Effect of monowave and polywave light curing on the degree of conversion and microhardness of composites with different photoinitiators: An in vitro study

AIM: The purpose of this study was to evaluate the effect of light-curing units (LCUs) on the degree of conversion (DC) and microhardness of composites with varying photoinitiator systems. MATERIALS AND METHODOLOGY: Two groups were formed based on LCU – monowave (Group M) and polywave (Group P). Each group was further divided into two subgroups based on photoinitiator systems – combination of camphorquinone (CQ), Ivocerin, and 2,4,6-trimethylbenzoyl diphenylphosphine oxide (Subgroup CIT) and only CQ (Subgroup C) in the composite. Samples prepared were 4 mm thick. Microhardness was measured at bottom surface by Vickers hardness tester, and DC was evaluated by Fourier transformation infrared spectroscopy. STATISTICAL ANALYSIS: Kolmogorov–Smirnov test was used. RESULTS: Both the mean microhardness and DC of composite in subgroup C were similar (P > 0.05) in Group M (52.42 ± 2.67 and 48.30 ± 5.81) and Group P (51.77 ± 1.96 and 48.50 ± 4.87). The mean microhardness of composite containing a combination of photoinitiators was more in Group P (57.09 ± 2.61) as compared to Group M (47.37 ± 3.51). The mean DC was higher in Group P (59.75 ± 5.30) as compared to Group M (39.70 ± 3.57), and these differences were statistically significant (P < 0.05). CONCLUSION: The type of LCU affects DC and microhardness only in the case of composites containing a combination of photoinitiators.