It has been shown that the intensity of adverse effects of tooth bleaching techniques on pulp-dentin complex is directly related to the amount of residual hydrogen peroxide (H2O2) capable of diffuse through enamel and dentin to reach the pulp chamber. Thus, this research project aims to develop innovative tooth bleaching products capable of minimize residual H2O2 diffusion to the pulp chamber, in order to reduce the adverse effects to pulp tissue, and also optimize bleaching effectiveness. This process will be based on a hemic peroxidase as catalyst agent of H2O2 degradation in reactive oxygen species (ROS). Two major products will be formulated: 1) Catalytic thickening agent (CT), which will be mixed to H2O2 to obtain a bleaching gel; and 2) Catalytic Primer (CP), which will be applied onto dental structure prior bleaching. At Phase 1, three hemic peroxidase and two H2O2 concentrations will be tested. The bubbling generation, sub-products deposition, pH stability and residual H2O2 will be assessed. The biological effects and bleaching effectiveness will be evaluated at Phase 2. Enamel/dentin discs (3.5 mm thickness) adapted to artificial pulp chambers (APCs), will be placed on compartments containing culture medium. The products will be applied onto enamel for 45 min. Then, the culture medium in contact with dentin (extract) will be collected and applied to human dental pulp cells (HDPCs) previously seeded on sterile acrylic plates. The cell viability and oxidative stress generation will be assessed after a 60-minute contact time with the extracts. The H2O2 diffusion through dental structure and the bleaching effectiveness will be evaluated. Based on the results, two formulations for each product (CT and CP) will be selected to determinate the application protocol according to the enamel/dentin thickness of dental substrate (Phase 3). Therefore, discs with 2.3 mm and 4.0 mm thickness, representing low incisors and upper premolars, respectively, will be obtained and the products will be applied onto enamel for 1x45, 1x30, 1x10 or 1x5 min. The same esthetic and biologic parameters will be evaluated. The data obtained will be subjected to statistical analysis.
News published in Agência FAPESP Newsletter about the scholarship: