Study On The Lightweight Design And Manufacturing Of Customized Porous Mandibular Prothesis Based On Selective Laser Melting

Selective Laser Melting(SLM)is one kind of 3D printing process for metal materials,which is efficient and has advantage on manufacturing complex metal parts.Common methods we used to repairing mandibular defect often fail to simultaneously repair the shape,mechanical properties,and motor function of the mandibular defect site.Combining Computer-Aided Design(CAD)with SLM technology can help us to design and manufacture personalized porous mandibular prostheses which can repair the shape,mechanical properties,and motor function of the mandibular defect site at the same time.Nickel-titanium alloy is a medical metal material which has the potential to replace Ti6Al4 V being the next generation of medical implant material,since its elastic modulus is low,biocompatibility is good and has shape memory effect,etc.In this dissertation,nickel-titanium alloy is used as the manufacturing material.And based on the study of the mechanical properties of the nickel-titanium porous structure as well as the mandibular stress distribution under centric occlusion condition,a novel lightweight design method for the design of personalized porous mandibular prosthesis is carried out.The main contents and conclusions of this dissertation are as following:(1)Taking laser power and scanning speed as variables,and using the surface topography and line energy density of the NiTi parts as the manufacturing quality indicators,two-factor comprehensive tests and follow-up experiments were conducted in order to find out the optimal process parameters of SLM manufacturing of the nickel-titanium alloy.By analyzing the microstructure,phase composition and phase change behavior of the SLM NiTi parts,the reliability of the optimized process parameters was verified.After that,the nickel-titanium alloy porous structure was formed under the optimized process parameters,and its compression performance was studied.(2)Personalized three-dimensional mandibular model establishing and finite element simulating.According to the volunteers’ CT scan data,a three-dimensional model of the mandible was extracted and established.And then,optimize this model through a series of reverse modeling operations.After that,the obtained personalized mandibular model was simulated by finite element mechanics,and the normal stress distribution of the mandible model under the condition of centric occlusion was obtained.(3)Lightweight design and SLM molding of personalized porous mandibular prosthesis.Using the compressive strength of the SLM-shaped Ni Ti alloy porous structure obtained in(1)to fit the modified Gibson-Ashby compressive strength model,and established the mathematical relationship between the porosity parameters and the compressive strength of the porous nickel-titanium parts.Using the normal stress distribution rule of the mandible under centric occlusion obtained in(2),calculated the porosity distribution rule of the corresponding SLM porous nickel-titanium parts.Then,taking the mandibular stress region C as an example,the complete design process of the porous internal structure and the personalized external structure of the innovative personalized porous mandibular prosthesis was shown.Finally,the prosthesis designed for stress region C was manufactured by SLM and tried on resin model.