Maxillary cysts are clinically divided into two categories: odontogenic and non-odontogenic, among which odontogenic cysts are more common. Small cysts can be left alone in the jawbone, while large cysts can invade the maxillary sinus cavity and are prone to infection, leading to maxillofacial deformity. 12 cases of maxillary cysts invading the maxillary sinus were admitted to our department from 1998 to 2006, and our experience of diagnosis and treatment is reported as follows. Clinical data 1. General data The 12 cases in this group were 8 male and 4 female; the oldest was 68 years old, the youngest was 15 years old, and the average was 40.5 years old. The maxillary tooth-containing cyst invaded the maxillary sinus in 4 cases, and the maxillary tooth-containing cyst was removed and the maxillary sinus was rhizotomized at the same time in 4 cases; the maxillary apical cyst invaded the maxillary sinus in 8 cases, and the maxillary apical cyst was removed and the maxillary sinus was rhizotomized at the same time in 8 cases. The diagnosis was confirmed by histopathological examination. 2, clinical diagnosis According to the history of the affected side of the nose, nasolabial area, lip-buccal groove area, buccal soft tissue apparently progressive bulge expansion. On palpation, the enlarged maxillary bone is ping-pong-like; there are congenitally missing teeth or residual roots in the intra-oral teeth; X-ray or CT examination shows an oval or inverted pear-shaped hypodensity area in the maxilla (maxillary tooth-containing cyst), in which a high-density shadow resembling teeth is visible, and the wall of the cyst spreads to the alveolar bone and even to the roots of the teeth (the cyst form is mostly oval or inverted pear-shaped; in severe cases, there is extensive destruction of maxillary bone, especially the anterior wall of the maxilla. The diagnosis of maxillary tooth-containing cysts or maxillary apical cysts is not difficult. Maxillary cysts, especially those invading the maxillary sinus, are in principle treated surgically. Preoperative root canal treatment is required based on imaging data. Surgical method General anesthesia, K-Lu pathway, paying attention to the incision should be chosen to make the incision at the normal bone to facilitate wound healing and prevent the formation of oral maxillary sinus fistula. In principle, the cyst is removed by bluntly separating the cyst along the wall of the cyst from the bone. If inflammation is found in the maxillary sinus on preoperative radiography, maxillary sinus radical surgery can be performed at the same time; if the tooth is in good condition, the affected tooth can be preserved after apicoectomy. If the tooth containing cyst is removed together with the cyst wall; if there is also an oral maxillary sinus fistula, the granulation tissue around the fistula should be removed and the fistula should be repaired by using the adjacent tissue flap or buccal fat pad flap. Treatment of the operative cavity: the operative cavity is filled with iodoform gauze and drained from the window of the inferior nasal tract, via the anterior nostril. For maxillofacial deformities caused by jaw cysts, the normal facial appearance should be restored after surgery by shaping as much as possible using manipulation. The incision should be tightly sutured to prevent poor wound healing and even cracking to form oral maxillary sinus fistula. Postoperatively, systemic hemostasis and anti-infection treatment was used, and iodoform gauze or balloon was extracted from the nasal cavity in stages from 5 days after surgery, and the sutures were removed in 6 to 7 days. The sutures were removed in 1 week and the wounds were healed and discharged. After 1 to 5 years of postoperative follow-up, none of the cases had recurrence, and the face was symmetrical with basically normal morphology. Discussion Cystic lesions of the maxilla can be of two major types: those of odontogenic origin, such as tooth-containing cysts and root cysts, and those of non-odontogenic origin, among which are facial cleft cysts and neoplastic lesions, such as cystic enameloblastoma, giant cell tumor of bone, and aneurysmal bone cysts. Brown tumors due to hyperparathyroidism can also cause cystic lesions in the maxilla. Tooth-containing cysts are the more common odontogenic cysts that originate from the epithelial cells of the enamel apparatus and are associated with infection and traumatic stimulation, and are more common in adolescents, mostly (75%) in the maxilla, especially in the third molar. According to the relationship between the cyst and the tooth, it can be divided into central and lateral parietal types. In the former case, the cyst surrounds the crown of the tooth, and when the cyst increases, it can be pushed to the distal part of the socket or the tooth can enter the cyst; in the latter case, the cyst is located in the lateral line of the crown and pushes the tooth to the lateral displacement. Routine axial CT scan on the basis of X-ray plain film can better show the structure and composition of the lesion itself, the growth of the craniofacial bone in the lesion area forward or backward, such as the forehead, posterior occipital, zygomatic bone, maxillary sinus and post-sinus soft tissues, inner and outer pterygoid plates; coronal CT scan clearly shows the involvement of the pterygoid bone, pterygoid sinus, pterygoid winglets, optic nerve foramen, septal sinus, sieve plate, inferior and superior orbital fissure, nasal cavity, alveolar process, hard palate and oral cavity The degree of narrowing and deformity. Maxillary cysts are more frequent in the anterior than in the bicuspid and molar areas, while mandibular cysts are more frequent in the molar than in the anterior and bicuspid areas, showing round or ovoid hypodense areas, single or multiple rooms, containing cystic fluid, with a CT value of about 20-25 HU, and as the cystic fluid accumulates the cavity increases, it can be accompanied by the presence of a small amount of gas, which can be lobulated due to inconsistent resistance in all directions, and the walls of the surrounding bone resorption forming the bone cavity are cortical, showing The wall of the surrounding bone cavity is cortical, with clear edges and a dense white line wrapped around. Root-end cysts are mostly located at the root end of deeply decayed, residual or dead pulp teeth, where the root of the adjacent tooth is pushed into position and the root end