Impact of the Different Application Times of Natural Antioxidants on Shear Bond Strength of Resin Composite to Bleached Enamel Surface

Natural antioxidants present a viable option for instant bonding by counteracting free radicals and reinstating composite to bleached enamel adhesion. The aim of this study was to evaluate the impact of varying application durations (10, 15, and 20 minutes) of two types of natural antioxidants ethanolic extracts (Moringa oleifera and Salvadora persica) on Shear Bond Strength (SBS) of resin composite to bleached enamel. Methods: the 108 extracted premolar teeth were randomly allocated into nine groups: unbleached enamel (control), bleached enamel with delayed bonding (one-week post bleaching), and six groups treated with Moringa oleifera or Salvadora persica extracts for durations of 10, 15, or 20 minutes. The shear bond strength was evaluated with a universal testing machine, failure mode analysis done by using a stereomicroscope. Results: Bleaching significantly diminished shear bond strength (SBS) in comparison to unbleached enamel (6.39 MPa vs. 26.22 MPa) at (p≤0.05). The delayed bonding group demonstrated partial SBS recovery of 17.43 MPa. The utilization of natural antioxidants markedly enhanced shear bond strength, with prolonged exposure durations resulting in increased bond strengths. Moringa oleifera (19.00 MPa at 20 minutes) surpassed Salvadora persica (17.51 MPa at 20 minutes). Failure mode analysis revealed heightened cohesive failures in the antioxidant-treated groups, refereed to the enhanced bond strength. Conclusion: Natural antioxidants promptly reestablish SBS post-bleaching, presenting a clinically feasible alternative to deferred bonding. Moringa oleifera exhibited enhanced effectiveness, indicating its promise for prompt restorative interventions following bleaching. Subsequent research ought to refine application techniques and investigate the long-term impacts on bond durability.