Sign up for our FREE Mailing List to receive the latest news!


By Sandra Duffy, President, Consumers for Dental Choice
Alternatives Magazine,, Fall 2006 Issues 39 and 40

Sandra Duffy

Hardly a week goes by without an article in the paper or a feature on the evening news about human exposure to toxic mercury from the fish you eat, the air you breathe or the water you drink or play in.

But few people are aware that the primary source of mercury exposure for most people is their metal dental fillings, commonly called “silver fillings,” that are, in truth, approximately 50% elemental mercury. Silver comprises 25-35% of the filling and the balance is varying combinations of tin, copper and zinc. The average mercury-based filling contains ½ gram of mercury, about the same amount found in the old-fashioned mercury thermometers that are being outlawed state-by-state. 1

In 1991, the World Health Organization published a monograph on inorganic mercury that identified mercury amalgam dental fillings as the primary source of mercury in the bodies of those who have amalgam fillings. 2 Yet, almost without fail, fish is routinely identified in media stories as the primary source of mercury exposure for most people. What accounts for this disconnect between the facts and journalistic accuracy? The answer lies in the 170-year history of amalgam in America and who controls the information that gets to dental consumers and the media.

In sixteenth and seventeenth century America, dentistry was a subspecialty of medicine. Painful or decayed teeth were either pulled or cavities were filled with molten gold – a painful and expensive procedure.

In 1833, the Crawcour brothers, who were French dentists, immigrated to the United States and introduced the use of amalgam as a dental restoration material. 3 The medical community was well aware of the toxicity of mercury. Nineteenth century hat makers were known to go insane from felting hats with a mercury solution. Lewis Carroll made that knowledge part of the popular lexicon with his nonsensical Mad Hatter in his best selling novel, Alice in Wonderland. Additionally, the poor quality of the amalgam also led to its condemnation by many medical dentists. In the 1840’s these medical dentists formed the American Society of Dental Surgeons (ASDS) and required its members to sign a pledge promising to not use amalgam.

However, once amalgam was introduced in America, tradesmen, primarily barbers and blacksmiths, could easily make amalgam from filings of silver coins and other metals, using liquid mercury to amalgamate the mixture of metals, creating a soft pliable plug that could be quickly and easily tamped into a hole in a tooth. The amalgam quickly hardened into a strong resistant substance which could withstand the rigors of chewing. Amalgams were sold to the common man as an inexpensive method to save teeth and its installation was relatively painless.

Some medical dentists saw the advantages of amalgam. It was inexpensive, easy to use and broadened the potential patient base. Ultimately, dissident medical dentists and tradesmen-dentists formed a competing dental trade organization in 1859 which is now known as the American Dental Association (ADA). The ASDS faded away and with it, the vocal concerns about mercury-based dental fillings.

The use of amalgam was founded in controversy and continues to the present. Up until 1986, the ADA and its member dentists asserted that the mercury in amalgam, when combined with its constituent metals, was inert, did not expose patients to any mercury and was not a source of health harm.4 However, as early as the 1860’s, medical doctors were making a link between amalgam fillings and specific health harm. A lecture by William P. Wesselhoeft, MD, Boston, MA, on his clinical experiences was written up in an 1896 edition of the International Hahnemannian Association Transactions. It included a post-lecture discussion with other doctors about their similar experiences.

The connections these doctors made between health harm and amalgams was unequivocal and included: tongue ulcers (“I firmly believe the ulcer was caused by the contact with the filling.”) chronic gastritis (“The result of the removal of the fillings was a perfect, and permanent cure of his chronic gastritis.”); tinnitus (“The tinnitus she says is now ‘so far off’ that she scarcely hears it); disfiguring eczema (“…his mother sent me this message: ‘The Lord be praised that our son is again presentable through your ministrations.’”); chronic rheumatism (“I have relieved chronic rheumatism many times after having the mercurial amalgams removed, and I think this is the experience of a great many in our profession.”); and, follicular pharyngitis (“…follicular pharyngitis, and many other affections of the throat, post-nasal catarrh, etc., are practically incurable until these amalgam fillings are removed.”). 5

One theme that is common for patients with mercury amalgam poisoning is the difficulty of finding a diagnosis for their wide-ranging maladies. Medical doctors are not trained to look to dental materials as a source of health problems and dental consumers have little knowledge about the composition of fillings being placed in their mouths. Patients don’t ask about them and dentists don’t volunteer the information even though the doctrine of “informed consent” requires such a discussion.

