Bleaching efficacy, transenamel and transdentinal cytotoxicity and degradation kinetics of bleaching gels containing manganese oxide

Author(s)

Rafael Antonio de Oliveira Ribeiro

• Document type: Master's Dissertation
• Press: Araraquara. 2020-08-04.
• Institution: Universidade Estadual Paulista (Unesp). Faculdade de Odontologia. Araraquara
• Defense date: 2020-05-06
• Advisor: Carlos Alberto de Souza Costa

Abstract

Objective: Assess the aesthetic outcome, transenamel and transdentin toxicity as well as degradation kinetics of bleaching gels with 10% and 35% H2O2 chemically activated with manganese oxide (MnO). Methods: Enamel-dentin discs were stained and bleached with gels associated with an experimental thickener containing or not MnO. As positive and negative controls, gel with 35% H2O2 was applied on enamel for 45 minutes or no treatment was performed, respectively. To determine the best concentration of MnO (2 mg/mL, 6 mg/mL and 10 mg/mL) concerning the aesthetic outcome, the discs were stained with black tea and then bleached with the experimental gels (UV-reflecting spectrophotometer, CIE L * a *B* system). For cell viability (MTT assay) and oxidative stress analysis, the bleaching protocols were performed on discs adapted to artificial pulp chambers and the extracts (culture medium in contact with dentin surface + components of the bleaching gels that diffused across the discs) were collected and applied for 1 h on odontoblast-like MDPC-23 cells. The quantification of H2O2 diffused through the discs was also determined (leuco-crystal violet/peroxidase assay). The numerical data were submitted to specific statistical analysis (ANOVA; Tukey). Results: Increased aesthetic outcome was achieved with the addition of MnO to both concentrations of H2O2 in the bleaching gels. However, this effect was more significant for the concentration of 10 mg/mL of MnO. Disregarding the concentration of H2O2 in the bleaching gels, the addition of MnO in the composition of such products reduced significantly the transenamel and transdentinal diffusion of residual H2O2, the oxidative stress and consequently the cytotoxicity of the procedures to the pulp cells. These positive data were more evident with the addition of 10mg/mL of MnO to the bleaching gels, what also increased significantly the production of free radicals and hydroxyl radicals (degradation kinetics). Conclusion: It was possible to conclude that the production of free radicals and radical hydroxyl, enhances the aesthetic outcome, as well as reduces the oxidative stress and toxicity to pulp cells. (AU)

• FAPESP's process: 18/14457-6 - Transenamel and transdentinal cytotoxicity, bleaching efficacy and degradation kinetics of bleaching gels containing metallic oxides
• Grantee: Rafael Antonio de Oliveira Ribeiro
• Support Opportunities: Scholarships in Brazil - Master