Purpose: Maxillary sinus augmentation via crestal approach has been advocated as an alternative approach for sinus membrane elevation. Presently, no study has examined the relationship between the amount of bone grafting material placed and the final sinus membrane elevation height. Therefore, the present study was aimed at investigating the extent of sinus membrane elevation height depending on the amount of bone grafting material inserted as well as three-dimensionally assessing the likelihood of membrane perforation during membrane elevation. Materials and Methods: A total of 34 subjects (16 females and 18 males) with 61 crestal sinus elevation sites were recruited. The following changes in elevated sinus membrane area were recorded: vertical elevation height (VEH), buccopalatal elevation (BPE), and mesiodistal elevation (MDE). Cone beam computed tomography (CBCT) was used to measure the elevated height of the maxillary sinus floor at the initial examination, during surgery, and immediately after surgery. In addition, the VEH:BPE and VEH:MDE ratios at each site were calculated using CBCT to determine the probability of sinus membrane perforation. Results: In average, 0.1 mL of bone graft material placed elevated VEH an average of 3.5 mm, while 0.2 mL and 0.3 mL of graft placed elevated VEH 5 mm and 6 mm, respectively. Furthermore, it was demonstrated that the VEH:BPE and VEH:MDE ratios play a determinant role on membrane integrity. As such, a ratio greater than 1.0 may jeopardize membrane integrity, while a ratio ≤ 0.8 might represent a lower risk of membrane perforation. Conclusion: An initial 0.1 mL of bone material filling can elevate sinus membrane vertically by 3.5 mm. To avoid sinus membrane perforation, a VEH:BPE or VEH:MDE ratio of ≤ 0.8 should be obtained. Schlagwörter: bone replacement graft, cone-beam computed tomography, crestal approach, endosseous implants, sinus augmentation