經過根管治療的失活齒，可能會因為原有齲蝕造成齒質不當喪失，或根管治療造成齒體結構的破壞，而導致牙根與牙頸部容易發生斷裂。本研究目的為評估不同受力情況、根柱形狀與根柱材料等因素，對於根管治療後門齒的力學行為影響。
本研究使用有限元素法建構完整三維根柱治療門齒模型作為力學分析。建構的模型包括根管治療完的牙齒、牙周韌帶、硬質骨、鬆質骨、牙齦等結構，並針對門齒內植入根柱之幾何外型(cylindrical、tapered和two-stage cylindrical)、根柱機械材料性質(金合金、不鏽鋼、鈦合金、碳纖維和玻璃纖維)、門齒切緣受不同方向(垂直力、水平力和斜向力)外力等不同條件進行模擬分析，以了解患齒在受力之後，其應力分佈以及形變等情形。
結果發現當增加根柱的直徑和根柱材料的楊氏係數時，都會使根柱上的應力值增加，因此使牙本質上的應力值略減。另外，牙齒受到不同方向外力，也會對於牙齒上的最大應力位置與大小有所影響。牙本質上應力值受水平撞擊力時影響最大，因此在製作牙冠時，考量避免咬合後，水平力的產生，是根管治療修復中重要的因素。

Endodontically treated teeth are prone to fracture, but investigations about restorative variables related to fracture are often inconclusive and contradictory. The effect of different anatomic shapes and materials of posts on the stress distribution in an endodontically treated incisor was evaluated in this work. The purpose of this study was to analyze the stresses in post-restored teeth by using finite element method, and the variables evaluated were loading modes, shapes, diameters, and materials of the posts. The model of the restored tooth consisted of post-and-core, a crown, dentin, periodontal ligament, cortical and cancellous bone, and gingiva. Either of the models combining three post shapes (cylindrical, tapered and two-stage cylindrical) and five different materials (gold alloy, stainless steel, titanium, carbon fibre and glass fiber) was analyzed its contribution in the stress pattern in the post-restored tooth. Three-dimensional stress analysis was performed using the Finite Element Method. Three static loads of 100N was applied at vertical, horizontal and oblique directions on the incisal edge, the generated von Mises stress and deformation were calculated. Results showed that the increase of post diameter and elastic modulus would stiffer the post thus increasing the post stress. On the other hand, the dentin stress would reduced with the increasing of post stress. The loading mode is a vital factor to affect the peak dentin stress magnitude and location. Horizontal force would induce a harmful bending effect on the tooth structure, therefore, the restoration of the devitalized teeth should be cautious to prevent or reduce the bending effect.

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