Dental amalgam is a dental filling material used to fill cavities caused by tooth decay. It has been used for more than 50 years in hundreds of millions of patients. Dental amalgam is a mixture of metals, consisting of liquid mercury and a powdered alloy composed of silver, tin, and copper. Approximately 50% of dental amalgam is mercury by weight. Dental amalgam fillings are also known as “silver fillings” because of their silver-like appearance.