A midcrestal incision was made with vertical release incisions at the canine and tuberosity region. A full-thickness mucoperiosteal flap was elevated. The lateral maxillary sinus wall was prepared using a diamond burr with copious irrigation with sterile isotonic saline, regarding the contour of the maxillary sinus as observed on the preoperative panoramic radiograph. A bony top-hinge trap-door was mobilized and turned inward and upward into a horizontal position in the maxillary sinus, together with the carefully elevated Schneiderian membrane. The area created between the lifted lid and the sinus floor was filled only with BCP (Straumann® Bone Ceramic). The BCP was 100% crystalline, highly pure, and had a porosity of 90%. The pores were 100 to 500 μm in diameter. No membrane was used to cover the lateral window [36]. Primary wound closure was performed with Gore-Tex® sutures (W.L. Gore & Associates, Newark, DE, USA). Immediately after the procedure, a panoramic radiograph was made. Postoperative examination and removal of the sutures were performed 10 to 14 days after the MSFE procedure.

After 9-month (five patients) and 12-month (five patients) healing times, a crestal incision was made with small mesial and distal buccal vertical release incisions. Subsequently, a full-thickness mucoperiostal flap was raised. The alveolar ridge was inspected for suitable implant placement, and the former lateral window area was inspected for tissue condition. Implant preparations were made, and biopsies were obtained from the grafted area at planned dental implant positions using trephine drills with an external diameter of 3.5 mm and internal diameter of 2.5 mm (Straumann^® trephine drill) with copious irrigation of sterile saline. In the 10 patients, 22 standard plus, regular neck, soft tissue level Straumann® SLA dental implants with a diameter of 4.1 mm and a length of 10 or 12 mm were placed (Fig. 1). The implants were left to integrate in a non-submerged unloaded fashion. Soft tissue closure was performed with Gore-Tex® sutures. A postoperative radiological examination (panoramic radiograph) was taken directly after dental implantation. Sutures were removed after 10 to 14 days and, if needed, provisional prosthetics were adapted to the new situation. Attention was paid to prevent premature loading of the dental implants. The patients were instructed to avoid loading of the posterior maxilla upon which the operation had been conducted until the 3-month integration time of the dental implants had passed and the fixed superstructures were fabricated and placed.