Highly efficient strategy for photocatalytic tooth bleaching using SiO2/MgO/Fe2O3 nanocomposite spheres

Background: Tooth discoloration is caused by variety of complex factors that are either inherent or extrinsic in nature. High concentrations (40%) of H2O2 used for in-office tooth bleaching that increase the risk of bleaching sensitivity, enamel porosity and gingival irritation. Photocatalytic degradation method is a promising way to bleaching the tooth using low concentration of H2O2. Methods: Template free Fe2O3 nanoparticles decorated SiO2/MgO nanocomposite spheres are evaluated for photocatalytic degradation of dyes and stains under UVA1 light illumination. Significant findings: SiO2/MgO/Fe2O3 photocatalyst demonstrated 90% degradation of Congo red dye with 1% H2O2 in 30 min under UVA1 light illumination. Subsequently, stained natural human teeth were satisfactorily bleached using SiO2/MgO/Fe2O3 catalyst with 1% H2O2 under UVA1 light illumination due to the generation of •OH and •O2 free radicals with the support of Photo-Fenton process. Cell viability assay indicated that human gingival fibroblasts favorably respond to the light irradiated SiO2/MgO/Fe2O3 photocatalyst associated with H2O2. The 3D surface examination of bleached enamel surfaces by confocal laser scanning microscope (CLSM, Olympus LEXTTM OLS5000) showed no significant changes. Using SiO2/MgO/Fe2O3 photocatalyst in conjunction with very low concentrations of H2O2 under UVA1 light illumination provides a safe and highly efficient strategy for dental bleaching application.