Influence of various antioxidants on micro-shear bond strength of resin composite to bleached enamel

Teeth bleaching causes an immediate decrease in resin composite bonding ability. This study aimed to investigate the influence of various antioxidants on resin composite bond strength to bleached enamel.

One hundred and ten human maxillary incisors were used. A negative control (group A) (n = 10) was assigned (no bleaching-no antioxidant). The remaining teeth were divided into two groups (n = 50) according to the bleaching agent used: group B (40% hydrogen peroxide) and group C (35% carbamide peroxide). Both groups were subdivided into five subgroups (n = 10). A positive control subgroup (no antioxidant) and other four subgroups according to the antioxidant solution used (10% sodium ascorbate, 10% grape seed extract, 10% green tea extract, and 5% alpha-lipoic acid). After resin composite building, the micro-shear bond strength test was performed. Fracture analysis was examined using a stereomicroscope. Statistical analysis was performed using a two-way analysis of variance and Tukey's HSD post hoc test.

Bond strength significantly decreased after bleaching and there was no significant difference between bleaching agents (P < .0848). Except for alpha-lipoic acid subgroups, the other antioxidants subgroups revealed significantly higher bond strengths than bleached control subgroups (P < .0001).

All antioxidants used except alpha-lipoic acid were effective in the reversal of compromised bonding after bleaching.

Immediate bonding procedures after bleaching are requisite when bleaching fails to treat teeth discoloration and the direct composite veneer is considered, also when shades of old composite restorations become mismatched after bleaching and should be replaced. Immediate reestablishment of resin bond strengths after bleaching can be achieved by using several antioxidants without the need for delay.