| Project/Area Number |
14370645
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
補綴理工系歯学
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| Research Institution | SHOWA UNIVERSITY |
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Principal Investigator |
TAMAKI Yukimichi Showa University School of Dentistry, Dept of Oral Biomaterials & Technology, Associate Professor, 歯学部, 助教授 (80197566)
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| Co-Investigator(Kenkyū-buntansha) |
FUKUNAGA Hideki Showa University School of Dentistry, Dept of Crown & Bridge, Assistant Professor, 歯学部, 講師 (50199254)
HOTTA Yasuhiro Showa University School of Dentistry, Dept of Oral Biomaterials & Technology, Assistant Professor, 歯学部, 講師 (00245804)
MIYAZAKI Takashi Showa University School of Dentistry, Dept of Oral Biomaterials & Technology, Chief Professor, 歯学部, 教授 (40175617)
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| Project Period (FY) |
2002 – 2003
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| Project Status |
Completed (Fiscal Year 2003)
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| Budget Amount *help |
¥7,300,000 (Direct Cost: ¥7,300,000)
Fiscal Year 2003: ¥3,100,000 (Direct Cost: ¥3,100,000)
Fiscal Year 2002: ¥4,200,000 (Direct Cost: ¥4,200,000)
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| Keywords | Phosphate-bonded investment / Cast / Ammonia / Dust-free / Paste |
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| Research Abstract |
It is well-known that dental investments are composed of fine powders. However, they may cause a respiratory disease if laboratory workers absorb them by mistake when opening the package, weighing and initially mixing at work. Moreover, phosphate-bonded investments may release harmful ammonia gas for human body. The objective of this research was to produce the paste-like phosphate-bonded investments without ammonia. Two pastes (Code: paste1 &, paste2) were prepared prior to test. Pastel was a mixture of cristobalite (average size; 9.2μm, Tatsumori Cor.) and the phosphate (Magnesium dihydrogenphosphate; Yoneyama chem.) liquefied with distilled water of 20cc. Paste2 was MgO (Magnesium oxide #220, Tateho chem.) coagulated by oily compounds. Four (A-D) experimental phosphate-bonded investments (pastel (g)/paste2(g) = A: 79.6/25.5, B: 82/22.5, C: 84.4/19.5, D:86.8/16.5) were designed and their fundamental properties were evaluated. Paste2 was effective to harden the mold and shorten setting time. Compressive strength of A showed 8.65±1.55MPa as green strength and 7.60±0.62MPa as fired strength. A was obviously strongest in the experimental molds. These strength values became smaller alphabetically, and there were significantly differences among A-D by One-way ANOVA (p<0.05). On the other hand, setting time of A was about 8 minutes and shorter than those of B-D. D was found to set after about 13 minutes from mixing. Thermal expansion is depended on the amount of cristobalite including in the mold. In this study, D containing more pastel was advantageous on thermal expansion. The expansion rate was about 1.8% at 900℃. These results suggest that experimental paste-like phosphaie-bonded investments are useful for operators because of complete dust-free and usable properties as dental casting molds. Hence, we need to explore more suitable paste/paste ratio for dental casting molds or evaluate castings obtained from them.
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