Evaluation of Human Dental Enamel Microhardness after Office Bleaching with Diode Laser and LED Light Compared with the Conventional Technique

Objective: Tooth bleaching is a very popular treatment procedure for patients. The procedure can be carried out with different light sources. However, one of the possible complications of vital bleaching is a change in enamel microhardness. The present study aimed to evaluate human dental enamel microhardness after office bleaching with diode laser and LED light compared to the conventional bleaching procedure. Methods: Thirty-nine human premolar teeth were randomly assigned to three groups in terms of the bleaching technique. Snow O bleaching gel was used in group 1 with an LED light-curing unit; Snow L bleaching gel was used in group 2 with diode laser irradiation; and Opalescence Boost bleaching gel was used with no light source in group 3. Enamel surface changes were evaluated in one tooth in each study group and one intact tooth as a reference under a scanning electron microscope (SEM). In the remaining samples (n=12), samples? microhardness was determined with a Vickers unit before and after bleaching. Repeated-measures ANOVA was used to compare microhardness changes, followed by post hoc Tukey tests at the 0.05 significance level. Results: Enamel microhardness decreased in all the groups after bleaching, with the maximum decrease in microhardness in the Snow O bleaching group with LED light, which was significantly higher than the other groups (P=0.002). The two other groups did not exhibit any significant difference in microhardness decrease (P>0.05). Conclusion: Considering the present study results, power bleaching with 980nm diode laser was less time-consuming compare to conventional bleaching procedure and yielded better outcomes in terms of enamel surface microhardness compared to the use of an LED light-curing unit.