Researchers at the West Virginia University School of Dentistry say they have uncovered the reason for high rates of tooth loss in two Pennsylvania towns and two West Virginia counties.

Nationwide about 20 percent of Americans have lost their teeth, but in West Virginia, it's 43 percent, researchers say.

About 80 percent of the residents in the study area suffer from more severe forms of periodontal disease, researchers say.

Researchers studied 445 families to reach their conclusions. They also determined that the impact of gum disease doesn't stop with the mouth.

"If a woman is pregnant, she is four to seven times more likely to have a preterm, low birth-weight baby compared to someone who does not have gum disease," Richard Crout, D.M.D., Ph.D., an expert on gum disease and associate dean for research in the West Virginia University School of Dentistry, said in a statement.

Crout said the study convinced him of the general health problems that accompany periodontal disease.

"Leaving periodontal disease untreated is a major public health problem," Crout says. "Not only do we see cases where the inflammatory process has eaten down around the bone, ultimately causing tooth loss in many patients, but also more important the inflammation likely has traveled throughout the body. A person with periodontitis may be twice as likely to have a heart attack and almost three times more likely to have a stroke."

Crout's co-authors on the largest study on Appalachian oral health to date were Dan McNeil, Ph.D., of WVU, and Robert Weyant, Dr.P.H., and Mary Marazita, Ph.D., of the University of Pittsburgh.