Current smokers on HRT, however, received none of estrogen's benefits, indicating smoking negates estrogen's protective effects.

The results are from two studies-one assessing jaw bone loss; the other, tooth loss-conducted by the UB Periodontal Disease Research Center. They were presented March 14 at the annual meeting of the International Association for Dental Research in San Francisco.

"We know estrogen has a bone-sparing effect in the skeleton," said Sara G. Grossi, UB clinical assistant professor of oral biology and clinical director of the Periodontal Disease Research Center. "We wanted to determine if it had the same effect on the bone around the teeth, the bone loss associated with gum disease. We found that women who took estrogen had significantly less bone loss and they also lost fewer teeth.

"The protective effect of estrogen on the teeth is an important observation," Grossi added, "because we accounted for all other factors that could contribute to loss of bone around the teeth and tooth loss."

Results showed that among never-smokers, postmenopausal women on HRT had significantly less tooth loss than postmenopausal women not on HRT.

"This tells us that estrogen supplementation improves oral health in older women and allows them to keep their teeth longer, therefore improving their overall quality of life," she noted.

The researchers don't know precisely how smoking negates estrogen's protective effects, Grossi said, but she speculates that it could be in one of two ways: by preventing estrogen from being used by the body or by the action of smoking on the bone itself.

"We know that smoking is a risk factor for bone loss," she said. "Maybe the effects of estrogen aren't enough to overcome it. It's one more reason why women shouldn't smoke."

Presenting the results in San Francisco were Nada El-Ghorab, a postdoctoral fellow from Egypt, and Carlos Ferreira, a postdoctoral fellow from Brazil.