Comparative evaluation of effects of natural antioxidants on the shear bond strength of composite resin to bleached enamel

Context: The use of antioxidants immediately after bleaching showed increased bond strength. Aims: This study aimed to compare the effects of natural antioxidants on the shear bond strength of composite resin to bleached enamel. Materials and Methods: Fifty extracted single-rooted upper incisors were decoronated by sectioning the roots 2 mm below the cementoenamel junction, and then, crowns were embedded in autopolymerizing acrylic resin block (3.0 cm × 3.0 cm × 3.0 cm) with the labial surface exposed. They were randomly divided into five groups, depending on the type of antioxidant used (n = 10): (i) Group 1: control (no bleaching), (ii) Group 2: bleaching only, (iii) Group 3: bleaching + 10% sodium ascorbate (antioxidant), (iv) Group 4: bleaching + green tea, and (v) Group 5: bleaching + white tea. Labial surfaces of 40 teeth were bleached with 38% hydrogen peroxide for 20 min following manufacturer's instructions. After that, the experimental groups (Groups 3, 4, and 5) were treated with respective antioxidant solutions before composite restorations were done using a cylindrical plastic mold (3 mm × 5 mm). Shear bond strength of the specimens was tested under universal testing machine. Statistical Analysis: Data were analyzed with ANOVA and Tukey's post hoc test. Results: There were statistically significant differences between shear bond strength of control groups (Groups 1 and 2) and experimental groups (P < 0.05), but no significant difference in bond strength was observed among the antioxidants used. Conclusion: Application of antioxidants immediately after bleaching showed increased bond strength. Green tea and white tea extract can be used as alternative antioxidants in improving the bond strength of enamel.