Dental Amalgam

Dental Amalgam

Also called: Amalgam Fillings, Silver Fillings, Metal Fillings

Reviewed By:
Kenneth Cheng, D.D.S.

Summary

Amalgam is a material composed of mercury and a mixture of several metals (e.g., silver, copper, tin). It is a strong and stable substance used in dental restorations for repairing tooth structure lost to tooth decay and cavities. Amalgam restorations are popularly known as silver fillings. It has been used for over 100 years and is the dominant material used for fillings. Use of amalgam has been declining over the past few decades due to the availability of alternative restoration materials (e.g., composite resin).

Due to the durability of amalgam and its ability to withstand substantial chewing stress, it can be used to restore decayed molars, which handle the greatest chewing load in the mouth. Amalgam is also used for fillings in areas that are difficult to keep dry during the dental procedure (e.g., deep fillings below the gumline).

To identify a need for fillings, patients need to see a dentist for a dental examination. A combination of physical examination and x-rays are used to identify tooth decay and cavities. Before the filling can be placed, the tooth is prepared by removing any decay. A portion of the healthy tooth structure often must also be cut away to help retain the amalgam filling.

There is usually little or no discomfort after an amalgam restoration has been placed, although some patients may experience some sensitivity to hot and cold. It is important to maintain diligent dental hygiene and see a dentist regularly for a dental examination and cleanings, because an amalgam filling does not protect the tooth from additional tooth decay.

Amalgam has many advantages over other restoration materials. It is very strong and wears away more slowly than other materials, except for gold. It also can be placed into the cavity more quickly. Furthermore, amalgam is the least expensive material available.

However, amalgam has certain drawbacks. The silver color of amalgam does not look like natural tooth enamel and the material often requires removing more of the healthy tooth structure than other materials. Sometimes, a small gray or blue discoloration can appear on the soft tissues (e.g., inner cheeks, gums) near the filling. This is completely harmless and is known as an amalgam tattoo. In rare cases, patients may have an allergic reaction to amalgam.

Concern over the potential safety of the mercury in amalgam has been raised by some people. Opponents of amalgam have blamed the substance for a variety of general health problems, from nerve damage to compromised immunity. According to experts in the subject at the American Dental Association, U.S. Centers for Disease Control and Prevention, National Institutes of Health and the U.S. Food and Drug Administration(FDA), there is no sound scientific evidence of a link between amalgam fillings and any other health problems.

About dental amalgam

Amalgam is a strong, stable substance used to repair tooth decay and cavities. Amalgam restorations are popularly known as silver fillings. They are composed of a metal alloy (mixture) chemically bound to elemental mercury. Silver usually makes up the bulk of the alloy, with copper and tin being the other common metals. Additional metals that may be used in the alloy include indium, palladium and zinc.

Mercury is added to the alloy in a less than 1:1 ratio. According to the Academy of General Dentistry (AGD), mercury is the only element that has the properties necessary to bind the alloy together in a form that is effective for filling cavities.

Amalgam is a safe, durable and affordable material that has been used in dental fillings for over 100 years. According to the American Dental Association (ADA), amalgam has been used in over 100 million Americans and is the most commonly used material in the United States to fill cavities in the back of the mouth. The AGD estimates that over 1 billion individual amalgam fillings are placed every year.

Questions about the safety of the mercury in amalgam have been raised by some people. However, various health organizations such as the ADA, U.S. Food and Drug Administration (FDA) and National Institutes of Health (NIH) agree that there are no well-designed scientific studies that indicate a connection between amalgam and problems with a patient’s general health. According to the ADA, the makeup of the metal alloy used in amalgam makes the mercury stable and safe for use. This chemical reaction is similar to the combination of two potentially hazardous substances (sodium and chlorine) that produces common table salt. Amalgam has been researched, tested, studied and reviewed more thoroughly than any other restorative material in modern dentistry and has been repeatedly found to be safe and effective.

