口腔金瓷修复体的无损检测研究

口腔金瓷修复体（ＰＦＭ）具有颜色逼真、耐磨性强等优点,广泛应用于牙齿缺损、牙列缺损及牙齿美容的修复等。但是由于陶瓷的脆性和制作工艺的问题,临床中经常出现脱瓷、内部出现裂痕或界面脱落等情况,不仅延长了口腔金瓷修复的时间,而且使修复的费用大大增加,因此需要一种检测方法,在修复前或修复后都能判断金瓷牙齿表面或内部是否存在缺陷。本文将利用声扫描显微镜、Ｘ－射线显微探伤仪对修复体进行无损检测。结果表明,两种方法对缺陷的检测均是可行的。特别是两种方法结合起来使用,能有效无损检测金瓷修复体表面或内部的缺陷的深度和尺寸,将为临床提供广泛的应用前景。     

Comparative study of various internal fixation methods for treating patellar fractures by three-dimensional photoelasticity

Objective: To compare the biomechanical basis of 3 different internal fixation methods: nitinol patellar concentrator (NT-PC),tension band and wire circle in treating patellar fractures. Methods:The epoxy resin three dimensional photoelasticity patellar models were made by precise moulding, and were fixated by nitinol patellar concentrator (NT-PC) , tension band and wire circle respectively. The patellar models with frozen stress stripes were put into the polarized light field and the stress distributions were compared. As for the model fixated by NT-PC, by dividing layer, photographing and tracing, we used the iterative method to calculate the stress value of every internal node of the epoxy resin patellar model, and the character of stress was analyzed. Results:An overall stress field was yielded when the patellar model was fixated by NT-PC, and the stripes were more than that of tension band model and wire circle model, which have only few stress stripes in the fixated layers. Further analysis indicated that there were continuous fixated stresses in the facies articularis and distal pole of patella, and the character of stresses produced by NT-PC were mainly in longitudinal direction, then in transverse direction. The shearing stresses were small. Conclusion: The initiative and continuous memorial stress of NT-PC and its overall stress distribution character are the essence of NT-PC distinguished with tension band and wire circle in treating patellar fractures. The stress character produced by NT-PC is good for the stability of fracture site and prompts fracture healing.     

云纹干涉法对不同层厚比的口腔金瓷修复体界面力学特性的研究

目的 金瓷修复体(PFM)兼具金属强度及陶瓷美观的优点，在口腔医学上得到了广泛的应用，但临床上仍常发生脱瓷并且又多发生在界面处，针对这种情况，通过研究不同层厚比的金瓷修复体试件梁的界面强度，以分析其破坏机理，为加工工艺提供参考。方法 采用云纹干涉法对界面开有贯穿裂纹和未开裂纹试件进行了四点弯曲实验研究，并与有限元计算结果进行了比较。结果 得到裂纹尖端及界面处的位移场、应力场，计算了界面断裂强度及应力等参量，并给出了试件制备、实验方法。结论 由于金瓷层厚比的不同导致金瓷横截面中性层位置发生改变，得出金瓷层厚比对金瓷修复体界面强度有很大影响。