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The dental amalgam controversy is a controversy surrounding the use of dental amalgams in modern dentistry.

The controversy centers around the propriety of the use of dental fillings containing mercury. Amalgams contain around 50% mercury, along with various other metals like silver, tin, copper, and zinc. Mercury, silver and copper have bactericidal properties which explains the effectiveness of amalgam in the treatment of carious lesions. Amalgams have been used in dentistry for over 150 years because they are malleable, durable, and more affordable than gold or composites. While the American Dental Association (ADA) has supported the use of amalgam since its inception in 1859, the Food and Drug Administration (FDA) has never officially approved amalgam for use in dental fillings. The FDA maintains a web page on the use of amalgam, however, on which it states, "no valid scientific evidence has shown that amalgams cause harm to patients with dental restorations, except in the rare case of allergy.".

This statement by the FDA does not take into account more recent evidence such as the german review of scientific references up to 2005 ( Gesundheitswesen. 2005 Mar;67(3):204-16. ) which concluded that amalgam contributes substantially to human mercury load. Mercury accumulates in some organs, particularly in the brain, where it can bind to protein more tightly than other heavy metals (e. g. lead, cadmium). Therefore, the elimination half time is assumed to be up to 1 - 18 years in the brain and bones. Mercury is assumed to be one of the most toxic non-radioactive elements. There are pointers to show that mercury vapour is more neurotoxic than methyl-mercury in fish. Review of recent literature suggests that mercury from dental amalgam may lead to nephrotoxicity, neurobehavioural changes, autoimmunity, oxidative stress, autism, skin and mucosa alterations or non-specific symptoms and complaints. The development of Alzheimer's disease or multiple sclerosis has also been linked to low-dose mercury exposure. There may be individual genetical or acquired susceptibilities for negative effects from dental amalgam. Mercury levels in the blood, urine or other biomarkers do not reflect the mercury load in critical organs. Some studies regarding dental amalgam reveal substantial methodical flaws. Removal of dental amalgam leads to permanent improvement of various chronic complaints in a relevant number of patients in various trials. Summing up, available data suggests that dental amalgam is an unsuitable material for medical, occupational and ecological reasons.

Proponents state that the amount of mercury released by amalgam fillings is negligible, thus there is no danger that mercury will leak from fillings into the body.ADA. However in a recent study published in the American Journal of Forensic Medical Pathology, the authors concluded that total mercury levels were significantly higher in subjects with a greater number of occlusal amalgam surfaces (>12) compared with those with fewer occlusal amalgams (0-3) in all types of tissue. Critics argue that mercury can and does leak into the body via amalgams, and that long-term exposure to the low levels of mercury vapor causes neurodegenerative diseases, birth defects, and mental disorders. There is no debate on the danger of high concentrations of mercury in any form, and both sides agree that amalgam may cause an allergic reaction in mercury-sensitive individuals.

History, overview, and governmental involvement

For centuries, dentists have been cleaning out decay and filling cavities, using filling material such as stone chips, resin, cork, turpentine, gum, lead and gold leaf. The renowned physician Ambroise Paré (1510 – 1590) used lead or cork to fill teeth. Amalgams were the first standardized filling material. In 1816, Auguste Taveau developed the first dental amalgam from silver coins and mercury. This early amalgam contained a very small amount of mercury and had to be heated in order for the silver to dissolve at an appreciable rate.

In 1840, the only official dentist organisation in existence, the American Society of Dental Surgeons, which had promoted mercury amalgams since its inception, had members sign a mandatory pledge promising not to use mercury fillings because of fear of mercury poisoning in patients and dentists. At the time, however, dentists mixed the amalgam themselves in their office, making the office a source of poisonous levels of mercury.

In 1859, the American Dental Association (ADA) formed from dentists who wanted to continue to use amalgams. The ADA position on the safety of amalgam has remained consistent since its foundation.

As time passed, controversy over the use of amalgams became evident. Some claim that dental amalgams are not only safe for use but desirable, since it they are cheap, easy to use, fairly durable and strong, and can be quickly inserted into the oral cavity. Opponents, however, argue that amalgams can cause many diseases and can easily be replaced by non-metal fillings.

