Trail shows improved outcomes with metronidazole alone or with amoxicillin as adjuncts to non-surgical treatment of chronic periodontitis


The main aim of this study was to evaluate the effects of the adjunctive use of metronidazole (MTZ) or MTZ + amoxicillin (AMX) in the treatment of generalized chronic periodontitis (ChP).

Participants with untreated generalized ChP were randomised to receive either scaling and root planning (SRP) only (n= 40); SRP with MTZ, 400 mg/3 times a day (n= 39); SRP or with MTZ+AMX, 500 mg/3 times a day (n= 39); Antibiotics were prescribed for 14 days.  Patients ≥30 years of age and a minimum of 6 teeth with at least one site each with probing depth (PD) and clinical attachment level (CAL) ≥5 mm, as well as at least 30% of the sites with PD and CAL ≥4 mm and bleeding on probing (BOP) were included.  Those having had previous subgingival periodontal treatment, smokers, relevant systemic diseases and allergies to MTZ, AMX or CHX were excluded. All subjects received clinical monitoring at baseline, 3 and 6 months and 1-year post-therapies. In addition, all subjects received periodontal maintenance at the three post-treatment monitoring visits. The main outcome the difference among groups for the mean number of residual pockets with PD ≥5 mm post-treatment.

  • Of the 118 patients randomised, 17 were lost to follow up (SRP group = 6; MTZ group =6;MTZ+AMX group =5).
  • Three adverse events were reported in the SRP group; 8 in the MTZ group and 7 in the MTZ+AMX group.
  • All three main therapies were effective in reducing the number/percentage of sites with PD ≥5 mm with BOP during the course of the study (p < 0.05)
  • Fewer subjects in the MTZ (n = 11), and in the MTZ + AMX (n = 9) groups still had “high risk” for disease progression at 1 year (i.e. ≥9 sites with PD ≥5 mm), in comparison with the SRP-only group (n = 25)

The authors concluded

Treatment of generalized ChP was significantly improved by the adjunctive use of MTZ + AMX and MTZ.


Previously we have noted systematic reviews that have suggested enhanced benefits of using systemic antimicrobials as a adjunct to SRP (Dental Elf May 25th)


Feres M, Soares GM, Mendes JA, Silva MP, Faveri M, Teles R, Socransky SS, Figueiredo LC. Metronidazole alone or with amoxicillin as adjuncts to non-surgical treatment of chronic periodontitis: a 1-year double-blinded, placebo-controlled, randomized clinical trial. J Clin Periodontol. 2012 Aug 16. doi: 10.1111/jcpe.12004. [Epub ahead of print] PubMed PMID: 23016867

Dental Elf 25th May 2012



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Derek Richards

Derek Richards is a specialist in dental public health, Director of the Centre for Evidence-Based Dentistry and Specialist Advisor to the Scottish Dental Clinical Effectiveness Programme (SDCEP) Development Team. A former editor of the Evidence-Based Dentistry Journal and chief blogger for the Dental Elf website until December 2023. Derek has been involved with a wide range of evidence-based initiatives both nationally and internationally since 1994. Derek retired from the NHS in 2019 remaining as a part-time senior lecturer at Dundee Dental School until the end of 2023.

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