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The dental amalgam controversy refers to the conflicting views over the use of amalgam as a filling material mainly because it contains the element mercury. Scientists agree that dental amalgam fillings leach mercury into the mouth, but studies vary widely in the amount and whether such amount presents significant health risks. Estimations run from 1-3 micrograms (µg) per day (FDA) up to 27 µg/day (Patterson). The effects of that amount of exposure are also disputed. The use of mercury in dental fillings is approved in most countries. Norway, Denmark and Sweden have banned the use of mercury in dental amalgams over environmental concerns, and in Sweden's case also from concerns over its effect on human health. Elsewhere in the world, unused dental amalgam after a treatment is subject to strict disposal protocols, again for possible environmental reasons rather than for fear of direct toxicity to humans.
Those who advocate the use of amalgam point out that it is durable, relatively inexpensive, and easy to use. On average, resin composites last only half as long as dental amalgam (although modern composites are improving in strength) and dental porcelain is much more expensive. However, the gap between amalgam and composites may be closing. Further, concerns have been raised about the endocrine disrupting (in particular, estrogen-mimicking) effects of plastic chemicals such as bisphenol A used in composite resins. Arguably, there is more credible evidence of a possible subclinical toxic effect of composite resins compared to dental amalgam.
In addition to health and ethics issues, opponents of dental amalgam fillings point to the negative externalities of water contamination and environmental damage of mercury. This concern is especially worrisome since its use and disposal by dentists go largely unregulated in many places, including the United States. The WHO reports that in the United Kingdom mercury from amalgam and laboratory devices accounts for 53% of total mercury emissions. Separators may dramatically decrease the release of mercury into the public sewer system, where dental amalgams contribute one-third of the mercury waste, but they are not required by some states in the United States.
A 2006 Zogby International poll of 2,590 US adults found that 72% of respondents were not aware that mercury was a main component of dental amalgam and 92% of respondents would prefer to be told about mercury in dental amalgam before receiving it as a filling. A 1993 study published in FDA Consumer found that 50% of Americans believed fillings containing mercury caused health problems. Some dentists (including a member of the FDA's Dental Products Panel) suggest that there is an obligation to inform patients that amalgam contains mercury.
The broad lack of knowledge that existed among the public was displayed when a December 1990 episode of the CBS news program "60 Minutes" covered mercury in amalgam. This resulted in a nationwide amalgam scare and additional research into mercury release from amalgam. The following month Consumer Reports published an article criticizing the content of the broadcast, stating that it contained a great deal of false information and that the ADA spokesperson on the program was ill prepared to defend the claims.[clarification needed]
The amount of mercury that patients are subjected to is itself controversial. Many studies have been conducted and findings have varied substantially. Depending on the study, average systemic uptake levels have been estimated to range between 1.7 µg/day and 17 µg/day.
As a (straight) comparison, these daily absorption levels comprise between 3.4% and 68% of workplace air quality safety standards (which range from 25 to 50 micrograms per cubic meter of air).
Critics point out that: (1) the workplace safety standards are based on allowable maxima in the workplace, not mercury body burden; (2) the workplace safety numbers are not applicable to continuous 24hr exposure, they're limited to a normal work day and 40 hr work-week; and (3) the uptake/absorption numbers are averages and not worst case patients (those most at risk).
A study conducted by measuring the intraoral vapor levels over a 24-hour period in patients with at least nine amalgam restorations showed the average daily dose of inhaled mercury vapor was 1.7 µg (range from 0.4 to 4.4 µg), which is approximately only 3.4% of the threshold limit value of the OSHA maximum allowable environmental level of 50 µg/day in the workplace. The World Health Organization (WHO) notes that exposure can be greatly increased by personal habits such as bruxism and gum-chewing and cites a report which found a 5.3 fold increase in mercury levels after chewing, eating, or toothbrushing. They report that amalgam is estimated to contribute 50% of mercury exposure in adults. In the studies the WHO reviews, daily mercury exposure estimates range from 3 μg/day to 9 μg/day.
