UB orthodontics researchers evaluate microplastics’ effect on immune system

BUFFALO, N.Y. — In a groundbreaking study, orthodontics researchers at the University at Buffalo School of Dental Medicine recently discovered how synthetic polymers, including clear aligners, retainers and sleep devices, may affect the immune system.

Thikriat Al-Jewair, DDS, L.B. Badgero Endowed Chair and associate professor, and Stephen Warunek, DDS, clinical assistant professor in the Department of Orthodontics, collaborated with medical researchers at the University of Pittsburgh’s Thomas E. Starzl Transplantation Institute to explore how plastic orthodontic devices could affect the oral cavity and the overall health of users.

What they found was that these devices, particularly aligners, release microplastics and the even-smaller nanoplastics (MNPs), which are then ingested by macrophages, specialized immune cells that live inside organs and are meant to clear foreign debris and protect against infection and inflammation.

“Because microplastics do not biodegrade, they can persist inside macrophages,” Al-Jewair explains. “Over time, this may trigger chronic inflammation, weaken the body’s ability to fight infection and interfere with proper wound healing.”

Their study, the first to capture live cell imaging of macrophages ingesting aligner-derived MNPs, was published in the February 2026 issue of Progress in Orthodontics.

“It’s not only that the macrophages ingest them and just sit there,” Warunek says, “but that the microplastics are skewing their immune responses.”

The article’s first author, Jordan Warunek, is Stephen Warunek’s son. He received a master’s degree in microbiology and immunology from UB in 2020 and is completing his doctorate in immunology under his adviser, Hēth Turnquist, PhD, at the University of Pittsburgh, which is how the two institutions connected.

Microplastics discovered in multiple organs

For the past two decades, scientists have increasingly sounded the alarm regarding microplastics — fragments smaller than 5 millimeters that form when plastic products degrade. They infiltrate the water we drink, food we eat and air we breathe, posing dangers to both the environment and human health.

While there are still many unknowns about the level of harm to our bodies, these tiny plastic particles have been detected in human tissues, including the lungs, liver, placenta and even the brain. Some studies have linked microplastics exposure to cardiovascular problems, gene damage and fertility issues. The smaller the particle, the likelier it will stay inside tissues and organs.

Clear aligners are the most frequently used of the orthodontic devices tested. Typically, aligner treatment requires multiple aligner sets, with each set used for a week or two before being replaced by the next. Like traditional braces, aligners gradually move teeth into their proper position.

For the study, the team evaluated six orthodontic devices manufactured by different companies — a mix of clear aligners, retainers and sleep appliances for temporomandibular joint disorders (TMD) — to determine the severity of the microplastic shedding, along with what happens when immune cells encounter these plastic particles.

Three of the materials were produced using traditional thermoforming, while three were 3D-printed. They submerged all of them in artificial saliva, incubated and put them through a vortex mixer daily for one week. Particle release was quantified by flow cytometry and imaged by scanning and transmission electron microscopy.

They discovered that the direct-printed polymers shed a larger amount of microplastics than the thermoformed ones. Both types, however, shed measurable MNPs fragments that are readily internalized by macrophages.

Aligners, a billion-dollar business

The study comes at a time when the market for clear aligners, valued at $6.39 billion in 2024, is exploding.

On average, patients require 20 to 50 sets of aligners. Conservatively, 100,000 patients are undergoing treatment with an average use of 30 aligner sets, according to the study. This adds up to approximately 3 million clear aligners in use worldwide every day, according to the study.

Invisalign, one of the thermoform polymers tested, came onto the market in 1999, while 3D-printed versions have only been used for teeth straightening over the last few years, Warunek explains.

In many orthodontic circles, 3D-printed aligners are considered the future for their speed, precision and efficiency.

“Direct-printed aligners offer greater customization and production efficiency,” Al-Jewair says. “The digital workflow may help streamline treatment, enabling same-day delivery and reducing appointment frequency, in some cases”

Al-Jewair adds that ongoing research is also evaluating surface characteristics, as slightly rougher or more porous texture could influence durability and the potential for very small particle release over time.

While aligners are here to stay, manufacturers and researchers should continue evaluating the materials used in their production to ensure safety and performance, Al-Jewair and Warunek say.

Further research required

Al-Jewair says the team hopes to continue its research and, eventually, move into clinical trials. In the meantime, she emphasizes that the findings are based on preliminary in-vitro studies and will need to be validated through well-designed clinical studies before any conclusions can be drawn.

Questions have arisen, such as: Are the immune responses temporary? Are they reversible?

“There are still many unanswered questions,” she says, “and I hope to continue this line of research to help address them.”