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Dental Amalgam:

Dental Amalgam: A Health Risk?

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. he 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."