Effect of Office Bleaching on Enamel Bonding Performance.

PURPOSE: To evaluate the effect of in-office bleaching on enamel microshear bond strength (microSBS) of two self-etch adhesives (SEA). MATERIALS AND METHODS: For the bleaching group, bovine enamel surfaces were treated with a bleaching agent and divided into two main groups: one in which adhesive was applied immediately after bleaching and another in which adhesive was applied after one week. Enamel was bonded using the following procedures: group 1: application of a two-step SEA (Clearfil SE Bond 2, SE2, Kuraray Noritake); group 2: etching with 40% phosphoric acid (PA) and application of SE2;.group 3: application of a one-step SEA (G-Premio Bond, GP, GC); group 4: etching with PA and application of GP. Resin composite was placed and microSBS was measured at 24 h (immediately) and 1 week after bleaching. Acid-base resistant zones (ABRZ) were observed under SEM. Three-way ANOVA was used for data analysis. RESULTS: Bleaching significantly decreased the microSBSs even after PA etching with both SE2 and GP (p </= 0.005). However, there were no significant differences in microSBS between groups with and without PA etching, except for SE2 without bleaching, in which the microSBS significantly increased with PA etching (p < 0.005). Thick ABRZs were found in SE2 and GP after bleaching, which exhibited an irregular wave-like shape for PA-treated specimens. CONCLUSION: The enamel microSBSs were adversely affected by in-office bleaching. Thick ABRZs were created with bleaching and PA treatment.