Final answer:
Amalgam restorations are primarily a combination of mercury, silver, tin, and copper. Approximately 50% of a dental amalgam's weight is mercury, which binds well with the other powdered metal alloys.
Step-by-step explanation:
Amalgam restorations are a combination of mercury with one or more other metals. The correct answer is that an amalgam is a combination of mercury and multiple other metals, primarily silver, tin, and copper. Dental amalgams are approximately 50% mercury by weight. Mercury is used because it binds well with the solid metal alloy, and the powdered alloy to which mercury is added usually consists of silver, tin, and copper with small amounts of zinc.