For more than 150 years, dentists have been putting ‘silver’ fillings—or dental amalgam, which contains mercury—into cavities in our teeth. And for most of that time, dental groups have been reassuring us that the fillings are safe. The mercury is ‘locked’ within the material and can’t escape and, in any case, is elemental, or inorganic, mercury, the safest form of what everyone acknowledges is one of the most toxic metals on the planet.
But a major new study says our health guardians are wrong: mercury does leak from fillings, and it’s a substance that can damage our brain, heart, kidneys, lungs and immune system. And perhaps the most chilling part of the researchers’ discovery is that when the elemental mercury leaks into the bloodstream, the gut converts it into methyl mercury, its most toxic form.1
It’s a significant finding. Methyl mercury mainly comes from fish, and defenders of amalgam fillings have maintained that they weren’t adding to our overall ‘mercury load’. But the new discovery means that anyone with eight amalgam fillings will have 150 per cent more methyl mercury in their blood than someone without these fillings—and around 25 per cent of the American public has 11 or more silver fillings.
The open secret
It’s long been an open secret in dentistry. The American and British Dental Associations have barred dentists from putting up posters or handing out information sheets that reveal that amalgam fillings are 50 per cent mercury, although dentists have been quietly moving towards the use of safer materials.
Despite such an information blackout, fears about the dangers of amalgam fillings began to escalate in the 1980s, when it was discovered they were releasing mercury vapours that were being deposited in the kidneys. Even then, the dental associations batted back the concerns because the evidence was inconsistent or based on only small study populations.
But this new study, carried out by researchers at the University of Georgia, puts paid to those objections. They analyzed the data from 14,703 people gleaned from two previous US National Health and Nutrition Examination Surveys (NHANES), and compared the amount of mercury in the blood with the number of fillings each participant had. The researchers also considered other factors that contribute to mercury levels in our bodies, including the environment and the amount of fish in the diet.
After factoring in these other sources, the researchers still found a direct association between the number of amalgam fillings and amount of methyl mercury in the blood.
But while methyl mercury levels increased between the two surveys (2003–2004 and 2011–2012), there was no increase in the number of fillings. This suggests that the gut may be changing elemental mercury to methyl, said researcher and professor of environmental health science Xiaozhong Yu. “As toxicologists, we know that mercury is poison, but it all depends on the dose. So, if you have one dental filling, then perhaps that’s OK. But if you have more than eight dental fillings, the potential risk for adverse effect is higher,” he said.
The average American has three fillings, the researchers say, but even this may not be safe if they’re also eating fish more than a few times a week or are exposed to mercury in their work environment.
It stays with us
It could also be that amalgam fillings on their own can leak enough to cause unacceptably high levels of methyl mercury in the blood. The European Commission’s BIO Intelligence Service (BIS) evidently thinks so. A 2012 report pointed out that autopsies have shown that bodies with amalgam fillings can have up to 12 times more mercury than usual in their tissues.2
The World Health Organization (WHO) also believes that amalgam fillings are the most significant source of mercury in our bodies. It reckons we get four times the level of mercury from our fillings as from fish: if we are absorbing 10 mcg of mercury from our fillings, then fish is adding a further 2.3 mcg and the environment contributes just 0.3 mcg.3
And the process of leaching—where fillings are constantly releasing mercury—begins almost immediately, within a day of the filling being placed, a new study has found, so confounding the belief that it happens only with worn and old fillings. When researchers at the University of Peshawar in Pakistan measured mercury levels in blood, nail, urine and hair samples before and immediately after the use of an amalgam dental filling, they discovered that levels were up to eight times greater a day after the procedure compared with the controls who didn’t get a filling.4
The smoking gun
So what damage is mercury doing to our health? There are too many lifestyle variables to absolutely establish a direct cause-and-effect between mercury levels and disease, but common sense would suggest that having one of the world’s most toxic metals in our body must be doing some damage. It’s smoking-gun evidence: we can’t see it directly, but we have the next best thing—all the evidence is pointing in the same direction.
