Dental plaque holds far more than just a gross reminder to keep brushing your teeth. New research shows that buried within plaque is a history of the bacteria, food, and other microscopic particles that crossed the teeth it's come to coat. While plaque may have less to say about those with good oral hygiene today, an international group of researchers has found that it could reveal quite a bit about our ancestors: on the teeth of several 1,000-year-old skeletons, researchers were able to determine health and dietary information and to analyze the bacteria that once existed in their mouths.
"Ancient plaque ... is going to be a major new frontier."
"The most interesting — but not especially staggering finding — is that it was possible to reconstruct the whole genome of a bacteria living in a Medieval nun's mouth and reveal that it lacked antibiotic resistance genes found in modern strains," Matthew Collins, a University of York professor involved with the research, writes in an email to The Verge. The researchers identified a number of pathogens and disease-causing bacteria within the plaque and, in particular, found that gum disease was caused by the same bacteria then as it is today.
But that's merely the tip of the iceberg when it comes to what's hidden inside of plaque. "We think that ancient plaque ... is going to be a major new frontier in the study of the oral microbiome," Collins writes. Most ancient human remains have hardened plaque in their mouths, and the researchers say that future studies may be able to outline how the ecosystem of microbes in our mouths has changed over time as humans changed their diets and behaviors.
Plaque may be among the better sources of information on that too. Because hardened plaque will degrade slower than bone, in some instances, it may be a more reliable and available resource from ancient human remains. That it includes traces of food and dietary habits is particularly valuable too, since that information isn't always evident through other records.
"For us, the most remarkable finding is that we have uncovered a sort of 'Pompeii of the mouth,'" Collins writes, comparing hardened plaque to the Roman city buried and preserved in ash. "We can not only find food particles, but also bacteria, and evidence of the battle they were having with the human immune system, a battle fought 900 years ago and frozen in time."
The research was published last month in Nature Genetics and was led from the University of Zürich, the University of Copenhagen, and the University of York. While Collins acknowledges that this isn't plaque's breakthrough moment in research just yet, he suggests that this work could be its precursor. Now that researchers know where they can look, they may be able to begin identifying changes in diet that led to issues of health that we're still dealing with today.