Fig. 2

For Anatomy-Guided as an evolution of the extra-sinus approach, the relationship of the zygomatic buttress–alveolar crest area is classified into five different types. In this technique, the path of the ZI body can range from total intra-sinus (ZAGA 0) to the wall of the maxilla (ZAGA 1 & 2) to total extra-maxillary sinus (ZAGA 3 & 4). The curvature of the external wall of the maxillary buttress determines the final relationship between the implant and the anterior maxillary wall. For surgical access, a slightly beveled palatal incision starts from the posterior buccal aspect of the maxillary tuberosity to the midline. According to the prosthodontics aspect, the starting point (implant head emergence) should be at or close to the top of the alveolar ridge crest. When the residual bone at the sinus floor level has adequate thickness and width (minimum: 4 mm height, 6 mm width) in a patient without a history of periodontitis, the position of the entry point should be close to the middle portion of the crest with an intra-sinus starting path of the implant if the maxillary wall is flat or convex. When the crestal bone height or thickness is inadequate, the alveolar entrance point should be shifted to the buccal, regardless of the maxillary wall curvature. Based on the maxillary wall concavity and the height of the new bone, the osteotomy is shaped like a tunnel or canal [16, 22]