The in-office bleaching technique performed with high concentrations of hydrogen peroxide (HP) gels may cause damage to the pulp tissue. Therefore, the administration of antioxidant agents before tooth bleaching has been proposed in order to prevent the deleterious effects of this clinical aesthetic procedure. The aim of this study is to evaluate the protective effect of vitamin E on odontoblast-like cells (MDPC-23) against the trans-enamel and trans-dentinal toxicity of a 35%-HP bleaching gel. First of all, a dose-response and a time-response curves of vitamin E (alfa-tocoferol) and its synthetic analogue (TROLOX) will be obtained in face of a direct aggression of HP using the MTT assay. In this way, the ideal concentration and contact time of the vitamins with the cells will be determined for a protective effect. Then, enamel/dentin discs will be adapted to artificial pulp chambers (APCs). The MDPC-23 cells will be seeded on the dentin surface of the discs and pre-treated with the antioxidant agent previously selected (alfa-tocoferol or Trolox) using the pre-determinate concentration and contact time. The 35%-HP bleaching gel will be applied for 45 minutes (3 applications of 15 minutes) on the enamel surface of the discs. After the bleaching procedure, the APCs with the discs and cells will be maintained in incubator with 5% CO2 at 37o C for 12 hours. The cell metabolism and cell morphology will be evaluated by MTT Assay and SEM, respectively. The data will be subjected to specific statistical analysis.
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