of the cystic lesion protrudes into the cyst. Tooth-containing cysts occur in the body of the mandible, especially at the third molar. They appear as round or ovoid unicompartmental cyst-like hypodense areas with smooth margins and one or several unerupted teeth with tilted or dislodged apical bone resorption. Keratocysts are prone to secondary infection, with indistinct margins due to cortical resorption and dense bone thickening from chronic infection. The nasopalatine cyst ball is located in the anterior palate at the fusion of the middle nasal eminence and the maxillary eminence on both sides, and the ball maxillary cyst is often located between the lateral incisors and the roots of the single cusp teeth, showing a pear-shaped hypodense area and pushing the roots apart. Isolated maxillary cysts are conical, ovoid or irregular shaped air-containing cavities of varying size and shape, with clear or poorly defined borders, lacking clear sclerotic margins, and typical interdental fan-shaped separation changes seen in adjacent teeth. CT features of maxillary tooth-containing cyst: cystic swelling at the maxillary alveolus; 1 tooth inside the cyst; bone resorption in the upper alveolus. Differential diagnosis: facial cleft cyst: a cyst formed by the remnant epithelium at the union between the various protrusions that make up the maxilla during the embryonic period; the cyst contains cholesterol and can occur in the hard palate, paranasal and maxillary areas, independent of the teeth, surrounded by a sclerotic zone; the larger cysts can be close to the root of the tooth or cause the tooth to shift, but there is no widening of the gap around the root. Single-compartment enamel-forming cell tumor: the cyst wall is often incised and the tooth root is often resorbed or destroyed. Root cysts: the most common odontogenic cysts, caused by chronic infection of the tooth root, are located at the root of the tooth, the tooth is usually not displaced, and there is often a sclerotic zone of bone at the periphery. The incidence of maxillary cysts is higher than that of other bones in the body because there are many epithelial remnants of tooth development in the jaws, which can become the starting base of cysts under certain conditions, and maxillary epithelial cysts are a group of common and slowly increasing benign lesions in the oral and maxillofacial region. The enlargement of cysts is usually considered to depend on three factors: mural enlargement, hydrostatic enlargement and bone resorption factor enlargement. Therefore, treatment of maxillary cysts can be achieved by eliminating or destroying the factors involved in cyst enlargement. Although there are isolated reports of non-surgical treatment of jaw cysts in the literature, the main treatment of cysts is currently surgical, using a combination of cyst excision or scraping, pouching or decompression, and jaw resection. Currently, a combination of the first two procedures is mostly used to remove the three factors of cyst formation in order to achieve radical cure of the cyst. Precautions in jaw cyst surgery: (1) When making an incision, care should be taken to choose to make the incision at normal bone to facilitate wound healing and prevent the formation of oral maxillary sinus fistula. (2) The cyst enlarges and occupies the whole maxillary sinus cavity and invades the surrounding area continuously, causing extensive destruction of the maxilla and massive resorption of the surrounding bone, so special care should be taken during the surgical peeling of the cyst wall to avoid puncturing the cyst wall as much as possible and to strive for complete removal. For this reason, intraoperative attention should be paid to: ① Take care not to cut through the cyst wall when making the incision. ②In order to reduce the tension to reduce the chance of peeling the cyst wall, some of the cystic fluid can be aspirated with a syringe before peeling the cyst. (3) Blunt separation should be made between the cyst wall and bone for complete removal of the cyst. After the cyst is removed, it should be carefully checked for residual tissue of the cyst wall, especially in the apical part, the adhesion of the cyst wall to the bone wall, etc. The residual tissue must be thoroughly removed and the bone cavity can be cauterized with carbolic acid if necessary to prevent recurrence. (3) The operator should be familiar with and master the anatomical structures, especially the adjoining relationships, and be especially careful when stripping the posterior and lateral walls, and never go beyond the posterior wall to avoid damaging important structures in the infratemporal recess, such as the internal maxillary artery and the pterygoid plexus, which may lead to serious bleeding. (4) In case of palatal bone destruction defect, it is necessary to prevent the palatal mucosa from penetrating and even causing oral maxillary sinus fistula. (5) When the cyst penetrates the upper wall of the maxillary sinus, it is necessary to prevent penetration of the orbital floor and pay attention to protect the orbital tissues to avoid serious consequences. (6) If there is also an oral maxillary sinus fistula, the granulation tissue around the fistula needs to be removed, and if there is a large tissue defect, the fistula can be repaired using adjacent tissue flaps or buccal fat pad flaps. (7) If there is also maxillary sinusitis, maxillary sinus radical surgery must be performed at the same time. In this group of 12 cases, 8 of them had maxillary apical cysts with a variable number of roots exposed in the cavity, and any teeth that could be preserved were preserved as much as possible, but apicoectomy must be done intraoperatively, with bone chisel removal of 2-3 mm, and preoperative root canal treatment was required. Teeth that cannot be preserved must be extracted. If the intraoral incision is large after tooth extraction and cannot be tightly sutured, part of the alveolar bone can be removed and then mattress plus interrupted suture can be done. Treatment of bone cavity after jaw bone cyst surgery: opinions differ on the use of filling or no filling. In our case, the bone cavity was not filled with a filling, and the cystic cavity was allowed to fill with a blood clot, with no postoperative infection or fistula formation. We believe that the bone cavity does not have to be filled because new bone can be formed by mechanization as long as the clot in the bone cavity is not infected.