UW News

May 16, 2023

School of Dentistry researchers to expand upon study into how and why our gums swell

UW News

Researchers collect a sample of oral bacteria from a study subject. Photo credit: Dr. Shatha Bamashmous.

Like many of life’s challenges, it turns out that dental plaque is all about how you respond.  

A team of microbiologists, immunologists and periodontists in the University of Washington’s School of Dentistry are expanding upon their recent discovery that people’s gums respond to plaque with three distinct types of inflammation. The team has received a $2.7 million grant from the National Institutes of Health to better understand each of those three responses.  

The team discovered that people fall into three main types of responses to bacteria in plaque, including a new type of what UW microbiologist Jeffrey McLean called “slow responders.” That discovery added new depth to the field’s understanding of gingivitis the swelling, redness and bleeding in the gums that occurs when plaque builds up on and below the gumline.  

Left untreated, gingivitis can lead to periodontitis, an irreversible condition that eats away at gum tissue and the bone that supports teeth. Periodontitis has been linked to an increased risk of heart and lung disease and other systemic diseases in humans. 

Gingivitis research could also deepen our understanding of inflammation in the rest of the body, McLean said, which can be difficult to study in real time.  

“We think eventually, knowing someone’s responder type could also relate to their response to other things. Even, potentially, the virus that causes COVID,” said McLean, an associate professor in the Department of Periodontics. “If you’re a certain type of responder, you might have that response to other viral infections, too.”  

The team will use the new grant to explore the specific mechanisms that control gingival inflammation. Researchers will identify the specific bacteria, fungi, viruses and metabolites associated with different responder types. Then they will attempt to understand what causes such vastly different inflammation responses.  

“We don’t know if it’s your prior history, or if that’s your response type. Those are the questions we try to answer eventually,” McLean said. “By knowing there’s three major response types, we can now dig in and find out what makes them different and what’s the basis of why they’re responding differently.” 

That research will rely upon the time-tested model of experimental gingivitis — the only model that allows researchers to create, and immediately reverse, inflammation in healthy human subjects. Participants will undergo a full dental cleaning, and then stop brushing several of their teeth for 21 days. As plaque builds up and inflammation sets in, researchers will take samples from both sides of participants’ mouths. After three weeks, participants will receive another cleaning, and the inflammation will recede.  

Previously, scientists believed there were two types of responses to plaque below the gumline: Some people’s gums responded to plaque with strong, swift inflammation and redness, while other people’s gums had a more muted response.  

In 2021, the researchers discovered a third type of response. They showed that some people accrue dental plaque much more slowly than others, meaning it takes longer for their gums to become inflamed. Once that inflammation kicks in, however, slow responders’ gums become just as inflamed as the strong responders’ gums. They also found unique molecular signatures in the other responder types. 

These discoveries open a path to develop treatments and products specifically designed for different response types — for example, a toothpaste that replicates the bacterial conditions found in slow responders’ mouths could help strong responders stave off gingivitis. 

Knowing your specific responder type might also change how you maintain good oral hygiene. Slow responders, for example, may not need to visit a dentist as often as those with stronger, quicker inflammation responses.  

Those discoveries won the 2022 American Academy of Periodontics’ Clinical Research Award, given to the year’s most outstanding research in the field.   

This trial will be led by principal investigators McLean and Rich Darveau, with co-investigators Diane Daubert and Yung-Ting Hsu, all of the UW School of Dentistry. The trial will be conducted in the UW Regional Clinical Dental Research Center in the Health Sciences Building with clinical site investigators Marilynn Rothen and Mary K Hagstrom. The award, from the National Institute of Dental and Craniofacial Research, also includes collaboration with the University of Texas Health Science Center at San Antonio. 

For more information, contact McLean at jsmclean@uw.edu.