Development and application of a TiF4-loaded polymeric primer for in-office dental bleaching associated with violet LED irradiation

Abstract

The main objectives of the present study is to develop an innovative polymeric primer (PP) containing different concentrations of titanium tetrafluoride (TiF4) catalyst, and to assess its influence on the aesthetic efficacy, morphological changes in dental enamel and cytotoxicity frequently caused by conventional in-office tooth bleaching therapy. For this purpose, standardized enamel/dentin discs will be stained and then bleached for 45 minutes (1 session) using a bleaching gel with 35% H2O2. The gel will be applied on enamel previously coated or not with a PP containing different concentrations of TiF4 (2 mg/mL, 6 mg/mL or 10 mg/mL). No treatment or application of bleaching gel directly on enamel will be used as negative and positive controls, respectively. In PHASE 1, the best concentration of TiF4 present in PP will be determined by screening the bleaching efficacy with a UV-reflection spectrophotometer (CIE L*a*b* System). Additionally, the possible morphological alterations of the dental enamel structure will be assessed (Microhardness, Scanning Electron Microscopy and Energy Dispersive Spectrometry). In PHASE 2, the trans-enamel and trans-dentinal cytotoxicity caused by the bleaching protocols will be evaluated using enamel/dentin discs adapted to artificial pulp chambers. After completing the bleaching treatments, the extracts (culture medium + bleaching gel components diffused through the discs) will be collected and then applied on odontoblast-like MDPC-23 cells, which will be evaluated concerning their viability (MTT assay) and morphology (SEM). The quantification of total H2O2 diffused through the discs will also be determined (Leuco-crystal Violet/Peroxidase). In PHASE 3, degradation rate of H2O2 and the production of hydroxyl radicals (OH*) will be assessed. Following, the best bleaching protocols will be assessed when associated with violet LED irradiation of the gels. In PHASE 4, the best bleaching protocols already established in phases 2 and 3 will be analyzed concerning human dental pulp cells (hDPC) gene expression of the following markers: TNF; PTGS2; ILB, IL6, IL8, IL17A, IL23A; HMOX1; BGLAP, SPP1, ALPL; DSPP; and DMP1. The cells will be evaluated immediately and 7 days after concluding the bleaching protocols. The data will be subjected to specific statistical analysis. (AU)