Topical metronidazole application in recall patients. Long-term results

The aim of this randomised study in split-mouth design, in which 24 patients from the recall programme of Marburg University Department of Periodontology were enrolled, was to compare topical application of a metronidazole 25% dental gel with subgingival scaling. The clinical parameters used were pocket probing depth (PPD) and bleeding on probing (BOP); these were recorded at baseline and 1, 3, 6, 14, 18 and 24 months after completion of treatment. In addition, plaque samples were taken from all mesial pockets for evaluation by dark-field microscopy. All patients had at least one tooth in each quadrant with a PPD of 5 mm or more showing BOP when they entered the study. The treatment consisted of 2 applications of dental gel in 2 randomly selected quadrants (on days 0 and 7) as well as subgingival scaling of the remaining quadrants. Statistical evaluation of all sites with a baseline PPD of 5 mm or more showed that both methods led to a significant reduction in PPD and BOP in the first 6 months. The average reduction in PPD was 1.3 mm in the gel group and 1.5 mm in the scaling group, with the tendency to bleeding being reduced by ca. 50% in both groups. After 24 months, improvements of 0.6 mm and 0.5 mm respectively were observed in PPD. The tendency to bleeding had undergone a slight increase but was still below baseline values. No statistically significant differences were observed between the two methods, although the results recorded with subgingival scaling were slightly better. Dark-field microscopy revealed a shift in the composition of the bacterial flora, suggesting a more physiological situation, which was maintained for 6 months before reverting consistently after 18 months to the baseline values of the plaque composition. Overall, application of a metronidazole 25% dental gel led in recall patients to an improvement in the investigated clinical and microbiological parameters comparable with subgingival scaling. After 24 months, the clinical parameters still displayed a very slight improvement over baseline values; after 18 months the microflora had reverted to its baseline composition.