Clinical and microbiological benefits of systemic metronidazole and amoxicillin in the treatment of smokers with chronic periodontitis: a randomized placebo-controlled study

J Clin Periodontol. 2008 Oct;35(10):885-96. doi: 10.1111/j.1600-051X.2008.01304.x. Epub 2008 Aug 24.


Aim: The aim of this study was to evaluate the clinical and microbiological effects of scaling and root planing (SRP) alone or combined with metronidazole (MTZ) or with MTZ and amoxicillin (AMX) in the treatment of smokers with chronic periodontitis.

Methods: A double-blind, placebo-controlled, randomized clinical trial was conducted in 43 subjects who received SRP alone (n=15) or combined with MTZ (400 mg 3 x per day, n=14) or with MTZ+AMX (500 mg 3 x per day, n=14) for 14 days. Clinical and microbiological examinations were performed at baseline and 3 months post-therapy. Subgingival samples were analysed by checkerboard DNA-DNA hybridization.

Results: Subjects receiving MTZ+AMX showed the greatest improvements in mean probing depth and clinical attachment level. Both antibiotic therapies led to additional clinical benefits over SRP alone in initially shallow, intermediate, and deep sites. The SRP+MTZ+AMX therapy led to the most beneficial changes in the subgingival microbial profile. These subjects showed significant reductions in the mean counts and proportions of periodontal pathogens such as Tannerella forsythia, Porphyromonas gingivalis and Treponema denticola, and the greatest increase in proportions of host-compatible species.

Conclusion: Significant advantages are observed when systemic antibiotics are combined with SRP in the treatment of smokers with chronic periodontitis. The greatest benefits in clinical and microbiological parameters are achieved with the use of SRP+MTZ+AMX.

Publication types

  • Randomized Controlled Trial
  • Research Support, N.I.H., Extramural

MeSH terms

  • Adult
  • Amoxicillin / therapeutic use*
  • Anti-Infective Agents / therapeutic use*
  • Bacteria / classification
  • Bacteria / drug effects
  • Chronic Periodontitis / etiology
  • Chronic Periodontitis / microbiology
  • Chronic Periodontitis / therapy*
  • Colony Count, Microbial
  • Combined Modality Therapy
  • Dental Deposits / drug therapy
  • Dental Deposits / microbiology
  • Dental Scaling*
  • Double-Blind Method
  • Drug Therapy, Combination
  • Female
  • Follow-Up Studies
  • Humans
  • Male
  • Metronidazole / therapeutic use*
  • Middle Aged
  • Periodontal Index
  • Smoking / adverse effects*
  • Treatment Outcome


  • Anti-Infective Agents
  • Metronidazole
  • Amoxicillin