Dental bleaching with hydrogen peroxide: clinical parameters analysis and in vitro effects on enamel mineral content and microhardness

Abstract

The general aim will be to analyze the clinical parameters and effects in vitro as regards enamel mineral content and microhardness when bleaching agents containing hydrogen peroxide (HP) are used. Aim 1 of the Study will be to clinically evaluate the efficiency, tooth sensitivity, presence of gingival irritation, acceptability and comfort of the bleaching technique with HP dispensed in individual or pre-loaded trays. Seventy-five participants will receive treatment with (n=25) 10% HP (Opalescence Trés White Supreme 10% Menta/ Ultradent), 9.5% HP (Pola Day/ SDI) or 10% carbamide peroxide (CP) (Opalescence PF 10% Mint/ Ultradent). Bleaching treatment will be performed for 30 minutes daily for 14 days. In different time intervals (initial, 7 and 14 days from beginning of bleaching), the tooth color will be evaluated with a spectrophotometer, and clinical parameters of sensitivity, degree of acceptability of the bleaching technique and degree of comfort of the bleaching tray used will be evaluated by means of visual analog scales (VAS). Aim 2 of the study will be to evaluate the calcium and phosphorous content of human tooth enamel before, during and after treatment with bleaching agent for home and in office treatment, containing HP in high and low concentrations. Forty-eight completely impacted third molars will be used, which will be distributed into the levels of factors under study (n=8): 'HP with high concentration' - Whiteness HP Maxx/ FGM (35% HP); Whiteness HP Blue/ FGM (35% HP + 2% calcium gluconate); Pola Office +/ SDI (37.5% HP+ 5% potassium nitrate); Opalescence Boost/ Ultradent (38% HP + 1.1% fluoride and 3% potassium nitrate) - and 'HP with low concentration' - Pola Day/ SDI (9.5% PH); White Class 10%/ FGM (10% PH + potassium nitrate + calcium + fluoride). The same tooth will be evaluated at different "time intervals" during and after bleaching treatment, with microbiopsies being performed of the enamel for quantification of calcium and phosphorous by means of the Total Reflection x-Ray Fluorescence Technique (TXRF). Aim 3 of the study will be to evaluate human tooth enamel microhardness before, during and after treatment with bleaching agent for home and in office treatment, containing PH in high and low concentrations. For this purpose, the same bleaching agents and evaluation time intervals as those described in Project 2 will be evaluated. The Test of Correlation between the data obtained in Projects 2 and 3 will be applied. Appropriate statistical tests will be applied according to the type of variable under study for each of the projects presented. (AU)