A Swedish study of autopsies examined the mercury levels in brains and kidneys and found a strong correlation with the number of amalgam fillings. A German study found that mercury urinary excretion was significantly higher in those with dental amalgam fillings.
The NIDR Amalgam Study performed on a cohort of an adult military population of 1127 healthy males found that, based on their cross-sectional data it is estimated that, on average, each ten-surface increase in amalgam exposure is associated with an increase of 1 ug/L mercury in urine concentration. 
Research on 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. It was also found to have crossed the placental barrier in pregnant rats and shown to cross the gastrointestinal mucosa when amalgam particles are swallowed after amalgam insertion or after removal of old amalgam fillings.
Peer-reviewed scientific studies have come to opposite conclusions on whether the mercury exposure from amalgam fillings causes health problems. A 2004 systematic review conducted by the Life Sciences Research Office, whose clients include the FDA and NIH, concluded that "the current data are insufficient to support an association between mercury release from dental amalgam and the various complaints that have been attributed to this restoration material". A peer-reviewed Journal of the Canadian Dental Association article holds that "it seems likely that humans may have evolved with a threshold level for mercury below which there is no response or observable adverse health effects". Another review published in 2005 by the Freiburg University Institute for Environmental Medicine found 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", that "Alzheimer's disease or multiple sclerosis has also been linked to low-dose mercury exposure", and that "removal of dental amalgam leads to permanent improvement of various chronic complaints in a relevant number of patients in various trials."
Potential amalgam-induced health risks which have been studied by researchers include those related to allergy as well as toxicity. In 2002, the Food and Drug Administration issued a statement on dental amalgam which asserted that "no valid scientific evidence has shown that amalgams cause harm to patients with dental restorations, except in the rare case of allergy". A 1991-1997 study of 3162 patients in Sweden and Germany found that 719 of those with mercury fillings, or 23 percent, tested positive for systemic allergic sensitivity to inorganic mercury on the MELISA lymphocyte proliferation test. In a smaller group of 85 patients who suffered from symptoms resembling Chronic Fatigue Syndrome and had their amalgams replaced with composites and metal-free ceramics, "over 78 percent reported improvement in health status as compared to the period prior to metal removal." A paper published as part of a 1991 National Institutes of Health conference on side-effects of dental restorative materials reported a 22.53% incidence of allergy in subjects who had amalgam fillings for more than five years. Despite these findings, the ADA claimed as recently as 2004 that there had been less than 100 reported cases of allergic reactions to amalgam fillings.
The FDI World Dental Federation performed a meta-analysis of the literature on mercury toxicity and concluded that there is no documented scientific evidence to show adverse effects from mercury in amalgam restorations except in extremely rare cases of mercury hypersensitivity.
In 1991 the United States Food and Drug Administration concluded that "none of the data presented show a direct hazard to humans from dental amalgams." The Food and Drug Administration in 2008 subsequently issued an advisory warning pregnant women and children about dental amalgam containing mercury, and posted this warning on their website. On February 18, 2003, the New York Supreme Court dismissed two amalgam-related lawsuits against organized dentistry, stating the plaintiffs had "failed to show a 'cognizable cause of action'." The plaintiffs blamed the ADA, the New York Dental Association and the Fifth District Dental Society for deceiving the "public about health risks allegedly associated with dental amalgam."
Other lesser findings were reported, including a cross-sectional study in which cognitive function was not related to the number or surface area of occlusal dental amalgams, a case-control study in which patients with numerous amalgam fillings exhibited higher levels of neurological symptoms than the controls, and a study of self-referred patients who believed they were suffering ill-effects from dental amalgams which found no correlation between number of dental fillings and symptomatology, but higher mean neuroticism than two comparison groups (the authors concluded that self-referred patients with health complaints attributed to dental amalgam are a heterogeneous group of patients who suffer multiple symptoms and frequently have mental disorders).
