A STATISTICAL APPROACH TO THE ECOLOGY OF ACTINOBACILLUS-ACTINOMYCETEMCOMITANS IN SUBGINGIVAL PLAQUE

Structured complexity may be a key feature of the microbiota residing in periodontal ecosystems. Recently, several attempts have been made t o analyse the mutual interdependence of certain organisms in subgingiv al plaque and/or to identify clinical conditions which might influence presence or absence of these bacteria in subgingival plaque. The aim of the present analysis was to compare the results of different models derived from logistic regression of several clinical factors on the p resence of Actinobacillus actinomycetemcomitans in subgingival plaque of adult periodontitis patients all harbouring this organism, Models a ssuming independence of observations or assuming independent observati ons with the level of response depending on the individual subject wer e compared to models considering the correlated structure of the acqui red data by employing Generalized Estimating Equation (GEE) methods. S ignificant associations found when neglecting the correlated observati ons within a given subject as, e.g., between A. actinomycetemcomitans and amount of supragingival plaque, bleeding on probing, or attachment loss, became generally spurious in the GEE approach. Thus, presence o f A. actinomycetemcomitans only depended on periodontal probing depth. It was concluded that the correlated structure of observations in an oral cavity should be carefully considered when associations between c linical factors are calculated.