Effect of Different LED Light-curing Units on Degree of Conversion and Microhardness of Bulk-fill Composite Resin.

AIM: The aim of this study is to compare the effect of the use of second-generation and third-generation LED light-curing units (LCUs) on the degree of conversion (DC) and microhardness (VHN) of bulk-fill resin composites. MATERIALS AND METHODS: Thirty cylindrical specimens (each n = 5) of Tetric N-Ceram Bulk-Fill, Filtek Bulk-Fill Posterior Restorative, and SDR flow were prepared in metal molds (5 mm in diameter and 4 mm in thickness) and cured with second-generation LED (SmartLite(R) Focus(R), Dentsply Sirona) and third-generation LED (Bluephase(R) style, Ivoclar Vivadent) resulting in six groups. Degree of conversion was determined using Fourier transform infrared spectroscopy (FTIR), and microhardness with Vickers microhardness tester. Data were statistically analyzed using one-way ANOVA and least significance difference (LSD) test, and DC and microhardness were correlated using Pearson's correlation (alpha = 0.05). RESULTS: There was a significant difference between DC and VHN between all groups of bulk-fill which were cured by second-generation LED curing light and third-generation LED curing light. Then there is no significant difference between DC of the three composite bulk-fill resins by (second-generation LED vs third-generation LED curing light). CONCLUSION: The second-generation LED curing light can still be used to cure bulk-fill resin composites by increasing the duration of irradiation. CLINICAL SIGNIFICANCE: In the microhardness test, there was a significant difference in the Filtek Bulk-Fill Posterior Restorative resin composites.