Vol. 11, Issue 4, Part A (2025)

Clear aligners have revolutionized orthodontic therapy by providing a more aesthetic and comfortable alternative to fixed appliances. However, increasing concerns have emerged regarding their biocompatibility and potential health risks associated with chemical leaching and microplastic release. This review explores the composition, degradation behavior, and biological implications of commonly used thermoplastic materials such as polyethylene terephthalate glycol (PETG), polyurethane, and polycarbonate. Evidence from in vitro and systematic reviews indicates that while most aligners comply with international safety standards, variable levels of bisphenol A (BPA), urethane dimethacrylate (UDMA), and other additives can leach into the oral environment, particularly during initial wear periods. The release of these compounds and microplastic particles poses possible cytotoxic, estrogenic, and systemic risks, including endocrine disruption and microbiome alterations. Despite advancements in manufacturing, data from human studies remain limited, and the long-term biological impact of chronic exposure remains unclear. Future research should prioritize standardized testing protocols, robust clinical trials, and the development of safer, sustainable biomaterials for aligner fabrication.