If you are like me, you brush your teeth—too vigorously, I’m told—with a plastic rack of plastic bristles. You use your plastic brush to lather a paste pushed from a plastic tube. When you have a cavity, you go to a dentist who might fill the hole with a plastic composite then sand it flush right there in your mouth. Say you grind your teeth at night. Your dentist might prescribe you a fitted piece of cured acrylic to grind into instead, the surface of which eventually gets visibly rough and worn. Perhaps your teeth are not very straight, so you contemplate getting aligners—thin sheets of thermoplastic that would be heated and then molded to the contours of your mouth and that you would need to wear almost constantly. The retainers you’d wear afterward to keep your newly straight teeth in place might also be plastic.
Nearly every part of modern dentistry and orthodontics involves—and is enhanced by—this remarkably useful material. In some cases, it’s part of necessary medical treatments: A cavity must be filled to prevent worse damage, and at least the plastic-glass composite filling your cavity won’t leach mercury, like the silver fillings that were more common for prior generations. But in cases that are purely aesthetic—tooth straightening can fall into this category—the trade-offs may look different.
Although many hands are wrung over the microplastics that pass from our tea bags and carpets and water bottles into our bodies, when it comes to oral health, we welcome plastic intentionally, and sometimes permanently, directly in our mouths. This troubles Adith Venugopal, an orthodontist and a senior lecturer in the Faculty of Dentistry at the University of Otago, New Zealand; he published a letter in a dental journal last year raising concerns about the micro- and nanoplastics that slough off aligners and retainers. A robust body of research links chemical compounds that leak out of plastic to hormone disruption, developmental abnormalities, and cancer, but the effect of the actual fragments of plastic accumulating in our tissues and organs is less clear. Venugopal started researching microplastics in orthodontics after seeing a paper that found patients with micro- and nanoplastics embedded in their artery plaques were more likely to have a heart attack or stroke. Plastic exposure from dentistry or orthodontics, Venugopal thinks, is ethically different than the worries over plastic exposure resulting from consumer choices. “Prescribing it from a medical standpoint, knowing that it would leach out and cause so many millions of particles to be ingested on a yearly basis, is troublesome, isn’t it?” he told me. “I mean, that’s the first thing, to do no harm.”
But what the harm of dental and orthodontic plastics might be is, as of yet, poorly understood. Venugopal’s letter is one in a growing body of statements and studies coming out of those professions that ask if plastic may be harming patients. (“Microplastics: An Orthodontic Concern!” yelped an editorial in the Journal of the World Federation of Orthodontists last year.) So far, few if any papers have looked at the issue in humans, though preliminary studies attempt to replicate aspects of mouths in a lab, by simulating wear and tear from liquid and friction. The Nordic Institute of Dental Materials has been looking into the release of microplastics from night guards. The chief scientific officer of the American Dental Association’s research arm, Ben Wu, said in a statement that the association is “closely monitoring the scientific literature on microplastics” but that “no clinical evidence currently exists showing a meaningful oral or overall health impact from the particles.” The ADA’s best current advice to patients is to monitor their plastic dental devices for cracks, roughness, or breaks, and look into a replacement. Or, Wu suggested, instead of opting for clear plastic aligners, a person could get metal braces or retainers.
The American Association of Orthodontists is taking a more proactive approach. “This is certainly something that is high in our consciousness,” Steven Siegel, the organization’s president, told me. The association recently convened a panel of researchers to look at all of the available studies to date, and has asked its awards committee to put out a call for proposals for new research in this area. It hasn’t taken an official position on microplastics, because the group, like Venugopal and the ADA, considers the available research to be “preliminary,” he said. But it believes microplastics are “an issue that we need to pay close attention to.”
Clear orthodontic aligners have become a particular focus of early research attention, given the nature of their use. “They’re supposed to be worn about 22 hours a day for optimal tooth movement,” Venugopal told me. People typically change theirs out after one or two weeks and continue that cycle for months to years. A group of Italian researchers published a paper in 2023 that found that aligners did indeed leach microplastics after seven days when exposed to artificial saliva in a lab. But Venugopal points out that the lab study couldn’t capture the onslaught of enzymes, teeth gritting, and temperature variation that a real human mouth inflicts. So he and a doctoral student are now conducting what he believes is the first real-world study of how much microplastic leaches into saliva while an actual person is wearing aligners.
There is always the alternative that the ADA pointed to: metal braces. Although these may still use a small amount of plastic adhesive to bond the equipment to the front of a wearer’s teeth, at least the plastic isn’t on the chewing surface. (This doesn’t elide concerns entirely; one paper has tried to characterize the microplastics sloughed off by orthodontic rubber bands. It may be a lot.)
In his own practice, instead of prescribing plastic retainers, which can be removed, Venugopal says he’s intentionally prescribing more fixed-wire retainers for people who would get a similar benefit from either. (Some patients would still benefit more from having thermoplastic molded ones, he said. But for those who could go either way, they’re getting metal.) “So, yes, it is affecting me as a clinician as well,” he said. If a patient were to ask him about microplastics, he would tell them what research has shown (that microplastics leak from objects such as aligners) and what it hasn’t (whether the leakage from an aligner or retainer alone poses a significant danger). “Without being informed about that, I don’t want to scare patients,” he said. Each of his patients—like everyone—is already inhaling, drinking, and eating microplastics just by living in the world.
The only way to get us out of the dental-plastic loop will be to develop different materials. A plastic-bristled toothbrush may add approximately 30 to 120 microparticles of plastic to your diet with each brushing, according to one study. Another put the estimate at an average of 39 particles a day. Either calculation suggests that a plastic toothbrush adds tens of thousands of particles to one’s yearly load of microplastics, which is significant when considering that estimates of microplastic exposure from food, air, and water put a person’s yearly particle load at more than 100,000. Nonplastic toothbrush options exist, but they’re hardly mainstream. Most dental floss is plastic, too—alternatives, such as silk floss, are mostly a health-food-store find.
Conversely, not brushing your teeth would be a dental disaster, and no one should choose not to fill a cavity. The downside of an untreated cavity almost certainly far exceeds any hypothetical harm from additional microplastic exposure. “I was at a dental meeting a couple of months back, and I bit down and I fractured two molars, old fillings,” Siegel said. “And I went to my friend who’s an excellent dentist. I didn’t hesitate to have composite restorations with the materials that we use. I put it in that context: I think that the release, if any, of some of the compounds and microplastics is probably relatively minimal.”
The same goes for mouth guards: Siegel said he wasn’t aware of any material that could take the place of my acrylic set prescribed for tooth grinding. “Whether it’s crossing the street or having a medical procedure, one always looks at the risks and benefits,” Siegel told me. “I try and limit microplastic exposure in my own life. I try not to reheat things in plastic containers. I limit processed-food intake, things like that.” But, he said, when it comes to the health of your mouth, you want to ask yourself: Do the benefits of protecting your teeth and jaw outweigh the potential risks of adding to your microplastic dose? “For me personally, if I ground my teeth, I would wear a night guard,” he said. That was a sensible assessment, I thought, even if—for now—we don’t really have the information to base that decision on. Still, I got his point. I’ll pull mine out of storage tonight.
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