The dental amalgam controversy centers around the use of amalgam fillings in teeth. An amalgam is a mixture of metals, 50% of which is typically mercury. It has been used in dentistry for nearly 200 years because it is malleable, durable and more affordable than gold or composites. The American Dental Association has supported the use of amalgam since its inception in 1859. Proponents once thought the combination of metals in an amalgam rendered the mercury inert. This is now known not to be the case; mercury vapors do leach from fillings into the body. The severity of mercurial toxicity depends on the form and length of exposure.

The ADA's position states that the amount of mercury released by amalgam fillings is negligible (ADA). As of December 2002, FDA investigations reported that, "no valid scientific evidence has ever shown that amalgams cause harm to patients" (FDA) Critics associate long-term exposure to the low levels of mercury vapor with neurodegenerative diseases, birth defects, and mental disorders. Dental offices in California have posted a warning that amalgam contains mercury, "a substance known to cause birth defects and other reproductive harm," since 2003, and a statewide ban on dental amalgam goes into effect in 2006 (Consumers for Dental Choice). 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 of dental amalgam

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 Pare (1510-1590) used lead or cork to fill teeth. Amalgams were the first true standard filling material. The first people to use amalgams to fill cavities appear to be the French. In 1816 Auguste Taveau developed the first dental amalgam from silver coins and mercury. This early amalgam was low in mercury and had to be heated in order for the silver to dissolve at any appreciable rate. Modern dental amalgams are mixed cold.

Appearance

One obvious disadvantage of using amalgams for fillings is they look unattractive. The material is black (silver if an abrasive toothpaste is used) and can clearly be seen on, and sometimes behind, a tooth. For this reason, amalgam fillings are seldom used in the front teeth. They are, however, still very popular for use in the back teeth, especially since dental amalgams are generally considered to be tougher wearing than composite fillings.

This assumption has been challenged, since the number and type of composite (or "white") fillings available has been rapidly growing since the 1980s. For the first time in history there are competitors to amalgam, such as the 'Diamond' range of composites, which according to one comparative study were demonstrated to be superior to amalgams in terms of toughness, rate of corrosion ('wear'), three different measures of strength and other measurements. Other more commonly used brands of composite also compared favourably in some aspects, but not in others.

History of controversy

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. It must be noted that in 1840 dentists mixed the amalgam themselves in their office, making the office a source of poisonous levels of mercury.

The American Society of Dental Surgeons however claimed amalgams were toxic in the mouth and should be removed. Such claims have been controversial for over a century because the removal exposes the patient to abundant mercury vapors unless special precautionary measures are employed. These measures cannot eliminate exposure to mercury vapors but can nowadays minimize it. They may include the use of an oxygen mask, rubber dam , extensive rinsing, high volume suction, cutting and sectioning the filling rather than drilling it all out, and other precautions.

In 1856 the American Society of Dental Surgeons disbanded because dentists who supported the use of amalgams deserted the ASDS ranks until it had too few members to exist.

In 1859 the American Dental Association (ADA) formed from dentists who wanted to continue the use of amalgams. Their position is that amalgams were proven to be completely safe and leaked no mercury at all. No such proofs existed in 1859, because the scientific methods of medicine in 1859 were not as advanced, and toxicity of amalgams or exposure to the mixing process could not be proven or disproven. Therefore, no substantial medical studies were funded. The ADA position on the safety of amalgam itself never changed.

Controversy has never disappeared on this subject, with ardent views on both sides, but the mainstream view in most countries (with some exceptions such as Japan, Switzerland, Norway and Sweden) has since 1859 maintained that dental amalgam is not only safe for use but desirable, since it is cheap, easy to use, fairly durable and strong and, above all, fast to insert into the oral cavity, and hence more profitable than alternative materials which need to be layered in and so take longer to place in general.

This controversy has returned to the limelight since new legislation in California and Connecticut was passed to illegalise use of amalgam fillings in future. In California, the so-called Mercury in Dental Filling Disclosure and Prohibition Act (Bill H.R. 4163, 107th Congress, 2nd Session, April 10th 2002) prohibited the purchase and use of any dental amalgam material in the State of California after 2006. In the transition period, all amalgam fillings were, by law, only to be offered to consumers in California (if not under 18, pregnant or lactating) with a warning stating that mercury contained in them was "highly toxic" and that amalgam "poses health risks". This act was both condemned and acclaimed by many people on both sides of the controversy, but was nevertheless passed into American law.

Composition

In 1895 the multitude of formulas for making amalgam were standardised:

The gamma-2-phase amalgams contain approximately equal parts 50% of liquid mercury and 50% of an alloy powder containing:

• > 65% silver (Ag)
• < 29% tin (Sn)
• < 6% copper (Cu)
• < 2% zinc (Zn)
• < 3% mercury (Hg)

Around 1970, the ingredients changed for manufacturing cost reasons to the new non-gamma-2 form:

The gamma-2-free amalgams (sometimes referred to as "high-copper" amalgams) contain approximately equal parts 50% of liquid mercury and 50% of an alloy powder containing:

• > 40% silver (Ag)
• < 32% tin (Sn)
• < 30% copper (Cu)
• < 2% zinc (Zn)
• < 3% mercury (Hg)

The possible difference in toxicology between the two has not been studied conclusively. Around the late 1970s, the gamma-2-free amalgam became common. The leaking of poisonous substances other than mercury, or of combined compounds of the various metallic components, has less often been the subject of tests than mercury on its own, which further adds to the lack of conclusive data.

Regulation

This change in the amalgam formula was introduced without having to undergo FDA approval because amalgams are classified as a device, not a substance. Device modification does not need FDA approval. As far as the U.S. Code of Federal Regulations is concerned 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)).

This prevented amalgams from undergoing the testing which had been used for all other dental materials invented since.

Environmental impact

Most modern governments claim that certain fish in excess quantities are unsafe due to methyl mercury levels (death has been known to occur from mercury contaminated fish). The warnings especially target pregnant women. Larger species of fish, such as tuna or swordfish, are usually of greater concern than smaller species, since the mercury accumulates up the food chain.

The increasing concern over the presence of methyl (organic) mercury in fish can be attributed to industrial pollution. The World Health Organization, OSHA, and NIOSH, all agree that mercury is an environmental poison and have established specific occupational exposure limits.

Mercury enters the environment as a pollutant from various different industries, since it has been applied to many different uses, such as:

• dentistry
• steel, phosphate & gold production
• gold extraction
• metal smelting
• use in photo-engraving, textile printing, dye manufacture, bronzing of field-glasses, anti-fouling paint in ships, tool-hardening processes, wood pulping, chloralkali industry, electrodes and reagents
• medical applications, including vaccinations (thimerosal preservative used in DPT, influenza and others), ophthalmic solutions/ointments/suspensions, diuretics, nasal drops/sprays/mists/decongestants/spray pumps, haemorrhoidal ointments/suppositories, mumps skin test antigen, adrenal cortex injections, allergen patch tests, testosterone injection suspension, antibiotic ear suspensions, fungizone lotion/cream, tissue fixatives, throat lozenges, hair tonics
• laboratory work involving mercury or sulfur compounds
• manufacture & repair of barometers, ultraviolet lamps, direct-current electric meters, batteries, radio valves, strip lamps & mercury thermometers
• cosmetic industries, including in the making of some brands of mascara, contact lens solution, contraceptives, spermicides, disinfectants, hair dyes and skin-lightening creams

The Environmental Protection Agency has declared amalgam removed from teeth to be toxic waste. Even the American Dental Association warns that amalgam filling material is hazardous to dental office personnel before and after its presence in patients' mouths.

Environmental Health Criteria 118, a report prepared by Dr Lars Friberg, Karolinska Institute, Sweden, and published under the joint sponsorship of the United Nations Environment Programme, the International Labour Organisation and the World Health Organization, in Geneva, 1991, concluded that amalgam fillings constitute the main average exposure risk to humans (3 to 17mcg), exceeding fish and seafood (2.3mcg), other food (0.3mcg), air and water sources combined.

Amalgams and Alternative Medicine

Mercury amalgams have been suspected by some practitioners of integrative or alternative medicine of causing many (often multi-systemic, vague) physical problems. They reason being that, since mercury is poisonous, so must be anything containing mercury; hence, amalgams are poisonous. This argument however ignores the difference between a metal and an alloy.

Many of the discussions on this topic have centered, historically, on whether the amalgam mixture is stable, or whether any metals are released from the fillings after being placed in the oral cavity. This focus has in recent years shifted to discussing whether the amount released is significant or not. Some integrative and alternative practitioners claim that it is, while mainstream dental authorities, physicians, and chemists maintain that it is too minuscule to matter.

Various diagnostic methods exist to detect the presence of mercury in the body, 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 best, 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 be linked specifically to mercury of dental origin, except (a) on an epidemiological scale; or (b) through measuring levels before and after dental work. Studies have been attempted to investigate both angles, and results have differed, again fueling the controversy on both sides, since the scientific data remains inconclusive and cannot prove either safety or danger.

Nevertheless, alternative practitioners, in some cases with tests and in others without, sometimes recommend their patients to consider removing their dental fillings, saying they suspect mercury poisoning from them.

Some dentists point out that while there is no denying that, 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), the mercury is captured in the filling and cannot get out, it is bound in the alloy.

Conventional authorities maintain that no medical research has yet provided any conclusive evidence of significant physical problems caused by amalgam fillings. Legal bodies such as 'Consumers for Dental Choice', however, claim to have over 60,000 valid studies on file implicating amalgam fillings in diverse health conditions, which have been used in various lawsuits, and which were the main contributing factor to the bill passed in California in 2002 illegalising amalgam fillings from 2007. 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 amalgam should not be used.

Among modern dentists who are exposed to the mercury and its vapour on a daily basis, no evidence of mercury poisoning has been demonstrably proven. However, some recent research is showing 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, and in others an increased rate of cancer, depression, irritability, chronic fatigue, headaches, tremors, arthritis, infertility and miscarriages.

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. But a direct correlation between urinary mercury levels and the disability was not found. More research needs to be done before a solid conclusion can be reached. The unreliability of urine test in showing lifetime of mercury accumulation rather than recent exposure (and unreliability to measure recent exposure in autistics) 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.

Alternative dentists (also known as biological, mercury-free, holistic or, in some cases, homeopathic) sometimes advise patients to have some or all of their fillings removed and replaced with composites. While they may show no evidence that amalgam fillings cause health problems, they often feel this is the case. In addition, patients often request this, as consumers, whether or not they have received any advice.

Removing all of them at once can cause problems. For this reason, when biological dentists remove fillings, the vast majority follow set protocols which include sequential removal, usually of no more than two fillings at one time, or one quadrant.

Any time a filling is drilled out, there is always a risk that the drill will remove too much tooth material, requiring the tooth to be restored with a cap. Another risk is that the dentist may drill too far, hitting the pulp and causing an infection, subsequently requiring the tooth to be treated with a root canal. Removal can involve drilling into the amalgam so more vapors are released than in putting them in.

The alternatives to amalgam fillings usually selected are composites. If the brand of composite is chosen carelessly, they do have drawbacks; they may have to be replaced more often, again causing risk of tooth damage or infection during replacement. However, there are now many different brands available, and the number continues to increase with new research. Those dentists who keep up to date with the latest developments are therefore often aware of which composite materials may be comparable to, or even superior than, amalgams in terms of durability and strength.

For the same reason, the main contention of alternative dentists is that these are now becoming safe, cheap alternatives to amalgam for normal dental practice. In California from 2007, these alternative materials will be the only option, while in countries such as Japan and Switzerland they already are. Most American dentists still maintain, however, that dental amalgam is by far the best choice of filling material in terms of many factors, such as strength, safety, durability and cost.

References

• Calhoun B. (2005, March 31). Dental amalgam and mercury. Retrieved April 05, 2005.
• Koral, S.M. (2004, September). The scientific case against amalgam. The International Academy of Oral Medicine and Toxicology. Retrieved April 10, 2005.
• Lorscheider, F.L. Vimy, M.J. and Summers A.O. (2004, March). Mercury Exposure from Silver Tooth Fillings: Emerging Evidence Questions a Traditional Dental Paradigm. FASEB Journal. Retrieved April 05, 2005.
• U.S. Food and Drug Administration. (2004, April 1). Medical devices: Dental devices. In: Food and drugs. Code of Federal Regulations. Retrieved April 05, 2005.

External links

• American Dental Association: Amalgam - links to news, journal articles and other resources.
• The Mercury Amalgam Scam: How Anti-Amalgamists Swindle People - (2004) Stephen Barrett, M.D.
• NCAHF Position Paper on Amalgam Fillings - (2002) ...statement was written in response to claims that the mercury content of amalgam fillings causes toxic amounts of mercury to enter the body. From the National Council Against Health Fraud.

• Bernard Windham on amalgam fillings Chemical engineer Bernard Windham’s extensive collection of references and information about mercury's adverse health and evironmental effects.
• Bio-Probe Collated study abstracts, articles, news and information from the authors behind the international scientific newsletter for dentists.
• Consumers for Dental Choice Regular news updates, media articles and lawyers' views on the subject of public disclosure and freedom of choice.
• The International Academy of Oral Medicine and Toxicology - a membership organization for dental, medical and research professionals who seek to promote mercury-free dentistry. Research and news articles accessible to the public.
• Mercury free and healthy: The dental amalgam issue - (2004) A literature review from DAMS, Inc. (Dental Amalgam Mercury Syndrome Support Group).

• Mercury Policy Project - works to promote policies to eliminate mercury uses, reduce the export and trafficking of mercury, and significantly reduce mercury exposures at the local, national, and international levels.