Microbial Shifts in Early Subgingival Biofilm Formation

Objectives: To compare early microbial changes in subgingival biofilm formation in periodontally healthy and periodontitis subjects. Methods: 30 periodontally healthy and 8 periodontitis subjects were recruited. Subgingival plaque samples were taken from the mesial aspect of each tooth, at entry, and individually analyzed for their content of 41 bacterial species using checkerboard DNA-DNA hybridization. The teeth were cleaned, immediately re-sampled and samples analyzed in the same fashion. The subjects refrained from oral hygiene for 7 days. Subgingival plaque samples were taken from 7 teeth in randomly selected quadrants at 1, 2, 4 and 7 days and analyzed as described above. Counts of each species were determined for each sampled site and averaged across sites in each subject at each time point. Significance of difference for each species over time was determined by the Friedman test and between clinical groups at each time point using the Mann-Whitney test. Results: Mean (x 10⁵, ±SEM) total DNA probe counts were 16.3±3.1 and 31.8±10.0 on entry and 4.5±0.8 and 4.3±0.8 immediately post-cleaning in healthy and periodontitis subjects respectively. At 2 days, total counts in healthy and periodontitis subjects exceeded baseline values (21.8±5.9, 56.2±30.7). There were striking differences between health and periodontitis in the patterns of re-colonization. In Periodontitis, counts of most species increased rapidly to well above baseline values by 2 days and 17 species, including the actinomyces and streptococci, decreased to about baseline levels by 7 days. For other species, the counts plateaued or increased. Some species did not reach baseline levels by 7 days including C. gracilis, E. nodatum, P. gingivalis and T. denticola. For healthy subjects, the counts of most species increased slowly over time reaching or exceeding baseline values by 7 days. Conclusions: The kinetics of subgingival plaque re-development in periodontitis and health differs markedly. Supported by NIDCR grant DE14368.