Do Orthodontic Aligners Release Microplastics?

In March 2026, researchers at the University of Buffalo published findings that should concern anyone wearing a clear aligner right now. Their study confirmed that orthodontic aligners — the kind worn by roughly 14 million Americans for 20 to 22 hours per day — release micro- and nanoplastic particles (MNPs) during normal use. More troublingly, the study documented that macrophages — the immune cells that patrol your body for foreign threats — actively ingest these plastic particles. Once inside, the particles persist. They do not break down. And the immune cells loaded with plastic behave differently from healthy ones.

This is not a fringe finding. It is a peer-reviewed study from a research university, and it adds to a growing body of evidence showing that items we put directly in or on our bodies — tea bags, coffee makers, food containers, baby bottles — release plastics into the human body in ways we are only beginning to understand. Clear aligners are the latest item on that list, and they occupy a uniquely intimate position: a custom-fit plastic device worn inside your mouth for the better part of every day, in direct contact with your saliva, for months or years at a time.

What the University of Buffalo Study Found

The March 2026 study focused on what happens at the cellular level when aligners are worn. The key findings were straightforward and concerning in equal measure.

Aligners release MNPs during normal use. Simply wearing a clear aligner as directed — 20 to 22 hours per day — is enough to cause the release of micro- and nanoplastic particles. This is not a matter of abnormal wear or misuse. It is the product functioning as designed, in an environment (the mouth) that accelerates plastic degradation.

Macrophages ingest the particles. Macrophages are the front-line immune cells responsible for engulfing and neutralizing foreign material in the body. When micro- and nanoplastics are present, macrophages do exactly what they are designed to do: they eat them. The problem is that plastic particles are not like bacteria or viruses. Macrophages can destroy pathogens. They cannot destroy polyurethane.

The particles persist inside the cells. Once ingested, MNPs remain inside the macrophage. There is no enzymatic pathway to break them down. The macrophage is effectively stuck carrying a load of plastic debris indefinitely, which impairs its ability to perform its normal functions.

The downstream consequences are significant. When macrophages are loaded with plastic particles, the study found evidence of impaired immune function across three domains: increased susceptibility to chronic low-grade inflammation, a weakened response to bacterial infection, and impaired wound healing. The immune system's ability to respond to real threats — pathogens, injuries, cellular stress — appears to be compromised when macrophages are preoccupied with non-degradable plastic cargo.

How Aligners Release Microplastics

Understanding the mechanism helps clarify both why this happens and what, if anything, can be done about it.

Material composition. Most clear aligners — including Invisalign, the dominant brand — are made from a proprietary polyurethane-based thermoplastic called SmartTrack. SmartTrack is engineered for elasticity and clarity, which are exactly the properties needed for an orthodontic aligner. But polyurethane is still a plastic polymer, and like all plastic polymers, it is vulnerable to degradation under mechanical and thermal stress.

Mechanical stress from chewing. Even when patients comply with instructions not to eat while wearing aligners, normal jaw movement — talking, swallowing, light clenching — creates repetitive mechanical stress on the aligner material. Over thousands of cycles, this causes micro-fractures and surface degradation that release particles into saliva.

Thermal stress from hot drinks. Many patients leave their aligners in while drinking coffee, tea, or other warm beverages — or reinsert them shortly after consuming hot food. Heat accelerates the degradation of polyurethane significantly. A material that might shed minimal particles at room temperature can release substantially more at 60–70°C (140–160°F), temperatures routinely encountered with hot drinks.

Salivary degradation environment. Saliva is not a neutral medium. It contains enzymes, acids, and fluctuating pH levels that create a mildly corrosive chemical environment for plastic surfaces. Over the 1–2 week wear period of a single aligner tray, this ongoing chemical exposure combines with mechanical and thermal stress to progressively degrade the aligner surface.

Each new tray resets the exposure cycle. Aligner treatment typically involves switching to a new tray every one to two weeks. While this means each individual tray is only worn briefly, it also means that patients are continuously introduced to fresh plastic surfaces — each new tray presenting the highest rate of particle release as the surface is most intact and most actively degrading. There is no “break-in” period that reduces exposure over time; instead, the cycle repeats with every new tray for the entire duration of treatment.

Context: How Worried Should You Be?

The honest answer is: cautiously concerned, not panicked.

This is one study. The University of Buffalo findings are important and peer-reviewed, but they are early. The study examined what happens at the cellular level — specifically, how macrophages respond to MNPs in a laboratory model. It did not follow actual aligner patients over time and measure health outcomes. That research does not yet exist. It is scientifically plausible that macrophage disruption at the level observed in the lab translates to clinical consequences in patients, but “plausible” is not the same as “demonstrated.”

