下颌第一磨牙不同桩核位置数目玻璃纤维桩全瓷修复后基牙应力的三维有限元分析

The three-dimension finite element analysis on mandibular first molar restored with different designed fiber post-core and all ceramic crown

目的通过三维有限元分析玻璃纤维桩全瓷冠修复下颌第一磨牙近中颊壁缺损时,桩的数目和位置对基牙应力的影响。方法对离体下颌第一磨牙使用锥形束CT扫描,提取数据,使用Mimics、Geomagic、Ansys软件建立下颌第一磨牙近中颊壁缺损的三维有限元模型,模拟玻璃纤维桩全瓷冠修复,根据桩数目和位置的不同,设计7种桩核修复模式,分别在最大载荷(F1,600 N)、垂直载荷(F2,225 N)、斜向载荷(F3,225 N)和水平载荷(F4,225 N)作用下,比较载荷、桩的数目和桩的位置对基牙von Mises应力(范式等效应力)极值和应力分布的影响。结果纤维桩全瓷冠修复下颌第一磨牙近中颊壁缺损时,7组模型在四种载荷作用下,牙体组织von Mises应力极值分别为21.854-22.629 MPa(F1)、20.945-21.369 MPa(F2)、21.637-22.513 MPa(F3)、37.922-38.277 MPa(F4)。7组模型间牙体组织von Mises应力峰值和应力分布变化不大;增加桩核的数目对于原桩核应力分布影响不显著;随着载荷侧向力的增加,牙体组织和纤维桩von Mises应力极值逐渐增加。结论玻璃纤维桩全瓷冠修复下颌第一磨牙近中颊壁缺损时,桩数目和位置的变化对修复后基牙应力影响不大。

Objective To evaluate the effect of different numbers and location of fiber post on stress distribution of fiber post-all-ceramic crown restored mandibular first molar,with application of finite element method.Methods Intact human mandibular first molars were used to build three-dimensional finite element models,restored with fiber post core and all ceramic crown.Three-dimension finite element model with 7 different post designs(according to the numbers and location of fiber post inserted into root canal)were created with soft wares of Mimics,Geomagic and Ansys.The von Mises criterion was applied for comparing the maximum von Mises stress value of dentin and stress concentration areas in 7 models maximum load(F1,225 N),vertical load(F2,225 N),inclined load(F3,225 N)and horizontal load(F4,225 N).Results Under maximum load,vertical load,inclined load and horizontal load,the maximum von Mises stress value of dentin were 21.854-22.629 MPa(F1),20.945-21.369 MPa(F2),21.637-22.513 MPa(F3)and 37.922-38.277 MPa(F4),when the mandibular first molar defect was restored with fiber post core and all ceramic crown.There was little difference in maximum von Mises stress values and stress distribution among the 7 groups.Increasing the number of Posts has no significant effect on the stress distribution of the original post.The maximal Von Mises stress on dentine increased when the horizontal direct loads increased.Conclusions The number and location of posts have little influence on maximum stress values and stress distribution,when the mandibular first molar defect was restored with fiber post core and all ceramic crown.