The comparative evaluation of effect of three natural antioxidants on the bond strength of composite resin to bleached enamel – an in-vitro study

Background: Tooth discolorations frequently affect people of various age groups and are multifactorial in nature. Increasing demand in aesthetic dentistry has resulted in the widespread practice of extra-coronal bleaching or vital bleaching. An important complication following bleaching is decreased bond strength of composite resin to bleached enamel when bonding immediately after the bleaching process. The use of antioxidants immediately after bleaching showed increased bond strength to bleached enamel. Hence, the main aim of the present study was to determine the effect of antioxidants, namely 10% Tulsi leaf extract, 10% Olive leaf extract &10% Pine Bark extract on the shear bond strength of composite resin to bleached enamel. Materials & method: Ninety freshly extracted human anterior teeth were divided into five groups: GroupI(n=18) – bleaching with 35% hydrogen peroxide gel (without antioxidant), GroupII(n=18) - bleaching with application of 10% Tulsi leaf extract, GroupIII(n=18) - bleaching with application of 10% Olive leaf extract, Group IV(n=18) – bleaching with application of 10% Pine Bark extract, and Group V(n=18) - control group i.e., no bleaching. These groups were further subdivided into two subgroups based on whether composite build-up was done immediately (Subgroup A) or after a delay of 2 weeks (Subgroup B). Shear bond strength of the specimens were tested using universal testing machine. Data were statistically analysed using Two-way ANOVA test & Tukey's multiple posthoc test and independent t test. Result: There were statistically significant differences between shear bond strength of control groups & experimental groups and also among the experimental groups. Conclusion: The use of antioxidants effectively reversed the compromised bond strength of bleached enamel. Among the natural antioxidants, 10% pine bark extract application after bleaching showed better bond strength.