In 2001 in a lawsuit involving California Proposition 65 and amalgams, a California Superior Court judge ruled that all dental offices with more than nine employees must provide notices on the contents dental fillings to patients. The mandated notice reads:

Notice to Patients, Proposition 65: Warning on dental amalgams, used in many dental fillings, causes exposure to mercury, a chemical known to the state of California to cause birth defects or other reproductive harm. Root canal treatments and restorations including fillings, crowns and bridges, use chemicals known to the state of California to cause cancer. The U.S. Food and Drug Administration has studied the situation and approved for use all dental restorative materials. Consult your dentist to determine which materials are appropriate for your treatment.

Some legislators have introduced legislation to prohibit further use of amalgam fillings. In 2002, eight members of the U.S. House of Representatives introduced the Mercury in Dental Filling Disclosure and Prohibition Act (H.R. 4163, 107th Congress, 2nd Session, April 10th 2002), which would have prohibited any mercury in dental fillings starting in 2007. In an interim period between July 1, 2002 and 2007, the bill would have required labeling of amalgam with a warning. The bill was referred to a subcommittee and was tabled (not considered). Other countries, such as Japan, Switzerland, Norway and Sweden, have passed similar legislation.

Regulation

In the United States, amalgams are classified as a "device," not a "substance," by the FDA. "Device" modification does not need FDA approval. Under the U.S. Code of Federal Regulations, amalgams are a prosthetic device:

"Amalgam Alloy, (a) Identification. An amalgam alloy is a device that consists of a metallic substance intended to be mixed with mercury to form filling material for treatment of dental caries. (b) Classification. Class II." (21 CFR 872.3050 (2001))

As a result of this classification, amalgams have not been subject to official government testing in the United States.

Anti-amalgam arguments

Opponents of the use of amalgams in dentistry make several arguments against such use. These arguments include:

1. Available alternatives exist that do not raise the health concerns that amalgams do.
2. Because mercury is toxic to the environment, discarded amalgams are a pollutant.
3. Amalgams cause a variety of ill health effects for some individuals who have them as well as dentists who use them.

Available alternatives

One argument against the use of amalgams in dentistry is that a number of uncotroversial, safe alternatives exist. A number of composite resin (or "white") fillings have been invented since the 1980s. Other alternatives include gold, porcelain, and glass ionomers. Proponents of amalgams, however, counter that amalgams are stronger, more durable, and less expensive than most of the available alternatives. In addition these materials have not had as long a period of use and study as amalgam, and are known to contain other potentially hazardous compounds.

Environmental impact

Opponents also argue that amalgams are detrimental to the environment. These persons point out that the World Health Organization, OSHA, and NIOSH, all agree that mercury is an environmental toxin and have established specific occupational exposure limits. Additionally, they point out that, in the United States, the Environmental Protection Agency considers amalgams removed from teeth to be toxic waste. Proponents counter that, while mercury is bad for the environment, amalgams do not harm the environment if they are disposed of properly.

Health effects generally

Dental amalgams have been suspected by some medical practitioners, particularly of integrative or alternative medicine, of causing many physical and/or psychological problems. They reason that, since mercury is poisonous, amalgams in the mouth that contain mercury are poisonous. These persons argue that amalgams can cause neurodegenerative diseases, birth defects, and mental disorders.

Toxicologists have catalogued a large number of health effects caused by mercury poisoning, thus the range of possible symptoms is very diverse and all of them can be produced by other causes, making it difficult to draw definite conclusions. While most dentists acknowledge that a small proportion of patients may suffer from local symptoms due to mercury sensitivity or allergy, they would not agree with alternative practitioners who suspect a larger range of local and non-local health effects in a larger proportion of people.

Similarly, some proponents feel that the mercury contained in amalgam fillings is safer than pure mercury compounds due to the differences between pure metals and alloys. Many of the discussions on this topic have centered on whether the amalgam mixture is stable or whether any metals are released from the fillings after being placed in the oral cavity.

Various diagnostic methods exist to detect the presence of mercury in the body or the degree of mercury sensitivity, including blood tests, urine tests, stool tests, saliva tests, MELISA tests , lymphocyte sensitivity tests, DMPS or DMSA chelation urine tests, a hair analysis and others. Opinions differ on which of these tests, if any, is the most accurate, although mainstream scientific research tends to place the most weight on chelation urine tests or stool tests when trying to assess chronic levels, or on blood or urine tests when trying to assess recent acute exposure. None of these tests, however, can link mercury levels to dental amalgams, except (a) on an epidemiological scale; or (b) through measuring levels before and after dental work. Studies have investigated both angles and results have differed, fueling the controversy since the scientific data remains inconclusive and has not yet proven either safety or danger.

Most dentists, however, still feel that while, when placing the fillings, both patient and dentist are exposed to a small amount of mercury and mercury vapor, once the alloy has hardened (which takes less than a minute), most of the mercury is captured in the filling and, being bound in the alloy, cannot get out except in small amounts they would not deem significant except for the hyper-sensitive. Opponents and some alternative medicine practitioners, on the other hand, disagree, and recommend that patients with amalgams have them removed or risk serious health effects.

Organziations opposed to amalgam use, such as 'Consumers for Dental Choice', claim to have over 65,000 studies on file implicating amalgam fillings in diverse health conditions, which have been used in various lawsuits and which were the main contributing factor both to the Californian legislation concerning the issuing of warnings to patients about mercury and the federal bill introduced in 2002 proposing that amalgam fillings be made illegal after 2006. Critics have described some of these studies as scientifically invalid. The most recent meta-study has concluded that after studies with methodological flaws are discounted, the evidence indicates that amalgams should not be used.

In the United States, the National Institute of Health is currently conducting a study of the health effects of amalgams in children. The research began in 2002 and should be finished in 2006.

Health effects for dentists

Among modern dentists who are exposed to the mercury and its vapor on a daily basis, no evidence of mercury poisoning has been demonstrably proven. Some research, however, has indicated that mercury from amalgams may be affecting some dentists with mild toxicity. Dentists in several large-scale studies performed multiple cognitive and behavioural tests and, compared to a normal population, lagged behind in many areas. In one study this included 14% worse scores in memory, co-ordination, motor speed and concentration. The study did not demonstrate any link between mercury exposure and these lagging scores, however.

A study examining the health effects of mercury on dentists was done in the UK and published in the Occupational and Environmental Medicine Journal. This study found that 180 dentists had on average 4 times the urinary mercury excretion levels of 180 people in a control group. Also, dentists were significantly more likely than control subjects to have had disorders of the kidney and memory disturbance. A direct correlation between urinary mercury levels and the disability, however, was not found. The unreliability of urine test in showing lifetime of mercury accumulation rather than recent exposure has slowed down any kind of research on living humans, and the short life of animals in the classic lifetime exposure tests known as LD50 was not conductive of safety proofs in humans for chronic amalgam exposure. Thus, more research needs to be done before a solid conclusion can be reached.

External links

Anti-amalgam links

• Dental amalgam and mercury
• The International Academy of Oral Medicine and Toxicology
• Mercury free and healthy: The dental amalgam issue - A literature review from Dental Amalgam Mercury Syndrome Support Group, Inc.
• Bernard Windham on amalgam fillings
• Bio-Probe Collated study abstracts, articles, news and information from anti-amalgam and anti-fluoride group
• Consumers for Dental Choice
• Mercury Policy Project
• Quecksilber

Other links

• University of Calgary: How Mercury Causes Brain Neuron Degeneration
• US FDA statement on amalgams
• American Dental Association: Amalgam - links to news, journal articles and other resources.
• NCAHF Position Paper on Amalgam Fillings
• The Mercury Amalgam Scam: How Anti-Amalgamists Swindle People
• The Straight Dope: Are you being poisoned by your silver tooth fillings?
• Review and Analysis of the Literature on the Health Effects of Dental Amalgams
• American Cancer Society statement on amalgams

• Dentistry