lateral incisor: a 3-year randomized clinical trial. Journal of Periodontology 80, 1393-1398.

Glauser, R., Zembic, A. & Hammerle, C.H. (2006) A systematic review of marginal soft tissue at implants subjected to immediate loading or immediate restoration. Clinical Oral Implants Research 17 Suppl 2, 82-92. Glauser, R., Zembic, A., Ruhstaller, P. & Windisch, S. (2007) Five-year results of implants with an oxidized surface placed predominantly in soft quality bone and subjected to immediate occlusal loading. Journal of Prosthetic Dentistry 97, S59-S68. Grutter, L. & Belser, U.C. (2009) Implant loading protocols for the partially edentulous esthetic zone. International Journal of Oral and Maxillofacial Implants 24 Suppl, 169-179. Hall, J.A., Payne, A.G., Purton, D.G., Torr, B., Duncan, W.J. & De Silva, R.K. (2007) Immediately restored, single-tapered implants in the anterior maxilla: prosthodontic and aesthetic outcomes after 1 year. Clinical Implant Dentistry and Related Research 9, 34-45. Jemt, T. (1997) Regeneration of gingival papillae after singleimplant treatment. International Journal of Periodontics and Restorative Dentistry 17, 326-333. Kan, J.Y., Rungcharassaeng, K., Umezu, K. & Kois, J.C. (2003) Dimensions of peri-implant mucosa: an evaluation of maxillary anterior single implants in humans. Journal of Periodontology 74, 557-562. Katona, T.R., Goodacre, C.J., Brown, D.T. & Roberts, W.E. (1993) Force-moment systems on single maxillary anterior implants: effects of incisal guidance, fixture orientation, and loss of bone support. International Journal of Oral and Maxillofacial Implants 8, 512-522. Laney, W.R. (2007) Glossary of Oral and Maxillofacial Implants. Berlin:Quintessence. Levi, A., Psoter, W.J., Agar, J.R., Reisine, S.T. & Taylor, T.D. (2003) Patient self-reported satisfaction with maxillary anterior dental implant treatment. International Journal of Oral and Maxillofacial Implants 18, 113-120.

Den Hartog, L., Raghoebar, G.M., Stellingsma, K. & Meijer, H.J. (2009) Immediate loading and customized restoration of a single implant in the maxillary esthetic zone: a clinical report. Journal of Prosthetic Dentistry 102, 211-215. Den Hartog, L., Slater, J.J., Vissink, A., Meijer, H.J. & Raghoebar, G.M. (2008) Treatment outcome of immediate, early and conventional single-tooth implants in the aesthetic zone: a systematic review to survival, bone level, soft tissue, aesthetics and patient satisfaction. Journal of Clinical Periodontology 35, 1073-1086. Esposito, M., Grusovin, M.G., Achille, H., Coulthard, P. & Worthington, H.V. (2009) Interventions for replacing missing teeth: different times for loading dental implants. Cochrane Database of Systematic Reviews CD003878. Gapski, R., Wang, H.L., Mascarenhas, P. & Lang, N.P. (2003)

98

Lin, C.L., Chang, S.H., Chang, W.J. & Kuo, Y.C. (2007) Factorial analysis of variables influencing mechanical characteristics of a single tooth implant placed in the maxilla using finite element analysis and the statistics-based Taguchi method. European Journal of Oral Sciences 115, 408-416. Lioubavina-Hack, N., Lang, N.P. & Karring, T. (2006) Significance of primary stability for osseointegration of dental implants. Clinical Oral Implants Research 17, 244-250. Meijer, H.J., Stellingsma, K., Meijndert, L. & Raghoebar, G.M. (2005) A new index for rating aesthetics of implant-supported single crowns and adjacent soft tissues--the Implant Crown Aesthetic Index. Clinical Oral Implants Research 16, 645-649.

Meijndert, L., Meijer, H.J., Raghoebar, G.M. & Vissink, A. (2004) A technique for standardized evaluation of soft and hard peri-implant tissues in partially edentulous patients. Journal of Periodontology 75, 646-651. Mesa, F., Munoz, R., Noguerol, B., Dios Luna, J., Galindo, P. & O’Valle, F. (2008) Multivariate study of factors influencing primary dental implant stability. Clinical Oral Implants Research 19, 196-200.

Immediate loading

Mombelli, A., van Oosten, M.A., Schurch E Jr & Land, N.P. (1987) The microbiota associated with successful or failing osseointegrated titanium implants. Oral Microbiology and Immunology 2, 145-151. Rao, W. & Benzi, R. (2007) Single mandibular first molar implants with flapless guided surgery and immediate function: preliminary clinical and radiographic results of a prospective study. Journal of Prosthetic Dentistry 97, S3-S14. Roze, J., Babu, S., Saffarzadeh, A., Gayet-Delacroix, M., Hoornaert, A. & Layrolle, P. (2009) Correlating implant stability to bone structure. Clinical Oral Implants Research 20, 1140-1145.

5

Schincaglia, G.P., Marzola, R., Giovanni, G.F., Chiara, C.S. & Scotti, R. (2008) Replacement of mandibular molars with single-unit restorations supported by wide-body implants: immediate versus delayed loading. A randomized controlled study. International Journal of Oral and Maxillofacial Implants 23, 474-480. Schropp, L., Isidor, F., Kostopoulos, L. & Wenzel, A. (2004) Patient experience of, and satisfaction with, delayed-immediate vs. delayed single-tooth implant placement. Clinical Oral Implants Research 15, 498-503. Schropp, L., Wenzel, A., Kostopoulos, L. & Karring, T. (2003) Bone healing and soft tissue contour changes following single-tooth extraction: a clinical and radiographic 12-month prospective study. International Journal of Periodontics and Restorative Dentistry 23, 313-323. Smeets, E.C., de Jong, K.J., Abraham-Inpijn, L. (1998) Detecting the medically compromised patient in dentistry by means of the medical risk-related history. A survey of 29,424 dental patients in The Netherlands. Preventive Medicine 27, 530-535. Trisi, P., Perfetti, G., Baldoni, E., Berardi, D., Colagiovanni, M. & Scogna, G. (2009) Implant micromotion is related to peak insertion torque and bone density. Clinical Oral Implants Research 20, 467-471. Wang, H.L., Ormianer, Z., Palti, A., Perel, M.L., Trisi, P. & Sammartino, G. (2006) Consensus conference on immediate loading: the single tooth and partial edentulous areas. Implant Dentistry 15, 324-333.

99

6. Immediate loading and customized restoration of a single-tooth implant in the maxillary aesthetic zone: a clinical report

This is an edited version of the manuscript: Den Hartog, L., Raghoebar, G.M., Stellingsma, K., Meijer, H.J. Immediate loading and customized restoration of a single implant in the maxillary esthetic zone: a clinical report. Journal of Prosthetic Dentistry 2009; 102: 211-215

Abstract The replacement of a single missing anterior tooth with a dental implant is a demanding therapy. This report describes a treatment in which an anterior maxillary implant was immediately restored with a provisional restoration. During the provisional phase, an optimal emergence profile was created by adjusting the provisional restoration. An impression was made with an individually fabricated impression post for an accurate reproduction of the established emergence profile and finally a screw-retained all-ceramic crown was placed. By implementing this protocol, an optimal definitive result could be achieved together with immediate patient satisfaction. However, cooperation between several disciplines and careful patient selection were required.

Chapter

6

102

The application of dental implant to restore a missing tooth in the anterior dentition is challenging. In the aesthetic zone, both the appearance of the implant crown and the soft tissue contribute to a successful treatment outcome and should consequently be in harmony with the surrounding dentition (Chang et al. 1999, Belser et al. 2004). To accomplish the desired result, meticulous pre-operative treatment planning is crucial together with cooperation between several disciplines during the restorative phase. In recent literature, several treatment strategies using dental implants have been reported to replace a missing tooth (Den Hartog et al. 2008). Among these, interest has been attributed to immediate or early loading protocols in which a provisional restoration is placed soon after implant placement. Clinical studies of immediate or early loading have reported favorable treatment outcomes in terms of implant survival, marginal bone resorption, soft tissue level and the incidence of complications for treatment in which implants were inserted in healed sites (Ericsson et al. 2000, Andersen et al. 2002, Cooper et al. 2007, Hall et al. 2007) as well as implants placed in fresh extraction sockets (Crespi et al. 2008, de Rouck et al. 2008). However, a recent systematic review (Den Hartog et al. 2008) showed that well-designed controlled studies that compare these approaches with conventional protocols are scarce and whether or not superior aesthetic outcomes could be achieved remained inconclusive. Immediate or early implant loading provides several advantages for the patient including a shorter overall treatment time, avoidance of a second-stage operation and eliminating the need for a removable prosthesis during the healing phase. However, these protocols require careful pre-operative planning and patient selection. Furthermore, good primary implant stability is a prerequisite (Esposito et al. 2007), in addition to the development of a protected occlusion to create a non-occluding provisional crown. Another important development has been the introduction of alumina- and zirconia-based ceramic abutments made with computer-aided design/computer-aided manufacturing (CAD/CAM) technology. Ceramic abutments are highstrength (Sundh & Sjögren 2008, Yüzügüllü & Avci 2008,) biocompatible (Welander et al. 2008) and have allowed new options to improve the natural appearance of the implant crown. However, little is known about the long-term clinical performance of these abutments (Linkevicius & Apse 2008). The purpose of this clinical report was to demonstrate an immediate implant loading protocol for restoration of a missing central incisor. After the provisional restoration phase, an individually fabricated impression post was used and subsequently a definitive screw-retained one piece all-ceramic crown was placed.

103

Clinical report

Introduction

6

Figure 1. Pre-operative view.

Figure 2. Exposure of the alveolar bone.

Chapter

6

Figure 3. Screw-retained provisional crown placed same day after implant surgery.

104

105

Clinical report

Clinical report A 47-year-old woman consulted the Department of Oral and Maxillofacial Surgery (University Medical Center Groningen, University of Groningen, Groningen, the Netherlands) with a missing right central incisor (Figure 1) lost due to a traumatic injury. At the time of the consultation she was wearing a removable partial denture and desired a durable and fixed restoration, without involvement of the adjacent teeth. The patient was healthy, did not smoke and intraoral examination revealed a healthy well-maintained dentition. Clinically, adequate bone volume was present at the future implant site. In all dimensions, sufficient space was available for an implant crown with an anatomical design. Radiographically, no pathology of the bone and adjacent teeth was noted. Because of the favorable starting point, it was decided to use an immediate loading protocol. Preoperatively, diagnostic casts were made with a diagnostic arrangement representing the future implant crown in an ideal position. Next, a transparent acrylic resin template (Vertex Castapress; Vertex Dental, Zeist, the Netherlands) was fabricated and a guide channel was prepared in the template to aid in proper implant placement. Care was taken with the surgical guide so that the guidance channel would direct the implant sufficiently toward the palate to accommodate a screw-retained restoration. One day before surgery, the patient started taking antibiotics (amoxicillin 500 mg, 3 times daily for seven days) and used a 0.2% chlorhexidine mouthwash (Corsodyl; GlaxoSmithKline, Utrecht, the Netherlands) for oral disinfection. Following local anaesthesia (Ultracaine D-S Forte; Aventis Pharma, Hoevelaken, the Netherlands) a slightly palatal crest-incision was made with extensions through the buccal and palatal sulcus of the adjacent teeth. A minimal mucoperiosteal flap was elevated to expose only the ridge crest (Figure 2). Then, an implant (NobelReplace Tapered RP 16 mm, Nobel Biocare, Gothenburg, Sweden) was placed according to the procedure prescribed by the manufacturer guided by the surgical template. The shoulder of the implant was placed at a depth of 3 mm apical to the buccal and cervical aspect of the prospective clinical crown to provide soft tissue to develop an adequate emergence profile. Good primary implant stability was obtained (> 45 Ncm, determined with Osseocare; Nobel Biocare). Next, an opentray impression was made at the implant level using a custom resin impression tray (Lightplast base plates; Dreve Dentamid, Unna, Germany) and a polyether impression material (Impregum Penta; 3M ESPE, St. Paul, Minnesota, USA.). Finally, a healing abutment (NobelReplace; Nobel Biocare) was placed and the wound was closed with sutures (Ethilon 5-0; Johnson & Johnson Gateway, Piscataway, New Jersey, USA). In the dental laboratory, a screw-retained provisional restoration was fabricated consisting of an engaging temporary abutment (Temporary Abutment Engaging

6

Figure 4. View of peri-implant soft tissue after the provisional restoration phase. Note established emergence profile.

Figure 5. Assembly of provisional crown with implant analog and impression of cervical portion of provisional crown.

Chapter

6

Figure 6. Customized impression post.

106

107

Clinical report

NobelReplace; Nobel Biocare) against which composite resin (Solidex; Shofu Inc, Kyoto, Japan) was modelled. Eight hours post-implant placement, the abutment was removed and the provisional crown was placed and subsequently torqued to 32 Ncm (Figure 3). Special care was taken to prevent any centric and eccentric occlusal contacts with the antagonist teeth. Furthermore, the provisional restoration was contoured so that the peri-implant soft tissue was optimally supported. In particular, the interproximal papillae were given enough space to regenerate. The patient was instructed to follow a soft diet, to avoid exerting force on the provisional restoration and to continue chlorhexidine rinses (Corsodyl; GlaxoSmithKline, Utrecht, The Netherlands) for seven days. For pain control, ibuprofen 600 mg (Brufen Bruis 600; Abott B.V., Hoofddorp, The Netherlands, three times daily for time needed) was prescribed and at two weeks post surgery the sutures were removed. The patient returned to the prosthodontist once a month for three months for examination of the implant. During these sessions, implant mobility, oral hygiene and occlusion were evaluated. Also, an important objective was the creation of an ideal emergence profile by removing the provisional crown. Extraorally and where needed, composite resin was removed or added to aspects of the crown to create more space or more support for the soft tissue. In this process, special attention was given to the shape of the proximal contour to provide an optimal condition for the papillae to reach maturity. Three months later (six months post-implant placement) an implant level impression was made using an impression post (Impression Coping Implant Level Open Tray NobelReplace; Nobel Biocare) that was customized in a way that the obtained emergence profile could be transferred to the definitive restoration (Figure 4). To realize this, the provisional crown was assembled with an implant analog (Implant Replica NobelReplace; Nobel Biocare) embedded in type IV dental stone (GC Fuji Rock EP; GC Europe N.V., Leuven, Belgium). An addition silicone impression (Futar D; Kettenbach GmbH & Co KG, Eschenburg, Germany) of the cervical portion of the crown was made (Figure 5). Next, the latter was substituted for an impression post and bis acrylic composite resin (Protemp; 3M ESPE, St. Paul, Minn) was added to the post. After polishing the individualized post (Figure 6) it was inserted into the implant and an open-tray impression was made with a polyether impression material (Impregum Penta; 3M ESPE) and a custom resin impression tray (Lightplast base plates; Dreve Dentamid). In the dental laboratory, a soft tissue cast was prepared. First, a waxing of the definitive crown was made on a temporary abutment (Temporary Abutment Engaging NobelReplace; Nobel Biocare). The screw access hole was located sufficiently to the palate to create a screw-retained crown and to prepare an appropriate abutment. Therefore, the waxing was cut back to the desired form and scanned

6

Figures 7 & 8. Application of porcelain to individually fabricated Procera zirconia abutment to create a one-piece screw-retained definitive crown.

