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What are amalgam fillings made of?

ASOMAT response:      The ADA answer is misleading. Dental amalgam is NOT a true alloy. It is made up of 50% mercury, which is NOT locked into a set filling but escapes continuously during the entire life of the filling in the form of vapour, ions and abraded particles.

Amalgam is often referred to, misleadingly, as silver amalgam. Because mercury makes up 50%, and silver only 30%, it should be referred to as mercury amalgam. Health Canada's letter to the Canadian Dental Association castigated the CDA for just such behaviour.

The absorption rate of inhaled mercury vapour is extremely high, approximately 80% of the inhaled dose, a small proportion of which reaches the brain tissue within each blood circulation cycle. This release is stimulated by chewing, brushing and hot fluids. One study reported that mercury vapour levels in the mouth 54 times higher in the mouth of a patient with amalgams, than levels in the mouth of a patient without amalgams, after chewing.

Mercury vapour levels in the human mouth have been recorded in many studies. These studies indicate that stimulation by chewing or increase in temperature will lead to an elevation of the mercury vapour levels. These levels remain elevated for about 90 minutes. Thus, during the course of a day, the stimulation of regular chewing and grinding could lead to a permanently elevated level of mercury vapour. A recently published study gives an indication of the amount of mercury released from dental amalgam (35). Other studies (40,42,47,48,49,51) indicate levels as high as 87mcg/m3, and in some individuals this may go as high as 100mcg/m3 (37). Even a level of only 10mcg/m3 would be 714 times higher than the ATSDR MRL for chronic inhalation exposure to metallic mercury vapour.


Is it true that mercury leaks out of fillings?

ASOMAT response:           The ADA answer is correct but incomplete. It neglects to advise readers of the research which has shown that mercury from amalgam fillings is released continuously and accumulates in the body.

Human autopsy studies have shown that the concentration of mercury in the brain is directly related to the number, size and age of amalgam fillings in the mouth.(93,95) The brain is the critical target organ for mercury vapour and methylmercury and is most significant in cases of chronic low level exposure to mercury vapour (Sheridan P. ‘Amalgam restorations and mercury toxicity’ Masters thesis Sydney University 1991). Mercury from amalgam fillings is stored principally in the kidneys, liver and central nervous system. This mercury has also been shown to cross the placenta and collect in foetal tissue. Studies show the level of mercury in liver, kidney and brain tissue of deceased foetuses, newborn and young children is proportional to the number of amalgam fillings in the mother's mouth. One such study concludes that "the elevated concentrations of inorganic mercury found in the tissues of people with amalgam filings, derive mainly from these fillings and not from other theoretically possible sources. (57,58)

The continuing and chronic release of mercury from dental amalgams ensures that the mercury levels build up in tissues throughout the body over many years, interfering with a variety of body functions. It is this chronic long term heavy metal poisoning which is the problem, not the one-off brief and acute exposure.

It should also be noted that elemental Hg and Hg vapour from dental amalgam can be methylated in the body to form methyl mercury (98,99,120,169,185,192,195,197,198,208, 213). This form of mercury is readily transported across the placenta, and via the breast milk.


Is this mercury harmful?

ASOMAT response:            The ADA answer is misleading and incomplete. The NHMRC withdrew its policy statement on dental amalgams in August 1997 and has had no policy statement since that time.

Further, the findings of the Swedish Medical Research Council have been severely criticised for bias and are not accepted as presenting an accurate or comprehensive review of the literature.

The extreme toxicity of mercury is well documented. The toxic threshold for mercury vapour has never been found. Even the US Environmental Protection Agency has so stated( 30,31,32). The peer reviewed published literature clearly shows that neurological damage is one of the most reported effects of long term, low level mercury poisoning (61,62,63,64,65,66,67).

