2003 Fiscal Year Final Research Report Summary
Improvement of Castable Ceramics
| Project/Area Number |
12671906
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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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 | The Nippon Dental University |
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Principal Investigator |
HATA Yoshiaki The Nippon Dental University, School of Dentistry at Niigata, Professor, 新潟歯学部, 教授 (90060433)
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| Co-Investigator(Kenkyū-buntansha) |
MURATA Yoko The Nippon Dental University, School of Dentistry at Niigata, Assistant, 新潟歯学部, 助手 (00297962)
HATA Syuichi The Nippon Dental University, School of Dentistry at Niigata, Lecturer, 新潟歯学部, 講師 (10297963)
TAWADA Yasuyuki The Nippon Dental University, School of Dentistry at Niigata, Assistant Professor, 新潟歯学部, 助教授 (60179918)
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| Project Period (FY) |
2000 – 2003
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| Keywords | castable ceramics / crystallization / flexural strength / β-spodumene / mica |
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| Research Abstract |
We have experienced many failured cases on castable ceramic restorations during more than ten years clinical use. So, changing compositions of conventional Olympus castable glass ceramics (OCC) was decided as a countermeasure. They are 5 mol% mica crystal (MA-5), 5 mol% β-spodumene crystal (SP-5) and 10 mol% β-spodumene crystal (SP-10) added to OCC respectively. These materials (OCC, MA-5,SP-5,SP-10) were casted into the square column (4×3×25mm) specimens for the flexural strength test. Specimens were crystallized under following conditions respectively (temperature 883℃ and 933℃, holding time 0, 30 and 60min) and tested by three-point bending test. And the results were as follows. OCC (933℃, holding time 0min.) showed the highest value (196.08±30.63MPa) and MA-5 (883℃, holding time 30min.) did the most lowest (87.13±25.13MPa). To compare these results, 6×6×6×12mm prism-shaped crystalized specimens were made under following conditions ; one was the OCC (933℃, holding time 0min.) above mentioned (H) and the other was followed by the OCC manual (883℃, holding time 0min.)(N). Fracture toughness for these specimens were tested by notchless triangular prism (NTP) method and the results were as follows. N showed 2.56±0.37 MPa・m^<1/2> and H did 3.35±0.52MPa・m^<1/2>. H value was significantly higher than N. Then we considered some reinforcement methods of OCC. One of them was an application of electroforming technique to OCC. Anterior OCC crown were compared to the electroformed OCC crown by compressed strength test and results were as follows. The former's value was 90.92±10.13kgf and the latter was 118.17±21.83kgf. Changing the compositions of OCC couldn't surpass the mechanical properties of conventional OCC. And it was suggested that OCC was possible to be reinforced by the electroforming technique. But the material itself has a very high quality, it's more important to decrease a structural defect such as a trapped air.
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