This is an undergraduate student report submitted as part of a  requirement in Dental Public Health.      The views and findings included in this report do not  necessarily reflect the views of the University of Toronto or  the individuals quoted. 

Are composite resin fillings more susceptible to recurrent caries than non-resin fillings in the general population? A review.

Taif Alobaidy Astha Bansal Ibrahim Darrag Rachit Gangar Sandra Issa Preeti Lalit Ioana Leb-Neinstein Chaitanya Patel

University of Toronto Faculty of Dentistry Submitted June 10, 2014

Abstract Background. Secondary caries is the main reason for replacement of dental restorations. Since the introduction of composite resins as filling material, their use increased greatly due to their esthetic properties. Objectives. To determine whether composite resin fillings are more prone to recurrent caries than non-resin restorations in the general population. Search methods. A systematic search was conducted for relevant articles in six databases. The team was divided in pairs and was assigned one to two databases. Selection criteria. The authors only included studies that compared resin to non-resin filling materials with regards to secondary caries formation. Other inclusion criteria were: studies in vivo done on humans, articles written in English and availability of full text articles. Excluded articles were those used in the Cochrane review from 2014 and the ones with a design other than randomized clinical trial or cohort. Data collection. Six online databases were used for the search of significant articles. After removing duplicates, a total of 279 articles were screened by title and abstract and 42 full text articles were reviewed. Six studies were included in the review. Results. Compared to amalgam, composite resin fillings are more prone to recurrent decay formation. No differences were found between composite resin fillings and inlays. Composite resins provided less protection against secondary caries formation in patients with high risk for caries than glass ionomer cements. Compomers use in children proved superior to composite resins. Conclusions. Composite resins are more prone to secondary caries compared to amalgam, glass ionomer cements and compomers. MeSH Words. Composite resins, amalgam, glass ionomer cements, inlays Key words. Recurrent caries, secondary caries



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1. Background Secondary (recurrent) caries is the main reason (65%) for replacement of restorations in the dental practice, regardless of the material. [1,2] In a review on secondary caries, Mjör and Toffenetti discussed the difficulty the dental community faces in defining this condition: “There is no clear differentiation made among secondary caries, marginal defects, and residual or remaining caries”. [3] In the present review, the consensus was to refer to recurrent caries as lesions observed at the tooth-restoration interface. Recent studies have examined whether composite resin fillings are more prone to recurrent caries than the rest of the materials. The reasons for this are mainly attributed to the degradation of the hybrid layer formed at the tooth-restoration interface. Delaviz et al. (2014) determined that the breakdown is a result of material-host interplay: Salivary enzymes, bacteria, and matrix metalloproteinase are responsible for the breakdown of both the adhesive and composite resins and subsequently, limit their lifespan. [4] Shokati et al. (2010) concluded in a study that the degradation of the resins is an ongoing process in which salivary enzymes such as esterases induce porosities on the surface of the composite resin and at the level of the hybrid layer by attacking the BIS-GMA-based resin material. This can occur in as little as six months after the placement of fillings, leading to microleackage and accumulation of bacteria, specifically Streptococcus mutans, the major cause for caries formation. [5, 6] Amalgam, composite resins, glass ionomer cements (GIC), resin modified glass ionomer cements (RMGIC) and compomers are all currently used as filling materials in primary and permanent teeth. In addition to these, inlays are also available as an alternative to direct intracoronal restorations. They all present, to different degrees, with the potential of forming secondary caries. For decades, amalgam has been the material of choice in tooth restoration, especially in the posterior teeth. It is strong and durable, but its unaesthetic appearance and health safety concerns that were raised because of mercury content put its use into question. [7-9] Although amalgam fillings release minimal amounts of mercury vapors, current scientific consensus supports the position that amalgam does not constitute a health hazard. [10,11] Since Buonocore [12] first introduced composite materials into practice in 1955, their use in the dental practice has increased exponentially. Initially, they were mainly used in anterior, low stress 3

