Why do dentists use amalgam tooth fillings?

Jonathan B. Levine, DMD
Growing up, most of us who had cavities had them filled with amalgams made of silver, tin, mercury, and some other trace elements like copper. While their aluminum-foil like appearance weren’t the most attractive, they were durable (many last up to 20 years). Today, even though more attractive tooth-colored composite resins are available (and used by many dentists), the standard amalgam is what most dentists still fill cavities with.

Theories of mercury leaking from cavities causing toxicity resulting in certain autoimmune diseases have spread far and wide in the dental world. But while high mercury levels found in certain seafood have altered people’s menu selections, its appearance in fillings is far less volatile. Although mercury by itself is classified as a toxic material, the mercury in an amalgam is chemically bound to other metals to make it stable and therefore safe for use in dental applications. In fact, amalgam is the most thoroughly studied and tested restorative material now used. The safety and effectiveness of amalgams have been reviewed by major U.S. and international scientific and health bodies, including the American Dental Association (ADA), the National Institutes of Health (NIH), the U.S. Public Health Service (PHS), the Centers for Disease Control and Prevention (CDC), the Food and Drug Administration (FDA), and the World Health Organization (WHO). All have concluded that amalgam is a safe and effective material for restoring teeth.
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Dentists use amalgam ("silver") tooth fillings because they're strong and they last a long time -- typically at least seven years, and usually longer. They also are the least expensive type of fillings. Dental amalgam is a mixture of metals; the fillings are known as silver fillings because of their silver color. Dentists often use them for fillings in the back teeth.
The amalgam filling has been proven over time to be a durable material. The use of silver amalgam continues to be a viable option when used in areas of low esthetic importance. The clinical use of amalgam has continued due to its relatively low cost, wear resistance and high survival rates.
Amalgam fillings, or silver fillings, can withstand very high chewing loads, they are particularly useful for restoring molars in the back of the mouth where chewing load is greatest. They are also useful in areas where a cavity preparation is difficult to keep dry during the filling replacement, such as in deep fillings below the gum line. Amalgam fillings, like other filling materials, are considered biocompatible -- they are well tolerated by patients with only rare occurrences of allergic response. 

Dental amalgam has been used by dentists for more than a century and is the most thoroughly researched and tested restorative material among all those in use. It is durable, easy to use, highly resistant to wear and relatively inexpensive in comparison to other materials. For those reasons, it remains a valued treatment option for dentists and their patients.
Amalgam fillings are a time-tested restoration that can be provided at a reasonable cost. They are strong, not as technique sensitive as some other more costly restorations, and they can last for a long period of time. They are relatively easy to place well and shape and smooth properly. Also, they can often be successful in less than ideal situations, such as below the gum, when access is not good, or moisture control is a challenge.

Although patients may feel they are not as good or "nice" as composite tooth-colored fillings, they can often be more successful than composites especially in challenging areas. Amalgam fillings can be contoured nicely and therefore provide a restoration that contacts adjacent teeth well, and occludes properly with opposing teeth.
There are a number of choices in materials to restore a damaged tooth. Amalgam has a VERY long track record (over 150 years).

It is a durable material, is relatively inexpensive compared to other materials, and is not as technique-sensitive as other materials. Its physical properties may also give it an advantage in certain situations.
Amalgam fillings are 50% mercury. Most dentists have been taught that the mercury in fillings is bound and not released. This has now been proven to be totally false. Mercury is poison and according to the World Health Organization amalgam fillings are the number one contributor to whole body mercury levels. Teeth can now be filled with an inert composite or porcelain material. These materials have now been refined and actually are better for your teeth. The materials must be used properly and the restorations will last just as long and  longer than amalgam. Even better, the composites and porcelains will not crack your teeth as does amalgam.
Dentists may use amalgam or silver fillings to fix cavities in teeth. Amalgam fillings are strong and durable. They are generally more economical than tooth-colored fillings. They can be used in areas that are hard to get to and hard to keep dry in filling the tooth. See your dentist, who can best explain which filling material would be best for your tooth.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.