Metronidazole and amoxicillin for patients with periodontitis and diabetes mellitus: 5 years secondary analysis of a randomized controlled trial

Background The aim of this study was to perform a 5-year follow-up analysis of a previously-published randomized trial (RCT) evaluating the 2-years effects of metronidazole (MTZ) plus amoxicillin (AMX) as adjuncts to scaling and root planing (SRP) in the treatment of periodontitis in type 2 diabetic patients. Methods Volunteers who received periodontal treatment in the aforementioned RCT were selected for clinical and microbiological evaluation. Patients did not receive regular supportive periodontal therapy (SPT) from 2 to 5 years post-treatment. Results Of the patients enrolled in the RCT, 43% entered this study (n = 10/control and 15/test group). Most of clinical parameter values, including the number of sites with probing depth >= 5 mm (primary outcome variable), were reduced at 5 years post-therapy when compared with baseline in the antibiotic-treated group (P < 0.05), but presented higher values than those at 2 years (P < 0.05). The mean proportions of microbial complexes did not differ between MTZ+AMX+SRP and SRP-only groups at 5 years post-treatment (P > 0.05). Conclusion Diabetic patients treated with adjunctive MTZ+AMX were better maintained over a period of 5 years than those treated with SRP only. However, the clinical and microbiological benefits obtained up to 2 years post-treatment were not fully sustained in these patients who did not receive SPT between 2 and 5 years post-treatment.