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/cm2) and low (650 mW/cm2) 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/cm2) 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/cm2). 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.