Crown lengthening is a surgical procedure performed by a dentist to expose a greater amount of tooth structure for the purpose of subsequently restoring the tooth prosthetically. This is done by incising the gingival tissue around a tooth and, after temporarily displacing the soft tissue, predictably removing a given height of alveolar bone from the circumference of the tooth or teeth being operated on. While some general dentists perform this procedure, others frequently refer such cases to periodontists. https://www.youtube.com/watch?list=TLGGV83bWZgIeagwNTEyMjAyMg&v=v54KFzqOi_8