1990 Fiscal Year Final Research Report Summary
Ultrastructure and Crystallographic Study of Enamel in Human Dental Fluorosis.
| Project/Area Number |
63440071
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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 |
Morphological basic dentistry
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| Research Institution | Tokyo Dental College |
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Principal Investigator |
MIAKE Yasuo Tokyo Dental College, Dept. of Oral Pathology, Lecturer, 歯学部, 講師 (00157421)
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| Co-Investigator(Kenkyū-buntansha) |
YANAGISAWA Takaaki Tokyo Dental College, Dept. of Oral Pathology, Associate Professor, 歯学部, 助教授 (10096513)
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| Project Period (FY) |
1988 – 1990
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| Keywords | Dental fluorosis / Enamel crystal / Highly mineralized layer / Hypomineralized layer / Hydroxyapatite / Fluorapatite / Micro analysis / High resolution Electron Microscope |
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| Research Abstract |
Materials used in this work were permanent molars of human and porcine dental fluorosis.
Enamel surfaces from human subjects with dental fluorosis were generally cloudy to opaque, with several pits or defects of various size and degrees. Porcine subjects with dental fluorosis, however, were not seen pits or defects. Immediately below the relatively highly mineralized outermost surface enamel layer was an extensive hypomineralized area. The highly mineralized layer was composed of many large elongated hexagonal crystals and small hexagonal crystals. In some parts of the large crystals, crystal growth on the surface or attachment of extremely small crystals to the surface were observed. The lattice striations of the large and extremely small crystals were connected to each other in exact register. In views along the (100) plane, lattice intervals of large elongated hexagonal crystal were 0.817 nm. Shapes of small crystals were equilateral-hexagonal or nonequilateral-hexagonal and lattice
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intervals of it were 0.812 nm. This result showed that large elongated hexagonal crystals were hydroxyapatite and small crystals were fluorapatite. The hypomineralized enamel area was composed of fairly sparsely arranged, large crystals and a few small crystals. Large crystals were generally smaller than those observed in the surface layer. In some parts of this area, either the crystals large had perforations in their centers or irregular defects formed on their surfaces. Porcine subjects, however, were not seen those crystals. Both large and small crystal were observed in the transitional region between the highly mineralized surface layer and the subsurface hypomineralized area. Central perforations within the large crystals frequently contained apparently newly formed crystal fragments. Lattice striations between the original crystals and the newly formed crystalline material were not always in register with each other. Wave-dispersive electron-probe line analysis indicated that fluoride concentration was very high in the highly mineralized surface layer and low in the hypomineralized area. Less
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