Incorporation of TiO2 in low concentration bleaching agent for in-office use associated with violet light: physical-chemical properties of the bleaching gel, influence on tooth color, cell cytotoxicity and effect on the dentin matrix

Abstract

The present study aims to evaluate the physicochemical properties of dental bleaching agents incorporated with titanium dioxide (TiO2) nanotubes, associated or not with the application of violet light and the effects on the color change of the dental structure at different times, pulp temperature, biocompatibility with cell culture and the characteristics of the dentin collagen matrix. Bleaching agents containing hydrogen peroxide (PH) at 35% (Whiteness HP, FGM) and 6% (White Class, FGM) will be evaluated, incorporated or not with 1% TiO2, associated or not with the application of violet LED light. To evaluate the physicochemical properties of the bleaching gels, the pH value, mass analysis, decomposition of hydrogen peroxide, average particle size (P), polydispersity (PO) and zeta potential (PZ) will be verified. For color analysis (Vita Classical scale, CIELab and CIEDE 2000), 60 bovine incisors will be prepared divided into six groups (n = 10). The bleaching agents will be applied with or without application of violet LED light (Bright Max Whitening, MMOptics) in three sessions of 30 minutes each, with an interval of 7 days between sessions. Measurements will be performed at different times (baseline, 24 hours after, 8th day, 15th day and 1 week and 1 month after the end of treatment). For the evaluation of the pulp temperature (using a thermocouple inside the pulp chamber), 60 bovine incisors with access through the palatal face and with a 2.5mm thick buccal wall will be used for the same groups. Temperature measurements will be made before, during and after the bleaching treatment. For the evaluation of cytotoxicity, cell culture of fibroblast and pulp odontoblate will be used. The cells will be seeded in 96-well plates (1 x 103 cells / well) and placed in contact with culture medium conditioned by the bleaching gels (group PH 35%, group PH 6%, group PH 6% with the addition of nanotubes) together with the application or not of the violet LED light for 30 minutes. Cell viability will be analyzed using the MTT reduction test and cell proliferation will be done using the Trypan blue vital exclusion method, immediately and 24 hours after treatment. The dentin collagen matrix will be evaluated by means of a three-point flexural strength test to determine the modulus of elasticity throughout the whitening treatment, using collagen matrices (demineralized beams). Quantification of metalloproteinases and analysis of the release of hydroxyproline will be performed to assess the influence of treatments on collagen degradation. For all variables studied, the data will be tabulated in an electronic spreadsheet, using parametric or non-parametric tests. Significance level of 5% will be adopted. (AU)