Effect of Light Curing Mode and Type on Conversion of Resin Composites.

Objective To determine the efficacy of polymerization for two different curing units by examining the degree of conversion (DC) of seven different composite materials. Materials and methods Conventional halogen light (40 s) and a light-emitting diode curing unit (LED) [20 s] were used to polymerize seven different composite brands. A total number of 70 specimens were evaluated (n = 5). To determine the degree of conversion, Fourier transformation infrared spectroscopy was used. For statistical analysis, two-way analysis of variance (ANOVA) and Tukey's HSD post hoc test were applied (α = 0.05). Results Degree of conversion varied with both the light unit and type of composite, with significant interactions. Charisma (67.0 ± 6.0) and Z-250 (65.2 ± 3.3) showed the highest DC when cured using the LED, whereas Grandio (38.2 ± 3.5) showed the lowest when exposed to the conventional halogen light. Conclusion Degree of conversion was affected by the type of light curing units and results varied greatly with respect to composite brand and type (nonofilled, macrofilled, hybrid, microhybrid and ormocer).