Implant Diameters Affect the Stress Distribution on Single Molar Restoration

Objectives: Narrow-diameter morse taper (MT) implants have been used to avoid bone grafting for implant insertion in resorbed ridges. However, its influence on the biomechanical behavior of peripheral bone tissue and prosthetic components is not clear. This study compared the biomechanical behavior of three different diameter MT implants on stress in the peri-implant bone tissue and prosthetic components.
Methods: Computer-aided design software was used to create three finite element (FE) models of an atrophic posterior maxilla segment with a single MT implant in the first molar region. FE analysis was used to evaluate the effects of implant diameter (narrow-3.5, regular-4.3 and wide-5.0mm). Bone tissue was considered orthotropic and all structures were considered perfectly bonded. Each model received a 200N oblique load on the occlusal surface distributed on 5 charging points. The shear stress (τ_max) and strain (ε_max) were calculated for the bone tissue and equivalent Von Mises (σ_vM) for implant and abutment.
Results: Wide implants decreased 63% in shear stress on the cortical bone and 41% on the trabecular bone when compared with narrow implants. The strain in cortical bone was 4,964, 2,841 and 1,979 µɛ for 3.5, 4.3 and 5.0 models, respectively. Narrow implants presented 26% and 40% more σ_vM stress in the implant platform when compared to regular and wide implants, respectively. On the other hand, the abutment σ_vM was not significantly affected.
Conclusions: The implant diameter affects the stress and strain in bone and implant, as the diameter increases the stress and strain decrease. Narrow implant should be used with caution, as it induces higher stresses in bone and implant platform.