Amalgam fillings consist of about 50% highly toxic mercury. In dentistry, this material has been highly controversial since its introduction at the beginning of the 19th century and was even temporarily banned in the USA. However, the use of this material has been able to assert itself primarily due to a lack of cost-effective alternatives. In addition, advocates assumed that mercury was firmly embedded in the fillings. Since a WHO study in 1991, however, it has been confirmed that mercury constantly dissolves from the fillings, more than is absorbed by humans through food or breath.