| Dental
amalgam is a common material used to fill cavities. Fillings made with
amalgam also are known as silver fillings. Over the years concerns have
been raised about the use of amalgam because it contains mercury. We
talked with David A. Albert, D.D.S., M.P.H., associate professor of dentistry
and public health at Columbia University College of Dental Medicine and
the Mailman School of Public Health, about the safety of dental amalgam.
What is amalgam?
Amalgam is a combination of metals that has been used in dentistry for more
than 100 years and is still commonly used today. Although it sometimes is
called "silver amalgam," amalgam actually consists of a combination
of silver, mercury, tin and copper, and small amounts of zinc, indium or
palladium.
With the development of tooth-colored materials to restore teeth, amalgam
is used less often than in the past, but the newer materials can't be used
for all situations. Amalgam has been popular as a material for dental fillings
and restorations because it is less expensive than other materials and holds
up better over time, especially in teeth that undergo a lot of pressure and
wear from chewing.
How safe is amalgam?
Millions of people have amalgam fillings. Although concern has been raised
over the mercury in amalgam, and the issue has been studied extensively,
researchers have not found evidence of significant health problems related
to the use of amalgam in fillings.
The U.S. Food and Drug Administration (FDA) has evaluated research on the
safety of dental amalgam and has not found any reason to limit its use.
Why is nercury used in amalgam?
Mercury is used in amalgam because when it is mixed with an alloy powder,
it creates a compound that is soft enough to mix and press into the tooth,
but which hardens quickly and can withstand the forces of biting and chewing.
Why the concern about mercury in amalgam?
Mercury is a metal that occurs naturally in the environment. Mercury can
exist as a liquid — as is seen in many thermometers — or, when
heated, as a gas. It also can be combined with many other materials.
Everyone is exposed to mercury through air, drinking water, soil and food.
Concerns have been raised, for instance, about the amount of mercury accumulating
in fish as a result of pollution. Mercury enters the air from industries
that burn mercury-containing fuels. Mercury from all sources can accumulate
in body organs.
As with most substances, the degree of harm caused by mercury in the body
is related to the amount. Very low levels don't cause any ill effects. At
higher levels — for instance, when workers are exposed to mercury through
their jobs — mercury can cause a number of symptoms including anxiety,
irritability, memory loss, headaches and fatigue.
The controversy over mercury in amalgam centers on how much mercury is released
from fillings and absorbed into the body. In the past, it was thought that
amalgam fillings were inert, meaning that no mercury was released once the
filling was complete. In recent years, sophisticated tests have shown that
very small amounts of mercury in the form of vapor can be released as the
amalgam wears.
Research on this issue is complex and has arrived at various estimates of
the actual amount of mercury released. However, several reviews of the research
have concluded that any amount released from amalgam in the mouth is very
low.
"Studies have shown that the amount of mercury you are exposed to from
your fillings is less than the amount that most people are exposed to in
their daily environment or in the food they eat," Dr. Albert says.
Do some people have reactions to amalgam?
In rare cases, people have allergic reactions to the mercury in amalgam.
The ADA says that fewer than 100 cases of this type of allergy have ever
been reported. People allergic to amalgam can receive alternative filling
materials.
Should pregnant women be concerned about amalgam fillings?
Research over the years has not demonstrated any health effects from amalgam
fillings in pregnant women. However, mercury can cross the placenta. In general,
dentists recommend that pregnant women avoid unnecessary dental care. During
pregnancy, the placement of amalgam restorations should be avoided. Pregnant
women who need a cavity filled can talk with their dentists about alternatives
to amalgam restorations.
Should anyone else consider alternatives to amalgam fillings?
Since any concern about mercury is related to the total amount of mercury
absorbed from all sources, some people who have high exposure to mercury
may want to consider alternatives to amalgam. For instance, dentists may
consider alternatives for people who are exposed to mercury through their
occupation, or who eat large amounts of seafood.
If amalgam is safe, why does my dentist take precautions when handling
it?
Because dentists work with mercury almost every day, they must take safety
precautions. Without appropriate protection, dentists can inhale mercury
vapors, which over time can produce symptoms of mercury toxicity.
To make dental amalgam, dentists mix liquid mercury with a powder containing
silver, tin and other metals. Dentists purchase special capsules that contain
the powder and the liquid mercury separated by a membrane. They use special
machinery to puncture the membrane and mix the amalgam while it is still
in the capsule. Once mixing is complete, the capsule is opened. By the time
the amalgam is placed in your tooth, the mercury has formed a compound with
the other metals and is no longer toxic.
If you are receiving an amalgam filling or having one removed, your dentist
will use high-powered suction to remove any excess amalgam from your mouth.
Dentists' offices have special disposal systems for any extra amalgam, and
the sink drains have special traps to prevent amalgam from entering the plumbing
system.
Are there alternatives to amalgam?
There is now a dental amalgam that contains indium as well as mercury. The
indium helps retain the mercury so that less is released into the environment.
There are also high-copper amalgams, which contain less mercury and more
copper.
Dentists use other materials to restore teeth, such as composite resin,
porcelain and gold. Amalgam is stronger than composite resin (a tooth-colored
material) and requires less time in the dentist's chair. Because it wears
faster than amalgam, composite resin can't be used in every situation.
Should I visit an amalgam-free practice?
"It is not necessary to seek treatment at a practice that does not use
mercury. However, if you have a mercury allergy, you may want to consider
it," Dr. Albert says. Generally, if you have any concerns about amalgam
fillings, talk to your dentist about them and whether there are alternatives
to amalgam that would work for you.
Should I have my amalgam fillings removed?
"I advise my patients to replace amalgam fillings only when necessary," Dr.
Albert says, "such as when fillings are worn or broken. Because there
is no evidence that amalgam fillings can cause a problem, I think it is best
not to remove existing restorations that function well. The process of removing
the restorations can release more mercury. If you are concerned about amalgam
as a restorative material, choose a different material for your new restorations."
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