A spatial gradient of bacterial diversity in the human oral cavity shaped by salivary flow.

Spatial and temporal patterns in microbial communities provide insights into the forces that shape them, their functions and roles in health and disease. Here, we used spatial and ecological statistics to analyze the role that saliva plays in structuring bacterial communities of the human mouth using >9000 dental and mucosal samples. We show that regardless of tissue type (teeth, alveolar mucosa, keratinized gingiva, or buccal mucosa), surface-associated bacterial communities vary along an ecological gradient from the front to the back of the mouth, and that on exposed tooth surfaces, the gradient is pronounced on lingual compared to buccal surfaces. Furthermore, our data suggest that this gradient is attenuated in individuals with low salivary flow due to Sjögren's syndrome. Taken together, our findings imply that salivary flow influences the spatial organization of microbial communities and that biogeographical patterns may be useful for understanding host physiological processes and for predicting disease.

Characterization of dental anatomy and gingival biotype in Asian populations.

Gingival and dental characteristics are risk factors for periodontal problems. With short or fused roots, a decreased periodontium results in some attachment loss, compromising periodontal stability. Similarly, with an increased incidence of thin gingival biotype, inflammatory and traumatic insults may result in gingival recession. Anecdotally, Asian dentitions have been described as having short roots with "thin gingiva". This cross-sectional study will utilize clinical data and radiographic interpretation to ascertain whether this clinical impression is valid.