Three-dimensional Finite Element Analysis Of Post And Core Crown Restoration Of Various Forms Of Tooth Defects With Mandibular First Molar

Objective:Use Three-dimensional finite element analysis method to establish the model of first mandibular molar tooth and periodontal tissue,to compare the stress distribution and intensity of the residual tooth and periodontal tissues of the first mandibular molar when the two types of post-core materials were used to repair the defects.It provides guidance for the ideal design of the post-core crown restoration,the selection of materials,and the adjustment of the occlusion.Methods:Use CBCT scanning and Mimics10.01 and ANSYS software to establish a three-dimensional finite element model of the first mandibular molar with varying degrees of tooth defects,including crown,dentine,pile,nucleus,periodontal ligament,and alveolar bone.And Analyze the stress condition of the tooth and periodontal tissue under 24 different working states by two types of occlusal ways.The experiment was divided into two parts:In the first part,we use the finite element software to establish a three-dimensional finite element model of the first mandibular molar with different defects restored with post-core crown.The second part,it is divided into six groups according to the degree and location of the tooth defect.The six models of the defects are repaired with two post-core materials which have different elastic modulus.Then carry out the 600 N model at 5 points and 8 points,in order to simulate the ABC/AC occlusal contact pattern,including the 24 operating conditions.At last we compare the stress distribution and indensity of the all-ceramic crowns,residual tooth tissue and post-cores in each group.Results:1.After the post-core crown restoration,the maximum principal stress ofresidual dentine is mainly concentrated in direction of the distal buccal of the mesial root,the root bifurcation below and the distal root,some occur in the distal region of the preparation crown.The maximum principal stress of all-ceramic crowns is mainly concentrated in the area between the two tongue tips.2.Compared to the AC-type occlusal contact,the ABC-type occlusal contact can effectively reduce the stress on the crown,dentine,and post-core.3.The stress distribution of dentin obviously depend on the kind of post-core material,and the higher the elastic modulus,the higher stress indensity on the tooth tissue.4.The higher the degree of defect,the higher the stress indensity on the tooth tissue after the post and core crown restoration,and it doesn't depend on the defect location.And the degree of defect and occlusal contact will affect the stress distribution among the piles after post-core crown restoration.Conclusion:1.The ABC-type occlusal relationship can reduce the stress of the crown,dentin,and post-core compared to the AC-type occlusal-contact relationship.Proper restoration of the prosthesis should restore the contact of the B zone.2..Compared with zirconia piles,the use of glass fiber pile repair can reduce the risk of cracks.3.The higher the degree of defect,the higher the stress indensity of the tooth tissue after the post-core crown restoration,and the tooth tissue should be retained as much as possible on the basis of removing the thin-walled weak tip.