Methods: Twenty subjects in a maintenance care program but with recurrent periodontal disease participated. Three months after scaling and root planing a total of 40 sites, 2 in each patient, with pocket probing depth of >5 mm were selected. One site randomly selected was treated with 25% metronidazole gel (test) and the other site with a placebo gel (control). A bacterial sample was collected on paperpoint from each test and control site at baseline and 12 weeks after treatment. The following pathogens were analyzed and detected with PCR: Porphyromonas gingivalis (P.g.), Actinobacillus actinomycetemcomitans (A.a.) and Prevotella nigrescens (P.n.).
Results: At baseline, A.a., P.g. and P.n. were detected at different frequency in all test and control sites. There was a statistically significant difference between the test and control sites for P.n. at baseline. The major difference after treatment with 25% metronidazole gel was the increase of positive control sites for P.g. and P.n. There were no statistically significant differences in the occurrence rate of A.a., P.g. and P.n. between the test and control sites after treatment.
Conclusion: This study has shown that 25% metronidazole gel treatment did not seem to influence the microbial outcome, when PCR was used to analyze the presence/absence of A.a., P.g. and P.n. in this group of subjects with recurrent periodontal disease.