The immune cell angle is what makes this finding different. Most microplastic research focuses on where particles end up — bloodstream, organ tissue, breast milk. This study focuses on what the immune system does when it encounters the particles, and the finding that macrophages actively ingest and are functionally impaired by MNPs is a more mechanistic, more actionable finding than simple detection data. It is not a reason to panic, but it is a reason to take the exposure seriously rather than dismissing it.

Aligners vs. traditional braces. Metal and ceramic orthodontic brackets do not release microplastics. Stainless steel and titanium alloys are inert at the scale of normal oral exposure. Ceramic brackets made from polycrystalline alumina are similarly inert. If you have not started aligner treatment and microplastic exposure is a genuine concern, traditional braces remain a plastic-free alternative worth discussing with your orthodontist. This is not a universal recommendation — there are cases where aligners are clinically superior — but it is worth having the conversation.

Treatment duration is a mitigating factor — up to a point. Orthodontic treatment is temporary. Six months to two years of aligner wear is not a lifetime of exposure. Compare this to the decades of exposure most people accumulate from kitchen plastics, food packaging, and drinking containers. If you are already concerned about microplastics, BPA-free plastics are not as safe as marketed, your morning coffee maker may be a significant daily source, and the cumulative burden from food and drink likely dwarfs what aligners contribute. The context matters.

What research is still needed. The critical missing piece is patient outcome data. Studies that follow actual aligner patients, measure their microplastic body burden before and after treatment, and track relevant health markers over years — that research does not yet exist. Until it does, the UB findings sit in the important but preliminary category: strong enough to take seriously, not strong enough to make sweeping clinical recommendations.

What You Can Do

Whether you are mid-treatment and committed, considering aligners, or simply want to minimize exposure, here are the evidence-informed steps available to you.

• Never drink hot liquids with aligners in. This is the single most impactful behavior change. Heat dramatically accelerates polyurethane degradation. Remove your aligners before any hot drink — coffee, tea, broth, anything above roughly 50°C (120°F). The few minutes of inconvenience are worth the reduction in thermal-stress-driven particle release.
• Rinse aligners before reinserting after meals. After eating (with aligners removed), rinse both your mouth and the aligner before reinserting. Food debris and residue create additional mechanical friction surfaces that can accelerate wear. A brief rinse reduces this.
• Avoid chewing or clenching with aligners in. If you are a habitual jaw clencher or grinder, discuss this with your orthodontist. Mechanical stress is a primary driver of MNP release, and clenching applies significantly more force than normal jaw function. There may be options to address the clenching separately.
• Ask your orthodontist about the study. Your orthodontist should know about the UB 2026 research. If they are unaware, share it. This is an evolving area, and a good clinician will be able to contextualize the findings relative to your specific treatment plan and health history.
• Consider traditional braces if you have not yet started. If you are in the planning phase and microplastic exposure is a genuine concern, traditional metal or ceramic braces are worth a serious conversation. They are clinically effective for a wide range of cases and involve zero plastic particle exposure from the orthodontic hardware itself.
• Support your immune system during treatment. Since the concern is specifically about macrophage function, general immune health is relevant. An antioxidant-rich diet (rich in vitamins C and E, polyphenols from berries and leafy greens) supports macrophage function. Adequate sleep is similarly important for immune regulation. These are not substitutes for reducing exposure, but they are meaningful adjuncts.

The Bigger Picture

Orthodontic aligners are the latest item in a growing list of products we use intimately and daily that have been found to release microplastics into our bodies. Coffee makers with plastic components shed particles with every brew cycle. Paper tea bags lined with plastic polymers release billions of microplastic particles per steep. BPA-free food containers replace one harmful chemical with structurally similar alternatives. Each individual source seems small until you begin mapping the aggregate exposure across a day, a week, a lifetime.

The aligner finding matters not just because of its own contribution to body burden, but because of the immune mechanism it documents. Most microplastic research has focused on where particles are found — blood, stool, lung tissue, placenta, breast milk. The UB study focused on what happens when the immune system encounters them. That is a different and more urgent kind of question. The answer — that immune cells ingest and are impaired by plastic particles — raises questions that will need to be asked about every source of microplastic exposure, not just aligners.

The right response to this information is not to rip out your aligners, avoid all orthodontic treatment, or retreat into a state of plastic anxiety. It is to know the science, reduce what is reducible, advocate for better material standards, and support the research needed to understand the long-term consequences. We are in the early stages of understanding what decades of widespread plastic use have introduced into human biology. The aligner study is one data point in a much larger, still-forming picture.

For now: if you are in aligner treatment, follow the behavioral guidance above. If you are considering treatment, have a frank conversation with your orthodontist about the tradeoffs. And wherever possible, reduce your overall microplastic exposure from the sources that have been in your life far longer than your aligners. There is a growing evidence base for practical steps that actually move the needle.

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