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This systematic review aims to further current knowledge on the effects of microplastics from orthodontic clear aligners, identifying potential implications for human health and providing a basis for further research and development of alternative materials. A literature search to find all peer-reviewed citations relevant to the review topic was conducted in the following databases: PubMed, Scopus, Web of Science, and Cochrane Library on 31 December 2024. A manual search of grey literature was also performed. There were 62 citations retrieved by the search query, and 11 were selected for inclusion in the review. Four selected studies were in vitro, while seven were in vitro following intraoral material aging studies. Ten studies evaluated the surface morphology of the material after aging, among the mechanical characteristics assessed, while only one article evaluated the chemical characteristics and size of the microplastic particles released from the aligners after simulated in vitro use. Discussion: From the evaluation of the studies included in this review, it is possible to state that there is a gradual increase over time in the surface roughness of the material, and modifications occurred in the morphology and surface topography of the aligners. Furthermore, it emerged that dispersion of microplastics occurs during the use of different types of aligners, with microplastic particle sizes ranging from 5 to 20 μm The findings suggest that clear aligners may cause microplastic dispersion in saliva during therapy, and this could cause a problem for the general health of patients, due to the absorption or ingestion of these released molecules. Further research is needed to fully understand the extent of microplastics released from aligners and to find alternative materials that can reduce this occurrence.
Stefano et al. (Fri,) studied this question.