Chapter

6

Figure 9. Clinical view of definitive implant crown 18 months after implant placement.

108

Discussion This report describes an immediate loading protocol finalized with the placement of a screw-retained all-ceramic restoration. A major prerequisite for immediate loading is a high degree of primary stability in terms of high insertion torque (Esposito et al. 2007). In this treatment, an initial insertion torque of at least 45 Ncm was reached. Although clinical studies on immediate single-tooth implant loading reported varying minimal insertion torques for immediate loading, the authors of this report adopted a threshold of 45 Ncm. In this patient, a substantial maturation of the papillae occurred during the provisional phase. Care was taken to ensure that the provisional crown did not disturb this process, but served as a natural guide. Regeneration of papillae with time has been reported in several studies (Jemt & Lekholm 2005, Schropp et al. 2005), but the mechanism behind this phenomenon could not validly be explained. Some authors believed that this increase might be attributed to remodelling potential of the soft tissue to establish a proper biological height after the surgical manipulation (Chang et al. 1999). It is widely accepted however, that the interproximal bone level next to the adjacent teeth is important for the future level of the interproximal papillae of the implant (Belser et al. 2004). Finally, a screw-retained definitive restoration was fabricated. The advantages of this type of restoration compared to a cement-retained restoration include retrievability and no risks for cement remnants thereby excluding possible irritation of the peri-implant tissues. However, the presence of a screw access opening decreases fracture resistance of the porcelain (Torrado et al. 2004). Furthermore, screw-retained restorations necessitate precise implant positioning for a proper palatal position of the screw access hole that does not interfere with the aesthetics.

109

Clinical report

for fabrication of an individual zirconia abutment (Procera; Nobel Biocare AB). Porcelain was added directly to the abutment to create a screw-retained one piece definitive restoration (Figures 7 & 8). The restoration was placed and the abutment screw was torqued with 32 Ncm. Finally, the screw hole was filled with a cotton pellet and composite resin (Clearfil AP-X; Kuraray Medical Inc, Okayama, Japan). The restoration has been in service for 18 months without complication (Figure 9).

6

crestal contours in a 6-year prospective clinical study. Clinical Implant Dentistry and Related Research 7, 127-135.

References Andersen, E., Haanaes, H.R. & Knutsen, B.M. (2002) Immediate loading of single-tooth ITI implants in the anterior maxilla: a prospective 5-year pilot study. Clinical Oral Implants Research 13, 281-287. Belser, U.C., Schmid, B., Higginbottom, F. & Buser, D. (2004) Outcome analysis of implant restorations located in the anterior maxilla: a review of the recent literature. International Journal of Oral and Maxillofacial Implants 19 Suppl, 30-42.

Linkevicius, T. & Apse P. (2008) Influence of abutment material on stability of peri-implant tissues: a systematic review. International Journal of Oral and Maxillofacial Implants 23, 449-456

Chang, M., Wennstrom, J.L., Odman, P. & Andersson, B. (1999) Implant supported single-tooth replacements compared to contralateral natural teeth. Crown and soft tissue dimensions. Clinical Oral Implants Research 10, 185-194.

Chapter

6

Kan, J.Y., Rungcharassaeng, K. & Lozada, J. (2003) Immediate placement and provisionalization of maxillary anterior single implants: 1-year prospective study. International Journal of Oral and Maxillofacial Implants 18, 31-39.

Cooper, L.F., Ellner, S., Moriarty, J., Felton, D.A., Paquette D. & Molina, A. (2007) Three-year evaluation of single-tooth implants restored 3 weeks after 1-stage surgery. International Journal of Oral and Maxillofacial Implants 22, 791-800. Crespi, R., Capparé, P., Gherlone, E. & Romanos, G.E. (2008) Immediate versus delayed loading of dental implants placed in fresh extraction sockets in the maxillary esthetic zone: a clinical comparative study. International Journal of Oral and Maxillofacial Implants 23, 753-758. De Rouck, T., Collys, K. & Cosyn, J. (2008) Immediate single-tooth implants in the anterior maxilla: a 1-year case cohort study on hard and soft tissue response. Journal of Clinical Periodontology 35, 649-657. Den Hartog, L., Slater, J.J., Vissink, A., Meijer, H.J. & Raghoebar, G.M. (2008) Treatment outcome of immediate, early and conventional single-tooth implants in the aesthetic zone: a systematic review to survival, bone level, soft tissue, aesthetics and patient satisfaction. Journal of Clinical Periodontology 35, 1073-1086. Esposito, M., Grusovin, M.G., Willings, M., Coulthard, P. & Worthington, H.V. (2007) Interventions for replacing missing teeth: different times for loading dental implants. Cochrane Database of Systematic Reviews 18, CD003878. Ericsson, I., Nilson, H., Lindh, T., Nilner, K. & Randow, K (2000). Immediate functional loading of Branemark single tooth implants. An 18 months’ clinical pilot follow-up study. Clinical Oral Implants Research 11, 26-33. Hall, J.A., Payne, A.G., Purton, D.G., Torr, B., Duncan, W.J. & De Silva, R.K. (2007) Immediately restored, single-tapered implants in the anterior maxilla: prosthodontic and aesthetic outcomes after 1 year. Clinical Implant Dentistry and Related Research 9, 34-45. Jemt, T. & Lekholm, U. (2005) Single implants and buccal bone grafts in the anterior maxilla: measurements of buccal

110

Meijndert, L., Raghoebar, G.M., Meijer H.J. & Vissink, A. (2008) Clinical and radiographic characteristics of singletooth replacements preceded by local ridge augmentation: a prospective randomized clinical trial. Clinical Oral Implants Research 19, 1295-1303. Palmer, R.M., Palmer, P.J. & Smith, B.J. (2000) A 5-year prospective study of Astra single tooth implants. Clinical Oral Implants Research 11, 179-182. Palattella, P., Torsello, F. & Cordaro, L. (2008) Two-year prospective clinical comparison of immediate replacement vs. immediate restoration of single tooth in the esthetic zone. Clinical Oral Implants Research 19, 1148-1153. Schropp, L., Isidor, F., Kostopoulos, L. & Wenzel, A. (2005) Interproximal papilla levels following early versus delayed placement of single-tooth implants: a controlled clinical trial. International Journal of Oral and Maxillofacial Implants 20, 753-761. Sundh, A. & Sjögren G. (2008) A study of the bending resistance of implant-supported reinforced alumina and machined zirconia abutments and copies. Dental Materials 24, 611-617. Torrado, E., Ercoli, C., Al Mardini, M., Graser, G.N., Tallents, R.H. & Cordaro L. (2004) A comparison of the porcelain fracture resistance of screw-retained and cementretained implant-supported metal-ceramic crowns. Journal of Prosthetic Dentistry 91, 532-537. Welander, M., Abrahamsson, I. & Berglundh T. (2008) The mucosal barrier at implant abutments of different materials. Clinical Oral Implants Research 19, 635-641. Yüzügüllü, B. & Avci, M. (2008) The implant-abutment interface of alumina and zirconia abutments. Clinical Implant Dentistry and Related Research 10, 113-121.

6

111 Clinical report

7. Trauma to an implant crown that was saved by the fixation screw: a case report

This is an edited version of the manuscript: Trauma to an implant-supported crown that was saved by the fixation screw: a case report. Den Hartog, L., Meijer, H.J.A., Stellingsma, K., Santing, H.J., Raghoebar, G.M. Dental Traumatology 2010; 26: 366-369

Abstract

Chapter

7

A traumatic impact to an implant crown might damage the implant, crown and peri-implant tissue. Ideally, only a small prosthetic retreatment is needed for restoration, since a complicated prosthetic retreatment or a surgical retreatment in particular, could be very inconvenient for the patient. However, there is a deficiency in literature on how the implant, restoration and surrounding tissues generally react to impact forces. This report demonstrates a case of trauma to an implant crown in the maxillary anterior zone resulting in a palatal displacement of the crown. After careful examination and follow-up, it appeared that only the fixation screw was damaged, while the implant, crown and peri-implant tissue remained unharmed. Thanks to the protective qualities of the implant system, an easy prosthetic retreatment could restore the implant crown and a surgical retreatment was prevented.

114

It is known that a missing anterior tooth can be successfully replaced with a dental implant (Creuger et al. 2000, Belser et al. 2004, Den Hartog et al. 2008). However, after implant therapy is completed, several complications might occur ( Berglundh et al. 2002, Jung et al. 2008). These vary from peri-implant soft tissue lesions (viz. peri-implant mucositis, soft tissue dehiscence, fistula) and abnormal marginal peri-implant bone loss (peri-implantitis), to more technicalrelated complications as implant fracture and fracture or loosening of the abutment, fixation screw or crown. Overload by occlusal forces is one of the factors that may induce these complications (Esposito et al. 1999, Piatelli et al. 2003, Khraisat et al. 2004). Besides this overload, a relatively rare factor is an acute excessive load caused by a dental trauma. There is a deficiency in literature concerning the consequences of these suddenly high forces to the implant, restoration and surrounding tissues. To date, only three case reports have been published that present the consequences of a trauma to implant crowns (Flanagan 2003, Stuebinger et al. 2004, Allen & Allen 2006). In two cases, the trauma resulted in damaged implant crowns and a bent fixation screw, but the implants sustained no damage (Flanagan 2003, Stuebinger et al. 2004). In one case however, the implant gave way resulting in a palatal movement of the implant within the bone, possibly in combination with a fracture of the alveolar process (Allen & Allen 2006). Because the implant remained osseointegrated, it was restored with a new implant crown. This report is aimed to further demonstrate the consequences of a trauma to an anterior implant crown and the subsequent therapeutic approach that was performed.

Case report An 18-year-old man was referred to the Department of Oral and Maxillofacial Surgery (University Medical Center Groningen, University of Groningen, Groningen, the Netherlands) for replacement of a right central incisor with an implant supported crown. Six years ago this tooth had been avulsed in a bicycle accident and was subsequently replanted. Because of severe root resorption and a persistent fistula, the tooth could not longer be saved. After extraction, an augmentation procedure was performed with an autogenous retromolar bone graft, Geistlich Bio-Oss® (Geistlich Pharma AG, Wolhusen, Switzerland) and Geistlich Bio-Gide® (Geistlich Pharma AG) to reconstruct the alveolar process. Four months thereafter, a 16 mm Replace Select Tapered implant (Nobel Biocare AB, Göteborg, Sweden) was placed according to a two-staged procedure. After the osseointegration period, the implant was restored with a one-piece screw-retained all-ceramic crown (Procera, Nobel Biocare AB). 115

Trauma case

Introduction

7

Seven months later (14 months after implant placement), the patient consulted our department following an accident 2 days previously in a swimming pool in which his knee stroke his anterior dentition. He had no pain and only complained about a disrupted occlusion because of displacement of the implant crown. There were no extra-oral injuries. An intra-oral inspection showed that the implant crown was displaced to the palatal, causing a premature contact (Figure 1). The implant crown was neither mobile nor damaged. A slight swelling and redness of the facial peri-implant mucosa was noted. The adjacent natural teeth were intact, vital and did not show increased mobility. Figure 1. Implant supported crown, region 11; palatally displaced after trauma.

Chapter

7

For radiographic examination, a maxillary anterior occlusal radiograph was taken together with a peri-apical radiograph. No abnormalities were detected on the occlusal radiograph. The peri-apical radiograph was closely compared with a peri-apical radiograph that was taken before the accident, just after placement of the crown. Distally, the implant-abutment interface showed a small triangular gap (Figures 2 and 3). It was suggested that the displacement of the implant crown was caused by deformation of the fixation screw. However, it was not certain that, besides this, the alveolar process surrounding the implant had been fractured, causing a displacement of the implant itself. Since the aesthetics were still acceptable for the patient, an expectative policy was pursued. It was possible to leave the implant crown free from occlusion contacts by grinding the porcelain of the palatal aspect of the implant crown. The patient was instructed to follow a soft diet and to avoid force on the implant crown as much as possible. Follow-up visits one and three months later showed status quo. On the last visit, the one116

Figure 3. Radiographic view after trauma. Note the small triangular gap at the distal implant-abutment interface.

Trauma case

Figure 2. Radiographic view after completion of implant therapy, before trauma.

7

piece screw-retained implant crown was removed. A torque wrench was necessary to loosen the fixation screw that was clearly bent (Figure 4). A careful visual inspection of the implant platform and implant crown revealed that both were undamaged. For further investigation of the implant crown, it was installed on the original soft tissue cast with the aid of a laboratory fixation screw. It was found that there was a good fit with the implant analog and that the implant crown was properly located in harmony with the adjacent dentition (Figure 5). The palatal aspect of the implant crown that was grinded earlier was restored in the dental laboratory by fusing a new layer of porcelain. The implant crown was replaced on the implant and fixed with a new fixation screw. The implant-abutment interface was approved radiographically and finally the fixation screw was torqued. The screw hole was filled with a cotton pellet and composite resin (Figure 6).

117

Figure 4. Bent fixation screw.

Figure 5. one-piece screw-retained all-ceramic crown replaced on the original soft tissue cast. The crown is in harmony with the adjacent dentition.

Chapter

7

Figure 6. Clinical view after replacement of the crown with a new fixation screw.

