The effect of repeated

removal on the composition of the supra-and subgingival microbiota Abstract Background, aims: The purpose of the present investigation was to determine the effect of weekly professionally administered supragingival plaque removal on the composition of the supra and subgingival microbiota. Methods: 18 adult subjects with periodontitis who had been treated and were in a maintenance phase of therapy were clinically and microbiologically monitored at baseline, 3, 6 and 12 months. After the baseline visit, the subjects received scaling and root planing followed by professional supragingival plaque removal every week for 3 months. Clinical measures of plaque accumulation, bleeding on probing (BOP), gingival redness, suppuration, pocket depth and attachment level were made at 6 sites per tooth at each visit. Separate supra (NΩ1804) and subgingival (NΩ1804) plaque samples were taken from the mesial aspect of all teeth excluding third molars in each subject at each time point and evaluated for their content of 40 bacterial taxa using checkerboard DNA-DNA hybridization. Significance of changes in mean counts, prevalence and proportions of bacterial species over time in both supra and subgingival samples were determined using the Quade test and adjusted for multiple comparisons. Results: Mean % of sites exhibiting plaque, gingival redness and BOP were significantly reduced during the course of the study. Significant decreases in mean counts were observed in both supra and subgingival samples. Mean total DNA probe counts (¿10 5 , ∫SEM) at baseline, 3, 6 and 12 months were: 133∫19, 95∫25, 66∫6, 41∫6 (pϽ0.001) for supragingival samples and 105∫22, 40∫10, 19∫4, 13∫3 (pϽ0.001) for subgingival samples. Mean counts of 22 of 40 and 34 of 40 species tested were significantly reduced in the supra and subgingival samples respectively over the monitoring period. For example, mean counts of Porphyromonas gingivalis ¿10 5 at baseline, 3, 6 and 12 months in the subgingival plaque samples were 2.0∫0.4, 0.5∫0.2, 0.6∫0.3, 0.3∫0.1 (pϽ0.001); Bacteroides forsythus 2.0∫0.6, 0.4∫0.1, 0.4∫0.2, 0.1∫0.2 (pϽ0.001); Treponema denticola 3.4∫1.1, 0.8∫0.3, 0.4∫0.2, 0.3∫0.3 (pϽ0.01). Similar reductions were seen in supragingival plaque samples. While counts were markedly reduced by professional plaque removal, the proportion and prevalence of the 40 test species were marginally affected