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Cytotoxicity and Endocrine Disruption in Materials Used for Removable Orthodontic Retainers: A Comprehensive Review.
Katarzyna Chojnacka1, Marcin Mikulewicz2
1Department of Advanced Material Technologies, Faculty of Chemistry, Wroclaw University of Science and Technology, 50-372 Wroclaw, Poland.
Dentistry Journal
|June 25, 2025
Summary
Orthodontic retainer materials are generally safe, with minimal cytotoxicity and no significant endocrine disruption reported in clinical studies. However, long-term endocrine effects require further investigation, and environmental concerns exist regarding microplastic release.
Area of Science:
- Biomaterials Science
- Orthodontics
- Toxicology
Background:
- Removable orthodontic retainers utilize various materials, including polymethyl methacrylate (PMMA), thermoplastics, 3D-printed resins, polyetheretherketone (PEEK), and fiber-reinforced composites.
- Assessing the biocompatibility and potential endocrine-disrupting effects of these materials is crucial for patient safety and long-term oral health.
Purpose of the Study:
- To evaluate the cytotoxicity and endocrine-disrupting potential of materials commonly used in removable orthodontic retainers.
- To review in vitro and in vivo data on the biological responses to these retainer materials.
Main Methods:
- A comprehensive literature search (2015-2025) was conducted across electronic databases.
- Included studies focused on in vitro cytotoxicity, estrogenicity, in vivo tissue responses, and clinical biomarkers.
- Analysis covered PMMA, thermoplastics, 3D-printed resins, PEEK, and fiber-reinforced composites.
Main Results:
- Thirty-eight in vitro and ten clinical studies met the inclusion criteria.
- Photopolymer resins showed the highest cytotoxicity; thermoplastics and PMMA exhibited mild effects, decreasing after water storage.
- While bisphenol-type compounds were released, systemic exposure remained below regulatory limits; no significant clinical endocrine effects were observed.
Conclusions:
- Most orthodontic retainer materials demonstrate good biocompatibility.
- Limited data exist on long-term endocrine effects, necessitating standardized biocompatibility assessment protocols for comparative analysis.
- Environmental concerns arise from microplastic release by single-use thermoplastics and their end-of-life management.
