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 LEXT^TM 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.