Sufficient evidence has accumulated to conclude that smoking is a causal factor in cardiovascular diseases, certain types of cancer, chronic obstructive lung diseases, infertility, cataracts, hip fractures, and periodontal diseases (29
). Risks of some of these diseases decline when the causal factor is removed through smoking cessation (30
). Research suggests smoking also may be causally linked to tooth loss (8
), but there is little information on the effect of smoking cessation on tooth loss risk.
A previous analysis of DLS participants found that the rate of tooth loss among men who quit smoking was about 50% lower than the rate among current smokers but still significantly higher than the rate among nonsmokers (8
). However, that analysis did not address how risk might change with increasing length of abstinence. In a 12-year follow-up study of 1031 Swedish women, prospective rates of tooth loss were similar in never smokers and former smokers who had abstained from smoking an average of 10 years before entering the study (13
). These findings are consistent with the arrested progression of periodontal bone loss and attachment loss observed when individuals quit smoking (31
The results of this study suggest that tooth loss risk does decline after smoking cessation but that the risk remains elevated in relation to nonsmokers for at least 9 years. Why should the risk of tooth loss decline as men remain abstinent from cigarettes, and why does it seem to take about a decade or more to return to the level of never-smokers? The loss of alveolar bone is not reversible, so one might expect the cumulative damage to the bone tissue by cigarettes to keep the risk of tooth loss permanently elevated. But periodontal disease is often localized around a few teeth, as demonstrated by the small number of teeth with moderate alveolar bone loss and probing pocket depths in this cohort, and progresses intermittently. Removing exposure to smoke reduces the likelihood that disease will become widespread and affect many teeth. In addition, smoking is one of several risk factors for periodontal disease. Age, genetic susceptibility, and systemic diseases such as diabetes all influence the disease risk. It may be that as time elapses, these other risk factors become more important and begin to obscure the differences due to past smoking. Finally, there are other lifestyle changes that may occur when an individual decides to quit smoking and may become more established as the duration of abstinence increases. Smokers who quit appear to be more health conscious than those who continue to smoke, and they make physician visits and use health screening programs at rates comparable to those of nonsmokers (34
). Former smokers in the DLS were more likely than current smokers to have had a dental prophylaxis in the past year (8
), a practice that should promote tooth retention rather than tooth loss.
The risk of tooth loss in quitters was not significantly different from that in never smokers more than 9 years after cessation and remained consistently near 1.0 after 13 years. The length of time needed to lower the risk to the level of never smokers could not be determined more accurately in our subject population. The number of subjects decreased, and the confidence intervals widened, as the baseline used to compute tooth survival was moved forward to account for increasing periods of abstinence. Nevertheless, the data suggest that the length of time after smoking cessation needed to significantly lower risk is not so long as to be unattainable yet requires long-term commitment to avoid smoking relapse.
This study has several limitations that could affect our estimates of tooth loss risks and of when the risk for quitters reaches the level of never smokers. Information on the causes of tooth loss was not obtained. We assume that teeth were lost primarily because of periodontal disease or caries, but it is possible that some teeth were extracted for other reasons unrelated to these diseases. There may have been confounding by education, socioeconomic status, and dental insurance coverage that we could not control for adequately. Although we had some information on these measures, it was not necessarily complete. Education was recorded as a nine-level categorical variable rather than years completed. Socioeconomic status (income) was assessed only at the study baseline and was not updated during follow-up, even though the employment status of the men changed. Dental insurance information was not obtained until almost 20 years had elapsed since baseline and therefore was missing for the 40% of the cohort that had dropped out by this time. It is possible that insurance coverage of smokers who dropped out early was different from that of smokers who remained in the study. In addition, the study included only men and few individuals from minority populations. Therefore, the ability to generalize these results to different populations is limited.
The results of this study suggest that the risk of tooth loss decreases upon smoking cessation, but it may take at least 9 to 12 years of abstinence for the risk to return to the level of never smokers. This information can be used to encourage current smokers to quit and to remain abstinent.