Prognosis of Indirect Composite Resin Cuspal Coverage on Endodontically Treated Premolars and Molars: An In Vivo Prospective Study

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1 on Endodontically Treated Premolars and Molars: An In Vivo Prospective Study Maria Carlos Real Dias, DDS, MSc, 1 Jorge N.R. Martins, DDS, MSc, 2 André Chen, DDS, MSc, 3 Sérgio André Quaresma, DDS, Msc, 4 Henrique Luís, PhD, MS, BS, 5 &João Caramês, DDS, PhD, FICD 6 1 Clinical Assistant Faculty, Occlusion and Oral Rehabilitation, Lisbon University, School of Dental Medicine, Lisbon, Portugal 2 Department of Endodontics, Implantology Institute, Lisbon, Portugal 3 Clinical Assistant Faculty, Implant Dentistry, Lisbon University, School of Dental Medicine, Lisbon, Portugal 4 Assistant Professor of the Master of Endodontics, International University of Catalunya, Barcelona, Spain 5 Professor of Statistics and Probabilities, University of Lisbon Dental School, Lisbon, Portugal 6 Full Professor and Chairman of the Implantology Department, Lisbon University, School of Dental Medicine, Lisbon, Portugal Keywords Composite resins; dental restoration failure; follow-up studies; root canal therapy; dental cavity preparation. Correspondence Jorge N.R. Martins, Instituto de Implantologia of Lisbon, Av. Columbano Bordalo Pinheiro, 50 5º e6º, Lisboa, Portugal. jnr_martins@yahoo.com.br. Jorge N.R. Martins ORCID The authors deny any conflicts of interests. Accepted August 2, 2016 doi: /jopr Abstract Purpose: This prospective clinical study evaluated the success rate of indirect composite resin cuspal coverage on endodontically treated molars and premolars and the survival rate of the restored teeth. Materials and Methods: One hundred fifty endodontically treated teeth were restored with total resin cuspal coverage and randomly selected for the study. Patients were recalled after 2 to 5 years for clinical evaluation. Data were subjected to standard tests of statistical correlations using Spearman test. Results: Out of the 150 teeth, 84 were molars and 66 were premolars. Of these teeth, 58.7% had mesio-occlusal-distal (MOD) cavities, 20.7% had mesio-occlusal (MO), and 20.7% had occlusal-distal (OD). A build-up procedure was performed in 51.3% of the teeth, and buccal veneer composite resins were placed at the margins of 96.7% of the teeth. Out of the 150 teeth, 30 (20%) presented margin discoloration, 3 teeth (2%) had restoration reparable fractures, 2 teeth (1.3%) had restoration irreparable fractures, and 1 tooth (0.7%) exhibited secondary recurrent caries. The opposing arch that occluded with the treated teeth presented 58% natural teeth (no restoration material), 26.7% ceramic crowns, and 15.3% implant-supported ceramic crowns. Statistically significant differences (p = 0.018) between irreparable restoration fractures and the type of support material present in the opposing arch were found. Conclusions: In a period of up to 5 years, the resin cuspal coverage of endodontic treated teeth had a success rate of 96%, while the tooth survival rate was 100%. The type of support material on the opposing arch may influence the longevity of the restoration of endodontically treated teeth. The success of endodontically treated teeth depends not only on the clinician s ability to eliminate intracanal microorganisms and avoid new contamination, but also skill in avoiding coronal and root fractures. 1,2 Several techniques and materials have been used to restore damaged teeth. Direct composite resin restorations have become a standard for intracoronary cavities, 3 but unfortunately some limitations inherent in composite resin systems have not been fully overcome. 4 The light-cured resin contraction during polymerization represents a significant limitation, since it may lead to a volume shrinkage of 2% to 4%. 4,5 A large polymerization contraction can cause excessive forces against the tooth structure, potentially leading to pulpal problems. 4,5 Another issue is the failure to obtain a complete and uniform polymerization throughout the restoration, 6 potentially leading to postoperative pain, marginal pigmentation, secondary recurrent caries, or fractures causing microleakage. The development of systems for indirect composite restoration, with the material handling to be performed in an environment of controlled light, temperature, humidity, pressure, and time, allows for better polymerization, which in turn results in a well-cured restoration, minimizing shrinkage and improving mechanical properties due to a postpolymerization cycle. In addition, the extraoral handling gives the restoration improved Journal of Prosthodontics 00 (2016) 1 7 C 2016 by the American College of Prosthodontists 1

