The effect of power bleaching on enamel microhardness activated by three different light sources: An in vitro study

Aims and Objectives: The aim of this study was to evaluate and compare the effect of power bleaching on human enamel microhardness activated by three different light sources, namely the light emitting diode (LED), diode laser, and neodymium: Yttrium-aluminium-garnet (Nd: YAG) laser. Materials and Methods: Fifty enamel samples were randomly divided into five test groups each containing 10 samples (n = 10). The enamel surfaces of samples were polished and baseline Vickers microhardness values were evaluated. Control group samples were untreated and stored in artificial saliva. Experimental groups were subdivided into four groups based on bleaching treatment carried out. Enamel samples were treated with 40% hydrogen peroxide gel for 2 cycles of 20 min per bleach cycle (with and without light activation). Microhardness was reassessed on 1 st , 7 th , and 21 st day after storage in artificial saliva. Results were subjected to statistical analysis using one-way analysis of variance (ANOVA) and t-test. Results: There was a statistically significant difference present in enamel microhardness values compared to the unbleached and bleached group. On comparing 1 st and 7 th day to the baseline values there was a statistically significant difference in all the experimental groups. No statistically significant difference existed between the baseline values and 21 st day. Conclusion: Activation with various light sources (LED/diode laser/Nd: YAG laser) do not have additional deleterious effects on enamel microhardness and thus can be used safely to hasten the bleaching procedure.