The February 2013 issue of controversial publication What Doctors Don’t Tell You (WDDTY) lead on the headline “New dental mercury dangers – What you need to know about for safe fillings”.
I found this surprising for a couple of reasons. Firstly, your doctor really isn’t the right person to talk to about dental treatment (so, in this, at least, the magazine’s title is correct), but also that this is deemed more important than the amazing discoveries that Vitamin C can cure AIDS and that there are ‘11 foods that kill cancer.’
Before I start to dig deeper into their claims, in the interests of disclosure, you should all know that I’m a dentist (and therefore clearly in the pay of Big Dental, whoever that may be). I place (not exclusively) amalgam fillings almost every day, and if WDDTY had approached me or any of my thousands of registered colleagues, they may have come out with a better article.
I want to concentrate, for now, on the main claim of the article. The lead-in to the first paragraph reads: A person with a dozen amalgam fillings is absorbing around 1.83 mcg of mercury a day, but this escalates to 27 mcg in someone with 47 amalgam surfaces, assuming some teeth have more than one filling.
The claim, which is repeated in the body of the article, is backed up with references to two papers: ‘Factors Affecting Estimation of Dental Amalgam Mercury Exposure from Measurements of Mercury Vapor Levels in Intra-oral and Expired Air’ from the December 1997 issue of the Journal of Dental Research; and ‘The Contribution of Dental Amalgam to Urinary Mercury Excretion in Children’ from Environmental Health Perspectives, 2007. Interestingly, the WDDTY article doesn’t give the titles of the papers in their references section. It’s worthwhile noting that researchers in New England found no significant effects on the neuropsychological function of children at 5 year follow-up.
I haven’t been able to get a copy of the JDR paper (and don’t think it’s worth the $32 they want for access), but the take-home message from the abstract is ‘The corrected estimates for daily dose of mercury from amalgam restorations are a factor of sixteen lower than those previously reported.’ Surely it couldn’t be right that WDDTY have deliberately used figures they know may be out by a factor of 16? (If anyone can get a copy of the full paper, so I can look into this in a bit more detail, please get in touch.) The difficulties in estimating mercury release from dental amalgams are discussed in depth here (abstract here).
The second paper is interesting. The results show that mercury excretion in urine drops to baseline readings after 7 years after peaking at year 2. Although this does appear a long time, this is insignificant if the levels are low enough to be non toxic. Moreover, this is somewhat questionable as a more commonly quoted half-life for mercury excretion is just 55 days1. None of this takes into account the various factors that may affect the amount of mercury being released from an amalgam filling.
So, we know that the figures given by What Doctors Don’t Tell You are dubious at best, but what’s this about 47 amalgam surfaces? What does that even mean? Lets learn some dental anatomy.
There are four types of teeth in the human mouth. These are incisors, canines, premolars and molars. Each of these teeth has five separate surfaces; to spare you any technical jargon, let’s call them the front, back, inside, outside and biting surfaces.
A simple single surface amalgam would occupy part of one of the surfaces of these teeth, usually the biting surface. A two surface filling would occupy part of two surfaces, usually the biting surface and the front or back surface. This can escalate until all five surfaces can be filled. Of course this classification does not account for different sizes, depths or exposed surface areas of fillings, or the different formulation of amalgams present, but it’s all we have here. What ‘47 amalgam surfaces’ doesn’t necessarily mean, is that some teeth have more than one filling. Rather that some fillings occupy more than one surface.
If we have a full complement of 32 teeth, then there are 160 available surfaces to be filled, and 47 surfaces would involve 29% of your mouth being restored with amalgam, right?
Well, it’s not quite that simple.
Amalgam is generally only used for the posterior teeth, that is the molars and premolars. That instantly cuts down the available surfaces to just 100 (that’s 12 molars if the wisdom teeth are present and 8 premolars) which would bring this 47 amalgam surfaces much closer to half the available surfaces to be filled.
Now, if someone has such a high rate of decay as to require this number of restorations, I would be willing to suggest that they may have lost at least one or more teeth through their lifetime (especially as anyone with this amount of treatment experience is likely to be at least middle aged) and of course they may never have had their wisdom teeth to start with.
Essentially, anyone with 47 amalgam surfaces filled is more likely to be older, have poor dental health in the first place, quite possibly have a poor diet and be of a lower socioeconomic class. Is it OK to suggest that they have bigger issues at hand than a few amalgams? Even if not, then it is unrealistic to suggest 47 amalgam surfaces is normal.
So far, then, we have questionable figures for the amount of mercury released from amalgam fillings and an overstatement on typical levels of amalgam present in the mouth. The WHO estimate that for most people in the USA and Canada, the exposure to mercury from dental amalgam is less than 5 mcg/day2. Of course, exposure to does not equal absorption of. Let us assume for one minute, though, that these figures are honest. How does that compare with what is safe?
In the same CICAD document as cited above, the WHO state that the average inorganic mercury intake is roughly 4.3 mcg/day. For an average sized adult, this would be 3% of the tolerable intake. We can see then, that even the maximum intake suggested in What Doctors Don’t Tell You would be less than 30% of the tolerable intake for an average person. Further research shows that the steady-state release of a single surface amalgam is just 0.03 mcg/day.
What Doctors Don’t Tell You has presented inaccurate values for mercury levels, unrealistic figures for amalgam surfaces (and used jargon to describe this when an easy explanation would have been favourable) and given no reference to the figures they’ve provided. Mercury is undoubtedly toxic, and I can see a day, fairly soon, when use of amalgam will be banned, but not for the reasons that have been produced here. In addition, some of the suggested ‘detox’ solutions for the claimed amalgam toxicity are beyond belief, but that’s for another blogpost…
1. Roberson TM, Heymann HO, Swift EJ. Sturdevant’s Art and Science of Operative Dentistry. 5th ed. Missouri: Mosby Inc; 2006. pp. 151–64.
2. CICAD 50: Elemental Mercury and Inorganic Mercury Compounds: Human Health Aspects. http://www.who.int/ipcs/publications/cicad/en/cicad50.pdf