Supragingival plaque may modify the effects of subgingival bacteria on attachment loss

Background: Bacterial interactions in response to local and systemic factors may explain important features of the pathogenesis of periodontal disease. This study evaluates the role of supragingival plaque level on the relationship between subgingival microorganisms and the risk of attachment loss. Methods: The study population consisted of 386 white women aged 45 years and older who had at least seven teeth. Subgingival plaque samples were taken from the mesio-buccal surface of six maxillary and six mandibular teeth using paper point technique. The samples were pooled, and immunofluorescence microscopy was performed to identify the following target microorganisms: Actinobacillus actinomycetemcomitans (Aa), Tannerella forsythensis (Tf), Campylobacter rectus (Cr), Prevotella intermedia (Pi), Capnocytophaga species (Cs), Porphyromonas gingivalis (Pg), Eubacterium saburreum (Es), and Fusobacterium nucleatum (Fn). The presence or absence of supragingival plaque and clinical attachment loss (CAL) were assessed at the same 12 sites where subgingival plaque samples were taken. The association of each microorganism with CAL was tested using multiple logistic regressions controlling for age, smoking status, and diabetes. Odds ratios (OR) and their 95% confidence intervals (CI) were calculated. Results: At low supragingival plaque levels, only the presence of Pg was significantly associated with CAL (OR: 6.41, 95% CI: 1.30 to 31.70); all remaining microorganisms were also associated with increased but nonsignificant risk of CAL. At high supragingival plaque levels, the presence of Tf (OR: 2.40, 95% CI: 1.42 to 4.04) and Pg (OR: 3.71, 95% CI: 1.63 to 8.42) was significantly associated with increased risk of attachment loss. By contrast, the presence of Cs (OR: 0.55, 95% CI: 0.30 to 1.01) and Es (OR: 0.35, 95% CI: 0.15 to 0.82) was associated with decreased risk of attachment loss. Fn, Pi, and Cr were not significantly associated with CAL at either low or high supragingival plaque levels. Conclusions: This study suggests that an association of certain subgingival microorganisms with CAL changes in relation to supragingival plaque levels in older adult women. It also suggests that the overall effect of dental plaque is a function of the balance between pathogenic and other microorganisms that colonize this environment. Therefore, all microorganisms in the biofilm, including those with no apparent association with overt disease and those with negative associations, may play roles in the pathogenesis of periodontal diseases.