Adjunctive antimicrobial therapy of periodontitis: Long-term effects on disease progression and oral colonization

Background: This study assessed the long-term effects of adjunctive antimicrobial therapy on periodontal disease progression and oral colonization. Methods: Patients with previously untreated chronic periodontitis and subgingival Actinobacillus actinomycetemcomitans and/or Porphyromonas gingivalis were randomly assigned to subgingival scaling without (control group) or with systemic amoxicillin plus metronidazole and CHX irrigation (test group). Relative attachment levels were determined and subgingival and mucosal plaque samples were taken at baseline, at 10 days (plaque only) and at 3, 6, 9, 12, 18, and 24 months following initial therapy. During maintenance therapy, patients received supragingival debridement only. Results: After 24 months, the 18 test group patients showed at sites with initial probing depths (PD) >= 7 mm a significantly (P < 0.05) higher frequency of 2 mm or more attachment gain (37.3% +/- 4.6%) and lower frequency of attachment loss (7.2% +/- 3.1%) compared to the 17 controls (8.2% +/- 3.9% and 19.1% +/- 13.1%, respectively). Compared to controls, the intraoral prevalence of A. actinomycetemcomitans (up to 18 months) and P. gingivalis (up to 3 months) decreased and that of Eikenella corrodens (at 10 days) increased in test patients (P < 0.05). In both treatment groups, the detection frequency of Tannerella forsythensis decreased transiently, while an overall increase was recorded for Treponema ssp. Conclusions: Over the 24-month period, a single course of the administered adjunctive antimicrobial therapy led to a relative risk reduction of 62% for attachment loss at deep sites. However, with the exception of A. actinomycetemcomitans, it failed to induce long-term changes in the prevalence profiles of oral colonization.