why are mercury containing amalgam tooth fillings considered safe despite mercury being extremely toxic?
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The properties of elements change wildly when those elements form chemical bonds with other elements. It’s why hydrogen (a flammable gas) and oxygen (a flammable gas) are not flammable when they are bonded in water, and why sodium (a violently reactive metal) and chlorine (a poisonous gas) are not deadly to consume as table salt.
[Methylmercury](https://en.wikipedia.org/wiki/Methylmercury) (organic mercury) is a common compound of mercury that is both extremely toxic and transfers through food; it usually takes special kinds of underwater bacteria to turn mercury into it. It is also very much *not* metallic mercury. It’s close cousin, dimethylmercury, is the one that is scary (can kill somebody that touches it with gloves on).
Metallic mercury is still toxic and can technically be picked up from fillings, but almost all of it is bound up by the other amalgam ingredients; getting any into your system would require getting the other metals in as well, and even then they would tend to stick together instead of interacting with your body. So the benefits of mercury and the risks of rust or other metals outweigh the risks of mercury amalgams. However, the potential risks are enough some countries ban its use.
Concerning science, current studies don’t have sufficient rigor to draw a certain conclusion. This means that even if it’s a good idea to phase out its use, amalgam won’t shorten anybody’s life enough to be noticeable. Wikipedia has a [page on the subject](https://en.wikipedia.org/wiki/Dental_amalgam_controversy).
In Norway it was made illegal in 2008 thankfully, i would think most “modern” countries would not use such materials any more when better alternatives exist by far.
Mercury is toxic if you get a lot at once, but it doesn’t add up over time the way lead poisoning does. Your body can filter out a small dose of mercury in weeks or months, and then you’re fine and haven’t been hurt at all. As long as the fillings in your teeth release mercury slower than your body gets rid of it, they won’t poison you.
I’m a dentist and I’ll try to give as concise an opinion as I can:
My cards on the table first. I’m not ‘Pro-amalgam’, I’m pro-evidence.
I hardly place amalgam fillings anymore, probably only about 6 in the last year. There are some of my colleagues who will have done more amalgams in half a day of work this morning than I have in 12 months.
The reason isn’t because I consider amalgam to be dangerous, but because I believe there are now better materials out there, combined with the fact that most people prefer aesthetic white fillings.
Some salient points:
Many studies on toxicity are on free mercury rather than bound mercury in amalgam, which is a different beast.
Blood and urine levels of measured mercury may not be helpful as a measurement at all.
Only a correlation to illnesses is meaningful. And over 50 years of serious research has not found any correlation between the two.
The greatest ingestion of mercury comes from fish (esp larger fish like tuna). And this is in the more toxic form of methylmercury, which easily crosses the blood-brain barrier and accumulates there , not being excreted and so doesn’t show up in urine analysis.
There’s a good environmental reason to reduce our usage of mercury amalgams but to claim that it is a danger to public health is unsupported, unscientific bollocks.
(Wait till you find out what’s in the ‘safer’ white fillings. It’s a cytotoxicity party mate).
You know how chlorine is extremely toxic to all life? And how sodium will burst into flames in water? Yet you eat NaCl all the time and in fact cannot survive without it. Compounds can have significantly different physical and chemical properties than the elements they are made of. Chlorine is extremely electronegative – it only has 7 electrons in the last shell and needs to complete it by reacting with pretty much anything. It reacts with sodium, “takes” that electron and is presto….at peace. NaCl is pretty inert – it will sit on your counter and happily not eat through metal, not burst into flames, not suffocate you because the reaction has already been completed. Similarly with Hg – it’s toxic because it replaces other things in metabolic pathways, the main one being inhibition of some enzymes. But Mercury amalgams are “pacified” – it already reacted with something else (like silver, tin etc), and for the most part (even after hundreds of years of use, there’s still lack of research) do not release elemental mercury in the organism.
Pure elemental mercury is liquid at room temperature. If you were to [swallow liquid mercury](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5001828/), you’d probably be okay. Pure elemental mercury mostly just goes through your digestive tract and out the other end.
[It’s not that uncommon for amalgam fillings to come out and be swallowed.](https://www.collinsdental.com/blog/harmful-mercury-filling-swallowed/)It’s not terribly dangerous if this happens- it’s just passed through your digestive tract, and comes out the other end.
Mercury vapor is much more dangerous than swallowing mercury. If you get an amalgam filling removed, that releases mercury vapor. There’s not really enough of it to do much to you, but dentists who put in and remove lots of amalgam fillings might be a different story.
The mercury is locked away in a compound that will not be made available to the body’s cells.
Pure metallic mercury also isn’t too poisonous (short external exposures), as it has a hard time absorbing and becoming available.
But something like dimethyl mercury is in a compound that is instantly absorbed through skin (and through gloves) and into the body. Like one drop on the skin and you’re likely going to die, which has happened.
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