Crown lengthening is used for both cosmetic and clinical purposes. During this procedure, excess gum and bone tissue is reshaped to expose more of the natural tooth. Cosmetic crown lengthening is used to correct a gummy smile by elongating the crown of the tooth. Clinical crown lengthening is performed when the tooth is decayed, broken below the gum line, or has insufficient tooth structure for a crown or bridge restoration. Crown lengthening adjusts the gum and bone level to expose more of the tooth, so it can be restored.