人造全冠牙体预备不同设计对粘固剂微折的影响

Effects of different complete crown tooth preparations、upon cement microfracture

目的：分析人造全冠牙体预备不同设计对微渗漏的影响．方法：采用三维有限元分析法，分析三单位全冠固定桥同时轴向加载１５０Ｎ，在不同锥度，不同高度，不同颈缘设计条件下，不同粘固剂所受的应力大小及其分布．共建立１４个有限元计算模型，锥度分别为０°，６°，１２°，２５°；高度分别为４，５及６ｍｍ；颈缘设计分别为９０°肩台和１３５°凹面形；粘固剂分别为磷酸锌粘固剂，玻璃离子粘固剂和复合树脂．结果：随着锥度的增大和高度的降低，粘固剂所受的平均应力值增大；不同颈缘设计对粘固剂总应力影响不大，对颈缘所受应力影响较大；在同等条件下，磷酸锌粘固剂所受应力最大，其次是复合树脂，玻璃离子粘固剂所受应力最小．结论：在牙体预备锥度较大，高度较低的情况下，不宜选择１３５°凹面设计和磷酸锌作为粘固剂．

This study aimed to analyze the effects of complete crown tooth preparations on cement microfrac-ture. A three-dimensional finite element analysis(FEA)was selected to determine the stress levels and dis-tributions on dental cements resulting from 150N occlusal loads on three-unit complete artificial crowns under various conditions Fourteen 3D-FEA computer models were generated to study the effects of(1)different tapers(0-degree,6-degrees,12-degrees,25-degrees);(2)different heights(4 mm,5mm,6 mm);(3)marginal configrations(90-degree shoulder, 135-degree champher)and(4) three types of cement(zinc phos phate,glass ionomer,composite resin ).The results showed that there was almost no difference between a champher and shoulder marginal configuration except at the edge of the margin where the champher finish line stresses were greater,but these stresses were magnified for teeth prepared with short and/or over-ta-pered axial walls. Under the same conditions,the zinc phosphate cement stresses were greatest among the three types of cement, and the glass ionomer cement stresses were the least.