Bimaxillary protrusion is a kind of dental and maxillofacial deformity caused by the overdevelopment of the alveolar bone in the front part of the upper and lower jaws, and it is more common in the yellow and black races. Clinical manifestations of the lips and upper and lower front teeth protruding forward, open lips and teeth, smile and gums, upper and lower lips can not be naturally closed, forcibly closed lips can be seen in the chin and lip area of the tension bulge. Clinically, a considerable number of patients with chin retraction deformity, lateral view of the “bird’s beak” typical face. There are also some patients with maxillary protrusion, compensatory lip tilt of the lower anterior teeth or adaptive hypertrophy of the soft tissues of the lower lip, which gives a visual impression of bimaxillary protrusion. 1, Data and Methods 1.1 Study Objects 102 patients with adult bimaxillary protrusion deformity were admitted to the Orthognathic Surgery Department of Tianjin Stomatological Hospital between October 2005 and August 2013, 48 males and 54 females, with ages ranging from 16 to 41 years old, and an average age of 24.5 years old. The inclusion criteria of the cases were as follows: ① Facial protrusion in lateral view; ② Fullness of the mouth and lips, sharp nasolabial angle, shallow or absent chin-lip groove; ③ Neutral relationship of the first molar; ④ Basically normal development of the dentition and intact dentition; ⑤ No obvious developmental abnormality, no history of chronic systemic diseases, etc. All patients were treated with the aim of improving the facial shape. All patients were mainly aimed at improving the facial shape and reducing the protrusion. The bimaxillary protrusion was categorized into two main types according to the protrusion of the base bone, teeth, alveolar bone, and soft tissues of the lips: true bimaxillary protrusion and pseudo bimaxillary protrusion, which were further categorized into subtypes according to the condition of the chin and soft tissues. True bimaxillary protrusion, also known as osseous protrusion, refers to the protrusion of the basal bones, i.e., the patient’s SNA angle and A-point protrusion distance are larger than normal, the SNB angle and B-point protrusion distance are also larger than normal, and the soft tissue manifests itself as the protrusion of the upper and lower lips. True bimaxillary protrusion was divided into two subtypes, simple bimaxillary protrusion and bimaxillary protrusion with chin retraction, according to the presence or absence of chin retraction. In our data, there were 57 cases of true bimaxillary protrusion, including 24 cases of simple bimaxillary protrusion and 33 cases of bimaxillary protrusion with chin retraction. Pseudomandibular protrusion is mainly dental protrusion, which refers to the normal base bone, i.e., the patient’s SNA angle as well as the A-point protrusion distance is normal, and the SNB angle and the B-point protrusion distance are also normal, but the alveolar protrusion and dentition are protruding, or the upper and lower lips are adapted to be hypertrophied. Clinically, we also found that many patients with bimaxillary protrusion did have maxillary protrusion, but the mandible and dentition developed normally, while the functional adaptation of the soft tissues of the lower lip appeared as a masked protrusion, i.e., soft-tissue-derived protrusion of the lower lip. Soft tissue origin proptosis is therefore included in pseudoproptosis. Pseudoprognathism can also be accompanied by chin retraction. In the data of this group, there were 45 cases of pseudo-bimaxillary protrusion, including 16 cases of bimaxillary protrusion of dental origin and 29 cases of bimaxillary protrusion of soft tissue origin. 1.2 Treatment 1.2.1 Preoperative orthodontics Most patients with bimaxillary protrusion have crowding of maxillary and mandibular anterior teeth and lip tilt, preoperative orthodontics align the maxillary and mandibular dentition, remove the anterior teeth compensation, and adjust the axial inclination of the anterior teeth. 58 of the 102 cases underwent preoperative orthodontics, and 44 cases did not have preoperative orthodontics. 1.2.2 Surgical methods Under controlled low-pressure general anesthesia via nasal endotracheal intubation, most of the maxillary and mandibular first bicuspids were extracted, and anterior maxilIary osteotemy (AMO), anterior mandibular subapical osteotemy (AMSO), and anterior mandibular subapical osteotemy (AMSO) were performed via the labiobuccal approach. osteotemy (AMSO), 3 cases of maxillary median osteotomy and arch expansion during the same period, 6 patients with maxillary Lefort I osteotomy, maxillary and mandibular first bicuspid extraction, AMO, AMSO recession during the same period, and 3 patients who were still protruding after subtractive extraction and orthodontic treatment with maxillary Lefort I osteotomy and recession, and bilateral sagittal splitting osteotomy of the ascending mandibular branch during the same period. Of the 102 patients, 73 underwent horizontal osteotomy chin molding to move the chin anteriorly during the same period (see Table 1). Relying on the jaw plate to accurately locate the distance of movement, the selection of micro titanium plate was fixed in the edge of the pear-shaped hole or zygomatic alveolar bone wall area, respectively, and the mandibular selection of small titanium plate fixation, absorbable thread suture mucoperiosteal incision. 1.2.3 Postoperative orthodontics All patients started postoperative orthodontics about 8 weeks after surgery, aligning the teeth, closing the remaining gap in the cuspid-bicuspid region, as well as small open jaws in the region of the maxillary and mandibular cuspid and bicuspid, to further harmonize the shape of the dental arches, and to establish precise and stable occlusal relationships. 