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Controversy exists regarding the use of mercury in dentistry, in dental fillings. A minority of dentists has always been opposed to amalgam use but evidence of adverse effects on patients from mercury in amalgam fillings is contradictory and there remains no conclusive evidence of measurable ill-effects despite the fact that amalgam has been in use for over 150 years and continues to be the most common material used in fillings. Overall, however, its use is declining due to improving dental health generally and increasing availability of more modern alternatives. Background Dental amalgam is a mixture , rather than a true alloy, of mercury along with other metals like silver, tin, copper, and zinc.• Cadmium, indium, palladium and lead were historically 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. While it is accepted that amalgam fillings release mercury,•• it is generally argued that the amount of mercury released by amalgam fillings is negligible, thus there is no significant danger from mercury leaking from fillings into the body. Opponents of amalgam argue that long-term exposure to the low levels of mercury vapor causes neurodegenerative diseases, birth defects, and mental disorders. Experts acknowledge the risks of exposure to mercury in any form, while noting that effects of exposure to dental amalgam are not evident at the population level despite its past ubiquity. Better dental health overall coupled with increased demand for more modern alternatives such as resin composite fillings (which match the tooth color), as well as public concern about the mercury content of dental amalgam, have resulted in a steady decline in dental amalgam use, so the issue may eventually become moot.• History and overview Minority dissent over amalgam has been a stable feature of informed debate among dentists almost since its invention. In 1840, the American Society of Dental Surgeons, was founded by a group of dentists who met in New York city. It was the first national organization of dentists in existence at the time. Chapin A. Harris A.M.,M.D.,D.D.S. , who in 1840 co-founded the ASDS and 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". "At that time there were only about three hundred trained and scientific dentists in the entire country; the rest were relatively untrained operators, outright quacks, or charlatans". 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 1960s). 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 twenty-six delegates representing various dental societies in the United States at a meeting in Niagara Falls, New York. The ADA did not forbid use of amalgams. The ADA position on the safety of amalgam has remained consistent since its foundation. As of 2006, ADA has over 152,000 members and is the largest and longest-standing professional association of dentists in the world. Amalgam formulations and properties were gradually improved, notably by Dr. G.V. Black in 1895. Despite these changes, debate 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 1970s 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 maintain 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 negligible. Opponents, however, argue that repetitive exposure to a very small amount of mercury can be cumulative, so amalgams can cause health problems. 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 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. It has since been re-introduced as bill HR-4011 by congresswoman Diane Watson, who issued a public statement after the September 2006 decision of the FDA Review panel on dental amalgam. 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). 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, last updated in December 2002, 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 earlier conclusion by the FDA has now been called into question by a panel of scientists. In September 2006, a joint meeting of three FDA committees has reviewed and discussed peer-reviewed scientific literature on dental amalgam devices. Prior to the joint meeting, some scientists and consumers advocates have raised questions about the fairness of this process, as planned by the FDA. Following the meeting of the joint committees on the 6-7 September 2006, in a 13-7 vote, the advisory panel of outside advisers that the FDA had asked to assess the conclusions of it's report on amalgam safety, rejected the FDA report stating the report's conclusions were "unreasonable", given the quantity and quality of information currently available. Panelists said remaining uncertainties about the risk of so-called silver fillings demanded further research,in particular, on the effects of mercury-laden fillings on children and the fetuses of pregnant women with fillings and the release of mercury vapor on insertion and removal of mercury fillings. Michael Aschner, a professor of pediatrics and pharmacology at Vanderbilt University and a panel consultant said "There are too many things we don't know, too many things that were excluded." Shortly after the decision of the joint advisory panel, the president of the International Academy of Oral Medicine and Toxicology (IAOMT) wrote to the FDA to ask for an expanded review of current science on dental mercury amalgams, a definitive date for such a hearing, and a format that will assure that the full breadth of health effects is assessed. In a press release the ADA wrote that it " welcomes the call by a U.S. Food and Drug Administration (FDA) panel for additional review of scientific studies on the safety of dental amalgam fillings." and reiterated that "the overwhelming weight of scientific evidence supports the safety and efficacy of dental amalgam, and it should continue to be made available to dentists and their patients " and " dental amalgam contains elemental mercury combined with other metals such as silver, copper, tin and zinc to form a safe, stable alloy. " 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. Amalgams are stronger, more durable, and less expensive than most of the available alternatives, though 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 since " clinical studies on the longevity of amalgam and resin composite restorations placed by dental students and dentists who are experienced in both composite resin and amalgam placement show a comparable and acceptable annual failure rate for those restorations ". • Teaching of amalgam techniques to dental students is declining in some schools in favor of composite resin,• and at least one school, University of Nijmegen in the Netherlands, had eliminated dental amalgam from the curriculum entirely as of 2001.• Environmental impact Mercury is an environmental toxin and the World Health Organization, OSHA, and NIOSH have established specific occupational exposure limits. Amalgam removed from teeth is classified as toxic waste in various countries. Mercury from improperly disposed of amalgam may be released into sewage water. Crematoria are to establish recovery of mercury from flue gases as soon as reasonable since mercury from amalgam is released into air during cremation of cadavers with amalgam fillings. Environmental risks are mitigated provided that amalgams are disposed of properly. ISO has issued standards regarding the proper handling and disposal of amalgam waste, and legislation to enforce these standards is being adopted in some states. General Health effects 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 and neurotoxic, amalgams known to release mercury into the mouth are indisputably 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 itself on health has not yet been 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• 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. Anti-amalgam links Other links | |||||||
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