bearing teeth due to mechanical properties concerns, but manufacturers have since improved them so that they are successfully used in the posterior teeth, where occlusal forces are high [13]. Patients prefer tooth-colored to metallic restorations because of their esthetic properties, but also because of toxicity concerns. Practitioners increasingly use them because of both excellent esthetics and improved mechanical properties. In some countries, amalgam use has decreased significantly and from both a patient and dentist perspective, as the trend seems to be focused more and more on esthetic restorations. [14,15] Resin modified glass ionomer cements and compomers are esthetic materials with intermediate wear and shrinkage characteristics. RMGI are similar to the classic GIC, but have resin added to their composition for strength and esthetics. Compomers release fluoride, but are more similar to composites, which make them highly esthetic. Compared to composite resins, glass ionomer cements have the advantage of fluoride release, resistance to microleakage and reduced shrinkage, but they are less esthetic and have reduced abrasion and fracture resistance. [16] Indirect intracoronal restorations such as inlays made out of different materials (gold, ceramic, composite resins) were introduced in order to overcome water solubility and polymerization shrinkage, as well as to increase marginal adaptation, strength, hardness and polishabilty. [17, 18] The disadvantages of these alternatives compared to the direct restorations are related to higher cost, longer chair-side time and technique sensitivity. [19] As with any material used in dentistry, there are advantages and disadvantages that come with their usage. Manhart et al. (2002) describe the factors that contribute to restoration failure as being patient, dentist and material-related. Patient factors are related to the location of the restoration, caries risk of the patient, the exposure to fluoride, and compliance with recall. Dentist factors are linked to cavity preparation, handling and application of the material. Material related factors are polymerization shrinkage, strength, wear resistance, bond strength, and technique sensitivity. [20] Composite resins are not only esthetic, but also allow a more conservative preparation compared to amalgam and are easy to repair. Disadvantages are mainly related to their use in the posterior high stress bearing areas: occlusal wear, polymerization shrinkage, gap formation, and difficulty in restoring proximal contact, which lead to secondary caries formation. [21] In spite of these limitations of composite resins, their use is growing.



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There are two important reasons for this literature review. Due to the growing demands for composite resin placement by the patients on one side and the dentists on the other, it is important to assess whether they in fact increase the secondary caries formation rate compared to the other available materials. In addition, a search of the literature revealed many studies that compared composite resins to amalgam, but few that compared them to the other tooth-colored materials used in restorative dentistry.

2. Objective To determine whether composite resin fillings are more prone to recurrent caries formation compared to non-resin filling materials in the general population.

3. Methods 3.1. Criteria for considering studies for this review: The inclusion criteria for studies were based on articles that are written in English, completed invivo on humans and available in full articles. The exclusion criteria were the following: studies which were included in the Cochrane review on ”Direct composite resin fillings versus amalgam fillings for permanent or adult posterior teeth” (2014), systematic reviews, meta-analysis, in-vitro studies, case report studies, and case series studies. The authors only considered studies that had a period of minimum 2 years follow-up. 3.2. Types of study The type of studies was selected based on the strength of the studies to assess therapy. Thus randomized clinical trials and cohort studies were considered. Randomized clinical trials offer strong evidence in assessing efficacy; however, there are limitations in application to general dental practice because they are conducted under ideal conditions [22]. The cohort studies, prospective or retrospective better reflect outcomes in a non-ideal, “real life” situation [23, 24].



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3.3. Types of participants and interventions Adults, both male and female, and children were included in the systematic review and the results were analyzed based on primary and permanent teeth, not based on age. All studies that compared composite resin restorations to amalgam, glass ionomer, compomers, and inlay were included. 3.4. Types of outcome measures Outcomes were either accepting the null hypothesis in which there is no difference between composite resin restorations and the other restorative materials used or rejecting the null hypothesis. 3.5. Search methods for identification of studies A systematic search was performed on PubMed, Scopus, Science Direct, Ovid, Google Scholar and The Cochrane Collaboration to select the articles that met the predefined inclusion criteria. The key words used in all databases were composite resins, composite resin filling, resin filling, composite filling, dental amalgam, glass ionomer cements, ceramic inlay, gold inlay, composite inlay, recurrent caries, secondary caries, and dental decay. The search was limited to in-vivo studies on humans and to the ones written in English. The group was divided into pairs. Each pair was assigned a database and used the keywords to search for relevant articles. Of the 545 records identified, 279 articles remained after removing the duplicates. These were first screened based on the title and 205 were excluded. Then, 74 articles were reviewed by abstract. The next step was retrieving the full articles, and each article reviewed independently taking into consideration the identified question and the inclusion/exclusion criteria, and six studies were chosen for the evidence-based project. The selected articles were further reviewed individually. Summary charts were created in which the following information was included, if available: Author, date, population description, intervention, control, outcome, critical appraisal comments and conclusions.



