Effects of metronidazole plus amoxicillin as the only therapy on the microbiological and clinical parameters of untreated chronic periodontitis

Aim: To determine the effect of metronidazole plus amoxicillin (M+A) as the sole therapy, on the subgingival microbiota of chronic periodontitis. Material and Methods: Twenty-two patients with untreated chronic periodontitis were randomly assigned to a group that received M+A for 7 days, or to a group receiving scaling and root planing (SRP) and two placebos. Clinical measurements including sites with plaque, bleeding on probing (BOP), probing depth (PD) and attachment level (AL) were made at baseline, 3, 6, 9 and 12 months. Subgingival plaque samples were taken from all teeth at baseline 3, 6, 9 and 12 months for the counts of 40 subgingival species using checkerboard DNA-DNA hybridization. Results: Mean PD was reduced from 2.80 +/- 0.45 at baseline to 1.95 +/- 0.05 at 12 months (P < 0.001) and from 2.39 +/- 0.41 to 1.95 +/- 0.10 (P < 0.001) in the M+A- and SRP-treated patients, respectively. Corresponding values for relative mean AL were 10.07 +/- 1.30-9.77 +/- 0.34 (P < 0.001) and 9.94 +/- 0.28-9.77 +/- 0.26 (P < 0.001). Percentage of sites exhibiting BOP were 40.6 +/- 18.3-14.0 +/- 1.4 (P < 0.001), and 38.5 +/- 5.1-19.0 +/- 2.8 (P < 0.001) in the M+A and SRP groups, respectively. Mean total DNA probe counts and counts of the majority of the 40 test species were significantly reduced over time in both groups, with no significant differences detected at any time point between groups. At 12 months many of the species were still present at significantly lowered levels compared with their baseline counts in both groups. Conclusions: Changes in clinical and microbiological parameters were similar after receiving systemically administered M+A as the sole therapy or after receiving SRP only.