Often called silver fillings—this material has been known for 500 years and has been a standard in dentistry for two centuries. Modern dental amalgam is an alloy of silver, tin, copper, and mercury. It forms a durable, corrosion resistant, alloy when condensed into cavities prepared by the dentist. Very large defects can be restored with it, but it is metallic in appearance and some people object to it because it is nearly 50% mercury, a toxic, somewhat absorbable metal. Proper precautions when using it are required for safety of the dental team and patient. It still has some important applications, but most people now prefer to have fillings made with composite resins.