The ADA appears to have forgotten its own advice to its members in a memorandum dated December 1989, (included as a supplement to the News Bulletin in December 1989) in which it warned about the toxic effects of mercury vapour. It wrote at the time.."Chronic toxic exposure to mercury is manifested as neurological effects. Early non-specific signs include weakness, fatigue, anorexia, weight loss, and gastro-intestinal disturbances." Further warnings stated.. "Signs of advanced toxicity include tremor and may advance to behavioural changes including excitability and memory loss. There may also be ataxia and speech disorders. The triad of symptoms - increased excitability, tremors, and gingivitis have been recognised as major manifestations of mercury toxicity from  inhaled mercury vapour"

The existing occupational standards are all specifically declared to be estimates only, on the appearance of CLINICALLY OBSERVABLE SIGNS AND SYMPTOMS. Statements by the dental profession that the amount of mercury exposure encountered by patients from dental amalgams is too small to be harmful are contradicted by the scientific literature and are totally indefensible. Dentists receive no training at all which would enable them to even look for symptoms relating to mercury toxicity. As far back as 1975 the consensus at that time had already concluded there was no level of mercury vapour established where the effects could be considered harmless. (The International Committee on MAC Values for Mercury 1969, US EPA document on mercury 1973 and 1984, US NIOSH document on mercury 1973). More recently WHO endorsed the earlier consensus when its 1991 WHO Criteria 118 publication stated clearly that for mercury vapour "a specific no-observed-effects level (NOEL) cannot be established", meaning that NO level of mercury vapour that can be considered harmless has been found. The findings of this WHO Expert Committee were accepted by Health Canada in its own deliberations which led to a change of policy recommending restrictions in the use of amalgams.

Multiple small doses will result in body accumulation. Chronic exposure to mercury vapour produces neurological effects which include excitation, tremors, insomnia, vasomotor disturbances, gingivitis and kidney dysfunction. Toxicity of inorganic mercury includes inflammation of mucosal surface of the mouth, gingivitis with swelling, and kidney dysfunction (nephrotic syndrome) (71,72,73,74,75,76).

Neurological damage is sustained by chronic exposure to mercury vapour. This is relevant not only for the patients receiving amalgam fillings but also for the future children of women with amalgam fillings. It is also relevant to dentists who place it. Many studies have demonstrated neurological damage to dental personnel (12,77,78,79,80,81,82,83,84,85) Many other studies have also showed the harmful effects of mercury in the brain (65,66,67,64,62,70).

Published research (104,105,106,107) now demonstrates that mercury from dental amalgam may be a significant factor in antibiotic resistance.

The synergistic effects of mercury combined with various other substances is also an area of significant concern which has been under-researched to date. The toxic effects of mercury are further enhanced when mercury is in combination with other metals such as zinc and lead. The effects of mercury and lead combined have also been reported. One study showed that when a lethal dose (LD1) of mercury was combined with 1/20 LD1 of lead, the combination of the two resulted in a LD100 in the test animals (44). This has not been investigated in human subjects but it is clearly reasonable to assume the possibility of similar effects in amalgam-bearing humans. Mercury has been shown to interfere with tubulin synthesis resulting in "neurofibril tangles" in the brain. Mercury, specifically from dental amalgam, placed in rats' teeth, has been shown to affect tubulin synthesis. 

The relationship of mercury in Alzheimer’s disease is still not fully determined. There is however, a body of evidence which is strongly suggestive of a connection. ASOMAT does NOT assert that mercury causes Alzheimer’s. ASOMAT does believe however, in the light of recent research (10,90,100,101,102,103), that it is quite possible that low levels of mercury present in the brain could cause normal cell death, and that in susceptible people this could lead to dementia which would be similar to Alzheimer's disease. This would be entirely consistent with what is known in the literature about mercury’s neurotoxicity. The most recent research (  "Increased blood mercury levels in patients with Alzheimer's disease."  Hock C, Drasch G, et al. J Neural Transm 1998;105(l):59-68 )  demonstrated elevated blood levels of mercury in AD. The researchers suggested that possible explanations of increased blood mercury levels in AD include yet unidentified environmental sources or release from brain tissue with the advance in neuronal death.

