Influence of thickener kind and hydrogen peroxide gel viscosity on the properties of the hydrogen peroxide gel

Abstract

Objective: The aim of this study will be to understand how the choice of a thickening agent and the viscosity of a 35% hydrogen peroxide gel can influence the chemical reactions occurring inside the gel layer; the way it interact with tooth structure and produce its primary and secondary effects over mineralized structure. More specifically the effect of the variables on pH, peroxide decomposition, formation of free radicals and capture of calcium and phosphorus by the bleaching gel.Materials and Methods: 270 bovine incisors will be selected and enamel/dentin discs obtained from labial surface, with 6mm of diameter and 2mm of thickness (1mm of enamel and 1mm of dentin). Experimental bleaching gels will be prepared using five different thickening agents (PAP - polyacrylic acid polymer; EC - acrylic copolymer emulsion - Salcare, PAS - sulfonic acid polymer - Aristoflex, SAM - Magnesium aluminum silicate - Bentonita, SP - Fumed silica - Aerosil), which will be added in enough quantity to produce gels with low (L - 30.000 cP), medium (M - 100.000 cP) e high (H - 250.000 cP) viscosities. The samples will be divided into the following experimental groups/subgroups (n=15): PAP/L, PAP/M, PAP/H; EC/L, EC/M, EC/H; PAS/L, PAS/M, PAS/H; SAM/L, SAM/M, SAM/H; SP/L, SP/M, SP/H. In addition, three control groups will be prepared: NTPC (Non Thickener Positive Control) - a hydrogen peroxide solution will used; CPC (Commercial Positive Control) - A commercially available bleaching gel will be used (Whiteness HP, FGM). NC (Negative Control) - the treatment will be performed with purified water. The bleaching gels will be applied for 45 minutes over the samples. The change on peroxide content in the bleaching gel will be evaluated using titration with potassium permanganate and a potentiometric titrator (HI902C1-02, Hanna). The amount of free radicals in the bleaching gel will be measured using the Aminophenyl Fluorescein indicator and a multimode microplate reader (SYNERGY HTX, Biotek) in the fluorescence mode. The concentration of calcium and phosphorus in the bleaching gel will be analyzed using a multimode reader (SYNERGY HTX, Biotek) in the absorbance mode. The pH changes of the bleaching gel will be measured using a micro electrode (HI1083B, Hanna). The data will be statistically analyzed with a significance level of 5%. (AU)