Antimandibular deformity, commonly known as “geodontia” and “pocket tooth”, is a common developmental malformation of the teeth and jaws. Severe antimandibular deformity not only affects appearance, but also affects eating and speech. With the development of craniomaxillofacial surgery technology and the continuous improvement of surgical instruments, the treatment of antimandibular deformity caused by skeletal development through surgery can receive good surgical results. I. When do I need surgery? For a patient with an antimandibular deformity, the cause of the antimandibular deformity must first be clarified. Overall, there are two types. One is simply caused by the misalignment of teeth, with normal development and position of the upper and lower jaws, which is medically known as “dental malformation”, and this type of malformation does not require surgery, and only requires a dentist to rearrange the teeth. On the contrary, if the antimandibular deformity is caused by abnormal development of the upper and lower jaws, which is called “bony deformity”, it needs to be treated surgically. In most cases, bony deformities are accompanied by varying degrees of dental deformities, and it is difficult to achieve the desired effect if the teeth are simply aligned without surgical correction of the abnormal jawbone. II. What are the conditions that can lead to antimandibular deformity? 1. Excessive development of the lower jaw (mandibular protrusion) This type of antimandibular deformity is mainly manifested by the overgrowth of the lower jaw, and the lower jaw is steep and long when observed from the side. Some patients also have an oblique lower jaw at the same time. In addition to the antimandibular deformity, most of the patients have different degrees of depression in the middle of the face and lack of three-dimensional feeling. 3. Maxillary recession with mandibular protrusion The antimandibular deformity of these patients is usually more serious. The timing of surgery and pre-surgical preparation for antimandibular deformity should be performed after the jaws of the patient have developed into a definite shape, usually after the age of 16-18. Before surgery, X-ray examination should be done first to understand the development of upper and lower jaw deformity, and through measurement, to determine whether the antimandibular deformity is due to overdevelopment of the lower jaw, recession of the upper jaw or both conditions? to determine the surgical plan. Then upper and lower jaw occlusal models were taken to analyze the upper and lower jaw occlusal relationship. If the occlusal relationship is too misaligned, orthodontic treatment should be done in dentistry before surgery to rearrange the crowded and misaligned teeth in preparation for the later surgery. The surgery requires general anesthesia and is performed through an intra-oral incision, leaving no scar on the exterior. For the antimandibular deformity caused by mandibular protrusion, the surgery mainly targets the mandible, and the whole mandible is set back to correct the mandibular protrusion through a special osteotomy, thus achieving the purpose of correcting the antimandibular deformity. By receding the jaw bone, the length of the jaw is shortened and the upper jaw is rotated upward at the same time, resulting in a smaller angle of the jaw and a more beautiful side view. If the chin is too long, the chin bone should be shortened at the same time. 2. In the case of retrusion of the upper jaw, maxillary osteotomy is needed to correct the retrusion of the upper jaw through a special osteotomy. At the same time, the anterior displacement of the maxilla also significantly improves the depression of the middle part of the face. After correction of the antimandibular deformity, individual patients with a low nose can further increase the three-dimensionality of the middle part of the face through rhinoplasty. 3. For patients with antimandibular deformity who have both maxillary recession and mandibular protrusion, maxillary osteotomy and mandibular osteotomy recession should be performed at the same time, and chin osteotomy is also needed if necessary. V. Follow-up treatment after antimandibular deformity After surgery, rubber band elastic traction is used between the upper and lower jaws for 8-12 weeks to maintain the position of the upper and lower jaws and consolidate the surgical effect. The traction is then removed and the occlusal relationship is further adjusted in the dentistry department. Was the diagnosis of bony maxillary hypoplasia made first and where was it made? Is there a family history? Is the lower jaw development normal? 1. If the maxillary hypoplasia is pure and the lower jaw is normal, the anterior traction effect is positive. As for the traction angle, it is related to the angle of the mandibular plane and the depth of the overlying jaw, generally 15 degrees is used more often. Wear 12-14 hours a day, the face frame should be adjusted appropriately, whether the maxillary expansion arch, depending on whether there is really maxillary stenosis. 2. If the upper jaw is normal and the lower jaw is protruding, the diagnosis is wrong. The result will be bimaxillary protrusion. 3. If the upper jaw is underdeveloped with an overdeveloped lower jaw, the treatment effect after traction depends on the development of the lower jaw during the rapid development period. After anterior traction treatment, the jaw should be reviewed once every six months to observe the development of the lower jaw until the age of 15. If the retrusion is found again, timely treatment is required, and if it is true bony mandibular protrusion, surgical treatment is required. Functional orthodontic appliances have a positive effect on the underdevelopment of the upper and lower jaws, but there is no good treatment for the overdevelopment of the lower jaw.