The dangers of complacently accepting ‘guesstimated’ safe levels are starkly demonstrated in a recent study (50) which studied 917 children of approximately 7 years of age. Clinical examination and neurophysiological testing did not reveal any clear cut mercury related abnormalities, but mercury related neuropsychological dysfunctions were most pronounced in the domains of language, attention, and memory, and to a lesser extent in visuospatial and motor functions. These associations remained after adjustment for covariates, and after exclusion of children with maternal hair mercury concentrations above 10 micrograms (50 nmol/g). The effects on brain function associated with prenatal methyl mercury exposure appeared to be widespread, and "early dysfunction was detectable at exposure levels currently considered safe."

The toxicity of this material was tragically demonstrated with the recent death of Prof. Karen Wetterhahn, (The Scientist 11 (21) October 1997, front page). Prof. Wetterhahn died from exposure to two drops of dimethyl mercury that penetrated her latex gloves. She first lost her balance, then her hearing and eyesight, went into a coma and died 10 months after exposure, despite valiant attempts to save her life. Dimethyl mercury is less reactive than Hg2+ but is definitely more lethal due to the fact that it concentrates in the central nervous system.


Is it true that mercury is in our diet?

ASOMAT response:          The ADA answer is correct but incomplete. It neglects to inform readers of the research which has shown that mercury from dental amalgams is by far the main source of mercury exposure in humans and is therefore misleading.

Both Health Canada (1996a) and the World Health Organization (1991) (14) consider dental amalgam to be the single largest source of mercury exposure for the general public, with amalgam potentially contributing up to 84% of total daily intake of all forms of mercury from all sources.

In 1991 The World Health Organization (WHO) published a report (14) showing that the mercury retained in the body from dental amalgam exceeds the combined amount from  all other environmental sources, including seafood. Therefore, the level of exposure resulting from amalgam is not an issue of contention. The WHO also noted that for mercury vapour "a specific no-observed-effects level (NOEL) cannot be established, ie. NO level of Mercury Vapour has been found that can be considered harmless. The levels of exposure are small. We point out however, that in toxicological terms, ‘small’ needs to be relative to the threshold for effects. Where no threshold has been defined (as with Hg vapour) it must be compared to a regulatory reference dose. The total dose may be small but where the reference dose is smaller, then the exposure can still be detrimental. Current research, using solid biochemical data, shows that ‘small’ as it is, it is still enough to compromise body health.

Exposure to mercury in ANY form or from ANY source is potentially dangerous. Wherever possible avoid contact with ALL materials containing mercury.


Can you be allergic to the mercury in amalgam?

ASOMAT response:         The ADA answer is misleading.

The mercury from dental amalgams is exactly the same as mercury used in industry. If anything it is even more pure due to the requirements of materials standards (technical   NOT toxicological). To try to infer that reactions to mercury from dental amalgam are somehow different from mercury from other sources is completely misleading.

Claims by the Australian and American Dental Associations that the incidence of mercury allergy is less than 1% have never been supported by any references.  Such claims are totally refuted by the scientific literature. Peer reviewed published research has reported allergy levels of 5%-8% (Rudner) 27% (Djerrasi & Berova), 2%-10.8 % (White & Brandt), 31%, 27%, 32%, 39% (Miller et al), 11.3% (Brun), 9.6 % (Nebenfuher et al), 13% (Sato et al) (119, 275,276, 278,279,280). Despite this research, the dental associations, including the Australian Dental Association, have, without offering any supporting evidence, falsely stated, and continued to maintain, that the true incidence of mercury allergy is much less than 1% (Dr. Sheldon Newman "Amalgam best material, Expert Reports" AmDA News September1, 1986). They continue to publicly claim that amalgam is only dangerous to those 'rare individuals' who are allergic to amalgam. Such comments are blatantly false and misleading. (Even Caulk Co., the manufacturers of the Dispersalloy brand of amalgam warn: "Allergic reactions that may occur in previously exposed persons include dermatitis, encephalitis, and death")As cited above, the research shows allergy levels of up to 39%. Hg allergy is VERY relevant in the context of health effects and mercury exposure. It is relevant because mercury allergies are caused by mercury binding to a host protein, forming a P-S-Hg-X complex that the body’s immune system recognizes as a foreign protein and which it attacks. Low level chronic exposure would sensitize the immune system of anyone with the genetic make-up predisposing them to having this problem. It is similar to the penicillin sensitivity that many individuals have. Assuming half of the Australian population have amalgam fillings and 13% (119) of them showed symptoms caused by true allergy to mercury, this would mean that over 1,700,000 people have had their immune system compromised to some extent, either minor or significant, by a toxic substance, the most common source of which is unequivocally dental amalgams!

