UNIVERSITY OF SIENA SCHOOL OF DENTAL MEDICINE
PHD PROGRAM: “DENTAL MATERIALS AND CLINICAL APPLICATIONS”
Ph D THESIS OF: Carlo Monaco
TITLE “Clinical and scientific aspect of Inlay Fixed Partial Dentures”
ACCADEMIC YEAR 2004/2005 December 2005 Siena Italy
Committee: Promoter Prof. Marco Ferrari Co-Promoter Prof. R. Scotti Prof. xxxxxxxxxxxx Prof. xxxxxxxxxxxx Prof. xxxxxxxxxxxx Prof. xxxxxxxxxxxx
TITLE “Clinical and scientific aspect of Inlay Fixed Partial Dentures” _____________________________________________________________
Chapter 1: General introduction 1.1
Tooth structure removal associated with various preparation designs
Metal-free inlay retainer restorations
Indication and contraindications of inlay-fixed partial denture
Chapter 2: The use of fiber reinforced composites in dentistry 2.1
Fiber-reinforced composite systems
Properties of the fibers and polymer matrices
Impregnation of the fibers
Quantity of fibers
Direction of the fibers
Position of fibers
Water sorption of FRC matrix
Chapter 3: Marginal adaptation of IFPDs 3.1 Marginal adaptation of three partial bridges made with different structure material. Chapter 4: Criteria for selecting the materials for IFPDs 4.1 Fracture strength of three partial bridges made with different structure material. Chapter 5: laboratory process for high volume fiber framework 5.1
Fiber reinforced composite with a high volume framework: a technical
procedure. Chapter 6: Different structure of the framework 6.1 Clinical Evaluation of Fiber-Reinforced Composite IFPDs. Chapter 7: adhesive procedures 7.1 Inlay Bridge With a New Microfilled Composite: A Clinical Report
Chapter 8: Clinical trial 8.1 Randomized controlled trial of Fiber-Reinforced Composite Inlay Fixed Partial Dentures: two-year results. Chapter 9: Alternative materials as regards FRC 9.1 Fatigue test in shear: its effect on bond of a glass-infiltrated alumina ceramic to human dentin, using different luting procedures.
Chapter 10 Other clinical application of FRC 11.1 Clinical evaluation of teeth restored with quartz fiber-reinforced epoxy resin posts. Chapter 11 Conclusions Summary
Chapter 1 General Introduction When missing tooth structure or teeth are replaced, minimal biologic risk should be involved to reestablish function and esthetics. To proven reliability and durability of complete-crown metal ceramics made them the method of choice for posterior singletooth restorations and fixed partial denture (FPD). However, this restoration required considerable reduction of tooth structure. The increased use of the adhesive technique and preservation of dental tissues have greatly impacted conservative tooth preparation design. The development of fibre-reinforced composite (FRC) technology and all-ceramic systems has opened the potential for fabrication of metalfree restorations with durability and good aesthetics. This thesis contains a study on several different basic and clinical aspects related to the use of inlay-fixed partial dentures made with fiber-reinforced composites and all ceramic systems. Starting from the assessment of the differences between the amount of tooth structure removed for conventional preparation and various innovative designs for fixed prosthodontics, the next step was to analyse the different materials that can be used when missing tooth must be replaced. Inlay-fixed partial dentures and dental implants are the true alternatives to the conventional metal-ceramic three-unit bridges; for these reason an overview regarding the properties advantages and disadvantages of fiber-reinforced materials is presented. As actually different fiberreinforced composites are available on the market, it is important for the clinician to know the properties of each system to select the more appropriate for the specific clinical application. The first objective of this thesis was to evaluate before and after fatigue the marginal adaptation of inlay fixed partial dentures made with different materials and establish a connection between the quality of continuous/non-continuous margins and the mechanical properties of different materials. The second was indeed to conduct a study to assess the fracture strength and the dye penetration after fatigue of one fiberreinforced composite and two all-ceramic systems, and to verify the existence of a correlation between the mechanical resistance and the microleakage. Another goal of this thesis was in fact to evaluate if and how different methods of positioning of the
fibers for the framework can increase the fracture strength and reduced the flexibility of the bridges. The design of the fiber framework is an important prerequisite to obtain a durable clinical success when using fiber-reinforced composite. Another step of this thesis was to describe the technical procedure to obtain a framework with a high volume of fiber; for these reason a clinical study comparing the survival rate of inlay fixed partial dentures made with different framework design is presented. Bonding procedures represent the goal for the term of partial restorations. The next step of this thesis was to describe the luting procedures and the surface treatment for the inlay bridges and to compare the clinical performances and the post-operative sensibility of three- and two-step adhesive systems after two-year observation period. Alternative materials to the metal-ceramic restorations went through rapid developments in the last few years, in particular alumina- and zirconia based ceramics. Both these materials represent the future alternatives of the fiber-reinforced composite but their clinical applications in partial restorations are still limited. The next steps of this thesis were the analysis of the bond of a glass-infiltrated alumina ceramic to human dentin, using different luting procedures. Finally the use of fiber-reinforced composite in the reconstruction of the endodontically treated teeth is examined with according to the aim of the minimal intervention philosophy.