In 2002, Maths Berlin, Professor Emeritus of Environmental Medicine and Chair of the 1991 World Health Organization Task Group on Environmental Health Criteria for Inorganic Mercury, published an overview and assessment of the scientific literature published between November 1997 – 2002 as part of a special investigation for the Swedish Government on amalgam related health issues. The 2002 report was a follow-up to a similar review of the literature published between 1993 and November 1997. The 2002 review assessed over 700 references. A final report was submitted to the Swedish Government on 3 June 2003 and included Berlin's report as an annex to the full report. Berlin's annex was translated into English and is currently available from the Government Offices of Sweden along with an introduction and summary of the full report. Berlin's 2002 review includes a summary of the 1997 analysis.
The proper interpretation of the data on hand is, to date, controversial. The vast majority of past studies have concluded, not without controversy, that amalgams are safe. However, although the vast majority of patients with amalgam fillings are exposed to levels too low to pose a risk to health, many patients (i.e. those in the upper 99.9 percentile) exhibit urine test results which are comparable to the maximum allowable legal limits for long-term work place (occupational) safety. Two recent randomized clinical trials in children  discovered no statistically significant differences in adverse neuropsychological or renal effects observed over the five-year period in children whose caries were restored using dental amalgam or composite materials. In contrast, one study showed a trend of higher dental treatment need later in children with composite dental fillings, and thus, claimed that amalgam fillings are more durable. However, the other study (published in JAMA) cites increased mercury blood levels in children with amalgam fillings. The study states, "during follow-up [blood mercury levels were] 1.0 to 1.5 μg higher in the amalgam group than in the composite group." EPA considers high blood mercury levels to be harmful to the fetus, and also states that "exposure at high levels can harm the brain, heart, kidneys, lungs, and immune system of people of all ages." Currently, EPA has set the "safe" mercury exposure level to be at 5.8 μg of mercury per one liter of blood. While mercury fillings themselves do not increase mercury levels above "safe" levels, they have been shown to contribute to such increase. However, such studies were unable to find any negative neurobehavioral effects.
During the FDA's December 13–14, 2010 CDRH panel review of the International Academy of Oral Medicine and Toxicology's request for reconsideration to the classification of amalgam, neurologists questioned the type of neurobehavorial tests and the unethical nature of a prospective trial looking for brain damage in children. Furthermore, evidence was presented by the Geier's that further analysis of the data found that an unusual porphyrin called Coproporphyrinogen indicative of pathophysiology (harm) was found in a dose response relationship to the number and size of amalgams placed, thus calling into question the claim that no injury had occurred.
As a result of a lawsuit, a fund was developed to research amalgam-related illness, and a clinical trial evaluating the effect of removing amalgam was published in 2008. The trial found that all groups had improved symptoms, including a group where the participants were treated with a "biological detoxification" therapy and dental amalgam was not removed. Follow-up of a clinical trial was published in 2010.
The American Dental Association (ADA) has asserted that dental amalgam is safe since its foundation in 1859. In its advisory opinion to Rule 5.A. of the ADA Code of Ethics, it has also held that, "the removal of amalgam restorations from the non-allergic patient for the alleged purpose of removing toxic substances from the body, when such treatment is performed solely at the recommendation or suggestion of the dentist, is improper and unethical". According to the Boston College Law School study, "A dentist who is found guilty of violating the ADA Code of Ethics can be sentenced, censured, suspended, or expelled from the ADA" and the "ADA forbids its dentists from suggesting mercury removal under threat of license suspension". The same study pointed out that state dental associations and disciplinary boards have "not only adopted the ADA's position as a matter of routine" in proceedings which have sanctioned anti-amalgam dentists or stripped them of their licenses in California, Maryland, Arizona, Colorado, and Minnesota, but in many cases "the board members themselves often belonged to the ADA as well". A 2002 article in the Atlanta Journal and Constitution reported allegations by anti-amalgamists that the ADA had effectively imposed gag rules which forbade them from discussing their positions with patients. The Boston College Law School study also cites proceedings in which an Arizona dentist, "is facing sanctions for advocating alternative materials", a California dentist lost his license, "for running an advertisement entitled: "Mercury Emission from Silver Filings Unsafe by Government Standards", and a Maryland dentist, "was sanctioned for writing an article on dental amalgam removal". More recently, the ADA has entered into litigation "aimed at defending its reputation and discouraging further lawsuits by patient-plaintiffs against dental amalgam".
