Are ‘silver’ dental fillings safe?
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Your Environment drills into the controversy |
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.
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. They
also claim that the ADA has failed to disclose information
regarding the significant risk of harm associated with the
fillings in order to promote the continued use of amalgams, a
product in which it has a financial stake as a paid endorser.
“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.
TRACKING MERCURY’S VAPORS
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.
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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.
The Battelle team also found “convincing new evidence
of adverse behavioral effects associated with mercury
exposures from amalgam fillings within the range of that
received by the general population.” And researchers at the
Colorado State University, Department of Physiology, in
Fort Collins, Colo. have linked dental amalgam exposure to
mental illness.
Haley and other scientists, including Vimy and
Lorscheider, found in experiments on rat brains that chronic
inhalation of low-level mercury — at levels that simulate
exposure to amalagam fillings — can inhibit brain chemistry,
producing lesions similar to those in Alzheimer’s diseased
brains. Mercury inhibits the efficiency of tubulin, a protein
vital to brain cells, they explain.
‘SAFE’ FOR HUMAN USE
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.”
LOOKING TO THE FUTURE
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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