2 Dias et al contours, proximal contacts, occlusal anatomy, and cavosurface adaptation. 6 In heavily destroyed endodontically treated teeth, it is important to preserve as much of the remaining dental structure as possible, especially in the cervical region, for a better mechanical stabilization of the restoration. The use of posts is not mandatory, unless there is insufficient tooth structure to retain the core. The pulp chamber can be used as part of the retention, in addition to adhesion. 7 Restoring an endodontic tooth is subject to some controversy, although it has been extensively studied. A few years ago, several studies supported the theory that a greater risk of fracture in endodontic teeth was due to dentin dehydration and loss of collagen links. 8 At present, this fragility is associated with the loss of tooth structure. 9 The loss of structural integrity, associated with the access opening, in endodontically treated teeth has led to a greater prevalence of fractures when compared to vital teeth The coronal access results in an increased deflection during the cusp function, raising the possibility of cusp fracture and microfracture of the restoration margins. This is supported by the fact that, in addition to the destruction resulting from access to the pulp chamber, there is an association with the loss of tooth structure due to caries or previous restorations. 12,14 There are several options to restore a tooth with endodontic treatment, and there is no single solution for all clinical situations. Taking into account the best scientific knowledge, preference should be given to restorative treatments that preserve the maximum natural structure. 7,9 Restorations that increase the structural integrity also improve the prognosis of a tooth exposed to the forces of chewing, especially in teeth with root canal treatment. Cuspal coverage is essential to strengthen the cusps of an endodontically treated tooth, 15 except for the cases where a class I can be solved by a direct restoration in a safe occlusal context. 9 Rocca and Krejci 9 give a rationale for a proper therapeutic option in endodontic teeth, highlighting important aspects such as the thickness of the remaining walls, the dimension of the cavity, and above all, the occlusal surface. Schwartz and Robbins 14 suggested that a cuspal coating should be placed on the tooth to ensure long-term success, since there is a greater chance of survival when compared with intracoronary restorations. Mondelli et al 16 also researched and evaluated the fracture resistance of highly destroyed premolars (mesio-occlusal-distal [MOD] cavity preparation with removal of the pulp chamber roof) restored with a packable composite resin, with and without cuspal coating. The results showed that a cuspal coating can be a safe option for restoring weakened teeth treated endodontically. They also stated that restoring premolars with cuspal coating increased the fracture toughness, when compared with teeth restored without cuspal coating. Composite onlays may be seen as a restorative option that gives all the advantages of a cusp coverage restoration, and also the advantage of being a less expensive treatment option, which presents the possibility of correcting minor fractures in the mouth with composite resin without requiring a new restoration. Despite the extensively published literature on the restoration of endodontically treated teeth, the information available regarding the use of composite resin cuspal coverage is very scarce. The primary objective of this study was to evaluate, in in vivo conditions, the influence of several factors (type of tooth, type of preexisting cavity, presence of build-up, discoloring of the composite veneering, type of restoration fractures, loss of adhesion, tooth fracture, secondary decay, and opposing arch characteristics) in the prognosis of indirect composite resin cuspal coverage, as a restorative option for endodontically treated teeth. The secondary objective was to evaluate the survival rate of teeth with endodontic treatment after being restored with composite resin cusp coverage. Materials and methods Tooth selection Premolars and molars with recently performed endodontic treatment, requiring restorative procedures were preselected for this study. All teeth were placed in a proper occlusion with their opposing tooth (Angle s class I occlusion). Periodontal disease was absent from all cases, and the mobility was within physiological limits for all of them. Teeth with class I cavities (due to the great amount of tooth integrity) or previously restored with posts, definitive restorations with cuspal coverage, core reconstructions, or crowns were excluded. Tooth restorative procedures All teeth had endodontic treatment performed by two experienced endodontists, according to the quality guidelines of the European Society of Endodontology. 17 The restorative procedures were performed by a clinician with exclusive practice to restorative dentistry (single operator) at the Instituto de Implantologia, Lisbon, between 2009 and 2012, having followed the Rocca protocol. 