Effect of short implant crown-to-implant ratio on stress distribution in anisotropic bone with different osseointegration rates

OBJECTIVE: This study aimed to provide evidence for the clinical application of single short implants by establishing an anisotropic, three-dimensional (3D) finite element mandible model and simulating the effect of crown-to-implant ratio (CIR) on biomechanics around short implants with different osseointegration rates. METHODS: Assuming that the bone is transversely isotropic by finite element method, we created four distinct models of implants for the mandibular first molar. Subsequently, axial and oblique forces were applied to the occlusal surface of these models. Ultimately, the Abaqus 2020 software was employed to compute various mechanical parameters, including the maximum von Mises stress, tensile stress, compressive stress, shear stress, displacement, and strains in the peri-implant bone tissue. RESULTS: Upon establishing consistent osseointegration rates, the distribution of stress exhibited similarities across models with varying CIRs when subjected to vertical loads. However, when exposed to inclined loads, the maximum von Mises stress within the cortical bone escalated as the CIR heightened. Among both loading scenarios, notable escalation in the maximum von Mises stress occurred in the model featuring a CIR of 2.5 and an osseointegration rate of 25%. Conversely, other models displayed comparable strength. Notably, stress and strain values uniformly increased with augmented osseointegration across all models. Furthermore, an increase in osseointegration rate correlated with reduced maximum displacement for both cortical bone and implants. CONCLUSIONS: After fixing osseointegration rates, the stress around shorter implants increased as the CIR increased under inclined loads. Thus, the effect of lateral forces should be considered when selecting shorter implants. Moreover, an implant failure risk was present in cases with a CIR ≥ 2.5 and low osseointegration rates. Additionally, the higher the osseointegration rate, the more readily the implant can achieve robust stability.