三维有限元分析不同材料不同方法修复离体牙缺损模型的应力分布

Different materials and different methods for repairing an isolated tooth defect model: a three-dimensional finite element analysis of stress distribution

背景:如何最大限度地保留根管治疗后的牙体组织,并能够保证修复后的强度是目前的研究热点。目的:使用有限元法分析不同方式修复离体牙缺损模型的应力分布情况。方法:收集北京市海淀医院口腔科因慢性牙周炎无法保留而拔除的上颌第一磨牙12颗,根管治疗后制备离体牙缺损模型,以钴铬合金、纯钛金属、二氧化锆、E.max全瓷为修复材料,每种材料分别进行嵌体、高嵌体、桩核冠3种修复方式。通过MicroCT扫描上颌第一磨牙修复模型,使用图像处理软件Mimics17.0及Geomegic Studio 2013重建牙体及修复体三维数字模型,采用有限元分析软件进行力学模拟,力加载方式设为:8点90°加载、3点90°加载、3点90°加载、3点0°加载。结果与结论:在各载荷条件下,桩冠组修复体边缘、预备体肩台、剩余牙本质颈部及桩核中部出现应力集中区;在各载荷条件下,嵌体组釉质的加载点出现应力集中区,并有将应力沿牙釉质传到至颈部的趋势,嵌体和预备体相对的龈壁和底面及二者移行处也出现应力集中区;在各载荷条件下,高嵌体组高嵌体与牙釉质接触处出现应力集中,预备体龈壁和底面及二者移行处,以及相对应的高嵌体髓腔内部分也出现应力集中的情况,但应力分布更为均匀;结果表明在上颌磨牙大面积缺损的修复方式中,高嵌体具有适用性和优势性。

BACKGROUND:Current concerns are on how to maximize the reservation of tooth tissues after root canal treatment and to ensure the strength of the tooth after repair.OBJECTIVE:To analyze the stress distribution of an isolated tooth defect model after repair with different methods METHODS:We collected12maxillary first molars which had been extracted for chronic periodontitis at the Department of Stomatology,Beijing Haidian Hospital in China.After root canal treatment,the isolated tooth defect model was prepared and repaired with different materials(cobalt-chromium alloy,pure titanium metal,zirconium dioxide,E.max all-ceramic)and using different repair methods(inlay,onlay,post-core crown).First,the model repaired by the corresponding materials and repair methods was scanned by Micro CT.The image processing software Mimics17.0and Geomegic Studio2013were then used to reconstruct the three-dimensional digital models of the tooth and restoration,and a simplified three-dimensional model of the alveolar bone was created.Finally,the above model data was imported into the finite element analysis software for mechanical simulation(the force was loaded at an angle of90o at8,3,3points and at an angle of0o at0point,respectively).RESULTS AND CONCLUSION:Under different loading conditions,in the post-core crown group,the stress was concentrated in the edge of restoration,the shoulder of the preparation,the neck of the residual dentin,and the middle part of post-core crown in the post-core crown group.In the inlay group,the stress was concentrated in the load point of the enamel,and was transferred along the tooth enamel to the tooth neck;the stress concentration area also included the gingival wall and undersurface and transition site corresponding to the inlays and preparations.In the onlay group,the stress concentration occurred at the contact between the onlay and the enamel,at the gingival wall and undersurface of the preparation,and at the transition site.The stress was also concentrated and distributed evenly in the corresponding pulp cavity of the onlay.To conclude,the onlays have applicability and superiority in the repair of large-area defects of the maxillary molars.