An organic acid produced by bacteria dissolves away the hard outer covering of our teeth. Fillings are a man-made material designed to fill in or restore the damaged areas of decayed teeth. Although not normally recommended, fillings can also replace areas of teeth that have been damaged by fracture. Broken teeth are usually best restored with crowns .
Fillings can also repair areas of wear caused by brushing too hard and other habits.
Dental amalgam is a mixture of metals used to fill back teeth. Most people know amalgam fillings as silver fillings, as this is one of the major metals in the amalgam filling. One of the metals in the mixture is a small amount of mercury which has led some uninformed people to say that dental amalgam is dangerous. When mercury is combined with the other metals in dental amalgam, its chemical nature changes, forming a hard dense metal mixture. There is much less metalic mercury in dental amalgam than what patients are exposed to in food, air, and water.