Biomechanical and Mechanostat analysis of a titanium layered porous implant for mandibular reconstruction: The effect of the topology optimization design.

A porous scaffold/implant is considered a potential method to repair bone defects, but its mechanical stability and biomechanics during the repair process are not yet clear. A mandibular titanium implant was proposed and designed with layered porous structures similar to that of the bone tissue, both in structure and mechanical properties. Topology was used to optimize the design of the porous implant and fixed structure. The finite element analysis was combined with bone "Mechanostat" theory to evaluate the stress and osteogenic property of the layered porous implant with 3 different fixation layouts (Model I with 4 screws, Model II with 5 screws and Model III with 6 screws) for mandibular reconstruction. The results showed that Model III could effectively reduce the stress shielding effect, stress within the optimized implant, defective mandible, and screws were respectively dropped 48.18%, 44.23%, and 57.27% compared to Model I, and the porous implant had a significant stress transmission effect and maintained the same stress distribution as the intact mandible after the mandibular defect was repaired. The porous implant also showed a significant mechanical stimulation effect on the growth and healing of the bone tissue according to the bone "Mechanostat" theory. The combination of porous structure with the topology technique is a promising option to improve the mechanical stability and osteogenesis of the implant, and could provide a new solution for mandibular reconstruction.