Factors affecting supragingival biofilm composition. I. Plaque mass

Objectives: To examine the relationship between plaque mass, clinical parameters and supragingival biofilm composition. Methods: Supragingival plaque samples were taken from up to 28 sites in each of 187 systemically healthy adult subjects at baseline (N samples = 4,745; mean 25.4 per subject). All samples were individually analyzed for their content of 40 bacterial species using checkerboard DNA-DNA hybridization. The relationship between plaque mass and microbial composition was examined by sub-setting the data into 10 groups based on 10 percentile increments of the total DNA probe counts. Differences among groups in terms of species counts and proportions and between total plaque mass and clinical parameters were sought using the Kruskal Wallis test and adjusted for multiple comparisons.

Results: The mean total plaque mass per subject (10⁵) for the 187 subjects ranged between 6.5-201.0 (median 48.8). With increasing total plaque levels there was a change in the proportions of individual species and microbial complexes. “Small plaques” were characterized by high proportions of streptococci (yellow complex), species in the orange complex including Fusobacterium nucleatum ss vincentii, Fusobacterium nucleatum ss nucleatum and Prevotella intermedia, and purple complex species, Veillonella parvula and Neisseria mucosa; plaques of moderate mass were characterized by high proportions of Actinomyces and purple complex species, while “large plaques” exhibited increased proportions of green (Capnocytophaga gingivalis, Eikenella corrodens, Capnocytohaga sputigena) and orange complex species. Measures of gingival inflammation, pocket depth, attachment level and recession were significantly positively associated with plaque mass. Increased supragingival plaque mass was related to increased pocket depth irrespective of presence or absence of gingival inflammation.

Conclusions: A major factor affecting supragingival biofilm composition is the mass of the plaque sample which in turn is related to the clinical status of the adjacent periodontal tissue. Supported by NIDCR grants DE12108 and DE14368.