A mixture of metals used to fill/ restore a cavity. Amalgam restorations are commonly called silver fillings or Mercury fillings. They are very stable restorations which have been safely used for many decades. The advantages of them are they are inexpensive, long lasting and technically forgiving to place. The disadvantages of them are they can turn dark over time and are not aesthetically pleasing to most people. Note while these restoration do contain Mercury which is poisonous in its unbound form, amalgam restorations are not poisonous. The Mercury is not poisonous when it is chemically bound to other metals as it is in amalgam fillings. It is very safe in this combination. Here is an analogy to help clarify this point. Pure (unbound) oxygen is highly explosive, but when combined (Bound) to Hydrogen it become water which is not at all explosive