There are two types of sinus graft procedures:
 Indirect Sinus floor Elevation with placement of implant
 Direct Sinus Graft using modified caldwell luc technique
The maxillary sinuses are behind your cheeks and on the top of the upper teeth. Sinuses are like empty rooms that have nothing in them. Some of the roots of the natural upper teeth extend up in to the maxillary sinuses. When the upper teeth are removed, there is often just a thin wall of bone separating the maxillary sinus and the mouth. Dental implants need bone to hold them in place. When the sinus wall is thin, it is impossible to place dental implants in this bone.
There is also a solution, its called sinus graft or sinus lift. The specialist or skilled implantologist enters the sinus from where upper teeth used to be. The thin paper like sinus membrane is carefully lifted upward and donor bone is inserted into the floor of sinus. After several months of healing, the bone becomes the part of the patient’s jaw and dental implant can be inserted and stabilized in this new sinus bone.
Furthermore, If enough bone between the upper jaw ridge and the bottom of the sinus is available to stabilize the implant well, sinus augmentations and implant placement can sometimes be performed as a single procedure. If enough bone is not available sinus augmentation will have to be performed first, then the graft will have to mature for several months, depending upon the type of graft material used. Once the graft material has matured, the implant can be placed.