The Straight Story on Dental Amalgam

When a decayed tooth needs to be filled, patients have several options, including composites (white fillings), gold, or the silver-colored fillings called "dental amalgam." In recent years, white fillings have surpassed dental amalgam as the most frequently used material, but dentists still value amalgam for such cases as: 

• Cavities below the gumline;
• Large cavities in back teeth, where chewing forces are greatest,
• Areas of the mouth that are difficult to keep dry; and
• For treating patients, such as children and the disabled, who have difficulty keeping still during dental treatment.  

Dentists have used amalgam safely and effectively to restore teeth in more than 100 million Americans.

Dental amalgam is an alloy made by combining silver, copper, tin and zinc with mercury. Because mercury is a principal ingredient, people may be concerned about how amalgam might affect their health or the environment. Rest assured that dental amalgam has been studied and reviewed extensively, and has established an excellent record of safety and effectiveness. Similar to the way hydrogen (an explosive gas) combines with oxygen to form water, the mercury in dental amalgam combines with the other metals to form a stable alloy.

On the environmental front, dentists continue to utilize technology and common sense to minimize the already small amount of amalgam waste that enters public sewer systems.  It is important to note that the mercury in the amalgam is chemically bound and differs significantly from the methylmercury that is of greatest concern. Chairside traps and vacuum filters in dental offices capture most waste amalgam before it enters the sewer line. Screens and settling chambers designed to capture particulate matter in wastewater treatment plants capture most of the rest.   The ADA recommends that dentists recycle amalgam captured in chairside traps and vacuum filters. 

Isn’t mercury toxic?

Like virtually every substance to which people are exposed, mercury can be toxic in specific forms and specific doses.  It is important to distinguish dental amalgam, a solid intermetallic compound of mercury, silver, tin and copper, from mercury.  Exposure to dental amalgam cannot correctly be compared to exposure to an equivalent amount of mercury, whether in the human body or the environment.  Nor is the mercury contained in amalgams present as methylmercury, or readily converted to this organic form, which is of most concern to human health.

U.S. and international agencies responsible for protecting public health—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, among others, have independently concluded that dental amalgam is a safe, effective restorative material. 

If it is a hazardous material before it is in the mouth, and it is a hazardous material when it’s removed from the mouth, how can it be safe when it is in the mouth?

That would be accurate if you were asking about free mercury, but it doesn’t apply to dental amalgam, which, once in alloy form, remains that way. Like many substances used in health care, dental amalgam requires proper handling during manufacture, shipping, storage and use in accordance with federal, state and local laws and rules. Amalgam that is removed from patients’ teeth should be recycled. The relevant question is whether a substance creates a measurable, negative effect on health, and dental amalgam does not.  It has consistently proven to be a safe and effective material.

What about rumors linking dental amalgam to disease?

No properly designed, peer-reviewed scientific study links dental amalgam to any neurological or systemic disease.  Significant research about dental amalgam continues, most notably two ongoing randomized, clinical trials, begun in 1997 on the biological effects of dental amalgam in children.  These studies, supported by the National Institute of Dental and Craniofacial Research, seek to determine whether dental amalgam has any demonstrable adverse health effects by measuring a whole array of neuropsychological functions, such as IQ, learning ability and behavior.  Children participating in these studies also are being tested for kidney function and mercury levels in blood, urine and hair.  And while those ongoing studies will not be completed until 2006, the government would have halted them immediately if at any point during the past six years the study subjects showed any sign that amalgam was harming them. 

Other organizations concerned about public health, such as the Alzheimer’s Association, the National Multiple Sclerosis Society and the American Academy of Pediatrics all have publicly stated that there is no scientific evidence linking dental amalgam with any disease or syndrome. The Autism Society of America states that there is no known cause for autism, but that it is generally accepted that it is caused by abnormalities in brain structure or function, and that children with autism are born with the disorder or born with the potential to develop it.  The Institute of Medicine has concluded that there is no evidence linking mercury to any of the pathophysiological changes known to be associated with autism, such as genetic defects.

Does dental amalgam release mercury vapor in the body?

Amalgam fillings are known to emit minute quantities of mercury vapor during vigorous chewing or grinding.  The amounts of mercury vapor emitted by amalgams fall well within levels considered safe, that is, they show no toxicity and cause no adverse health reactions.  In fact, one prominent researcher has estimated that even an especially sensitive person would have to have hundreds of amalgam fillings before exhibiting even subtle symptoms of excessive mercury exposure.

Why do dentists refer to amalgams as “silver fillings,” when they contain much more mercury than silver?

Dentists and scientists generally refer to this material as “dental amalgam.” However, some dentists and many patients refer to these restorations as “silver fillings,” because, traditionally, it was a way to distinguish them by appearance from “gold fillings” (gold) and the more recently developed “white fillings” (composite resin).  In fact, the word amalgam means an alloy of mercury with another metal.

Why does the ADA continue to recommend amalgam fillings when alternatives exist?

The ADA does not recommend any single restorative material.  The ADA believes that patients, in consultation with their dentists, should have a full range of treatment options, including filling materials, basing decisions on what is most clinically appropriate to meet each patient’s needs. Dental amalgam is but one of many dental filling materials that the ADA evaluates to help dentists and their patients choose safe, appropriate and effective treatments.

