1991 Fiscal Year Final Research Report Summary
Ultrastrucure of enamel in experimental dental fluorosis
| Project/Area Number |
01044127
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| Research Category |
Grant-in-Aid for international Scientific Research
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| Allocation Type | Single-year Grants |
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| Section | Joint Research |
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| Research Institution | Tokyo Dental College |
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Principal Investigator |
YANAGISAWA Takaaki Tokyo Dental College, Chiba, Japan, 歯学部, 教授 (10096513)
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| Co-Investigator(Kenkyū-buntansha) |
RICHARDS Alan Royal Dental College, