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Biocompatibility of Orthodontic Aligner Materials in the Digital Workflow: A Quantitative In Vitro Comparison of Thermoformed, Directly Printed, and Polyamide-12 Systems
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Scientists tested how different clear aligner materials—including newer 3D-printed types—affect human cells when tiny plastic particles wear off during use. Traditional thermoformed aligners and a polyamide-based system held up better in lab tests, while some 3D-printed materials showed more cell damage at higher doses and longer exposure times. This suggests that as 3D-printed aligners become more popular, manufacturers need better testing and quality controls to ensure they're safe for long-term wear in your mouth.
INTRODUCTION/OBJECTIVES: Directly 3D-printed aligners (DPAs) have recently emerged as a promising development in orthodontics, offering greater design flexibility and in-office manufacturing. However, their biological safety remains incompletely characterised, particularly regarding the release of micro- and nanoplastics (MNPs) during clinical use. This study evaluated the in vitro cytocompatibility of eight orthodontic aligner materials, including thermoformed systems, directly 3D-printed resins, and a polyamide-12 (PA-12) device, using MTT cell-viability assays on human dental pulp stem cells (hDPSCs). METHODS: Standardised specimens were prepared according to manufacturer-recommended protocols, while MNP suspensions were generated by controlled abrasion and sonication. Cells were exposed to material eluates at concentrations of 500, 1000, and 5000 ng/100 µL for 24 to 96 hours. RESULTS: Cell viability and morphological analyses revealed marked material-, dose-, and time-dependent differences. Thermoformed materials and the polyamide-12 system generally exhibited more stable profiles, with viability frequently above 70% and preserved cell morphology. A subset of materials showed non-linear responses suggestive of a hormetic-like effect. By contrast, several directly 3D-printed resins showed greater reductions in viability, approaching moderate cytotoxicity at higher concentrations and longer exposure. CONCLUSIONS: Within the limitations of this in vitro study, thermoformed materials and polyamide-12 showed more consistent cytocompatibility than some directly printed materials. CLINICAL SIGNIFICANCE: These findings highlight the need for systematic biocompatibility evaluation of orthodontic aligner materials and indicate that adherence to standardised post-curing protocols and rigorous material qualification workflows is essential to minimise potential biological risks during clear aligner therapy.
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Scientists reviewed new 3D-printed teeth straighteners that could replace traditional clear aligners, potentially offering better fit and even delivering antibacterial treatments or fluoride directly to teeth. However, early research shows these newer aligners may release harmful chemicals and create microplastics in the mouth. More long-term safety studies are needed before these 3D-printed aligners can be considered safe alternatives to current teeth straightening methods.
Effects of microplastic release from 3D-printed orthodontic aligners: a histological and immunological bioassay approach.
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3D-printed clear aligners (a popular alternative to traditional braces) can shed tiny plastic particles, and this study found that these particles triggered inflammation and stress responses when tested on living tissue. While the research used leeches rather than humans, it's an early warning sign that the materials used in some orthodontic devices may not be as harmless as assumed, and more real-world testing is needed before we know what this means for people's mouths.
Microscopic Acid‐Induced Degradation and Elemental Release From Thermoformed and 3D ‐Printed Orthodontic Aligners in a Simulated Gastric Environment
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Researchers evaluated acid-induced degradation and elemental release from thermoformed and 3D-printed orthodontic aligner materials under simulated gastric conditions, finding that both types released microplastic and nanoplastic particles along with chemical additives under acidic exposure, raising concerns about ingestion risks during orthodontic treatment.
Release of Microplastics and Chemical Compounds from Clear Orthodontic Aligners: A Narrative Review of the Current Evidence
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This review summarizes existing research on clear plastic orthodontic aligners, worn in the mouth, and whether they release chemicals and tiny plastic particles as they wear down. Lab studies found that aligner surfaces can develop roughness and tiny cracks, sometimes releasing chemicals and microplastics, but most evidence comes from lab models rather than real-world use in people.
Biocompatibility and Safety of Orthodontic Clear Aligners and Thermoplastic Retainers: A Systematic In Vitro Review (2015–2025)
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This systematic review examined whether orthodontic clear aligners and retainers release harmful chemicals or microplastics in the mouth. While most products met safety standards, some materials did release detectable levels of bisphenol A and other chemicals, especially during initial wear and after aging, raising questions about long-term oral exposure.
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