Objective: The objective of this paper is to analyze the stress distribution in the deep wedge-shaped defective mandibular first premolars restored with different methods.
Methods: Three-dimensional finite element models of mandibular first premolar with deep wedge-shaped defect were created. The model, which was untreated after root canal treatment, served as the control group. Then, according to different treatment designs, four experimental groups were established as follows: resin filling (A), post restoration after resin filling (B), crown restoration after resin filling (C), and post and crown restoration after resin filling (D). Four different post materials were then chosen for establishing the subgroup models: fiber post (B1, D1), AuPd post (B2, D2), pure Ti post (B3, D3), and CoCr post (B4, D4). A force of 100 N was applied at a 30° angle on the buccal-inclined surface near the top of the buccal cusp. The maximum principal stress and Von Mises stress were investigated using finite element analysis software.
Results: 1) For the control group, the maximum principal stress and Von Mises stress of the residual dentine were the same as those of the tip of the defect. 2) Compared with the control group, the maximum principal stress and Von Mises stress of groups A, B, C, and D decreased greatly (P<0.05). The maximum principal stress and Von Mises stress of groups C and D with crowns were similar. The maximum principal stress and Von Mises stress of the post-dentine surface of groups B and D with fiber post were less than those in the cast metal post models (P<0.05). 3) The displacement of the buccal cusp of group A was similar to that of the control group (P>0.05) and larger than those in groups B, C, and D (P<0.05).
Conclusions: It is necessary for deep wedge-shaped defective teeth to be treated with full crowns, but a post is not necessary. If a post is used, fiber post with elastic modulus closer to the dentine is more suitable than metal post. .
目的 应用三维有限元法分析不同修复方法对深型楔状缺损下颌第一前磨牙应力分布的影响。方法 采用CT扫描下颌第一前磨牙后建立三维有限元模型，模拟深型楔状缺损，建立根管治疗后楔状缺损处未做任何处理的模型作为对照组，同时按照根管治疗后修复方法的不同建立4个实验组模型：树脂充填（A）组、树脂充填后桩修复（B）组、树脂充填后冠修复（C）组、树脂充填后桩冠修复（D）组；根据桩的材料将B、D组分为4个亚组：纤维桩（B1、D1）组、金钯桩（B2、D2）组、纯钛桩（B3、D3）组和钴铬桩（B4、D4）组。分别以100 N、30°斜向力加载于模型的颊尖顶偏颊面，应用有限元分析软件分析模型中各处最大主应力和Von Mises应力。结果 1）对照组模型剩余牙体组织最大主应力和Von Mises应力峰值与缺损尖端处牙本质的相同。2）A、B、C、D组模型的剩余牙体组织、缺损尖端处牙本质的最大主应力和Von Mises应力峰值均较对照组明显降低（P<0.05）；全冠修复的C组的最大主应力和Von Mises应力峰值与D组近似；根管内放置桩的B、D两组中，纤维桩修复的桩—牙本质界面处牙本质应力峰值明显小于铸造桩组（P<0.05）。3）A组模型颊尖位移值与对照组相似（P>0.05），但大于B、C、D组（P<0.05）。结论 深型楔状缺损患牙根管治疗后应行全冠修复；在根管内放置桩并不是必须的，若放置桩，应选择与牙本质弹性模量接近的纤维桩。.
Keywords: full crown; post; three-dimensional finite element; wedge-shaped defect.