The impact of at-home bleaching time with 10 hydrogen peroxide on whiteness potential, enamel microhardness and mitocondrial activity of human gingival fibroblasts

• Grant number: 25/11160-6
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: November 01, 2025
• End date: October 31, 2026
• Field of knowledge: Health Sciences - Dentistry - Dental Clinics
• Principal Investigator: Matheus Kury Rodrigues
• Grantee: Ana Júlia da Silveira Pedreira Oporto
• Host Institution: Vice-Reitoria de Pesquisa e Pós-Graduação. Universidade Paulista (UNIP). São Paulo , SP, Brazil

Abstract

Introduction: The growing demand for aesthetic dental treatments has driven the use of at-home tooth bleaching techniques, particularly those using 10% hydrogen peroxide (HP). Despite reported efficacy, there is ongoing debate regarding the impact of application time of these agents on tooth structure and their biocompatibility with gingival tissues. Objective: This project aims to evaluate the influence of application time of commercial 10% HP-based bleaching gels on bleaching effectiveness, enamel microhardness of bovine teeth, and mitochondrial activity in human gingival fibroblasts. Methods: Three commercial 10% HP gels (White Class - FGM, Opalescence GO - Ultradent, and Potenza Bianco H2O2 - Potenza Bianco) will be characterized in terms of HP concentration and pH at 15, 30, and 60 minutes of application using electronic titration with potassium permanganate and a pH meter, respectively. Then, 90 bovine tooth blocks will be randomly distributed into 9 groups (n = 10/group) according to the product instructions and the three evaluation times (15, 30, and 60 min) during a two-week daily application protocol. Color change (¿E00) and whiteness index (¿WID) will be measured using a benchtop spectrophotometer. Enamel surface microhardness will be assessed using a Knoop indenter. Human gingival fibroblasts will be exposed to different HP dilutions for the same time periods and evaluated using the MTT assay to measure mitochondrial activity. Data will be explored and, upon confirmation of normality assumptions, analyzed using two-way ANOVA (¿ = 5%).