Dental amalgam controversy

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

The controversy concerns the propriety of the use of dental fillings containing mercury. Dental amalgam is a mixture, rather than an alloy, of mercury along with other metals like silver, tin, copper, and zinc. Cadmium, indium, palladium and lead have historically been found in some amalgam products. ^*^*^* Amalgams have been used in dentistry for over 150 years because they are malleable, durable, and more affordable than gold or composites.

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. Critics argue that mercury can and does leak into the body via amalgams ^*," target="_blank" >and that long-term exposure to the low levels of mercury vapor causes neurodegenerative diseases, birth defects, and mental disorders. Aside from the defense of the use of mercury in vaccines surrounding the thimerosal controversy, an overwhelming majority of experts acknowledge the danger of high concentrations of mercury in any form. Both sides of the dental amalgam debate agree that the heavy metals contained in amalgam may cause an allergic reaction in mercury-sensitive individuals. As the use of amalgam is steadily declining in favor of more natural looking and less controversial composite resin materials, the issue may eventually become moot.[http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=16393132&query_hl=4&itool=pubmed_DocSum

History and overview

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. The Chinese were the first to use a silver amalgam to fill teeth in the 7th century. In 1816, Auguste Taveau developed his own dental amalgam from silver coins and mercury. This amalgam contained a very small amount of mercury and had to be heated in order for the silver to dissolve at an appreciable rate. Taveau's formula offered lower cost and greater ease of use compared to existing material such as gold, but had many practical problems, including a tendency to significantly expand after setting. Because of these problems, this formula was abandoned in France. In 1833, however, two Europeans, the Crawcour brothers, brought Taveau's amalgam to the United States under the name "Royal Mineral Succedaneum". They set up an elegant, well appointed office in New York and began aggressively advertising their practice, claiming to be able to completely and painlessly restore a tooth in just two minutes. Despite their lack of any formal qualification and their substandard methods - they were known to leave the bulk of the decayed portion of the tooth intact, counting on the liquid amalgam to kill any infection - their practice thrived and they were soon attracting many wealthy clients from the area's best dental practices. Their success attracted a great deal of attention.^*

Most dentists with medical training, who treated wealthier patients able to afford the more expensive gold fillings that were in use at the time, were outraged to find their patients turning to two unqualified opportunists using untested and potentially dangerous materials. Dr. Chapin Harris, who in 1840 co-founded the first dental school in the US, the Baltimore College of Dental Surgery, said in his opening address: "It is one of the most objectionable articles for filling teeth that can be employed, and yet from the wonderful virtues ascribed to this pernicious compound by those who used it, thousands were induced to try its efficacy". However many dentists, including the more affordable craftsman-dentists who were usually trained in trades such as carpentry or metalwork, and mainly handled extractions, reacted differently. They saw in the new amalgam a filling material that even the poor could afford, which required less skill to use than gold, as evidenced by the financial success of the untrained Crawcours, and so began to adopt amalgam in their own practices.

Also in 1840, the American Society of Dental Surgeons, was founded in New York. It was the only official organization of dentists in existence at the time. In 1845, the ASDS 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, dentists made amalgam by mixing liquid mercury and the other components of amalgam themselves in their office, a practice which continued until pre-filled amalgam capsules became generally available in the 1960's.^* Because of this, it was feared that dental offices were often contaminated with unsafe levels of mercury. During the next decade some members of the society were suspended for the use of amalgam. Because of its stance against dental amalgam, membership in the American Society of Dental Surgeons declined, and due to the loss of members, the organization disbanded in 1856.

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

Amalgam formulations and properties were gradually improved, notably by Dr. G.V. Black in 1895. Despite these changes, controversy over the use of amalgams persisted in the dental profession. The ADA maintained until 1984 that mercury was bound in amalgam and did not release mercury vapor. In the 1970's numerous studies demonstrated that a small amount of mercury vapor was constantly being released from amalgam, corroborating the first such study published in 1882 in the Ohio State Journal of Dental Science by Dr. Eugene S. Talbot.^*

The majority of dentists claim that dental amalgams are not only safe for use but desirable, since they are cheap, easy to use, fairly durable and strong, can be quickly inserted into the oral cavity and that any release of mercury vapor is too negligible to be an issue. Opponents, however, argue that repetitive exposure to a very small amount of mercury can be cumulative, so amalgams can cause many diseases, and that there are many alternative filling materials which can easily be used instead of amalgam.

Regulation and governmental involvement

Some legislators have introduced legislation to prohibit or restrict use of amalgam 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 countries, such as Japan, Norway, and Sweden, have banned or stringently regulated the use of mercury in dental amalgams, citing health concerns. The Swedish Chemicals Inspectorate (KemI) maintains a web site containing a report on the investigation for a general ban on mercury on which it states, "KemI judges that there are strong grounds for banning amalgam for environmental reasons. From a health point of view there is every reason to apply a precautionary approach."^* Some countries, notably Austria and Germany, have some restrictions on dental amalgam, such as permitting its use for the general population, but not for children, pregnant women, people with kidney problems, when in contact with other metals, such as braces, and in people with mercury sensitivity.