3 According to this protocol, each tooth was covered with flow composite at the channel inlet (immediately after the root canal filling procedure performed in a previous endodontic appointment), and measured for the distance between the floor of the pulp chamber and the remaining tooth, in order not to exceed 4 mm (all measurements were performed using a periodontal probe). If the depth of the cavity exceeded this value, the tooth was subjected to a composite resin build-up (Filtek Z250 micro-hybrid resin; 3M ESPE, St. Paul, MN). This procedure was also applied when the remaining margin was less than 2 mm deep from the gingival margin, or the remaining wall was less than 1.5 mm thick (Fig 1). The objective was to have margins and thickness equal or superior to those values. This procedure was performed under proper rubber dam isolation. The exposed dentine was submitted to immediate dentine sealing (all enamel margins were cleaned after this procedure to ensure perfect enamel adhesion). Tooth preparation followed a protocol requiring 1.5 to 2 mm wear on functional cusps and 1 mm wear on non-functional cusps. All corners were rounded and the angle of divergence of the walls was about 10. The peripheral limits of the restorations had a cavosurface angle of 90, except in cases where esthetics were mandatory (an esthetic bevel was implemented in the buccal wall at 1 mm deep). The final impression was made at the same appointment with dual consistency addition silicone in one stage. Fermit (Ivoclar Vivadent, Amherst, MA) was used as a provisional restorative material. The measures were confirmed in working models. All 2 Journal of Prosthodontics 00 (2016) 1 7 C 2016 by the American College of Prosthodontists

3 Dias et al Prognosis of Indirect Composite Resin Cuspal Coverage Figure 1 Composite resin build-up decision making. Figure 2 Clinical procedures for overlay placement on the second premolar: (A) initial; (B) composite resin build up; (C) cuspal reduction; (D) overlay laboratory work; (E) standard measurements; (F) prepared for cementation; (G) premolar overlay; (H) matching measurements; (I) cementation; (J) final esthetic result of the second premolar treatment. Figure 3 Buccal veneering composite placement for esthetic reasons in the maxillary first premolar (before and after). indirect restorations were performed with the Adoro System (Ivoclar Vivadent, Schaan, Liechtenstein), following manufacturer s recommendations. Cementation with RelyX Unicem-Tr (3M ESPE, Seefeld, Germany) was performed 15 days after the initial treatment under rubber dam isolation (Fig 2). The occlusion of all restorations was checked with shimstock paper. The paper was folded to be 16 mm thick. For esthetic reasons, if there was a visible transition between tooth and resin restoration, an additional layer of microhybrid composite veneering was implemented to opacify the final result (Fig 3). Journal of Prosthodontics 00 (2016) 1 7 C 2016 by the American College of Prosthodontists 3

4 Dias et al Final sample selection and recalls From the preselected larger sample, a smaller sample was randomly selected to be included in the study and subjected to posterior clinical evaluation. The randomization method consisted of picking papers with a patient chart and tooth number from a bag. The picked cases were to be included in the study. A total of 150 teeth were admitted in this in vivo study. All patients were scheduled for a 2-year recall, and those who failed this appointment would be contacted by phone or to try to bring them back to a proper recall, although no recall should exceed 5 years. This study was approved by the Ethics Commission of the Instituto de Implantologia. Statistical analysis The primary outcome (restoration success) was defined as a failure if the tooth required a new restoration, tooth repair, or extraction during the follow-up period. Teeth lost due to endodontic and periodontal reasons were to be excluded (from the restoration success rate) due to the independence of the restoration. The exception would be tooth loss due to endodontic reasons caused by restorative microleakage. The secondary outcome (tooth survival) was considered successful if the tooth was functional, or in the case of the presence of fracture (of the restoration or of the tooth) still possible to be restored. The independent variables analysed were: type of tooth (premolar or molar), type of preexisting cavity (mesio-occlusal [MO], occlusal-distal [OD], MOD), presence of build-up, discoloration of the composite veneering, type of restoration fractures (reparable [possible to be repaired in mouth] or irreparable [impossible to be repaired in mouth and requiring a new restorative procedure]), loss of adhesion, tooth fracture, secondary decay, and opposing arch (intact tooth with enamel occlusal contact point, tooth-supported ceramic crowns and implantsupported ceramic crowns). Data were collected in SPSS and subject to standard tests of statistical correlations using the Spearman test. Statistical significance was declared when the average failure was >0.027 for an alpha of 0.05 and power of Results The 150 teeth admitted to this study belonged to 150 patients (79 males, 71 females). It was possible to bring back all patients over the recall period of 2 to 5 years, representing a 100% recall rate with 0% dropouts. Out of the 150 teeth, 84 were molars (56.0%) and 66 were premolars (44.0%). Preexisting MOD cavities were noted in 58.7% of the cases, 20.7% of the teeth had a MO cavity, and 20.7% had an OD cavity (Table 1); 51.3% of the studied teeth had a build-up procedure done, and 48.7% did not need this kind of pre-restoration. In 96.7% of the cases, it was necessary to place veneer composite on the margin. Over the follow-up period (2 to 5 years), there were 30 teeth (20%) with margin discoloration defined as margin pigmentation, and 120 teeth (80%) esthetically acceptable (still with invisible margin between tooth and restoration). In the same period, there were 3 reparable (2%) (2 male, 1 female patient) Table 1 Type of cavity and tooth type Sample (n) Percent Tooth type Molar Premolar Total Cavity MO OD MOD Total Table 2 Opposing arch Sample (n) Percent Natural teeth Ceramic crowns-tooth Ceramic crowns-implants Total Table 3 Reparable fractures versus type of cavity Reparable fracture Type of cavity MO OD MOD Total * No correlation between the type of cavity and the reparable fracture (ρ = 0.042, p = 0.612). and 2 irreparable (1.3%) (1 male, 1 female patient) restoration fractures. The 3 reparable fractures occurred at 2.5 years (twice) and 4 years, while the 2 irreparable fractures happened at 3 and 4.5 years. There were no cases of failed adhesion or fractures to the underlying tooth, nor were there endodontic or periodontic problems. In the same period, only a single tooth (0.7%) exhibited secondary recurrent decay. The arch opposing restored teeth had different characteristics: 58% had natural teeth (no restoration material) with an enamel occlusal contact point, 26.7% of the opposing arch had tooth-supported ceramic crowns, and 15.3% had implant-supported ceramic crowns (Table 2). Spearman correlation test, with a significance level of 5% showed no correlation between the type of cavity and the reparable fracture (Table 3) or irreparable fracture (Table 4). Also, there was no correlation between type of teeth and reparable fractures (ρ = 0.031, p = 0.709) or irreparable fractures (ρ = 0.103, p = 0.210). There was no correlation between the type of opposing arch and reparable fracture (Table 5); however, when it comes to irreparable fractures, all the events occurred when the opposing arch had implant-supported ceramic crowns, representing a statistical significance (ρ = 0.193, p = 0.018) (Table 6). There were no correlations between the existence 4 Journal of Prosthodontics 00 (2016) 1 7 C 2016 by the American College of Prosthodontists

5 Dias et al Prognosis of Indirect Composite Resin Cuspal Coverage Table 4 Irreparable fractures vs type of cavity Irreparable fracture Type of cavity MO OD MOD Total * No correlation between the type of cavity and irreparable fracture (ρ = 0.043, p = 0.599). Table 5 Reparable fractures versus opposing arch Reparable fracture Opposing arch Natural teeth Ceramic crownstooth Ceramic crownsimplants Total * No correlation between the type of opposing arch and reparable fracture (ρ = 0.119, p = 0.148). Table 6 Irreparable fracture vs opposing arch Irreparable fracture Opposing arch Natural teeth Ceramic crownstooth Ceramic crownsimplants Total * Statistical significance (p = 0.018). of build-up and reparable fracture (ρ = 0.147, p = 0.073) or irreparable fracture (ρ = 0.119, p = 0.146). The success rate of the restorative procedure was 96% after this follow-up period. No endodontically treated teeth were lost over the same period. Discussion The best scientific evidence shows that prognosis of an endodontically treated tooth not only depends on endodontic variables, but also on correct tooth rehabilitation. 18,19 To the best of the authors knowledge, there are only two in vivo studies 20,21 on a critical issue such as the one explored in this investigation. The difficulty in performing a proper follow-up and standardizing the study are cited as possible reasons for the lack of literature on this topic. According to Nagasiri and Chitmongkolsuk, 20 the survival rates of endodontically treated molars without crowns were 96%, 88%, and 36% at 1, 2, and 5 years, respectively. With greater amounts of coronal tooth structure remaining, the survival probability increased. Regarding the different types of full-coverage restorative procedures, the outcomes are also relatively high. According to a Cochrane review by Sequeira-Byron et al 22 the full-coverage metallic-ceramic crown may reach a success of 98.1% at 3 years. A systematic review by Morimoto et al 23 concluded that ceramic onlays may reach a survival rate of 95% at 5 years. Donovan et al s 24 retrospective evaluation states that full-coverage cast gold restorations may be successful in 97% of cases in a period between 1 and 9 years. Cavity and tooth type The choice of a restorative method is frequently based on cavity configuration and on residual number of cavity walls; however, the residual wall thickness could be a valuable clinical parameter when choosing a restoration for endodontically treated teeth. 