Associations between subgingival plaque bacterial morphotypes and clinical indices?

The aim of the present study was to evaluate possible associations between subgingival plaque bacterial morphotypes, as assessed by darkground microscopy, and clinical indices of routine adult chronic periodontitis. Clinical indices were plaque index (PlI), gingival index (GI), sulcus bleeding index (SBI), papilla bleeding index (PBI), attachment loss (AL), pocket depth (PD) and probeable pocket depth (PPD). Apical border plaque was sampled in vivo and after extraction to test whether direct or indirect sampling affected any such associations. Similarly, pocket depth and attachment loss were also assessed directly and indirectly on the same teeth, in vivo or after extraction. The influence of the type of index used to record inflammation (GI, SBI, PBI) was also assessed, as were the effects of the numbers of sampled subjects and the method of analysis, which comprised the use of transformed and untransformed data and of parametric and non-parametric tests. Data were collected in relation to the approximal surfaces of 44 teeth extracted from 22 adults (2 teeth each) and from 1 pair of contralateral upper anterior or premolar teeth in each of 100 adults, all which untreated routine chronic periodontitis. Selected subjects had greater than or equal to 4 mm probeable pocket depth and/or attachment loss, and radiographic evidence of bone loss in relation to 1 approximal surface on each of 1 pair of contralateral anterior or premolar teeth, or to 2 teeth scheduled for extraction. Plaque preparation and darkground microscopy were as described previously. Insignificant associations (p greater than 0.05) were demonstrated between supragingival plaque (PlI) and periodontal inflammation (GI, SBI, PBI) or destruction (PPD and AL), as well as between inflammation and attachment level. In contrast, significant moderate associations (r = 0.5-0.77) were demonstrated between each of the 3 morphotype groups; spirochaetes, other motiles and cocci. Spirochaetes showed a significant moderate (r = 0.5) positive association with pocket depth with a 2.43% mean increase of spirochaetes for each 1 mm increase of PPD. Although highly significant associations (r = 0.9) were demonstrable between the 3 inflammation indices (GI, SBI, PBI) themselves, only PBI showed significant positive associations (r = 0.3) with spirochaetes and other motiles. Also, PlI showed significant associations with each of the 4 morphotypes (r = 0.3-0.5). The heterogeneity of spirochaetes and other motiles as well as the multiplicity of possible aetiological microbial agents in plaque may have resulted in underestimated associations between subjects as well as undetectable association within a given mouth using only 4 morphotype groups.(ABSTRACT TRUNCATED AT 400 WORDS)