Some practitioners may also recommend that patients with amalgam fillings have them removed and replaced, particularly if the patient is experiencing the symptoms that they attribute to the use of amalgam. These professionals recommend that unprotected amalgam removal should be avoided even in routine dental procedures to avoid exposure to mercury vapor and amalgam particulate matter.
Consumer Reports magazine claims that the connection between many of these diseases and amalgam fillings is solely revenue-generating propaganda. Consumer Reports told its readers on several occasions that "if a dentist wants to remove your fillings because they contain mercury, watch your wallet."
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 in developed countries, though overall amalgam use continues to rise worldwide. Given its superior strength, durability and long life relative to the more expensive composite fillings, it will likely be around for many more years to come.
Dental amalgam has been found to be a frequent contributor to oral lichenoid lesions and is possibly a variable associated with an increased risk of other autoimmune conditions such as multiple sclerosis, lupus, thyroiditis and eczema.
In 1991 Geir Bjørklund published a toxicological risk analysis of occupational diseases in dentistry that are related to chronic exposure to inorganic mercury, especially metallic mercury vapour. He found studies indicated that dental work involving mercury may be an occupational hazard with respect to reproductive processes, glioblastoma (brain cancer), renal function changes, allergies and immunotoxicological effects.
In 1994 Rowland found a 40% decline in fecundability in a case controlled study of female dental assistants exposed to mercury in dental offices.It should be noted that female dental assistants exposed to low levels of mercury were more fertile than their unexposed counterparts. There has been no evidence that dentists who are exposed to dental amalgam and vapor on a daily basis get mercury poisoning; however, individual dentists and staff members have become mercury poisoned and studies of the dental profession has documented a decline in cognitive abilities greater than the non-mercury exposed individuals. Some studies have indicated that mercury from dental amalgam has mild effects on some dentists. Dentists in several large-scale studies performed multiple cognitive tests and, compared to a normal population, lagged behind in many areas. A small-scale study based in Singapore found the "exposed-dentist" group had 14% worse scores in memory, co-ordination, motor speed and concentration compared to the control group. The study did not demonstrate any link between mercury exposure and these lagging scores, however. A newer study also found a link between cognitive impairment (including mood) and dental work, even though "exposure among these dental personnel is not much greater than exposures to the general population through the dental amalgam in their fillings" as shown by urinary studies. Twelve of 13 symptoms were correlated with greater mercury exposure.
A study examining the health effects of mercury on dentists in the UK published in the Occupational and Environmental Medicine Journal concluded that 180 dentists had on average 4 times the urinary mercury excretion levels of 180 people in a control group. Dentists were significantly more likely than control subjects to have had disorders of the kidney or memory disturbance. No direct correlation between urinary mercury levels and the disability, however, was found. Urine testing is unreliable for showing lifetime mercury accumulation rather than recent exposure.
The WHO reports that mercury from amalgam and laboratory devices accounts for 53% of total mercury emissions, and that one-third of the mercury in the sewage system comes from dental amalgam flushed down the drain. 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, but in many countries it is not regulated, including the United States. The environmental pollution of mercury imposes health risks upon the surrounding population; in economics this pollution is considered an external cost not factored into the private costs of using dental amalgam. Separators may dramatically decrease the release of mercury into the public sewer system, but they are not required in the United States.
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 US states.
The Association of Metropolitan Sewerage Agencies (AMSA) studied seven major waste-water treatment plants and found that dental uses were "by far" the greatest contributors of mercury load, on average contributing 40%, over 3 times the next greatest contributor. The EPA recognizes dental amalgam as a major source of the mercury in the water. The Western Lake Superior Sanitary District that dentists emit .1 grams of mercury per day per dentist. Based on this, dental amalgam contributes 14% of the mercury in Seattle and 12% of the mercury in San Francisco. 4% of the mercury in Lake Superior is believed to originate from amalgam. The National Association of Clean Water Agencies noted in a report that purification of mercury from waste water will impose a significant financial burden upon municipal treatment plants. Several other groups have analyzed mercury in waste water and concluded that it is a serious problem. Other studies have shown this to be a gross exaggeration. With respect to pollution in the United States, a study done in 1992 showed that batteries "accounted for 86 percent of discarded mercury and dental amalgam a mere 0.56 percent."
