Can smoking cessation impact the incidence and progression of periodontitis?

Aim The aim of this systematic review was to assess the effect of smoking cessation on the incidence and progression of periodontitis, and to evaluate the effect of cessation on periodontal treatment outcomes.Data sources Both prospective observational and interventional studies that evaluated the effect of smoking cessation on incidence and progression on periodontitis were included for the review. Different electronic databases, including PubMed, Embase and Scopus, were used for finding the relevant literature. In addition to this, hand-searching of the included articles and Google Scholar searches were also conducted to look for missing grey literature.Study selection A thorough search from the literature, done using a pre-defined search strategy, yielded a total of 2,743 studies. After de-duplication and excluding the irrelevant articles, a total of eight observational and two interventional studies were included in the review.Data extraction and synthesis Two authors independently extracted the data from the included studies. Data like basic study characteristics (for example, author names, country of study, follow-up time) and other parameters like smoking behaviour and periodontal outcome measures were extracted from the included studies. Meta-analysis was carried out to find the impact of smoking cessation on the risk of periodontitis, while comparing the effect among quitters vs never-smokers, quitters vs continuing smokers and never-smokers vs continuing smokers.Results Six out of eight observational studies were included in the meta-analysis and the results of the meta-analysis were depicted using forest plots. The pooled risk ratio for the three different comparisons were: quitters vs never-smokers RR = 0.97 (CI = 0.87-1.08); continuing smokers vs quitters RR = 1.79 (CI = 1.36-2.35); and continuing smokers vs never-smokers RR = 1.82 (CI = 1.43-2.31). Two interventional studies included showed 0.2 mm higher gain in attachment level (CAL gain) and 0.32 mm reduction in periodontal pocket depth (PPD) among quitters over non-quitters over a period of 12-24 months.Conclusions Non-significant difference in the incidence and progression of periodontitis was observed between quitters and never-smokers, while significantly higher risk of periodontitis was observed among the continuing smokers cohort as compared to quitters or never-smokers.