ABSTRACT
As dentin bond strength of the materials containing resin is reduced after bleaching, a delay in bonding for at least one week after bleaching is recommended. The aim of this study was to investigate the neutralizing effect of an antioxidizing agent on the shear bond strength [sbs] of bleached dentin and compare it with a delay of one week before bonding of composite resin [CR] and resin-modified glass-ionomer [RMGI]. Exposed dentin surfaces of 96 sound human molars were divided into eight groups. Buccal dentin surfaces of the specimens in group 1 and 5 were consecutively bonded with CR and RMGI cylinders. The specimens in other groups were bleached for six hours a day for five consecutive days. For the specimens in groups 2 and 6, bonding of CR and RMGI was performed immediately after bleaching, respectively. The specimens in groups 3 and 7 were immersed in distilled water for one week and then CR and RMGI were bonded. For the specimens in groups 4 and 8, 10% sodium ascorbate gel was applied and then CR and RMGI were bonded, respectively. Shear bond strengths of the specimens were measured. Data was analyzed by ANOVA and Tukey test [? = 0.05]. The mean sbs values for groups 1 to 5, 7, and 8 in MPa were 17.055 +/- 2.954, 8.19 +/- 0.941, 16.406 +/- 1.508, 15.640 +/- 3.073, 8.893 +/- 0.620, 8.162 +/- 0.975, 7.584 +/- 0.939, respectively. There were significant differences between the study groups. The specimens of group 6 had pretest failure. Bleaching led to a significant decrease in sbs of CR to dentin immediately after bleaching, and RMGI did not bond in this situation. A delay of one week before bonding and application of sodium ascorbate gel significantly increased the sbs of the evaluated materials to bleached dentin. In the composite groups the delayed subgroup had significantly higher sbs than the sodium ascorbate subgroup. In glass-ionomer groups there were no significant differences in sbs values