| Project/Area Number |
62570864
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Conservative dentistry
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| Research Institution | SHOWA UNIVERSITY |
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Principal Investigator |
WATANABE Akira SHOWA UNIV, DENTAL FACULTY, LECTURER, 歯学部 (60129880)
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| Co-Investigator(Kenkyū-buntansha) |
HOSOKI Shoji SHOWA UNIV, DENTAL FACULTY, ASSISTANT, 歯学部, 助手 (90181502)
森田 憲治 昭和大学, 歯学部, 助手 (10182239)
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| Project Period (FY) |
1987 – 1988
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| Project Status |
Completed (Fiscal Year 1988)
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| Budget Amount *help |
¥1,800,000 (Direct Cost: ¥1,800,000)
Fiscal Year 1988: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 1987: ¥1,400,000 (Direct Cost: ¥1,400,000)
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| Keywords | Dental precise casting / ringless casting / vacuum casting / casting accuracy / compensation of casting shrinkage / investment / 歯科精密鋳造 / 吸引鋳造 |
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| Research Abstract |
The purpose of this study is to develop an optimum gypsum-bonded investment for the dental ringless casting.
1) Composition of the experimental investment From the results of the measurement of the physical properties, initial setting time, setting expansion, thermal expansion, conpressive strength and diametral tensile strength, the optimum composiscion of experimental investment is decided to be 25% gypsum, 37.5% cristobalite and 37.5% quartz.
2) Water/powder ratio and the direction of a wax pattern in mold The result of the measurement of setting and trarmal expansion of experimental investments showed that the optimum water/powder ratio was 0.35, and a wax pattern should be invested horizontally in a ring.
3) The use of 20k alloy is better than that of Au-Ag-Pd alloy from the comparison of the castings' discrepancy made by two different alloys.
4) Clinical eveluation Inlays made by the use of this experimental investment were set in several patients, and these inlays were evaluated by assessmant of marginal adaptation of these inlays to the cavities one year after placement.
5) Ring's type for making mold Two types of ring were designed to set free the obstruction of the setting expanision of the experimental investment. But these two designed types of ring were worse than the conventional type of ring, when castings' deformation was compared.
An investment of which composition if 25% gypsum, 37.5% cristobalite and 37.5% quartz developed in this research can be used as an investment without ring for the dental casting and the casting made by the use of this investment can be used clinically.
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