Effect of Bleaching Treatment and Reduced Application Time of an Antioxidant on Bond Strength to Bleached Enamel and Subjacent Dentin

Purpose: To evaluate the influence of bleaching on bond strength to enamel and subjacent dentin, and to determine whether a reduced application time (1 min) of the antioxidizing agent can obviate the compromised bond strength after bleaching. Materials and Methods: One hundred twelve bovine incisors were obtained, and the enamel and dentin surfaces were standardized to a thickness of 1 mm. The specimens were divided into two control groups (enamel and dentin without treatment) and 12 experimental groups (n = 10), based on the concentration of bleaching agents (carbamide peroxide 16% and hydrogen peroxide 35%), time interval between bleaching and restorative procedures (24 h; 24 h + sodium ascorbate (SA) 10%/1 min; 14 days), and substrate (enamel or dentin). All samples were submitted to the bleaching treatment on enamel. After the stipulated interval, a microshear test was performed. Results: The bleaching treatment compromised the bond strength to the enamel when the restoration was performed 24 h after the end of bleaching. The bond strength to dentin was not affected by bleaching. Conclusions: The SA 10% application for 1 min obviates the detrimental effect of bleaching on bond strength. The bleaching performed on enamel does not affect the bond strength to the subjacent dentin. Keywords: tooth bleaching, carbamide peroxide, hydrogen peroxide, bond strength, sodium ascorbate, adhesive system, enamel, dentin