Abstract:

Objective　To investigate the effect of two different ring liner thickness on the deformation of resulted castings. Methods　GC No.2 casting rings (50 mm in height and 39.5 mm in diameter) were lined with two dry ceramic fiber linerswith thickness of 0.70 mm and 0.45 mm. Plate-like wax patterns with pre-marked points were invested with a gypsum-bonded invest- ment and the rings were cast with a silver-based dental alloy. The difference between the castings and the wax patterns at corre- sponding points was calculated to represent the dimensional change of the investment in the rings at different directions.Results　 The expansion of the investment in the ringwas non-isotropic, with larger radial direction expansion than the axial direction expan- sion(P<0.01). In the scope of this study, the effect of two different ring liner thickness on the casting precisionwas statistically non-significant (P>0.05).Conclusion　The liners with two different thickness failed to eliminate non-isotropic deformation of the castings under the testing conditions of this study.

Key words: ring liner, casting investment, casting precision