Cavity Dimension Effect on MOD Dental Restoration Filled with Resin Composite-A Finite Element Interface Stress Evaluation

窩洞尺寸對牙科MOD複合樹脂填補窩洞復形之影響－有限元素分析界面應力分析

張志涵(Chih-Han Chang) ； 方金蘭(Chin-Lan Fang) ； 許瑞廷(Jui-Ting Hsu) ； 陳昌本(Chang-Pen Chen) ； 莊淑芬(Shu-Fen Chuang)

《Journal of Medical and Biological Engineering》 24卷4期 (2004/12) Pp. 195-200

摘要

複合樹脂近年來已被廣泛運用為牙科直接窩洞填補的材料；然而複合樹脂應用於牙科窩洞填補時卻有聚合收縮的缺點，當聚合收縮所產生之界面收縮應力大於複合樹脂與齒質界面的結台強度時，臨床上常造成樹脂與牙齒界面的破壞。本研究藉由有限元素分析，探討在不同尺寸之二級MOD窩洞復形中，樹脂收縮在界面造成的界面應力與窩洞大小的關係。研究以切片取得第二小臼齒塑膠假牙齒的輪廓，以建立三維有限元素網格模型，並在齒冠處建立不同大小的樹脂填補窩洞，利用有限元素熱力分析的模組，以熱漲冷縮的方法進行聚合收縮模擬，並觀察平均界面正向應力、最大界面正向應力，以評估窩洞大小的影響。結果發現窩洞尺寸對界面正向應力之影響並不一致，界面應力並未隨窩洞深度及寬度的增加而增加。經進一步模擬探討發現，剩餘齒質之強度亦是影響界面應力的重要因素，較大的窩洞尺寸會增加樹脂收縮力而提高界面應力，但較大的窩洞也會降低剩餘齒質強度，使的樹脂收縮時界面應力降低。

關鍵字

複合樹脂 ； 聚合 ； 應力 ； 窩洞 ； 有限元素分析

並列摘要

Resin composite has been one of the widely used materials in dental restorations. The polymerization shrinkage of this material is one of the critical defects provoking failures for the restoration. The biomechanical responses resulted from the interface stress between the resin and tooth (generated by the polymerization shrinkage) would be an important issue in determining the success of restoration. The aim of this study was to evaluate the biomechanical effects of cavity dimension in Class Ⅱ MOD (mesial-occlusal-distal) restoration using finite element analysis. Solid model of a plastic synthetic second premolar was established by the transverse section slices of the plastic tooth. The model was then revised to create a sub-volume in the crown region to represent the resin filled cavity with various cavity dimensions. Resin material properties were applied in the elements within the cavity and shrinkage of these elements was simulated by a negative thermal expansion. The interface normal stress between the resin and tooth structure induced by this resin shrinkage was evaluated. The results shown that a larger cavity dimension is not always generated a greater interface stress. Since a larger cavity could increase the degree of contraction that leads to the interface stress, it also weakens the remaining tooth structure thus reduce the interface stress.

並列關鍵字

Resin composite ； Polymerization ； Stress ； Cavity ； Finite element analysis