Development of experimental thickeners for hydrogen peroxide-free innovative bleaching gels application: in vitro and clinical studies

• Grant number: 25/04556-0
• Support Opportunities: Regular Research Grants
• Start date: November 01, 2025
• End date: October 31, 2028
• Field of knowledge: Health Sciences - Dentistry - Dental Materials
• Principal Investigator: Carlos Alberto de Souza Costa
• Grantee: Carlos Alberto de Souza Costa
• Host Institution: Faculdade de Odontologia (FOAr). Universidade Estadual Paulista (UNESP). Campus de Araraquara. Araraquara , SP, Brazil
• Associated researchers: Josimeri Hebling Costa

Abstract

The main objective of this study is to develop in-office bleaching gels based on peroxymonosulfate (PMS) and peroxydisulfate (PDS) with different thickeners (Carbopol 940, Aristoflex, Chitosan), as well as to evaluate their esthetic efficacy, effects on the structure of dental enamel and trans-amelodentinal cytotoxicity. Initially, experimental groups will be established, where combinations of different concentrations of PMS or PDS, containing or not manganese dioxide (MnO2), will be evaluated. The concentrations will be determined by potentiometric titration of each gel, and the degradation of chromophores will be analyzed to found the best concentrations of both oxidizing agents. The most promising gel formulations containing PMS and PDS with or without MnO2 will be selected for the following laboratory analyses. For this purpose, enamel/dentin discs will be standardized and then subjected to the bleaching procedure (gel with 35% H2O2) for a period of 45 minutes (1 session). In positive and negative control groups, no treatment will be performed on enamel or the base formulation of the bleaching gels, without the active compound, will be applied on enamel, respectively. The efficacy of the bleaching will be assessed using a UV-reflection spectrophotometer (CIE Lab* System). Subsequently, Scanning Electron Microscopy (SEM) and Energy Dispersive Spectrometry (EDS) will be employed to evaluate the microhardness and possible morphological changes caused by the bleaching treatments on dental enamel. The trans-amelodentinal cytotoxicity of the bleaching therapies will be estimated by using a protocol in which standardized enamel/dentin discs will be adapted to artificial pulp chambers. After concluding the bleaching therapies, the extracts (culture medium + components of gels diffused through the discs) will be collected and then applied to odontoblast-like MDPC-23 cells, which will be evaluated concerning their viability (MTT), oxidative stress (carboxy-H2DCFDA probe) and morphology (SEM). The amount of H2O2 diffused across the discs will also be determined (leuco-crystal violet/peroxidase). In addition, the cells will be evaluated (immediately and after 7 days) for gene expression of the following gene markers: Tnf; Ptgs2; Ilb, Il6, Il17d, Il23a; Hmox1; Bglap, Spp1, Alpl; Dspp and Dmp1. The genotoxic effects of the bleaching therapies will also be assessed (analysis of micronucleus formation). After concluding the in vitro protocols, the best bleaching strategies obtained will be clinically evaluated for chromatic alteration of the teeth, as well as the degrees of sensitivity and satisfaction of patients undergoing innovative aesthetic therapies. The numerical data obtained will be subjected to specific statistical analysis. (AU)