A February 2006 Zogby poll on mercury amalgam dental fillings revealed that 76% of Americans are unaware that mercury is the primary component of amalgam fillings. 92% are of the opinion that dental consumers should be informed of the available alternatives.6

How have American dental consumers been kept ignorant of the existence of toxic mercury in dental fillings for over 170 years? Several factors play a role. While it isn’t clear if the ADA coined the phrase “silver fillings,” it is clear that the term is the descriptor of choice by the ADA and most dentists. The ADA’s website and its brochures, which are sold to dentists for distribution to patients, consistently refer to these fillings as “silver fillings” or as “dental amalgam,” but never as “mercury fillings.”7 Consumers in states like California and Maine, which have passed laws requiring dentists to provide patients with documents disclosing the mercury content of amalgam, have spent years wrangling with the dental boards and dental associations for honest documents. Arizona and New Hampshire have passed such laws, but have failed to enforce them to date.

The ADA has taken affirmative steps to prevent dentists from informing their patients about the existence of or the risks of mercury in dental fillings. The ADA, in 1990, adopted an Ethical Rule (5A), which prohibits dentists from removing amalgam,

“for the alleged purpose of removing toxic substances from the body when, performed solely at the recommendation or suggestion of the dentist … [because it] is improper and unethical.”8 A number of state dental boards have adopted these ethics rules. The effect has been to intimidate dentists from talking at all about amalgams for fear that any statement critical of the dental material might imply a recommendation for removal.

The Oregon Board of Dentistry has not adopted the ADA’s ethical rules, but it did adopt a written policy on amalgam that was even more punitive. Oregon law provides that a dentist can be disciplined, including loss of license, for commission of a fraud against a dental consumer. The amalgam policy deemed it a fraud for a dentist to recommend the removal of an amalgam for the purpose of removing a toxin. Actions by the Oregon ACLU resulted in the rescission of this policy in March 2003.9

The most effective tool of state dental boards to keep dentists from warning patients about the dangers of mercury amalgams is the disciplinary process that has been used against mercury-free dentists with the encouragement and support of the ADA. Mercury-free dentists have been disciplined, and even lost their licenses to practice, for practicing mercury-free dentistry, for advertising their mercury-free practices, for publishing articles or lecturing about mercury-free dentistry. These actions by state boards have had the effect of imposing a “gag order” on mercury-free dentists, preventing them from performing their fiduciary duty to inform their patients of the risks of treatments and the alternatives available.

The Oregon Board of Dentistry investigated four mercury-free dentists in 2005 for producing an “infomercial” on mercury-free dentistry which aired multiple times on a Portland Metro area network station, but, after receiving a lengthy, detailed response, dismissed the matter. And, in 2006, the Board investigated one of those same dentists for advertising his practice in Portland Monthly magazine; a matter that is still pending. These actions by the Board are effective at keeping other mercury-free dentists from speaking out for the fear of bearing the costs to defend the investigations and the risk of losing their right to practice their profession.

