April 30 (HealthDay News) -- Only a small number of people should take antibiotics before dental procedures to protect them against infective endocarditis (IE), according to updated guidelines from the American Heart Association.

IE is an infection of the heart's inner lining or the heart valves.

For most people, taking antibiotics before they go to the dentist may cause more harm than good, according to the guidelines, which are based on the latest scientific evidence.

For decades, doctors have recommended that patients with any kind of heart abnormality take short-term antibiotics before they undergo any dental work, including teeth cleaning. But this use of antibiotics carries risks, including dangerous allergic reactions and the possibility that bacteria that cause IE will become antibiotic-resistant.

New evidence indicates that the risks of this kind of antibiotic use outweigh the benefits, the AHA says. Only people at the greatest risk of bad outcomes from IE should receive short-term preventive antibiotics prior to dental procedures, the guidelines recommend.

This includes people with artificial heart valves, a history of previous IE, certain serious congenital heart conditions, and heart transplant patients who develop a problem with a heart valve.

"We've concluded that if giving prophylactic antibiotics prior to a dental procedure works at all -- and there's no evidence that it does work -- we should reserve that preventive treatment only for people who would have the worst outcomes if they get IE. That's a profound change from previous recommendations," writing group chair Dr. Walter R. Wilson, a professor of medicine at the Mayo Clinic in Rochester, Minn., said in a prepared statement.

The new guidelines were published in a recent issue of Circulation.