Stability of Bonded Resin Composite Restorations to Enamel after Bleaching with 20% Carbamide Peroxide

This study aimed to examine the effect of postoperative home bleaching using 20% carbamide peroxide on the shear bond strengths of different adhesives to enamel and to verify the failure mode for each test specimen.

One hundred sound human molars were used in this study. Bonding procedures were performed on the flattened buccal enamel surfaces according to the manufacturer's instructions. OptiBond Solo Plus adhesive (Kerr), Single Bond Universal adhesive (3M ESPE) applied with both the total-etch and self-etch techniques, and Tetric N-Bond Universal adhesive (Ivoclar Vivadent) applied with both the total-etch and self-etch techniques were used, followed by resin composite post fabrication (Filtek Z350 XT; 3M ESPE). All specimens were thermo-cycled for 5000 cycles and then divided into the control (non-bleach) and postoperative bleaching groups (20% carbamide peroxide). The shear bond strength values were measured and compared between the two groups. Data were analyzed using one-way analysis of variance with Tukey's test (p = 0.05). The failure modes of debonded specimens were evaluated using a digital microscope (50×). The bonding interfaces of the resin composite posts to different enamel conditions (control and postoperative bleaching) were observed by a scanning electron microscope (SEM) before the shear bond test.

The shear bond strength values of all tested adhesives were lower in the postoperative bleaching group than they were in the control (non-bleach) group, particularly the bond strength values of self-etch adhesives.

The stability of bonded resin composite restorations to enamel, using different dental adhesives, could be compromised after the bleaching procedure at varying sensitivity levels.

Replacement of bonded resin composite restorations to enamel might be considered after bleaching procedures, especially if these restorations were previously bonded with self-etch adhesives.