The chin consists of the connection of the horizontal branches of the bilateral mandibles and is an important part of the lower 1/3 of the face. Its own morphological position and its harmonious proportional relationship with the upper and middle face is one of the important factors of facial aesthetics, and affects the shape and function of the lips. Poor development of the chin bone can lead to “pointed mouth”, “pointed face” or “bird-shaped face” deformity. Overdevelopment of the chin can cause “long face” or “horse face” deformity. Deviation of the chin can cause asymmetry of the entire face. Chin deformity can exist alone or occur simultaneously with other skeletal deformities of the jaw or face. The cosmetic plastic surgery treatment of chin deformity can be divided into chin filling surgery and chin shaping surgery according to the different surgical methods and surgical sites. 1, chin filling chin filling surgery: the use of autologous bone, artificial bone or other biological substitutes placed in front of the chin bone after shaping to increase the length and protrusion of the chin, to improve the facial contour of the surgical method, mainly applicable to the correction of mild to moderate small chin deformity with normal bite and relationship. (1) Surgical access: chin filling surgery can be used extra-oral access and intra-oral access, extra-oral access is less used at present due to the scar left under the can, this article focuses on intra-oral access chin augmentation. The length of the incision depends on the material to be placed. When silicone prosthesis is used for chin augmentation, the length of the incision is about 1-1.5cm because of the elasticity of silicone, and the depth reaches the surface of the periosteum, and a cavity is formed by sharp stripping with small scissors on the surface of the periosteum, the size of which is suitable for placing the silicone stent, and the cavity should not be too large to prevent the prosthesis from shifting after surgery. When using autologous bone or artificial bone for chin augmentation, a 4-4 “V” shaped incision is made in the mucosa, and the mucoperiosteum is cut to reach the surface of the chin bone, and the periosteal stripper is stripped to reveal the bone surface of the chin bone, so as to facilitate the fixation of the implant. (2) Implant material: ① Silicone implant: solid silicone is the commonly used implant material at present, as long as the indications are chosen correctly, it is still an effective method to correct small chin deformity. According to the preoperative design and the operator’s experience, the shape and size of the silicone prosthesis are carefully sculpted and trimmed. Since the most likely complication after silicone implant placement is post-operative displacement which affects the surgical result, the volume should not be too large when implanted. At the same time, attention should be paid to the symmetry of the front and back, left and right positions of the prosthesis. After adequate hemostasis, the wound cavity is flushed with antibiotic saline and the muscle layer and mucosa are tightly sutured. After surgery, the wound is fixed with an external dressing. Medpor implant placement Medpor (POREX SURGICAL INC, USA): also known as high-density porous polyethylene, is a porous implant material with good biocompatibility and easy to sculpt and shape. After placement, it can be fixed to the bone surface of the chin bone with titanium nails at both ends, and there is no risk of prosthesis displacement after surgery. Because this material has a long arm, it makes the transition between the lower edge of the lower jaw and the chin after placement continuous and natural, with good results. 2, chin shaping: early eighties Bell proposed with a wide range of soft tissue tip chin osteotomy plastic surgery, because the blood flow of the chin bone segment is guaranteed, postoperative bone resorption is greatly reduced, and the proportion of soft tissue changes after the osteotomy is closer, is the ideal method of correction of various chin deformities. It is suitable for the surgical correction of chin recession, short chin, long chin, giant chin and deviated chin. (1) Basic osteotomy method chin osteotomy: design a 4-4 “V” shaped incision in the mucosa of the labial side of the lower lip gingival groove, cut open the mucoperiosteum to reach the surface of the chin bone, peel off the periosteal stripper to reveal the front of the chin bone, the range of peeling is appropriate to meet the designed osteotomy line, try to retain the muscle attachment below the osteotomy line to ensure the blood supply of the osteotomy block; first use a small round drill to set out the midline at the mid-chin union, and then set out the horizontal osteotomy line. The horizontal osteotomy line is located below the bilateral chin holes and parallel to the jaw plane, 1-1.5 cm from the lower edge of the median chin, and is used to cut the bone along the osteotomy line with a compound saw. The bone chisel is inserted between the broken ends of the bone, and the distal bone block is completely freed by rotating and prying, at which time the osteotomy section can be repositioned according to the patient’s deformity and preoperative design to achieve the purpose of correcting the corresponding deformity. (2) Commonly used chin osteotomy displacement mode and indications: ① horizontal forward displacement type: it is the most commonly used osteotomy mode in chin shaping surgery, mainly applicable to patients with simple chin recession and not accompanied by deformity of the chin bone in the left and right and vertical directions. (2) Forward lengthening type: It is suitable for patients with chin recession who also have short chin bone development in the vertical direction, and is a commonly used method to correct small chin deformity in clinical practice. After the chin bone is truncated horizontally, the distal bone segment is lengthened according to the preoperative design, and a small splint is used for strong internal fixation. The broken end of the bone is filled with autologous bone or artificial bone graft to establish bone continuity and ensure bone healing. (3) Horizontal left and right shift: It is suitable for patients with normal chin height, bilateral chin nodes are basically symmetrical and located at the same level of chin deviation. The distance between these two lines is the distance to be moved horizontally. ④Horizontal shift rotation type: If the chin is skewed and the bilateral chin nodes are located at the same level but the anterior and posterior directions are not the same, the anterior and posterior rotation should be done at the same time as the left and right movement of the formable part. If the chin is oblique and the bilateral chin nodes are in the same direction but not at the same level, when moving the chin from side to side, up and down rotation should be done at the same time. ⑤ Shortening forward shift type: It is suitable for patients with a posterior chin reduction but too long in the vertical direction. During surgery, two parallel osteotomy lines are designed in the chin and the distance between the two lines is the height to be shortened. The lower bone segment is cut first, and then the upper bone segment is cut and removed, and the cut segment is moved forward in the predetermined position. Steel wire or small titanium plate is fixed internally. (6) Shortening backward type: It is suitable for those who do not have chin protrusion and have long chin vertically. After removing the bone segment to be shortened, the lower part of the osteotomy is set back and fixed properly. (3) Retrograde osteotomy of the lower edge of the chin body of the mandible: correction of square wide chin deformity from the morphological point of view, the chin is located in the lower 1/3 of the face and is one of the important components of facial aesthetics. Therefore, when performing chin osteotomy, we should not only consider the shape and position of the chin itself, but also take into account the overall proportional relationship between the chin and the mandibular angle and the mandibular body. Especially for patients who require cosmetic reduction of facial bones, it is necessary to take into account both the morphology of the frontal view and the continuous flow of the curve of the mandibular angle, body and chin from the lateral view. In the past, not enough attention was paid to this aspect in both chin shaping surgery and mandibular angle osteotomy. Therefore, on the premise of ensuring good blood supply to the distal bone segment after chin osteotomy, it is necessary to explore a chin osteotomy method that is simpler to osteotomy and takes into account the overall coordination of the mandibular angle, body and chin. Based on our many years of clinical experience, we designed the surgical method of “retrograde osteotomy of the lower edge of the chin body of the mandible to correct square wide chin deformity”, which can well maintain the natural shape of the chin bone because the lower edge of the chin remains unchanged. For patients with a wide, uncoordinated lower face, this surgery can be performed alone or in conjunction with mandibular angle osteotomy and horizontal chin osteotomy. For patients with a combined wide chin, retrograde osteotomy of the lower edge of the chin body of the mandible (including chin node osteotomy) is performed at the same time as the curved osteotomy of the mandibular angle, which can not only make the osteotomy line of the mandibular body continue smoothly and completely avoid the second mandibular angle, but also achieve a more perfect face shape from the front.