An amalgam actually consists of a combination of metals including silver, tin, indium, copper, and liquid (elemental) mercury. Small amounts of zinc or palladium may also be used. This combination of metals has been used successfully for more than 150 years in hundreds of millions of patients around the world.
The chemical properties of elemental mercury allow it to react with and bind together the metal alloy powder to form an amalgam. Together the alloy particles form a strong, durable, and solid filling. Indium helps retain the mercury so that less is released into the environment. By adding copper to the alloy, less mercury is needed to bind the elements.
Stronger than Composite Fillings
Today resin composite restorative materials are available (see “Tooth-colored Fillings”). Therefore, amalgam is used less often because of the esthetics. However, the newer resin materials cannot be used in all situations. Amalgams are stronger, hold up better over time, and can outlast tooth-colored fillings by 10 to 15 years. This is especially true for teeth that undergo a lot of pressure and wear from chewing. Amalgam is also tolerant of saliva or blood contamination during placement (unlike composites). It is faster to place so patients spend less time in the dental chair and amalgam is less costly than other materials.
How safe is amalgam?
Everyone is exposed to mercury through air, drinking water, soil and food. Over the years, concerns have been raised about the use of amalgam because it contains mercury. Dental amalgam contains elemental mercury. It releases low levels of mercury in the form of a vapor that can be inhaled and absorbed in the lungs. High levels of mercury vapor exposure are associated with adverse effects on the brain and the kidneys.
Considered Safe by the FDA
The FDA has reviewed the best available scientific evidence to determine whether the low levels of mercury vapor associated with dental amalgam fillings are a cause for concern. Based on this evidence, the FDA has concluded that the amount of mercury vapor released from amalgams in the mouth is minimal. Therefore, dental amalgam is a safe restorative material and there is no association between its use and adverse health effects in the general population. Clinical studies in adults and children ages six and above have found no link between dental amalgam fillings and health problems.
The amount of clinical data available regarding long-term health outcomes in pregnant women and their developing fetuses, and children under the age of six, including infants who are breast-fed is very limited.
However, the estimated amount of mercury in breast milk attributable to dental amalgam is low and falls well below general levels for oral intake that the Environmental Protection Agency (EPA) considers safe. Despite the limited clinical information, the FDA has concluded that the existing risk information supports a finding that infants are not at risk for adverse health effects from the mercury in breast milk of women exposed to mercury vapor from dental amalgam.
What Precautions are Used?
Dental amalgam is packaged in special capsules. The metal alloy mixture is a powder. The metal alloy and the liquid mercury are separated in compartments by a membrane inside the capsule. They are mixed in a special machine that punctures the membrane and combines the elements while in the capsule. Once mixing is complete, the capsule is opened. By the time the soft amalgam putty is placed in a patient’s tooth, the mercury has formed a compound with the other metals and is no longer toxic.
Amalgam is placed inside a prepared tooth with pressure that causes the mercury to rise to the top. Dr. Best overfills patients’ teeth and removes the mercury rich layer, further lessening their exposure to mercury. During its placement, high-powered suction is used to capture any mercury vapors and remove amalgam remnants.
Should amalgam fillings be removed and replaced?
Replace amalgam fillings only when they are worn, broken or when there is decay beneath the filling. Removing good amalgam fillings results in unnecessary loss of healthy parts of the tooth and exposes a patient to additional mercury vapor released during the removal process.
In rare cases, people have had allergic or sensitivity reactions to the mercury or metals in dental amalgam. The American Dental Association says that fewer than 100 cases of this type of allergy have been reported. Other dental filling materials are available for these patients.