2 .Results The wounds of 102 patients were healed in one stage without infection and bone necrosis. Postoperative follow-up ranged from 12 to 36 months without recurrence. At the end of the treatment, all patients had normal jaw relationship, normal arch shape and curve, neat teeth alignment, good occlusal relationship, good lip-dentition relationship, significant improvement of the lower 1/3 of the facial appearance, and harmonious nose-lip-chin relationship. 3 .Typical case Patient 1, female, 24 years old, came to the hospital to receive orthodontic orthognathic joint treatment with “bimaxillary protrusion, open lip and exposed teeth, and chin retraction”. In the lateral view, the upper and lower lips protruded, nasolabial groove was poor, and the chin was retracted without chin-labial groove. In the frontal view, the upper and lower lips were thicker and the chin was shorter. Positioning Lateral cephalometric film measured SNA angle >86°, SNB angle >84°, anterior point of the chin away from the vertical line made through the root point of the nose towards the FH plane. The diagnosis was bony bimaxillary protrusion with chin retraction. After 6 months of preoperative orthodontics, the first maxillary and mandibular bicuspids were extracted, the AMO was retreated and elevated, the AMSO was retreated, and the horizontal chin osteotomy was shifted forward. Postoperative orthodontic treatment was started 8 weeks after surgery. Before and after surgery as shown in Fig. 1. Patient 2, female, 25 years old, came to the hospital for combined orthodontic and orthopaedic treatment for “bilabial protrusion”. In the lateral view, the upper and lower lips were protruding, the nasolabial angle was slightly acute, the chin was slightly retracted, the chin-labial sulcus was shallow, and the accumulation of chin muscles was obvious when the mouth was closed. In frontal view, the lip-dentition relationship was 4 mm, smile dewlap was 3 mm, bilateral molar class I relationship, deep coverage of anterior teeth, and normal overjet. Positioned lateral cephalometric film measured SNA angle 85°, SNB angle 79°, and the anterior point of the chin was slightly away from the vertical line made through the root point of the nose towards the FH plane. The diagnosis was pseudo bimaxillary protrusion (maxillary protrusion with chin retraction and chin muscle accumulation). Preoperative orthodontics was performed at 6 months to align the teeth, and the surgery was performed with extraction of the first maxillary bicuspid, simultaneous AMO recession, and horizontal chin osteotomy anteriorly. Postoperative orthodontics was started 8 weeks after surgery. Before and after the surgery, as shown in Figure (2) 4. Discussion At present, bimaxillary protrusion is mainly divided into dental protrusion and bony protrusion, dental protrusion refers to the normal base bone, while the teeth and alveolar bone protrude forward; bony bimaxillary protrusion refers to the base bone protrudes forward. In general, dental proclination is an indication for orthodontic correction, while bony proclination is an indication for orthognathic surgery [3]. This classification method mainly considers maxillary and mandibular hard tissues (teeth, alveolar bone, and base bone) in the anterior-posterior direction, and does not address the relationship between chin as well as labial soft tissue malalignment. In this study, combining the morphology of the chin and lip, on the basis of true anterior protrusion and pseudo-bimaxillary protrusion, these two types were further divided into two subtypes, in which the protrusion of soft-tissue origin, although the mandibular hard tissues are normal, the patient’s long-term masked anterior protrusion of the closed lip, the tension of the chin muscle is piled up, and the support of the upper jaw anterior teeth, and the lower lip appears to be thick; or due to the pressure of the upper front teeth of the lower lip downward curls, and the presence of protrusion is larger. For different types of bimaxillary protrusion, better treatment results may be achieved with different treatments. For the treatment of bimaxillary protrusion, at present, many patients turn to orthodontists in order to avoid the risk of surgery, hoping to further improve the relationship between the lips and teeth through the anterior teeth recession, and orthodontic disciplines have also done a lot of work in this area, and achieved certain results [4-6], orthodontic treatment reduces the protruding degree of the upper and lower lips of patients with bimaxillary protrusion by controlled movement of the teeth, and the amount of orthodontic treatment on the teeth is obvious and effective, but the amount of recession on the bone is not. But the amount of recession to the bone is limited. Since patients with bimaxillary protrusion are most concerned about the change of upper and lower lip protrusion after treatment, we compared and analyzed the literature reports in recent years on the treatment of bimaxillary protrusion by simple extraction orthodontic treatment and orthognathic extraction osteotomy and recession treatment, and most of them showed that the improvement of upper and lower lip protrusion by orthodontic treatment was not as ideal as surgical method, but some people thought that surgery did not have much advantage. In addition to the differences in anterior-posterior protrusion, orthodontic treatment is also insufficient for the problem of gingival smile. Although the upper lip is adjusted with the recession of the teeth, the anterior teeth are difficult to be