Abstract
Adaptation or dimensional deviations of the castings produced by Ni-alloys and phosphate bonded investments was evaluated by the ring-type castings fabricated by a direct technique for taking wax pattern and by sectioning the crown-type castings on the preparations embedded in resin.The correlation between dimensional deviations of the working dies for die-investing technique and dimensions of castings was also discussed.The findings were as follows:1)The phosphate bonded investments tested showed the sufficient expansion to compensate the castingshrinkage of Ni-alloy.
2)The observation of the sectioned specimens of the crown-type castings showed that the investing technique using the wax ring made an even space between the castings and the preparation.But the castings produced by the steel ring lined with petrol-jellyed asbestos or wet asbestos showed the restraint of the expansion at the line angle between the axial wall and the occlusal portion. 3)A high positive corrllation of the dimensional deviation was observed between the working dies and the castings in case of the die-investing technique by the phosphate bonded investments.