Cremation of bodies containing amalgam restorations results in near-complete emission of the mercury to the atmosphere, as the temperature in cremation is far greater than the boiling point of mercury. In countries with high cremation rates (such as the United Kingdom), mercury has become a great concern. Proposals to remedy the situation have ranged from removing amalgam-containing teeth prior to cremation to installing activated carbon adsorption or other post-combustion mercury capture technology in the flue gas stream. These proposals range from unpopular to expensive.
Studies have shown the amount of mercury to be released per body cremated to range from 0.25 grams to slightly over 1.00 grams. The number of amalgam fillings and their size determines the volume of mercury released, as well as any deposition which may occur in the backend of the cremation equipment, either incidental or intentional (e.g. if a baghouse or other filtration system is employed).
As a comparison, a mercury thermometer contains 0.50 grams of mercury, and an average compact fluorescent lamp contains 0.004 grams of mercury. Such numbers indicate that the average cremation of a body with amalgam emits as much mercury as is contained in 156 compact fluorescent lamps.
Alternative materials include composite resins, glass ionomer cements, and gold alloys. Most of these materials, with the notable exception of gold, have not been used as long as amalgam, and some are known to contain other potentially hazardous compounds. This is why biocompatibility testing is recommended for all dental materials as per ADA/ANSA or ISO standards, and can be performed by specialized laboratories. 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 in 2001.
Alfred Stock, a noted chemist, reported becoming very ill, and eventually tracing his illness to his amalgam fillings and the resulting mercury intoxication. He described his recovery after the fillings were removed and believed that amalgam fillings would come to be seen as a "sin against humanity." Hal Huggins, a Colorado dentist (previous to having his license revoked), is a notable critic of dental amalgams and other dental therapies he believes to be harmful; his views on amalgam toxicity were featured on 60 Minutes.
|The examples and perspective in this article may not represent a worldwide view of the subject. (June 2010)|
In 1840, the American Society of Dental Surgeons was founded by a group of dentists who met in New York city. It was the only national organization of dentists in existence at the time. Chapin A. Harris, the co-founder of the ASDS and the first dental school in the US, the Baltimore College of Dental Surgery, spoke of dental amalgam 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". 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, the 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.
|This section requires expansion. (May 2008)|
Some legislators have introduced legislation to prohibit or restrict use of amalgam fillings.
In most European countries (for example, the United Kingdom, France, and Italy), amalgam use is unrestricted. Some other countries, such as Sweden and Denmark, have banned the use of mercury in dental amalgams, citing health or environmental 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."
Sewers from Norwegian dental clinics older than 1994 (or if there is other reason to believe amalgam have ended up in the sewers instead of the patients mouth) shall be cleaned by experienced personnel to properly remove any residual mercury. The detailed procedure to do so is available from Norwegian Pollution Control Authority free of charge.[dead link]
In the US, many states are undertaking both regulatory and non-regulatory activities to ensure proper management of mercury-containing dental amalgam.
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:
On July 28, 2009, FDA issued a final rule that: (1) reclassified mercury from a class I (least risk) device to class II (more risk) device; (2) classified dental amalgam as a class II device; and (3) designated a special controls guidance document for dental amalgam.
The special controls guidance document recommends specific labelling, including an Information for Use statement "Dental amalgam has been demonstrated to be an effective restorative material that has benefits in terms of strength, marginal integrity, suitability for large occlusal surfaces, and durability. Dental amalgam also releases low levels of mercury vapor, a chemical that at high exposure levels is well documented to cause neurological and renal adverse health effects." 
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 of dental fillings. The mandated notice reads:
Following the meeting of the joint committees on 6–7 September 2006, when the panel of outside advisers that the FDA had asked to assess the conclusions of its report on amalgam safety rejected the FDA report in a 13-7 vote, they stated 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 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."