The widespread practice of giving some people antibiotics before they undergo dental work to prevent a rare but potentially lethal heart infection appears to be unnecessary, a study by researchers at the University of Pennsylvania found.
The study, published last week in the Annals of Internal Medicine, challenges the 50-year-old practice of prescribing preventive antibiotics before any dental work, including teeth cleaning, to people who have been diagnosed with a variety of heart conditions. These include mitral valve prolapse, a common and usually inconsequential deformity of a heart valve that typically requires no treatment; a heart murmur; congenital heart disease or a history of rheumatic fever.
The common practice, endorsed by the American Heart Association and the American Dental Association, is believed to affect about 10 percent of the U.S. population. Mitral valve prolapse, for example, affects between 5 and 10 percent of Americans.
The antibiotics are supposed to prevent endocarditis, an infection of the heart valves that can be fatal if it is not treated. Endocarditis occurs when bacteria are introduced into the bloodstream and migrate to the heart, damaging the valves and the lining of the heart. The infection is common among intravenous drug users who use non-sterile equipment to inject drugs.
Bacteria can be introduced in other ways, as well, such as an injury from a normal activity such as brushing the teeth, chewing food or a getting a nick during a dental procedure. In people with normal heart valves, the bacteria are repelled by the body. But in people with damaged valves, the bacteria may be trapped and can multiply.
The view that endocarditis can be linked to dental work arose decades ago after retrospective studies found that 15 percent of patients who developed the infection had recently been treated by a dentist. For decades susceptible patients have been told to take amoxicillin before having dental procedures.
To determine whether dental procedures are a cause of endocarditis in susceptible people, Brian L. Strom, a professor of epidemiology and statistics at the University of Pennsylvania School of Medicine, and his colleagues analyzed the cases of 273 people hospitalized for endocarditis at 54 hospitals in the greater Philadelphia area between 1988 and 1990. None of the participants was an intravenous drug user.
They were matched by age, sex and residence with a control group of healthy patients. Researchers then collected medical and dental records and compared the two groups.
Strom and his team found that people who developed endocarditis were no more likely than the control group to have undergone dental work in the three months before they developed the heart infection. Endocarditis can occur rapidly, in a matter of days, or more slowly, over a period of weeks.
However, patients who developed endocarditis were more likely to have pre-existing heart-valve problems that predisposed them to infection. They were substantially more likely to have a previous heart infection or mitral valve prolapse.
"Antibiotics are not benign," said Strom. "There are acute side effects and some of these side effects are life-threatening. Choosing to use them indiscriminately in the case of dental work makes no sense. There are probably going to be more deaths (from antibiotic allergies) than from endocarditis."
But officials at the American Heart Association and the American Dental Association, both of which recommend prophylactic antibiotics for patients with valve problems, said they plan no immediate change in their recommendations that patients with abnormal heart valves take antibiotics before undergoing dental work.
"Further research is warranted to determine whether some heart or valvular conditions would require coverage with pre-procedural antibiotics while others would be precluded," the ADA said in a statement.
"This is one study," said Heart Association spokesman Brian Henry. "We are adhering to the guideline."
Yet a companion editorial in the Annals of Internal Medicine recommended that prophylactic antibiotics be discontinued for most dental procedures and for most patients.
Widespread use of antibiotics, wrote David T. Durack of Becton Dickinson Microbiology Systems, is unnecessary, expensive and can contribute to the burgeoning global problem of antibiotic-resistant bacteria.
He noted that an earlier study conducted in the Netherlands found no relationship between dental work and endocarditis.