Simple bacteriological methods to assess changes in subgingival microflora produced by metronidazole-containing acrylic strips placed into periodontal pockets.

Dark field microscopy is perhaps the simplest microbiological technique to monitor the effects of treatment methods on bacterial plaque. However, the method provides qualitative rather than true quantitative data. This study attempts to measure changes in flora by a number of methods following the placement of 40% metronidazole acrylic strips into periodontal pockets. 10 patients with periodontal pockets greater than 6 mm which bled on probing had acrylic strips placed for 2 to 3 days. Prior to insertion and after removal, subgingival plaque samples were collected into 1 ml of saline and processed as follows. (a) Dark field microscopy for qualitative shifts. (b) Gram stain for differential counts. (c) Counting chamber for total counts. (d) Serial dilution and culture for total cultivable counts. After treatment the significant changes were as follows. (a) % increase in cocci and decreases in other forms, particularly motile organisms. (b) Gram-positive cocci increased and Gram-negative bacilli decreased. (c) Total counts obtained by the sampling method decreased greater than 80%. (d) Total cultivable counts decreased greater than 75%. (e) The efficiency of culturing appeared low and the potential problems of sampling to quantification were identified. The consistency of the changes produced suggested that using simple bacteriological techniques it was possible to show marked changes in the numbers and types of organism present in subgingival plaque following the use of local antimicrobial therapy.