Fracture Resistance of Endodontically Treated Premolar Teeth with Extensive MOD Cavities Restored with Different Bulk Fill Composite Restorations (An In vitro Study)


Background: The present in-vitro study was undertaken to evaluate and compare fracture resistance of weakenedendodontically treated premolars with class II MOD cavities restored with different bulk fill composite restorations (EverXposterior, Alert, Tetric EvoCeram Bulk Fill, and SDR). The type and mode of fracture were also assessed for all theexperimental groups.Materials and Method: Forty-eight human adult maxillary premolar teeth were selected for this study. Standardizedextensive class II MOD cavities with endodontic treatment were prepared for all teeth, except those that were saved asintact control. The teeth were divided into six groups of eight teeth each (n=8): (Group 1) intact control group, (Group 2)unrestored teeth with endodontic treatment, (Group 3) restored with (TetricEvoCeram Bulk Fill), (Group 4) restored withSDR bulk-fill flowable composite, (Group 5) restored with EverX Posterior composite and (Group 6) restored with Alertcomposite. . All specimens were subjected to compressive axial loading until fracture in a universal testing machine. Thedata were statistically analyzed using one-way ANOVA test and LSD test. Macroscopic fracture type were observed andclassified into favorable and unfavorable. Specimens in groups 3, 4, 5 and 6 were examined by stereomicroscope at amagnification of 20× to evaluate the mode of failure into adhesive, cohesive or mixed.Results: The mean fracture load was (1.2505Kn) for group 1, (0.371Kn) for group 2, (0.512 Kn) for group 3, (0.6435 Kn) forgroup 4, (0.608 Kn) for group 5, and (0.8315) for group 6. Using one way ANOVA test a highly significant difference (P <0.01) were found among all groups. The use of Alert composite (which contain micro glass fiber) improved the fractureresistance significantly in comparison to other groups. SDR bulk-fill flowable composite showed better improvement infracture resistance but with no significant differences in comparison to EverX composite restoration (which contain ShortE-glass fiber filler). The type of failure was unfavorable for all the restored groups.Conclusion: All experimental composite restorations showed significant improvement in the resistance to cuspal fracturein comparison to unrestored one (group 2). However, under the conditions of this study, direct composite restorationsshould be considered as a valid interim restoration for weakened endodontically treated teeth before cuspal coveragecan be provided