Evaluation of bond strength durability on bleached human dentin

This study evaluated the effect of aging on the microtensile bond strength (μTBS) between composite resin and human dentin bleached with 35% hydrogen peroxide (HP) or 10% carbamide peroxide (CP). Thirty intact extracted third molars were selected for the study. After the dentin surface was exposed, the smear layer was abraded with silicon carbide paper to ensure standardization. The teeth were randomly divided into 3 groups: 1 (G1), no treatment (control); 2 (G2), dentin bleached with CP (at-home bleaching); and 3 (G3), dentin bleached with HP (in-office bleaching). G2 and G3 were bleached according to the manufacturers' instructions and stored in distilled water for 21 days. The teeth in all 3 groups were then bonded with a dental bonding agent and nanohybrid composite resin. Each tooth was sectioned and divided into groups to allow evaluations at 3 time periods: 24 hours, 6 months, and 12 months. The specimens were stored in distilled water at 37°C ± 1°C until use. The μTBS of the specimens was tested on a universal testing machine. Fracture mode analysis was performed with a stereoscopic loupe. The data were analyzed statistically by 2-way analyses of variance and Tukey tests. After 24 hours, G3 had a significantly lower mean [SD] μTBS value (20.00 [5.67] MPa) than G1 (31.14 [8.83] MPa), but their means were statistically similar at 6 months (29.42 [7.72] MPa vs 22.97 [7.48] MPa, respectively). Tukey tests revealed that there was no statistically significant change in μTBS over time for G2 or G3. After 12 months of aging, only G1 specimens showed statistically lower μTBS values compared with the 24-hour time period (P < 0.05). Based on the results, the durability of the bond between composite resin and dentin is not affected by the choice of bleaching treatment.