Effect of Office Bleaching on Enamel Bonding Performance

Purpose: To evaluate the effect of in-office bleaching on enamel microshear bond strength (µSBS) 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 µSBS 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 µSBSs even after PA etching with both SE2 and GP (p ≤ 0.005). However, there were no significant differences in µSBS between groups with and without PA etching, except for SE2 without bleaching, in which the µSBS 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 µSBSs were adversely affected by in-office bleaching. Thick ABRZs were created with bleaching and PA treatment. Keywords: office bleaching, ABRZ, microshear bond strength.