Health and environmental hazards of shape memory polymer used in orthodontic aligners – a scoping review
DOI:
https://doi.org/10.2340/biid.v13.45225Keywords:
Clear aligners, shape memory aligners, SMP, 3D-printing aligner, orthodontic aligners, digital orthodontics, biocompatibility, cytotoxicity, environmental impactAbstract
Background: Shape memory polymers (SMPs) are gaining traction in orthodontics, particularly in clear aligners, due to their stimulus-responsive behavior and potential to improve treatment outcomes. However, their use in biomedical devices raises questions about biocompatibility and environmental sustainability.
Objectives: This scoping review aims to map current evidence on the health and environmental risks of SMPs used in orthodontic aligners, identify knowledge gaps, and guide future research.
Search methods: A systematic search of PubMed, Scopus, Web of Science, Embase, ProQuest, and Cochrane databases was conducted, focusing on studies from the past decade. Search terms included SMPs, orthodontic aligners, toxicity, biodegradability, and environmental impact.
Selection criteria: Eligible studies involved original in vitro, in vivo, clinical, or environmental research related to SMPs in orthodontic applications.
Data collection and analysis: Key information from each study was extracted using a standardized Excel spreadsheet by one reviewer (SA) and validated by another (MKN). Extracted data included study design, polymer type, health and environmental risks, and conclusions. Due to heterogeneity, results were synthesized narratively.
Results: Sixteen studies met the inclusion criteria. Evidence on SMP biocompatibility is emerging but limited. Certain SMP formulations released residual monomers and degradation products with potential cytotoxic or systemic effects. Environmental concerns included low degradability, accumulation of polymer waste, and lack of recycling strategies. Notably, there was a lack of long-term clinical data and environmental life-cycle analyses.
Conclusions: While SMPs offer promise in orthodontics, their safety and environmental impacts are insufficiently studied. Future research should focus on standardized toxicological testing, long-term evaluations, and sustainable material development.
Registration and Conflicts: This scoping review was prospectively registered in PROSPERO (ID: CRD42022308725). The authors report no conflicts of interest.
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Biomaterial Investigations in Dentistry is a Diamond Open Access peer-reviewed journal, publishing research in oral biomaterials science. The publishing of articles is free for authors, thanks to the support of Acta Odontologica Scandinavica Society (AOSS), a not-for-profit society. 
