Young adults who keep their wisdom teeth often quickly develop gum disease, which appears to increase the risk of pregnancy complications and possibly other health problems, according to the first large studies to carefully evaluate the risks posed by wisdom teeth.

The research, which is being released today, should prompt more dentists and patients to closely monitor the extra molars -- and consider removing them -- even if they are not impacted or causing obvious problems, experts said.

Data from 254 patients in their twenties who opted to keep all four wisdom teeth and underwent detailed follow-up examinations found that a surprisingly high proportion -- 60 percent -- already had signs of early gum disease around those teeth when the study began, and about 25 percent experienced a worsening over the next two years.

Wisdom teeth, also known as "third molars," are the last teeth to emerge, usually pushing through the gums between ages 17 and 25. The decision about whether to extract them if they are not causing pain or damaging other teeth remains highly controversial among dentists because few well-designed studies have evaluated the issue.

"This research is very important to dentistry," said Leon Assael, an oral surgeon at the Oregon Health & Sciences University in Portland who edits the Journal of Oral and Maxillofacial Surgery, which will publish the studies. "It indicates that there are both general oral health and overall health implications related to the wisdom teeth that were not known before."

The new data come from a series of studies the American Association of Oral and Maxillofacial Surgeons launched in the late 1990s at the University of North Carolina in Chapel Hill and the University of Kentucky in Lexington. The first findings will be described at a news conference today in Boston in advance of the group's annual meeting.

"The conventional wisdom is that people who have gum disease typically don't have a problem until they are 35 or 40 years old," said Raymond P. White Jr. of the University of North Carolina, who led the studies. "We found it is much more prevalent than anyone believed at a much younger age than anyone thought."

Gum disease occurs when bacteria grow in the tissue supporting teeth, which can damage the tissue and cause spaces known as pockets to form around the roots. As it worsens, the infection can loosen and damage the teeth, eventually requiring them to be pulled. Wisdom teeth are particularly vulnerable because they are difficult to reach and keep clean. Once the bacteria get established in the mouth, the risk they will spread and damage other teeth increases significantly.

The new findings indicate that patients and dentists need to monitor wisdom teeth much more carefully, White and others said.

"People assume that if you don't have any symptoms, you're okay," White said. "What we're saying is that's not necessarily the case."

A growing body of evidence has also linked inflammation from chronic infections in the body, including gum disease, to an increased risk of a host of more serious problems, including heart disease, diabetes complications and pregnancy difficulties. Scientists suspect chronic inflammation releases bacteria or toxic substances that can have myriad adverse effects elsewhere in the body.

"There's probably 100 papers now that link periodontal disease, which is just another type of chronic infection, with many health complications," White said.

Data collected from another study involving 1,020 pregnant women in their twenties at Duke University found that those who kept their wisdom teeth and had the worst signs of gum disease were more than twice as likely to give birth prematurely -- on a par with the risk associated with cigarette smoking, the researchers found.

"This fits in with the idea that if you have chronic inflammation some place, you're at greater risk for negative health outcomes, in this case preterm birth," White said.

Based on the findings, dentists should pay much more attention to wisdom teeth in women who are pregnant or planning to get pregnant soon, White and others said.

"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. "No one thought of checking women of this age for periodontal disease because no one would have thought it could be a problem."

The increased risk could not be explained by factors such as age, diet, weight, previous preterm birth, marital status or lack of health insurance, White said.

Bruce Pihlstrom of the National Institute of Dental and Craniofacial Research said the findings were interesting but not conclusive.

"It is an association. It doesn't demonstrate cause and effect, by any means," said Pihlstrom, whose institute is funding two large studies to see whether treating gum disease reduces the risk of preterm birth.