118

This report describes a case of trauma to an anterior implant crown. It appeared that only the fixation screw had sustained damage. Apparently, a major part of the impact energy was absorbed by the deflection of the fixation screw, thereby saving the crown, implant and alveolar bone. Thanks to this protective mechanism, only a small prosthetic retreatment could restore the implant crown. More complicated prosthetic retreatments or surgical retreatments in particular should be prevented as much as possible. We believe that implant components could play an important role in preventing serious damage to the implant or surrounding tissue following an impact force. With respect to the peri-implant bone, it is known that although bone is able to absorb energy, a large force impact applied to an integrated implant, might lead to microcracking or fracture of bone (Flanagan 2003). It is conceivable that as a result, displacement of the implant occurs, or even worse, an extensive fracture of the alveolar process. A study on the impact fracture resistance of implants and abutments showed that 18 out of 20 implants that were embedded in a bonesimulating material, remained intact and were displaced from the embedding material with fracture of the embedding material as a consequence (Silva et al. 2009). In only two specimens with zirconia abutments, the abutments fractured. Assumed that the bone-simulating material is representative of alveolar bone structure, it was suggested that a facial trauma to an osseointegrated implant is likely to lead to fracture of the alveolar bone, leaving the implant intact. To what extent this would actually occur in the clinical situation, is not known. Only one report describes a displacement of an implant after trauma, probably in combination with fracture of the labial cortical bone (Allen & Allen 2006). In this report however, the traumatic incident was only four months after implant placement and the authors hypothesized that the peri-implant bone was not yet maturated and hardly organized, offering little resistance to force. Furthermore, it was argued that the low bone volume present at the implant region could be responsible for the implant displacement and possible fracture. In our case, the trauma occurred 14 months after implant placement and even though a pre-implant augmentation procedure was performed, the peri-implant bone resisted. It turned out that only the fixation screw was damaged. However, at the first consultation after trauma, we were not really sure if the bone surrounding the implant had not been fractured, also causing a displacement of the implant itself. Since the aesthetics were still acceptable for the patient and it was possible to leave the implant crown free from occlusal forces, we decided to adopt an expectative policy allowing the peri-implant bone to rest. Little is known about how the implant and superstructure generally react to an impact. If the superstructure has been damaged, this can be solved by re119

Trauma case

Discussion

7

Chapter

7

pairing or replacing the relevant component, on the condition that it is possible to remove this component from the implant. However, if the implant has to be replaced due to damage or a non-removable component, a complex surgical retreatment is needed with much inconvenience for the patient. In the study by Silva et al. (2009), also impact tests were performed on implants clamped in brass. They found that for implants with titanium abutments, an impact leads to fracture of the abutment screw leaving the abutment and implant intact. Zirconia abutments however, fractured in pieces, but no damage of the implant and abutment screw was observed. It should be noted that in this study, implants with an external implant-abutment connection were tested. Implant systems with internal abutment connections might react differently to an impact, but to our best knowledge, impact tests on these connections are lacking in literature. On the other hand, several studies investigated the strength of different implant-abutment connections under compressive loading tests. These studies could provide valuable information about the stability of implants under high forces. It was found that abutments and abutment screws fractured or bent, while most of the implants remained intact or showed only little damage (Boggan et al. 1999, Norton et al. 2000, Strub et al. 2003, Khraisat 2005, Steinebrunner et al. 2008). This implies that under high forces, the implant is not the weakest link and in general may remain standing after an impact. However, a comment should be made on implants with a smaller diameter. Finite element stress models in which implants with an internal connection were subjected to compressive loading showed that especially implants with a narrow diameter (3.3 mm) are at risk to fracture, since high stresses concentrated at the implant collar (Akça et al. 2003, Nagasawa et al. 2008). Implants with a regular diameter (≥ 4 mm) showed a more favorable stress distribution with lower stresses at the implant collar (Nagasawa et al. 2008). In our case, the patient was restored with a Replace Select Tapered implant and a NobelProcera zirconia abutment. Att and coworkers (2006) evaluated the fracture strength of implant-supported all-ceramic restorations under compressive loading, for the same abutment and implant system as in our case. After the load-to-fracture tests, no implant collar distortion was found for all of the specimens. It was of advantage that our patient was restored with a one-piece screw-retained crown, since it was easy to remove and could be used again. Cement-retained implant crowns are hard to remove without sacrificing crown material. Furthermore, it proved to be helpful that we had documented the implant treatment completely, including the radiographic documentation at various stages and that we kept the original soft tissue cast on which the final crown was fabricated. Although the incidence of trauma to implant restorations is not high, the patient deserves a careful approach that is well-thought. The same is true for 120

Trauma case

preventing irreversible damage leading to complicated prosthetic or surgical retreatments. To our opinion the superstructure should be the weakest link if an implant restoration is subjected to a traumatic impact, thereby preserving the implant and surrounding tissue. Most ideally, the fixation screw absorbs most of the energy thereby protecting the crown, abutment and implant. Moreover, it is important that damaged implant components can be removed from the implant, so that a prosthetic retreatment is feasible. Therefore, more research would be helpful to explore the consequences of an impact to implant systems and corresponding implant components.

7

121

References Akça, K., Cehreli, M.C. & Iplikçioğlu, H. (2003) Evaluation of the mechanical characteristics of the implant-abutment complex of a reduced-diameter morse-taper implant. A nonlinear finite element stress analysis. Clinical Oral Implant Research 14, 444-454. Allen, E.M. & Allen, P.F. (2006) Trauma to an osseointegrated anterior dental implant: a case report. Dental Traumatology 22, 44-47. Att, W., Kurun, S., Gerds, T. & Strub, J.R. (2006) Fracture resistance of single-tooth implant-supported all-ceramic restorations after exposure to the artificial mouth. Journal of Oral Rehabilitation 33, 380-386.

Chapter

7

Belser, U.C., Schmid, B., Higginbottom, F. & Buser D. (2004) Outcome analysis of implant restorations located in the anterior maxilla: a review of the recent literature. International Journal of Oral and Maxillofacial Implants 19, Suppl 30-42. Berglundh, T., Persson, L. & Klinge, B. A. (2002) Systematic review of the incidence of biological and technical complications in implant dentistry reported in prospective longitudinal studies of at least 5 years. Journal of Clinical Periodontology 29, Suppl 3 197-212. Boggan, R.S., Strong, J.T., Misch, C.E. & Bidez, M.W. (1999) Influence of hex geometry and prosthetic table width on static and fatigue strength of dental implants. Journal of Prosthetic Dentistry 82, 436-440. Creugers, N.H., Kreulen, C.M., Snoek, P.A.& De Kanter RJ. (2000) A ����������������������������������������������������� systematic review of single-tooth restorations supported by implants. Journal of Dentistry 28, 209-217. Den Hartog, L., Slater, J.J., Vissink, A., Meijer, H.J.& Raghoebar, G.M. (2008) Treatment outcome of immediate, early and conventional single-tooth implants in the aesthetic zone: a systematic review to survival, bone level, soft tissue, aesthetics and patient satisfaction. Journal of Clinical Periodontology 35, 1073-1086. Esposito, M., Hirsch, J., Lekholm, U. & Thomsen, P. (1999) Differential diagnosis and treatment strategies for biologic complications and failing oral implants: a review of the literature. International Journal of Oral and Maxillofacial Implants 14, 473-490. Flanagan, D. (2003) External and occlusal trauma to dental implants and a case report. Dental Traumatology 19, 160-164. Jung, R.E., Pjetursson, B.E., Glauser, R., Zembic, A., Zwahlen, M. & Lang, N.P. (2008) A systematic review of the 5-year survival and complication rates of implant-supported single crowns. Clinical Oral Implant Research 19, 119-130. Khraisat, A., Abu-Hammad, O., Al-Kayed, A.M. & Dar-

122

Odeh, N. (2004) Stability of the implant/abutment joint in a single-tooth external-hexagon implant system: clinical and mechanical review. Clinical Implant Dentistry and Related Research 6, 222-229. Khraisat, A. (2005) Stability of implant-abutment interface with a hexagon-mediated butt joint: failure mode and bending resistance. Clinical Implant Dentistry and Related Research 7, 221-228. Nagasawa, S., Hayano, K., Niino, T., Yamakura, K., Yoshida, T., Mizoguchi, T. & et al. (2008) Nonlinear stress analysis of titanium implants by finite element method. Journal of Dental Materials 27, 633-639. Norton, M.R. (2000) In vitro evaluation of the strength of the conical implant-to-abutment joint in two commercially available implant systems. Journal of Prosthetic Dentistry 83, 567-571. Piattelli, A., Scarano, A., Favero, L., Iezzi, G., Petrone, G. & Favero, G.A. (2003) Clinical and histologic aspects of dental implants removed due to mobility. Journal of Periodontology 74, 385-390. Silva, N.R., Nourian, P., Coelho, P.G., Rekow, E.D. & Thompson, VP. (2009) Impact Fracture Resistance of two Titanium-Abutment Systems Versus a Single-Piece Ceramic Implant. Clinical Implant Dentistry and Related Research 3, [Epub ahead of print]. Steinebrunner, L., Wolfart, S., Ludwig, K. & Kern M. (2008) Implant-abutment interface design affects fatigue and fracture strength of implants. Clinical Oral Implant Research 19, 1276-1284. Strub, J.R. & Gerds, T. (2003) Fracture strength and failure mode of five different single-tooth implant-abutment combinations. International Journal of Prosthodontics 16, 167-171. Stuebinger, S., Hodel, Y. & Filippi, A. (2004) Trauma to anterior implants. Dental Traumatology 20, 169-171.

7

123 Trauma case

8. General discussion

The application of a dental implant to replace an anterior tooth is challenging. One should not only strive to rehabilitate function, but also to restore the aesthetics represented by the appearance of the implant crown and the peri-implant mucosa. Besides, as holds for all implant cases, the tissue surrounding the implant should remain healthy and stable over time for good long-term prognosis. From the broad spectrum of materials and techniques available in aesthetic implant dentistry, this thesis inquired into two aspects, namely the design of the implant neck and the concept of immediate implant loading. Radiographic, clinical and aesthetic outcome measures together with patient satisfaction were assessed reflecting the quality of the final outcome. In this chapter the main research outcomes are discussed. In the last paragraphs, clinical implications and suggestions for future research are given.

Chapter

8

Evidence from literature on single-tooth implants in the aesthetic zone A systematic review of the literature was performed to gain insight into the available evidence on the efficacy of using an implant to replace a missing anterior tooth (Chapter 2). In this review, we focussed on single implants neighboured by natural teeth that had been inserted to replace a missing tooth in the aesthetic zone (defined as the region from teeth 15-25 and teeth 35-45). The included studies suggest that such a therapy will lead to a successful outcome on, at least, the short term with regard to implant survival, marginal peri-implant bone loss and incidence of complications. A meta-analysis revealed an implant survival rate of 95.5 % after one year (based on 19 studies) and only a little amount of marginal bone loss at one year after definitive crown placement (0.20 mm, based on five studies). A low number of complications was reported, most of which were minor and could be solved non-invasively. These favorable results need closer scrutiny, since the available literature showed several shortcomings. First, studies on single-tooth implants in the aesthetic zone underexposed significant variables as soft tissue aspects, aesthetic outcome and patient satisfaction. Variables reflecting the condition of the peri-implant mucosa as probing pocket depth, bleeding on probing and plaque indices were lacking in most of the studies. Furthermore, the few studies that did evaluate soft tissue appearance made use of the papilla index according to Jemt (1997) to express the volume of the interproximal papillae or assessed the level of the facial peri-implant mucosa. Although these outcome measures contribute to the final aesthetic outcome, other aesthetically relevant items as soft tissue colour, texture and contour were not taken into account. To assess the aesthetic outcome, all aesthetically relevant aspects should be considered. For this purpose, objective rating instruments as the Implant Crown Aesthetic Index (Meijer et al. 2005) and the Pink Esthetic Score –White Esthetic Score (Belser et al. 2009) were introduced. 126

Single-tooth implants with different neck designs in the aesthetic zone The aim of this study, as described in chapters 3 and 4, was to compare the outcome of single-tooth implants in the maxillary aesthetic zone (from teeth 14 - 24) with three different neck designs, namely a smooth ‘machined’ neck (‘smooth group’), a rough neck with grooves (‘rough group’) and a scalloped neck with grooves (‘scalloped group’). Variables were marginal bone level change, clinical and aesthetic outcome measures and patient satisfaction.

Marginal bone level change After implant placement and through time of function, it is commonly accepted that implants will display some extent of bone loss (Albrektsson et al. 1986, Laurell & Lundgren 2009). We considered loss of peri-implant marginal bone measured radiographically as being an important outcome measure expressing the quality of the treatment outcome. First, marginal bone loss may induce pocket formation which could be unfavorable for long-term health of the peri-implant tissues (Rams et al. 1984, Heydenrijk et al. 2002). Second, loss of peri-implant marginal bone might result in recession of the peri-implant mucosal level (Bengazi et al. 1996, Chang et al. 1999b, Hermann et al. 2001a) thereby affecting the aesthetic outcome. Measurement of marginal bone on peri-apical radiographs is generally accepted 127

General discussion

Besides the aesthetics of the mucosa, these indexes also contemplate the aesthetics of the implant crown. The design of the included studies should be considered as another shortcoming. There was a lack of well-designed clinical trials and most of the studies could be classified as case series. Since case series are prone to selection bias, results of these studies should be interpreted with caution. Furthermore, in most of the studies, sample sizes were small and follow-up periods were too short to draw firm conclusions regarding the treatment outcome of single implant therapy on the long term. From the perspective of these abovementioned shortcomings, it seems paradoxical that instead of establishing conventional treatment strategies, most of the studies inquired into protocols where implants were inserted in fresh or early healed extraction sites or were subjected to immediate or early loading. Despite promising results for this variety of studies, there was too little evidence to answer the question whether all these treatment strategies will result in a comparable – or even better – outcome than the conventional procedures. Unfortunately, no clinical trials could be retrieved focussing on different implant types or different implant neck designs in particular.

8

Chapter

8

as a reliable and feasible instrument to measure bone loss at least at the proximal side of the implant (Hermann et al. 2001b, Salvi & Lang 2004) and offers fixed reference points from the moment of implant placement to years thereafter, allowing for longitudinal research. Since it is known that peri-implant bone loss occurs circumferentially thus at the facial and palatal aspects as well (Buser et al. 2004, Cardaropoli et al. 2006), radiographic bone loss observed at the proximal implant side might be a measure for bone loss at the facial and palatal sides as well. In our study, implants with a scalloped implant neck displayed significantly more peri-implant bone loss from implant placement up to the end of follow up (18 months after implant placement; 2.01 ± 0.77 mm) than the implants with a smooth (1.19 mm ± 0.82 mm) and rough neck (0.90 ± 0.57 mm) but with common flat platforms (Chapter 3). Unfortunately, studies on the scalloped implant are scarce and clinical trials are lacking, which limits a comparison of our results with results from the literature. The available publications are in line with our findings since values of 1.5 to 2.1 mm bone loss (standard deviations around 1 mm) between implant placement and 12 months thereafter were reported (Nowzari et al. 2006, Kan et al. 2007, McAllister 2007). We do not have a clear explanation for the amount of bone loss in the scalloped group as observed in our study. One reason might be that peri-implant bone is mainly formed in a horizontal plane. As a result, the more crestally related facial and palatal part of the implant platform dictates the marginal bone level around the implant. Another reason could be inferred from a biomechanical point of view. Too much stress at the implant neck after loading, might induce initial marginal bone resorption (Oh et al. 2002; Schrotenboer et al. 2008). Possibly, the stress distribution from the scalloped implant to the bone was unfavorable and too high, leading to the amount of marginal bone loss as was observed during the first evaluation period. In this context, the complex connection between implant and abutment could play a role. Several studies demonstrated that a rough surface topography at the implant neck exhibit less marginal bone resorption than a smooth coronal area (Shin et al. 2006, Bratu et al. 2009, Nickenig et al. 2009) and that (micro)threads at the level of the implant neck have the quality to preserve marginal bone (Palmer et al. 2000, Shin et al. 2006, Lee et al. 2007). In contrast to these observations, we could not detect a significant difference in bone loss between implants with a rough or smooth neck (Chapter 3). However, since the abovementioned studies retrieved data mostly from posterior tooth replacements or from non-clinical research, it is questionable whether these data can be extrapolated to our human study involving maxillary teeth in the aesthetic zone. Unfortunately, clinical trials investigating smooth and rough implant neck architectures for anterior singletooth replacements are lacking. 128

Clinical outcome At 18 months post-implant placement, significantly deeper pocket depths were measured in the scalloped group together with higher bleeding scores compared to the other study groups (Chapter 3). This is not a surprising finding when taking into consideration the higher amount of marginal bone loss in the scalloped group and the positive correlation that was found between pocket depth and marginal bone level alterations. From 6 to 18 months, pocket depths and bleeding scores increased significantly in the scalloped group, while in this evaluation period only a small amount of marginal bone loss was observed in this study group. Apparently, the peri-implant tissues in the scalloped group developed more marginal inflammation with time as confirmed by the higher bleeding scores. As described by Schou et al. (2002), even a mild marginal inflammation is associated with a deeper penetration of the probe. This might be a reason that deeper pockets depths were measured at 18 months of follow-up, without 129

General discussion

Since in our study the implant-abutment interface was closely related to the bone crest (all implant necks were leveled with the bone crest at the time of implant placement), it might be possible that the thought beneficial effect of a rough implant neck, could not be effectuated at a level surpassing the bone resorption around a smooth implant neck. This hypothesis is in line with suggestions from the literature mentioning that the position of the implant-abutment interface relative to the bone crest at the time of implant placement is a significant factor determining marginal bone loss (Hermann et al. 2000, Broggini et al. 2006, Jung et al. 2008). An inflammatory reaction at the implant-abutment interface due to microbial leakage seems to be a major factor for this bone loss. A more apical position of the implant-abutment interface is thought to be a factor increasing the inflammatory reaction (Broggini et al. 2006). Furthermore, a zone of connective tissue will form between the bone crest and the inflammatory cell infiltrate at the implant-abutment interface at the cost of marginal bone (Schwarz et al. 2008). Other implant features might also be important in preventing bone loss. It has been suggested that besides surface roughness and grooves, a conical internal implant-abutment connection combined with a non-matching implant-abutment diameter favor marginal bone preservation (Wennstrom et al. 2005, Jung et al. 2008, Cochran et al. 2009). It seems that by reducing the diameter of the abutment, the implant-abutment interface and thereby the inflammatory reaction will be displaced further away from the bone, resulting in less marginal bone loss. Furthermore, an internal conical connection has been associated with a more stable connection possibly leading to less bacterial leakage and a better stress distribution (Hansson 2003, Coelho et al. 2008, Cochran et al. 2009). However, the beneficial effects of such connections need further clinical investigation.

8

Chapter

8

observing a concordant loss of marginal bone loss. Furthermore, inflammationinduced swelling of the peri-implant mucosa might have resulted in increased pockets depth (‘pseudo-pocket’). Although there is no evidence showing a correlation between pocket depth and the presence or absence of active peri-implant disease (Schropp et al. 2005b, Heitz-Mayfield 2008), it has been shown that with increasing pocket depth, an environment is created for periodontal pathogens (Rams et al. 1984, Heydenrijk et al. 2002). We therefore believe that peri-implant pocket depths should be limited and remain stable over time to facilitate healthy peri-implant tissues. The long-term influence of increased pocket depth on marginal bone levels needs further study as applies to the interaction between marginal bone loss and pocket formation. After placement of the definitive crown (6 months post-implant placement) to 1 year thereafter (18 months post-implant placement) the levels of the mid-facial peri-implant mucosa remained stable (Chapter 3). This corresponded to the small amount of marginal bone loss observed in this period. Despite this small amount of bone loss, the level of the papillae gained some height after definitive crown placement (overall 0.22 mm). The capacity of papillae to exhibit regrowth after crown placement has also been observed in other single-tooth implant studies (Jemt & Lekholm 2003, Schropp et al. 2005a, Den Hartog et al. 2008, Meijndert et al. 2008). The study by Meijndert et al. (2008) in which a comparable restoration procedure and the same evaluation strategy were used, reported a comparable gain in papillary height of 0.25 mm. To elucidate the effect of marginal bone loss on the level of the mucosa around anterior single-tooth implants, it would have been of interest to compare the total amount of bone loss after 18 months with the total change in peri-implant mucosal level. However, changes of the peri-implant mucosal level can only be measured accurately after placement of the definitive crown (i.e. after six months post-implant placement) since thereafter the actual peri-implant mucosal level is established. After definitive crown placement, only minor marginal bone loss and a concordant change in peri-implant mucosal level was observed. Since the most bone loss already occurred during the first evaluation period, the true effect of bone loss on the peri-implant mucosal level might have been missed. Scalloped implants were accompanied by more complications of the definitive crown, viz. porcelain fracture (six cases) and mobility (three cases), than the other implants (Chapter 3). The complex connection between the scalloped implant neck and abutment might have been a major factor determining these complications. However, long-term follow-up is needed to unveil the stability of the prosthetic restorations as the problems with the scalloped implant restorations might mainly be an early phenomenon. In the line of complications, an interesting phenomenon we encountered was a 130

Aesthetic outcome and patient satisfaction To assess the aesthetic outcome, objective rating instruments are available, to be used by dental professionals. These instruments are composed of different aesthetically related items based on the anatomic form, colour and surface characteristics of the peri-implant mucosa and implant crown. Such instruments facilitate instant or longitudinal assessment of the aesthetic outcome of different treatment strategies and can be of value for a thorough analysis of the final outcome in order to improve treatment aspects. However, since the patient is the final user of implant therapy, the opinion of the patient is also of importance. Questionnaires to be completed by the patient are commonly employed to assess the subjective appreciation of the aesthetic outcome. To our best knowledge, only two aesthetic rating instruments are nowadays available to assess the aesthetics of the peri-implant mucosa and implant crown (Meijer et al. 2005, Belser et al. 2009). In our study, both these instruments were used, knowing that these instruments are not yet optimal. A major drawback is that these instruments are not suitable to assess the pre-operative situation as well. When the pre-operative situation can be assessed, this might be of value to better understand the possible role of factors determining the final aesthetic outcome. Furthermore, the instruments are not yet tested for their external validity and with respect to their internal validity, further development is necessary to improve the reproducibility (as discussed in Chapter 4). The same applies to the development of validated questionnaires to assess patient (aesthetic) satisfaction. Nowadays, no such questionnaires are available. Beforehand, we hypothesized that the design of the implant neck might have an effect on the level of the peri-implant mucosa and with that influences the final aesthetic outcome. However, using both the available aesthetic evaluation instruments (Meijer et al. 2005, Belser et al. 2009), this effect could not be shown in our study (Chapter 4). Although the scalloped implants displayed more radiographic marginal bone loss, there were no differences between study groups regarding the items ‘level of the facial peri-implant mucosa’ and ‘quantity of papillary tissue’ (both these items are part of the aesthetic evaluation instruments). There are some possible reasons for not observing between-group differences 131

General discussion

trauma to an implant crown in one of our patients allocated to the smooth group (Chapter 7). It appeared that only the fixation screw was damaged, while the implant, restoration and peri-implant tissues remained unharmend. Just an easy prosthetic retreatment was neccesary and a surgical retreatment was prevented. We realize that the incidence of trauma to implant restorations is not high. However, we favor designing suprastructures as such that these structures are the weakest link in case of trauma, thereby preserving the implant and surrounding tissue.

8

Chapter

8

on these items despite between-group differences in marginal bone loss. First, it might be that the difference in marginal bone resorption between the scalloped group and the other study groups brought about a clinical effect that was too little to be observed with the aesthetic indexes we applied or that the indexes itself were not able to reveal these differences (e.g., because of the shortcomings as discussed earlier). A second reason might be ascribed to the role of the periodontium of the adjacent teeth. Namely, it is assumed that the level of the papilla is related to the bone level next to the adjacent teeth (Choquet et al. 2001, Kan et al. 2003, Romeo et al. 2008). We observed only minor marginal bone loss at the adjacent teeth without differences between study groups. Possibly, the periodontium of the adjacent teeth also acts on the level of the facial peri-implant mucosa. Finally, we believe that the role of the pre-operative situation for the final aesthetic outcome needs discussion. Possibly, the level of the mucosa before implant placement was more relevant to the future level of the peri-implant mucosa than is the amount of bone loss around the implant neck. In our study, all implants were placed in healed extraction sites, up to a third of which were augmented in a separate session before implant placement. It revealed that in 63% of the cases, the level of the facial peri-implant mucosa showed a deviation when compared to the adjacent dentition. It is known that after tooth removal, the walls of the alveolus undergo substantial resorption at the facial aspect, affecting the anatomy of the soft tissue (Schropp et al. 2003a, Araujo & Lindhe 2005). A strategy of immediate or early implant placement or a socket preservation technique might favor the aesthetic outcome. By way of comparison, in other studies (Belser et al. 2009, Buser et al. 2009) in which implants were installed in early healed extraction sites and subjected to simultaneous guided bone regeneration, the level of the facial peri-implant mucosa showed a deficiency in only 22 % and 10% of the cases, res­ pectively. As discussed earlier, it would be helpful to further develop an aesthetic evaluation instrument, by which the pre-operative situation can be assessed as well. This will facilitate a further exploration of predisposing factors. Although from a professional’s perception the appearance of the peri-implant mucosa and implant crown were not acceptable in, respectively, 40% and 20 % of the overall cases, the subjective aesthetic appreciation of the patient was high. T�������������������������������������������������������������������������� he discrepancy ����������������������������������������������������������������������� between the aesthetic outcome from a professional’s and patient’s perception has been reported in earlier studies (Chang et al. 1999a, Meijndert et al. 2007, Esposito et al. 2009). As suggested by Chang (Chang et al. 1999a), it might be that factors considered by professionals to be relevant for the aesthetic outcome may not be of decisive importance for patient’s aesthetic satisfaction. Furthermore, we argue that for the final appreciation of the patient, the pre-operative situation plays a role of significance and gives weight to the final judgment. When the pre-operative situation is compromised and patient’s 132

Immediate loading of single-tooth implants in the aesthetic zone The objective of this study was to compare the outcome of immediate loading with that of conventional loading of implants applied for a missing anterior maxillary tooth for radiographic marginal bone level change and clinical and aesthetic outcome measures together with patient satisfaction (Chapter 5). We hypothesized that immediate loading is not inferior to conventional loading.

Marginal bone level change It seems rational to argue that immediate loading might induce more marginal peri-implant bone loss than conventional loading, since immediate loading might induce a more uneventful healing of the surrounding peri-implant bone. However, no differences were observed between immediate and conventional loading regarding marginal bone loss at 6 and 18 months post-implant placement. This is in agreement with recent studies on immediate and conventional single-tooth implants in the anterior zone (Hall et al. 2007, Den Hartog et al. 2008, Degidi et al. 2009). Clinical outcome Studies on immediate loading have often considered implant survival as the primary outcome measure. This is, however, only one outcome variable reflecting a succeeding therapy. In our study, survival rates were 96.8% for the immediate group (one implant failed) and 100% for the conventional group. These high survival rates were confirmed by other studies on immediately loaded implants, even when inserted in fresh extraction sockets (Den Hartog et al. 2008). It should be realized that the sample size of our study was too small to demonstrate whether immediate loading was non-inferior to conventional loading with respect to implant survival. Additional (long-term) studies would be helpful to draw firm conclusions regarding the potential hazardous effect of immediate loading on implant survival. It is important to reach sufficient primary implant stability before performing immediate loading. It has been observed that in addition to the anatomy of the bone (Mesa et al. 2008, Roze et al. 2009) and preparation technique (Tabassum 133

General discussion

expectations are realistic, patients ����������������������������������������������� might be satisfied even when the aesthetic outcome according to an objective index is poor. The aesthetic indexes do not take the preoperative situation into account as discussed before. The high general patient satisfaction we observed might be deduced from the patient’s appreciation with the aesthetics, since the outcome of all questions was correlated with general patient satisfaction. However, it should be noticed that also other aspects as function and comfort might contribute to general patient satisfaction.

8

Chapter

8

et al. 2010), the geometry (O’Sullivan et al. 2004, Dos Santos et al. 2009) and length of the implant (Mesa et al. 2008) are factors influencing primary stability. In our study, almost all implants were 16 mm in length, the longest available for the type of implant we used. Furthermore, the implants had a rough surface topography and a tapered design, both favoring primary implant stability (O’Sullivan et al. 2004, Dos Santos et al. 2009). It might be attributed to these factors that in our study there were no difficulties to reach primary implant stability. Besides paying attention to sufficient primary stability as being a ‘conditio sine qua non’ for immediate loading, it is also important to carefully instruct the patient and to pay attention to the occlusion of the provisional crown. In our study, all provisional crowns were free from centric and eccentric occlusal contacts with the antagonist teeth. With respect to the health of the peri-implant tissue expressed in probing depth, bleeding upon probing and amount of plaque, no differences were noticed between the immediate and conventional study group. The implants showed deeper probing pockets depths than the adjacent teeth (as also was observed in the implant neck study Chapter 3). Such deeper pocket depths around singletooth implants have been reported in another study from our research group (Meijndert et al. 2008). It is argued that this difference in probing depth between implants and natural teeth, might be partly ascribed to the anatomy of the periimplant mucosa and its attachment to the implant surface, being different compared to the anatomy of the gingiva and its attachment to the root surface (Berglundh et al. 1991). It was demonstrated that these differences had an impact on probing depth measurements, since the gingiva was more resistant to probing forces than the mucosal seal around implants (Ericsson & Lindhe, 1993). Another interesting finding was the high number of implants displaying bleeding upon probing. At 18 months post-implant placement, most of the implants showed bleeding upon probing (around 80% of the implants versus 30% of the adjacent teeth, including the implants from the implant neck study). Unfortunately, data from other relevant studies on this topic are scarce and contradictory values are reported (Den Hartog et al. 2008). Besides, bleeding index scores were presented in percentages as well as in mean values or the unit of analysis differed (per implant or per implant side). Since bleeding on probing indicates presence of inflammation in the peri-implant mucosa (Heitz-Mayfield 2008), the significance of this variable as predictor for the long-term prognosis needs further investigation.

Aesthetic outcome and patient satisfaction There is growing evidence that immediate loading of implants inserted in fresh extraction sockets would lead to more favorable soft tissue levels compared to a 134

Principal findings and clinical implications The general aims of our study were to compare the outcome of single implants with different neck designs applied to replace a missing anterior tooth in the maxilla and to compare the outcome of immediate loading with conventional loading, again for implants replacing a missing tooth in the anterior maxilla. First, we assessed the treatment outcome of single-tooth implants in the maxillary aesthetic zone with three different implant neck designs, namely a 1.5 mm smooth implant neck (‘smooth group’), a moderately rough implant neck with grooves (‘rough group’) and a scalloped moderately rough implant neck with grooves (‘scalloped group’). At 18 months post-implant placement, the scalloped group showed significantly more marginal bone loss, deeper probing pocket depths and higher bleeding scores than the smooth group and rough group, while there were no differences in outcome between the smooth group and rough group. Besides, the implants in the smooth and rough groups revealed favorable treatment outcomes in terms of bone loss, implant survival, complications and soft tissue aspects, which are in line with values reported in other studies on single-tooth implants placed in the anterior maxilla (Den Hartog et al. 2008). Although there were no differences in aesthetic outcome between the three dif135

General discussion

delayed strategy (Block et al. 2009, De Rouck et al. 2009). These studies reported that ������������������������������������������������������������������������������ immediate stabilization of the soft tissue after tooth removal by means of immediate implant placement and immediate placement of the provisional crown, would result in 0.75 to 1 mm more soft tissue preservation mid-facially. In our study, all implants were inserted in healed sites as was common those days. As pointed out earlier, tooth removal induces resorption of the walls of the alveolus affecting the soft tissue anatomy (Schropp et al. 2003b, Araujo & Lindhe 2005). It could be that for healed sites, a potential positive effect of an immediate (provisional) crown on soft tissue preservation subsided. When using the aesthetic evaluation instruments to express soft tissue aesthetics, at least no significant difference between immediate and conventionally loaded implants was observed. The same applied to the volume of the papilla assessed with the papilla index. General patient satisfaction was high in both study groups and patients were satisfied regarding function, aesthetics and treatment procedure. Other studies on anterior single-tooth implants reported comparable overall satisfaction scores of 8.8 and higher (also using VAS) (Schropp et al. 2004, Den Hartog et al. 2008). As confirmed by other studies (Levi et al. 2003, Schropp et al. 2004), a substantial percentage of conventionally treated patients (30%) experienced the healing time of the implant as long. Although Levi et al. (2003) found that treatment time was not a critical factor for overall satisfaction, the shorter treatment time of immediate loading might serve these patients.

8

ferent implants, we suggest the use of implants with a 1.5 mm smooth neck or a rough neck with grooves for single anterior tooth replacements in stead of using implants with a scalloped neck design since the latter implants displayed more bone loss and less clinical performance. Next, we assessed the treatment outcome of immediately loaded single-tooth implants in the aesthetic zone. It revealed that - on the short term - immediate loading will lead to a treatment outcome that is not less favorable than conventional loading. Since the concept of immediate loading shortens treatment time and offers comfort for the patient, this concept should be considered as a promising alternative to conventional loading. However, it should be realized that the concept of immediate loading has to be performed according to a specified protocol paying attention to adequate primary implant stability, a non-occluding provisional crown and careful patient instruction. Moreover, only short term results are available thus far.

Chapter

8 Future research Based on our findings and that of other studies (Hall et al. 2007, Degidi 2009), immediate loading of a single-tooth implant in the aesthetic zone can be considered as an effective treatment strategy on the short term. Additional studies are needed to investigate the efficacy of immediate loading on the long-term, before immediate loading can indeed be considered as an at least equal treatment modality as conventional loading has been shown to be. Next to immediate loading, the promising concepts of immediate and early implant placement after tooth extraction need further study. In our immediate loading study, all implants were installed in healed extraction sites, at least three months after the tooth had been extracted. However, placement of an implant immediately or early after tooth extraction has been posed to be beneficial for preservation of hard and soft tissue. Furthermore, when immediate or early placed implants are subjected to immediate loading, this could offer even more comfort for the patient than just applying immediate loading. In order to gain more insight into preservation of hard and soft tissue after tooth extraction, studies are needed investigating socket preservation techniques and - whether or not - these techniques should be combined with immediate or early implant placement. Socket preservation techniques could, amongst others, enhance the final outcome since collapse of tissue might be prevented and with that a thorough augmentation procedure. As applies to our immediate loading study, additional (long-term) studies are needed to validate the conclusions we draw in our study to different implant neck designs. Furthermore, besides focusing on the topography and geometry of the implant neck, additional research on other material aspects is needed. 136

137

General discussion

For instance, the promising concept of internal conical connections between implant and abutment needs further study as holds for the concept of non-matching implant-abutment diameters (‘platform switching’). An important starting point for future research is that studies should focus on the quality of the outcome, using uniform outcome variables and data presentation. This will ease comparison of studies. In order to compare different types of interventions, clinical trials are needed with sufficiently large study populations and random allocation procedures. Furthermore, we believe that it would be helpful to consider the pre-operative situation and its relation to the final outcome as well. When taking the pre-operative situation into account too, the true effect of an intervention on the final outcome might be determined with more accuracy meanwhile reducing the difference in treatment outcome as rated by the clinician (who now just rates the appearance of the crown and soft tissue) and the patient (who also includes the baseline characteristics in his ratings). With regard to the measurement instruments, efforts should be made to further develop an objective aesthetic rating instrument with good internal and external validity, to be commonly used in implant research. The present aesthetic rating instruments are only tested for their reproducibility and do not take the pre-operative situation into account. The same applies to the development of a validated questionnaire assessing patient satisfaction. Finally, upcoming instruments as three-dimensional imaging techniques could be brought into new research projects. With such measurement instruments, the effect of an intervention on the hard and soft peri-implant tissues can be assessed in all dimensions with more ease and probably with more accuracy. It is foreseen that, through further research, more insight will be obtained into the efficacy and efficiency of implant treatment strategies to replace a missing anterior tooth. This will favor the ultimate ambition to strive for, viz. efficient creation of a high quality restoration for the long term, satisfying the criteria that reflect function and aesthetics.

8

References Albrektsson, T., Zarb, G., Worthington, P. & Eriksson, A.R. (1986) The long-term efficacy of currently used dental implants: a review and proposed criteria of success. International Journal of Oral and Maxillofacical Implants 1, 11-25. Araujo, M.G. & Lindhe, J. (2005) Dimensional ridge alterations following tooth extraction. An experimental study in the dog. Journal of Clinical Periodontology 32, 212-218.

8

Bengazi, F., Wennstrom, J.L. & Lekholm, U. (1996) Recession of the soft tissue margin at oral implants. A 2-year longitudinal prospective study. Clinical Oral Implants Research 7, 303-310.

Chapter

Belser, U.C., Grutter, L., Vailati, F., Bornstein, M.M., Weber, H.P. & Buser, D. (2009) Outcome evaluation of early placed maxillary anterior single-tooth implants using objective esthetic criteria: a cross-sectional, retrospective study in 45 patients with a 2- to 4-year follow-up using pink and white esthetic scores. Journal of Periodontology 80, 140-151.

Berglundh, T., Lindhe, J., Ericsson, I., Marinello, C.P., Liljenberg, B. & Thomsen, P. (1991) The soft tissue barrier at implants and teeth. Clinical Oral Implants Research 2, 81-90. Block, M.S., Mercante, D.E., Lirette, D., Mohamed, W., Ryser, M. & Castellon, P. (2009) Prospective evaluation of immediate and delayed provisional single tooth restorations. Journal of Oral and Maxillofacial Surgery 67, 89-107. Bratu, E.A., Tandlich, M. & Shapira, L. (2009) A rough surface implant neck with microthreads reduces the amount of marginal bone loss: a prospective clinical study. Clinical Oral Implants Research 20, 827-832. Broggini, N., McManus, L.M., Hermann, J.S., Medina, R., Schenk, R.K., Buser, D. & Cochran, D.L. (2006) Periimplant inflammation defined by the implant-abutment interface. Journal of Dental Research 85, 473-478. Buser, D., Martin, W. & Belser, U.C. (2004) Optimizing esthetics for implant restorations in the anterior maxilla: anatomic and surgical considerations. International Journal of Oral and Maxillofacial Implants 19 Suppl, 43-61. Buser, D., Halbritter, S., Hart, C., Bornstein, M.M., Grutter, L., Chappuis, V. & Belser, U.C. (2009) Early implant placement with simultaneous guided bone regeneration following single-tooth extraction in the esthetic zone: 12-month results of a prospective study with 20 consecutive patients. Journal of Periodontology 80, 152-162. Cardaropoli, G., Lekholm, U. & Wennstrom, J.L. (2006) Tissue alterations at implant-supported single-tooth replacements: a 1-year prospective clinical study. Clinical Oral Implants Research 17, 165-171.

138

Chang, M., Odman, P.A., Wennstrom, J.L. & Andersson, B. (1999a) Esthetic outcome of implant-supported single-tooth replacements assessed by the patient and by prosthodontists. International Journal of Prosthodontics 12, 335-341. Chang, M., Wennstrom, J.L., Odman, P. & Andersson, B. (1999b) Implant supported single-tooth replacements compared to contralateral natural teeth. Crown and soft tissue dimensions. Clinical Oral Implants Research 10, 185-194. Choquet, V., Hermans, M., Adriaenssens, P., Daelemans, P., Tarnow, D.P. & Malevez, C. (2001) Clinical and radiographic evaluation of the papilla level adjacent to single-tooth dental implants. A retrospective study in the maxillary anterior region. Journal of Periodontology 72, 1364-1371. Cochran, D.L., Bosshardt, D.D., Grize, L., Higginbottom, F.L., Jones, A.A., Jung, R.E., Wieland, M. & Dard, M. (2009) Bone response to loaded implants with non-matching implant-abutment diameters in the canine mandible. Journal of Periodontology 80, 609-617. Coelho, P.G., Sudack, P., Suzuki, M., Kurtz, K.S., Romanos, G.E. & Silva, N.R. (2008) In vitro evaluation of the implant abutment connection sealing capability of different implant systems. Journal of Oral Rehabilitation 35, 917-924. De Rouck, T., Collys, K., Wyn, I. & Cosyn, J. (2009) Instant provisionalization of immediate single-tooth implants is essential to optimize esthetic treatment outcome. Clinical Oral Implants Research 20, 566-570. Degidi, M., Nardi, D. & Piattelli, A. (2009) Immediate versus one-stage restoration of small-diameter implants for a single missing maxillary lateral incisor: a 3-year randomized clinical trial. Journal of Periodontology 80, 1393-1398. Den Hartog, L., Slater, J.J., Vissink, A., Meijer, H.J. & Raghoebar, G.M. (2008) Treatment outcome of immediate, early and conventional single-tooth implants in the aesthetic zone: a systematic review to survival, bone level, soft-tissue, aesthetics and patient satisfaction. Journal of Clinical Periodontology 35, 1073-1086. Dos Santos, M.V., Elias, C.N. & Cavalcanti Lima, J.H. (2009) The Effects of Superficial Roughness and Design on the Primary Stability of Dental Implants. Clinical Implant Dentistry and Related Research [Epub ahead of print]. Ericsson, I. & Lindhe, J. (1993) Probing depth at implants and teeth. An experimental study in the dog. Journal of Clinical Periodontology 20, 623-627. Esposito, M., Grusovin, M.G. & Worthington, H.V. (2009) Agreement of quantitative subjective evaluation of esthetic changes in implant dentistry by patients and practitioners. International Journal of Oral and Maxillofacical Implants 24, 309-315. Gapski, R., Wang, H.L., Mascarenhas, P. & Lang, N.P.

Grunder, U., Gracis, S. & Capelli, M. (2005) Influence of the 3-D bone-to-implant relationship on esthetics. International Journal of Periodontics and Restorative Dentistry 25, 113-119. Hall, J.A., Payne, A.G., Purton, D.G., Torr, B., Duncan, W.J. & De Silva, R.K. (2007) Immediately restored, single-tapered implants in the anterior maxilla: prosthodontic and aesthetic outcomes after 1 year. Clinical Implant Dentistry and Related Research 9, 34-45. Hansson, S. (2003) A conical implant-abutment interface at the level of the marginal bone improves the distribution of stresses in the supporting bone. An axisymmetric finite element analysis. Clinical Oral Implants Research 14, 286-293. Heitz-Mayfield, L.J. (2008) Peri-implant diseases: diagnosis and risk indicators. Journal of Clinical Periodontology 35, 292-304. Hermann, J.S., Buser, D., Schenk, R.K. & Cochran, D.L. (2000) Crestal bone changes around titanium implants. A histometric evaluation of unloaded non-submerged and submerged implants in the canine mandible. Journal of Periodontology 71, 1412-1424. Hermann, J.S., Buser, D., Schenk, R.K., Schoolfield, J.D. & Cochran, D.L. (2001a) Biologic Width around one- and two-piece titanium implants. Clinical Oral Implants Research 12, 559-571. Hermann, J.S., Schoolfield, J.D., Nummikoski, P.V., Buser, D., Schenk, R.K. & Cochran, D.L. (2001b) Crestal bone changes around titanium implants: a methodologic study comparing linear radiographic with histometric measurements. International Journal of Oral and Maxillofacical Implants 16, 475-485. Heydenrijk, K., Meijer, H.J., van der Reijden, W.A., Raghoebar, G.M., Vissink, A. & Stegenga, B. (2002) Microbiota around root-form endosseous implants: a review of the literature. International Journal of Oral and Maxillofacical Implants 17, 829-838. Jemt, T. (1997) Regeneration of gingival papillae after single-implant treatment. International Journal of Periodontics and Restorative Dentistry 17, 326-333. Jemt, T. & Lekholm, U. (2003) Measurements of buccal tissue volumes at single-implant restorations after local bone grafting in maxillas: a 3-year clinical prospective study case series. Clinical Implant Dentistry and Related Research. 5, 63-70. Jung, R.E., Jones, A.A., Higginbottom, F.L., Wilson, T.G., Schoolfield, J., Buser, D., Hammerle, C.H. & Cochran, D.L. (2008) The influence of non-matching implant and abutment diameters on radiographic crestal bone levels in dogs. Journal of Periodontology 79, 260-270.

Kan, J.Y., Rungcharassaeng, K., Liddelow, G., Henry, P. & Goodacre, C.J. (2007) Periimplant tissue response following immediate provisional restoration of scalloped implants in the esthetic zone: a one-year pilot prospective multicenter study. Journal of Prosthetic Dentistry 97, S109-S118. Kan, J.Y., Rungcharassaeng, K., Umezu, K. & Kois, J.C. (2003) Dimensions of peri-implant mucosa: an evaluation of maxillary anterior single implants in humans. Journal of Periodontology 74, 557-562. Laurell, L. & Lundgren, D. (2009) Marginal Bone Level Changes at Dental Implants after 5 Years in Function: A Meta-Analysis. Clinical Implant Dentistry and Related Research [Epub ahead of print] Lee, D.W., Choi, Y.S., Park, K.H., Kim, C.S. & Moon, I.S. (2007) Effect of microthread on the maintenance of marginal bone level: a 3-year prospective study. Clinical Oral Implants Research 18, 465-470. Levi, A., Psoter, W.J., Agar, J.R., Reisine, S.T. & Taylor, T.D. (2003) Patient self-reported satisfaction with maxillary anterior dental implant treatment. International Journal of Oral and Maxillofacical Implants 18, 113-120. McAllister, B.S. (2007) Scalloped implant designs enhance interproximal bone levels. International Journal of Periodontics and Restorative Dentistry 27, 9-15. Meijer, H.J., Stellingsma, K., Meijndert, L. & Raghoebar, G.M. (2005) A new index for rating aesthetics of implantsupported single crowns and adjacent soft tissues--the Implant Crown Aesthetic Index. Clinical Oral Implants Research 16, 645-649. Meijndert, L., Meijer, H.J., Raghoebar, G.M. & Vissink, A. (2004). A technique for standardized evaluation of soft and hard peri-implant tissues in partially edentulous patients. Journal of Periodontology 75, 646-651. Meijndert, L., Meijer, H.J., Stellingsma, K., Stegenga, B. & Raghoebar, G.M. (2007) Evaluation of aesthetics of implantsupported single-tooth replacements using different bone augmentation procedures: a prospective randomized clinical study. Clinical Oral Implants Research 18, 715-719. Meijndert, L., Raghoebar, G.M., Meijer, H.J. & Vissink, A. (2008) Clinical and radiographic characteristics of singletooth replacements preceded by local ridge augmentation: a prospective randomized clinical trial. Clinical Oral Implants Research 19, 1295-1303. Mesa, F., Munoz, R., Noguerol, B., Dios Luna, J., Galindo, P. & O’Valle, F. (2008) Multivariate study of factors influencing primary dental implant stability. Clinical Oral Implants Research 19, 196-200. Nickenig, H.J., Wichmann, M., Schlegel, K.A., Nkenke, E. & Eitner, S. (2009) Radiographic evaluation of marginal bone

139

General discussion

(2003) Critical review of immediate implant loading. Clinical Oral Implants Research 14, 515-527.

