Differentiation of tongue and periodontal microbiota in health and periodontitis

Objectives: The tongue and periodontium offer specialized niches for the oral microbiota, with dysbiotic changes occurring in the subgingival and supragingival niches during the development of chronic periodontitis. Whilst the microbial ecology of the tongue is generally associated with oral malodour, clinical studies have shown an association between oral malodour and chronic periodontitis. In this study, the microbiota on the tongue of individuals with oral health, chronic periodontitis and gingivitis, was characterized in relation to the periodontal microbiota.
Methods: Tongue scrapings, subgingival and interdental plaque were collected and the bacterial 16S rDNA V3-V4 region sequenced using the HOMINGS methodology. Sequences were analyzed using Minimum Entropy Decomposition which enabled determination of sequence variation within oral taxa at 1-nucleotide resolution. Volatile Sulfur Compound (VSC) concentrations were measured in the breath of participants using Oral Chroma™.
Results: Breath methanethiol was associated with both clinical indices of periodontitis and the ecological differences observed in subgingival and interdental niches in disease compared to health. Whilst the tongue and subgingival microbiota showed niche specialization in their community composition, disease associated overlaps were observed between the niches in the oligotype distribution of health and disease associated taxa. Clinical indices of gingivitis and periodontitis such as plaque index and probing depth were also associated with changes in tongue ecology.
Conclusions: Malodour associated with chronic periodontitis may be due to a dysbiotic tongue ecology as it is influenced by the changes occurring in the periodontal niches. The interdental plaque may act as a reservoir for periodontopathic taxa in health, whereas the tongue may also carry these taxa as transient species.