The Effect of Hydrogen Peroxide With Different Concentration on the Color and Surface Microhardness of the Resin...

This study aimed to evaluate the whitening effect, shear bond strength (SBS), microhardness, and microstructure of discolored resin brackets following whitening treatment with various concentrations of hydrogen peroxide (HP).

Resin brackets were bonded to the enamel surface and discolored with a curry solution. Control (distilled water; DW) 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 DW for a week by repeating this whitening process three times. The whitening efficacy was evaluated according to the 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 ANOVA analysis and Tukey's post-hoc test (p = 0.05).

All the experimental groups demonstrated a significant whitening effect on the discolored resin brackets compared to the control group (p < 0.05). Especially, 35% HP showed faster color changes than the other groups (p < 0.05). The microhardness of the resin bracket was significantly lower in 35% HP compared to the control group (p < 0.05). FE-SEM analysis revealed no significant difference between the experimental and control groups.

HP application at concentrations of > 8.7% and < 17.5% is effective in whitening discolored resin brackets while not deteriorating the SBS, surface hardness, and microstructure. Dental clinicians can safely use HP within the recommended range to achieve effective esthetic outcomes without compromising bracket performance and durability.