Purpose: To evaluate the efficacy, associated morbidity, and results of a three-dimensional reconstruction technique for repairing severe defects of the maxilla using a calvarial autogenous bone graft and a soft tissue double-layered surgical approach in preparation for placing dental implants. Materials and Methods: Bone defects of the maxilla consecutively reconstructed with calvarial autologous graft in the authors' institution were retrospectively evaluated. Patients with combined maxilla alveolar ridge defects with a width less than 4 mm and a height less than 7 mm (to the level of the maxillary sinus or the nostril), with at least three teeth involved, were included in the study. Calvarial bone blocks were sagittally sectioned in fine layers and fixed three-dimensionally in a boxlike structure with particulate bone inside. The purpose was to obtain an adequate amount of vertical and horizontal alveolar bone to enable restoration with dental implants at least 3.4 mm in diameter and 11 mm in length. Results: Eleven reconstructive procedures were performed in 10 patients. Bone graft integration was successful in all of them. No major complications were observed in the donor cranial site. A mean bone gain of 5.04 mm (range, 3.4 to 7.8 mm) in height was obtained (standard deviation [SD], 1.69). The implant surgery was performed between the 15th and 19th weeks. A total of 28 implants were placed, and the mean follow-up time was 45 months (range, 23 to 65 months; SD, 12). The mean graft vertical resorption was 0.78 mm (range, 0.50-1.50 mm; SD, 0.00) 41 months after implant fixation. Conclusion: Three-dimensional reconstruction technique using calvarial bone grafts to restore severe segmental or crestal bone defects in the maxilla is an effective and predictable procedure that can increase the horizontal and vertical bone volume in preparation for the successful placement of dental implants. Schlagwörter: atrophic maxilla, calvarial bone graft, dental implants, onlay bone grafting, preprosthetic surgery, 3D reconstruction