Fri, 24 Feb 2006 12:00 CST
New York - Men who smoke cigarettes are about twice as likely to require root canal treatment as those who have never smoked, according to a prospective cohort study lasting for almost three decades.
The risk for cigarette smokers increased with more years of smoking and decreased with length of abstinence, suggesting a dose-response relationship.
Cigar and pipe smoking, although linked to periodontal disease and tooth loss, was not significantly associated with root canal treatment, according to an online report to be published in the April issue of the Journal of Dental Research. The research was also presented today at a press briefing here sponsored by the American Medical Association and the American Dental Association.
The study included 811 dentate men in the VA Dental Longitudinal Study who were followed from two to 28 years. The men, ages 21 to 84 years, were not VA patients and received dental and medical care from the private sector. This may be the first longitudinal analysis of smoking as a risk factor for root canal treatment, said a team headed by Elizabeth Krall, Ph.D., M.P.H., of Boston University Goldman School of Dental Medicine here.
Incident root canal treatments occurred in 985 teeth among 385 subjects. The risks attributable to cigarette smoking remained statistically significant even after controlling for number of teeth affected, percentage with crowns, coronal caries, and 20% or greater alveolar bone loss. The results also held when education and brushing and flossing were included, the researchers reported.
Multivariate analyses of root canal risk at the individual tooth level yielded almost twice the risk (HR 1.9) for current cigarette use (95% CI 1.4 to 2.5). However, for current cigar and pipe smokers, the 1.3 risk was similar to that of never-smokers (95% CI 0.9 to 1.7).
Length of time spent smoking made a difference. For men who had quit smoking nine or fewer years before baseline, the risk was still almost twice as high as that for the never-smokers (HR 1.9; 95% CI=1.3 to 2.8). But among men who had quit more than nine years previously, the risks were similar to never smokers.
Among current cigarette smokers, the risks increased with length of smoking from 1.2 times greater (HR 1.2, CI=0.7 to 1.9) for smoking four or fewer years, to twice the risk (HR 2.0, CI 1.2 to 3.3) for smoking five to 12 years, and a 2.2 times greater risk (HR 2.2 CI 1.5 to 3.3) for those who smoked for more than 12 years, the researchers reported.
Smoking impairs the body's response to infection, exacerbates bone loss throughout the skeleton, induces a chronic systemic inflammatory response, and causes vascular problems, the researchers said. Any of these pathways can potentially affect the health of the tooth pulp and surrounding bone tissue. Once bacterial infection begins in the pulp and surrounding tissue, Dr. Krall said, smokers have difficulty limiting the destruction.
The study had certain limitations, she noted. Although cigar and pipe use were not related to root canal treatment in this study, periodontal disease and tooth loss were significant. It is possible that the small number of pipe/cigar smokers and the difficulty of quantifying the amount smoked may have accounted for the lack of root canal findings, she said. Risk estimates suggest a threshold effect for cigarette smokers around five years' exposure, but since cigar smokers tend to start the habit later, their tobacco exposure may be limited.
Another limitation of the study is the small (5%) number of minority subjects and the lack of women. We would expect to see the smoking and root-canal risk in women and other ethnic groups, Dr. Krall said, although absolute risk may differ and be more closely related to cigarette exposure than to demographic characteristics.
At the beginning of this article, there are some "Medpage Today Action Points":
* Explain to patients that even though this study was limited to men, similar risks are likely for women, including those exposed to second-hand smoke.
* When talking with pipe and cigar smokers, suggest that despite the limited findings in this study that show no increased risk in these patients, they may still be at risk for root canal treatment along with other periodontal risks.
As a public service to our cherished readers, we thought we would add the following "warnings":
* When talking with anyone at all, be sure to warn them that smoking is also the cause of every other major and minor illness that has ever existed and that will ever exist.
* If they object to any of your statements - which are based on studies with extraordinarily small and exclusive groups, and then later generalized to encompass the entire world - tell them that it is your expert opinion that none of the other three million different cancerous chemicals that they ingest each day has anything to do with the illnesses for which everyone blames smoking. If you own stock in a company that makes non-stick frying pans, be sure to mention that Teflon is mostly certainly not a carcinogen, and that you even recommend Teflon-coated pacifiers for babies.
* As always, push as many pharmaceuticals as you can so that you can get some nice kickbacks from your "retirement plan", aka Big Pharma.