Science Fair Project Encyclopedia
- This article is about the alloy. For the comic book series, see Amalgam Comics.
Amalgam in Dentistry
For centuries dentists have been cleaning out decay and filling cavities, using filling material such as stone chips, resin, cork, turpentine, gum, lead and gold leaf. The renowned physician Ambroise Pare (1510-1590) used lead or cork to fill teeth. Amalgams were the first true standard filling material.
Mercury amalgams are used in dentistry because they are cheap, easy to use, durable, and were widely regarded as safe. They are made by mixing approximately equal measures of mercury and an alloy of silver, copper, tin and other metals.
The first people to use amalgams to fill cavities appear to be the French. In 1816 Auguste Taveau developed first dental amalgam from silver coins and mercury. This early amalgam was low in mercury and had to be heated in order for the silver to dissolve at any appreciable rate. Modern dental amalgams are mixed cold. Current dental amalgams now contain copper to eliminate the gamma-2 phase of the silver-mercury-tin alloy. The gamma 2 phase is weaker than the other phases so a high copper, low gamma 2 dental amalgam has superior strength.
After all the usable metal had been extracted from the ore, mercury was poured down a long copper trough which formed a thin coating of mercury on the surface. The waste ore was then poured down the trough, and any gold in the waste amalgamated with the mercury. This coating was occasionally scraped off and distilled to remove the mercury, leaving behind fairly high purity gold.
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