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theses

Human evolutionary history spans millions of years and is marked by several periods of cultural innovation. The most recent of which is the industrial revolution, which has impacted human health and biology. While modern sociocultural change has been well studied for its effects on systemic diseases, its effects on dental health in America has not well understood. Here, we use a multidisciplinary approach to examine the effects of modern sociocultural change on oral health and diseases. First, we combined dental paleopathology and modern dental methods to examine the dental health of late 19th century and early 20th century Americans and found that the dental health of studied American populations was poorer than people living today. Also, while there are statistical significant differences in root exposure, calculus abundance, and attrition, the overall dental health of this diverse dataset was the similar to their contemporaries, despite differences in socioeconomic status.

Secondly, we conducted a comprehensive metagenomics study on the Americans who died between 1895-1950 and we observed clear distinctions between modern dental plaque communities and historical calculus microbiota. One prominent member of the historical calculus metagenome is Methanobrevibacter oralis, dominant in 41/43 of the samples analyzed. Like in the previous chapter, here I observed no distinct clustering patterns of microbiota and M. oralis pan-gene family content by age, “race”, and geography. The role of M. oralis in the modern oral cavity is that of a “co-pathogen” associated with periodontitis, however further analysis using historical reconstructions and modern genomic data will shed light on the pathogenic potential of this archaeon over time.

Lastly, as a control for all dental calculus microbiome studies, I compared the microbial communities of dental plaque to that of dental calculus and found that dental calculus is its own distinct microbial community and preserves a similar alpha diversity to other oral microhabitats. This pattern was observed when comparing a subject’s dental calculus to their own dental plaque and when comparing a subject’s dental calculus to HMP nasal, oral, and throat microbial communities. At the genus level, dental calculus harbors bacteria similar to that found in plaque, the differences reside at the species level. Due to differentially abundant taxa and less preserved human DNA, ongoing ancient microbiome research has a bias towards recovering certain taxa and less human DNA will be available to study over time.

ETD_10131

Ph.D.

Includes bibliographical references

doi:10.7282/t3-22s6-6p04

ETD doctoral

The author owns the copyright to this work.