两种方式修复下颌第一磨牙应力分析

Stress analysis of mandibular first molars repaired in two ways

目的通过建立三壁缺损的下颌第一磨牙有限元模型, 模拟纤维桩全瓷冠和改良高嵌体的修复效果, 分析牙冠缺损位置对基牙应力的影响。方法选择1颗形态完整、因牙周病拔除的下颌第一磨牙。使用锥形束计算机断层扫描(CBCT)获取数据, 使用Mimics、Geomagic、Ansys软件组建下颌第一磨牙模型, 依据三壁缺损的位置和修复方式不同建立8组模型(纤维桩全瓷冠A、B、C、D组和改良高嵌体E、F、G、H组), 选择四种作用力(F1、F2、F3和F4), 比较牙体最大冯·米塞斯应力(Von Mises应力)及分布。结果纤维桩全瓷冠修复(A、B、C、D组模型)时, 牙本质Von Mises应力极值分别为19.334 9~19.907 1 MPa (F1), 8.295 47~8.466 08 MPa(F2), 19.433 5~19.441 4 MPa(F3), 36.109 3~36.199 8 MPa(F4);改良高嵌体修复(E、F、G、H组)时, 牙本质Von Mises应力极值分别为19.493 8~19.864 8 MPa(F1), 9.077 35~9.317 12 MPa(F2), 22.770 6~23.541 2 MPa(F3), 35.724 2~35.989 7 MPa(F4), 各组模型间变化不大。随着载荷角度的增加, 牙本质应力极值增加。相同缺损模式下, F2、F3载荷时, A、B、C、D组牙本质应力极值小于E、F、G、H组;F1、F4载荷时, 八组模型牙本质应力极值相近, 但A、B、C、D组牙本质应力集中区位于牙齿表面, E、F、G、H组髓室内出现应力集中区。结论下颌第一磨牙三壁缺损改良高嵌体和纤维桩全瓷冠修复时, 缺损位置对修复效果无显著影响, 纤维桩全瓷冠更利于分散牙本质应力。

Objective To establish a finite element model of the mandibular first molar with three wall defects,simulate the repair effect of fiber post porcelain crown and modified inlay,and analyze the effect of crown defect location on abutment stress.Methods One intact mandibular first molar was extracted due to periodontal disease.Conical beam computed tomography(CBCT)was used to obtain the data,Mimics,Geomagic,and Ansys software were used to construct the mandibular first molar model,and 8 groups of models(groups A,B,C,D of fiber post all-porcelain crown and groups E,F,G,and H of modified onlays)were established according to different locations and repair methods of the three wall defects.Four forces(F1,F2,F3 and F4)were selected to compare the maximum Von Mises stress and its distribution.Results The extreme values of dentin Von Mises stress were 19.3349-19.9071 MPa(F1),8.29547-8.46608 MPa(F2),19.4335-19.4414 MPa(F3)for fiber post all-porcelain crown restoration(group A,B,C and D models),respectively.36.1093-36.1998 MPa(F4);The maximum values of Von Mises stress were 19.493-19.8648 MPa(F1)in modified high inputate restoration(E,F,G,H).9.07735-9.31712 MPa(F2),22.7706-23.5412 MPa(F3),35.7242-35.9897 MPa(F4).There was litle change among the models.The extreme value of dentin stress increased with the increase of loading Angle.Under the same defect mode,the extreme value of dentin stress in groups A,B,C and D was less than that in groups E,F,G and H at F2 and F3.At F1 and F4,the extreme values of dentin stress in the eight groups were similar,but the dentin stress concentration area in groups A,B,C and D was located on the tooth surface,and the stress concentration area appeared in the pulp chamber in groups E,F,G and H.ConclusionsThe position of the defect has no significant effect on the repairing effect of the modified inlay and the fiber post porcelain crown.The fiber post porcelain crown is more beneficial to disperse the dentin stress.