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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.
AIM: This study investigated the acute biological effects of micro- and nanoplastics (MPs/NPs) released from 3D-printed orthodontic aligners, focusing on their potential to elicit inflammatory and oxidative responses. Given the dynamic intraoral environment, the use of a biologically relevant invertebrate model (Hirudo verbana) enabled histological and molecular assessment of short-term exposure to plastic-derived particles. MATERIALS AND METHODS: MPs/NPs were generated from 3D-printed aligner samples via mechanical stress and ultrasonication. Medicinal leeches were exposed to the resulting plastic dispersion for 24, 72 h, and 1 week (triplicate experiments). Morphological alterations were assessed by light and electron microscopy. CD31 and HmAIF-1 immunostaining and acid phosphatase assays evaluated immunological responses. Oxidative stress was quantified by quantitative PCR (qPCR) analysis of SOD and GST gene expression. One-way ANOVA with Dunnett's post hoc test comparing MP/NP-treated vs controls (α = 0.05). RESULTS: Exposure to MPs/NPs triggered rapid angiogenesis, confirmed by increased CD31 expression and vascular remodelling over time (24 h, P < .01; 72 h, P < .001; 1 week, P < .01). Macrophage-like cell activation was significantly evidenced by elevated HmAIF-1 levels (24 h, P < .001; 72 h, P < .01; 1-week, P < .001) and acid phosphatase activity (24 h, P < .001; 72 h, P < .01; 1-week, P < .001). Oxidative-stress markers (SOD and GST) were significantly upregulated at 24 h (P < .001) and, for glutathione transferase only, slightly increased at 72 h (P < .05), indicating an acute cellular stress response that decreased at later time points. CONCLUSIONS: Even brief exposure to MPs/NPs released from 3D-printed aligners can disrupt tissue homeostasis, activating inflammatory and oxidative pathways. These findings raise concerns about the biocompatibility of photopolymer resins and underscore the need for more dynamic, biologically relevant testing models to evaluate the safety of orthodontic materials under clinically realistic conditions.
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Experimental assessment of damage and microplastic release during cyclic loading of clear aligners
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Researchers tested three popular brands of clear orthodontic aligners under simulated chewing conditions and found that all released microplastic particles during use. Since patients wear aligners for extended periods each day, this represents a direct and ongoing source of microplastic ingestion, raising questions about the cumulative exposure from dental devices that are growing in popularity.
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.
Orthodontic derived microplastics impact macrophage differentiation and homeostasis
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Researchers found that commonly used orthodontic materials release micro- and nanoplastic particles that are readily taken up by immune cells called macrophages. The particles triggered a shift toward pro-inflammatory immune responses, with direct-printed polymer materials releasing higher levels of immunostimulatory particles, raising concerns about both local oral health effects and potential systemic immune impacts from dental devices.
Orthodontic Clear Aligners as a Potential Source of Microplastic Exposure: Implications for Human Health and Environmental Sustainability
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If you're using clear plastic aligners to straighten your teeth (like Invisalign), this review of existing research suggests that everyday wear and tear from chewing and saliva may cause them to shed tiny plastic particles into your mouth. Scientists don't yet know how much this affects your health, but it adds to growing concerns about microplastics — tiny plastic fragments already found throughout the human body — while also raising questions about the environmental waste from millions of discarded aligners. More research is needed before we know if this is something to actually worry about.
Macrophage extracellular trap formation and oxidative stress in periodontal cells associated with clear aligner-derived microplastics
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Clear aligners (the clear plastic teeth-straighteners) can shed tiny microplastic particles, and lab tests show these particles trigger immune cells to release inflammatory "traps" while causing oxidative stress that damages bone-forming cells near the gums. This early-stage cell study suggests long-term aligner wear might contribute to gum and bone irritation, though more research is needed to confirm this happens in real mouths, not just lab dishes.
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