When maxillary molars (that is, maxillary posterior teeth) are implanted, the distance between maxillary sinus and alveolar ridge is very close, especially for patients with molar and premolar loss and extremely atrophic alveolar ridge, the average distance between maxillary sinus floor and alveolar ridge is about 5 mm, and the bone mass is limited, so it is easy to penetrate the sinus cavity when planting long implants, and there is not enough supporting bone, which brings certain difficulties to the implantation operation. Clinically, due to individual differences, some patients have sufficient bone mass and can be implanted with short-sized implants. Generally, maxillary sinus floor bone grafting is used to solve the problem that they can't implant because of insufficient bone mass, but because of the complicated operation, they should be more careful. Cyst is a pathological cavity containing liquid or semi-fluid. Oral and maxillofacial cysts can be divided into soft tissue cysts and jaw cysts according to their locations. Common soft tissue cysts include salivary gland cysts (such as mucous gland cysts and sublingual gland cysts), sebaceous gland cysts, dermoid cysts, epidermoid cysts, thyroglossal duct cysts and branchial cleft cysts. Common jaw cysts include odontogenic jaw cysts (such as apical cysts, primitive cysts, odontogenic cysts and odontogenic keratocysts). ) and facial cleft cysts (such as bulbar maxillary cyst, nasopalatine cyst and median cyst, etc. ), in addition to extravasation cysts and aneurysmal bone cysts. The pathogenesis or tissue sources of various cysts in this area are different. For example, salivary gland cyst is formed by the rupture of salivary gland tube or gland, mucus extravasation or obstruction of salivary gland tube, and the swelling of lumen caused by mucus retention. However, odontogenic jaw cysts are a group of cysts caused by epithelium or epithelial residues of odontogenic organs. It can be inflammatory, such as apical cyst; It can also be developmental, such as odontogenic cysts and primitive cysts.