bond strength of composite resin to bleached dentin: effect of using antioxidant versus buffering agent

objective : application of sodium ascorbate as an antioxidant and calcium hydroxide as a buffering agent following intracoronal bleaching has been recommended. the aim of this study was to investigate the effect of using the mentioned materials on shear bond strength of composite resin to the bleached dentin. materials and methods: in this in vitro investigation, sixty human sound premolars were divided randomly into five groups (n=12). occlusal dentin surfaces were exposed. the negative control (nc) group was  not bleached and the other groups were bleached with 35% hydrogen peroxide gel for 5 days. afterwards, composite cylinders were built up in the positive control (pc) group immediately after bleaching, in the delay bonding (db) group after one week, in the sodium ascorbate (sa) and calcium hydroxide (ch) groups after 40 hours of treatment with the materials. then, the samples were stored in 37°c for 24 hours. the specimens were thermocycled (5-55°c, 500 cycles), subjected to shear bond testing by universal machine. the data were analyzed by one-way anova and duncan tests ( =0.05). results: there was a significant difference between pc and ch groups in comparison with the other groups (p<0.05), but the difference among other groups was not significant (p>0.05). conclusion: application of sodium ascorbate could significantly increase the bond strength of composite resin to bleached dentin, while the use of calcium hydroxide did not affect bond strength.