Biomechanical Study Of 3D Mesh Titanium Scaffold For The Reconstruction Of Mandibular Segmental Defects

Objective: Recently,a three-dimensional(3D)titanium-mesh scaffold with bone grafting material to form a concrete has been proposed to reconstruct the large defect of mandible.This mixed approach can form a biological restoration by integrating soft tissues and hard tissues of mandible with the scaffold,thus achieve functional reconstruction of mandible.Mechanical stimulation plays an important role in regeneration and reconstruction of bone tissue,so it is necessary to optimize the 3D mesh scaffold to make it has good mechanical adaptability with mandible.The optimized scaffold can bear occlusal load while promoting bone regeneration.However,how to design and optimize the 3D scaffolds of mandible is still unclear.Therefore,the aim of this study was to investigate the optimization of 3D scaffolds for mandibular defect.Methods: Both the biomechanical behavior and mechanobiological property of scaffolds were considered in this study.Four configurations(Rh:regular hexahedron,Co: cuboctahedron,Rd: regular dodecahedron,Di:diamond)and three strut diameters(d1: 0.2mm,d2: 0.5mm,d3: 0.8mm)were divided into 12 groups.Then these scaffolds were filled with bone graft material to simulate bone growth,and different loads were applied.By employing Finite Element Analysis and bone “Mechnostat” theory,the optimal unit cell was selected from 12 scaffolds.In the second part of the experiment,the original implant for mandible defects was designed with the optimal unit cell,and the final implant was optimized to promote osteogenesis and avoid mechanical failure under bi-lateral chewing bite(200N)and maximum force(worse-case)bite(800 N).Results: The mechanical failure of scaffolds highly depended on the configuration and strut size.The same strut diameter: the compression strength of scaffolds: Di<Rd<Rh<Co;With the increasing of strut diameter,the maximum stress of same configurations gradually decreased.The trend of compressive strength of the different scaffolds were consistent with the FEA analysis.Under the masticatory force,Rh-d3,Co-d3 and Rd-d3 can resist mechanical failure,but only Rd-d3 can provide good load transfer for bone tissue.Ultimately,the optimized implant was constructed with regular dodecahedron unit cell,and the strut diameters of scaffold gradually increased from the top of the alveolar ridge to the lower edge of the mandible,from 0.2 mm to 0.8 mm,and the connection between the scaffold and fixed plate was thickened.The computational results indicated that the optimized implant can provide an excellent mechanical environment forbone regeneration and avoid mechanical failure.Conclusion: The 3D mesh titanium implant optimized by FEA and bone “Mechnostat” theory can provide a good biomechanical environment to promote osteogenesis in theory,thus hard and soft tissue of mandible can be combined with implant.It provides the basis for occlusal reconstruction with dental implant and long-term stability.This study provides a theoretical basis for the design and optimization of 3D mesh scaffolds for the reconstruction of mandible defects,and is expected to provide a new strategy for functional mandibular reconstruction.