effect of hydrogel and solution forms of sodium ascorbate on microleakage of composite restorations immediately after non-vital bleaching

objective: the present in vitro study was undertaken to compare the effects of hydrogel and solution forms of sodium ascorbate on microleakage of composite restorations subsequent to a non-vital bleaching procedure with 10% carbamide peroxide. materials and methods: forty-eight sound extracted human maxillary incisors were obtained. following root canal therapy, the teeth were randomly divided into an unbleached control group (group 1) and three experimental groups in which bleaching was performed (12 teeth in each group). non-vital bleaching with 10% carbamide peroxide was carried out for periods of 8 hours a day for one week. in group 2, the specimens were restored immediately after bleaching. group 3 specimens were treated with sodium ascorbate solution, whereas in group 4 specimens, sodium ascorbate hydrogel was used before placement of composite restorations. following thermocycling, the specimens were subjected to dye leakage (methylene blue) test. statistical analysis was carried out using kruskal- wallis and dunn multiple comparison tests at a significance level of p<0.05. results: significant differences existed in microleakage scores among the four groups (p<0.0005). pairwise comparison of groups with dunn test revealed that higher microleakage scores in group 2 compared to each of the other three groups was statistically significant (p<0.001) while the differences between other groups were not statistically significant (p>0.05). conclusion: ten percent carbamide peroxide significantly increases microleakage of composite restorations when bonding is performed immediately following non-vital bleaching. compromised sealing ability of composite restorations is reversed with application of both forms (hydrogel and solution) of sodium ascorbate, as an anti-oxidant.