So, it does seem that smoking has a positive aspect!

http://www.21stcenturydental.com/smith/education/ulcers.htm

"The aim of this study was to investigate the effect of nicotine, in the form of Nicorette tablets, on aphthous ulcers in nonsmoking patients. The study was prompted by the observations that smokers are less likely to suffer from mouth ulcers, that some smokers on quitting develop them, and that patients on nicotine replacement therapy are less likely to develop ulcers than those having other types of smoking cessation therapy. CLINICAL FEATURES: The three nonsmoking patients who were selected for the study each had a long history of recurrent aphthous ulcers with no remissions. INTERVENTION AND OUTCOME: Each patient was given up to four 2 mg Nicorette chewing tablets per day. After one month of this regimen each patient was weaned off the tablets. In each case the ulcers healed and new ulcers did not appear during Nicorette therapy. Two of the patients relapsed when weaned off the tablets. CONCLUSIONS: This preliminary trial shows that nicotine may have a beneficial effect on aphthous ulcers. Further studies are necessary to elucidate the mechanism."