Optimal Design And Biomechanical Analysis Of Personalized Porous Artificial Condylar Prosthesis

The temporomandibular joint is located in the mandibular condyle area of the human skull.Severe temporomandibular joint disease could cause huge obstacles to the patient’s mouth opening,chewing and other functions,accompanied by pain,and clinical joint reconstruction is needed to repair.Artificial condylar prosthesis replacement is one of the treatment methods,and has a wide range of clinical applications with good results.However,according to the postoperative statistic data,a small number of patients have failed to joint replacement due to titanium plate fracture or screw loosening,which is related to the type,design and materials of the joint prosthesis.Therefore,an artificial condylar prosthesis with better retention force,less "stress shielding" effect and better long-term stability is very significant for improving the success rate of temporomandibular joint replacement.Aiming to solve the current deficiencies of the temporomandibular joint prosthesis,and reduce the stress level and stress concentration of the temporomandibular joint prosthesis and the screw as well as stress shielding of the mandible,and improve the stability of the joint prosthesis,an optimal design method for the porous artificial condylar prosthesis modeling including the fixed plate and the condyle was proposed in this thesis.Then the biomechanical analysis of the designed joint prosthesis was performed by finite element analysis,and the prosthesis was fabricated by metal 3D printing(SLM)finally.(1)Based on reconstructed three-dimensional model and biomechanical model of a mandible,the fixed plate part of the joint prosthesis was designed by using the topology optimization technique.The stresses within the conventional and optimized plates were compared by the finite element method,and the optimal solution with four screws was obtained.The results showed that the maximum stress of the optimized fixed plate and screw was reduced by 7% to 21% and 9% to 49%.(2)Aiming at the design of the condylar head part,a porous structure design method with inhomogeneous cell density and required porosity was proposed.Based on the bone density distribution characteristics of the condyle,condyle cell model with inhomogeneous density was established.(3)In order to further determine the rod diameter parameter of the condylar unit cell,the cell rod diameter was calculated based on the topology optimization technique and the relative unit density model.Finally,a complete personalized porous artificial condylar prosthesis was built.(4)Based on the mandibular biomechanical model,the biomechanical behaviors of the designed porous joint prosthesis and a solid prosthesis were analyzed and compared under three types of occlusion methods.Results of the finite element analysis showed that the average maximum stress of the porous prosthesis(137 MPa)is 48% lower than that of the solid prosthesis(263 MPa),and screw stress has a small drop.Finally,using SLM metal 3D printing and post-processing technology,a better quality joint prosthesis was fabricated.