Topical metronidazole application as an adjunct to scaling and root planing

Aim: This study was carried out to investigate the effect of 2 applications of a metronidazole 25% dental gel as adjunctive therapy to subgingival scaling with root planing. Method: 59 of the original collective of 64 patients with adult periodontitis were observed for a 9-month period. This randomised single-blind study was carried out in split-mouth design. Each patient had to have at least 2 pockets with a probing depth of greater than or equal to 5 mm in each quadrant. The clinical parameters, pocket probing depth (PPD), attachment level (AL) and bleeding on probing (BOP), were recorded at all teeth on days 0, 91, 175 and 259; in addition, subgingival plaque samples taken from 45 patients were analysed by means of dark-field microscopy. Therapy comprised subgingival scaling and root planing (SRP) of all quadrants and additional application of metronidazole 25% dental gel in 2 randomly selected quadrants (SRP+Metro). Treatment was confined to teeth with a baseline PPD of greater than or equal to 5 mm. Average PPD and AL and the incidence of BOP were computed for all pockets with a baseline PPD of greater than or equal to 5 mm, and the 2 methods compared. The main efficacy variable for evaluation of the 2 treatments was the difference in PPD on day 259. Results: Comparison of the 2 treatments revealed a statistically significant improvement in the clinical parameters for both treatment methods over the study period. Between baseline and day 259, significant differences in PPD (SRP+Metro: from 6.00 to 4.63 mm, SRP: from 6.02 to 4.83 mm) and BOP (SRP+Metro: from 67 to 31%, SRP: from 64 to 36%) were observed between the 2 treatment groups. Evaluation according to different patient groups demonstrated significant advantages of the combined therapy in previously-untreated patients, especially in female probands. Dark-field microscopy revealed a shift in the bacterial flora towards healthy conditions. Conclusions: The results show that only minor advantages are to be gained from the application of a metronidazole 25% dental gel as adjunctive therapy to subgingival scaling. The distinctly better results of combined therapy in previously-untreated patients calls for more thorough investigation.