Tooth and Consequences Print
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Tooth and Consequences
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ImageOver 100 million people in the U.S. have toxic metal permanently implanted in their teeth—and if you’re over age 30, there’s a good chance you’re one of them. Dental amalgam, which most people know as their metal-colored “silver fillings,” is approximately 50 percent mercury.

Yet according to Dentistry Associate Dean Tim DeRouen, people don’t need to worry about their fillings; the mercury in your mouth won’t harm you. DeRouen is the lead author of a study published in the Journal of the American Medical Association last year, which compared 253 children who had amalgam fillings with 254 children who had mercury-free fillings. It found that amalgam had no harmful effects.

Not everyone is persuaded by the study’s results. Some organizations that want to end the use of mercury in dentistry have criticized the study’s design and maintain that amalgam is dangerous. But DeRouen says the science is clear. “I think this pretty much settles the question as far as the average response of most kids,” he says. “The average kid who gets an amalgam filling is not at any higher risk of neurodevelopmental problems or neurobehavioral problems than kids who don’t.” Since children are thought to be more sensitive to the effects of mercury due to their still-developing brains and bodies, the implication is that adults can breathe easier about their fillings too.

To make dental amalgam, elemental mercury—a liquid at room temperature—is mixed with an alloy powder containing silver and small amounts of other metals such as copper, tin and zinc. When this mixture is placed in a damaged tooth, it hardens quickly into a tough, long-lasting shield against decay. For much of the last 150 years, amalgam has been the most commonly used material for repairing cavities in teeth—and also the subject of periodic debate.

The current round of controversy was sparked in the late 1970s and 1980s, when highly sensitive technologies revealed that amalgam fillings—long believed to be chemically inert once they had hardened in the mouth—actually release small amounts of mercury vapor whenever a person chews or brushes their teeth. Videos of this process are dramatic, showing a sinister-looking smoke rising from the surface of molars. Some of this mercury vapor is absorbed by the lungs; studies have shown a direct relationship between the number of amalgam fillings and the level of mercury in a person’s blood, urine and tissues.

Much of what we know about the dangers of mercury comes from studies of people who were exposed to high doses through occupational accidents or environmental disasters. At high doses, mercury can cause a slew of neurological effects such as tremors, anxiety, personality changes, and loss of muscle control, memory or coordination. It also damages the kidneys, digestive system and other organs throughout the body.

However, the amount of mercury vapor released by fillings is extremely small, about 5 to 9 micrograms per day, depending on the number of fillings you have and what you’re chewing. Anti-amalgam groups say mercury is so toxic that even these miniscule amounts—a microgram is a millionth of a gram—are dangerous. They blame dental mercury for autism, multiple sclerosis, Alzheimer’s disease, immunological problems and a host of other ills.

Yet studies have failed to confirm a link between amalgam fillings and such diseases, and a variety of public health bodies—including the U.S. Food and Drug Administration, the U.S. Public Health Service, the Centers for Disease Control and Prevention, the National Institutes of Health and the World Health Organization—have all declared amalgam safe. Then again, studies of long-term, low-level mercury exposure are relatively scarce, and their results not always clear. Despite 150 years of widespread use, dental amalgam has never been the subject of a randomized controlled clinical trial—the gold standard, scientifically speaking, for deciding questions of treatment safety.

Never, that is, until now.