Effect of antioxidant treatment on bond strength of a luting resin to bleached enamel

Purpose The aim of this study was to comparatively investigate the effect of antioxidant treatment and delayed bonding after bleaching with carbamide peroxide on the shear bond strength (SBS) of a luting resin to enamel. Materials and methods Forty flat enamel surfaces were prepared from freshly extracted human molars using a low speed diamond saw, then divided into three bleaching groups (n = 10/group) and a control group (n = 10). Group 1 consisted of specimens bonded immediately after bleaching. Group 2 specimens were treated with an antioxidant agent, 10% sodium ascorbate, while Group 3 specimens were immersed in artificial saliva for 1 week after bleaching. Specimens in Group 4 were not bleached, but immersed in artificial saliva for 1 week before bonding. Forty ceramic blocks (Empress 2, Ivoclar) were prepared and luted to teeth using a dual-curing resin cement (Variolink II, Ivoclar). The specimens were thermocycled and the SBS tests were performed using a universal testing machine (crosshead speed: 0.5 mm/min). Fracture analysis of the bonded surfaces was done using a scanning electron microscope. Statistical analysis was carried out by Kruskall–Wallis and Mann–Whitney U-tests. Results While the samples that were immediately bonded after bleaching (Group I) demonstrated significantly lower shear bond strengths and 10% sodium ascorbate group (Group II) demonstrated significantly higher bond strengths than control group samples (p < 0.05), no significant differences were found among delayed bonded group and control group (p > 0.05). Conclusion Using sodium ascorbate with a concentration of 10% may be reliable for reversing the compromised bond strength.