Amalgam is the generic term applied to the silver-mercury filling commonly used in dentistry to restore teeth. Amalgam is also known as the "silver filling" (due to its shiny appearance) or the silver–mercury filling. Amalgam literally means mixed with mercury and in the dental sense that is true. Powdered metals and metal compounds consisting of silver, copper, tin and zinc are mixed with about an equal weight of liquid mercury. Three different types of chemical reactions take place within this mixture and the resultant silver-mercury amalgam will set at room temperature and, most importantly, within a few minutes.
Silver-mercury amalgam has been used as a filling material for 160 years and has enjoyed the reputation of being an inexpensive, long lasting filling. The materials alone only cost about one dollar. Although the average life span of a silver-mercury amalgam filling is only around five years, according to Dr. Leon Silverstone at the University of Colorado School of Dentistry, some amalgam fillings have been known to last for up to 20 years.
Three times now, mercury from fillings has been accused of initiating diseases. The first time was in the 1830s, again in the 1920s and the third time a movement started in 1973 in which more substantial information has been available to determine the toxicity of mercury. Up until recently, it was felt that the mercury stayed within the filling. Now it is known that mercury leaches out every minute of the day.
Mercury comprises about 50 percent of the most common filling in the world called silver-mercury amalgam. Amalgam also contains copper, tin, silver and zinc. It is silver colored when first placed; therefore, the name, "silver" filling. After it has been in the mouth, mercury fillings begin to tarnish. The blacker the filling, the more tarnish has taken place. Silver-mercury fillings have an electrical current which can be measured. The higher the current, the faster mercury is being released. As of 1976, the new ADA sponsored (and patent holder) high copper mercury amalgam started taking over the market. Mercury is released 50 times faster from high copper (around 30 percent) amalgam than the "conventional" silver-mercury amalgam of before that time.
Currently dental amalgam fillings contain around 48 to 51 percent mercury by weight. Copper comes in second with the high copper amalgam now leading the markets. Copper can be from 24 to 33 percent of the amalgam. The higher the copper level, the faster the mercury and copper - both - are emitted from the fillings. If a gold crown is anywhere in the mouth, mercury comes off faster. According to university studies done by Dr. Chew, over the first two years after placement, amalgams release bout 34 micrograms of mercury per filling (per square centimeter of filling exposed) per day. These tests were done of silver-mercury fillings sitting in water and tested daily.
There are many things that make mercury come out faster. As just mentioned, any other metals such as gold crowns, nickel crowns and removable bridges will increase the speed of release of mercury. Chewing foods increases the emissions, dramatically. Hot liquids, like coffee, increase the release by thousands of percent, but only for 10 or 15 minutes. Abrasion from chewing gum increases the release of mercury by 1500 percent as published. Abrasion during the grinding of teeth during waking or sleeping hours, called "bruxism," also releases mercury vapor.
Compression of the filling from chewing releases mercury into the mouth. The electrical charge on a filling gives a hint as to how fast mercury, copper and other metals are being released. The higher the current measured, the faster the mercury release. The total amount of mercury released would be difficult to measure, but suffice it to say that the current measurements are adequate to contribute significantly to disease processes and the actual total mercury release in a living human being with saliva (which has a much higher electrical potential with dissimilar metals than water), in a warm , with acidic foods, bruxism, chewing gum, eating foods and several hundred bacterial strains is greater than any of today's estimates.