Silver amalgam fillings consist of between 48 and 52% inorganic mercury and 20% silver, with the remainder a mix of copper, tin and zinc. Some people may be particularly sensitive to any of these elements, including those that are necessary for proper cellular functioning, but of all these mercury is the most highly toxic.
There really is no safe level of exposure to mercury, though just how much exposure it takes to cause adverse effects varies from person to person. Some people are able to eliminate mercury from their bodies effectively, which may explain why some people can tolerate more exposure to the metal. Even in these individuals, mercury can still build up to a point where it will cause negative effects (San Diego residents should see their local dentist to remove amalgams).
To explain how mercury from fillings ends up in the body, it is important to realize that mercury acts more like a liquid than other metals. If you leave mercury on a table, it will evaporate just like water. Higher temperatures will cause the mercury to evaporate more quickly. This evaporation, known as off-gassing, occurs with all mercury fillings, resulting in minute, but constant exposure. The mercury released by fillings is absorbed into the skin, lungs and digestive system and accumulates in the organs and tissues.
If you have mercury fillings and are concerned about your exposure, there are tests that can determine how much mercury you have in your body. Your test results can help your health care provider develop a plan to help you remove the mercury that has accumulated in your tissues. The plan may include removing your fillings and replacing them with a more biocompatible alternative, some kind of chelation therapy, a combination of these or something else. Regardless of the plan, the test can offer a baseline against which results of future tests can be compared to be sure levels are going down.
For the record, neither white nor gold filling materials are necessarily always biocompatible. The best material for one person may not be ideal for another. A Holistic dentist may suggest testing to determine the best material for you.
Many people are exposed to mercury from other sources than metal fillings, including fish consumption and occupational sources. When it comes to fillings, there is a significant difference in exposure depending the on the surface area of the filling. Large fillings, as one might expect, will result in higher levels of exposure than smaller fillings. As mercury tends to accumulate, the length of time the filling is in place, while it may not matter in terms of daily exposure, is significant in terms of how much mercury is built up in the organs and tissues.
A final note, if you are also exposed to lead or other heavy metals, the toxic effects may be several times the effects of exposure to any single heavy metal.