Purpose: The aim of the present study was to perform a finite element (FE) analysis of a modified sinus elevation procedure involving additional implantation of a cortical bone graft block for stabilization of an implant. A secondary aim was to compare the modified sinus augmentation with the standard technique and to determine whether the FE model to replace a dental implant can be simplified into a cylinder without compromising the accuracy of the outcome. Materials and Methods: Based on computed tomography data, three-dimensional FE models of half of a maxilla were created. A basic model was generated to analyze a conventional sinus elevation procedure and another was created for the modified version, which involved insertion of a cortical bone graft block. Two implant models were used in the premolar region: a typical threaded endosseous dental implant and a simplified 4 × 10-mm cylinder. Occlusal loads were applied in axial, mediotrusive, and laterotrusive directions, and perfect bonding was assumed to be present at all interfaces. Results: The maximum von Mises stresses were significantly lower for the sinus graft models with added cortical bone than for the conventional sinus elevation under all types of loads. No significant difference was observed between the use of threaded implants and the simplified implant cylinders. Conclusion: The addition of a cortical bone graft may be a useful approach to decrease stresses around implants placed into the grafted sinus. Keywords: dental implant loading, finite element analysis, maxillary atrophy, sinus elevation, three-dimensional modeling