Crown lengthening is usually a periodontal cosmetic gum surgery procedure called gingivoplasty to improve the appearance of gums and smile. However, it is also done to correct deformities by reshaping and re-contouring the gums, for functional purposes.
When used to correct a gummy smile it is called dental crown lengthening, and usually targets the upper front teeth. As the name implies, this is done to reduce the amount of gum and increase the surface area of teeth that is seen when you smile. It can also be done to improve the symmetry of an uneven gum line.