Development of tooth bleaching products based on advanced oxidative process principles: analysis of esthetic and biologic effects

Abstract

This research project has the challenging purpose of developing innovative tooth bleaching products capable to associate both esthetic and biologic parameters. The optimization of hydroxyl radicals (HO*) generation from hydrogen peroxide (H2O2) at low concentrations will be the principle of these products in order to increase the reactivity with tooth structure. Consequently, the diffusion of residual H2O2 to the pulp chamber should be reduced. The HO* generation from H2O2 will be based on Fenton, Photo-Fenton and Modified-Fenton reactions, widely used on Advanced Oxidative Process, by formulation of catalytic phases containing iron, manganese or hemic peroxidase. Two products will be formulated: 1) Catalytic thickening agent (CT), which will be mixed to the H2O2 phase in order to generate a bleaching gel; and 2) Catalytic Primer (CP), which will be applied on dental structure prior bleaching. In Phase 1, products (CT and CP) will be formulated for each catalytic agent. The variables pH, catalytic agent/ H2O2 rate, and association with photocatalysis will be tested, and HO* generation/residual H2O2 will be evaluated. Then, the biologic and esthetic effects of these products will be analyzed (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 the enamel for 45 min. Then, the culture medium in contact with dentin (extract) will be collected and applied on human dental pulp cells (HDPCs) previously seeded on acrylic plates. The cell viability and oxidative stress generation will be assessed after a 60-minute contact time with the extracts. The H2O2/HO* diffusion through dental structure and the bleaching effectiveness will be evaluated. According to the results, one formulation for each product (CT and CP) will be selected to Phase 3, and the application protocol will be determined according to the enamel/dentin thickness of dental substrata. In this way, discs with different thickness (2.0-2.5 mm and 3.5-4.0 mm) 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. Finally (Phase 4), more detailed analysis of products/protocols biologic effects will be performed on HDPC 3D culture in vitro, and also on human pulp tissue in situ. The pathways related to oxidative stress, inflammation and tissue regeneration will be assessed. Data will be subjected to statistical analysis. (AU)