While the ADA is providing dentists with brochures to give to patients to calm their concerns about the safety of amalgams,10 the amalgam manufacturers are placing inserts with their product that warn dentists of health risks from amalgam. For example, in 1997, Dentsply, a leading amalgam manufacturer, disclosed that amalgam is a neurotoxin (toxic to the brain and central nervous system), a nephrotoxin (toxic to kidneys) and a lung and skin sensitizer. Further, the manufacturers warned against the use of amalgams in certain vulnerable populations, including pregnant women, children six and under, people with kidney disease and people with mixed metals in the mouth. 11

In response to pressure from the ADA, Dentsply revised this product warning document, explaining that the wording was necessary to comply with German labeling requirements and the purpose of the revision deleting the warning was to assure that the “contraindications and warnings are consistent with accepted scientific information,”12 i.e. German citizens are entitled to warnings but Americans are not. This is yet another way the ADA assures that Americans do not know about the risks of mercury in dental fillings.

There is a very real risk to mercury-using dentists if they keep following the ADA’s “cone of silence” about the mercury content of amalgams and health risks associated with them. David Barnes, a dentist in Tennessee, sued Kerr Manufacturing, an amalgam manufacturer, for mercury poisoning from use of Kerr amalgams in his practice. In 2005, the federal Sixth Circuit Court of Appeals, affirming the trial court’s dismissal of the case, found that the product warning sufficiently notified Barnes that mixed dental amalgam was dangerous.

The Court noted, “the label on each jar of dental amalgam capsules featured not only a skull and crossbones next to the word ‘Poison,’” but also a list of illnesses, including “bronchiolitis, pneumonitis, pulmonary edema [and] redness and irritation to [the] eyes and skin.” Likewise, the Court noted, the MSDS (material safety data sheet, provided to all dentist-buyers) warned that chronic mercury exposure could lead to “nervous irritability, weakness, tremors, gingivitis, erythrism and graying of the lens of the eye.” Further, the Court ruled that the other ingredients mixed in amalgam with the mercury – silver, copper and tin – are not claimed by the manufacturer to “neutralize the danger while the dentist is working with the product.” 13

Dr. Barnes admitted that he was aware of mercury’s toxicity, but testified that in dental school, he was taught that mixed dental amalgam was safe and the mercury rendered inert by mixing it with other metals. That evidence carried no weight with the court and that should give all dentists pause. Not only because they have no recourse if they are harmed by their exposure to mercury, but because those same warnings that protected Kerr are not given to dental consumers.

Under the “learned intermediary” doctrine, the manufacturer could also be insulated from liability cases brought by dental consumers. That doctrine is based on the assumption that a medical/dental professional, in fulfillment of his fiduciary duty to his patient, will pass along manufacturer’s warnings and any other information a patient would want to know about treatments and their risks before giving consent for treatment. In defense of a lawsuit, the manufacturer would assert that its duty is complete upon warning the dentists; the warnings to patients must come from the “learned intermediary” – the dentist. Furthermore, the Court’s opinion provides a direct challenge to the ADA’s proclamations of amalgam safety. By implication, the court found that amalgam carries a health risk and warnings were required, and then it found that the warnings were adequate.

Thus, dentists are placed in a classic Catch-22: if the dentist fails to warn patients of the risks of mercury in amalgam, he faces potential liability for health harm; and, if the dentist gives such warnings, she faces risk of discipline by the state dental board, including possible loss of her professional license to practice.

What is the evidence that supports the ADA claim of safety for amalgam or the mercury-free activists’ claim of health harm? The ADA states:

The strongest and most convincing support we have for the safety of dental amalgam is the fact that each year more than 100 million amalgam fillings are placed in the United States. And since amalgam has been used for more than 150 years, literally billions of amalgam fillings have been successfully used to restore decayed teeth. 14

Thus, the ADA’s proof of safety is its assertion that because amalgam works to restore teeth, it is safe.

As of April 2006, the ADA additionally points to an $11 million National Institute of Dental and Craniofacial Research (NIDCR) study which compared the adverse health effects of amalgam fillings in children, with adverse health effects in child-subjects who received non-amalgam fillings. One branch of the study was conducted with 500 low income children from New England and the other branch with 500 children attending Casa Pia schools in Lisbon, Portugal.

These studies, known as the Children’s Amalgam Trials (CAT), were published in the April 19, 2006 issue of the Journal of the American Medial Association (JAMA). The trial investigators concluded that there were no significant differences in the target health measures between the subjects with amalgams and those without. 15

These studies are controversial. The federal Office of Human Research Protection is conducting an investigation looking at the adequacy of the Informed Consent forms, which did not disclose to the Casa Pia guardians that amalgam contains mercury; the impact, if any, of the sex abuse scandal at the Casa Pia schools that lasted three decades and was discovered during the pendency of the trials; and, issues related to bias and conflicts of interest of the researchers. Other researchers are seeking the data compiled by the University of Washington researchers, who conducted the Casa Pia trial for further evaluation.

In the same issue of JAMA, an editorial by Herb Needleman, MD, was published, commenting on the CAT, and urging caution against reading too much into the studies. He mentions that the trials were too short to assess the long term effects of the children’s exposure to the neurotoxic mercury. The New England branch of the studies was a 5 year study and the Casa Pia branch was a 7 year study. Dr. Needleman points out the weaknesses and limits of the studies and warns that:

With the application of better epidemiological designs and more robust statistical methods to investigate toxicity, the usual consequence is uncovering effects at lower thresholds. The trajectory of discovery of … lead has followed this path … and may offer insight into the future path that mercury investigations may follow. 16

Twenty years ago Dr. Needleman was on the forefront of the warnings on lead thresholds, warning that the so-called safe levels were set much too high. It is now understood that there is no safe level of lead exposure for the developing brain.

One peer reviewed study by H.L. Schubert, 17 published in the Journal of Toxicology and Environmental Health in 1978, tested the relative amounts of lead and mercury which would kill 1% of rat subjects. The amount of lead resulting in a 1% lethal dose (LD) was 280 micrograms of lead per kilogram of body weight. And for mercury it was 7 micrograms of mercury per kilogram of body weight, i.e. 1/40 th as much. But what was revolutionary in this study was that the synergism of the two neurotoxins were tested and it was found that a combination of 280 mcg pb/kg (1LD) added to 7 mcg hg/kg (1LD) killed 100% of the rats (100 LD). This is synergistic toxicity which makes it impossible to define a “safe” level of mercury.

In 2002, Kazantzis looked at 40 years of peer reviewed literature to determine whether there was any safe level of mercury exposure. He concluded:

As mercury can give rise to allergic and immunotoxic reactions which may be genetically regulated, in the absence of adequate dose-response studies for immunologically sensitive individuals, it has not been possible to set a level for mercury in blood or urine below which mercury related symptoms will not occur. 18

Dr. Needleman, in his JAMA editorial, indicated that he also understands the political use of studies like the CAT. He states:

It is predictable that some outside interests will expand the modest conclusions of these studies to assert that the use of mercury amalgam is risk free. This conclusion would be unfortunate and unscientific.” 19

In fact, the ADA has made such an assertion and has waged a nationwide public relations campaign to continue to mislead the public on this issue. The title of an article on the ADA’s website says it all: “Two New Clinical Studies Support the Safety and Use of Dental Amalgam in Children.” 20

In contrast, mercury-free dentistry activists point to thousands of peer-reviewed scientific journal articles, some of which conclude that mercury vapor is not inert, it is emitted from amalgams in excess of government safety limits; that 80% of it is absorbed into the lungs; that certain subsets of the population with certain genetic markers are more vulnerable to harmful effects; that the harm includes, among many other types of harm, measurable neurological and neurobehavioral deficits; that specific health harm to dentists and dental personnel have been linked to their exposure to amalgam; and, that safe removal of amalgam with biological detoxification resulted in significant improvement of adverse health conditions. See:;www.iaomt.org

The use of mercury amalgam in back teeth (molars) is considered the “standard of care” by the ADA, its constituent state dental associations, state dental boards and dental insurance reviewers. All American and Canadian dental schools must teach the placement of amalgam fillings as part of its curriculum. The ADA, through an alter ego, the American Dental Education Association, which is headquartered with K Street lobbyists in Washington D.C., accredits all dental schools. This is an educational monopoly structured to support the continued use of mercury in dental fillings.

However, for decades, some dentists have been making a decision to practice dentistry without using mercury. They say they do it for the safety of their patients, their staff and themselves. In the early days of mercury-free practice it was challenging to find satisfactory alternative materials for back teeth. There are now many safe and effective alternatives to mercury amalgam. According to the Christensen Research Institute, the number of dentists with a mercury-free practice was 3% in 1985; it tripled to 9% in 1995; and, more than tripled again to 28% in 2001. It is estimated that mercury-free dentists are now one-third of practicing dentists.

The ADA points to the poor characteristics of non-mercury fillings and claims that amalgam is the only material that can be used for some applications. The ADA also asserts that the alternatives do not last as long, have to be replaced more often and are more expensive because they take more time to place. However, metal fillings expand more than the alternatives and can crack teeth leading to crowns, root canals, and loss of teeth, jaw bone infections and periodontal disease. Even the California Dental Association will admit that use of amalgam results in the removal of healthy tooth structure to accommodate the filling. 21

Other countries have faced the controversy over the use of mercury amalgam dental fillings and many of them have taken some kind of action to limit their use. Some examples include: Health Canada ( Canada’s FDA equivalent) has advised that children 6 and under, and pregnant women not receive amalgams. Sweden does not reimburse the cost of placing amalgams. In 2002, Mats Berlin, formerly the World Health Organization’s leading expert on mercury toxicity, was given the task of evaluating dental amalgam. On April 25, 2003, a report was published and concluded that amalgam hazards were being underestimated. Dr. Berlin, in speaking about the report stated:

“I think that amalgam as soon as possible should be banned in the whole European Union. Every medical doctor and dentist should consider whether mercury from amalgam could be a contributing factor when they meet patients with unclear diseases and diseases which involve the immune system.” 22

Norway advises that all alternatives to amalgam be considered first. Japan has stopped teaching the placement of amalgams in its dental schools. The U.S. stands out for its failure to have any federal limits at all on the use of amalgams. The ADA is urging the FDA to classify amalgam as a Class II medical/dental device (safe with labeling that warns of its zinc content, but not its mercury content) and to preempt all state law limitations on amalgam.

The term “mercury-free dentistry activists” refers to individuals, including those who have been harmed by mercury amalgam, environmental groups that support efforts to keep mercury out of the environment, Dental Amalgam Mercury Syndrome, Inc, (DAMS), a support group for mercury poisoned dental consumers, mercury-free dental associations and Consumers for Dental Choice, a national tax-exempt non-profit established in 1996 by consumer advocates, which is headquartered in Washington D.C.

Consumers for Dental Choice is lead by Charles G. Brown, former state Attorney General of West Virginia, and its goal is to ban the use of mercury in dentistry, to create a fair playing field for mercury-free dentists and to educate the public about the health hazards of amalgam. Mr. Brown is conducting a national campaign to expose the deceptive practices of the American Dental Association (ADA) and state dental organizations and the illegal refusal of the FDA to regulate mercury amalgam. He is also legal counsel for the Coalition to Abolish Mercury Dental Fillings, the lobbying arm of the movement.

Since the organization began, the number of amalgams placed has declined dramatically, from two-thirds of all fillings placed to one-third, and the number of mercury-free dentists has grown dramatically, but abolition of mercury in dentistry remains its primary goal. The methods to accomplish this goal include:

