Amalgam (silver filling material) is the traditional, time tested restorative material for the treatment of dental caries, or dental cavity   that dentists have used for hundreds of years that is composed of varying percentages of liquid mercury and silver-tin-copper-zinc alloy powder. Shortly after it is placed in tooth, the mixture self hardens and can last for many years. Advantages of Silver filling are that they are less expensive than composite resin filling material, it is easier and faster to place in tooth.

Advantages
(1)   Amalgam fillings are strong and can withstand the forces of chewing. 
(2)   They are relatively inexpensive, compared with alternatives.
(3)   An amalgam filling can be completed in one dental visit.


Disadvantages
(1)  Silver filling doesn't match the color of teeth. 
(2)  Healthy parts of tooth often must be removed to make a space large enough to hold an amalgam filling.
(3)  Amalgam fillings can corrode or tarnish over time, causing discoloration where the filling meets the tooth. 
(4)  A traditional (non-bonded) silver filling does not bond (stick) to tooth. The cavity preparation developed by dentist requires undercuts or ledges to provide retention of the filling. Dentist may have to remove additional tooth structure to establish good retention for the filling.