The long-term success of oral implant treatment depends to a large extent on the quality and quantity of the implanted bone bed. The lack of bone volume in this area after maxillary posterior tooth loss often limits dental implantation for various reasons, and maxillary sinus floor elevation increases the bone height in the maxillary posterior area, creating conditions for implantation. The earliest designs and descriptions of maxillary sinus lift bone grafting are not exactly the same as today’s. Since 1987, as new techniques, instruments and materials have emerged, more scholars have developed improved methods, such as the osteotome technique proposed by Summers, which tends to make the maxillary sinus floor lift minimally invasive. In particular, the use of ultrasonic bone gouge has greatly improved the success rate of maxillary sinus floor lift with fewer complications. The clinical bone height in the maxillary posterior region is often divided into four cases: 1, the available height is 8-12mm, no maxillary sinus floor lift, routine implant placement, 2, the available bone height is 6-8mm, the bone quality is good, the maxillary sinus floor is not irregular, the bone chisel technique can be used to mildly elevate the sinus floor, the same time implant placement, 3, the available height is 4-6mm, the maxillary sinus floor lift, if the remaining If the remaining alveolar bone density is still good, implants can be placed at the same time. If the available bone height is less than 4mm, the maxillary sinus floor lift will be performed 6 months after the implant surgery. The author’s clinical cases are summarized as follows; I. Choose maxillary sinus floor apex surgery or maxillary sinus lateral wall window lift? When the available bone height in the posterior part of the maxilla is 6-8mm, the bone quality is good and there is no irregularity in the maxillary sinus floor, the bone chisel technique can be used to mildly elevate the sinus floor by 2-3mm, and the implant with a length of 10mm can be chosen to be placed at the same time, clinically it is usually possible to encounter some bone heights of 6-8mm, but the maxillary sinus floor is spaced and the internal elevation can easily The mucosa may rupture. If the mucosa is hyperplastic and there is chronic inflammation in the maxillary sinus, it is necessary to evaluate the patient as a whole before surgery and to consider it comprehensively, and not to perform the procedure reluctantly and blindly. If the intermaxillary distance is normal and the patient has a light occlusal force, short implants can also be placed to avoid the sensitivity of the endolift technique itself. Some scholars recommend the use of bone collagen for bone grafting, such as internal maxillary sinus floor lift, because of the large amount of rich collagen content within the bone collagen, which facilitates the formation of new bone. Other scholars suggest that if 2-3 mm of bone height is lifted, any bone grafting method can be dispensed with. The maxillary sinus floor cavity will likewise form new bone. It also reduces the chances of maxillary sinus infection after the procedure. It is recommended that the bone height should not be raised more than 4 mm for an internal maxillary sinus floor lift, otherwise there is a high risk of perforation. If you are not sure about the internal maxillary sinus lift, you can opt for a lateral maxillary sinus lift. The surgery is performed under direct vision and the surgeon can determine the state of the maxillary sinus based on the color and elasticity of the mucosa and decide the height of the lift according to the need, considering that the size and shape of the maxillary sinus varies greatly from the alveolar ridge to the thickness of the bone at the base of the maxillary sinus, which can range from eggshell to a few millimeters, so the technique of maxillary sinus floor lift should be considered comprehensively, including the incision design, the position and size of the opening and whether it is simultaneous. Therefore, the maxillary sinus floor lifting technique should be measured in a comprehensive manner, including the incision design, the position and size of the opening, and whether the implant is placed at the same time. When the maxillary sinus was first invented, the bone window of the maxillary sinus was usually a rectangle with sharp angles, and the sharp angles in this design and the drilling action on the bone tended to tear the maxillary sinus mucosa. Another difficulty is that fractures of the bone window are difficult to avoid, so the design of the maxillary sinus window was constantly modified, and a semi-circular window with a reamed shaft on top was still unsatisfactory. 1993 saw the introduction of a round or oval bone socket without a reamed shaft. Usually, in this design, the bone island is also attached to the underlying mucoperiosteum or maxillary sinus mucosa, which is peeled away from the mucosa and turned upward and inward, and sometimes, the bone island is peeled off and ground into granules as part of the graft material. Therefore, the current mature method is basically to open into an oval shape, and some scholars are used to turn the bone island with mucosa upward and inward, and some other scholars are used to peel off the bone island and grind it into granules as the bone graft material. There are also some scholars who prefer to graft the stripped bone island in situ and cover the surface of the bone window. However, this method must fix the bone island firmly, otherwise the bone island piece will easily cause infection once it moves. Combined with the operator’s experience for single posterior teeth missing customary opening window into a circle. The window should be as small as possible. Avoid opening the window too large, affecting the adjacent teeth. However, if the opening is too small, the field of view is inevitably restricted, and it is necessary to operate under blind vision when stripping the mucosa of the maxillary sinus floor and the palatal side. Therefore, it is crucial to choose the right special stripper to match the operator’s hand feeling that the mucosa of the maxillary sinus floor is not easily ruptured. If