Influence of different implant designs on stress distributions in all-on-four concept: A finite element analysis

The study aims to investigate the effect of different implant designs on stress distribution on the implant and mandibular bone in the All-on-four treatment concept using three-dimensional (3D) finite element analysis (FEA). A 3D FEA model was constructed based on the edentulous mandible's mean value. Eight different implant designs, consisting of two main groups with conical and cylindrical body geometry and four subgroups with four different thread designs, v-shaped, square, buttress, and reversible buttress in each group, were experimentally created in a computer environment. Implants 13 and 15 mm in length were inserted between the mental foraminas according to the All-on-Four concept, and the model was completed with an acrylic hybrid prosthesis created in a computer environment. A total force of 300N was applied with an oblique angle of 75° to the occlusal plane on the premolar and 1st molar teeth. Von Mises stresses (VMS) on the implants, and minimum principal stresses (Pmin) on the cortical and trabecular bones were evaluated using the 3D FEA. VMS and Pmin were lower in the cortical bone around conical, square-thread implants. Stress levels were highest on the cortical bone at the implant neck in all groups, with greater stress observed around posteriorly inclined implants. No direct relationship with trabecular bone was identified. Given the study's limitations, the results suggest using conical squared implants in the All-on-Four concept.