Three-dimensional Finite Element Analysis Of The Mandibular Fixed Partial Denture In Various Loading And Edentulous Span

Fixed partial denture (FPD) is one of the major methods to restore the missing teeth. As a important investigation on the features of FPD, many researches was focused on the stress distribution of FPD by means of various techniques or methods and there were many disputes on the results. Combining spiral CT(SCT) scanning technology ,digital image transfer and transcription, with three-dimensional finite element method (3-D FEM), a satisfactory 3-D FE model of the mandibular FPD with biomechanical property was constructed to simulate and analyze the load condition of the mandibular FPD under different kinds of the periodontal support, various position or directions and the changing length of the pontic with different simulated force in order to investigate the mechanism of the FPD.Our study can be divided into three parts:1. Construction of the three-dimensional finite element model of mandibular FPD:The purpose of this part was to construct 3-D FE model of the mandibular FPD by means of SCT scanning technology, digital image transfer and transcription ,UG and MARC engineering design program in order to provide the 3-D FE model basis for the researches of FPD biomechanics. The constructed model has a good similarity to the morphology of the three-dimensional images. The total number of the nodes is 5697 and the number of the elements is 4740 and the model is made of 7 kinds of materials.The model can be rotated arbitrarily and can be zoomed in or zoomed out. It can also be viewed in different fashions. The areas and the volumes by which the model was constituted can be picked out from the whole model and viewed separately. By applying different material properties, boundary conditions and load cases to the model, the different load conditions of FPD can be simulated.2. A three-dimensional finite element analysis of the stress distribution in the mandibular FPD produced by forces applied in varying directions and in low periodontal support:The purpose of this study -was to investigate the stress distribution by changing the load condition under the forces applied in varying directions and in low periodontal support in the mandibular FPD. On the basis of the three-dimensional FE model of the first part, we observed the load conditions of the mandibular FPD using the same force in varying directions and positions. Stress analysis was executed on a personal computer system with a finite element program MARC. The maximum principal stresses, the minimum principal stress and equivalent Von Mises stress in the abutment roots, pontic, alveolar bone and periodontal support were investigated. The results indicated that: The compress in the periodontal support and alveolar bone was concentrated in the tip of the abutment roots when FPD was loaded vertically. There were few changes of stress distribution in different load conditions of FPD. The stress in premolar was larger than that of molar when the restoration was loaded contemporary. Otherwise, the direction of the load influenced the stress distribution on the periodontal support interface and the lateral occlusion force is harmful to the abutment and structure of FPD. When the height of periodontal support was reduced the distribution trends ofthe stresses were similar in the FPD and periodontal support of abutments but the stress value was increased in those regions than the normal one.3. A three-dimensional finite element analysis of the stress distribution in the mandibular FPD produced by forces at different length of the pontic:The purpose of this study was to investigate the stress distribution by changing the length of the pontic. On the basis of the three-dimensional FE model of the first part and using MARC program, we analyzed the stress distribution of the mandibular FPD using the same force at different pontic length in two times, three times and four times comparing with the normal length. The results indicated that the region of the maximum Von Mises stress is on the surface of the connecter of the FPD...