| Project/Area Number |
03670875
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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 |
Functional basic dentistry
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| Research Institution | Nihon university |
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Principal Investigator |
SUMINO Rhyuji Nihon University School of Dentistry. Professor, 歯学部, 教授 (40014378)
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| Co-Investigator(Kenkyū-buntansha) |
IWATA Koichi Nihon University School of Dentistry. Instructor, 歯学部, 助手 (60160115)
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| Project Period (FY) |
1991 – 1992
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| Project Status |
Completed (Fiscal Year 1992)
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| Budget Amount *help |
¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1992: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1991: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Keywords | human / tooth pulp / thermal stimulus / evoked sensation / alveolar nerve / single unit / interstimulus interval / 単一神経活動 |
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| Research Abstract |
The relation between the intradental nerve responses and subjective sensory ratings evoked by thermal stimulation of the teeth was studied in man. When thermal stimulus was applied to the teeth, the subjects described the sensations according to a magnitude scale with 5 different levels : 1 - just discernible sensation (subjective detection threshold rating) ; 2 - 'touch-like' sensation ; 3 - slight pain sensation (threshold pain sensation rating) ; 4 - distinct pain sensation ; 5 - intolerable pain sensation. The early and late sensory responses following both cold and heat stimulation of the tooth were observed. The firing frequency of the heat-sensitive, but not the cold sensitive, units increased linearly in proportion to the increase in magnitude of the early sensory ratings. When repetitive thermal stimuli with interstimulus interval of 180 second (ISI 180) were applied to the thermally low threshold heat sensitive units, clear decrement of spike frequency was observed and the sensory rating was unchanged. ISI 30 did not cause any changes in firing frequencies and sensory ratings of the low threshold units. On the other hand, ISI 180 cause precise increment of firing frequencies and sensory ratings in high threshold units, whereas ISI 30 produced clear decrement of firing frequencies and sensory ratings. Furthermore, strong stimulus which Produce pain sensation was applied to the low threshold units, firing frequencies and sensory ratings showed opposite response profiles in ISI 180, increasing in firing frequencies and decreasing in sensory ratings and both of them showed clear decrement when ISI was 30 second. These findings suggest that thermal stimuli used in this study may evoke neuronal discharges and perceptive sensations by the mechanisms of the hydrodynamic theory, which intrapulpal receptors were activated indirectly by thermal stimulation of the tooth via the fluid flow in the dentinal tubules.
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