Crown lengthening, also known as crown lengthening, is performed mainly by means of periodontal surgery to bring the alveolar bone and crown back into a harmonious position. The gums are usually done with a simple flap and then the shape of the alveolar bone and the height of the alveolar bone are trimmed and re-sutured. It is a relatively simple procedure and the surgery time is short, usually 1-1.5 hours to complete. Usually when the tooth is decayed below the gum, the patient will be recommended to have crown lengthening. Because if the decayed end is below the gum, it will obstruct the cleaning of the tooth and increase the chance of the tooth decaying in the future. Therefore, it is necessary to expose the decayed end beyond the gum so that the oral hygiene can be maintained by simply brushing the teeth. In addition, some patients feel that their gums are swollen, uncomfortable and bleeding frequently after having porcelain teeth. Such a condition may be due to the fact that the edge of the crown has extended below the gums, repeatedly irritating the gums and causing inflammation and redness. This is also a good time to consider crown lengthening to trim the gums below the edge of the crown and reduce inflammation. Some teeth that have unfortunately fractured, with the broken end of the fracture below the flesh, are also an indication for crown lengthening at this time. Because this compresses the gums, it is also important to expose the fractured edge beyond the gums to allow for cleaning and preservation of the tooth.