True allergy is only one of the possible immune reactions to mercury. General sensitivity to the metals in amalgams also exist. Mercury from amalgams has been implicated in immune disease. Lindquist &Mornstad (250) concluded that "It thus seems that mercury released from amalgam fillings may initiate or support an ongoing immune disease" and called for further research.


Is it true that Sweden has banned amalgam?

ASOMAT response:           The ADA answer is misleading and incomplete.

Sweden has effectively banned amalgams from the year 2000. Sweden's Department of Social Services, NOT the Ministry of the Environment, announced in mid 1998 that it will no longer reimburse dentists for placing amalgam fillings from the year 2000. It is also worth restating Health Canada’s most significant recommendations; essentially, don’t use it in children, don’t use it in pregnant women, don’t use it in people with kidney diseases, and don’t flush it down the sewers. These echo the concerns of the German and Norwegian Health Departments which advised that amalgams not be placed in the mouths of young children or pregnant women, or in people with kidney problems. The Canadian Dental Association further advised their members not to place amalgams in people with neurological problems. It should also be noted that in May 1998 the British Health Department sent out letters to all doctors and dentists in the UK advising them not to place or remove amalgam fillings from the mouths of pregnant women. We should further note that one of NHMRC guidelines states ‘salvage all amalgam scrap and store in a tightly closed container. Storage under water offers no protection’. Further, the American Dental Association (JADA 105: pp 930 1982) recommended that amalgam scraps be stored under photographic fixer solution in a tightly closed container. Strong advice for a supposedly safe material !!

Should I have my dental amalgam fillings removed?

ASOMAT response:      The ADA answer is incomplete and misleading. The ADA does not discuss systemic health and does not acknowledge the full range of research showing that there are health issues related to dental amalgams.

Mercury does NOT cause a specific disease. It causes heavy metal poisoning which is characterised by a variety of symptoms. Amalgam is the greatest source of mercury for the average person. Tissue levels of mercury increase with time, the longer the amalgam fillings stay in the teeth. Amalgam removal leads to decreased levels of mercury in the body.

If it is not safe in the environment, how can it be safe in the mouth?

As far as improving dental health is concerned, it should be noted that the corrosion and expansion properties of amalgam fillings predispose to certain problems. A number of very respectable and 'establishment' dental authorities have reservations about dental amalgam as a filling material. To quote just two....

Dr Richard Simonsen the editor-in-chief of Quintessence (Volume 26, Number 3,1995),   wrote:  "Amalgam should never be used as a restorative material in paediatric dentistry." Why? Because better alternatives are available."

Dr. Harold Loe, the Director of the National Institute of Dental Research ( NIDR), wrote in the  "Dental Products Report  Sept 1993":

"That first filling is a critical step in the life of a tooth. Using amalgam for the first filling requires removing a lot of the tooth substance, not only diseased tooth substance but healthy tooth substance as well. So, in making the undercut you sacrifice a lot, and this results in a weakened tooth. The next thing you know the tooth breaks off, and you need a crown. Then you need to repair the crown...and so it continues to the stage where there is no more to repair and you pull the tooth. With the first filling you should do something that can either restore the tooth or retain more healthy tooth substance. Use new materials-composites or materials you can bond to the surface without undercuts. You can do this with little removal of the tooth substance so that the core of the tooth is still there."

This decision of amalgam removal is one that only the patient can make but the patient should have ALL the facts before doing so. Amalgam fillings have been associated, in the scientific literature, with a variety of problems  such as periodontal problems (pyorrhea), allergic reactions, oral lichen planus, interference with the immune system, as measured by the T-lymphocyte count, (123,124,125,126, 127,128, 129,130,131,132,133), multiple sclerosis (134,135,136,137, 138,139), fatigue, (142,143,144,145,146,147,148,149,150,151) cardiovascular problems (142,152, 153, 154,155,156,157,158, 159,160,161,162,163,164,165,166,167,168), skin rashes (119,170,171,172,173,174,175, 176,177,178, 179,180, 181,182,183, 184,186,187,188,189), endocrine disorders (190,191), eye problems (60,74,80,193,194,196,199).

