Effect of the enzyme peroxidase on aesthetic effectiveness and cytotoxicity of low-concentrated hydrogen peroxide bleaching gels

• Grant number: 17/08506-1
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: July 01, 2017
• End date: June 30, 2018
• Field of knowledge: Health Sciences - Dentistry - Dental Materials
• Principal Investigator: Carlos Alberto de Souza Costa
• Grantee: Victoria Aparecida de Souza Bazan
• Host Institution: Faculdade de Odontologia (FOAr). Universidade Estadual Paulista (UNESP). Campus de Araraquara. Araraquara , SP, Brazil

Abstract

Reducing hydrogen peroxide (H2O2) concentration on bleaching gels has demonstrated a promising effect on the biocompatibility of this aesthetic procedure with pulp tissue. However, the bleaching effectiveness at short-time periods may be negatively affected, limiting thus the clinical application of these alternative therapies. Recent studies have demonstrated that by accelerating decomposition rate of H2O2 into free radicals increases bleaching effectiveness. Consequently, H2O2 diffusion through dental structure and cell toxicity is minimized. In this way, the aim of the present study is to evaluate the aesthetic effectiveness and cytotoxicity of 20% and 10% H2O2 bleaching gels in association with the oxidative enzyme hosehardish peroxidase (HRP). The bleaching gels will be formulated with carbopol as thickening agent, and 6 mg/mL HRP will be incorporated. The free radicals production in the presence or absence of HRP will be evaluated by specific fluorescence assays. For biological evaluation, enamel/dentin discs (3,5 mm thickness) subjected to intrinsic staining (black tea) will be adapted to artificial pulp chambers, and the bleaching gels will be applied to enamel during 45 minutes. The culture medium in contact with dentin (extract) will be collected immediately after bleaching, and applied during 60 minutes on human dental pulp cells previously seeded in culture plates (80% confluence). The cell viability (MTT) and oxidative stress (H2DCFDA) will be evaluated. Color alteration will be measured on the discs by means of a UV-vis spectrophotometer (CIE L*a*b*). In negative control group, no treatment will be performed onto the discs, and a 35% H2O2 gel will used as positive control. Numerical data obtained by laboratorial protocols will be subjected to statistical analysis. (AU)