Bone grinding and face slimming to change the shape of the face is a hot spot of plastic and cosmetic surgery in recent years, the number of applicants is increasing, and it has become a new growth point of the plastic and cosmetic industry. The so-called change face shape is facial contour plastic surgery, is the application of craniomaxillofacial surgery osteotomy technology, to achieve the purpose of improving the shape of the face, belongs to a kind of plastic surgery. Mandibular angle is an important anatomical structure that determines the width and shape of the lower part of the face. Hypertrophy of the mandibular angle leads to the widening of the lower 1/3 of the face, resulting in a square face or even a trapezoidal face, which is obviously not in line with the traditional aesthetic standard of melon face and ovoid face that is respected by the population in most Southeast Asian countries. Mandibular angle hypertrophy has a relatively high incidence in the Oriental population, mostly occurring bilaterally at the same time, but also unilateral hypertrophy only. It is characterized by a low-slung mandibular angle that protrudes backward and outward. It is more common for jaw angle hypertrophy to be accompanied by different degrees of chewing muscle hypertrophy, as well as buccal fat cushion hypertrophy, facial subcutaneous fat hypertrophy and other factors that cause the lower part of the face to be too wide and bloated. First, the diagnosis of jaw angle hypertrophy 1, subjective evaluation of the patient’s self-knowledge, and exclude obesity, chewing muscle hypertrophy and parotid gland hypertrophy and other causes of the lower part of the face is too wide, in the clenching of the teeth under the state of the chewing muscle is not obvious thickening, recognized by the plastic surgeon. 2.Facial linear measurement through calipers to measure the width of the middle of the face, the lower part of the face, the angle of the angle of the jaw, the distance of the angle of the jaw from the earlobe. 3.X-ray film, panoramic film of the mandible to take the skull front and side positioning X-rays, panoramic film of the mandible to measure the width and angle of the bony mandibular angle. Surgical methods 1, intraoral incision mandibular angle osteotomy This type of surgery is divided into three methods due to the application of different chainsaw handles: the first is the application of the rifling saw to do oblique triangular osteotomy; the second is the application of the right-angle oscillating saw to do horizontal triangular osteotomy; and the third is the use of a split drill or a spherical drill to grind the bone. Advantages include no scar on the face, and part of the chewing muscle or buccal fat pad can be removed at the same time; the effect is obvious for improving the low position of the lateral mandibular angle, but the effect is not ideal for narrowing the width of the lower part of the face. The disadvantage is that it is difficult to operate, it is not easy to grasp the scale of osteotomy, and it has higher requirements for surgical instruments. 2, Intraoral incision mandibular angle sagittal osteotomy For those who are too wide in the lower part of the face, mandibular angle sagittal osteotomy can remove bilateral mandibular angle lateral bone plate, and can reduce the width of about 8mm. the osteotomy should be drilled diagonally outside the mandibular angle, and the external oblique line should be retained, so as to make the mandibular body and the mandible angle to maintain a strong connection, and to avoid the fracture occurred in the postoperative period due to the mild external force. The thin ligamentous bone chisel is as close as possible to the lateral bone plate during longitudinal splitting of the outer plate, so as not to damage the inferior alveolar neurovascularization. 3.Behind ear incision mandibular angle osteotomy The advantages of behind ear incision mandibular angle osteotomy are: the incision is hidden, the scar is not obvious. Disadvantages are: there is a facial nerve trunk traveling under the postauricular incision, damage to the facial nerve trunk may cause serious complications, for the anatomical unskilled doctors and young doctors who have just begun to perform surgery, try not to choose this surgical method. The incision is small, and the osteotomy cannot be performed under direct vision, which makes the operation difficult. 4, mandibular and intraoral joint incision mandibular angle hypertrophy osteotomy mandibular lower edge of small incision plus intraoral incision to remove the mandibular angle only in the jaw left a very small scar, but at the same time has the advantages of easy operation, precise osteotomy, can be accomplished at the same time the chewing muscle and buccal fat cushion part of the resection, to facilitate postoperative drainage and many other advantages. At the same time, it has the disadvantages of extra-oral incision. Causes of complications and their prevention Although serious complications rarely occur in the surgical treatment of mandibular angular hypertrophy, because this is a surgical procedure, the candidates are often very critical of the results of the surgery, and are very concerned about some minor deficiencies. Therefore, the surgeon should have full consideration of the adverse consequences and complications of surgery and do his best to prevent them. 1, asymmetric deformity: because most of the osteotomies are performed under blind or semi-blind vision, so it is difficult to achieve complete consistency in the amount of osteotomies on both sides, so some people prefabricated plexiglass templates before the operation to assist in determining the position of the osteotomy line in the operation, but in the clinical work, it still relies on the experience of the surgeon more. When there is a difference between the two sides of the osteotomy, if the difference is small, the grinding head can be used to polish the side of the osteotomy; if the difference is large, another osteotomy can be made up for it, and the width of the gap between the two osteotomies should be taken into consideration so as not to overdo it. 2.Second mandibular angle: In linear osteotomy, the smaller the angle of the original mandibular angle or the larger the amount of bone amputation are, the more likely to cause the appearance of the lower edge of the mandibular angle after osteotomy, so it is called the “second mandibular angle”. Some of them are not obvious in appearance, but the patients often complain that they have obvious angle when touching, so they have psychological scruples. This can be avoided by polishing the edges of the jaw after the curved osteotomy or straight osteotomy. 