The purpose of this study was to evaluate the characteristics of eight commercially available dental gold casting investments (GI-1, GI-2, GI-3, GI-4, GI-5, GI-6, GI-7 and GI-8) and eight dental high temperature casting investments (HI-1, HI-2,
HI-3,
HI-4, HI-5, HI-6, HI-7 and HI-8) being used in Korea.
The following properties were studied: fineness, consistency, setting time, compressive strength, setting expansion, thermal expansion, surface defects of castings, setting temperature rise and acidity. These tests were performed according to the
KDA
Specification No. 13: Dental gold casting investments, KSP 5205: Dental gold casting investments, RANSI/ADA Specification No. 2: Gypsum-bonded casting investment for dental gold alloy, RANSI/ADA Specification No. 42: Phosphate-bonded investments
JIS T
6601:Dental casting investments.
@ES From the experiments, the following results can be drawn:
@EN 1. In case of the fineness of the gold casting investments, the passed amount was 99.86% to 100% through No. 30 sieve, 39.53% to 91.94% through No. 100 sieve and 9.67% to 79.08% through No. 200sieve. In high temperature casting investments,
the
passed amount was 99.1% to 100% through No. 30 sieve, 45.22% to 73.69% through No. 100 sieve and 13.04%to 25.24% through No. 200 sieve.
2. The consistency of gold casting investments was 55.48±7.7.70mm to 145.32±3.63mm, and that of high temperature casting investments was 88.68±12.66 mm to 145.52±3.09 mm. The setting time of gold casting investments was 8.25±0.66 Min. to
23.75±0.25 Min, and that of the high temperature casting investment was 14.00±0.90 Min. to 23.08±2.04 Min
3. The compressive strength of gold casting investments was 17.95±1.27 Kg/Cm2 to 45.44±4.47 Kg/Cm2, and that of the high temperature casting investments was 28.13±1.83 Kg/Cm2 to 81.38±4.29 Kg/Cm2. The setting expansion of the gold casting
investments was 0.081% to 0.315%, and that of the high temperature casting investments was 0.005% to 1.001%.
4. The thermal expansion of gold casting investments was 0.24% to 0.90% at 700℃, and that of the high temperature casting investments was 0.006% to 0.06% at 1,000℃. The surface irregularities of castings observed were incomplete margin, fin,
surface
roughness and porosities.
5. The temperature rise during setting was 4.40℃ to 9.50℃ with gold casting investments, and that of the high temperature casting investments was 29.50℃ to 36.40℃. The time to reach the peak temperature was 23.8 Min. to 68.2 Min. with gold
casting
investments, and that of the high temperature casting investments was 23.8 Min. to 68.2 Min. The acidity of mixed supernatant water was pH 5.2 to pH 5.6.
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