Tooth bleaching is commonly mentioned as a simple and safe clinical procedure. However, it can offer risks if not well indicated or used inadequately. For non-vital teeth, the most undesirable risk is related to the diffusion of the bleaching agent to unprotected cervical area, stimulating osteoclasts and resulting in dental resorption in this region. Thus, the interaction between dentin nature, the substrate that is actually bleached, and the bleaching agent, is determinant to the success of the procedure. Dentin permeability is at the same time necessary as bleaching agent via of access and offers biological risks. This study purposes to evaluate different conditions of bleaching related to dentin permeability. The hypothesis is that bleaching agent associated or not to previous acid etching and/or to energy source can increase dentin permeability. Ten 1mm-thick dentin disks per group will be obtained from sound human third molars, totalizing 50. These disks will be flatted with no enamel or pulp corn evidences, checked using an optical microscopy. They will be individually placed in filtration chambers, allowing a standard dentin area exposition of 0.282mm2. In a first step, all disks will be treated with 35% phosphoric acid liquid to select dentin with similar baseline permeability. Subsequently, all selected sample will be randomized to 5 different groups: C- inert gel (negative control); PH- Whiteness HP Maxx-WM/ FGM- 35% hydrogen peroxide; PH-AF- WM- application of 35% phosphoric acid etching previous to treament with WM; PH-FE- WM associated to energy; PH-AF-FE- application of 35% phosphoric acid etching previous to treament with WM and associated to energy. Bleaching agente will be applied for 10 minutes, and disturbed after each 5 minutes. In the groups with light source association, it will be made after 5 minutes for 30s. Following, permeability will be assessed by capilarity using FLODEC. Data will be colected and analyzed according to normal distribution. If data satisfty this condition, it will be analyzed by ANOVA, considering treatment of substrate as a criteria.
News published in Agência FAPESP Newsletter about the scholarship: