Purpose: The aim of this clinical study was to evaluate the long-term outcome of the split bone block (SBB) technique for vertical bone augmentation in the posterior maxilla in combination with sinus floor elevation using a tunneling approach. Materials and Methods: Patients were treated for extensive vertical and horizontal alveolar bone defects without simultaneous implant placement and followed up for at least 10 years postoperatively. Autogenous bone blocks were harvested from the mandibular retromolar area following the MicroSaw protocol. The harvested bone blocks were split longitudinally according to the SBB technique. Implants were inserted and exposed after every 3 months, and prosthetic restoration was performed. Results: One hundred forty-two consecutively treated patients, 154 grafted sites, and 356 inserted implants were documented. Minimal graft exposure (1 to 3 mm) 4 to 8 weeks postoperatively was documented in two sites; infection of the grafted area occurred in one other case. The mean preoperative clinical vertical defect was 7.8 ± 3.9 mm, and the mean horizontal width was 3.1 ± 2.2 mm. Postoperatively, the mean vertical gained dimension was 7.6 ± 3.4 mm (maximum: 13 mm), and the mean width was 8.3 ± 1.8 mm. Implants could be inserted in all sites, with additional local small augmentation in 21 cases. The amount of maximum vertical bone resorption was 0.21 ± 0.18 mm after 1 year, 0.26 ± 0.21 mm after 3 years, 0.32 ± 0.19 mm after 5 years, and 0.63 ± 0.32 mm after 10 years. As part of a total patient dropout of 16.9%, four implants were lost within 10 years. The mean vertically gained bone was stable at 6.82 ± 0.28 mm (maximum: 12 mm). The resorption rate after 10 years was 8.3%. Conclusion: The described tunneling flap approach allows a hermetic soft tissue closure, characterized by a reduction of dehiscence and a secure bone graft healing. The combination of thin autogenous bone blocks and bone particles according to the SBB technique allows an acceleration of transplant revascularization, and thus, of graft regeneration, allowing a shortening of the patient treatment time as well as long-term three-dimensional volumetric bone stability. Schlagwörter: 3D bone augmentation, MicroSaw protocol, posterior maxilla, sinus floor elevation, split bone block technique, tunnel technique, vertical alveolar ridge augmentation