Repeated metronidazole and amoxicillin treatment of periodontitis. A follow-up study

Background: The prevailing concept is that little or no clear benefit is derived from antibiotic therapy in chronic periodontitis. Studies to determine the effect of metronidazole plus amoxicillin (M+A) on adult periodontitis are questionable because standard design for clinical trials was usually not used. In addition, there is no information about the effect of M+A as the sole therapy for periodontitis. Methods: A randomized, triple-blind, controlled clinical trial was used to determine the effect of systemic administration of M+A, as the sole therapy, in progressive adult periodontitis. Forty-six subjects with moderate to advanced adult periodontitis who showed greater than or equal to 2 mm attachment loss in at least 2 sites in the previous 2 months were entered in the study. Subjects were randomly distributed to a group who received 21 tablets of metronidazole 250 mg plus amoxicillin 500 mg, or to a group receiving a placebo (1 tablet every 8 hours for 1 week). Patients were examined every 2 months for 12 months. The M+A or placebo regimen was repeated at 4 and 8 months. No effort was made to change the oral habits of patients and they received no additional therapy. Differences between groups were assessed using the Mann-Whitney U test. The differences at every 2-month interval within each group were assessed using the ANOVA test. Results: Seven subjects abandoned the study; at 12 months the M+A group had 20 subjects and the placebo group 19. There were no significant differences in the clinical parameters at baseline between the 2 groups. After 2 months and thereafter, the M+A group showed significant clinical improvement while the placebo group showed a progressive deterioration of periodontal status. At 12 months compared to baseline, subjects of the M+A group showed: 1) a significant overall mean attachment gain of 0.43 mm (P = 0.005); 2) a significant decrease of active sites (P less than or equal to 0.03); 3) a significant increase of sites gaining attachment level (P less than or equal to 0.01); 4) a significant reduction of pocket depth (P less than or equal to 0.00006); and 5) a significant decrease in percentage of bleeding on probing sites (BOP) (P less than or equal to 0.0005). Significant differences between both groups at all 2-month evaluations were found in overall mean attachment level (P less than or equal to 0.000004), in percent of active sites (P less than or equal to 0.03), and in percent of BOP sites (P less than or equal to 0.02). Sites exhibiting greater than or equal to 2 mm of attachment loss in 2 successive or alternate evaluations, and periodontal abscess were noticed only in the placebo group. Conclusions: A 1-week course of systemic M+A every 4 months, as the only therapy, arrest the progression of adult periodontitis and significantly improves the clinical parameters of the disease.