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3.6. Data collection and analysis The authors used the following checklists for randomized clinical trials and cohort studies: 1. Checklist to Assess Evidence of Efficacy of Therapy or Prevention. (Adapted from: Fletcher, Fletcher and Wagner. Clinical epidemiology – the essentials. 3rd ed. 1996, and Sackett et al. Evidence-based medicine: how to practice and teach EBM. 1997); 2. 12 Questions to Help You Make Sense of a Cohort Study (Critical Appraisal Skills Programme (CASP), 2004). [28]

4. Results The six reviewed articles collected from different databases, present evidence obtained from randomized controlled trials and cohort studies. Details on the preliminary search results, with included and excluded articles, are summarized in the flow chart and rejection tables (Tables 1 and 2). The total number of patients assessed in all six included articles is 1033, age ranging from 4 to 47 years. Of the three randomized clinical trials that were selected, one compared composite resins to amalgam, one composite resins to amalgam and glass ionomer cements, and the third evaluated composite resin and glass ionomer cements. Of the three cohort studies, one assessed composites and compomers in children (split mouth, blind study), another one compared composites to ceramic inlays, and the last study compared direct composite resin fillings to indirect composite restorations (inlays). Table 3 gives details on the reviewed studies. The randomized controlled trial by Pallesen et al. (2003) evaluated composite resin fillings and inlays in adults over a period of 11 years. After that period, there was no statistically significant difference in the clinical outcomes between composite resins and inlays. De Moor et al. (2009) compared composite resins to glass ionomer cement restorations in cancer irradiated patients – a high risk group for secondary caries formation – and found that composite resins exhibited greater marginal and structural integrity in presence of fluoride but failed to 7

provide protection against secondary caries when compared to glass ionomer cements, especially in the non-fluoride use (NFU) patient group. In the two-year study by Pascon et al. (2005), 79 restorations were placed in school children with median age of 6 years and 2 months. Although the follow-up duration was short due to the short span of deciduous teeth, they found that compomer restorations had the best success rate compared to heliomolar composite restorations. Opdam et al. (2005) conducted a retrospective cohort study, in which data were collected in 2002 on treatments provided over a period of seven years (1990-1997). The evaluation of the longevity of 912 silver amalgam and 1955 composite resin restorations found that the largest cause for restoration failure was secondary caries, in both amalgam (29%) and composite resins (38%). Lange and Pfeiffer (2009) compared 395 composite resin restorations and 264 ceramic inlays regarding marginal adaptation, anatomic form, colour match of restoration, marginal discolouration, and secondary caries formation and surface roughness. There were no statistically significant differences between the two restorative modalities. In a five-year study done by Mjör and Jokstad (1993), out of 274 class II restorations that were placed in adolescents averaging 13 years of age (88 amalgam, 95 GIC, 91 composite resin), the composite resins failed mainly due to secondary caries while amalgam and glass ionomer restorations failed due to bulk fractures. Although the allocation for materials was not clearly defined and drop out was high, the long duration of the study (5 years) and the evenly distributed materials amongst the groups at follow up, offered reliable outcomes. With regards to the PICO question (Are composite resin fillings more susceptible to recurrent caries than non-resin fillings in the general population?) and based on all the selected studies, it appears that in permanent teeth composite resin restorations are more prone to secondary decay compared to amalgam and glass ionomer cements (in healthy and xerostomic patients).

4.1. Risks of bias and limitations in the included articles 4.1.1. Blinding We considered two of the randomized clinical trials to be at high risk for performance and detection bias (De Moor 2009, Pallesen & Qvist-2003), since neither operators nor examiners blinding was possible.

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4.1.2. Sample size: We considered three of the studies to have a small sample size (Pascon-2005, De Moor-2009, Pallesen & Qvist-2003), which would have an impact on the significance of the outcome.

4.1.3. Loss of follow-up The authors considered three studies to have high percentage of follow-up loss (>20%) (Lange and Pfeiffer-2009, De Moor-2009, Pascon-2005, Mjör and Jokstad-1193). However in Mjör and Jokstad, 161 losses to follow up of restorations were evenly distributed for the restorative materials.

