Smoking is not only bad for your health, it's bad for your teeth: researchers say that male smokers require root-canal surgery at twice the rate of nonsmokers, Medpage Today reported Feb. 23.

A three-decade-long study found that men who smoked for the longest period of time were most likely to need root canal, while those who quit lowered their risk. The risk of root canal was found with cigarette smoking, but not cigar or pipe smoking, even though the latter have long been associated with periodontal disease and tooth loss.

The research will be published online in April 2006 in the Journal of Dental Research.