Fracture Resistance of Maxillary Premolars Restored with Different Dentin Replacement Protocols

Abstract

Objectives: The aim of this research was to investigate the fracture resistance of premolar teeth with standardized mesioocclusodistal (MOD) cavities restored with different dentin replacement protocols. Materials and Methods: Sixty sound maxillary premolar teeth with standardized MOD cavities were assigned to six groups (n=10): G1: sound teeth (positive control); G2: unrestored premolars with MOD cavities (negative control); G3: restored incrementally with nanohybrid resin composite; G4: restored by bulk fill flowable followed by nanohybrid resin composite; G5: restored with packable fiber-reinforced composite followed by nanohybrid resin composite and G6: restored with flowable fiber-reinforced composite followed by nanohybrid resin composite. After being thermocycled at 37oC, 4mm diameter steel sphere was used in a universal testing machine to apply stresses on specimens at a cross-head speed of 5mm/min until fracture occurred. The results were statistically analyzed with statistical significance set at (P ≤ 0.05).Results: Intergroup comparison has shown statistically significant difference (P < 0.001). The highest fracture resistance was in G5 followed by G1 (natural tooth) then G6 with no difference between them. G4 and G3 showed intermediate results, which was statistically lower than G1, G5 and G6. The least fracture resistance was in G2 (unrestored MOD cavity), which was statistically lower than all groups.Conclusions: using fiber-reinforced composite (either packable or flowable) as dentin substitute material under resin composite is considered a perfect choice to restore fracture resistance of maxillary premolars with MOD cavities.