Non-surgical periodontal treatment with and without adjunctive metronidazole in smokers and non-smokers

Aim: To determine whether adjunctive metronidazole therapy would compensate for the poorer treatment response to scaling and root planing reported in smokers. Method: A single-blind, randomised clinical trial of 28 smokers and 56 non-smokers, stratified for periodontitis disease severity and randomly allocated to 3 treatment groups: (1) Scaling and root planing using an ultrasonic scaler with local anaesthesia (SRP), (2) SRP+metronidazole tabs 200 mg tds for 7 days, (3) SRP+2 subgingival applications of 25% metronidazole gel. Probing depths (PD) and attachment levels (AL) were recorded with a Florida probe at baseline, 2 months and 6 months post treatment by a single examiner who was unaware of the treatment modality. Results were analysed for all sites with baseline probing depths equal to or grater than Florida probe recordings of 4.6 mm using analysis of variance. Results: Reductions in probing depth at 6 months were significantly less (p<0.001) in the smokers (mean 1.23 mm, 95% confidence intervals = 1.05 to 1.40 mm) than in the non-smokers (1.92, 1.75 to 2.09 mm). Attachment level gains were approximately 0.55 mm and there was no statistically significant difference between smokers and non-smokers. There were no differences in any clinical measure in response to the three treatment regimens at 2 or 6 months for either smokers or non-smokers. A reduction in the proportion of spirochaetes was observed at 6 months which was less in smokers than in nonsmokers (p=0.034). Multiple linear regression analysis on probing depth at 6 months demonstrated that smoking was a significant explanatory factor (p<0.001) for poor treatment outcome, whilst the presence or absence of adjunctive metronidazole was not (p=0.620). Conclusion. This study confirms that smokers have a poorer treatment response to SRP, regardless of the application of either systemic or locally applied adjunctive metronidazole.