1992 Fiscal Year Final Research Report Summary
Dynamic Fatigue Properties of Human Teeth
| Project/Area Number |
01440079
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| Research Category |
Grant-in-Aid for General Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Research Field |
補綴理工系歯学
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| Research Institution | Tokyo Medical and Dental University |
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Principal Investigator |
NISHIMURA Fumio TOKYO MED & DENT.UNIV., FAC.of DENT.,Professor, 歯学部, 教授 (10013856)
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| Co-Investigator(Kenkyū-buntansha) |
NAKAMURA Hideo TOKYO MED & DENT.UNIV., FAC.of DENT.,Research Associate, 歯学部, 助手
WATARI Fumio TOKYO MED & DENT.UNIV., FAC.of DENT.,Research Associate, 歯学部, 助手 (70158682)
OKAZAKI Kunio TOKYO MED & DENT.UNIV., FAC.of DENT.,ex-Research Associate, 歯学部, 元助手 (90150292)
TAKAHASHI Hidekazu TOKYO MED & DENT.UNIV., FAC.of DENT.,Lecturer, 歯学部, 講師 (90175430)
NOMTO Sunao TOKYO MED & DENT.UNIV., FAC.of DENT.,ex-Professor, 歯学部, 元教授 (10013799)
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| Project Period (FY) |
1989 – 1992
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| Keywords | TOOTH / DENTIN / DENTAL MATERIALS / FATIGUE TEST / FATIGUE LIMIT / RESTRATIVE MATERIALS / SENILITY / DYNAMIC TEST |
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| Research Abstract |
K_<IC> of human enamel was examined by means of IM methods. K_<IC> of old man's teeth was 0.61 MPa.m^<1/2> in 1 and 0.77 MPa.m^<1/2> in 7 and the difference was significant (P<0.01). K_<IC> differed much from the direction of the indenter pressed to enamel rods and was 0.61 MPa.m^<1/2> in the direction of V, 0.66 MPa.m^<1/2> in the direction of H and 0.84 MPa.m^<1/2> in the direction of I, and the difference was significant (P<0.01). The values for a young man's permanent teeth was slightly higher but showed a similar inclination to an old man's teeth. K_<IC> of human enamel irradiated by CO_2 laser showed decreasing tendency in all irradiated spots.
A new tensile fatigue testing methods using a stainless steel screw was introduced. The preferred applied load waveform was the cyclic haver-triangle load because of the small coefficient of variance. Statistical definition of the fatigue limit at 10^5 stress cycles, was obtained by testing according to the staircase method. In 37ﾟC water, fatigue limit of gallium alloy was 29.5 MPa, and that of high copper amalgam was 26.9 MPa.
In general, fatigue limit of young man's dentin was higher, and did not fractured within 60,000 cycles of stress in spite of high maximum applied stress of 34 MPa. But old man's dentin fractured easily within 20,000 cycles of stress in spite of low maximum applied stress of 28 MPa. Fracture surface of fatigue-tested dentin specimens were evaluated using SEM. In the crack origin zone of dentin, several large dentin tubules were seen. And these tubules were thought to act as a defect, and stress concentration were occurred at this region.
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