It’s established that mercury poisoning, or hydrargyria, can damage the brain, kidneys and lungs, and symptoms include impaired vision, hearing, speech and muscle coordination. Mercury is also suspected to play a part in autoimmune and neurological diseases like Alzheimer’s and multiple sclerosis (MS). Indeed, Prof Boyd Haley at the University of Kentucky has proposed the hypothesis that elemental and organic mercury compounds, among other brain toxicants, are one major cause of Alzheimer’s.5
In one lab test, researchers at the University of Calgary in Canada discovered that when neurons were exposed to mercury ions, the metal disrupted their membrane structure and growth rates, and disintegrated cellular proteins. The affected nerve cells also formed abnormal patterns of ‘sprouting’ known as ‘neurofibrillary aggregates’, which are typically observed in the brains of Alzheimer’s patients.6
There’s also anecdotal evidence from people who’ve had their amalgam fillings removed and then experienced sudden improvements in chronic health problems. Six separate surveys involving 1,569 patients, all of whom had gone through amalgam removal, reported improvement—or, in some cases, complete reversal—of a range of problems, such as chest pain, depression, fatigue, gastrointestinal issues, migraine headaches, MS, memory loss and irregular heart beats, or arrhythmias.7
There is also further smoking-gun evidence from dental clinics themselves. Dental assistants reported significantly higher levels of neurological and psychosomatic problems, memory loss, inability to concentrate, fatigue and sleep disturbances than did healthcare personnel not regularly exposed to mercury fumes.8
While definitive proof that mercury from fillings causes serious health problems may never become available, there’s enough evidence to raise the question: why should you even take the risk, especially when safer alternatives are available?
A dental paradox
There’s one chronic condition that amalgam fillings can cause: periodontal, or gum, disease.
At least nine separate studies have demonstrated that they are causing gum problems, says the University of Calgary’s Clinical Associate Professor Murray Vimy.
“Periodontal disease is one of the most prevalent chronic diseases in man, and mercury fillings contribute significantly. The ADA [American Dental Association] and its advisors may be knowingly misinforming the public through the media, or they lack the understanding of the scientific research about mercury release from amalgam published in their own journals,“ he says.1
The yes boys take over
Amalgam was controversial almost from the day it was first formulated (it’s a mix of silver, tin and copper in liquid, or elemental, mercury). It was seen as a more pliable, durable and less costly alternative to gold, which was then routinely used to fill cavities.
But from the outset, leading American dentist Chapin Harris refused to handle the new material, describing it as “one of the most objectionable articles for filling teeth that can be employed”.
America’s first dental association, the American Society of Dental Surgeons, which Harris had co-founded in 1840, disbanded over the controversy in 1856 and was eventually replaced by the American Dental Association in 1859. The ADA was more welcoming of the new material—and remains so to this day.
Women and children first
Only people with a ‘mercury allergy’ or sensitivity to mercury are at risk from its effects, and that’s just 3 per cent of the population, say the dental associations. Even then, that’s still a substantial number of people, equating to around 1.8 million people in the UK and 9 million in the US.
The only others who should avoid amalgam fillings are pregnant women and new mums who are breastfeeding. As for the rest of us, our kidneys will take care of any mercury and it passes through us every day—or so the dental associations tell us.
But the World Health Organization isn’t so sure; in one study, WHO researchers discovered that people with the most amalgam fillings—which were leaching
up to 100 mcg of mercury every day—were excreting just half that amount in
This inefficient clearing may be down to age. One study of 507 schoolchildren (ages eight to 10) found that those with amalgam fillings had significantly higher levels of mercury in their urine during the first two years of follow-up. But over the full seven years of follow-up, their levels were not significantly different from those in children who had received resin composite fillings instead. This suggests that these children’s bodies had the ability to shed the toxic mercury load.2