Influence of light and laser activation of tooth bleaching systems on enamel microhardness and surface roughness.

Abstract

Objective:The objective of this study was to compare the effects of light and laser activation of in-office tooth bleaching systems on enamel microhardness and surface roughness.Materials and Methods:Twenty-five enamel slabs were divided into three treatment groups: light-activated bleaching, laser-activated bleaching, and control. The baseline data were recorded for enamel microhardness (Vickers microhardness [VMH]) and surface roughness (Roughness average, Ra). The specimens were cured for 10 min upon hydrogen peroxide application for the light-activated bleaching group and activated with a laser source, 8 cycles, 10 s per cycle for the laser-activated group. The changes in VMH and Ra at days 1, 7, and 28 were evaluated. Kruskal–Wallis, Friedman, Wilcoxon, and Mann–Whitney tests were used to analyze both VMH and Ra between the treatment groups at different time intervals.Results:There were a significant reduction in VMH values and significant differences between days 1, 7, and 28 against the baseline in the light-activated bleaching group (P = 0.001). The Ra values revealed significant differences in both light- (P = 0.001) and laser-activated (P = 0.033) groups.Conclusion:Light activation of a bleaching agent caused a reduction in enamel microhardness and an increase in surface roughness when compared to laser activation.