Can tooth bleaching procedures really cause morphological changes and mineral loss in dental tissues? A scoping review

Introduction: Tooth bleaching is a popular elective procedure aimed at improving tooth color and enhancing psychosocial well-being. It involves gels containing hydrogen peroxide or carbamide peroxide, which decompose to form reactive oxygen species (ROS) that penetrate mineralized tissues and degrade enamel pigments. Tooth bleaching can be performed through at-home, in-office, or combined techniques, with varying concentrations of bleaching agents. Although generally safe, factors such as agent concentration, temperature, exposure time, and tissue thickness can influence adverse effects. Free radicals generated during bleaching induce oxidative stress, which can alter the enamel's organic and inorganic matrix, potentially reducing mineral content and causing morphology alterations which weaken the enamel. The effects of tooth bleaching on enamel mineral loss and its morphology remain controversial, with ongoing research exploring its implications for dental wear, particularly in relation to aging and aesthetic improvements. Objectives: This scoping review aims to map in situ and in vivo studies evaluating morphological changes and mineral loss from tooth bleaching, the methods used for assessment, and the timing of demineralization and remineralization. It also aims to investigate the reversibility of these changes and the timeframe for remineralization, while assessing protective protocols to mitigate enamel damage. By synthesizing current evidence, it will identify research gaps and suggest directions for future studies. Methods: This study is a scoping review that will adhere to the guidelines outlined by PRISMA for Scoping Reviews (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) and will follow the guidelines presented in The Johanna Briggs Institute Reviewers' Manual (Methodology for JBI Scoping Reviews). The review will be guided by the PCC (Population, Concept, and Context) acronym and the key questions are: -are there morphological changes, mineral loss and recovery after tooth bleaching procedures, and at what timepoint do they occur? Is there any clinically viable protective clinical protocol capable of protecting the dental enamel from morphological changes and mineral loss after tooth bleaching procedures? What analytical methods are used to measure the mineral content? A thorough literature search will be carried out across several electronic databases, including PubMed/Medline, Embase, Scopus, ISI Web of Science, and gray literature sources. Keywords like "immediate mineral loss," "tooth bleaching," and "enamel structure" will guide the identification of relevant studies. Two independent reviewers will assess the articles based on the predefined inclusion criteria, and any disagreements will be resolved through discussion or consultation with a third reviewer, as needed. Inclusion criteria: Peer-reviewed studies examining mineral loss following tooth bleaching treatments; studies evaluating the effect of various bleaching agents and methods on enamel integrity. Data extraction will focus on key aspects of the selected studies, including study design, sample details, bleaching agents and protocols used, methods for evaluating mineral loss, and findings regarding enamel alterations and tooth health. The synthesis of the results will be conducted through a comprehensive analysis of the collected data, highlighting key trends, patterns, and discrepancies. A comparative approach will be applied to assess the relevance and potential implications and the synthesized data will be critically discussed, considering possible limitations and future research directions.