WASHINGTON — After more than three decades of controversy, the Food and Drug Administration on Tuesday issued new safety guidelines for mercury-based dental fillings that reaffirm the agency's long-held position that their use isn't a serious health threat to patients.
Tuesday's announcement fulfilled a procedural act that Congress first ordered back in 1976 but that had languished for decades as the dental industry, consumer advocates and scientists debated the safety of mercury-based fillings, also known as "dental amalgams."
Consumer groups, which have pushed for a ban on mercury in fillings, attacked the agency's announcement and promised a court challenge.
More than 100 million Americans have dental amalgams that are about 50 percent liquid mercury and 20 to 35 percent a powdered alloy made from silver, tin, copper, zinc and other metals, according to the FDA.
Consumer advocates and a number of scientists have argued for years that when these fillings are inserted or removed — and even when people are chewing — the mercury releases harmful vapors that could have toxic effects on the nervous systems of young children and fetuses.
For decades, they've called on the FDA to ban or greatly control the use of mercury-based fillings in pregnant women and young children, who may be most sensitive to the exposure.
However, long-term clinical studies of adults and children 6 and older who have the fillings haven't established a causal link between mercury fillings and serious illness, said Susan Runner, the head of dental devices at the FDA's Center for Devices and Radiological Health.
"The best available scientific evidence supports the conclusion that patients with dental amalgam fillings are not at risk for mercury-associated adverse health effects," Runner said.
The same holds true for fetuses, breast-fed infants and children younger than 6, who are more sensitive to mercury vapors, Runner said.
Although clinical data on the long-term effects of mercury-based fillings in these groups are limited, Runner said, "The scientific evidence that is available suggests that these populations are also not at risk."
As a result, the FDA didn't require dentists to tell patients about the potential health risks of mercury-based fillings, which have been used for more than 150 years.
Instead, the agency classified dental amalgam as a Class II, or moderate risk, medical device with special controls on its use. Gold and tooth-colored composite fillings are in the same class.
Dr. John Findley, the president of the American Dental Association, praised Tuesday's action.
"The FDA has left the decision about dental treatment right where it needs to be: between the dentist and the patient," Findley said.
After the announcement, the FDA pulled a "question and answer" page from its Web site that discussed potential health risks of mercury-based fillings.
Consumer groups were furious.
"Bowing to the dental products industry, FDA for the first time in its history pulled a warning about neurological harm to children. This contemptuous attitude toward children and the unborn will not go unanswered. We will see FDA in court," said Charles G. Brown, the national counsel for Consumers for Dental Choice, who brought a lawsuit that compelled Tuesday's action.
Brown said that the FDA's stance was in stark contrast to countries such as Norway and Sweden, which have banned amalgam.
The FDA's Runner said, however, that studies have found that adults and children 6 and older with mercury-based fillings were exposed to vapor levels that were below or equal to federal safety levels. Further, higher levels of exposure don't "necessarily mean that any adverse effects will occur," she said.
In children younger than 6 who have mercury in their fillings, Runner said, their smaller teeth and respiratory volumes would lessen their levels of exposure and minimize their risk as well. Runner said that women with mercury-based fillings who breast-fed their children didn't put them at great risk, because the estimated amounts of mercury in breast milk were below federal safety levels for oral exposure.
The only group of people who are at risk from the fillings, Runner said, are people with mercury allergies, who could suffer "contact reactions in the mouth."
The FDA is requiring that this information be on the labels for dental amalgam along with:
_ A warning that dental workers use adequate ventilation when they're handling amalgam.
_ A statement discussing the benefits and risks of using dental amalgam and the risks of inhaled mercury vapor.
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