- Mercury is a potent nerve poison, and
our mouths are full of the stuff in the form of amalgam, the silver-grey
material that for more than 150 years has been the material of choice to
patch cavities in teeth.
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- For seven years, Jim Copeman says, he
experienced such debilitating bouts of chronic fatigue and depression that
he thought he was losing his mind.
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- He consulted specialists, tried therapy
and took antidepressants, but nothing seemed to help until he followed
a suggestion by his sister, whose similar symptoms vanished after she had
her dental fillings removed.
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- Mr. Copeman was skeptical at first, but
he had a mouthful of fillings -- 14 large ones in all -- and thought he
had nothing to lose. He had them taken out earlier this year. Since then,
he says, he's been transformed.
-
- "Honest to God, it is the difference
between black and white," he said. "I've started to get busy.
I got my life back. I'm a normal person."
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- Experiences such as his are rekindling
the long-running controversy over the possible health effects of filling
teeth with amalgam, the silver-grey material that for more than 150 years
has been the material of choice to patch cavities in teeth.
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- Amalgam means mixture, and the fillings,
found in the heads of most North American adults, are half mercury, along
with tin, copper and silver.
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- It's easy to see why dentists in the
last century became fond of using amalgam. It's easy to work with, durable
and inexpensive. When it first came into use, it was a major factor in
making dental care widely available because it cost less than gold.
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- There was little concern about mercury
because it was assumed to be inert in the filling and not to enter the
body.
-
- But research conducted in the past 15
years, much of it in Canada by investigators at the University of Calgary,
has shown that trace amounts of mercury vapour are continually released
from fillings, and that higher amounts are emitted every time people eat,
brush or grind their teeth.
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- The mercury is inhaled and accumulates
throughout the body, with the largest amounts in the kidneys, brain, lungs,
liver and digestive tract. In pregnant women, mercury crosses the placenta
and enters the fetus.
-
- Since this early research, a growing
body of further scientific evidence has raised warning flags about amalgam
fillings' possible effects on patients -- and on dentists.
-
- Mercury is one of the most poisonous
materials known. It is a potent nerve poison and is one of the substances
under investigation as an endocrine disrupter, a substance that interferes
with the normal functioning of the hormone systems of living things.
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- It has been banned or removed from most
of its once-common uses in paints, thermometers, batteries and other products.
Dozens of advisories warn anglers against eating fish that contain trace
amounts of it.
-
- But in Canada and almost everywhere else
in the world, large amounts of mercury are still placed directly in people's
mouths, where the metal is uniquely positioned to enter people's bodies.
-
- Estimates by Health Canada indicate that
about half the public's exposure to mercury comes from dental amalgam.
-
- The amounts involved are small -- in
the range of a few millionths of a gram a day -- and controversy is raging
over whether such exposure is dangerous.
-
- Federal health officials studied amalgam
safety two years ago and issued a statement saying that "current evidence
does not indicate that dental amalgam is causing illness in the general
population."
-
- Nonetheless, Health Canada said that
as a general principle "it is advisable to reduce human exposure to
heavy metals in our environment, even if there is no clinical evidence
of adverse health effects," provided that the costs aren't too high
and alternatives are safe.
-
- In line with this principle, the government
currently recommends that amalgam not be used in children, pregnant women,
people with kidney disease or the estimated 2 per cent to 3 per cent of
the population with an allergy to mercury.
-
- The Canadian position is similar to one
Germany adopted in 1995. Sweden has gone a step further. It recommended
that amalgam use be stopped in those under 20 in 1995. Next year, Sweden's
national dental plan will no longer pay for amalgam fillings, a step toward
a total phaseout.
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- Some dentists say Health Canada isn't
being tough enough and have amalgam-free practices. They advise their patients
against using it.
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- "I haven't used mercury since the
first tests showed that mercury comes out of the fillings," said Murray
Vimy, a Calgary dentist and professor at the University of Calgary who
has conducted extensive testing on mercury emissions from amalgam.
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- Dr. Vimy said that even the tiny amount
of mercury that escapes from fillings should be of concern. "They're
not small [quantities]. These are pharmacological doses. Your hormones
in your body run on doses that are a thousand times smaller than this."
-
- He recommends a "zero-mercury exposure
or as close to zero as possible" and is surprised that the dental
profession hasn't taken an aggressive stand against its use.
-
- "If you ask a chemist, 'Tell me
about mercury' -- not a dentist now, someone who is unrelated to dentistry
-- they'll tell you that mercury is one of the most toxic elements in the
periodic table. They've banned mercury thermometers in hospitals all over
the world. People have more mercury in one filling than you have in a thermometer."
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- But determining whether mercury vapour
in the mouth has a deleterious effect is difficult: Few studies have looked
at the medical ailments of amalgam bearers compared with people without
amalgam.
-
- The effects of mercury-vapour toxicity
are so wide-ranging as to confound even the most diligent investigator.
Low levels can cause tremors, loss of memory, insomnia, depression, irritability,
personality changes, weight loss and distress.
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- The range of mental symptoms helped coin
the phrase "mad as a hatter," because hat makers were once exposed
to high levels of mercury.
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- Under Canada's regulatory system, amalgam
has been exempt from a requirement that all new medical devices put into
the body for more than 30 days undergo a safety review before they are
marketed. When the requirement was introduced in 1982, amalgam and most
other dental materials were given an exemption because they were already
in use.
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- For those worried about amalgam, most
dentists and Health Canada advise against the wholesale removal and replacement
of serviceable fillings.
-
- Even amalgam critic Dr. Vimy replaces
his patients' amalgam fillings with non-metallic replacements only as they
succumb to normal wear and tear.
-
- The Canadian Dental Association also
recommends against the wholesale removal of fillings, saying it doesn't
make sense from a health or financial point of view, except for those with
sensitivity to amalgam.
-
- Having fillings removed and replaced
can be costly. Mr. Copeman, for instance, said his cost $2,200.
-
- There are a number of non-metallic alternatives
to amalgam, including composites, resins, and ceramic crowns.
-
- But these tend to be more costly and
may not be completely risk free. Some research has indicated they can emit
toxic substances while they are setting, and their safety has not been
studied in much more depth than amalgam.
-
- "We don't know quite what leaches
out of these products," said Richard Sandilands, president of the
association. "It's the devil you know versus the devil you don't know
in some respects."
-
- Dr. Sandilands says amalgam has proved
itself. "Until we see something better, we're not going to jump off
the diving board here."
-
- Health Canada says the alternatives typically
do not release toxics indefinitly, as amalgam does mercury vapour. Once
cured, they tend to be inert. The department concluded that the "alternative
materials now in use appear to pose lower risks than amalgam."
-
- Dental amalgam is the subject of a class-action
lawsuit sponsored by Canadians for Mercury Relief against the federal government
and suppliers of the material, Johnson & Johnson Inc. and Dentslpy
Canada Ltd.
-
- Another question about amalgam is whether
its use may accentuate symptoms of nerve diseases such as Parkinson's,
Alzheimer's and multiple sclerosis. Health Canada, however, says no evidence
has been found linking these diseases with amalgam.
-
- Dr. Vimy says patients should try to
minimize their risks, particularly in cases where other family members
have these diseases. "My recommendation would be if you have a family
history of neurological diseases . . . you wouldn't want to have a neurological
poison diffusing out of your teeth."
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- http://health.theglobeandmail.com/docs/news/19981215/Health/HMERC.html
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