depressed in the vertical direction, and it is difficult to obtain a solution to the gingival situation when smiling. Orthodontic treatment alone also has little effect on the morphology of the chin-lip sulcus, and since most patients have a receding chin, surgical chinoplasty is ultimately required to achieve results. Adult orthodontics also suffers from a long treatment time, typically 1 year to close the extraction gap and about 1 year of retention. Some patients originally hoped to avoid surgery and use extraction orthodontics, anterior protrusion orthodontic effect is not obvious, and further transferred to surgical treatment, but due to the loss of the extraction gap instead of aggravating the complexity of the operation, can only be used in the upper and lower jaw as a whole osteotomy recession. With the intervention of orthognathic surgery, all the above deficiencies can be solved. Regarding the need for preoperative orthodontics and postoperative orthodontics, we believe that preoperative orthodontics is necessary in the following three cases: 1. Crowding, malocclusion, or severe anterior tilt in the maxillary and mandibular anterior region. 2. 2, The maxillary plane is high in the front and low in the back. 3, at the same time combined with other orthodontic need to take into account the solution of malocclusion. However, in reality, many patients have complete teeth, basically straight, occlusal relationship is good, there is no crowding or uneven phenomenon, there is no need for preoperative orthodontics, this group of 102 patients in 58 cases to receive preoperative orthodontics, 44 cases of preoperative orthodontics, but 102 patients all postoperative orthodontics, due to the operation in order to avoid damage to the neighboring teeth, osteotomy end of the two sides of the alveolar bone, so that cusp – bicuspid zone The integrity of the dental arch was destroyed; in order to solve the problem of vertical jaw overgrowth, the anterior portion of the bone segment was uplifted, resulting in small open jaws in the region of the maxillary and mandibular cuspids and bicuspids, and all these required further orthodontic coordination of the dental arch morphology and the establishment of precise and stable occlusal relationships, so postoperative orthodontics is necessary. Studies at home and abroad have also shown that the main difference between the lateral appearance of patients with bimaxillary protrusion and that of the normal population is in the lip and chin area, emphasizing the importance of the positional morphology of the lip and chin area in the overall aesthetic appearance of the lateral appearance. In both true and pseudo-bimaxillary protrusion, the upper and lower lips are protruding, and in most cases, there is also a retracted chin and a shallow or absent chin-lip sulcus. Due to the long-term concealment or adaptive closure of the patient’s mouth, resulting in the accumulation of the chin muscle, when the mouth is closed, the chin muscle is tense, affecting the normal chin-lip movement of the curve of the beauty of the chin. Orthognathic tooth extraction and orthodontic correction of bimaxillary protrusion face shape improvement is mainly concentrated in the nasolabial area, and basically has no effect on the chin, while chin horizontal osteotomy anterior migration can make the chin migration to achieve the ideal chin protrusion, change the tension of the chin muscle, and with the mandibular anterior portion of the apical subtrochanteric osteotomy, the side of the lip-chin relationship can be improved, and at the same time, change the shortness of the lower 1/3 of the face from the front to the back, so that the lower 1/3 of the face to grow vertically, which is the most important difference between orthognathic surgery and orthognathic surgery. This is the outstanding advantage of orthognathic surgery which is different from tooth extraction orthodontics. 72% of the patients in this group of data underwent horizontal chin osteotomy and anterior migration at the same time after maxillary and mandibular anterior osteotomy, which improved the chin protuberance as well as the height of the lower 1/3 of the face. Some scholars at home and abroad also have the same understanding that most patients with bony bimaxillary protrusion should undergo chinoplasty. For bimaxillary protrusion deformity with good molar relationship, most patients choose to use maxillary and mandibular anterior portion of the osteotomy backward, assisted by horizontal chin osteotomy forward migration can achieve good aesthetic and functional results. However, this procedure cannot lift the maxillary dentition substantially, so for patients with long vertical maxillary length and serious gingival exposure, Le Fort I osteotomy should be considered to lift the maxilla as a whole, and maxillary anterior osteotomy and retraction at the same time, in order to achieve satisfactory results. Another type of patients will be encountered in the clinic, that is, in adolescence due to bimaxillary protrusion, the choice of extraction orthodontics, but after the treatment of the upper and lower jaw still exists the problem of protrusion, due to the upper and lower jaw, the first premolar has been extracted, the extraction gap has been closed, the loss of upper and lower jaw anterior portion of the osteotomy of the opportunity, can only choose to maxillary Le Fort I-type osteotomy in the pterygoid maxillary joint area of the bone backward, during the same period of time, the sagittal osteotomy of the ascending branch of the mandibular retrogression, chin Horizontal osteotomy anterior migration, in order to achieve satisfactory results, but increased the complexity of the operation.