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Dental amalgam is a liquid mercury and metal alloy mixture used to fill cavities caused by tooth decay. Low-copper amalgam commonly consists of mercury (50%), silver (~22–32% ), tin (~14%), copper (~8%) and other trace metals. Dental amalgams were first documented in a Tang Dynasty medical text written by Su Kung in 659, and appeared in Germany in 1528.〔〔 In the 1800s, amalgam became the dental restorative material of choice due to its low cost, ease of application, strength, and durability. Recently however, its popularity has diminished somewhat. Concern for aesthetics, environmental pollution, health, and the availability of improved, reliable, composite materials have all contributed. In particular, concerns about the toxicity of mercury have made its use increasingly controversial. ==History of use== There are, according to Geir Bjørklund, indications that dental amalgam was used in the first part of the T'ang Dynasty in China (AD 618–907), and in Germany by Strockerus in about 1528. Evidence of a dental amalgam first appears in the Tang Dynasty medical text ''Hsin Hsiu Pen Tsao'' written by Su Kung in 659, manufactured from tin and silver.〔 Historical records hint that the use of amalgams may date even earlier in the Tang Dynasty.〔 It was during the Ming Dynasty that the composition of an early dental amalgam was first published, and a text written by Liu Wen Taiin 1505 states that it consists of "100 shares of mercury, 45 shares of silver and 900 shares of tin." Ever since its introduction in the Western World in the 1830s, amalgam has been the subject of recurrent controversies because of its mercury content. Early amalgam was made by mixing mercury with the filings of silver coins.〔 In 1833 two natives of England, Edward Crawcour and his nephew Moses Crawcour (incorrectly referred to as "the Crawcour brothers"), brought amalgam to the United States, and in 1844 it was reported that fifty percent of all dental restorations placed in upstate New York consisted of amalgam. However, at that point the use of dental amalgam was declared to be malpractice, and the American Society of Dental Surgeons (ASDS), the only US dental association at the time, forced all of its members to sign a pledge to abstain from using the mercury fillings.〔American Society of Dental Surgeons. (1845). ''(American Journal of Dental Science )''. Harvard University. p. 170.〕 This was the beginning of what is known as the first dental amalgam war. The dispute ended in 1856 with the disbanding of the old association. The American Dental Association (ADA) was founded in its place in 1859, which has since then strongly defended dental amalgam from allegations of being too risky from the health standpoint.〔Bremner MDF. (1939). ''(The Story of Dentistry from the Dawn of Civilization to the Present )'' Dental Items of Interest Pub. Co. p 86–87〕 The ratio of the mercury to the remaining metallic mixture in dental amalgam has not always been 50:50. It was as high as 66:33 in 1930. Relative ratios between the other metals used in dental amalgams has also been highly variable. Conventional (or gamma2)-amalgams have 32% silver and 14% tin, and they are most susceptible to corrosion due to their low copper content. Non-gamma2 dental amalgams have been developed that were, however, found to release higher levels of mercury vapor compared with traditional amalgams. Amalgam is the dental material that has the strongest tendency to create galvanic currents and high electric potentials as it ages. The rate of mercury release with the corrosion is accelerated when the amalgam filling is in contact with old restorations or coupled with gold artifacts present in the mouth. In 2008, Sweden, Norway and Denmark deliberated a ban of mercury dental amalgam in favor of composite fillings.〔 Since 1 April 2008, dentists in Denmark are forbidden to use mercury in fillings, except for molar masticating surface fillings in permanent (adult) teeth. The Swedish amalgam ban is for both environmental and health issues, according to the Swedish authorities. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Amalgam (dentistry)」の詳細全文を読む スポンサード リンク
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