A federal advisory panel is trying to decide whether the U.S. Food and Drug Administration relied on adequate science when it determined last year that mercury amalgam can safely be used to fill cavities in healthy people. At the time, the FDA didn't find evidence that dental mercury hurts developing fetuses, young children and those more sensitive to its potential health effects.
The FDA's scientific review of evidence about dental amalgam fillings, commonly called "silver fillings" because of their silver-gray color, found them safe for adults and children at least 6 years old. Dental amalgam is an approximately 50-50 mixture of liquid mercury and powdered metal alloy of silver, tin and copper. When mixed, it forms a pliable putty-like substance that hardens into place.
The mercury in amalgam fillings, called elemental mercury, releases small amounts of mercury vapor – a substance that at high levels can be toxic to the brain and kidneys. Vapor levels are highest right after fillings have been placed in a tooth, and later if they're being removed or replaced. People trying to stop the use of mercury in dentistry say mercury vapor levels are boosted by chewing, eating, brushing teeth and drinking hot liquids. The mercury that accumulates in the bodies of fish is methylmercury, which is generally considered more toxic.
"Even in adults and children ages 6 and above who have 15 or more amalgam surfaces, mercury exposure due to dental amalgam fillings has been found to be far below the lowest levels associated with harm," according to an FDA document titled "About Dental Amalgam Fillings." The document says mercury levels in breast milk also fall below those considered safe by the Environmental Protection Agency and the federal Centers for Disease Control and Prevention. In addition, the World Health Organization has said that amalgam restorations are safe and effective.
However, many Americans still worry about dental mercury exposure, and some have sought out mercury-free dentists who advise them to have their amalgam fillings removed and replaced with other types of fillings. Some mercury amalgam opponents fear that having the heavy metal in the mouth is related to higher rates of autism and behavioral problems in children, although there hasn't been proof it causes neurological injury in youngsters.
In the summer of 2009, the FDA moved dental amalgam from a low-risk category to one of elevated risk, under which it began requiring warnings for patients, dentists and dental assistants about inhaling mercury vapors, disclosure of mercury amalgam's health risks to dental patients, and assurances that the material is handled in properly ventilated areas and isn't used in patients with a known mercury allergy or sensitivity. But the new rule didn't warn that any particular groups faced higher risks than others.
Soon afterward, the FDA received four petitions asking it to reconsider the rule and ban or restrict mercury's use in dentistry.