[Effect of two different ring liner thickness on the precision of castings].
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 liners with thickness of 0.70 mm and 0.45 mm. Plate-like wax patterns with pre-marked points were invested with a gypsum-bonded investment and the rings were cast with a silver-based dental alloy. The difference between the castings and the wax patterns at corresponding 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 ring was non-isotropic, with larger radial direction expansion than the axial direction expansion (P < 0.01). In the scope of this study, the effect of two different ring liner thickness on the casting precision was statistically non-significant (P > 0.05).


CONCLUSIONS
The liners with two different thickness failed to eliminate non-isotropic deformation of the castings under the testing conditions of this study.
Wang
Wei-xin
WX
Dept. of Prosthodontics, West China College of Stomatology, Sichuan University, Chengdu 610041, China.
Chao
Yong-lie
YL
D002133:Calcium Sulfate; D002516:Ceramics; D003442:Crowns; D003734:Dental Casting Investment; D003735:Dental Casting Technique; D006801:Humans; D019736:Prostheses and Implants
D003734:Dental Casting Investment; D002133:Calcium Sulfate