5. Discussion 5.1. Summary of main results On the basis of the search strategy, the majority of the studies that were found compared composite to amalgam and only a few studies compared it to other available restorative materials. The evidence collected demonstrates that composites show a higher rate of secondary decay when compared to amalgam, GIC and compomer. Compared to inlays, no significant differences were found. 5.2. Quality of evidence and its implications The quality of evidence extracted from the reviewed articles is moderate, with each of them showing, to different degrees, strengths and limitations. A common trait of most studies was loss to follow up. The study by Pallesen & Qvist, considered only patients with sets of 5 equal sized class II restorations and randomization was done, ensuring subjects blinding. All the restorations were placed by one of the authors in order to minimize the inter-operator variability. The length of the study (11 years) increased the validity of the results. At follow-up visits, both operators analyzed

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the restorations, so that operator bias was minimized. Follow-up loss accounted for 4% (1 patient). The only limitation of the study was the small sample size (n=28). The study by Pascon et al. was double blinded as the patient and the three examiners were not aware of the type of intervention. Patients were subjected to split mouth intervention, so no control group was required. The limitation of the study was its short duration and follow-up loss of 25%. Similarly, the study by Mjör and Jokstad faced high follow up loss (approximately 60%). However, losses were evenly distributed amongst the three types of restorations. In the study by De Moor, patients had a history of head and neck irradiation and a minimum of three class V (cervical) lesions. Good patient allocation was ensured, but the sample size was small (35 patients) and the follow-up loss was 77% (attrition bias). Blinding of examiners was not possible as the types of restorations were visibly different from one another, which contributed to detection bias. Lange & Pfeiffer showed limitations in their study, as they did not specify whether the outcome was the result of material factor, operator factor or the patient variability. Loss of follow-up was over 20%. Opdam et al. collected data on a large number of patients (621 patients) over a period of seven years and a total number of 2867 restorations were assessed. To reduce bias of measuring results between restorations in same patients, Cox regression was estimated by using bootstrap technique (1000 fold re-sampling of original population study). Limitations were minimal in this study. 5.3. Potential biases in the review process One of the filters the authors used in their search was for articles only written in English. Therefore, a language bias should be taken into consideration. The number of articles included in the review was limited due to a Cochrane review that was published in 2014, which compared amalgam to composite resins with regards to secondary caries formation. Since the Cochrane Collaboration reviewed all the randomized clinical trials pertaining to this topic that were written up until September 2013 and had acceptable strength of evidence, we included cohort studies in the present study. Only one article done on humans in vivo was



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published after the review [34], which was not included because it did not compare the materials with regards to secondary caries formation. In addition to the above-mentioned factors, publication bias also needs to be considered. Only published data were collected and included in this review; thus, relevant studies may exist, but were inaccessible to the team.

5.4. Agreements and disagreements with other studies or reviews. When comparing composite resins to amalgam with regards to recurrent decay formation, the results support the outcome of the recent Cochrane review published in 2014, stating that the main reason for composite failure is recurrent decay and that this material is more prone to it than others. [25] When comparison of direct composites was done with indirect restorations, such as ceramic inlays, no significant difference was found between both materials with respect to secondary caries. However, ceramic inlays yielded better results with respect to marginal adaptation, anatomic form and color match (Lange & Pfeiffer, 2009). Similarly for composite inlays, Pallesen and Qvist found no difference in outcome between direct composite fillings and composite inlays. Moreover, the success rate of compomers in deciduous teeth was similar to the observed results in studies by Gross in 2001 and Duggal in 2002.[32,33]

5.5. Author’s conclusions The present review is in accordance with the literature concerning the longevity of dental restorations. The latter depends on many different factors: material factor, dentist factor and the patient factor and the reasons for their failures are secondary caries, bulk fracture, marginal leakage and deficiencies and wear. [20] Although composite restorations are more prone to redecay, are more technique sensitive and more costly than amalgam, they are increasingly preferred by patients and dentists due to their aesthetic properties. Indirect restorations are more costly, require more chair side time and may not lead to better results than the conventional direct ones [26, 27]. In some cases, such as high-risk patient undergoing head and neck radiation therapy the

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benefits of GIC use are a trade off with the higher mechanical strength of composite resins. [2931] Also, in primary teeth, where occlusal forces are lower than in permanent teeth and due to their shorter lifespan, the use of GICs or compomers may be preferred. It is evident that composite restorations are more prone to secondary decay, but further studies are needed in order to reach a conclusion regarding comparison between composite resins and inlays, GIC and compomers.

