COS 45-8 - Ecology in the dentist’s chair: Teeth cleaning and the human subgingival ecosystem

Tuesday, August 9, 2011: 4:00 PM
13, Austin Convention Center
Katie M. Shelef1, Peter Loomer2, Gary Armitage2 and David A. Relman3, (1)Department of Biology, Stanford University, Palo Alto, CA, (2)Department of Orofacial Sciences, University of California, San Francisco, San Francisco, CA, (3)Department of Microbiology and Immunology, Stanford School of Medicine, Palo Alto, CA

Complex microbial communities inhabit the subgingival crevices of the human oral cavity in both health and periodontitis (gum disease).  Previous studies on oral ecology have shown that the distinction between health and disease is one of microbial community composition and relative abundances rather than the presence of particular microorganisms. However, the ecological forces that regulate these communities remain relatively unexplored.

Professional teeth cleaning is a clinically important ecological force used to maintain and restore periodontal health. We examined the consequences of this disturbance on healthy and periodontitis-associated subgingival microbial communities. We hypothesized that these communities would differ among mouths and between health and disease, but react similarly to the disturbance treatment.

To test our hypothesis, we surveyed the changes in the microbial composition in eight subjects (4 healthy, 4 with periodontitis) from four subgingival sites and saliva before and after teeth cleaning. Each site was sampled over four time points before cleaning.  To create a disturbance, all visible microbial biomass was removed by cleaning, and we sampled the recovering plaque community over seven additional time points. Sample DNA was extracted, and the V3 region of the microbial 16S ssRNA gene was amplified and sequenced.  Preliminary results of community changes over time and space were based on correspondence analysis on OTU abundances and genera abundances. 


We found significant differences in subgingival communities among individual mouths and between health and periodontitis, consistent with our hypothesis. However, community dynamics over time were highly variable. Communities were not constant prior to disturbance, and for all mouths, pre-cleaning communities fluctuated over time, although the degree of pre-cleaning variation was mouth specific. Inter-mouth variability in response to teeth cleaning swamped any shared patterns for mouths overall and for health versus periodontitis. Furthermore, site-to-site community recovery within each individual mouth also showed high variability. Saliva remained a distinct community from the four subgingival sites throughout the time course for every mouth, suggesting that saliva communities are not acting as a reservoir for post-cleaning recolonization. All preliminary results held at both OTU and genera-level analyses.

Overall, the ecological impact of professional teeth cleaning appears to be highly mouth-specific. Our results suggest that the human oral ecosystem exhibits ecological independence, akin to island biogeography but with clinical implications.

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