铸造工艺对钛冠桥精度影响的研究

Objective To investigate the method of enhancing the accuracy of titanium crowns by improving the casting meth- od.Methods A self-assembled die was used to fabricate 48 standardized wax crowns. The dies were averagely divided into two groups. 21 crownswere successfully fabricated from one group according to the improved techniques. 18 crownswere 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. Similarmethodwas 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 be- tween the two groups. Value in experimental groupwas smaller. Distance from B′、E′to die between the two groups had no signifi- cant difference, butthe distance from C′、D′tothe diewas significantly different. The experimental groupwas smaller.Conclusion Standardized crowns fabricated by the improved titanium casting technique were more accurate, but special investment for tita- nium crowns and bridges should be developed to compensate the casting shrinkage of metal.