Sinus lift is a surgical procedure which aims to increase the amount of bone in the posterior maxilla (upper jaw bone), in the area of the premolar and molar teeth, by lifting the lower sinus membrane and placing a bone graft. 

 
When a tooth is lost the alveolar process begins to remodel. The vacant tooth socket collapses as it heals leaving the toothless area. This collapse causes a loss in both height and width of the surrounding bone. In addition, when a maxillary molar or premolar is lost, the floor of the maxillary sinus expands, which further diminishes the thickness of the underlying bone. Overall, this leads to a loss in volume of bone that is available for implantation of dental implants, which rely on bone integration, to replace missing teeth. The goal of the sinus lift is to graft extra bone into the maxillary sinus, so more bone is available to support a dental implant.