A “cap” or a crown can be made out of gold, porcelain fused to metal, or all porcelain. A crown covers the entire tooth. There are several reasons why a tooth might need a crown. One reason can be when an old filling and the decay underneath it is removed there is not enough tooth structure left to hold another filling. Another reason is after a root canal procedure is completed, the tooth becomes brittle and like a dead branch and can easily crack and break unless it is fully covered. Having professionally applied fluoride treatments after your dental cleaning, as well as using a fluoride rinse at home, is also helpful to protecting your crown from decay.