1.1 Tooth structure removal associated with various preparation designs The introduction of more invasive complete crown preparation for metal- and allceramic crowns has been correlated with an increase in pulpal complications since these restorations require considerable reduction of tooth structure (Creugers et al 1994). For a metal-ceramic shoulder preparation, a facial tooth reduction of about 1.3 to 1.5 mm and an occlusal reduction of 2.0 mm are recommended (McLean JW 1980, Rosenstiel et al 1995). In 1966, only 0.4% to 2% radiographic periapical pathologies were found (Ericsson et al 1966), whereas in 1970, 2.9% was reported (Schwartz et al 1970), and about 10 years later up to 4.0% periapical pathologies were detected (Kerschbaum et at 1981). These results are explained by the use of air turbines () and more invasive shoulder or chamfer preparations compared to the feather-edge design
used in the 1960s and 1970s (Klötzer 1984). A lower number of endodontic complications are associated with less invasive preparations. In a literature review, inlay restorations at 10 years showed a lower rate of loss of pulpal vitality (5.5%) compared to complete crowns (14.5%) (Kerschbaum et al 1981). The mechanical reliability and broad range of indications have made complete crowns the preferred denture retainer. However, wing—shaped retainers with retentive elements such as grooves made of metal have demonstrated a remarkable long-term success rate if the clinical protocol is followed carefully (Creugers et al 1992). The gravimetric analysis (Edelhoff et al 2002) showed that for a metal-ceramic crown retainer preparation, almost eight times more tooth structure must be removed compared to an adhesive wing-and groove attachment for a resin-bonded cast-metal fixed partial denture. The “new” half-crown preparation assigned for all ceramic fixed partial dentures (FPDs) required a similar amount of tooth structure removal as the onlay and cost approximately half of the tooth structure of a complete crown design. The percentage of tooth structure removal associated with the different preparation designs for a mandibular premolar was 19.3% for mesial/distal occlusal inlay without transverse ridge or central groove, 30.4% for mesial/distal occlusal inlay with transverse ridge or central groove and 75.9% for mete-ceramic complete crown. Similar percentages of tooth structure removal were found for the same kind of preparation in mandibular molar (19.3%, 25.5%, 73.1%). The inclusion of enamel promotes a superior bond over dentin, lower postcementation sensitivity, improved support of the materials used for the restorations, and reduced endodontic intervention. The positive influence of tooth structure preservation on the life expectancy of the pulp was reported in the literature. For cast-metal resin- bonded FPDs, a 0.13% rate of loss of pulpal vitality up to 5 years was reported, compared to 9.1% for complete crown abutments in the same period (Paszyna et al 1990).
