Effect of sampling on the composition of the human subgingival microbial flora

Eighteen adults with chronic periodontitis participated in an experiment to study the effect of sampling the subgingival microbial flora of periodontal pockets on the subsequent microbial composition of the pocket contents. Samples of bacteria were collected atraumatically with a periodontal curette from periodontal pockets. The sample was suspended in 0.85 N saline containing 1 % gelatin. A drop of the suspension suitably diluted was applied to a microscopic slide and the specimen immediately examined by darkfield microscopy. The microbial flora was classified into coccoid cells, motile cells, spirochetes and “other” microorganisms. The proportion of bacteria in each of these 4 categories was expressed as a percentage, based on the examination of the first 200 bacteria detected in a series of high power fields (mag. × 1200). The microbial composition of the contents of each of 6 pockets was examined at day 0 (baseline data) and each pocket reexamined once either 3, 7, 14, 21, 28 or 42 days later. In addition to the microbial examination, GI and P1I scores and probing depth measurements were also obtained at day 0 and at the reexamination. The results indicated a tendency toward reduced P1I and GI scores at the various reexaminations in comparison to baseline scores. Probing depth measurements did not change significantly. A slight but significant proportional increase in coccoid cells was detectable at 3 days and persisted at more or less the same level for the remainder of the experiment. Spirochetes showed a proportional decrease from baseline during the first week, while motile cells were proportionally reduced only on day 3. No significant changes occurred in the “other” microorganisms. It is not clear from the results if the alterations in the microbial flora were due to the sampling procedure per se or to a change in oral hygiene habits in a population of new patients suddenly more aware of their periodontal status. The clear-cut changes from baseline to day 3 levels and the subsequent lack of change from the 3-day through the 42-day intervals suggest that sampling per se may have contributed only to the changes from baseline noted in the first few days. The change in oral hygiene habits, however, may have contributed not only to the initial changes from baseline, but also to the maintenance of the new microbial proportions at a stable level for the remainder of the experimental period. Despite changes from baseline, all criteria remained well within the range of values that might be expected at periodontally diseased sites in patients with untreated chronic periodontitis.