Amalgam fillings are an alloy of mercury (from 43% to 54%) along with silver, tin, and copper. Mercury-based fillings were apparently first used by French dentists in the 1810s. They continue to be used in some countries because of their hardness and durability and because they are inexpensive.
Mercury vapor is toxic, and the use of amalgam fillings is therefore controversial, as the fillings do emit mercury as a minute amount of vapor. Some government agencies, including the UN's World Health Organization and Centers for Disease Control and Prevention, claim that amalgam fillings are safe, even for pregnant women, children, and diabetics, except in rare cases of allergy. The Food and Drug
Administration has never approved amalgam for use in dental fillings and is meanwhile opposing its use but amalgam fillings are legally considered "devices" and therefore outside the regulatory control of the FDA.
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