There are about 100 published studies linking gum disease to other health complications.

Periodontal disease develops when bacteria grow in the gums and hidden roots of teeth, damaging the tissue and causing gaps to form around the roots, eventually loosening the teeth. Infection can spread to other teeth and other parts of the body more easily in people with gum disease.

Researchers from the University of North Carolina and the University of Kentucky found that 60 percent of the study subjects had signs of infection around their wisdom teeth when they were first examined, and one in four had well-established gum disease two years later, despite having no signs or symptoms.

"This was a surprise to us, since most people assumed that you don't get periodontal problems until you are age 35 or 40. We found it's more prevalent than anyone believed at a much younger age than anyone had thought," said Dr. Raymond White, a professor of oral surgery at UNC's School of Dentistry and the leader of the study.

Wisdom Teeth

The results were presented Tuesday during a news conference at the annual meeting of the American Association of Oral and Maxillofacial Surgeons in Boston and will be published in the association's journal.

The data are part of a study the association set up in the late 1990s to consider what happened over time in young adults who either kept their wisdom teeth -- also called the third molars at the rear of the head and jaw -- and those who had them taken out.

"Part of the reason we were asked to spearhead these trials was that research at UNC and elsewhere showed that the inflammation in the mouth that periodontal infections cause promoted inflammation in other parts of the body," White said, noting there are about 100 published studies linking gum disease to other health complications.

"The primary health concern with third molars is infection, just like with other teeth," agreed Dr. Robert Glickman, a professor at New York University's College of Dentistry, who was not part of the study team. "However, because of their unique location in the jaws, infections from third molars spread down the neck in the lower jaw and to the orbits (eyes), sinuses, and brain in the upper jaw."

White's team collected baseline data on about 400 people who planned to keep their wisdom teeth -- the four rearmost teeth in the mouth -- and have more than two years of follow-up information on 254 of them. They'll continue the study for at least another five years.

Pregnancy and Gum Disease

Another study done on 1,020 high-risk pregnant women in their 20s at Duke University found that those who kept their wisdom teeth and had the worst signs of gum disease were twice as likely to give birth prematurely than those free of disease. The 18 percent preterm delivery rate is comparable to women who smoke while pregnant, White said.

Since untreated gum disease "seeds" the bloodstream with disease-causing bacteria, "women planning on getting pregnant should be certain to get their teeth and mouth checked, and certainly shouldn't forget about their wisdom teeth," White said.

Even people who scrupulously attend to brushing and flossing have difficulty reaching the backmost teeth.

But while most people develop some degree of decay or infection of at least one wisdom tooth in their lifetime, 25 percent don't, so "it's too early to recommend strongly that everyone [have] their wisdom teeth removed," White said. "It's a good idea to have the third molars evaluated before you're 25," he added.