Effect of intratooth location and thermomechanical cycling on microtensile bond strength of bulk-fill composite resin

CONTEXT: The initial bond strength and potential durability of an adhesive restoration are significantly affected by regional variations in dentin composition. AIM: The aim of this study is to evaluate the influence of dentin location and thermomechanical cyclic loading on microtensile bond strength of bulk-fill composite resin to coronal dentin. MATERIALS AND METHODS: Disto-occlusal cavity preparations were done on 60 extracted human mandibular molars with pulpal floor depth of 1.5 and 3.5 mm for superficial and deep dentin and 1.5 mm axial wall depth and are restored with bulk-fill restorative composite. Bond strength evaluation was done using universal testing machine, and mode of bond failure was observed under scanning electron microscope. STATISTICAL ANALYSIS: Statistical analyses were done using ANOVA and Tukey's multiple post hoc test. For comparison of failure mode, Mann–Whitney U-test was used. RESULTS: Superficial dentin has shown higher bond strength compared to deep dentin and gingival wall dentin (P = 0.001). The bond strength values decreased with the thermomechanical cycling (P = 0.001). Deep dentin and gingival dentin have exhibited more of adhesive failures. CONCLUSION: Bond strength of bulk-fill composite was negatively influenced by the depth of dentin and thermomechanical loading.