8

levels adjacent to parallel-screw cylinder machined-neck implants and rough-surfaced microthreaded implants using digitized panoramic radiographs. Clinical Oral Implants Research 20, 550-554. Nowzari, H., Chee, W., Yi, K., Pak, M., Chung, W.H. & Rich, S. (2006) Scalloped dental implants: a retrospective analysis of radiographic and clinical outcomes of 17 NobelPerfect implants in 6 patients. Clinical Implant Dentistry and Related Research 8, 1-10. O’Sullivan, D., Sennerby, L. & Meredith, N. (2004) Influence of implant taper on the primary and secondary stability of osseointegrated titanium implants. Clinical Oral Implants Research 15, 474-480. Oh, T.J., Yoon, J., Misch, C.E. & Wang, H.L. (2002) The causes of early implant bone loss: myth or science? Journal of Periodontology 73, 322-333.

Chapter

8

Schropp, L., Kostopoulos, L., Wenzel, A. & Isidor, F. (2005b) Clinical and radiographic performance of delayedimmediate single-tooth implant placement associated with peri-implant bone defects. A 2-year prospective, controlled, randomized follow-up report. Journal of Clinical Periodontology 32, 480-487. Schropp, L., Wenzel, A., Kostopoulos, L. & Karring, T. (2003a) Bone healing and soft tissue contour changes following single-tooth extraction: a clinical and radiographic 12month prospective study. International Journal of Periodontics and Restorative Dentistry 23, 313-323. Schropp, L., Wenzel, A., Kostopoulos, L. & Karring, T. (2003b) Bone healing and soft tissue contour changes following single-tooth extraction: a clinical and radiographic 12-month prospective study. International Journal of Periodontics and Restorative Dentistry 23, 313-323. Schrotenboer, J., Tsao, Y.P., Kinariwala, V. & Wang, H.L. (2008) Effect of microthreads and platform switching on crestal bone stress levels: a finite element analysis. Journal of

Palmer, R.M., Palmer, P.J. & Smith, B.J. (2000) A 5-year prospective study of Astra single tooth implants. Clinical Oral Implants Research 11, 179-182.

Periodontology 79, 2166-2172.

Rams, T.E., Roberts, T.W., Tatum, H., Jr. & Keyes, P.H. (1984) The subgingival microbial flora associated with human dental implants. Journal of Prosthetic Dentistry 51, 529-534.

Schwarz, F., Herten, M., Bieling, K. & Becker, J. (2008) Crestal bone changes at nonsubmerged implants (Camlog) with different machined collar lengths: a histomorphometric pilot study in dogs. International Journal of Oral and Maxillofacical Implants 23, 335-342.

Romeo, E., Lops, D., Rossi, A., Storelli, S., Rozza, R. & Chiapasco, M. (2008) Surgical and prosthetic management of interproximal region with single-implant restorations: 1-year prospective study. Journal of Periodontology 79, 1048-1055. Roze, J., Babu, S., Saffarzadeh, A., Gayet-Delacroix, M., Hoornaert, A. & Layrolle, P. (2009) Correlating implant stability to bone structure. Clinical Oral Implants Research 20, 1140-1145. Salvi, G.E. & Lang, N.P. (2004) Diagnostic parameters for monitoring peri-implant conditions. International Journal of Oral and Maxillofacical Implants 19 Suppl, 116-127.

Shin, Y.K., Han, C.H., Heo, S.J., Kim, S. & Chun, H.J. (2006) Radiographic evaluation of marginal bone level around implants with different neck designs after 1 year. International Journal of Oral and Maxillofacical Implants 21, 789-794. Tabassum, A., Meijer, G.J., Wolke, J.G. & Jansen, J.A. (2010) Influence of surgical technique and surface roughness on the primary stability of an implant in artificial bone with different cortical thickness: a laboratory study. Clinical Oral Implants Research 21, 213-220. Wennstrom, J.L., Ekestubbe, A., Grondahl, K., Karlsson, S. & Lindhe, J. (2005) Implant-supported single-tooth restorations: a 5-year prospective study. Journal of Clinical Periodontology 32, 567-574.

Schou, S., Holmstrup, P., Stoltze, K., Hjorting-Hansen, E., Fiehn, N.E. & Skovgaard, L.T. (2002) Probing around implants and teeth with healthy or inflamed peri-implant mucosa/gingiva. A histologic comparison in cynomolgus monkeys (Macaca fascicularis). Clinical Oral Implants Research 13, 113-126. Schropp, L., Isidor, F., Kostopoulos, L. & Wenzel, A. (2004) Patient experience of, and satisfaction with, delayed-immediate vs. delayed single-tooth implant placement. Clinical Oral Implants Research 15, 498-503. Schropp, L., Isidor, F., Kostopoulos, L. & Wenzel, A. (2005a) Interproximal papilla levels following early versus delayed placement of single-tooth implants: a controlled clinical trial. International Journal of Oral and Maxillofacical Implant. 20, 753-761.

140

8

141 General discussion

Summary samenvatting dankwoord & cv

summary

Chapter

9

A lost or congenitally missing tooth in the anterior region (‘aesthetic zone’) usually requires prosthetic replacement for functional and aesthetic reasons. The ultimate goal to strive for when restoring a missing anterior tooth is creation of a high quality restoration for the long-term, satisfying the criteria that reflect function and aesthetics. Dental implants have conquered a prominent role in contemporary dentistry when it comes to such replacements. There are, however, factors that could affect the treatment outcome of singletooth implants in the aesthetic zone. E.g., after implant placement and through time of function, it is accepted that some marginal bone around the implant will be lost. The level of the peri-implant marginal bone is related to the level of the peri-implant mucosa, which, in turn, is commonly considered as an important aspect determining the aesthetic outcome. Hence, loss of peri-implant marginal bone could affect the level of the peri-implant mucosa and with that the aesthetic outcome. Furthermore, marginal peri-implant bone loss might induce pocket formation, which could be unfavorable for long-term health of the peri-implant tissue. There is some evidence that the design of the implant neck might influence the amount of peri-implant marginal bone loss. As a result, various implant neck designs have been introduced for maximum preservation of marginal peri-implant bone. Apart from the role of the implant neck design, the concept of immediate loading is object of study in recent implantology. Placement of an implant crown immediately after implant installation offers advantages for the patients compared to a conventional load-free healing period of several months. These include reduction of overall treatment time, avoidance of second-stage surgery and immediate comfort as there is no need for a removable prosthesis during the healing phase. However, immediate loading might also induce more risk, since the implant is disturbed by forces during healing, possibly affecting a successful osseointegration. There is a paucity of well-designed trials addressing the effect of the implant neck design on the outcome of single-tooth implants therapy in the aesthetic zone. The same applies to trials investigating the efficacy of immediate loading of single-tooth implants in the aesthetic zone. Therefore, the general aims of this thesis were to compare the outcome of single-tooth implants in the aesthetic zone with three different neck designs and to compare the outcome of immediate loading with that of conventional loading, also for single-tooth implants in the aesthetic zone. In chapter 2 the available literature on the efficacy of single-tooth implant therapy in the aesthetic zone is systematically reviewed. Studies reporting on implants replacing a missing anterior tooth (region 15-25) with natural adjacent teeth were 144

In chapters 3 and 4, the outcomes of single-tooth implants in the aesthetic zone with three different neck designs are compared for marginal bone level changes, clinical outcome measures, aesthetic outcome and patient satisfaction. A total number of 93 patients with a missing anterior tooth in the maxilla was randomly assigned to be treated with an implant with a 1.5 mm smooth neck (‘smooth group’), with a moderately rough neck with grooves (‘rough group’) or with a scalloped moderately rough neck with grooves (‘scalloped-group’). All implants were installed in healed sites and were loaded after three months with a provisional crown. Three months later, implants were restored with definitive all-ceramic crowns. After implant placement and at 6 and 18 months thereafter, clinical data and standardized radiographs and photographs were collected. Patient satisfaction was explored using a self-administered questionnaire. Chapter 3 focuses on marginal bone level changes and clinical outcome. Significant differences in radiographic marginal bone loss were found between the 145

Summary

considered for inclusion. A distinction was drawn between immediate, early and conventional implant approaches. The methodological quality of eligible studies was assessed by two reviewers independently using specific study-design related assessment forms. Out of 86 primarily selected articles, 19 studies fulfilled the inclusion criteria. Follow-up periods of included studies were relatively short (only four studies had a follow-up duration ≥ five years). A meta-analysis showed an overall implant survival rate of 95.5% (95% CI: [93.0 – 97.1]) after one year and minor marginal bone loss at one year after definitive crown placement (0.20 mm, based on five studies). A stratified meta-analysis revealed no differences in survival between immediate, early and conventional implant strategies. A low incidence of biological and technical complications was found. No differences in outcome measures were reported in clinical trials comparing immediate, early or conventional implant strategies. Unfortunately, no studies could be identified focussing on the effect of different implant neck designs or different implant types. This review demonstrates that promising short-term results can be achieved for immediate, early and conventional single-tooth implant treatment in the aesthetic zone. However, it was found that in literature, important parameters including aesthetic outcome, soft-tissue aspects and patient satisfaction were clearly underexposed. The question whether immediate and early single-tooth implant procedures will result in comparable - or even better - treatment outcomes could not be answered due to lack of well-designed controlled clinical studies. The same applies to the question regarding the effect of the design of the implant neck on the outcome of therapy.

9

Chapter

9

study groups. The scalloped group yielded significantly more radiographic bone loss from implant placement to 18 months thereafter (2.01 ± 0.77 mm) compared to the smooth group (1.19 ± 0.82 mm) and rough group (0.90 ± 0.57 mm). Furthermore, at 18 months follow-up, the scalloped group showed significantly deeper pocket depths and significantly higher bleeding scores. Besides, more complications of technical origin (e.g. porcelain fracture, crown mobility) occurred in the scalloped group during follow-up. Survival rates were 96.8% for the smooth group (1 implant lost) and 100% for the rough and scalloped groups. There were no significant differences in bone loss and clinical outcome between the smooth group and rough group and both these study groups showed favorable results as compared to what has been established in other studies on single-tooth implants in the aesthetic zone. Based on these findings, we recommend the use of either an implant with a 1.5 mm smooth neck or an implant with a rough neck with grooves for anterior single-tooth replacements in stead of using an implant with a scalloped neck design. Chapter 4 focuses on the aesthetic outcome from a professional’s and patient’s perception. On photographs taken at one year after definitive crown placement (18 months post implant placement), the aesthetic outcome was assessed by two professionals using two objective aesthetic indexes (Pink Esthetic Score/White Esthetic Score (PES/WES) and Implant Crown Aesthetic Index (ICAI)). A 5-point Likert scale, ranging from very dissatisfied to very satisfied, was used to assess the aesthetic outcome from a patient’s perception. Furthermore, general patient satisfaction was explored using a Visual Analogue Scale ranging from 0 (very dissatisfied) to 10 (very satisfied). No differences in aesthetic outcome were found between the three implant neck designs. According to the professional’s assessments using the PES/WES and ICAI, respectively 79.3% and 62% of the crowns showed acceptable aesthetics. In 59.8% and 56.5% of the cases, acceptable mucosa aesthetics were found according to PES/WES and ICAI, respectively. A regression analysis showed that a pre-implant augmentation procedure was associated with less favorable objective aesthetics of the mucosa (according to the PES/WES, the most reproducible index). From a patient’s perception, more than 80% of the patients were satisfied about the aesthetic outcome of the crown and mucosa. This finding revealed that there is a discrepancy between the aesthetic appreciation from a professional’s and patient’s perception. General patient satisfaction was high (9.0 ± 1.0 out of a maximum of 10). This study shows that the aesthetic outcome of single-tooth implants in the aesthetic zone appears to be independent on the implant neck designs applied, but dependent on the need for pre-implant augmentation surgery. In chapter 5 it is studied whether immediate loading of anterior single-tooth im146

An immediate loading protocol of an anterior single-tooth implant is described in chapter 6. It is described how the provisional crown was made and how an optimal emergence profile was created by adjusting the provisional restoration. After the provisional phase, an impression was made with an individually fabricated impression post for an accurate reproduction of the established emergence profile. The final crown was a screw-retained all-ceramic crown consisting of an individual zirconia abutment. By implementing this protocol, an optimal definitive result could be achieved together with immediate patient satisfaction. 147

Summary

plants is not inferior to conventional loading. A number of 62 patients with a single missing maxillary anterior tooth was randomly assigned to two study groups. In one study group, patients were treated with an implant that was restored with a non-occluding provisional crown within 24 hours (‘immediate group’). In the other study group, patients were treated with an implant that was restored according to a two-stage procedure at three months after implant placement (‘conventional group’). After the provisional phase, definitive all-ceramic crowns were made. Follow-up visits were conducted after 6 and 18 months post-implant placement. The primary outcome measure of this study was marginal bone level change as measured on standardised radiographs. Non-inferiority of immediate to conventional loading was considered established when the immediately loaded implants showed no more than 0.5 mm of mean marginal bone loss compared to conventionally loaded implants. Other outcome measures were survival, soft tissue aspects (probing pocket depth, plaque, bleeding, peri-implant mucosal level), aesthetic outcome (using PES/WES and ICAI) and patient satisfaction. All implants had good primary stability (≥ 45 Ncm insertion torque). At 18 months post-implant placement, no differences in marginal bone loss were found (immediate group 0.91 ± 0.61 mm, conventional group 0.90 ± 0.57 mm). One implant was lost in the immediate group, three weeks after immediately loaded with a provisional crown. No implants were lost in the conventional group. There were no differences in probing pocket depth, plaque, bleeding and peri-implant mucosal level. Furthermore, the aesthetic outcome and patient satisfaction did not differ between both study groups. Within the limitations of this study (sample size and follow-up duration), we conclude that immediate loading of single-tooth implants in the aesthetic zone is not less favorable than conventional loading. Since the concept of immediate loading offers advantages for the patient, this concept should be considered as a promising alternative to conventional loading. However, the concept of immediate loading has to be performed according to a specified protocol paying attention to adequate primary implant stability, a non-occluding provisional crown and careful patient instruction.

9

In chapter 7 a report of a trauma case is described in which an implant crown in the aesthetic zone was involved. The traumatic impact resulted in a palatal displacement of the implant crown. After careful examination and follow-up, it appeared that only the fixation screw was damaged, while the implant, crown and peri-implant tissues remained unharmed. The implant crown could easily be replaced on the implant using a new fixation screw.

Chapter

9

The main research outcomes are discussed and general conclusions are drawn in chapter 8. It is concluded that for single-tooth replacements in the aesthetic zone, implants with a 1.5 mm smooth neck or a rough neck with grooves display less marginal bone loss and better clinical performance than implants with a scalloped rough neck with grooves. However, there were no differences in aesthetic outcome between the various types of implants studied. Furthermore, we conclude that the outcome of immediate loading of single-tooth implants in the aesthetic zone is not less favorable than conventional loading. Additional followup studies are needed to validate these conclusions for the long-term.

148

Bij het verloren gaan van een gebitselement of wanneer deze nooit is aangelegd, bestaat vaak behoefte aan prothetisch herstel. Dit geldt in het bijzonder wanneer het een gebitselement betreft in het zichtbare deel van het gebit, de zogenaamde esthetische zone. Het ultieme doel van prothetisch herstel is het realiseren van een duurzame kunsttand, die qua functie en esthetiek niet onder doet voor een natuurlijk gebitselement. In de hedendaagse tandheelkunde hebben implantaten een prominente rol verworven bij de vervanging van een ontbrekend gebitselement. Een implantaat is een kunstwortel die in het kaakbot wordt geplaatst en hierin vastgroeit. Op een implantaat kan vervolgens een kroon worden geplaatst, waarmee het ontbrekende gebitselement adequaat is vervangen. Een implantaat die een enkel gebitselement vervangt, wordt ook wel een solitair implantaat genoemd. Nadat een implantaat in het kaakbot is geplaatst, verdwijnt vaak een beetje bot rond de hals van het implantaat. Dit zogenaamde peri-implantaire bot is belangrijk voor de hoogte van het tandvlees rond het implantaat (de peri-implantaire mucosa). Wanneer peri-implantair bot verloren gaat, kan de peri-implantaire mucosa zich terugtrekken. Bij de vervanging van een gebitselement in de esthetische zone, is niet alleen het uiterlijk van de kroon van belang, maar ook het uiterlijk van het omliggende tandvlees. Immers, bij lachen en praten is het tandvlees in de esthetische zone soms zichtbaar. Wanneer de peri-implantaire mucosa zich terugtrekt en qua niveau afwijkt van het tandvlees rond de natuurlijke tanden, resulteert dit in een minder fraai esthetisch resultaat. Verder kan verlies van marginaal peri-implantair bot leiden tot een diepere pocket tussen het implantaat en de peri-implantaire mucosa. Een pocket is een spleet tussen de peri-implantaire mucosa en het implantaat, die ook aanwezig is tussen natuurlijke gebitselementen en tandvlees. Als de pocket dieper wordt, kan dit leiden tot minder gezond peri-implantair weefsel, omdat schadelijke bacteriën beter gedijen in diepere pockets. Het is aangetoond dat de vorm en oppervlaktestructuur van de hals van het implantaat van invloed zijn op het verlies aan peri-implantair bot en dat bij sommige typen implantaathalzen minder peri-implantair botverlies optreedt. Deze bevinding heeft geleid tot de introductie van diverse typen implantaathalzen voor maximaal behoud van het peri-implantaire bot. Naast het type implantaathals, heeft het concept van direct belasten de aandacht in de hedendaagse implantologie. Bij dit concept wordt kort nadat het implantaat in het kaakbot is geplaatst, een kroon op het implantaat gezet (binnen 48 uur voor de benaming ‘direct belasten’). Het implantaat wordt dus via de kroon direct belast, bijvoorbeeld door contact met voedsel en druk van de lip en tong. Dit in tegenstelling tot het gebruikelijke concept van conventioneel be149

Samenvatting

samenvatting

9

Chapter

9

lasten, waarbij het implantaat gedurende drie maanden ongestoord vastgroeit. Daarna volgt plaatsing van de kroon op het implantaat. Direct belasten biedt voordelen voor de patiënt, zoals een kortere behandelduur en direct comfort, omdat de kroon direct wordt geplaatst. Echter, het concept van direct belasten brengt ook een risico met zich mee, omdat het implantaat belast wordt tijdens het proces van vastgroeien in het kaakbot. Het implantaat kan hierdoor mogelijk verloren gaan. Tot op heden zijn slechts weinig klinische studies verricht naar solitaire implantaten in de esthetische zone waarbij gekeken werd naar het effect van het type implantaathals op het eindresultaat. Dit geldt tevens voor het resultaat van direct belasten van solitaire implantaten in de esthetische zone. In dit promotieonderzoek is daarom het behandelresultaat van drie verschillende typen implantaathalzen vergeleken bij solitaire implantaten in de esthetische zone. Daarnaast is het concept van direct belasten onderzocht, wederom toegepast bij solitaire implantaten in de esthetische zone. Dit concept is vergeleken met het behandelresultaat van conventioneel belasten. Hoofdstuk 2 betreft een systematische literatuurstudie naar het resultaat van implantaten in de esthetische zone (tot de tweede premolaar). Studies naar de uitkomsten van solitaire implantaten geplaatst tussen twee natuurlijke buurelementen kwamen in aanmerking voor inclusie. Er werd onderscheid gemaakt tussen solitaire implantaten die direct, vroeg (< drie maanden na implanteren) of conventioneel werden belast. De methodologische kwaliteit van geschikte studies werd beoordeeld door twee beoordelaars, onafhankelijk van elkaar en aan de hand van een vaste set criteria. Van de 86 primair geselecteerde artikelen, bleken 19 studies te voldoen aan de vooraf opgestelde in- en exclusiecriteria. De follow-up periodes van het merendeel van de geïncludeerde studies bleek relatief kort te zijn; slechts in 4 studies bedroeg de follow-up ≥ vijf jaar). Een meta-analyse liet een implantaat-overlevingspercentage zien van 95,5% na één jaar (95% betrouwbaarheidsinterval 93,0 – 97,1) en bovendien bleek weinig peri-implantair botverlies na plaatsen van de definitieve kroon op te treden (0,20 mm, gebaseerd op vijf studies). Een gestratificeerde meta-analyse toonde geen verschil aan in overleving tussen direct, vroeg en conventioneel belaste implantaten. Er was een lage incidentie van klinische complicaties (b.v. peri-implantitis) en complicaties van technische aard (b.v. breuk van de kroon). Helaas werden geen studies in de literatuur aangetroffen, die het effect van het type implantaathals op het behandelresultaat onderzochten. De conclusie van deze literatuurstudie is dat – in ieder geval voor de korte termijn – de behandelresultaten van zowel direct, vroeg als conventioneel belaste 150

In hoofdstuk 3 en 4 wordt het behandelresultaat beschreven van de toepassing van drie verschillende implantaathalzen bij solitaire implantaten in de esthetische zone. De onderzochte variabelen waren marginaal peri-implantair botverlies, klinisch en esthetisch resultaat, en patiënttevredenheid. Er werden 93 patiënten geïncludeerd met een ontbrekend gebitselement in de esthetische zone. De patiënten werden at random verdeeld over drie studiegroepen voor een behandeling met een implantaat met een 1.5 mm gladde hals (‘gladde groep’), een matigruwe hals met groeven (‘ruwe groep’) of met een gewelfde, matig-ruwe hals met groeven (‘gewelfde groep’). Alle implantaten werden minimaal drie maanden na extractie geplaatst. De implantaten werden na drie maanden voorzien van een tijdelijke kroon. Deze tijdelijke kroon werd na drie maanden vervangen door een volledig keramische definitieve kroon. Direct na plaatsen van het implantaat en na 6 en 18 maanden, werden klinische data verzameld en gestandaardiseerde röntgenopnamen en lichtbeelden gemaakt. De patiënttevredenheid werd onderzocht met behulp van een vragenlijst. In hoofdstuk 3 wordt ingegaan op de variabelen marginaal peri-implantair botverlies en klinisch resultaat. De gewelfde groep vertoonde significant meer marginaal botverlies na plaatsen van het implantaat tot 18 maanden daarna (2.01 ± 0.77 mm) vergeleken met de gladde groep (1.19 ± 0.82 mm) en ruwe groep (0.90 ± 0.57 mm). Verder vertoonden de implantaten in de gewelfde groep significant diepere pocketdiepten, significant meer bloeding na sonderen en werden meer complicaties waargenomen van technische aard (losse kroon, breuk van porselein). De implantaat-overlevingspercentages bedroegen 96,8 % in de gladde groep (één implantaat ging verloren) en 100% in de ruwe en gewelfde groep. Tussen de gladde groep en ruwe groep waren geen significant verschillen in botverlies en klinisch resultaat waarneembaar. Beide studiegroepen vertoonden gunstige resultaten in vergelijken met andere studies uit de literatuur. Voor de vervanging van een gebitselement in de esthetische zone wordt dan ook een implantaat met een gladde hals of met een ruwe hals aangeraden en niet een implantaat met een gewelfde hals, omdat er bij laatstgenoemde type implantaat meer botverlies en een minder klinische resultaat werd waargenomen. 151

Samenvatting

solitaire implantaten in de esthetische zone veelbelovend zijn. Belangrijke variabelen als het esthetische resultaat, aspecten van de peri-implantaire mucosa en patiënttevredenheid moeten nog nader worden onderzocht. De vraag of direct en vroeg belasten tot vergelijkbare – of zelfs betere – behandelresultaten leiden dan conventioneel belasten, kon niet worden beantwoord wegens gebrek aan goede gecontroleerde studies. Hetzelfde geldt voor de vraag wat het effect is van het type implantaathals op het behandelresultaat.

9

Chapter

9

In hoofdstuk 4 wordt het esthetische resultaat van de drie verschillende halstypen beschreven vanuit zowel het perspectief van de professional als vanuit het perspectief van de patiënt. Zowel het esthetisch resultaat van de kroon als de periimplantaire mucosa werd beoordeeld. Op foto’s, genomen na 1 jaar van plaatsen van de definitieve kroon (18 maanden na plaatsen van het implantaat), werd door twee professionals het esthetisch resultaat beoordeeld aan de hand van twee objectieve indexen (de Pink Esthetic Score-White Esthetic Score (PES-WES) en de Implant Crown Aesthetic Index (ICAI)). Een 5-punts schaal, lopend van zeer ontevreden tot zeer tevreden, werd gebruikt voor de beoordeling van het esthetisch resultaat door de patiënt. De algemene tevredenheid van de patiënt over het resultaat van de behandeling, werd gemeten met behulp van een schaal, lopend van zeer ontevreden (score 0) tot zeer tevreden (10). Er bleek geen verschil in het esthetisch resultaat van de drie verschillende typen implantaathalzen. Volgens de professionals waren respectievelijk 79.3% en 62% van de kronen esthetisch acceptabel, gemeten met de meetinstrumenten PES-WES en ICAI. De mucosa bleek in 59.8% en 56.5% esthetisch acceptabel. Een regressie-analyse toonde aan dat een pre-implantologische bot-opbouw (i.v.m. een botdefect) leidt tot een slechter esthetisch aanzicht van de peri-implantaire mucosa. Meer dan 80% van de patiënten bleek tevreden te zijn over de esthetiek van de kroon en peri-implantaire mucosa. Hieruit blijkt een verschil tussen de opinie van de professional en de opinie van de patiënt. De algemene tevredenheid van de patiënten was hoog (9.0 ± 1.0, gemeten met een visueel analoge schaal). Op basis van de resultaten van deze studie wordt geconcludeerd dat het esthetisch resultaat van solitaire implantaten niet afhankelijk is van het type hals van het implantaat, maar wel van een pre-implantologische bot-opbouw. In hoofdstuk 5 wordt de uitkomst van direct belasten van solitaire implantaten in de esthetische zone beschreven. Er werd nagegaan of deze uitkomst onderdoet voor een concept waarbij de implantaten conventioneel worden belast. Er werden 62 patiënten met een missend frontelement in de bovenkaak at random toegewezen aan twee studiegroepen. In de ene studiegroep werden patiënten behandeld met een implantaat die binnen 24 uur werd voorzien van een tijdelijke kroon. Deze kroon had geen contact met de gebitselementen in de onderkaak, d.w.z. deze kroon was uit de occlusie (directe groep). In de andere studiegroep werd het implantaat eerst ‘onder het tandvlees begraven’ (d.w.z. het tandvlees werd teruggehecht over het ingebrachte implantaat)(conventionele groep). Na drie maanden werd het implantaat ‘opgezocht’ (d.w.z. er werd een verbinding gemaakt tussen het in de kaak gelegen implantaat en de mondholte) en werd het implantaat voorzien van een tijdelijke kroon. Drie maanden na plaatsen van de tijdelijke kroon, werden de implantaten voorzien van een volledige keramische 152

In hoofdstuk 6 wordt een casus beschreven waarbij een solitair implantaat in de esthetische zone direct werd belast met een tijdelijke kroon. Onder andere wordt ingegaan op hoe de tijdelijke kroon werd vervaardigd, hoe deze werd aangepast en hoe werd zorggedragen voor een optimaal profiel van de tijdelijke kroon. Nadat de tijdelijke kroon zijn functie had vervuld, werd middels een speciale afdruktechniek het optimale profiel van de tijdelijke kroon overgebracht naar de definitieve kroon. Deze definitieve kroon was volledig keramisch, kon rechtstreeks in het implantaat worden geschroefd en bestond uit een volledig keramische opbouw. Met behulp van dit protocol werd een optimaal esthetisch eindresultaat verkregen. In hoofdstuk 7 wordt een casus beschreven van een trauma tegen een kroon op een implantaat. Door een slag of stoot, kunnen het implantaat, de kroon en 153

Samenvatting

definitieve kroon. Zes en achttien maanden na plaatsen van het implantaat, kwamen de patiënten terug voor nader onderzoek. De primaire uitkomstmaat van deze studie was peri-implantair marginaal botverlies, gemeten op gestandaardiseerd vervaardigde röntgenfoto’s. De uitkomst van direct belasten werd slechter beschouwd dan conventioneel belasten, als bij direct belaste implantaten gemiddeld ten minste 0,5 mm meer peri-implantair botverlies optrad. Andere variabelen waren implantaat-overleving, aspecten van de peri-implantaire mucosa (pocketdiepte, plaque, bloeding, niveau van de peri-implantaire mucosa), esthetisch resultaat (gemeten met behulp van PES-WES en ICAI) en patiënttevredenheid. Alle implantaten hadden een goede primaire stabiliteit (≥ 45 N/cm insertie torsie). Na 18 maanden bleek geen verschil in marginaal peri-implantair botverlies tussen beide studiegroepen (directe groep 0.91 ± 0.61 mm, conventionele groep 0.90 ± 0.57 mm). Eén implantaat uit de directe groep ging verloren, drie weken na plaatsing van implantaat en kroon. Er gingen geen implantaten verloren in de conventionele groep. Tussen beide groepen werden geen verschillen waargenomen in pocketdiepte, hoeveelheid plaque, hoeveelheid bloeding en het niveau van de peri-implantaire mucosa. Ook werd geen verschil in esthetisch resultaat en patiënttevredenheid gemeten. Met inachtneming van de beperkingen van deze studie (groepsgrootte en follow-up), blijkt dat direct belasten van solitaire implantaten in de esthetische zone niet onderdoet voor conventioneel belasten. Omdat direct belasten voordelen biedt voor de patiënt, moet dit concept worden beschouwd als een veelbelovend alternatief voor conventioneel belasten. Echter, het concept van direct belasten moet men uitvoeren volgens een specifiek protocol, met aandacht voor voldoende primaire stabiliteit van het implantaat, een tijdelijke kroon uit occlusie en goede instructie en medewerking van de patiënt.

9

het peri-implantaire weefsel beschadigd raken. Bij deze casus was de kroon naar palatinaal verplaatst. Na zorgvuldig onderzoek en follow-up bleek dat enkel de schroef, waarmee de kroon in het implantaat was gefixeerd, te zijn beschadigd. De kroon kon gemakkelijk worden teruggeplaatst op het implantaat, en weer worden gefixeerd met een nieuwe schroef.

