Clinical and microbiological benefits of metronidazole alone or with amoxicillin as adjuncts in the treatment of chronic periodontitis: a randomized placebo-controlled 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). Materials and methods: Fifty-one subjects (n = 17/group) were randomly assigned to receive scaling and root planing (SRP) only or combined with MTZ (400 mg t.i.d.) or MTZ + AMX (500 mg t.i.d.) for 14 days. Clinical and microbiological examinations were performed at baseline and 3 months post-SRP. Nine plaque samples/subject were analysed by checkerboard DNA-DNA hybridization for 40 bacterial species. Results: Subjects receiving MTZ + AMX exhibited a greater mean gain of clinical attachment, reduction in probing depth (PD) in intermediate and deep sites and a lower percentage of sites with PD >= 5 mm at 3 months, in comparison with those treated with SRP only (p < 0.05). The major benefit from the adjunctive use of MTZ was a greater reduction in PD in deep sites. SRP + MTZ + AMX was the only treatment that significantly reduced the levels and proportions of all red complex pathogens and elicited a significantly greater beneficial change in the microbial profile in comparison with SRP only. Conclusion: The adjunctive use of MTZ + AMX offers short-term clinical and microbiological benefits, over SRP alone, in the treatment of non-smokers subjects with generalized ChP. The added benefits of MTZ were less evident.