1.2 Metal-free inlay retainer restorations For the past 30 yr, some dentists have avoided the use of full coverage retainers for fixed partial dentures in order to conserve sound tooth substance. Generally, metalreinforced systems are the materials of choice for fabricating posterior fixed partial dentures because of their reliability and durability. Inlay-retained FPDs made of
metal alloys are been usually seated using the conventional cementation technique and cements (Kopp 1970). Before adhesive techniques were introduced to restorative dentistry, conventionally cemented partial crowns or inlays, made of cast gold, were used instead of full coverage crowns to retain a pontic (Boitel 1969). A common problem was the loss of retention of a retainer, with subsequent secondary caries development (Roberts 1970). As a result, more effective intracoronal retention with the help of boxes, grooves, and pins was demanded (Weinberg 1970).
solutions, however, mitigated the advantage of minimal invasiveness compared with complete-crown retainers. In the 1980s, adhesive techniques allowed the luting of metallic frameworks to dental enamel by using metal retainer wings made of cast gold or non-precious metal (Rochette 1973, Livaditis 1983). Inadequately retentive preparation shapes and insufficient stability of the metal framework were perceived to have been contributing factors. After initially frequent losses of retention, more defined and retentive preparations, along with improved adhesives, led to acceptable retention rates, especially in anterior teeth (Rammelsberg et al 1993). The aesthetic limitations caused by the metallic framework remained a problematic issue. The dark framework on the oral surfaces of abutment teeth eliminated translucency and gave the teeth a greyish appearance (Livaditis 1983) Restorations made of metal alloys are characterized by certain basic disadvantages. These base metal components that form on the surface of the alloy during the metal-ceramic fusing process may have a negative effect on the adjacent soft tissue. In addition, the opaque, darkish appearance created by certain metal denture retainers in the abutment teeth is considered to be unattractive. Partial preparations like inlays, onlays or partial crowns are recommended as retainers for short-span FPDs in caries-resistant dentitions. In addition to facilitating superior periodontal health, partial retainers enable preservation of healthy tooth structure. The combination of highly translucent prosthodontic materials and resin composite cements has enhanced the use of the adhesive technique and launched a new era of restorative treatment options with promising initial clinical results (Sorensen et al 1999). New in vitro findings and a better understanding of stress formation in fiber-reinforced composite (FRC) (Vallittu 1996, Freilich et al 2004) and in all-ceramic restorations led to less invasive preparations extended to existing systems. There has been limited use and no published clinical data of all-ceramic posterior FPDs retained either by wings or
inlays, mostly because of the low strength, the strength scatter, and the timedependent strength decrease of ceramics owing to slow crack growth (Fischer et al 2003). The reduced invasiveness of these resin-bonded inlay-retained FPDs makes them an appealing alternative to conventional preparations in cases where the residual dentition exhibits low caries activity. Metal-free materials such as fiberreinforced composites or high strength pressed ceramics exhibit outstanding corrosion resistance. The esthetics properties of these systems must be attributed to the high translucency of the materials and the fact than the restorations are entirely fabricated of tooth-coloured materials thereby achieving a high degree of light transmission. However, restorations made of these materials are not as strong as those that are metal-supported because of their particular mechanical properties. To achieve adequately strong dental restorations, therefore, certain modifications are necessary in the preparations fabrications, and cementation methods. The preparation geometry on an inlay retainer offers favourable prerequisites for the adhesive cementations technique. The preparation is usually surrounded by dental enamel, and the location of the preparation margin allows a rubber dam to be placed to ensure complete isolation. Adhesive cementation could offer one of the most effective ways of countering the loss of retention, which is one of the most frequent causes of failure of conventional inlay-retained fixed partial dentures.
1.3 Indication and contraindications of inlay-fixed partial denture The indications have to be strictly observed because of the special properties of the metal-free materials. As a result, careful assessment and planning prior to beginning the prosthodontic treatment measures are requisite. Furthermore, the following prerequisites must be met if the successful results are to be achieved with metal freeinlay-retained FPDs. 1.
Good oral hygiene
Low susceptibility to caries
Parallel alignment of abutment teeth
Immobility of the abutment teeth
Minimum height of abutment teeth ≥ 5mm (connector thickness)
Maximum mesiodistal extension of the interdental gap of 9 mm (width of premolar) if pressed ceramic is used and 12 mm (width of molar) if fiberreinforced composite materials are used.
Severe parafunctions, short clinical crowns (