A tooth can lose it normal shape and size for a variety of reasons. some reasons include decay, cracks and broken tooth structure and abnormal wear.
There are times when a tooth, having been filled years ago, is now failing do to recurrent decay and formation of cracks. When the filling needs to be replaced and there is more filling than there is tooth, a crown becomes the superior choice for a new restoration.
A crown covers the entire tooth to restore its original shape and size.
A crown is a very durable restoration that will greatly increase the strength of your remaining tooth and if done in porcelain can provide outstanding esthetics