Mercury makes up about 50% of the most common fillings in the world called Silver-Mercury amalgam fillings. This amalgam material also contains other metals such as Zinc, Copper, Tin, and Silver. Because of the high Mercury content, these fillings are Silver in color when they are first placed. Hence the name, “Silver” filling. After being in the mouth for a bit of time, it is at that point that the Mercury starts reacting chemically. Thus, resulting in black corrosion. The darker the filling, all the more tarnish that has taken place. These fillings do have an electrical current that can be measured.
