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Are ‘silver’ dental fillings safe?

Your Environment drills into the controversy

By Francesca Lyman


July 11 —  Anyone who has ever had a tooth cavity has probably seen a dentist who drilled it and packed it with a “silver” filling. But how many patients know what’s in that silver? And whether it could have consequences for your health?

PAINED FOR years by fatigue, aches, severe allergies and other chronic ills, Lydia Bronte never suspected that the cause of her problems might be something in her teeth.

It wasn’t until she sought the help of holistic physician Dr. Warren Levin that she got relief. Levin diagnosed Bronte with mercury poisoning and pointed to her dental amalgams as a probable source.

After realizing she had 17 dental amalgams in her mouth, Bronte was doubly shocked to discover that these “silver” fillings were not made chiefly of silver but of an alloy whose principal ingredient is mercury, a metal that can cause neurological damage at high levels.

“I was very conservative at the time and found this diagnosis hard to believe,” she says. “Nevertheless, based on the high mercury reading in [urine and blood] tests, I decided to have the amalgams out.”

This, and further treatments to remove the metal from her body, she says, made a big difference. Today, though not feeling 100 percent, she says her condition has vastly improved.

Could silver dental fillings be causing, or contributing to, health problems? Holistic health advocates, environmentalists and a growing cadre of “mercury-free” dentists fear amalgams emit dangerous levels of mercury, stirring up a health controversy that goes back 150 years.

Scientists agree that when absorbed in high enough doses, mercury, in all its chemical forms, can damage the brain, nervous system, kidneys and other organs, especially in infants and children. But they differ on not only how much mercury must be absorbed to cause adverse health effects, but also just how much of the amalgam’s mercury is absorbed by the human body to begin with.

Dental associations pooh-pooh alleged dangers. The ADA considers it “a safe, affordable and durable material” that has been used for “more than 150 years and during that time has established an extensively reviewed record of safety and effectiveness.”

ADA quotes the U.S. Public Health Service’s 1993 report stating that amalgam has no health consequences other than for a small percentage of people who might be allergic to the metals.

Others, however, like Boyd Haley, a chemist at the University of Kentucky, argue that it is harmful to more than just sensitive populations. Most people with amalgam fillings get an unsafe dose of the heavy metal because mercury vapor leaks continually from the fillings, says Haley, who recently testified before Congress on mercury exposure in children.

Consumer groups argue, meanwhile, that dental patients ought to be told about what’s going into their mouths. 

Mercury amalgams
Long-lasting (8-12 years)
Easy to apply
Resistant to fracture

Potentially allergenic
Potentially neurotoxic at high levels
Aesthetically unpleasing
Cosmetically preferred
Conserves tooth structure

Not as long-lasting (6-8 years)
Health concerns (potentially endocrine-disrupting)
Cost (1.5 times as expensive as mercury amalgam)
Glass ionomers
Conserves tooth structure
Cosmetically pleasing

Lasts only five years
Gold foil

Cost (4 times as expensive as amalgam)
Long lasting (12-18 yrs)
Resistant to fracture

8 times as expensive
Poor aesthetics
Poor conservation of tooth structure

In June, a coalition of citizens’ health and environmental groups filed suit against the American Dental Association for allegedly deceiving consumers into thinking amalgam fillings are made of silver, when in fact the major component (about 50 percent, according to the suit) is mercury.

“If mercury is so safe, why do they try to hide it?” says Charlie Brown, one of the lawyers representing Consumers for Dental Choice (CDC), a plaintiff in the suit. Brown notes that CDC has already succeeded in winning a state ruling that requires the California state dental board to advise participating dentists to tell their patients about the mercury content of amalgam fillings as well as discuss with them any sensitivities and the potential for adverse reactions, including suspected links to birth defects.

Although mercury has been known to be poisonous since ancient times, dentistry associations claim that the mercury is tightly bound with other metals, rendering it safe. Silver fillings usually contain a mix of silver, tin and copper as well as zinc and other metals, according to the Journal of the American Dental Association.

Mercury is essential to make the amalgam harden and adhere, says ADA spokesman J. Rodney Mackert, professor of dentistry at the Medical College of Georgia and an expert in materials science.


It wasn’t commonly known that amalgam released mercury vapor until recently, although the issue was raised more than a century ago. In 1985, Fritz Lorscheider, a fetal physiologist, and Canadian dentist Murray Vimy showed that mercury in amalgam continuously vaporizes; measuring mercury in the mouths of 46 people, they also found that the amount of vapor released from fillings rose when the subjects chewed gum or brushed their teeth. In 1990, the same scientists reported that studies on sheep using radioactively tagged mercury revealed that the highly volatile and unpredictable element travels to the gastrointestinal tract, kidney, liver and brain.