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, which tabled. It has since been re-introduced as bill HR-4011 by congresswoman Diane Watson ^*.

In most European countries (for example, the United Kingdom, France, and Italy) and the United States, amalgam use is unrestricted. In the United States, amalgams are classified as a "device," not a "substance," by the Food and Drug Administration (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 such as is required for medicines. However, the FDA maintains a web page on the use of amalgam 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."In September 2006, a joint meeting of three FDA committees will review and discuss peer-reviewed scientific literature on dental amalgam devices. [http://www.fda.gov/oc/advisory/accalendar/2006/cdrh12518dd09060706.html

Points of contention

Available alternatives

One argument against the use of amalgams in dentistry is that a number of less controversial, safer alternatives exist, like composite resin (or "white") fillings that have been available 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, though opponents point out that some newer composite materials have demonstrated durability on par with amalgam. Most of these materials, except gold which has been used longer than amalgam, have not had as long a period of use and study as amalgam, and some of them are known to contain other potentially hazardous compounds. This is one reason why biocompatibility testing is recommended for all dental materials as per ADA/ANSA or ISO standards, and can be performed by specialized laboratories.Some experts also caution against a too-sudden shift towards composite resin to allow time for dentists to acquire the skills needed to properly place resin fillings.^*," target="_blank" >and at least one school, University of Nijmegen in the Netherlands, had eliminated dental amalgam from the curriculum entirely as of 2001.[http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15193785&query_hl=4&itool=pubmed_docsum

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 classifies amalgams removed from teeth as toxic waste. They also state that not all amalgams are disposed of properly, claiming that mercury from amalgam is released into sewage water and also to air during cremation of cadavers with amalgam fillings, posing environmental risk. Proponents counter that, while mercury is bad for the environment, amalgams do not harm the environment if they are disposed of properly. The ISO has issued standards regarding the proper handling and disposal of amalgam waste, and legislation to enforce these standards is being adopted in some nations.^*

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 which are known to release mercury are a source of poison. These persons argue that amalgams can cause neurodegenerative diseases, birth defects, and mental disorders. While it is proven that mercury exposure can cause health problems such as these, the potential adverse effects of amalgam on health is yet to be resolved. Two recently released comprehensive reviews of papers published in peer-reviewed journals arrived at opposite conclusions. One released in December 2004 in the US found little evidence to link mercury fillings to health problems while the other, release in March 2005 in Germany found removal of dental amalgam leads to permanent improvement of various chronic complaints in a relevant number of patients in various trials. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15789284

Two recent randomized clinical trials in children showed no statistically significant differences in adverse neuropsychological or renal effects observed over the 5-year period in children whose caries were restored using dental amalgam or composite materials although one study could not rule out the possibility of a very small adverse effect on IQ in children with amalgam. One study showed a trend of higher dental treatment need later in children with composite. ^*" target="_blank" >Anti-amalgam groups such as the IAOMT have come to the conclusion that the above studies are poorly designed and raise ethical questions. An analysis of the data collected during these studies showed that the authors of the studies ignored the drop in mercury excretion in the urine in the children with amalgam fillings, after two years, even though the mercury exposure from amalgam remained the same or increased. According to Dr. Boyd Haley, this is evidence that these children are losing the ability to excrete mercury with increased exposure to this toxic metal.[http://www.iaomt.org/documents/CAT_Haley_response.pdf 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 from the fillings are absorbed by the body after they are placed in the oral cavity. Research on animals, including monkeys, has shown that mercury released from dental amalgam restorations is absorbed and accumulates in various organs such as the kidney, brain, lung, liver, gastro-intestinal tract, the exocrine glands ^*." target="_blank" >In a report on mercury in health care the W.H.O. stated that dental amalgam is the main source of mercury exposure in non industrialized settings, exposing the concerned population to mercury level significantly exceeding those set for food and air. Recent studies suggest that mercury may have no threshold below which some adverse effects do not occur [http://www.who.int/water_sanitation_health/medicalwaste/mercurypolpaper.pdf .

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 practitioners, particularly alternative medicine practitioners, on the other hand, disagree, and prefer the use of alternative fillings. Some practitioners may also recommend that patients with amalgam fillings have them removed and replaced, particularly if the patient is experiencing the symptoms that critics attribute to the use of amalgam.^*. These persons recommend that unprotected amalgam removal should be avoided even in routine dental procedures to avoid exposure to mercury vapor and amalgam particulate matter.

Organizations 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. One recent meta-study has concluded that after studies with methodological flaws are discounted, the evidence indicates that amalgams should not be used.

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

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