I. Etiology of dental and maxillofacial malformations Jaw developmental malformation is a lesion that gradually appears during the growth and development of an individual. Its etiology can usually be divided into two categories: congenital factors and acquired factors. The congenital factors are mainly genetic factors and maternal environmental abnormalities during fetal development. Genetic factors have a tendency to run in families, and most individuals of the same blood have common malformation characteristics. In contrast, abnormalities in the maternal environment during fetal development, such as malnutrition during pregnancy, endocrine disorders, injuries or infectious diseases, do not generally have genetic characteristics. However, both can affect the normal development of the dental and jaw systems and lead to malformations. Acquired factors refer to all factors that lead to the occurrence of malocclusion such as metabolic disorders, endocrine dysfunction, infection, injury, malnutrition, local blood supply disorders and bad habits throughout the growth and development stages from infancy to adulthood. For example, bad habits lead to anterior, open and partial dentition. The etiology of maxillofacial malformation may be a single factor mentioned above, but most cases are caused by two or more factors. B. Classification of dental and maxillofacial malformations Clinically, patients with bony dental and maxillofacial malformations mainly have abnormal three-dimensional spatial relationships between the cranium and jaw, the dentition and jaw, and the upper and lower jaws. Common developmental malformations of the jaws mainly include overdevelopment and underdevelopment. It can occur alone or simultaneously in the upper and lower jaws, and can be symmetrical or asymmetrical, and orthognathic surgery is the most ideal and effective way to treat this malformation. The most common orthognathic deformities are: mandibular protrusion (commonly known as geodontia), maxillary protrusion (also known as bruxism), small jaw (also known as bird’s mouth deformity), maxillary recession (also known as disc-shaped face), facial asymmetrical deformity (also known as crooked face), jaw angle and bite hypertrophy (also known as square face), and high or low cheekbones. In addition, post-cleft lip and palate repair and maxillofacial trauma secondary to dental and maxillofacial deformities are also the targets of orthognathic surgery. Orthognathic surgical treatment of dentofacial deformity Because the surgical treatment of patients with dentofacial deformity needs to cut and move the dental C-bone complex according to the deformity and treatment requirements, to reconstruct the normal three-dimensional spatial relationship and function of the dentofacial structure and to obtain satisfactory cosmetic results of the jaw. Therefore, the treatment plan, the adjustment of the tooth-tooth relationship, the site of osteotomy, the direction and distance of the bone block movement and the selection of the surgical plan should be precisely considered and designed before the operation, and the treatment effect of the selected plan should be expected and the preoperative shape predicted. After determining the treatment plan for orthognathic orthognathic surgery, the treatment procedure must be strictly followed in order to obtain the best expected results and avoid possible errors. According to practical experience, the treatment procedures can be summarized as follows: 1. Preoperative orthodontic treatment After the surgical plan is determined, orthodontic treatment must be carried out first according to the planned orthognathic position, with the aim of correcting misaligned teeth, adjusting the uncoordinated arch and tooth-tooth relationship, eliminating tooth-tooth interference, aligning teeth, and eliminating compensatory tilt of teeth, so that the incised bone segment can be moved smoothly to the designed orthodontic position during surgery, and establishing The result is a good dental relationship. This is a very important step and factor to obtain the best functional and morphological results. 2, determine the surgical plan After the end of the pre-surgical orthodontic treatment, it is still necessary to make a final assessment and forecast of the original surgical plan, and make necessary adjustments to the surgical plan or make necessary additions to the orthodontic treatment, so that the upcoming surgery can meet the reality and achieve the best results. 3.Model surgery, completion of preoperative preparation In addition to the routine general examination, general anesthesia and blood transfusion preparation, the model should be cut and pieced together according to the results of clinical examination, X-ray cephalometric analysis, and facial prediction, and the positioning dental plate and labial arch should be prepared on the completed model of model surgery, as a guide plate during surgery and as a fixed device after surgery, and according to the surgical plan, predicted effect and possible problems, the patient should be given The patient should be fully explained to the patient according to the surgical plan, predicted results and possible problems, and full understanding and consent of the patient should be obtained. 4.Orthognathic surgery must be performed strictly in accordance with the predicted and preoperative surgical design, and should not be altered at will during surgery. 5.Post-operative orthodontic and rehabilitation treatment Even for successful surgical procedures, there are usually problems such as uncoordinated cusp-fossa relationship between upper and lower teeth and unbalanced occlusion after surgery, so post-operative orthodontic treatment is usually needed to improve the occlusal relationship from functional and cosmetic effects and to stabilize and consolidate the effect after surgical correction. If the situation is normal, postoperative orthodontic treatment can be carried out 1-3 months after orthognathic surgery, while rehabilitation treatment is carried out for the purpose of restoring the function of the perimandibular muscles and temporomandibular joint. 6.Follow-up observation Understand the possible changes in the jaw and tooth-tooth relationship after surgery and carry out postoperative effect evaluation. Mobile, corrected bone blocks usually show slight displacement during the healing process. As long as it does not affect the clinical effect, postoperative orthodontic treatment will be carried out to consolidate the effect. However, if there is an obvious tendency of recurrence, it is necessary to treat accordingly. According to the healing process of osteotomy and its biomechanical characteristics, postoperative follow-up observation should be continued for at least 6 months.