Abstract:

Orthodontic treatment involves prolonged contact between dental materials and the oral environment, which creates conditions for continuous biological exposure throughout therapy. Orthodontic appliances remain in situ for months or years and are subjected to mechanical stress, thermal fluctuations, changes in oral acidity and microbial activity. These factors may promote corrosion, degradation and the release of metal ions, residual monomers, and other low-molecular-weight compounds with potential biological effects.
The aim of this review is to analyse the biological effects associated with materials used in orthodontic treatment, with an emphasis on allergic reactions, cytotoxicity, genotoxicity, and oxidative stress. Available experimental and clinical evidence indicates that ion release from orthodontic alloys and elution of organic components from polymeric and resin-based materials can occur under clinically relevant conditions. However, exposure levels and biological significance vary considerably depending on material composition, manufacturing features, clinical protocols, local oral conditions, and individual susceptibility.
Overall, current evidence suggests that biological responses are not determined solely by the intrinsic properties of materials but reflect a dynamic interaction between material-related factors and the oral environment. Allergic reactions—particularly to nickel-containing alloys and methacrylate-based polymers—occur mainly in sensitised individuals and may be influenced by local modifiers such as inflammation and changes in oral acidity. Cytotoxic and genotoxic findings reported in experimental models indicate plausible pathways, but clinical extrapolation remains limited due to methodological heterogeneity across studies. Further long-term studies integrating analytical measurements with biological and clinical outcomes are needed to support material- and protocol-specific risk assessment in orthodontic practice.
Keywords: Orthodontic materials; cytotoxicity; oxidative stress; allergic reactions