The effect of curing intensity on mechanical properties of different bulk-fill composite resins

Objective: The purpose of this study was to investigate the effects of two curing light intensities on the mechanical properties (Vickers microhardness, compressive strength, and diametral tensile strength) of bulk-fill resin-based composites (RBCs). Materials and methods: Four commercially available bulk-fill RBCs (Tetric ® N-Ceram, SonicFill™, Smart Dentin Replacement (SDR™) Posterior Flowable Material, and Filtek™ Posterior Restorative) were used in this study. A total of 72 cylindrical specimens of each RBC (n=288) were prepared and subjected to Vickers microhardness, compressive strength, and diametral tensile strength tests at high (1200 mW/cm 2 ) and low (650 mW/cm 2 ) curing light intensities (each n=12). Results were evaluated using independent and paired sample t -tests, one-way analysis of variance, and Tukey’s post hoc test. All tests were performed at a significance level of P <0.05. Results: The highest mean microhardness was observed for SonicFill (58.3 Vickers hardness number [VHN]) cured using high-intensity light. Although having the least mean microhardness values, a significant difference was observed between SDR cured using high-intensity light and that cured using low-intensity light ( P <0.05). In the total sample, the highest mean compressive strength was obtained for SonicFill (262.6 MPa), followed by SDR (253.2 MPa), both cured using high-intensity light, and the least was measured for Tetric N-Ceram cured using low-intensity light (214.3 MPa). At high and low curing light intensities, diametral tensile strength for all RBCs except SonicFill was significant ( P <0.001). Conclusion: A higher curing light intensity (1200 mW/cm 2 ) had a positive influence on the compressive and tensile strength of the four bulk-fill RBCs and microhardness of two materials tested compared with lower curing light intensity (650 mW/cm 2 ). SonicFill showed the greatest microhardness and compressive strength significantly for both curing light intensities and greater diametral tensile strength with high-intensity light, although not significant. SDR cured with high-intensity light showed the greatest diametral tensile strength among the four materials.