後牙區樹脂黏合牙橋與支台齒界面之有限元素應力分析

由於幾何外型的複雜及結構的不穩定性，使得樹脂黏合牙橋與支台齒界面的結合強度對於牙橋在臨床使用上的成功率是一個非常重要的考量因素，但臨床觀察或一般的實驗方法卻很難得知咬合力與界面結合強度間的關係，因此本研究利用三維有限元素分析針對咬合應力與牙橋界面破壞之關係進行探討。由於樹脂黏合牙橋幾何結構的複雜，本研究首先利用影像處理技術及CAD (Pro/Engineer)系統建構出牙橋與支台齒之三維實體模型(solid model)，再將其輸入有限元素軟體中(ANSYS v5.3)進行分析，首先在界面結合良好的情況下（即界面為bonded），針對九組不同的咬合力進行固位器和支台齒之界面應力分析，其次再利用先前所分析出來對界面末端產生最大應力值的咬合力，對兩組不同的界面破壞模式（依臨床破壞模式及應力集中模式設定）進行分析（即界面為de-bonding）。結果發現當界面尚未發生破壞時，作用於第二大臼齒頰側遠心咬頭向舌側呈45°之咬合力會對界面末端下方造成應力集中之現象而容易導致界面產生破壞；在咬合力對界面破壞的影響方面，由分析結果得知所模擬的兩種破壞模式（依臨床破壞模式及應力集中模式設定）下，咬合力均會造成義齒支架與牙齒之界面末端產生應力集中的情形，並沿著義齒支架下緣往牙橋本體方向發生，故若以應力為破壞的指標，界面應沿著此方向破壞，但此現象卻與臨床觀察之破壞趨勢不同，因此本研究推斷當界面產生破壞後，應力可能並非導致界面加速破壞的最主要原因，酸性物質的腐蝕作用可能係－更重要之因素。

關鍵字

樹脂黏合牙橋；界面；有限元素法

並列摘要

Due to the complicated geometry and unstable structure of resin-bonded (RB) bridges, the successful bridgeworks in clinical dentistry are usually dominated by the interface strength between the RB bridge and it's abutments. In this study, the three-dimensional finite element method was employed to analyze the interfacial stresses that were difficult to calculate using traditional clinical observation or experimental approaches. Solid models of the RB bridge and abutments were constructed first and assembled in a CAD system to depict reality of their complex geometry, they were then transferred to the mesh model in FE package (ANSYS) to process the stress analyses. Nine different occlusal forces were selected as the loading types to estimate the stress levels at the distal margin area of the bridge's retainer with perfect interfacial bonded conditions. After the loading evaluation, two interface failure types (clinical failure and stress concentration modes) were assumed as the de-bonding conditions to calculate the interfacial stresses under the worst loading case that was obtained in previous analyses. The results indicated that the maximum stress value was obtained at the distal-bottom tip of the bridge when the occlusal load was applied on the buccal distal cup, inclining 45 degrees to the lingual side of the second molar. For interfacial failure analyses, the stress concentrations were found and trended toward the pontic along the distal-bottom margin of the bridge's retainer with two different interface failure types. This interface failure tendency from the stress concentration aspect was not consistent with clinical observations. This study concluded that the occlusal forces might not be the most important factor in the speedup of the interfacial failure; acid erosion might be the significant issue to concern.

並列關鍵字

Resin-Bonded Bridge ； Interface ； Finite-Element Method

國際替代計量

後牙區樹脂黏合牙橋與支台齒界面之有限元素應力分析

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