A crown, which some people refer to as a "cap" is generally a tooth colored shell that fits over a carefully prepared existing tooth. In many cases the crown is made of porcelain or a combination of porcelain over a metal substructure. Its purpose is to protect and strengthen weakened tooth structure that may be present from decay or tooth fracture. Once the crown is placed on the tooth it acts much like a thimble that is placed on your finger to prevent further damage from occurring to the tooth.
The benefits include: