PHILADELPHIA (AP) _ Could diligent flossing and brushing lower the risk of a heart attack? It's not as odd as it might sound.

Some researchers think the same bacteria that rot the gums might do bad things elsewhere in the body. Surveys show that people with bad teeth and gums also tend to have more heart trouble, and circumstantial evidence is accumulating that this is more than a coincidence.

The latest piece of supporting data came Monday at a meeting of the American Association for the Advancement of Science. A researcher said his animal experiments suggest that some strains of the most common bacteria that build up on teeth can trigger blood clots.

``Our data suggest that bacteria may cause blood clots that can actually obstruct coronary arteries,'' said Dr. Mark Herzberg of the University of Minnesota.

That could lead to heart attacks, which occur when blood clots get stuck in heart arteries already clogged with cholesterol.

Others suggest that even if dental bacteria are not harmful, the body's reaction to them could be.

People with periodontal disease have a lifelong simmering infection that causes chronic inflammation of the gums. In response, their bodies release a slow, steady stream of potent germ-killing chemicals that might in themselves be harmful.

``The ramification of this inflammation can be far-reaching,'' said Dr. Frank Scannapieco of the State University of New York at Buffalo, who has done research in the area.

He and others say this constant, low-level infection could play a role in other common conditions, such as diabetes, lung diseases and even premature births.

About three-quarters of adults over age 35 have some degree of periodontal disease, a painless condition that often gives off few warnings except, perhaps, red gums and bleeding when brushing.

Under the surface, however, are pockets of infection that contain billions of bacteria. If this oozing mess was out where it could be seen, it would be a bone-deep sore the size of the palms of both hands.

When bacteria build up on the teeth, they form crud called plaque. The most common form of germ in dental plaque is Streptococcus sanguis. Herzberg found that about 60 percent of all strains of S. sanguis are capable of making the blood clot in a test tube.

In experiments on rabbits, Herzberg found that when one strain of S. sanguis was injected into their blood, it made clots form for about a half-hour. Electrocardiograms showed the clotting was bad enough to slow the flow of blood in heart arteries and deprive the heart muscle of all the oxygen it needed.

Ordinarily, collagen can make blood clot. Herzberg said the bacteria have structures on their surface that look just like collagen, a protein. And clotting cells in the bloodstream mistake these for the real thing.

The bacteria may carry this fake collagen as a kind of camouflage, Herzberg said. It fools the immune system into letting the bacteria pass as though it is a normal part of the body.

Large-scale studies suggest that those with bad gums and teeth have about double the usual risk of dying from heart disease.

Proving that gum disease is to blame is difficult. Heart disease and periodontal disease are both especially common among the poor. Some experts wonder if bad gums are simply a sign of poverty in people with heart trouble and not a cause of their troubles.

At least three more big studies are under way to help settle this. But the work so far suggests that bad gums could be as strong a risk factor for heart attacks as smoking cigarettes, which is blamed for about 40,000 heart-related deaths a year.

Over the past two decades, deaths from heart disease have been declining. Better diets and treatments probably account for some of this. But Herzberg believes there may be another explanation: Better dental care.