This is the pivotal question—and the one most often denied by the ADA. That mercury does indeed leak from dental amalgam was first discovered in 1926 by the German scientist, Dr. Alfred Stock.4 His findings were confirmed in 1979 by Dr. Gay and co-workers5, and again in 1981 by Dr. Carl Svare.6 Dr. Svare conducted experiments in volunteers among his dental students to see if the amalgams in their mouths released mercury. One student, growing hungry, left during the long wait to be tested and returned eating a slice of pizza. When she was tested, the doctor was shocked to see that she had enormously high mercury levels in her readings. Thinking it might be the pizza that contained the mercury, he had it tested. When the levels came back negative, he had her repeat the breath test, but this time had her chew on a piece of rubber tubing. Once again her mercury vapor levels were sky high.
Based on this "chewing gum study" other researchers repeated the experiment under better controlled conditions and found similar results1: chewing dramatically increases release of mercury from dental amalgams. The EPA sets the maximum acceptable dose of mercury, other than from air, at 10 ug. The average dental amalgam filling contains 750,000 ug of mercury, so the store of mercury in fillings is considerable.
One researcher found that chewing gum for five minutes led to a threefold increase in the release of mercury vapor from amalgam fillings, while chewing in controls without fillings had no effect on mercury levels. When test subjects rinsed with hot water he saw a further increase in mercury vapor release. His conclusion was that the amalgam alloy is unstable and constitutes a source of long-term mercury exposure that is toxicologically unsuitable as a dental filling material.8 A large number of people chew gum, not just for five minutes but for hours at a time. In addition, nearly everyone consumes hot food and liquids on a daily basis. People who do both have the highest mercury vapor levels and hence the highest blood and tissue levels.
In another study, Zander and colleagues found, in examining ninety-three males and females aged eighteen to sixty-three years of age, that those with dental amalgams had significantly higher urine mercury levels than subjects without amalgams.' In addition, urinary mercury levels were highly correlated with the number of amalgam surfaces. (Dentists count amalgam fillings according to the number of sides of the tooth containing amalgam, called surfaces.) They concluded that mercury exposure from dental amalgams is greater than from food or other sources.
Several studies have shown that mercury vapor from dental amalgams can reach levels of from 6 to 150 ug/M3.10 The EPA banned mercury-containing latex paint for producing mercury vapor levels of 2-3 ug/M3. While you might spend an inordinate amount of time in your house, your teeth follow you everywhere.
One study involving thirty-five subjects found that chewing markedly elevated oral mercury levels which then slowly declined over ninety minutes when chewing was stopped. Those with twelve or more mercury amalgam surfaces had levels reaching 29 ug a day, whereas those with four or fewer had 8 ug of mercury released daily. These levels alone exceed by a factor of eighteen those set as allowable mercury exposure from all sources.
Another consideration is manipulation of your fillings by a dentist. A high-speed dental drill can release mercury levels as high as 4,000 ug/M3 eighteen inches from the drill. (Remember, 50 ug/M3 is the limit set by the EPA for safe occupational exposure.) This high concentration of mercury is absorbed by the tissues of your mouth and distributed throughout your body. The dentist and his assistant share in this mercury cloud. In fact, even unwary patients sitting in the waiting room are exposed to high mercury vapor levels.
It is also important to realize that approximately 80 percent of the mercury released by your fillings is being constantly absorbed and stored in your body. For example, if your fillings release 12 ug of mercury a day, in a week you will have absorbed 67.2 ug, and in a month 288 ug. A small portion of that dose will be excreted, but most of it will be stored in your body. We already know that absorbed mercury accumulates in the nervous system. In fact, studies have shown that brain levels of mercury increase about three- to fourfold in those with dental amalgams compared to those without. Mercury from amalgams was found to saturate gum tissues as well as the jawbone itself.
It should be appreciated that not all people release mercury from their amalgams at the same rate. One Swedish study found that some people release as much as 23-63 ug/g of creatinine of mercury daily, indicating a daily uptake of 100 ug a day, well within the toxic range." This number is five to ten times higher than the average found in the general population of Sweden.
Every day, we do many things that increase the release of mercury vapor from amalgam fillings: chew gum, brush our teeth, use a water pick, have dental work done or our teeth cleaned, and consume hot foods and drinks. Even undergoing general anesthesia poses a risk due to oral manipulation by the anesthesiologist during intubation and mechanical stimulation to the teeth by the endotrachial tube.
Removing amalgams without taking special precautions dramatically increases mercury blood levels for over a month. One study found that immediately following removal of amalgam fillings, plasma mercury levels rose three- to fourfold and tissue levels rose by 50 percent. Also, such a concentrated release of mercury vapor can severely exacerbate preexisting neurological conditions.
Once amalgam fillings are removed, mercury levels will slowly decline. One study, in which seventeen people had their amalgams removed, found that mercury levels actually increased 30 percent during the first week, slowly declining over the next twelve months.12 In this study the mean half-life of blood mercury was ninety-five days. Unfortunately, removal from the nervous system is incomplete and occurs at a much slower rate.
A final study clearly refutes the ADA's lie that mercury is not released from amalgam fillings. In this study, subjects of all ages were examined for the concentration of mercury in their saliva prior to and after chewing." The data were obtained following ten minutes of chewing sugar-free gum. In the study group, children had an average of three fillings, thirty-to thirty-four-year-olds had the greatest number of fillings, and older individuals had an average of five fillings. (In older people, the lower average was due to the fact that many had lost teeth.)
Researchers found a direct correlation between the number of amalgam fillings and mercury levels in the subjects' saliva, although values varied considerably. People at the low end of the curve tested for less than 5 ug/1 of mercury in their saliva and those at the high-end had values over 1,000 ug/1. Approximately 1.7 percent of the subjects had mercury values greater than 400 ug/1. In all, 30 percent of the people examined had mercury values above those suggested by the World Health Organization (WHO) as being acceptable. It is important to note that WHO admits there is actually no truly safe level of mercury exposure.
Extrapolating from this study, we see that when we are dealing with very large numbers of people, for example 200 million in the United States alone, this puts over sixty million people at a very high risk of mercury toxicity. Within this number are a significant percentage of people with low levels of antioxidant defenses and other metabolic derangements that place them at even higher risk.
It is critical to note that two age groups were found to be in the highest risk categories for mercury absorption from dental amalgams: women of child-bearing age (twenty to thirty-nine years) and children between the ages of six and nine. As we shall see, it is the developing child's brain that is most at risk.
A word of caution concerning animal studies. Often we assume that the effects of toxin exposure in animals correspond to those in humans, but this is not always so. For example, compared to humans, cats have a tenfold higher resistance to the uptake of methylmercury across the blood-brain barrier. To produce chemical imbalance (ataxia) using mercury in cats requires a minimum dose of 46 ug/kg/day and blood levels of 6-8 ppm. In humans, ataxia occurs after a dose of only 4 ug/kg/day or 0.6 ppm of mercury. This means that humans may be much more sensitive than animals to mercury. We find a similar phenomenon with amphetamine. Many animals have physiological and biochemical systems quite different than humans, yet as far as we can tell, humans, rats, and mice appear to react similarly to mercury exposure.
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