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Do metal fillings leak?

The Mercury Amalgam Safety Concern

One of the greatest “controversies” about mercury amalgam fillings is whether they leak in the mouth.  Our previous blog has established that even the most conservative agencies will recognise that mercury is toxic, but there are many who still maintain that there is no safety concern because mercury in the mouth is “safe”.


Here is an excerpt from a dental organisation:

  • MYTH BUSTERS MYTH: Dental amalgam is the same as mercury, which seeps into your mouth and poses a significant health risk.
  • FACT: Amalgam is not the same as mercury. There is mercury in amalgam, but not in pure form as it is bound in ‘intermetallic compounds’ of silver, tin and copper. Once the amalgam filling has set, there is no liquid mercury present, and it does not present a health risk. And a leading toothpaste manufacturer has only recently changed their position from mercury amalgams being inert to this: “any amount released from amalgam in the mouth is very low.”

We will address dose and toxicity in a later blog but for now we need to find out “DO METAL FILLINGS LEAK?”

Woman in dental chairTo understand this better we need to know what an amalgam is.  A mercury amalgam filling commonly consists of mercury (50%), silver (~22-32% ), tin (~14%), copper (~8%), and other trace metals.  This is mixed and placed in the tooth cavity and allowed to “set”.  The setting process is a particularly complex one with multiple phases established between the various metal.   It was once widely promoted that the various phases, once set, remained stable and fixed.  There is now enough evidence to show that mercury is NOT bound in these phases permanently and there is a constant release of mercury from fillings and these Phasic Reactions change.  This is made worse by environmental factors such as heat (from drinks or food), chewing (while eating or grinding) and also from the natural corrosion of the metal.  In addition, if there are other metal fillings in the mouth or if they come in contact with another metal source, the galvanic effect can “push” the mercury from its bound form to a free form.  In these instances, the increase release of mercury can be quite significant. (

So mercury can leak into the mouth, can it leak elsewhere? Sadly, because mercury exists as a gas at room temperature, which means the individual atoms are quote small, it can also migrate through the tubules of the teeth (as our teeth are not solid).  This is seen especially in mercury amalgams placed under metal crowns. The different metals lead to a galvanic effect which creates a “charge”.  This charge then “pushes” the mercury into the tubules and canals of the tooth, which can then lead to mercury entering into the nerve/vascular complex found at the apices of the tooth.  It is interesting to note that the Material Safety and Data Sheet (MSDS) of amalgam specifically recommends against placing a metal filling under a metal crown.

Now we know that mercury leaks – both externally and internally – from fillings.  Is this a big deal?  We will address this in our next blog…

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