Cosmetic Crown Lengthing
You may have asked your dentist about procedures to improve a "gummy" smile because your teeth appear short. Your teeth may actually be the proper lengths, but they're covered with too much gum tissue. Crown lengthening may be performed to correct this.
During this procedure, excess gum and bone tissue is reshaped to expose more of the natural tooth. This can be done to one tooth, to even your gum line, or to several teeth to expose a natural, broad smile.

Non-Cosmetic Crown Lengthening
Crown lengthening may be performed to make a restorative or cosmetic dental procedure possible. Often a tooth may be decayed, broken below the gum line, or has insufficient tooth structure for a restoration, such as a crown or bridge. Crown lengthening adjusts the gum and bone level to expose more of the tooth so it can then be restored correctly.