9,25 Cuspal deflection and strain increase significantly when axial dentine is removed as part of the endodontic access. 26 It is often necessary to build and strengthen the remaining tooth with composite, to increase margins, or round the internal angles. 27 When the residual wall thickness is less than 2 mm, only cuspal coverage, with or without a fiber post, provides satisfactory fracture resistance. 25 The thickness of the walls, measured in the mouth and in models, was one of the criteria for standardization of the teeth selected for this study. In this study, the presence of a build-up did not affect the type of fracture (reparable or irreparable), which is consistent with the literature suggesting that the remaining tooth must be at least 1.5 to 2 mm thick so that fracture toughness could be the greatest. This study followed the literature, 3 implementing resin composite microhybrid as a build-up material. According to the literature, 15,16 the type of previous cavity (MO, MOD, and OD) is not related to the type of restoration fracture (reparable or irreparable), if cuspal coverage is performed. This data is confirmed in the present study, in which the type of cavity (MO, OD, or MOD) did not statistically affect the type of fracture. The anatomy and tooth type (molars or premolars) can be an important issue. 9 The axial forces in molars and the more complex set of forces in premolars increase the potential of fractures, especially with reduced healthy tissues. 12 In this study, there was no relationship between the type of tooth and the type of restoration fractures (reparable or irreparable). Margin discolorations Evidence shows that margin discolorations, defined as margin pigmentation, are frequent after 5 years. 21 The present study showed 20% margin discolorations. This data is consistent with the literature. 21 This may be explained by natural pigmentation of the composite over time. In some cases, a simple polish of the margin was enough to restore the original color. Journal of Prosthodontics 00 (2016) 1 7 C 2016 by the American College of Prosthodontists 5

6 Dias et al Type of material The mode of failure is a criterion for success, since a reparable fracture allows repair in the mouth. It is classified as irreparable if the fracture is found below the cemento-enamel junction (CEJ), or if it is so extensive that it does not allow the fractured overlay to be repaired (it leads to extraction, full-crown coverage, or a new overlay). The type of cement may influence cuspal deflection stability and tooth fracture resistance. 28 In this study, this variable was minimized by using the same cement, under the same conditions of absolute isolation in all cases. It should also be noted that, according to Magne and Knezevic s 29 in vitro study, the rate of fracture below the CEJ is between 30% and 40% for ceramic overlays and 20% for composite overlays (with a 3 mm cuspal reduction and immediate dentin sealing). For this reason, and also because it is possible to repair them in the mouth, all overlays in this investigation were performed in composite. All three cases of reparable fractures that occurred in the current study have been successfully solved with an additive composite technique in the mouth. The indirect process of executing the restorations has been associated with minimum material shrinkage and improved mechanical properties due to post-polymerization cycles. In this study, all restorations were performed through the indirect process using the Adoro system as the only restorative material, to avoid variability in materials. Opposing arch A key factor that the literature does not address as a factor that may influence the success rate is the type of material in the opposing arch. The choice of cases is critical to long-term success. In this study, the type of material in the opposing arch significantly affected the type of fracture. More than half of the opposing teeth were natural teeth with enamel contact points (58.0%), the remaining were tooth-supported ceramic crowns (26.7%) and implant-supported ceramic crowns (15.3%). The opposing arch did not influence the reparable fractures. On the other hand, the irreparable fractures were influenced by the support material present in the opposing arch. All irreparable fractures occurred when the opposing arch had implant-supported ceramic crowns (p = 0.018). No data regarding bruxism or nightguard protection was investigated, so it was not possible to understand, in