It has been demonstrated that the chemical catalysis of hydrogen peroxide (H2O2) in bleaching gels is an interesting alternative to reduce the diffusion of this toxic free radical through the dental structure and increase the tooth bleaching efficiency. Among all the chemical activators, manganese-based oxides constitute a class of metallic oxides that are found in abundance in nature and play a fundamental role as catalytic agents. However, only a few studies have assessed the effects of bleaching gels containing such manganese-based oxides as H2O2 activators. Therefore, the aim of the present study is to evaluate the trans-enamelodentin cytotoxicity, H2O2 diffusion and the aesthetic outcome of a gel with 35% H2O2 associated with manganese dioxide (MnO2) and ferrous manganese oxide (MnFeO) as catalytic agents. For this purpose, enamel-dentin discs will be bleached with a 35% H2O2 gel (3x 15 min.) containing 2 mg/mL, 4 mg/mL or 6 mg/mL of both manganese-based oxides. The gel with no chemical activator will be used as a positive control and no treatment will be performed in the negative control group. The color changes will be measured by means of UV-Vis spectrophotometer according to the CIE L*a*b* system. To assess the trans-amelodentin cytotoxicity, the enamel-dentin discs will be adapted to artificial pulp chambers (APCs) placed in wells of 24-well plates containing 1mL of culture medium (DMEM) that will be maintained in contact with the dentin surface of the discs. After performing the bleaching procedures, an aliquot of the extracts (DMEM + bleaching gels components that diffused across the discs) will be applied for 1 h on the odontoblast-like MDPC-23 cells. Then, cell viability (MTT assay) and oxidative stress (H2DCFDA fluorescence) will be evaluated. The H2O2 capable of diffusing through the enamel-dentin discs will be quantified (leuco-crystal violet/peroxidase assay). Data will be subjected to specific statistical analysis.
News published in Agência FAPESP Newsletter about the scholarship: