For more than 30 years the maxillary sinus augmentation graft has been a mainstay of implant-directed maxillary reconstruction. The purpose of this article is to review the fundamentals of maxillary sinus reconstruction including anatomy and physiology of the sinus, indications for surgery, preoperative evaluation, surgical techniques, and management of complications. While there are some relative contraindications for the procedure, there are almost no absolute contraindications. With preparation, education, and experience, the maxillary sinus augmentation/elevation graft is a procedure that greatly benefits the patient, with a predictable outcome. Sinus lift procedures are a commonly accepted method of bone augmentation in the lateral maxilla with clinically good results. Nevertheless the role of the Schneiderian membrane in the bone-reformation process is discussed controversially. Aim of this study was to prove the key role of the sinus membrane in bone reformation in vivo.