The Mechanical Simulation Of Post-and-core Crown Of Mandibular First Molars Based On Finite Element Analysis

Objective:1.This study aims to construct a three-dimensional finite element model of the post-and-core crown of mandibular first molar post crown was by using reverse engineering technology.2.Then to analyze the influence of the elastic modulus of the post-and-core material on stress distribution of the dentin after the restoration with different post-and-core.3.And then to compare the stress of same post and core restoration under static and dynamic loading.4.And finally to study the influence of different temperature loading on the dentin stress of post-and-core restorations by simulating the temperature variation situation actual environment of the oral cavity in the process of masticationMaterials and Method:The three-dimensional finite element method was used to construct the mandibular first molar fiber-core-resin and cobalt-chromium alloy core and restored with ceramic full crown models.And then loaded with different loading situation,vertical and oblique loading of 225 N in static and dynamic half-sine pulses respectively.The Von Mises stress and the maximum principal stress and distribution of dentin were analyzed to compare the influence of different materials and loading on the stress and distribution of the restoration,which range from 60°C to 0°C with the basic line in 37°C,was added to all of above situation to analyze the influence of temperature alone and together with that on the stress and distribution of restoration.Result:1.On vertical loading:Static loading groups: The peak Von Mises stress and main stress located in the mesial apical and toot bifurcation with volume of 18.752 MPa and 5.7392 MPa receptively in the group of fiber-post-core restoration.While in the cobalt-chromium alloy group the peak Von Mises stress and main stress was 19.128 MPa and 7.0476 MPa but located in the same region.Dynamic loading groups: The peak Von Mises stress and main stress located in the mesial apical and toot bifurcation with volume of 20.052 MPa and 6.1409 MPa receptively in the group of fiber-post-core restoration.While in the cobalt-chromium alloy group the peak Von Mises stress and main stress was 20.453 MPa and7.5428 MPa but located in the same region.2.Oblique 45 ° loading Static loading groups: The residual dentin of the fiber post group was 16.264 MPa with a peak stress of 10.264 MPa,which appeared in the root and neck region.The peak value of Von Mises stress in the cobalt-chromium alloy group was 15.348 MPa,which occurred in the root tip of the mesial root.The peak stress of the main stress was 9.412 MPa,which occurred in the root and neck.Dynamic loading groups: The Von Mises stress peak value of dentin in the fiber pile group was 17.396 MPa,which appeared in the tooth neck;the peak stress was 11.194 MPa in the root tip area;the peak value of Von Mises stress in the cobalt-chromium alloy group was 16.406 MPa,which appeared in the root In the neck,the main stress peak was 10.071 MPa,which was located in the root and neck.3.With temperature loading alone:37-0 °C: The Von Mises stress peak value of the dentin in the fiber pile group is 32.015 MPa,and the peak value of the principal stress is 22.08 MPa.The peak value of the Von Mises stress in the cobalt-chromium alloy group is 41.919 MPa,and the peak value of the principal stress is 16.625 MPa.37-60°C: The Von Mises stress peak value of dentin in the fiber pile group is 55.299 MPa,and the peak stress is 47.751 MPa.The peak value of Von Mises stress in the cobalt-chromium alloy group is 72.405 MPa,and the peak value of principal stress is 61.773 MPa.4.When the temperature and static forces are loaded together:37-0 °C: The Von Mises stress peak value of dentin in the fiber pile group was 30.936 MPa,and the peak value of the principal stress was 19.613 MPa.The Von Mises stress peak value of the cobalt-chromium alloy group was 41.715 MPa,and the peak value of the principal stress was 16.419 MPa.37-60°C: The Von Mises stress peak value of the fiber pile group was 56.568 MPa,the peak stress was 48.541 MPa,the peak value of Von Mises stress in the cobalt-chromium alloy group was 72.654 MPa,and the peak value of the principal stress was 61.543 MPa.Conclusion:1.According to our study,the relatively smaller elastic modulus materials,like fiber-post core crown,are recommended in residual root restoration.2.And instead of dynamic loading the static loading can be used to animate the real situation in oral mechanical analysis.3.And the temperature Loading alone can also cause the changing of stress and distribution in dentin.4.Compared with the temperature dropping,temperature rising may increase the probability of prosthesis fracture.Alloy post has the more sensitivity compare with fiber-post core crown.