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By the Skin of your Teeth: Investigating Chronic Periodontal Disease through History

Dental calculus (mineralised plaque) on skeletal remains

Chronic periodontal disease is a very common chronic condition which includes the familiar gum disease but can spread to the other supportive tissues around the tooth, potentially resulting in bone deterioration and tooth loss.  The disease is caused by overgrowth of harmful bacteria in plaque and tartar deposits around the gum-line. Beyond its effects on oral health, individuals with chronic periodontitis are also at higher risk for cardiovascular disease, stroke, diabetes, and respiratory illnesses.

In order to effectively treat periodontal disease today, we need to have a clear understanding of both the species of bacterial pathogens that cause the disease in the past and today, and how these bacteria have evolved through time. Archaeological studies have known that humans have been suffering from periodontal disease for millennia, although frequency and severity vary between geographic areas and historical periods. This study will investigate the genetic diversity and evolution of periodontal pathogens from five historic time periods in Yorkshire through biomolecular analyses of fossilised plaque on human skull remains. It will also examine different human immune responses over time in order to learn more about the bacteria's virulence and adaptability.

The initial results of metagenomic analyses indicate that bacterial DNA is well preserved in dental calculus, and that DNA yields are sufficient to reconstruct ancient periodontal pathogen genomes. We have completed genome reconstructions for two periodontal pathogens, Tannerella forsythia and Treponema denticola, dating to the Medieval period. Both genomes are distinct from modern strains, as well as from medieval strains recovered from Germany. Our results confirm that, in general, dental calculus represents a robust substrate for investigating ancient oral microbiomes - we are in the process of documenting variation in oral microbial communities through time and space.

Camilla Speller presented an overview of the project to public audiences at the Archaeology Open Day at the Washburn Heritage Centre in Fewston, May 8, 2013. She gave a talk entitled "the Yorkshire Oral Microbiome Project: Then and Now" discussing the archaeological samples from Fewston included in the C2D2 project, and then potential of dental calculus to understand past health. Speller also gave an interview on BBC Radio York's Science program related to the research output "Pathogens and host immunity in the ancient human oral cavity".

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