The term 'silver filling ' is a misnomer as a 'silver filling' contains 50% pure mercury and 35% silver with the remainder being made up of copper, tin and zinc. The mercury is the same metal that has been banned from thermometers in hospitals, schools and throughout industry because of its toxicity.

These fillings were originally used about 150 years ago as a cheap alternative to gold - the most common material in use at the time - which was too expensive for the vast proportion of the population. Consequently, 'silver fillings' were seen as the cheap alternative to gold. Even then, there was concern about the toxic affects of the mercury in the fillings and, although various dental associations banned its use at the time, economic forces won the day.

As each 'silver filling ' contains approximately 750-1000 milligrams of mercury, and other metals in the filling include silver, copper, zinc and tin (1), these fillings would more accurately be called mercury fillings. 75-80% of all tooth fillings are of this type (2).

At Dental School we were told that, once the filling was mixed, the mercury was locked into the filling and would not escape! Recently the British Dental Association admitted that the mercury in the filling does indeed escape.

The escape of mercury is affected by many things:

• Once covered with saliva the fillings begin to corrode (commonly known as rusting) and this releases mercury from the filling as well as ionic silver, copper and tin, which in themselves are toxic.
  
  
• Chewing and grinding releases more mercury vapour and microscopically small pieces of filling break off which are swallowed and then retained in the gut and slowly absorbed into the body.
  
  
• Increases in temperature cause more mercury vapour to be released, so hot food and drinks increase the amount of mercury vapour released. So each time you eat or drink you are increasing your exposure to mercury.
  
  
• If your mouth has more than one type of metal in it, i.e. gold crowns or fillings as well as 'silver fillings', then a battery is set up which causes currents 100-1000 times stronger than the electrical currents utilised by the brain. In addition, due to the currents released, the more volatile of the metals is released from the filling, in this case mercury vapour!
  

The above reasons explain why 'silver fillings' continuously release mercury vapour and its compounds into your mouth.

This low level, continuous, exposure to mercury vapour may be adversely affecting your health as even minute amounts of mercury vapour are very toxic.

The Environmental Health Criteria 101: methylmercury (WHO 1990) gives the following as estimated daily intakes of elemental inorganic and methylmercury.

Estimated average daily intake and retention (ug/day) of total mercury and mercury compounds in the general population not occupationally exposed to mercury, the figures in parenthesis are the estimated amount (ug) retained by the body of an adult.

No government department or authority anywhere in the world has ever certified 'silver fillings' as safe for use in humans, so we have no assurance that these filling are safe to use.

A risk assessment was recently carried out for the Canadian government by Dr. Richardson, a well respected risk assessor, who used all the available scientific data and came to the conclusion that up to 2 fillings in children and 4 fillings in adults would be an acceptable risk. Any more than this would be an unacceptable risk to the health of the patient.