Biomechanical Behavior of All-on-4 and M-4 Configurations in an Atrophic Maxilla: A 3D Finite Element Method

BACKGROUND: In edentulous patients, the concept of 4 implants with early loading has been widely used in clinical settings. In the case of bone atrophy in the anterior maxilla, using short implants or an angulated implant may be a good choice for treatment. The occlusal scheme remains a key aspect of All-on-4. The aim of this study was to use the 3-dimensional (3D) finite element method (FEM) to evaluate how different All-on-4 designs for canine-guided and group function occlusion affected the distribution of stress in the atrophic premaxilla. MATERIAL/METHODS: A 3D edentulous maxilla model was created and in 3D FEM, 3 different configurations – M4, All-on-4, and short implant – were modeled by changing the anterior implants and using 2 different occlusal schemes. For each model, the occlusal load was applied to simulate lateral movements. For cortical bone, the maximum and minimum principal stress values were generated, and for ductile materials, von Mises stress values were obtained. RESULTS: No significant differences were detected among the models; generally, however, the highest stress values were observed in the M-4 model and the models with short implants. Slightly higher stress values were observed in the group function occlusion group than in the canine-guided occlusion group. CONCLUSIONS: To promote better primary stabilization, M-4 or short implant configurations with canine-guided occlusion appear to be preferable for patients who have severe atrophy in the anterior maxilla.