this study, the influence of these parameters. The lack of proprioception may be a possible reason for this finding. Careful conclusions should be taken regarding the incidence of irreparable fractures against implant ceramic crowns. Since this event occurred only twice, it would be important to have a larger sample size or an extended follow-up period to be able to draw reasonable conclusions regarding a possible risk factor. None of the irreparable fractures led to tooth loss, since both fractures were restricted to the overlays. Both teeth could be restored again, one with a full crown and the other with a new overlay. Final primary and secondary outcome Over the follow-up period of 2 to 5 years, the indirect composite resin cuspal coverage had a success rate of 96%. The six failures, out of the initial 150 teeth, were from three reparable fractures, two irreparable fractures, and one secondary recurrent decay. No tooth was lost, which represents a 100% survival rate of endodontically treated teeth for the period evaluated. In our study, the fact that the same operator restored and evaluated all cases may mean a potential bias to influence data. This may be mitigated by the fact that the success criteria were objective and minimally dependent on the operator s opinion. The presence of bruxism and the comparison between maxillary and mandibular teeth were not addressed in this study, and those might be good subjects for future research. Conclusion Under the conditions of this research, it is possible to conclude that cusp coverage of endodontically treated premolars or molars showed an excellent clinical performance in a period that may reach 5 years. The success rate of restorations was 96%, and the tooth survival rate was 100%. The types of teeth and cavity had no influence on the type of fractures that occurred in the follow-up period. References 1. Ng YL, Mann V, Rahbaran S, et al: Outcome of primary root canal treatment: systematic review of the literature Part 2. Influence of clinical factors. 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7 Dias et al Prognosis of Indirect Composite Resin Cuspal Coverage 14. Schwartz RS, Robbins JW: Post placement and restoration of endodontically treated teeth: a literature review. J Endod 2004;30: Magne P: Composite resins and bonded porcelain: the postamalgam era? J Calif Dent Assoc 2006;34: Mondelli RF, Ishikiriama SK, De Oliveira Filho O, et al: Fracture resistance of weakened teeth restored with condensable resin with and without cusp coverage. J Appl Oral Sci 2009;17: European Society of Endodontology: Quality guidelines for endodontic treatment: consensus report of the European Society of Endodontology. Int Endod J 2006;39: Lazarski MP, Walker WA, Flores CM, et al: Epidemiological evaluation of the outcomes of nonsurgical root canal treatment in a large cohort of insured dental patients. J Endod 2001;27: Imura N, Pinheiro ET, Gomes BP, et al: The outcome of endodontic treatment: a retrospective study of 2000 cases performed by a specialist. J Endod 2007;33: Nagasiri R, Chitmongkolsuk S: Long-term survival of endodontically treated molars without crown coverage: a retrospective cohort study. J Prosthet Dent 2005;93: Shafiei F, Memarpour M, Doozandeh M: Three-year clinical evaluation of cuspal coverage with combined composite-amalgam in endodontically-treated maxillary premolars. Oper Dent 2010;35: Sequeira-Byron P, Fedorowicz Z, Carter B, et al: Single crowns versus conventional fillings for the restoration of root-filled teeth. Cochrane Database Syst Rev 2015 Sep 25;9:CD Morimoto S, Rebello de Sampaio F, Braga M, et al: Survival rate of resin and ceramic inlays, onlays, and overlays: a systematic review and meta-analysis. J Dent Res 2016;95: Donovan T, Simonsen R, Guertin G, et al: Restrospective clinical evaluation of 1,314 cast gold restorations in service from 1 to 52 years. J Esthet Rest Dent 2004;16: Scotti N, Rota R, Scansetti M, et al: Influence of adhesive techniques on fracture resistance of endodontically treated premolars with various residual wall thicknesses. J Prosthet Dent 2013;110: Taha NA, Palamara JE, Messer HH: Cuspal deflection, strain and microleakage of endodontically treated premolar teeth restored with direct resin composites. J Dent 2009;37: Swift EJ, Stundervant JR, Boushell LW: Indirect tooth colored restorations. In Heymann HO, Swift EJ, Ritter AV (eds): Sturdevant s Art and Science of Operative Dentistry (ed 6). St. Louis, MO, Mosby Elsevier, 2013, pp Salaverry A, Borges GA, Mota EG, et al: Effect of resin cements and aging on cuspal deflection and fracture resistance of teeth restored with composite resin inlays. J Adhes Dent 2013;15: Magne P, Knezevic A: Influence of overlay restorative materials and load cusps on the fatigue resistance of endodontically treated molars. Quintessence Int 2009;40: Journal of Prosthodontics 00 (2016) 1 7 C 2016 by the American College of Prosthodontists 7