| Objective: To establish three-dimensional finite element models of maxillary incisor area,Nobel Active implant-supported restoration and fixed prostheses with different assembly designs three-dimensional finite element method was used to analyze the effects of three-unit implant-supported fixed prostheses models with different designs on the stress distribution at the restoration,abutment,central screw,implant and implant-bone interface in three kinds of occlusal relationships,to explain and evaluate the clinical effect of different implant-fixed prostheses designs in different occlusal relationships in maxillary incisor region from the angle of biomechanics,so as to provide a theoretical reference for future clinical work.Methods: Cone-beam CT scan was used to obtain the imaging data of adult volunteer with three units missing in the maxillary incisor area(continuously missing from the right upper central incisor to the left upper incisor).Using the Mimics 19.0software,a three-dimensional solid model of the maxillary incisor was created.The three-dimensional solid model of implant restoration was established by using the software of Unigraphics NX 12.0,four kinds of implant-fixed prostheses models were designed according to different implant positions: Model A: three implants were implanted in three sites;Model B: two implants were implanted in left upper central incisor and left upper incisor;Model C: two implants were implanted in the right upper incisor and the left upper incisor,and Model D: Two implants were implanted in the two central incisor sites.It was assembled in Unigraphics NX 12.0 software and loaded with ABAQUS 6.14 finite element software simulation for end-to-end,normal,and deep overdentures to analyze the stress distribution at the implant-bone interface for each structure inside the implant fixed prostheses under four restoration scenarios with three occlusal loading methods.Results: 1.Three-dimensional finite element models of three-unit implantsupported fixed prostheses in maxillary incisor area,Nobel Active implant-supported restoration and four different designs of mandibular incisor area were established.2.Under the design of A-model implant-fixed prostheses,the stress distribution of each component was more uniform and the stress of the normal combination group was the largest.The stress peaks of the three occlusal relationships were all concentrated in the implant neck,and the stress of cortical bone was much higher than that of cancellous bone.3.The peak stress of each component steadily increased when the occlusal connection changed from a deep overbite to a normal occlusal and end-to-end occlusal relationship.The stress was concentrated on the restoration and implant.4.Under the design of the C-model implant fixed prostheses,the peak stress of all parts in the end-to-end occlusal group was higher than that of the other two groups,and the stress concentrated on the implant neck.5.D model implant fixed bridge design,the prosthesis,central screw,cortical bone,and cancellous bone in the normal group were the most stressed,implant and repair abutment stress peak in the opposite edge group.6.In the end-to-end occlusal group,according to the equivalent stress program of cortical bone and the maximum stress of each component,the stress distribution of implant-fixed prostheses,central screw,implant,and bone tissue showed an increasing trend in Model A,model D,Model C,and Model B.7.In the normal occlusion group,the peak stress of implant-fixed prostheses,abutment,implant,and cortical bone were concentrated in model A,the equivalent stress cloud of cortical bone shows that the stress distribution of cortical bone around the neck of the implant of Model A and model C is more uniform,the Von-Mises stress distribution on the cortical surface of the free-end cantilever,that is,Model B and Model D showed a tendency of bias to the bridge body side.8.In the deep overbite group,the maximum stress distribution in the implant-fixed prostheses,abutment,central screw,implant,and cancellous bone from small to large is the C model,a model,D model and B model,the stress in cortical bone is C model,D model,B model and a model from small to large.Conclusion: 1.All the experimental results showed that the implant neck and the surrounding cortical bone were stress concentration areas and the stress of cortical bone was much greater than cancellous bone.2.In the end-to-end occlusal group,the stress distribution relationship of implant-fixed prostheses restoration,central screw,implant,and bone tissue showed a gradual increasing trend in the A model,D model,C model,and B model,so when the patient’s occlusal state is the end-to-end occlusion,it is recommended to design the A and D models to avoid the design of B and C models.3.In the normal occlusion group and the deep overbite group,it is recommended to design the C model according to the stress distribution of each component of the implant-fixed prostheses in the maxillary incisor area and the force cloud diagram of cortical bone. |
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