5.6 Implications for practice All the 6 studies used for the review and the results of the Cochrane suggest that composite restorations were followed up for considerable period of time and have shown above average clinical outcomes. In the light of this knowledge, the benefits of superior aesthetic and strength of newer resins are weighed against the longevity and the risk of secondary decay formation. The material’s properties are evident and are supported by the literature, however patients and clinician factors should also be assessed. Therefore, restrictions should be considered in high caries risk patients and children when one should consider using restorative material with fluoride release or supplement. Regardless of the intervention, every treatment should start with the proper treatment plan and case selection. These two factors play a very important role in the successful outcome of any restoration. A dentist should always be aware and updated with all new products and use them according to evidence available in the literature. Additionally, the dentist should follow up after the treatment to check for failure due to recurrent caries. All clinical settings should be equipped with all the materials needed to restore a tooth based on clinical finding, because no single material has been found to have all the required properties that would lead to an ideal restoration. Composite resins require less extensive tooth preparation, but as it is technique sensitive, the dentist needs to take all required precautions before the placement of such materials. Every new material to be used on patients should be backed by strong research and evidence before it is introduced in the market. Information on its advantages/disadvantages over other materials should be made available.



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6. Acknowledgements 6.1. Dr. Dick Ito, Dr. Amir Azarpazhooh, Ms. Maria Buda, Ms. Dena Taylor 6.2. Authors: Taif Alobaidy, Astha Bansal, Ibrahim Darrag, Rachit Gangar, Sandra Issa, Preeti Lalit, Ioana Leb-Neinstein, Chaitanya Patel

References not included in the review 1. Forss, H. , Widstrom E. (2004) Reasons for restorative therapy and the longevity of restorations in adults. Acta Odontologica Scandinavica., 62, 2, 82-86 2. Mjör

IA, Shen

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Placement and replacement of restorations in general dental practice in Iceland. Operative Dentistry 27(2), 117-23. 3. Mjör IA, Toffenetti F. (2000) Secondary caries: a literature review with case reports. Quintessence International 31(3), 165-79. 4. Delaviz Y, Finer Y, Santerre JP, (2014) Biodegradation of resin composites and adhesives by oral bacteria and saliva: A rationale for new material designs that consider the clinical environment and treatment challenges. Dental Materials, 30(1), 16-32. 5. Shokati

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the integrity and fracture toughness of the dentin-resin interface. Journal of Biomedical Materials Research. Part B, Applied Biomaterials, 94(1), 230-7. 6. Kermanashi S, Santerre JP, Cvitkovitch DG, Finer Y. (2010) Biodegradation of resindentin interfaces increases bacterial microleackage. Journal of Dental Research, 89(9), 996-1001. 7. Roulet JF. (1997) Benefits and disadvantages of tooth-coloured alternatives to amalgam. Journal of Dentistry, 25(6), 459–73. 8. Kelly PG, Smales RJ. (2004) Long-term cost-effectiveness of single indirect restorations in selected dental practices. British Dental Journal, 196(10), 639–43. 9. Mitchell RJ, Koike M, Okabe T. (2007) Posterior amalgam restorations - usage, regulation, and longevity. Dental Clinics of North America, 51(3), 573–89.

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10. General Assembly Resolution. (2001). Retrieved March 27, 2014 from http://www.fdiworldental.org/media/11683/2010.ga.resolution.on.dental.amalgam.pdf 11. Canadian Dental Association Position on Dental Amalgam. (2005). Retrieved March 27, 2014 from http://www.cda-adc.ca/_files/position_statements/amalgam.pdf 12. Buonocore MG. (1955) A simple method of increasing the adhesion of acrylic filling materials to

enamel surfaces. Journal of Dental Research; 34, 849–53

13. Lutz F, Krejci I. (1999) Resin composites in the post-amalgam age, Compendium of Continuing Education in Dentistry. 20(12), 1138-44, 1146, 1148. 14. Hickel R, Manhart J. (1999) Glass-ionomers and compomers in pediatric dentistry. In: Davidson CL, Mjör IA, Advances in glass-ionomer cements. Berlin: Quintessence Publishing Co., 201–26. 15. Manhart J, Hickel R. (1999) Esthetic compomer restorations in posterior teeth using a new all- in-one adhesive: case presentation. Journal of Esthetic Dentistry, 11, 250–8. 16. Gross LC, Griffen AL, Casamassimo PS. (2001) Compomers as class II restorations in primary molars. Pediatric Dentistry, 23, 24–7 17. Bessing C, Lundqvist P. (1991) A 1-year clinical examination of indirect composite resin inlays; a preliminary report. Quintessence International, 22(2), 153-7. 18. Donly KJ, Jensen ME, Triolo P, Chan D. (1999) A clinical comparison of resin composite inlay and only posterior restorations and cast-gold restorations at 7 years. Quintessence International, 30(3), 163-8. 19. Wassell

