Bond Strength of Restorative Material to Dentin Submitted to Bleaching and Er: YAG Laser Post-Treatment

Objective: The purpose of this study was to assess the bond strength of a restorative material to bleached dentin, pretreated with Er:YAG laser. Background data: Laser irradiation for dental surface treatment may increase the bond strength of restorative material to tooth surface. There are no reports of using Er: YAG laser on dentin bleached with 35% hydrogen peroxide. Methods: Forty maxillary canines were sectioned, resulting in 80 fragments (5x5 mm) of intracoronary dentin that were divided into eight groups (n = 10) according to the dental bleaching (present or not), surface conditioning (with or without laser) and the post-bleaching time to perform restoration (immediately or 7 days). The bleached specimens received two applications of 38% hydrogen peroxide. Er: YAG laser was applied for 20 sec with 400 mJ/15 Hz. Restorative procedure was performed using phosphoric acid, an adhesive system, and resin using a split Teflon matrix. The specimens were submitted to shear bond strength test and the data (MPa) were analyzed by ANOVA and Tukey's test (alpha = 0.05). Results: There were significant differences among the three factors (p < 0.05). The highest values were obtained for unbleached specimens compared with bleached, for those treated with laser compared with those only conditioned with acid, and for those restored after 7 days compared with those having immediate restoration. In the interaction of factors, the bleached specimens treated with laser and restored immediately were statistically similar (p > 0.05) to those bleached and restored after 7 days. Conclusions: Er: YAG laser can restore the bond strength of the dentin/restorative material interface even if the restoration is performed immediately after bleaching.