开髓方式与全冠修复对上颌中切牙应力分布影响的三维有限元分析

Three-dimensional finite element analysis of different endodontic access methods and full crown restoration in the maxillary central incisor

目的采用三维有限元分析法分析不同开髓方式及全冠修复对上颌中切牙牙体组织应力分布的影响。方法采用锥形束CT扫描上颌中切牙构建上颌中切牙三维实体模型,根据开髓方式的不同及是否行全瓷冠修复建立4组实验模型:传统开髓树脂充填(A)组、传统开髓后全瓷冠修复(B)组、微创开髓树脂充填(C)组和微创开髓后全瓷冠修复(D)组。于舌侧切1/3与中1/3交界处施加大小为100 N、与牙体长轴呈45°方向的力,对所建立的牙体组织有限元模型中最大主应力、von Mises应力和改良von Mises应力进行分析。结果1)应力峰值:A组的最大主应力、von Mises应力和改良von Mises应力的应力峰值均表现为最大,除了D组的von Mises应力峰值略低于C组外,C组的最大主应力及改良von Mises应力的应力峰值均表现为最低,D组的最大主应力及改良von Mises应力的应力峰值均低于A组和B组。2)应力分布:相比于A组,C组牙颈部区域的应力集中程度较低,且应力集中的区域较小;在牙根牙本质处,C组的应力分布与A组相比更为均匀,应力分散至根尖更多区域;冠修复后,B组和D组在牙根区域的应力分布未见明显差异;B组应力分布状态与A组相比未见明显改变;D组相比于C组应力分布状态未见明显改变。结论从生物力学角度考虑,上颌中切牙开髓尽量采取微创开髓方式;传统开髓后建议行冠修复,微创开髓后冠修复未见明显优势。

Objective This study evaluates the effects of different endodontic access methods and full-ceramic crown on the stress distribution in the maxillary central incisor by using three-dimensional finite element analysis.Methods Computed tomography scans of the maxillary central incisor were used to construct a three-dimensional finite element model of the maxillary central incisor.According to the different methods of endodontic and the prosthetic treatments,four models were established,namely,group A(traditional access cavity preparation with resin filling),group B(traditional access cavity preparation restored full-ceramic crown),group C(minimally invasive endodontics with resin filling)and group D(minimally invasive endodontics restored full-ceramic crown).A static force of 100 N and a direction of 45°was applied to the long axis of the tooth at the junction of the incisal section one-third and middle section one-third.The maximum principal stress,the von Mises stress and the modified von Mises stress of the tooth tissue were analyzed using the finite-element analysis software.Results 1)Stress peaks:the stress peaks of the maximum principal stress,the von Mises stress and the modified von Mises in group A were the largest,except that the stress peak of von Mises stress in group D was slightly lower than that in group C.The stress peaks of the maximum principal stress and the modified von Mises in group C were the lowest.The stress peaks of the maximum principal stress and the modified von Mises stress in group D were lower than those in groups A and B.2)Stress distribution:compared with group A,the stress distribution of cervical dentin and the area of stress concentration in group C was lower and smaller.In the root dentin,the stress distribution in group C was more uniform than that in group A,and the stress was dispersed to several areas of the root apex.After crown restoration,no significant difference was observed in stress distribution between groups B and D in the root region.The stress distribution state of group B was not significantly different from that of group A.No significant difference was observed in the stress distribution state between groups D and C.Conclusion 1)From the perspective of biomechanics,the minimally invasive access was adopted for the maxillary central incisor.2)Full crown restoration is recommended after traditional access cavity preparation.No obvious advantage is observed in stress analysis for minimally invasive endodontics-restored full-ceramic crown.