Diode laser effect on enamel microhardness after dental bleaching associated with fluoride.

OBJECTIVE: The aim of this in vitro study was to evaluate the effects of diode laser irradiation on human dental enamel treated by bleaching and acidulated phosphate fluoride gels (APF) according to microhardness analysis. BACKGROUND DATA: The high interest of patients for aesthetics in cosmetic dentistry has led to new bleaching materials and the development of new techniques. MATERIALS AND METHODS: Sixty embedded, flattened human third molar enamel fragments were randomly assigned to three groups (n=20). Group 1 received topical application of 1.23% APF photoactivated using a diode laser. Group 2 received three applications of 35% hydrogen peroxide for 5 min and was photoactivated with laser for 30 s in each application. Group 3 treated the same as group 2 plus a 1.23% APF application for 1 min after bleaching followed by 30 s of laser irradiation. Microhardness analyses were performed before and after all the treatments. RESULTS: Analysis of variance followed by Tukey and Student statistical t-tests (p<0.05) showed significantly higher microhardness values for group 1 after treatment. No significant differences were shown before and after treatments for groups 2 and 3. CONCLUSION: No change was observed in enamel microhardness after treatment with hydrogen peroxide gel photoactivated using diode laser with or without APF. There was an increase in microhardness when enamel was treated only with APF photoactivated using a laser.