A team of researchers has identified how different people respond to the accumulation of dental plaque, helping us understand the vulnerability of some to serious conditions that lead to tooth loss and other problems.
The study was led by University of Washington researchers and recently published in the journal Proceedings of the National Academy of Sciences (PNAS).
Buildup of plaque, the sticky biofilm covering teeth and gums, can induce gingivitis, or gum inflammation if left unchecked. Gingivitis, in turn, can lead to periodontitis, a serious infection that can damage and destroy the gum and bones supporting teeth. As well as causing tooth loss, this chronic inflammation can also trigger heart disease, diabetes, cancer, arthritis, and bowel diseases.
The researchers also discovered a range of inflammatory responses to oral bacterial accumulation. When bacteria build up on tooth surfaces, it generates inflammation as the body responds. Two known major oral inflammation phenotypes were known: a high or strong clinical response and a low clinical response. The team identified a third phenotype, which they dubbed ‘slow’: a delayed strong inflammatory response in the wake of the bacterial buildup.
The study also found that subjects with low clinical response also showed a low inflammatory response for a variety of inflammation signals. “Indeed, this study has revealed a heterogeneity in the inflammatory response to bacterial accumulation that has not been described previously,” said Dr Richard Darveau of the UW School of Dentistry, one of the study’s authors.
Study co-author Dr Jeffrey McLean said, “We found a particular group of people that have a slower development of plaque as well as a distinct microbial community makeup prior to the start of the study.” The authors wrote that understanding the variations in gum inflammation could help screen for higher periodontitis risk. In addition, it is possible that this variation in the inflammatory response among the human population may be related to the susceptibility to other chronic bacterial-associated inflammatory conditions such as inflammatory bowel disease.
Additionally, the researchers found a novel protective response by the body, triggered by plaque accumulation, that can save tissue and bone during inflammation. This mechanism, which was apparent among all three phenotypes, utilises white blood cells known as neutrophils. In the mouth, they act something like cops on the beat, patrolling and regulating the bacterial population to maintain a stable condition known as healthy homeostasis.
In this instance, plaque is not a villain. To the contrary, the researchers said that the proper amount and makeup of plaque supports normal tissue function. Studies in mice have also shown that plaque also provides a pathway for neutrophils to migrate from the bloodstream through the gum tissue and into the crevice between the teeth and gums.
When healthy homeostasis exists and everything is working right, the neutrophils promote colonization resistance, a low-level protective inflammatory response that helps the mouth fend off an excess of unhealthy bacteria and resist infection. At the same time, the neutrophils help ensure the proper microbial composition for normal periodontal bone and tissue function.
The researchers’ findings underscore why dentists preach the virtues of regular brushing and flossing, which prevent too much plaque buildup. “The idea of oral hygiene is to in fact recolonise the tooth surface with appropriate bacteria that participate with the host inflammatory response to keep unwanted bacteria out,” Dr Darveau explained. The bacteria start repopulating the mouth’s surfaces spontaneously and almost immediately afterward, Dr Darveau said.
Source: University of Washington School of Dentistry
Journal information: Bamashmous, S., et al. (2021) Human variation in gingival inflammation. PNAS. doi.org/10.1073/pnas.2012578118.
