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. Methods: Conventional halogen light (40 seconds) and a light-emitting diode (LED) curing unit (20 seconds) were used to polymerize seven different composite brands. A total number of 70 specimens were evaluated (n = 5). To determine the DC, Fourier transformation infrared spectroscopy was used. For statistical analysis, two-way analysis of variance and Tukey's honestly significant difference post hoc test were applied (alpha = 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 (nanofilled, macrofilled, hybrid, micro-hybrid and organically modified ceramics).