Taking antibiotics before visiting the dentist may do more harm than good, the American Heart Association says.

Some dentists prescribe antibiotics before routine cleanings or extractions to prevent infective endocarditis, an infection of the heart's inner lining or valves. But the AHA now says that is only needed for people at high risk, such as those with artificial valves, a history of endocarditis or serious heart problems.

The doctor who led the work, Walter Wilson, said there is no evidence that the antibiotics prevent infection, and they may increase resistance of bacteria when infections do occur.

A news release said that everyday tooth brushing causes 154,000 times the risk of exposure to bacteria that could cause problems than having a tooth pulled.