Periodontal disease occurs in 13 percent of humans today. Why are humans even susceptible to periodontal disease, when most animals do not get periodontal disease? Is it human behavior or something else that contributes to chronic inflammatory disease in humans?

It can't be modern living or dental hygiene. The inflammatory disease-causing bacteria has been found in a Medieval German population, by analyzing the dental calculus - plaque - from teeth preserved for 1,000 years.

Christina Warinner, research associate in the Molecular Anthropologies Laboratories at the University of Oklahoma, assembled an international team of experts using modern technology to build a detailed picture of people from the Medieval period, by extracting DNA from samples of the dental calculus.

The samples were small, but dental calculus has a thousand times more DNA than bone. They also looked at and analyzed the protein in the samples for an even more detailed look.

"Through protein sequencing, we can reconstruct infection and immune processes. It is like excavating a battlefield archaeological site, just at a molecular scale," says Enrico Cappellini, senior researcher from the University of Copenhagen in Denmark. 

Lead author of the study, Dr. Christina Warinner, extracts ancient DNA under clean room conditions at the University of Zürich’s Centre for Evolutionary Medicine. Photo credit: Christina Warinner.

"What makes dental calculus so unique," according to Warinner, "is that it acts both as a long-term reservoir of the oral microbiome and as a trap for dietary and environmental debris. This allows us to investigate health and disease, as well as reconstruct aspects of an individual's life history and activities. Never before have we been able to retrieve so much information from one small sample."

Matthew Collins, a researcher from the University of York in the United Kingdom, said, "The preservation of biomolecules in dental calculus is remarkable — a microbial Pompeii." He added, "As we learn more about the evolution of the oral microbiome, I can imagine a future in which most archaeologists regard calculus as more interesting than the teeth themselves." 

The findings are intriguing because no one knew what, if anything, would be preserved in dental calculus. The results add to the body of work about the long-term relationship between humans and their resident microbes. "The study of ancient microbiomes helps us understand the evolutionary history of human health and disease," says Frank Rühli, director of the Centre for Evolutionary Medicine at the University of Zürich. "It informs modern medicine."

Published in Nature Genetics. Source: University of Oklahoma