in-vitro evaluation of the effect of herbal antioxidants on shear bond strength of composite resin to bleached enamel

objectives: a reduction in bond strength of composite to bleached enamel has been reported immediately after bleaching treatment. application of some antioxidant agents may decrease the adverse effects of whitening agents on bond strength and enhance composite bond to enamel. this study aimed to assess the effect of green tea, sodium ascorbate, sage and grape seed extract on bond strength of composite to bleached enamel. materials and methods: in this in-vitro study, 90 human enamel surfaces were randomly divided into six groups as follows (n=15): g1, no bleaching; g2, bleaching with 40% hydrogen peroxide (hp); g3, hp+1000 μmol epigallocatechin gallate (egcg) for 10 minutes; g4, hp+10% sodium ascorbate for 10 minutes; g5, hp+10% sage for 10 minutes and g6, hp+5% grape seed extract for 10 minutes. the specimens were bonded to composite in all groups. the shear bond strength of specimens was measured in megapascals (mpa). data were analyzed using one-way anova and tukey’s hsd test (α=0.05). results: the highest and the lowest mean shear bond strength values were observed in group 1 (22.61±3.29mpa) and group 2 (5.87±1.80mpa), respectively. the reduction in bond strength in group 2 was greater than that in other groups (p<0.001). no significant difference was found among groups 1, 3, 4, 5 and 6 (p>0.05).  conclusions: all the herbal antioxidants used in this study equally compensated for the reduced bond strength of composite to bleached enamel. keywords: antioxidants; tooth bleaching; composite resins; shear strength