“Whether those [latter] studies are applicable to humans is a matter of serious importance to public health,” says Dr. Norman Braveman, a research administrator at the National Institute of Dental and Craniofacial Research (NIDCR), which has two studies underway on the subject. At issue, he says, is what dose of mercury a typical patient gets in the dentist’s office, how much he is exposed to daily and potential health effects that might arise from this dose. And there isn’t much agreement on any of those questions.

“There’s no question that mercury is not healthy for us,” says Vasken Aposhian, a professor of cellular and molecular biology at the University of Arizona who has studied how mercury acts on the body. How many amalgams you have makes a big difference in terms of how much mercury your body’s absorbing, he maintains.

“Some people are hyper-sensitive to metals and can get very sick” from amounts that others can safely handle, he says. “Most are at risk from multiple exposures from fish, food and other sources.”

At a Congressional hearing on the use of mercury in medicine last year, Aposhian told legislators that Americans’ greatest exposure to mercury is from fillings - a serious threat, he says, because it can cross the placenta and harm the developing nervous system of the fetus.

ADA, however, maintains that the amount of mercury that vaporizes from the amalgam is trivial, and less significant than exposures in food, water and air. “Yes,” acknowledges ADA’s Mackert, “mercury is a poison,” and amalgams vaporize, “something only recently discovered.” But, he argues, “there is no convincing evidence that the small amount of mercury vapor from amalgams has any effect on humans.”

Further, says Mackert, repeating the mantra of the ADA, “there have been no studies conclusively linking mercury from dental amalgams with any diseases.”

But concerns about possible effects “can’t be dismissed,” as the U.S. Public Health Service noted. Studies show that people with more dental amalgam fillings have higher levels of mercury in their bodies. And researchers at the University of Calgary School of Medicine showed that mercury could be found in the blood and tissues of pregnant mothers and their fetuses within a few days after mercury fillings were placed.

Mercury in dental fillings has been linked to other adverse health effects. Anne Summers, a microbiologist at the University of Georgia, for example, found that mercury from fillings can inhibit the effectiveness of antibiotics. Scientists at the Battelle Centers for Public Health Research and Evaluation in Seattle linked exposure to mercury vapor from dental amalgam fillings to central nervous system toxicity among dental personnel. Researchers at the Colorado State University, Department of Physiology, in Fort Collins, Colo. have also linked dental amalgam exposure to mental illness.


Despite such studies, though, the National Institutes of Health, the U.S. Public Health Service, and the World Health Organization have all concluded that amalgams are safe enough to use. There is “no solid evidence of any harm for millions of Americans who have these fillings,” wrote the U.S. Public Health Service, and “no persuasive reason to believe that avoiding amalgams or having them removed will have a beneficial impact on health.”

By contrast, Canada recently restricted the number of amalgams that could be placed in children and pregnant women, following similar laws passed in Sweden, Germany, the United Kingdom and other countries. But having produced its new guidelines, the U.K. government then qualified that it had no evidence that there was a risk from amalgam, complicating the issue even further.

While the battle for reliable science rages, many dentists are switching away from mercury. A 1995 survey of dentists found 8.7 percent wanting to ban amalgam and 12.3 percent uncertain about its safety, according to a report published in the March issue of the Journal of the American Dental Association.

Dr. Anthony McLaughlin, a Redmond, Wash., dentist says he isn’t necessarily in the anti-mercury camp but has eliminated amalgams from his practice for his own safety and that of his staff; he also removed all the mercury from his own teeth, and that of his wife and his staff.

Remembering how he had to dispose of his scrap amalgam as hazardous waste, he says, “It’s OK to place these in people’s mouths yet it’s considered hazardous when you take it out. Go figure that one out.”


Given amalgam’s long track record, however, the government is hesitant to ban it without greater evidence of harm to human health.

“If we ban this material,” NIDCR’s Braveman, “what are our alternatives, and will they do the job as well?”

For now, he says, two government-funded studies are tracking 1,000 children — half with mercury amalgams, half with alternative materials — for such traits as behavior, intelligence, antibiotic resistance, immune function and memory. The results, he says, will be available in about four years.

In the meantime, if you’re concerned that you have a great many mercury fillings, Bronte suggests checking yourself for symptoms of mercury toxicity and having your fillings replaced with non-toxic materials.

“If your regular dentist really isn’t familiar with these materials, you are better off finding a dentist who is familiar with them,” advises Bronte, who went on to write “The Mercury in Your Mouth” after her health improved.

As more patients find out what’s in mercury fillings, adds advocate Brown, “more dentists will make it their business to know about the alternatives.”

Francesca Lyman is an environmental and travel journalist and editor of the American Museum of Natural History book, “Inside the Dzanga-Sangha Rain Forest” (Workman, 1998).

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