RW, Walls

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results British Dental Journal, 179(9), 343-9. 20. Manhart J, Garcia-Godoy F, Hickel R. (2002) Direct posterior restorations: clinical results and new developments. Dental Clinics of North America 46(2), 303–339 21. van Dijken JW. (1994) A 6-year evaluation of a direct composite resin inlay/onlay system and glass ionomer cement-composite resin sandwich restorations. Acta Odontologca Scandinavica, 52(6), 368-76. 22. Mjör IA. The reason for replacement and the age of failed restorations in general dental practice. Acta Odontologica Scandinavica 1997, 55, 58-63

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23. Song JW, Chung KC (2010) Observational studies: cohort and case-control studies. Plastic and Reconstructive Surgery, 126(6), 2234-42. 24. Mann CJ (2003) Observational research methods. Research design II: cohort, cross sectional, and case-control studies. Emergency Medical Journal, 20(1), 54-60. 25. Rasines Alcaraz MG, Veitz-Keenan A, Sahrmann P, Schmidlin PR, Davis D, IheozorEjiofor Z (2014) Direct composite resin fillings versus amalgam fillings for permanent or adult posterior teeth (Review). Cochrane Database of Systematic reviews, 31,3. 26. ODA (2014) suggested fee guide January 2014; ODA suggested fee guide for GP, Toronto, Ontario, 18-21. Retrieved from University of Toronto Dental Library on June 2, 2014. 27. Tobi H., Kreulen C., Vondeling H., van Amerongen WE. (1999) Cost-effectiveness of composite resins and amalgam in the replacement of amalgam Class II restorations. Community Dental Oral Epidemiology, 27(2), 127-43. 28. Critical Appraisal Skills Programe (2004). Making sense of evidence about clinical effectiveness. Retrieved from: http://www.caspinternational.org/mod_product/uploads/CASP_Cohort_Studies_Checklist_ 14.10.10.pdf 29. McComb D, Erickson RL, Maxymiw WG, Wood RE (2002) A clinical comparison of glass ionomer, resin-modified glass ionomer and resin composite restorations in the treatment of cervical caries in xerostomic head and neck radiation patients. Operative Dentistry 27, 430-437. 30. Verbeeck RMH, De Maeyer EA, Marks LA, De Moor RJG, De Witte AM, Trimpeneers LM (1998) Fluoride release process of (resin-modified) glass-ionomer cements versus (polyacid-modified) composites. Biomaterials 19, 509-519. 31. Vermeersch G, Leloup G, Vreven J (2001) Fluoride relsease from glass-ionomer cements, compomers and resin composites. Journal of Oral Rehabilitation, 28, 26-32. 32. Gross LD, Griffen AL, Casamassimo PS (2001) Compomers as class II restorations in primary molars. Pediatric Dentistry, 23,24-7.



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33. Duggal MS, Toumba KJ, Sharma NK. (2002) Clinical performance of a compomer and amalgam for the inter proximal restoration of primary molars: a 24-month evaluation. British Dental Journal 2002, 193,339-42. 34. Khalaf ME., Alomari QD. , Omar R. (2014) Factors relating to usage patterns of amalgam and resin composite for posterior restorations - a prospective analysis. The Journal of Dentistry, 5712(14).

References of studies included in the review 1. Pallesen U, Qvist V (2003) Composite resin fillings and inlays. An 11-year evaluation. Clinical Oral Inverstigation, 7(2), 71-9. 2. De Moor RJ, Stassen IG, van ‘t Veldt Y, Torbeyns D, Hommez GM (2011) Twoyear clinical performance of glass

ionomer and resin

compositerestorations in

xerostomic head- and neck-irradiated cancer patients. Clinical Oral Investigation, 15(1), 31-8. 3. Fernanda Mioni Pascoon , Kamila Rosamilla Kantovitz (2006) Clinical evaluation of composite and compomer restoration in primary teeth 24 months result. Journal of Dentistry 34, 6, 381-388. 4. Opdam NJ, Bronkhorst EM, Roeters JM, Loomans BA (2007) A retrospective clinical study on longevity of posterior composite and amalgam restoration. Dental Materials, 23(1), 2-8. 5. Lange RT, Pfeiffer (2009) Clinical evaluation of ceramic inlay compared to composite restoration. Operative Dentistry, 34(3), 263-72. 6. Mjör IA, Jokstad A (1993) Five year study of class ii restorations in permanent teeth using amalgam, glass polyyalkenoate (ionomer) cement and resin-based composite material. Journal of Dentistry, 21(6), 338-43.



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