| PartⅠ Study of three-dimensional reconstruction and finite element analysis of orbitalPurpose:Accurate reconstruction of the human orbital model based on the computer-assisted method.Realization of the highly simulated three-dimensional visualization of orbital.Analysis of the behavior trend of orbital fracture by simulation the process of traumatic fracture with finite element model.Methods:A New Zealand rabbit skull specimen was constructed to initially explore the accurate reconstruction of fine bone tissue on CT images.We collected the CT scanning data of normal people’s orbital,and used Mimics image processing software to carry out accurate 3D reconstruction,and extracted the interested parts to generate geometric models.The stress of the orbital bone in normal state was analyzed by finite element method.Based on the normal model of orbital bone,the stress state of the orbital bone wall after the frontal and lateral impact of boxing on the orbital bone was simulated in the computer,and the behavioral pattern of orbital fracture was analyzed by extracting data.Results:We were familiar with the method of accurate reconstruction of 3D image through the exploration of New Zealand rabbit skull CT reconstruction,We found that in the normal model of orbit,without considering the thickness,density and support of other surrounding tissues of the orbital bone wall,the biomechanical characteristics of the orbital bone morphology and structure were simply studied,The stress of the medial orbital wall was the highest and the inferior orbital wall was the next.And in the boxing impact,the stress value of the medial orbital wall was the largest,and the inferior orbital wall was the second.The medial wall was the most vulnerable to fracture,assuming the thickness and density of the four orbital walls were the same.Conclusions:The 3D model of orbital bone can be reconstructed accurately by computer-assisted method,which provides technical support for personalized orbital reconstruction.In normal people,orbital bone has a relatively stable mechanical state under static state,and the behavior pattern of fracture of orbital bone under the influence of external forces explains the characteristics of clinical orbital fracture,providing theoretical guidance for better prevention and treatment of orbital fracture.Part Ⅱ Study of personalized design of orbital reconstructive material based on mechanical propertiesPurpose:This part was aiming to carry out the mechanical simulation analysis of orbital implant material model under different experimental conditions,and to provide technical support for solving the problem of personalized customization of orbital implant material in morphological structure and mechanical properties.Methods:The initial 3D reconstruction model of orbital fracture was optimized by computer aided method.Taking the orbital morphological structure of the healthy side as the template and combining with the fracture state of the affected side,the initial model of implant material was optimized and generated.Then,the orbital stress data of the uninjured side was taken as the constraint condition,and two common materials,Medpor and HA,were used to assign parameters to the implant material samples,so as to optimize the structure of the obtained implant material model and determine the optimal size of the implant material.Results:The stress-strain values of fracture orbit were all lower than those of normal orbit.The static stress and strain values of the affected side of orbit after orbital restitution were close to those of the uninjured side.Case 1 patients with simple medial wall fracture required an implant repair area of 269.50mm2,in which the thickness of Medpor material required was 1.13mm and that of HA material was 1.44mm.Case 2 patients with simple inferior wall fracture required an implant repair area of 270.26mm2,in which the thickness of Medpor material required was 1.16mm and that of HA material was 1.37mm.Since the design was based on the definition of damaged edges,the required area of the two materials was the same.When the defect size,shape and target stress were consistent,the HA material required for orbital reconstruction was thicker than Medpor material.Conclusions:The bone of the physical form of the orbital was destroyed and the mechanical balance was lost when orbital fractured,and the orbital was more fragile.An individualized design method was constructed to maintain the shape and size of the orbital reconstructive material,which provided a new design perspective for the development and preparation of more suitable orbital reconstructive material in the future.Part Ⅲ Development and performance studies of Calcium-silicon-based bioactive ceramic material for personalized orbital reconstructionPurpose:We mixed copper with diopside and used 3D printing to obtain bioceramics scaffolds with customizable morphological structure and improved biological activity.Methods:In this study,diopside and bredigite powders were synthesized by sol-gel method,and copper ions were added to diopside in predetermined mole percentage ratio by the same method.The physical and chemical properties of ceramic powders were tested by XRD and ICP.A variety of bioceramics powders were prepared into porous scaffolds using 3D printing technology.The release characteristics of inorganic ions in various bioceramics scaffolds were analyzed by Tris immersion test.The biological activities of bioceramics in each group were detected through cell experiments.Results:In this study,modified diopside bioceramics which can release little copper ions slowly were obtained by adding a small amount of copper ions into diopside,and the bioceramics powders were successfully fabricated into porous scaffolds using 3D printing technology.By testing in vitro degradation,cell activity and cell morphological observation,we found that the diopside scaffolds containing trace copper ions showed an ideal biological activity to promote the proliferation of human umbilical vein endothelial cells,which was comparable to the known bredigite that rapidly degraded and released magnesium and silicon ions to promoted the osteogenic effect and vascularization.Conclusions:In this study,we constructed a new method to fabricate ceramic scaffolds by means of 3D printing,which solved the difficulty in traditional bioceramics shaping.In addition,the addition of trace copper elements to the magnesium-calcium-silica-based bioceramics diopside with reliable mechanical properties and good biological stability is expected to improve the biological activity of the traditional diopside,providing a new idea for the exploration of implant materials with better properties. |
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