When your dentist determines that you have a cavity in a tooth, he or she will tell you that you need a filling. But what exactly will your dentist use to fill the hole after the decay has been removed? Dental amalgam is the most widely used and researched material for fillings. It has been used to restore the teeth of more than 100 million Americans over the past 150 years.

Dental amalgam is a mix of metal (also known as an alloy) that is made by combining mercury, silver, tin, copper, and sometimes other metallic elements.

Because amalgam fillings can withstand a lot of chewing, they are useful especially for restoring molars in the back of the mouth, where the chewing load is greatest. They also are good in areas that are hard to keep dry, such as in deep fillings below the gum line. Amalgam fillings, like other filling materials, are considered biocompatible, which means that patients don't have a lot of problems with them and allergic reactions are very rare.

Disadvantages of amalgam include possible short-term sensitivity to cold after the filling is placed, which is also true of other dental materials. The silver-colored filling is not as natural looking as one that is tooth-colored and might be visible when you laugh or talk. To prepare the tooth, the dentist may need to remove more tooth structure to accommodate an amalgam filling than for other types of fillings.

Although dental amalgam continues to be a safe, commonly used restorative material, there have been some concerns because it contains mercury. However, because the mercury in amalgam is combined with other metals, it is safe for use in filling teeth. Major U.S. and international scientific and health organizations, including the National Institutes of Health, the U.S. Public Health Service, the Centers for Disease Control and Prevention, the Food and Drug Administration, and the World Health Organization, are satisfied that dental amalgam is a safe, reliable, and effective restorative material.

If you are concerned about amalgam, talk to your dentist. Dentists can use other materials to fill a tooth, such as composite resin, porcelain, and gold. Your dentist will advise you about the most practical, safest option for your situation.