(1) educating consumers and legislators on federal and state legislation that requires dentists to obtain informed consent from dental consumers, institutes immediate bans on use of amalgam in vulnerable populations and, ultimately, completes the ban on mercury-based fillings for all others;
(2) educating consumers, legislators, health officials and the media to promote the full disclosure of the risks associated with mercury amalgam fillings, to encourage the free flow of non-deceptive information between dentists and patients, which includes efforts to end the American Dental Association’s notorious “gag rule” which tries to silence mercury-free dentists;
(3) monitoring research relied upon by federal agencies to be certain that it is based on sound science and engaging experts to counter studies by non-independent or unqualified researchers that urge continuation of amalgam for spurious reasons such as “it’s good because we’ve used it for 150 years,” or “a mixture of amalgam is similar to the combining of sodium and chloride to make table salt;”
(4) educating, petitioning and filing lawsuits against the FDA to urge it to fulfill its statutory duty to protect consumers from the harmful effects of amalgam, an unapproved dental device;
(5) recruiting and promoting mercury-free dentists as nominees for appointment to the state dental boards of the individual states;
(6) supporting and defending mercury-free dentists who are targeted by state dental boards for the purpose of suppressing competition; and
(7) filing lawsuits to enforce laws regulating mercury and/or mercury amalgam which are not being enforced.

The disconnect between the facts and journalistic accuracy on the issue of mercury amalgams exists because the ADA is considered the authoritative source on all things dental. Many writers do not fact check the ADA. The best evidence of the success of ADA’s tactics is the 170 years of continual use of dental amalgam.

The Choice of JAMA for publication of the CAT reports may continue to mislead medical doctors into thinking that mercury in dental fillings cannot be considered a source of adverse health conditions; their colleagues over a hundred years ago were more aware of the toxicity of amalgam. The CAT studies were conducted to protect the economic interests of dentists, not to test the safety of a beneficial dental device, for which many excellent alternatives already exist. The controversial studies and the controversial results are just the most recent volley in a 170 year battle to convince the public that a known neurotoxin isn’t toxic. An industry that depends for its livelihood on an embargo of legally and morally required consumer information does not have a bright future in the Information Age.

The Precautionary Principle clearly steers consumers away from mercury dental products, including amalgam, because safer alternatives are available and eliminates an unacceptable risk to human health and to the environment.

August 7, 2006

Sandra Duffy, J.D.
Board President, Consumers for Dental Choice
Lake Oswego, OR
503-603-9333 home
503-988-3138 work

WHO, Criteria #118, p.36 (1991).

Clarkson, Thomas W., Element of Mystery , Environmental Health Perspectives. (EHP) Vol 110. Suppl 1. pp 11-23. 2002. (Dentists maintain that mercury in "amalgam becomes inert once the fillings have been allowed to set for several days, and that long-term danger to the patient from [mercury] vapor is therefore remote.”)

See for example: Answers to your questions about Silver Fillings, A Safe, Affordable Option in ToothRestoration, ADA, Chicago IL, 2000.

Oregon govt. - President's Message, by Jean Martin, DDS, MPH Vol. 17, No. 2 June 2002

10 Answers to your questions about Silver Fillings, A Safe, Affordable Option in Tooth Restoration,ADA, Chicago, IL, 2000. The factual information in this patient brochure, used to calm concerns of dental consumers about the use of mercury in dental fillings, is contained in a scientific rebuttal prepared by the International Academy of Oral Medicine and Toxicology, a mercury-free dental association. See,




14 Journal of the American Dental Association (April, 1990).

15 Bellinger DC, et al, Neuropsychological and renal effects of dental amalgam in children: a randomized clinical trial. JAMA. 2006 Apr 19;295(15):1775-83; DeRouen TA, et al,Neurobehavioral effects of dental amalgam in children: a randomized clinical trial. JAMA. 2006 Apr 19;295(15):1784-92. 

16 Needleman, HL, Mercury in dental amalgam--a neurotoxic risk? JAMA. 2006 Apr 19;295(15):1835-6.

17 Schubert, J., et al Com bined effects in toxicology--a rapid systematic testing procedure: cadmium, mercury, and lead. , J. Toxicol Environ Health, 1978 Sep-Nov;4(5-6):763-76.

18 Kazantzis G, Mercury exposure and early effects: an overview, Med Lav. 2002 May-Jun;93(3):139-47.

19 See note 16.