Effect of the concentration of hydrogen peroxide on the color and surface of the resin bracket

Abstract

Abstract Objectives. This study aimed to evaluate the whitening effect, shear bond strength (SBS) with the enamel surface, microhardness, and microstructure of discolored resin brackets following whitening treatment with various concentrations of hydrogen peroxide (HP). Materials and methods. Resin brackets were bonded to the enamel surface and discolored with a curry solution. Control (distilled water) and experimental solutions of 8.7, 17.5, and 35% HP were applied to the discolored resin brackets for 15 min. Resin brackets were then stored in distilled water for a week by repeating this whitening process thrice. The whitening efficacy was evaluated according to ISO 28399:2011. The SBS was measured using a universal testing machine. The microhardness and microstructure of the resin brackets were observed using a microhardness tester and field-emission scanning electron microscopy (FE-SEM). All the results were analyzed using a one-way analysis of variance analysis and Tukey’s post-hoc test (p=0.05). Results. All the experimental groups demonstrated a significant whitening effect on the discolored resin brackets compared to the control group (p<0.05). In particular, 35% HP showed faster color changes than the other groups (p<0.05). The microhardness of the resin bracket was lower in 35% HP than in the control group (p<0.05). FE-SEM analysis revealed no significant difference between groups. Conclusions. HP application at > 8.7% and < 17.5% concentrations whitens discolored resin brackets while not deteriorating the SBS, surface hardness, and microstructure. Clinical relevance. Dental clinicians can safely use HP within the recommended range to achieve effective aesthetic outcomes without compromising bracket performance and durability.