Metronidazole alone or with amoxicillin as adjuncts to non-surgical treatment of chronic periodontitis: a 1-year double-blinded, placebo-controlled, randomized clinical trial.

Aim: To evaluate the effects of the adjunctive use of metronidazole (MTZ) or MTZ + amoxicillin (AMX) in the treatment of generalized chronic periodontitis (ChP). A secondary aim was to examine a possible added effect of chlorhexidine to these therapies.

Methods: One hundred and eighteen subjects received scaling and root planing (SRP) only or with MTZ [400 mg/thrice a day (TID)] or MTZ+AMX (500 mg/TID) for 14 days. Half of the subjects in each group rinsed with 0.12% chlorhexidine twice a day (BID) for 2 months. Subjects were clinically monitored at baseline, 3, 6 and 12-months post-therapy.

Results: The two antibiotic groups showed lower mean number of sites with probing depth (PD) ≥5 mm and fewer subjects exhibiting ≥9 of these sites at 1-year post-treatment. Logistic regression analysis showed that antibiotics were the only significant predictors of subjects presenting ≤4 sites with PD ≥5 mm at 1 year (MTZ+AMX: OR, 13.33; 95%CI, 3.75-47.39/p = 0.0000; MTZ: OR, 7.26; 95%CI, 2.26-23.30/p = 0.0004). The frequency of adverse events did not differ between the two antibiotic treatments (p > 0.05). The chlorhexidine subgroups showed a trend (p > 0.05) to present fewer residual sites ≥5 mm compared with the placebo subgroups at 1 year.

Conclusion: Treatment of generalized ChP is significantly improved by the adjunctive use of MTZ+AMX and MTZ.