Fillings (restorations) are usually made up of either either composite (white) or amalgam (metal) materials and are the main treatments used to restore lost tooth structure due to decay or breakage (fracture). While amalgam fillings are still used, white fillings are most common, and dentists will pick the filling material to match the colour of your teeth enabling the filling to blend in and also naturally shape the filling to help restore function of the tooth.
Amalgam fillings are often removed and replaced with the modern composite filling.