EFFECT OF LOCAL METRONIDAZOLE APPLICATION ON PERIODONTAL HEALING FOLLOWING GUIDED TISSUE REGENERATION - MICROBIOLOGICAL FINDINGS

THE BACTERIOLOGICAL COLONIZATION OF HEALING periodontal defects was investigated after treatment with guided tissue regeneration using expanded polytetrafluoroethylene membranes together with local metronidazole gel (25%, 250 mg/g). Twelve patients, each with one pair of comparable defects, had the test defect treated with the membrane plus metronidazole gel and the control defect treated with the membrane alone. Thirty weeks after removal of the membrane, the median gain in probing attachment level as a percentage of the initial defect depth was 92% for the test defects and 50% for the control defects (P = 0.001). The median number of cultivable bacteria decreased from 1.2 X 10(6) at the presurgical examination to 3.0 X 10(5) at the one week examination in the test group (P = 0.02), whereas an increase was observed in the control group. Similarly, a lower median proportion of black-pigmented Gram-negative anaerobic rods was observed one week postsurgically in the test group (0.004%) compared to the control group (3.5%) (P = 0.02). Two weeks after membrane insertion, and at all following examinations, no microbiological differences between test and control group were observed. Consequently, the influence of the metronidazole gel on the treatment result appears to have been confined to the initial regeneration phase. Despite the good clinical results in the test group, all membranes from both test and control pockets were heavily colonized with bacteria at the time of removal. To ensure maximal periodontal regeneration with formation of bone, future research in this area should concentrate on reducing the microbial colonization of the wound area.