The lateral window technique, or external sinus graft, is the creation of an access point to the maxillary sinus through its lateral wall. The access is used to elevate the Schneiderian membrane for the placement of graft material in the inferior part of the sinus space. The lateral window technique is often used when resorption of alveolar bone leads to severely decreased bone height which impairs the placement of dental implants. An external sinus graft is achieved by placing a bone graft in the new space, or window, that has been created. The bone used in the grafting procedure may be autogenous, come from a human donor, or come from donor bovine bone. Though autogenous bone grafts have been shown to heal faster than grafts from the other two sources, their success rates are similar. If implants are needed, they may be placed during the same procedure or after the graft has healed.