Figure 9.

 Mean counts (×10⁵) of subgingival taxa detected in 123 periodontally healthy subjects enrolled in a 3‐year preventive program. Subgingival plaque samples were collected from the mesio‐buccal surface of every tooth present at baseline and at 1, 2 and 3 years after therapy. Counts of 40 subgingival species were measured for each sample using checkerboard DNA–DNA hybridization. Sites were grouped into three categories: (i) sites that did not show bleeding on probing in any of the visits (yellow) (n = 1,489); (ii) sites that had bleeding on probing at one or two visits (orange) (n = 1,593); and (iii) sites that had bleeding on probing at three or four visits (red) (n = 309). Data were averaged within subjects, across subjects and then across the different visits within each site category, separately, in order to obtain a summary measure of cumulative exposure to the 40 taxa over time. The species were ordered and grouped according to the complexes described by Socransky et al. ( 337 ). The figure was generated from data from Bogren et al. ( 38 ).