The microbial outcome observed with polymerase chain reaction in subjects with recurrent periodontal disease following local treatment with 25% metronidazole gel.

The aim of this study was to evaluate the microbial outcome in patients with recurrent periodontal disease following treatment with 25% metronidazole gel using the polymerase chain reaction (PCR). 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 > or = 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 analysed and detected with PCR:Actinobacillus actinomycetemcomitans (A.a.), Porphyromonas gingivalis (P.g.) and Prevotella nigrescens (P.n.). At baseline, A.a., P.g. and P.n. were detected in 30, 60 and 70% of all test sites and in 32, 58 and 21% of all 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. However, there were no statistically significant differences in the occurrence rate of A.a., P.g. and P.n. at test and control sites after treatment. This study has shown that 25% metronidazole gel treatment did not seem to influence the microbial outcome, when PCR was used to analyse the presence/absence of A.a., P.g. and P.n. in this group of subjects with recurrent periodontal disease.