Background Periodontitis is an inflammatory reaction in the tissue constituting the attachment between the tooth and the jawbone, and the condition may cause tooth decay. In Norway, many patients are diagnosed with periodontitis every year. Established periodontitis can be treated by the dentist and usually includes scaling and root planing (SRP), surgical flap procedures, gingivectomy, antibiotics or combinations of these procedures. In the present systematic review the patient's smoking status is evaluated against the outcome following professional periodontitis treatment.

Methods A systematic search for relevant literature was performed in Medline, Embase, Svemed and Cochrane Library (central and crd). The relevance of the identified literature was established by evaluation against predefined inclusion and exclusion criteria. The results of the relevant research articles were summarized in tables, described in the text, and also in meta-analysis where this was appropriate

Results A total of 38 relevant research papers were identified by the systematic literature search. Tooth loss among patients undergoing periodontal therapy was reported in one of the included studies, and showed a statistically insignificant trend towards increased risk of tooth loss in the smoker group (Odds Ratio 2.27; 95% Confidence Interval 0.86 to 5.94).

Post-therapeutic changes in pocket depth and clinical attachment level were reported in 35 and 32 studies, respectively. The reported results were heterogeneous, but some sources to heterogeneity were identified by the meta-analysis, for example differences in treatment procedure, pre-therapeutic pocket depth and smoker definition. Additionally, the precision of the effect estimate is significantly impaired by the large methodical uncertainties associated with the use of periodontal probes. The total MD (Mean Difference) effect estimate and 95% CI (Confidence Interval) indicated that non-smokers may show better effect of periodontal therapy than smokers. This was evident both when pocket depths (MD 0.33; 95% CI 0.22 to 0.43 mm) and clinical attachment levels (MD 0.30; 95% CI 0.19 to 0.41 mm) were taken into account. The biggest difference in treatment efficacy between smokers and non-smokers was evident when pre-therapeutic pocket depths were large (> 7 mm) (Pocket Depth: (MD 0.87; 95% CI 0.49 to 1.24 mm); attachment level: (MD 0.75; 95% CI 0.33 to 1.18 mm)).

Post-therapeutic change in pocket depth for ex-smokers and never-smokers were reported in five studies, and the results could be taken to show that the effect of periodontal treatment was almost equal for these two groups (MD 0.07; 95% CI -0.09 to 0.23 mm).

Six studies reported changes in radiological attachment as separate outcome. All tended to show improved treatment effect in the non-smoker groups, but the differences were not statistically significant.

Conclusion Compared to non-smokers, smokers may probably show poorer post-theraputic prognosis following periodontal treatment. Treatment efficacy among ex-smokers and never-smokers seem to be comparable.