铸造工艺对钛冠桥精度影响的研究

The Effect of Casting Techniques on the Accuracy of Titanium Crown and Bridge

目的 通过改进纯钛铸造方法提高钛铸件的精确性。方法 采用自行设计的模具制作标准化单冠蜡模4 8个 ,其中 2 4个采用改进铸造法获得试件 2 1个 ,另外 2 4个使用常用的铸造法获得试件 18个。使用测量显微镜按照 90°的 4个点分别测量蜡模和试件边缘距模具肩台的距离 ,观察其边缘适合性 ;用线性切割的方法纵切试件 ,再用测量显微镜测量试件截面内壁选定的 4个点 (B′、C′、D′、E′)到模型的距离 ,观察冠的内部适合性。结果 改进铸造法获得的试件肉眼观边缘更为完整 ,表面更光滑 ;改进铸造工艺前后的蜡模和试件边缘距模具肩台的距离具有统计学上的显著性差异 ,即工艺改进后的边缘适合性更好 ;改进工艺前后B′、E′距模型的距离无统计学上的显著性差异 ,而C′、D′到模型的距离具有显著性差异 ,改进后的内部适合性更好。结论 改进纯钛铸造工艺后标准化单冠试件的精确性有明显提高 。

Objective To investigate the method of enhancing the accuracy of titanium crowns by improving the casting method.Methods A self-assembled die was used to fabricate 48 standardized wax crowns. The dies were averagely divided into two groups. 21 crowns were successfully fabricated from one group according to the improved techniques. 18 crowns were fabricated by traditional method. A reference mark was scribed 90 degrees apart at four sites on the margin of each wax pattern and respective die. The distance between the margins of the wax pattern and the die was measured under a stereomicroscope. Similar method was also applied to measure the margin of castings. The castings were longitudinally split through midline. The distance between the 4 points(B′?C′?D′?E′)selected in the inner part of the crown and the die was respectively examined.Results Castings acquired by the improved method were more complete and had smoother surface. Marginal discrepancy value had significant difference between the two groups. Value in experimental group was smaller. Distance from B′?E′ to die between the two groups had no significant difference, but the distance from C′?D′ to the die was significantly different. The experimental group was smaller.Conclusion Standardized crowns fabricated by the improved titanium casting technique were more accurate, but special investment for titanium crowns and bridges should be developed to compensate the casting shrinkage of metal.