Objective: To evaluate the fracture resistance of maxillary premolars weakened by MOD cavities and restored with nanohybrid composite, bulk fill composite and two fiber reinforced composites.
Materials and Methods: A total of 60 sound maxillary first premolars with standardized MOD cavities were used for this study, except for intact control. Specimens were randomly divided into six groups (n=10); G1: sound premolars (negative control); G2: unrestored teeth (positive control); G3: MOD cavities restored with nanohybrid composite. G4: MOD cavities restored with sonicfill bulk fill composite.; G5: MOD cavities restored with nanohybrid resin composite with glass fibers embedded into it from bucco-lingually.; G6: MOD cavities restored with short-fiber reinforced resin composite. All specimens were subjected to thermocycling between 5Cº to 55Cº in water bath for a total of 2000 cycle with 10 seconds dwell time. Then specimens were individually mounted on a computer-controlled material testing machine (Instron 3345) with a load cell of 5 kN and the maximum load to produce fracture in Newton (N) was recorded and statistical analysis was performed.
Results: Kruskall-Wallis test and Bonferroni-corrected Mann-Whitney U test showed that there was a statistically significant difference between the different study groups (P=0.000). Positive control and short fiber reinforced composite groups yielded the significantly highest mean values; followed by nanohybrid resin composite, sonic fill bulk fill composite and fiber reinforced composite groups that were statistically similar. While the negative control had the significantly lowest mean value.
Conclusion: The use of short fiber reinforced resin composite as restoration significantly increased the fracture strength of premolars with MOD restorations.