Effect of local metronidazole application on periodontal healing following guided tissue regeneration. Microbiological findings
The purpose of this study was to investigate the effect of local application of a controlled release metronidazole gel on the microflora in the wound following insertion of an e-PTFE membrane and to study the possible association between selected bacterial species and the clinical treatment result. Twelve patients with two periodontal pockets greater than 6 mm and in association with angular bony defects were used in the study. The teeth were randomly assigned to either test or control groups and were treated with an interval of one week. The membranes were placed and metronidazole was injected at the site; the gel was applied along the gingival margin of the test teeth after suturing. The control sites did not receive metronidazole. The patients were told to rinse twice a day with 0.2% chlorhexidine. The patients were examined six days after the procedure, and two and four weeks following surgery. Samples were taken from the pockets. Six weeks after insertion, the membranes were removed and were subjected to microbiological exam. At 18 and 30 weeks both test and control surfaces were examined and microbiological samples were obtained for anaerobic and aerobic counts.
At entry there was no significant difference between the control and the test with regard to the total anaerobic/aerobic counts, ratio, black pigmented Gram-anaerobic rods, P. gingivalis, P. intermedius, A.a., or Staphylococci. Systemic absorption of metronidazole as well as leakage from the test wound to the oral cavity could have influenced the microflora in the control sites as well. A reduction in the median total anaerobic count between the presurgical and the one-week examination from 1.2 x 10(6) to 3.0 x 10(5) in the test group was statistically significant. One week after the membrane placement the control pockets had five times more cultivable bacteria than the test. The control pockets showed higher ratios of aerobic/anaerobic bacteria than the test ones. The surgical treatment reduced the ratios in both, but at the time of membrane removal the ratios were comparable to baseline. There was no difference between both groups regarding black-pigmented bacteroides, Gram- and/or Ala. However, one week after membrane placement, anaerobic rods in the test group were reduced from 58% to 42%, and in the control these proportions increased from 38% to 67%. Presurgery 42% of the patients harbored Ala. and 25% P.g. After surgery this disappeared in the test group; P.g. remained in 8% of the pockets, A.a. in 17%. Median proportion from pre-surgery to one week after surgery showed a decrease in black-pigmented bacteroides to a .004% (test) and an increase of 3.5% in the control. However, this difference was not evident after two weeks. None of the control pockets achieved 100% gain in clinical attachment, whereas half of the test pockets did. In conclusion, although bacterial colonization of the wound was delayed it was not prevented. Metronidazole gel decreased the percentage of bacteria in the test pocket after surgery, returning to baseline one week post-surgery. [c.c.
Frandsen, E., L. Sander, D. Arnbjerg and E. Theilade, J Periodont, 65:921,1994