The Foundation Of Three-dimensional Finite Element Model For Fixed Bridge Of Posterior Teeth Restored With Different Post-and-core Materials And Stress Analysis Of Abutments

Objective:To found a three-dimensional finite element model for fixed bridge of posterior teeth restored with different post-and-core materials, and compare the stress distribution of mandibular second molar restored as abutment of fixed bridge under the two loading conditions, and provide experimental basis for clinical applications.Method:A healthy adult male volunteers with a complete dentition, normal occlusion, no significant periodontal disease and alveolar bone loss, no posterior teeth defects and obvious wear was selected. The lower jaw data obtained by CT scanning were inputted into the Mimics software, and setted appropriate threshold values of tissues. According to the different gray-scale of images, two-dimensional contours of crown, root and pulp were delineated, and fitted the date segmented by Mimics software for extracting tissues required and building 3D models. The model was saved as IGES format. The model data of the mandibular second premolar and second molar were read in Ansys software (Ansys Inc. USA), and given the part of entities to the respective material properties. The model was meshed automatically and manually, and divided into different regions of structure and physical properties by the Boolean operation, and setted the material properties, boundary conditions as requested. Three-dimensional finite element model obtained were applied load to study dentin stress extremum and distribution of abutment. Results:The three-dimensional finite element model founded in this study had reasonable mesh and similarity.Mandibular second molar as fixed brige abutment of the dentin stress extremum from the biggest to the smallest were as follows:the glass fiber post> Ceramic post> cast titanium alloy post and core>cast nickel-chromium alloy post and core.High stress region appeared in the inside of cast Ni-Cr alloy post-and-core and dentin near root furcation and tip of post; and in the inside of cast titanium alloy post-and-core and dentin near root furcation and mesial cervical margin; and in mesial cervical margin for glass fiber post-and-core and ceramic post-and-core.Conclusion:Using CT computed tomography combined with reverse engineering software and ANSYS finite element analysis software to establish a three-dimensional finite element model for fixed bridge of posterior teeth restored with different post-and-core materials is accurate, effective and feasible. The model can better simulate the clinical practical situation, calculated results are reliable and comparable.When posterior teeth were restored with post-and-core materials as abutments of fixed bridge, the elastic modulus of material used should be close to dentin.