The use of amalgam has been declining during the past few decades due to a number of different factors, including increased availability of more cosmetically appealing alternative materials. For example, composite resin fillings may closely match the appearance of natural teeth. In addition, the use of other types of dental restorations (e.g., crowns, inlays, onlays) instead of fillings has increased. Also, the incidence of tooth decay has declined due to increased use of preventative measures such as fluoridated water supply, fluoride treatments, brushing, flossing and regular dental appointments.

Conditions treated with dental amalgam

Dental amalgam is used extensively in the treatment of tooth decay and cavities in patients of all ages. It is used for small to moderately sized cavities and may be used in both primary and permanent teeth.

Due to the durability of amalgam and its ability to withstand substantial chewing stress, the material can be used to restore molars, which must handle the greatest chewing load. Because of its ease of use and versatility, amalgam is also important in restorations of areas that are difficult to keep dry during the restorative procedure (e.g., deep fillings below the gumline).

Amalgam is not typically used in areas that are easily visible when patients speak or laugh (e.g., the front of the mouth) or in patients who are allergic to mercury or any other component of the alloy.

Before, during and after the procedure

Prior to an amalgam procedure, a dentist will perform a dental examination and evaluate the patient’s dental history. In most cases, the teeth are probed with an instrument to check for soft spots that might indicate decay.  X-rays are also generally taken to help identify tooth decay and cavities in difficult-to-see locations (e.g., between teeth, below the gumline). Before the procedure begins, the dentist will usually discuss the advantages and disadvantages of amalgam fillings versus alternative materials (e.g., composite resin) with the patient.

Typically, a local anesthetic is injected into the soft tissues around the tooth to be restored. Before the amalgam filling is placed, the tooth is prepared and isolated to block out moisture and contamination using a rubber-like material called a dental dam. Then, decay is drilled out of the tooth.

The procedure usually involves first drilling away decayed (carious) tooth structure then a cavity preparation to receive the amalgam. Often, a portion of the healthy tooth must also be removed to hold the amalgam in place. In some cases, a dentist will cut small channels or angeled undercuts into parts of the tooth to aid in the retention of the amalgam filling. When the amalgam flows into these channels or undercuts and hardens, it functions to hold the amalgam in place. Tiny dental pins which are inserted into the floor of the cavity preparation may also be used for this purposed. In general, dentists attempt to remove as little healthy tooth as possible.

The dentist may line the prepared area with a material for protection and insulation, and to help bond the amalgam to the tooth. For example, a cavity varnish or resin bonding system may be used to seal the space between the tooth and the amalgam. Once the area is prepared, the amalgam is placed and shaped in it. The dentist may need to make some adjustments, such as polishing the filling or adjusting the bite by using a form of carbon paper (articulating paper) to see where the tooth touches the opposing tooth.

There is usually little or no discomfort after an amalgam restoration has been placed, although some patients may experience sensitivity to hot and cold. If a filling is particularly large or deep, this sensitivity is more likely to occur. If any additional problems arise, such as pain or sensitivity when biting down, patients are advised to consult their dentist.

Old amalgam fillings can crack and require replacement. Cracks may be caused by the force of chewing or wear over time. Cracks in fillings can often be repaired using the same type of material.

In general, amalgam restorations require the same care as natural teeth. It is important to maintain diligent dental hygiene and visit a dentist regularly for a dental examination and cleaning. An amalgam filling (or other types of dental restoration) does not protect the tooth from future tooth decay. To prevent future decay in the area, proper preventive measures, such as daily brushing and flossing, are required.

Potential risks and benefits of dental amalgam

Amalgam has been used in dental restorations for over a century and it still has many advantages over other restorative materials. It is very strong and wears more slowly than other restorative materials, except for gold. According to the American Dental Association (ADA), amalgam lasts a long time – often more than 12 years. Amalgam fillings can be placed more quickly than other types. Unlike other materials, amalgam can be placed in areas that are difficult to keep dry during the procedure (e.g., below the gumline).

The techniques for placing amalgam fillings are different from those for composite resin. Composite resin requires a completely dry field for it to adhere to the tooth and sometimes requires the use of ultraviolet light to make it harden. Amalgam is the least expensive restoration material available. For example, other materials cost over four times as much as amalgam.