3.Hematoma: The most likely cause of hematoma after surgery is the damage to the inferior alveolar neurovascular bundle. Since the neurovascular bundle is in the bony nerve canal, it is often impossible to stop bleeding well, so the reasonable design of the location of the osteotomy line is the key to preventing damage to the inferior alveolar neurovascular bundle. Once the osteotomy site is found to have a tidal wave of blood, it is basically certain that the neurovascular bundle has been damaged, and gelatin sponge should be filled in immediately and compression should be applied to stop bleeding, and the position or direction of the osteotomy line should be adjusted after the bleeding has been controlled, and closed drainage should be left in place postoperatively, with a compression bandage, and the amount of drainage should be closely observed. If the partial excision of the bite muscle is done at the same time during the operation, blood seepage from the muscle residual surface will also cause postoperative hematoma, and the method of ligation followed by excision can be used to reduce the bleeding. Medical bioprotein gel has also been sprayed on the trauma to control blood leakage. In addition, in the extra-oral approach to the lower edge of the mandibular incision, should also avoid damage to the facial artery. 4, crooked corner of the mouth: some candidates in the postoperative period appeared on one side of the crooked corner of the mouth, but most of the symptoms in the facial swelling subsided after the relief or disappearance of the symptoms, indicating that this may be due to the operation of pulling the soft tissues caused by the muscles and (or) facial nerve mandibular marginal branch of the minor injuries. If there is no recovery 3 months after surgery, it means that the mandibular marginal branch of the facial nerve is seriously damaged, which is usually seen in candidates with extra-oral incision, and this situation is often irreversible. It is recommended to carry out facial nerve exploration at an early stage and anastomose the severed facial nerve severed ends, so that it is possible to restore the function of facial expression. 5, perioral skin, mucous membrane damage: in the intraoral approach to the candidates, if not to take protective measures, most of the candidates around the corner of the skin and mucous membrane will be due to the pulling hooks pulling compression or chainsaw burning and grinding and damage, although generally these injuries do not leave scars after the healing, but in the postoperative candidates often complain of pain in the corner of the mouth. For this reason, a sufficient amount of ointment can be applied to the perioral area for lubrication and gauze padding for protection during surgery. Some people use film to protect the perioral area, at the same time, because the film is transparent, so it does not interfere with the operator’s line of sight. 6, dyspnea: many candidates in the postoperative emotional irritability, v. Difficulty in breathing, the most common reason is that the bandage is too tight or improper site. Can be under the chin in the center of the outer dressing will cut a knife, relax the neck of the bandage compression. If the bandage is not tight, or relaxation of the patient still complains of dyspnea, should be considered for the pharyngeal swelling caused by, in addition to giving oxygen, dexamethasone 10mg intravenous drip, should be more closely observe the patient’s vital signs, conditions can be given to the oxygen saturation monitoring. Infection: Infection after jaw angle osteotomy surgery is not common, generally can be avoided by doing a good job of oral cleaning before surgery, strict aseptic operation, postoperative prophylactic use of antibiotics and good oral care. The most common cause of infection is hematoma, so preventing hematoma formation is the key to prevent postoperative infection. 8, limited mouth opening: some candidates still complain that their mouths are still not wide open after the swelling has subsided, which may be caused by the loss of attachment point of the biting muscle and the dysfunction of the power balance of the chewing muscle group; a small number of them may also be caused by the dysfunction of the temporomandibular joints resulting from surgical pulling. Generally in the postoperative mastication function through exercise can be restored, if the long term does not heal, should be invited to the oral and maxillofacial surgery consultation, check the temporomandibular joint. 9.Fracture of mandible: during osteotomy, due to occasional unexpected fracture line at the osteotomy line, resulting in fracture of the ascending branch of the mandible or the body of the mandible, at this time, we should decisively change the surgical program and fix the fracture with titanium plate, if unconditional units, intermandibular ligation can be used for fixation. 10, death: in recent years, because of the jaw angle osteotomy surgery led to the death of patients from time to time, we must warn the beauty seekers, surgery has risks, and even the cost of life. The main cause of death is damage to the extra-mandibular artery during the operation, causing hemorrhage, laxity of the tissues of the floor of the mouth and neck, hematoma of the floor of the mouth and neck, compression of the airway, resulting in obstructive respiratory distress or even asphyxiation and death. Close monitoring is needed after surgery