Data sources: Medline, Embase, the Cochrane Central Register of Controlled Trials (CENTRAL) and hand searching of the journals; Community Dentistry and Oral Epidemiology, Gerodontology, Journal of Clinical Periodontology, Journal of Dental Research, Journal of Periodontology, Journal of Periodontal Research, Journal of Public Health Dentistry and Oral Diseases. Any potential studies in the reference lists of the identified articles read completely were also considered.
Study selection: Studies published in English investigating associations between smoking and tooth loss and reporting the effect size were included. Literature reviews and studies that combined former smokers with non-smokers or current smokers were excluded.
Data extraction and synthesis: Data were extracted by one reviewer and verified independently by another with disagreements being resolved by discussion. Methodological quality of studies was assessed using the modified Newcastle-Ottawa Scale (NOS). A qualitative summary is presented.
Results: Six cross-sectional and two cohort studies were included examining 58,755 subjects in four countries. All studies reported significant associations, although the strength of the association was usually moderate. Four studies reported dose-response relationships between exposure to smoking and the risk of developing tooth loss. A decrease in the risk of tooth loss for former smokers was evident in six studies. Interpretation of evidence for each element was consistent, despite some shortcomings regarding study type and population.
Conclusions: Based on the consistent evidence found with the existing biological plausibility, a causal association between smoking and tooth loss is highly likely. Further studies using a cohort design and different populations are necessary to confirm this association.