Comparative Evaluation of Different Designs of Mesio-occlusal-distal Cavities and Different Composite Systems on Fracture Resistance: An In Vitro Study

Aim:The purpose of the present study was to evaluate and compare the effects of two types of cavity designs and different types of composites on the fracture resistance of mesio-occlusal-distal (MOD) cavities.Materials and methods: Ninety maxillary premolars were selected.Ten samples were used as negative controls.The remaining 80 samples were divided into two groups: group I, samples with cavity width of 1/2 the intercuspal width; and group II, samples with cavity width of 2/3 the intercuspal width.Ten samples from each group were left unrestored and used as positive controls.The remaining 30 samples of each group were further distributed into three subgroups: subgroup A, restored with Tetric N-Ceram (bulk-fill composite) (TNC-BFC); subgroup B, TNC-BFC + Interlig fibers (Angelus); and subgroup C, GC EverX Posterior (EXP) (FRC).An Instron universal testing machine (UTM) was used to evaluate the fracture resistance.The data were tabulated and subjected to statistical analysis.Results: Intergroup and intragroup analyses showed significant differences in fracture resistance.All the experimental subgroups showed significantly greater fracture resistance compared to their respective positive controls and reduced fracture toughness compared to the negative control, except group IC, which showed similar results to intact teeth. Conclusion:Considering the limitations of the study, it may be concluded that fracture resistance is affected by different designs of MOD cavities in upper premolars and that using short fiber-reinforced composites as a restoration for weakened premolars can significantly reinforce the teeth with improved fracture resistance.Clinical significance: Fiber-reinforced composite can restore the fracture resistance of a tooth in extensive cavity designs.