Controlled, broad-scale scientific studies investigating the effects on the health of patients of mercury released from dental amalgam fillings have NEVER been conducted. The true nature and full extent of effects are therefore unknown. Several studies have purported to examine large groups but all have suffered from various methodological weaknesses which limit their usefulness. The only study which we are aware of which compared two well controlled groups is the one by Siblerud (Siblerud R. Relationship between mercury from dental amalgam and health Toxic Substances Journal, 10:425-444. 1990) which suggested that mercury poisoning from dental amalgam may play a role in the etiology of many health disorders. A comparison of 125 health symptoms was made between a group of subjects with amalgams and a control group without amalgams. The 47 amalgam subjects reported a total of 45% (P - .0001) more health symptoms per subject compared to an age- and sex-matched control group of 48 non-amalgam subjects. Symptoms that were exhibited significantly more by the amalgam group were less happiness, less peace of mind, poorer reading ability, foul breath, tremors, colds and respiratory infections, heart or chest pains, heartburn, menstrual difficulties, sudden anger, depression, irritability, tiring easily, tired in morning, hay fever, trouble with night vision, and a metallic taste in mouth. Most of these symptoms can be explained by the know effects of mercury toxicity.

It has been suggested that if intention tremor is not present there are no health effects to be concerned. It should be noted that this is contrary to the published scientific research, the advice published by the dental associations and the advice published by the manufacturers themselves.

Blood mercury levels, significantly higher in amalgam patients than in non-amalgam patients, correlate with the number and size of the fillings but return to normal when the fillings are replaced (200,201,202). In one study (203), the daily intake of mercury from amalgams in the subjects was estimated to be at least 1.5ug. Scientific research has clearly established that mercury vapour passes very rapidly from blood to tissue and that levels of mercury in blood or urine are not reflective of the mercury in the body (204,205,206).The earliest symptoms of long term, low level mercury poisoning are sub-clinical and neurological. Consequently, due to their subtlety, these symptoms are easily mis-diagnosed. This is a challenge to our approach to health care and requires a different awareness of prevention. If all symptoms were totally reversible, with no enduring damage to the patient, then the problem would be relatively straightforward. Unfortunately, by the time chronic mercury toxicity is accurately recognised, the damage is done and often NOT totally reversible, even though significant improvements can be achieved with appropriate treatment.

A contemporary example of this is Pink’s disease where those patients affected by exposure to mercury as children are still being affected, even though the original source of exposure is now absent. The fact that such potential irreversibility exists is the reason that prevention and caution must be the dominant sentiments in national health policy, and why the onus of proof of safe levels MUST be on those who advocate the use of this material and not on those in whose mouths it is placed. The consequences of getting it wrong (most recently demonstrated by the Faroe Islands study (50) in which neurological damage by methyl mercury was shown at levels previously considered safe) are too debilitating and too long lasting. We must begin to think in terms of potential and pre-symptomatic effects. In studies in which rats were exposed to mercury vapour, it was found that they showed few clinical symptoms, even though 41% to 75% of their brain tubulin was dysfunctional. In amyotrophic lateral sclerosis (ALS), over one half of the neurons were destroyed before the patients showed signs of clinical distress.

What constitutes clinical versus sub-clinical health impairment? In the case of lead exposure in children for example, no clinical measurement or test can be applied to the individual children to measure impairment of IQ due to lead exposure. However, groups of children exposed to lead have a slightly lower average IQ than do children with no lead exposure. Is the effect clinical or sub-clinical? Does this make low level lead exposure less biologically (or societally) significant? The answer must surely be NO. Similar results have already been reported with low levels of mercury exposure (50,52).

There is obviously a lot of neural redundancy in the body but is it really appropriate to cavalierly take known and universally acknowledged toxins into our body just because we can withstand a certain amount before obvious, but often irreversible, symptoms become apparent? Is such a position morally and ethically justified when safer alternatives have been available for many years?




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