Digital Clear Aligner Systems as Multifunctional Platforms for Tooth Bleaching: A Systematic Review of Material Performance and Mechanical Implications in Esthetic Dentistry

Background: Clear aligners fabricated via computer-aided design and manufacturing are increasingly used in orthodontics and may also serve as carriers for peroxide-based bleaching agents. However, exposure to bleaching agents may affect the physical and surface properties of aligner polymers, which could influence their clinical performance. Objective: This systematic review aims to evaluate the available evidence on the use of clear aligners as carriers for tooth bleaching agents, with a focus on bleaching efficacy and reported effects on aligner materials based on the identified literature. Methods: A systematic search was conducted in PubMed, Web of Science, Scopus, Scielo, and Embase for studies published up to January 2026. Eligible clinical and in vitro studies investigated bleaching procedures using clear aligners or conventional trays and reported color change outcomes and/or changes in material properties such as hardness, surface integrity, or mechanical performance. Risk of bias was assessed using the Cochrane Risk of Bias tools and standardized criteria for in vitro and clinical studies. Results: Six studies (three clinical and three in vitro) met the inclusion criteria. Clinical evidence indicated that bleaching delivered through clear aligners achieved similar whitening outcomes to conventional tray-based systems. In vitro studies reported changes in surface hardness and mechanical properties of polymer-based aligner materials after peroxide exposure; however, no major structural degradation was observed. Clinical studies were generally at high risk of bias, while in vitro studies showed low to moderate risk. Conclusions: Within the limitations of this systematic review, clear aligners may represent a potential carrier for tooth bleaching agents with outcomes comparable to conventional trays. However, the available evidence is limited and heterogeneous. Well-designed randomized controlled trials are needed to confirm clinical effectiveness and long-term material safety.