Chapter

9

In hoofdstuk 8 worden de voornaamste onderzoeksresultaten bediscussieerd en worden conclusies getrokken. Uit dit onderzoek blijkt dat, voor wat betreft een behandeling met een solitair implantaat in de esthetische zone, een implantaat met een 1,5 mm gladde hals of met een ruwe hals met groeven, minder periimplantair botverlies en betere klinische resultaten vertoont dan een implantaat met een gewelfde ruwe hals met groeven. Tussen de toegepaste halstypen bleek echter geen verschil in esthetisch resultaat en patiënttevredenheid. Verder wordt geconcludeerd dat het direct belasten van een solitair implantaat in de esthetische zone op de korte termijn niet tot een minder gunstig resultaat leidt dan conventioneel belasten. Vervolgonderzoek moet uitwijzen of deze conclusies ook gelden voor de lange termijn.

154

dankwoord

Prof. dr. G.M. Raghoebar, hooggeleerde eerste promotor, beste Gerry. Jouw gedrevenheid en enthousiasme voor de wetenschap zijn buitengewoon. Jij vormde samen met Henny en Arjan het trio die de basis legden voor dit proefschrift. Gerry, ik heb veel bewondering voor jouw klinische talent en jouw vooruitziende blik voor onderzoeksvraagstukken die de implantologie bezig gaan houden. Ik ben je dankbaar voor het vertrouwen dat je me hebt gegeven om dit promotietraject te doorlopen en voor de tijd die je altijd voor mij wist vrij te maken, ook voor zaken die naast het werk speelden. Ik vond de manier van samenwerking erg plezierig en de waardering die je me hebt gegeven, werkte zeer motiverend. Ook dank ik je voor de mogelijkheid om me naast mijn onderzoek te bekwamen in de klinische aspecten van de implantologie. Ik heb leuke herinneringen aan onze contacten buiten het werkveld (zoals de activiteiten bij de NVOI en natuurlijk de jaarlijkse voetbalwedstrijd tegen de studenten) en hoop in de toekomst op nog meer mooie herinneringen. Prof. dr. H.J.A. Meijer, hooggeleerde tweede promotor, beste Henny. Tijdens mijn afstudeerscriptie, die ik bij jou heb geschreven, wist jij me te enthousiasmeren voor dit promotieonderzoek. Als lid van het ‘spelerstrio’ Gerry, Henny en Arjan, had jij een onmisbaar aandeel in de totstandkoming van dit proefschrift. Jouw vermogen om hoofdzaken van bijzaken te onderscheiden verdient veel respect. Samen met Gerry, had jij het ‘Fingerspitzengefühl’ voor de relevantie van het onderwerp van dit proefschrift. Je was altijd uiterst collegiaal en ik waardeer de laagdrempelige manier waarop we met elkaar kunnen omgaan. Ik dank je voor de ervaring die ik onder jouw begeleiding heb opgedaan in de prothetiek op implantaten, maar ook voor het prettige informele contact, zowel op de werkvloer als daar buiten. Prof dr. A. Vissink, hooggeleerde derde promotor, beste Arjan. Ook jij was lid van hét 'spelerstrio' en opereerde in het beginstadium van het onderzoek vooral 155

Dankwoord

Onderzoek verrichten is teamsport. Mede dankzij een team van spelers is dit proefschrift tot stand gekomen. Ik ben dit team erg dankbaar voor het goede samenspel. Het waren niet alleen deze spelers, maar ook anderen die een belangrijke rol hebben vervuld bij de totstandkoming van dit proefschrift. In de eerste plaats ben ik alle onderzoekspatiënten veel dank verschuldigd voor hun medewerking aan dit onderzoek. Ook dank ik de mensen die langs de zijlijn hebben gestaan en mij als onmisbare supporters steunden met dit onderzoek. Graag wil ik een aantal ‘spelers’ en ‘supporters’ persoonlijk bedanken.

9

achter de schermen. Daarna werd jouw rol meer zichtbaar en was je van grote waarde bij het schrijven van dit proefschrift. Jouw capaciteit om binnen zeer korte tijd artikelen te voorzien van suggesties en kritisch commentaar, grenst aan het randje van het onvoorstelbare. Je wist met jouw commentaar feilloos de vinger op pijnlijke plekjes te leggen, waardoor de kwaliteit van dit proefschrift significant is verbeterd (is niet statistisch getest, maar hoeft ook niet, het is gewoon zo). Ik dank je verder voor de prettige manier van samenwerken tijdens de spreekuren en voor het bijbrengen van de chirurgische vaardigheden op het gebied van de implantologie. Prof. dr. E. Rompen. I would like to thank you for your willingness to participate as a member of the PhD-committee and for the time you have spent on judging the manuscript. Furthermore, I would like to thank you for being a speaker at the symposium the day before the defence of the thesis.

Chapter

9 Prof. dr. G.J. �������������������������������������������������������������������� Meijer en prof. dr. D. Wismeijer, hooggeleerde leden van de beoordelingscommissie. Ik wil u graag bedanken voor de bereidheid om zitting te nemen in de beoordelingscommissie en voor de tijd die u hebt genomen om mijn manuscript te beoordelen. Prof. dr. L.G.M. de Bont, geachte professor. Graag bedank ik u voor de gelegenheid die u mij heeft gegeven om op de afdeling kaakchirurgie dit promotietraject te doorlopen. Onder uw leiding heerst er een open en prettige sfeer op de afdeling en ligt er een solide basis voor onderzoek. Dit heeft zeer wel bijgedragen tot de voltooiing van dit proefschrift. Ik ben u verder erkentelijk voor de mogelijkheid om naast mijn onderzoek de opleiding tot implantoloog te volgen. Drs. H.J. Santing, beste Eric. Samen zaten we in het bestuur van de Tandheelkunde Mondhygiëne Faculteitsvereniging (TMFV Archigenes). Een geweldig jaar! Gelukkig hebben we de foto’s en de anekdotes nog. Na je afstuderen voegde ook jij je als onderzoeker bij onze onderzoeksgroep. Op de werkvloer konden we het goed met elkaar vinden, maar ook op andere vloeren hebben we mooie momenten beleefd. Jammer dat het ‘minibar-moment’ tijdens het jaarlijkse EAO congres verloren dreigt te gaan. Hopelijk komen hier in de toekomst andere tradities voor in de plaats. Jij nog veel succes met het afronden van jouw promotietraject. Bedankt dat je mijn paranimf wilt zijn. Dr. N. Tymstra, beste Nynke. Ooit werden we meneer Enkeltands en mevrouw Dubbeltands genoemd. Wellicht verandert dit straks in Dr. Enkeltands en Dr. Dubbeltands. Onze promotietrajecten startten tegelijk en kenden veel raakvlak156

Dr. C. Stellingsma, beste Kees. Je fungeerde regelmatig als een belangrijke mentor. Ik kon met je van gedachten wisselen over onderzoekskwesties en dat werkte verhelderend. Ik dank je voor je rol als medeauteur en voor het behandelen van een groot aantal onderzoekspatiënten. Ook dank ik je voor de leuke tijd op congres. De warme nootjes zal ik niet snel vergeten. Mw. E. Wartena, beste Esther. De logistiek, planning en assistentie rond een grote klinische studie is geen sinecure. Alleen het inplannen al van een slordige 1300 afspraken (ongeveer 11 afspraken per onderzoekspatiënt) verdient veel respect, helemaal als de programma’s van de behandelaars al zo vol zitten. Jij kreeg het voor elkaar en wist het hele onderzoeksproject hiermee te stroomlijnen. Je leverde elke woensdagochtend maatwerk zodat het meetwerk weer kon beginnen. Hartelijk dank voor je inzet en de leuke samenwerking. Dhr. G. van Dijk, beste Gerrit. Graag wil ik je bedanken voor de positieve samenwerking betreft het tandtechnische aspect van dit onderzoek. In jouw tandtechnische laboratorium werden alle kronen vervaardigd samen met een groot deel van de richtplaatjes, binnen soms praktisch onmogelijke levertijden. Gerrit en alle medewerkers van het Tandtechnisch Maxillofaciaal Laboratorium Gerrit van Dijk, hartelijk dank hier voor. Dankzij jullie flexibiliteit, bleek niets te veel gevraagd. Dhr. A.K. Wietsma, beste Anne. Ik wil je hartelijk bedanken voor het vervaardigen van de eerste richtplaatjes en je belangrijke bijdrage aan de planning van de positie van de implantaten. Ook dank ik je voor je bereidheid om immer ad-hoc in je ‘hok’ met kunstgrepen de zaak te redden (een gebroken plaatprothese, een zoekgeraakt boorsjabloon, een krom richtstaafje etc.). Mw. M.A. Bezema, mw. B. Termeulen-Brongers, mw. H.H. Kooistra-Veenkamp, mw. I.J. Valkema, beste Ans, Bertina, Ria en Ingrid. Hartelijk dank voor jullie ondersteuning bij het behandelen van de onderzoekspatiënten en jullie zorgvuldige 157

Dankwoord

ken. We hebben veel samengewerkt en samen gewerkt op de onderzoekskamer die we jaren deelden. Discussies werden gevoerd over onderzoeksvraagstukken, maar ook onderwerpen buiten ons onderzoeksveld kwam regelmatig ter sprake. Hoogtepunten waren de diverse EAO congressen, het gezamenlijk optreden op Malta en natuurlijk het bezoek aan Las Vegas. Ik vind het erg bijzonder dat we ons (bijna) gelijktijdig hebben ontwikkeld tot ‘volwaardig onderzoeker’. Ik bedank je voor de leuke onderzoekstijd die we samen hebben beleefd en voor je kritische blik op mijn proefschrift. Bedankt dat je mijn paranimf wilt zijn.

9

werk achter de schermen. Dankzij jullie resulteert de ‘PPC’ niet in een Pre Prothetische Chaos. Mw. L.M.E. Kamstra-Dooper, mw. E.J.G. van Luijk-Voshaar, mw. A. van OplooTalens, mw. A. Prins-Schutter, mw. Y. Sanders-Niessen, beste Liliane, Emmy, Tiny, Anja en Yvonne. Ik dank jullie dat ik altijd mocht inbreken in jullie drukke programma voor het maken van de vele röntgenfoto’s voor dit onderzoek. Prof. dr. B. Stegenga, beste Boudewijn. ‘Het is allemaal niet zo ingewikkeld, als je maar denkt dat je het kunt’. Hartelijk dank voor deze visie, voor je rol als medeauteur en voor het boeiende informele contact.

Chapter

9

Dr. J.J.R. Huddleston Slater, beste James. Mede dankzij jouw hulp, werd mijn eerste publicatie een feit. Dat deze publicatie beloond werd met de NVGPT publicatieprijs, zie ik als een bekroning op onze samenwerking. Saillant detail is dat ik deze prijs uit jouw handen mocht ontvangen. Ik dank je verder voor het oplossen van diverse methodologische en statistische vraagstukken (soms eenvoudig via ‘human eyeball criteria’). Dr. L. Meijndert, beste Leo. Op de afdeling Kaakchirurgie was jij de pionier op het terrein van onderzoek naar solitaire implantaten in de esthetische zone. Jij onthulde de fascinerende aspecten van deze onderzoekslijn en legde een goede basis voor vervolgonderzoek. Dank voor het gespreide bedje dat je voor me klaar hebt gezet. Drs. G. Telleman, drs. J.W.A. Slot, drs. K.W. Slagter, drs D. Rickert en drs. Y.C.M. de Waal, beste Gerdien, Wim, Kirsten, Daniela en Yvonne. Hartelijk dank voor jullie interesse in mijn onderzoek en het goede gezelschap tijdens de congressen. Veel succes met het afronden van jullie promotieonderzoek. Mw. N.E. Jaeger, mw. L. Kempers, mw. K. Wolthuis, dhr. P. Haanstra, dhr. H.B. de Jonge en dhr. R.M. Rolvink, beste Nienke, Lisa, Karin, Piet, Harry en Richard. Bedankt voor jullie secretariële, technische en faciliterende ondersteuning. Alle mede-onderzoekers en AIO’s van de afdeling Kaakchirurgie. Hartelijk dank voor jullie belangstelling en de leuke contacten rond de diverse koffieautomaten en aan de lunchtafels. Alle niet met name genoemde medewerkers van de afdeling Kaakchirurgie. Hartelijk dank voor de plezierige samenwerking. 158

Lieve broer, zusje, opa, Jeltje en schoonfamilie. Hartelijk dank voor jullie warme belangstelling en steun. Jullie waren onmisbaar als ‘twaalfde man’. Opa, wat speciaal dat u de verdediging van mijn proefschrift gaat meemaken. Willemijn, jij in het bijzonder bedankt voor de gevulde Tupperwarebakjes voor als er thuis weer geen tijd was om te koken. Lieve ouders. Jullie hebben mij altijd gesteund en mij vrij gelaten in het maken van mijn keuzes. Ik ben jullie dankbaar voor de solide thuisbasis en het feit dat ik altijd op jullie kan rekenen. Zonder jullie was ik nooit zo ver gekomen. Heel veel dank hier voor! Lieve Femke. Jij was mijn belangrijkste supporter en mijn steun en toeverlaat als het even tegen zat. Dat jij bezig bent met het afronden van je tweede studie werkte zeer motiverend. Samen sluiten we straks een drukke periode af. Dat we in deze periode echt naar elkaar zijn toegegroeid, betekent gewoon dat wij bij elkaar horen. We vormen het perfecte duo en vullen elkaar zó goed aan. Sorry, dat ik de laatste tijd misschien wat afwezig ben geweest (‘je luistert niet!’…. ‘euhh…wat zeg je?’), maar dit maak ik straks weer meer dan goed! Lieve Femke, jij bent de reden dat ik na mijn werk weer zin heb om naar huis te gaan. Over een paar maanden zeg ik zonder enige twijfel ‘ja’ tegen jou. Je bent mijn topper. Ik hou van je!

159

Dankwoord

Alle medewerkers van Tandartsenpraktijk Loppersum. Heel veel dank dat ik – naast mijn onderzoek – altijd onbezorgd hier kon werken. Altijd was alles perfect geregeld en kon ik na een dag(deel) werken weer rustig verder met mijn onderzoek. Ook waren mijn patiënten tijdens mijn afwezigheid altijd in goede handen. Ab en alle medewerkers van dé praktijk, er is geen betere praktijk denkbaar om te mogen werken.

9

Curriculum Vitae Laurens den Hartog was born on 9 September 1980 in Steenwijk, the Netherlands. After finishing secondary school, he studied dentistry at the University of Groningen. During his study, he was chairman of the student faculty association of dentistry and was an employee of the Central Medical Library. He graduated as a dentist in 2004 and combined the PhD research described in this thesis with his work as a dentist in a private practice in Loppersum. Furthermore, Laurens worked as a dentist and as a teacher in implant prosthodontics at the Dental School of the University of Groningen. In 2010 he finished a post-doc training program to become an implantologist. Currently, he is secretary of the board of the Dutch Society of Oral Implantology (NVOI).

L. den Hartog University Medical Center Groningen Department of Oral and Maxillofacial surgery 9700 RB Groningen The Netherlands [email protected]

160

Suggest Documents