Tooth whitening procedures are increasing; however, side effects can occur, such as damage to pulp cells, by the whitening products. This study aims to assess the cellular effects promoted by a whitening product, namely, the oxidative stress fostered by the active agent hydrogen peroxide, with and without photoactivation. Additionally, if cellular recovery occurred, we intended to determine the time point where cells recover from the tooth whitening induced damage. Human fibroblasts were exposed to hydrogen peroxide, Zoom®, Zoom® + irradiation, and irradiation alone. The following analysis was performed: metabolic activity evaluation by the MTT assay; cell viability, mitochondrial membrane potential, peroxides production, superoxide radical production, and reduced glutathione expression by flow cytometry. We determined the IC50 value for all groups, and a dose-dependent cytotoxic effect was verified. At the times analyzed, hydrogen peroxide groups showed no metabolic activity recovery while a cell recovery was observed after 24 h (Zoom®) and 48 h (Zoom® + irradiation). Cell death was seen in hydrogen peroxide and Zoom® + irradiation groups, mainly by apoptosis, and the irradiation had a cytotoxic effect per se. This in vitro study supports that whitening products with moderate hydrogen peroxide (HP) concentration have a temporary effect on cells, allowing a cellular recovery.
Keywords: cytotoxicity; fibroblasts; hydrogen peroxide; oxidative stress; tooth whitening.