Restoring the bond strength of composite resin to bleached enamel with Epigallocatechin-3-gallate, Hypericin, and Resveratrol

Objective: This study investigated the effects of three herbal antioxidants on restoring the compromised bond strength of composite resin to bleached enamel.Methods: In this in vitro study, 50 extracted human central incisors were divided into five groups. Group A (negative control) received no bleaching or antioxidant treatment. The teeth in groups B to E were bleached and subjected to the following surface treatment: Group B (positive control): no surface treatment; Group C: application of 5% Epigallocatechin-3-gallate (EGCG); Group D: application of 10% Hypericin; and Group E: application of 10% Resveratrol. The antioxidant solutions were applied for 10 minutes. All specimens were restored with a nanohybrid composite resin, and shear bond strength (SBS) was measured 24 hours after restoration using a universal testing machine. Data were analyzed using one-way ANOVA and Tukey’s post hoc test with a significance set at P<0.05.Results: ANOVA revealed a significant difference in SBS among the groups (P=0.011). The bleaching alone (Group B) significantly reduced SBS compared to other groups (P< 0.05). All three antioxidants (5% EGCG, 10% Hypericin, 10% Resveratrol) fully restored SBS to the level of the non-bleached control (Group A), with no significant differences between them (P>0.05). Among antioxidants, 5% EGCG showed the highest mean SBS (5.06 ± 1.57 MPa), followed closely by 10% Hypericin (4.92 ± 1.05 MPa) and 10% Resveratrol (4.79 ± 1.16 MPa).Conclusions: All herbal antioxidants, including 5% EGCG, 10% Hypericin, and 10% Resveratrol, effectively improved the bond strength of composite resin to recently bleached enamel