Are amalgams more profitable for dentists?

No, the opposite is true.  Restoring teeth with other materials, such as gold or composites is costlier, and involves more complex and time-consuming procedures.

Has the ADA ever profited from dental amalgam?

No.  Scientists at the ADA Health Foundation (ADAHF) obtained two patents in the early 1970s for changes in the formulation of dental amalgam.  These patents were never exploited commercially and have long since expired.  Neither the ADA nor its foundation earned a cent from the patents.

In the past, the ADA charged a modest fee to manufacturers to help cover a small part of the cost of evaluating products submitted to the ADA’s Seal of Acceptance program.  The Seal program evaluates dental products according to stringent, objective criteria of safety and effectiveness and awards the Seal to products that are found in tests to meet these criteria.  Participation is strictly voluntary, and the fee was charged regardless of whether the product was accepted or not.  The ADA receives no money from the sale of an accepted product.

The total cost to maintain the Seal program is approximately $1.5 million annually.  Fees paid by amalgam manufacturers to the Seal program totaled about $5,100 per year, or less than one-half of one percent of the program’s total costs.  ADA members pay most of the cost of operating the Seal program as a service to the public and the profession.  On July 1, 2002, the ADA eliminated fees for evaluating all professional products, including dental amalgam.

Is the FDA questioning the safety of dental amalgam?

No. In fact, Dr. David W. Feigal, director, FDA Center for Devices and Radiological Health, told a congressional committee in November 2002 that, given the current scientific understanding of dental amalgam, the agency would approve its use as a dental device if it were submitted today.  In a consumer update posted on December 31, 2002, the agency states, “FDA and other organizations of the U.S. Public Health Service (USPHS) continue to investigate the safety of amalgams used in dental restorations (fillings). However, no valid scientific evidence has shown that amalgams cause harm to patients with dental restorations, except in the rare case of allergy.”

The ADA supports the FDA’s recent proposal to classify amalgam products in a single regulatory category (Class II) and require that manufacturers’ labels list ingredients in descending order of weight by percentage and include lot numbers, appropriate warnings and precautions, handling instructions and expiration dating.

Does the Centers for Disease Control and Prevention’s Second National Report on Human Exposure to Environmental Chemicals affect that agency’s position on amalgam safety?

Absolutely not.  According to Dr. Jim Pirkle, CDC’s deputy director for science, the report’s significance is that the agency now will be able to track more accurately the sources of mercury present in human beings.  In a press briefing about the report, agency personnel mentioned fish and water as being the primary sources of human exposure.  Dr. Pirkle added, “[W]hat I would say is that we haven’t got an urgent alarm that’s sounding.”

Is waste amalgam a significant source of mercury pollution?

No. Very little amalgam enters the environment to begin with. Research is ongoing as to whether amalgam releases mercury over time and, if so, to what extent.  The mercury contained in amalgams is not present as methylmercury or readily converted to methylmercury in the environment.  The mercury in dental amalgam would need to undergo a series of chemical changes in order to become “methylated.”  This process is not automatic; it can occur only in certain environmental conditions and requires the presence of specific microorganisms.  That said, the ADA and its member dentists are committed, both as health professionals and as members of their communities, to using “best management practices” to minimize the amount of amalgam discharged by dental offices.

What are dentists doing to reduce amalgam discharge?

State and local dental societies across the country are adopting (or have adopted) waste management guidelines, in concert with environmental and waste disposal experts, and have urged their members to follow best management practices.  Anecdotal information provided by state and local dental societies indicate that in at least 35 states plus the District of Columbia, there are voluntary programs to reduce amalgam discharge from dental offices. 

These voluntary activities have been favorably received by environmental regulators and widely publicized through their networks to regulators in other areas of the country and the U. S. Environmental Protection Agency.  These activities include:

·        Developing guidelines or recommendations for managing waste in dental offices, (best management practices), often as joint endeavors with environmental regulators; 

·        Distributing literature on waste management;

·        Education and training programs or workshops for dentists;

·        Fostering communication between dental societies and environmental regulators; and

·        Scrap amalgam recycling.

The ADA serves as a clearinghouse for state dental societies seeking information and advice on environmental issues and encourages state dental associations to work cooperatively with state and local environmental regulators to develop effective programs to reduce discharge of dental amalgam into the waste stream. 

How do dentists dispose of the scrap dental amalgam captured in their offices?

The ADA recommends recycling of amalgam scrap.  The ADA plans to ask the U.S. EPA to help facilitate the collection and transport of amalgam scrap and make recycling easier, especially for dentists in rural areas.

Conclusion

Dental amalgam use is declining, as more patients and dentists choose newer, more natural-looking, tooth-colored restorative materials.  If current trends continue, newer materials eventually may replace conventional dental amalgam entirely.  But for now, dentists and patients still value amalgam in numerous instances, and the ADA is therefore committed to protecting the patient-doctor decision to select this durable, cost-effective material among the safe options available for restoring decayed teeth. 

August 2005