Microbial and clinical measurements of periodontal pockets during sequential periods of non-treatment, mechanical debridement and metronidazole therapy

Microbial and clinical parameters were studied in 11 subjects with chronic inflammatory periodontitis. 2 periodontal pockets per subject were studied longitudinally. The microbial parameters included counts of different subgingival micro-organisms by dark field microscopy, counts of the total colony forming units (c.f.u.) on anaerobic blood agar, the facultative anaerobic counts and counts of black-pigmented Bacteroides, Fusobacterium and E. corrodens. The clinical parameters were probing pocket depth, bleeding after probing and crevicular fluid production. Clinical and microbial observations were compared during 3 consecutive periods of non-treatment, debridement and metronidazole therapy. The experimental sites were debrided by deep scaling while no debridement was carried out at the control sites. The effect of this treatment was studied over a period of 3 months. Then, at the experimental sites, a 2nd session of debridement was followed by administration of metronidazole. The effect of metronidazole alone and combined with mechanical debridement was studied during a subsequent 3-month period. The disease activity did not correlate with the microbial parameters and was evident in the presence as well as in the absence of black-pigmented Bacteroides. A single session of subgingival debridement resulted in significant reductions in probing depth, spirochetes, motile organisms, black-pigmented Bacteroides and E. corrodens. Repopulation of the subgingival sites was observed. However, the composition of the subgingival microbiota remained significantly changed during the 3 months after debridement. The re-isolation of the same Bacteroides-species and the same B. gingivalis type after treatment indicated an outgrowth of micro-organisms remaining at these sites.(ABSTRACT TRUNCATED AT 250 WORDS)