However, amalgam does have certain drawbacks. The silver color of amalgam does not look like natural tooth enamel. The metals in the amalgam can also corrode or tarnish. In addition, larger amounts of healthy tooth structure may have to be cut away than with other materials to hold the filling in place.

Sometimes, a small gray or blue discoloration can appear on the soft tissues (e.g., inner cheek, gums) near the amalgam restoration. This is called an amalgam tattoo and is caused by the transfer of tiny particles from the restoration to the soft tissues. Amalgam tattoos are harmless and cause no symptoms, although they may be visible on x-rays. They may appear similar to early forms of oral cancer (melanoma), so it is important to bring any discoloration to the attention of a dentist. A dentist can determine if the mark is a harmless amalgam tattoo or a cause for concern.

In rare cases, patients may have an allergic reaction to amalgam. This is typically characterized by an eczema-like lesion on the soft tissues near the restoration. When this occurs, the filling needs to be removed and replaced with a different material (e.g., composite resin).

Toxicity controversy surrounding dental amalgam

Some people may be concerned regarding the safety of mercury in amalgam fillings. It is known that a miniscule amount of mercury vapor is released from amalgam when the restorations are placed or removed, and through chewing and tooth grinding. Many opponents of amalgam have blamed the substance for a variety of general health problems (e.g., nerve damage, autism, Alzheimer’s disease, multiple sclerosis, kidney problems, birth defects, compromised immunity).

However, according to the American Dental Association (ADA), U.S. Centers for Disease Control and Prevention (CDC), National Institutes of Health (NIH) and the U.S. Food and Drug Administration(FDA), there is no sound scientific evidence of a link between amalgam and these or any other health problems. The amount of mercury vapor that escapes from amalgam is too small to cause harm. In addition, dentists generally use measures to remove the vapor from the patient’s mouth (e.g., evacuators that suck out the vapor) during placement or removal. Including the metal indium in the alloy further reduces the amount of mercury vapor released.

According to the Academy of General Dentistry, patients absorb larger amounts of mercury from air, water and foods than from amalgam fillings. The ADA has stated that even a mercury-sensitive patient would need nearly 500 amalgam fillings to notice subtle symptoms of mercury poisoning.

Nevertheless, the controversy has prompted many patients to seek the removal of amalgam fillings in the hope of a miracle cure for another medical condition. There is no scientific evidence that such cures actually occur. Furthermore, the unnecessary removal of any restoration can cause increased damage to the tooth.

Human error and limits in knowledge and technology make it impossible to absolutely state that any substance, including amalgam, is completely safe. However, according to the ADA, amalgam has been more thoroughly studied than any other dental restorative material. The CDC points out that other materials, including composite resin, may also possess dangerous components that may eventually be linked to general health problems.

Since the dangers of amalgam cannot be completely ruled out, it may be recommended that pregnant women avoid amalgam fillings. If a cavity needs to be restored during pregnancy, an alternative material (e.g., composite resin) can be used. Dentists generally urge pregnant women to avoid any unnecessary dental procedures, including removing fillings that are not faulty or defective.

In addition, some people have a hypersensitivity or allergy to amalgam. This is extremely rare and may be due to the mercury or another component of the alloy. People may also have allergies to other types of restorative materials, such as composite resin.

Questions for your doctor regarding dental amalgam

Preparing questions in advance can help patients to have more meaningful discussions regarding their treatment options. Patients may wish to ask their doctor the following amalgam-related questions:

  1. Why is amalgam the best option for my restoration?

  2. Are there other types of filling material I should consider?

  3. What type of anesthetic will be used before placing my filling?

  4. Will the amalgam be attached to my tooth with a pin, or with some type of bonding?

  5. How big will my filling need to be?

  6. Will my filling be visible when I speak or laugh?

  7. Do I require multiple fillings? How many?

  8. What is your opinion on the amalgam controversy?

  9. What measures will you take to remove the mercury vapor from my mouth while placing my filling?

  10. How long is my filling likely to last?
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