there is no 100% certainty in stripping the mucosa of the maxillary sinus floor, the opening can be enlarged and stripped under direct vision. Another advantage of small openings is that the postoperative response is mild. It reduces postoperative edema and pain. For patients with multiple missing posterior teeth, an oval window or a rectangular window can be chosen for maxillary sinus floor lift, and the height of the window can be referred to the height of the alveolar ridge shown by CT to avoid too low or too high window, which is usually 2-3 mm above the alveolar bone. If a bone septum is encountered at the floor of the maxillary sinus, it is best to choose two small windows if it happens to be in the middle of the window to be opened. The septal bone wall serves to accommodate the graft material. If the bone wall on the buccal side is too thick and the opening window is relatively large, which can easily lead to the tearing of the maxillary sinus mucosa, the same window can be opened separately and continued after stripping the mucosa, fully ensuring the integrity of the maxillary sinus mucosa. Especially, the application of ultrasonic bone knife in the elevation of maxillary sinus floor effectively reduces the incidence of mucosal perforation. The ultrasonic osteotome vibrates at ultrasonic frequencies of 60-200 μm horizontally and 20-360 μm vertically, selectively cutting mineralized tissue without cutting soft tissue. Third, the selection and application of bone graft materials in the lateral wall opening of maxillary sinus lift. There are many types of bone graft materials selected for elevation, and some scholars suggest using artificial material nonresorbable porous hydroxyapatite (HA) mixed with demineralized lyophilized dermal medullary autologous bone particles, and autologous bone mixed with artificial material at 1:1. Since all autologous bone and allogeneic bone undergo different degrees of resorption, the addition of non-resorbable HA to the graft bone can compensate for the resorption of bone to some extent. The porous nature of HA facilitates bone growth on the surface, and it also has X-ray blocking properties that facilitate subsequent X-ray examinations. When the available height is 4-6 mm, a maxillary sinus floor lift is performed, and if the remaining alveolar bone density is still good, implant placement can be considered at the same time. If the implant is to be placed at the same time, special attention should be paid to the depth of the pioneer drill and the reaming drill in the preparation of the cavity, so as not to touch the mucosa of the maxillary sinus floor, otherwise it will be easily perforated. The most reliable method is to use a stripper to penetrate deep into the maxillary sinus floor, so that the drill bit can be clearly felt when the pioneer drill or reaming drill penetrates the alveolar bone, thus avoiding perforation of the mucosa of the maxillary sinus due to the drill bit. The implant is placed with partial bone or autogenous bone and is placed as far as possible on the palatal side, then the implant is placed and finally the artificial bone is placed on the buccal side. This way the implant can be placed first to avoid the potential cavity for the implant to be placed. It also avoids the risk of rupture of the maxillary sinus mucosa due to the implantation of the bone graft material first and then the implant. Fourth, about the surgical complications of maxillary sinus floor lift The reaction after maxillary sinus floor lift is heavy. It is advocated to give antibiotics to prevent infection half an hour before surgery, and to apply antibiotics routinely intravenously for 48 hours after surgery, which can be extended to 72 hours to prevent infection if necessary. If there is local pain, oral or intravenous painkillers can be used. If the mucous membrane of maxillary sinus is broken during surgery, nasal drops are needed. Mucosal perforation of maxillary sinus mainly occurs during surgery, due to improper operation or mucosal thinning of maxillary sinus, inflammation of maxillary sinus mucosa and other causes of reduced mucosal elasticity and adhesions leading to perforation. Smoking causes increased brittleness of the maxillary sinus mucosa, which also increases the risk of maxillary sinus mucosal perforation. Smaller mucosal ruptures caused by inadvertent stripping of the maxillary sinus mucosa can be continued with biofilm coverage. If the perforation is large, check for inflammation within the maxillary sinus and recommend stopping the procedure if there is inflammation to avoid postoperative graft infection failure. Post-operative infection of maxillary sinus lift can easily lead to lift failure. Mucosal perforation of the maxillary sinus occurs during surgery increases the chances of infection. Improper selection of surgical indications also contributes to it. Some of the patients who need maxillary sinus floor lift have mucus cysts in the maxillary sinus or chronic maxillary sinus inflammation and mucosal thickening. If the mucous cyst in the maxillary sinus is not removed and the maxillary sinus floor lift is performed, there is an increased risk of infection, and Professor Linno recommends removing the cyst for three months before performing the external maxillary sinus floor lift. The authors recommend that patients who encounter the need for maxillary sinus floor lift must have a perfect examination before surgery, including general condition and local examination, and must take CBCT to rule out maxillary sinus abnormalities and other conditions. Because panoramic films are often not clear in detail it is easy to overlook conditions such as mucus cysts in the maxillary sinus and mucosal abnormalities. Choose the elevation height according to the thickness of the mucous membrane at the floor of the maxillary sinus with the reference of CBCT, the filling is too high to easily cause blockage of the maxillary sinus fissure. This leads to secondary infection. The development of maxillary sinus floor lifting technique has become very mature today, especially with the innovation of new equipment and graft materials, and its long-term results after lifting are good.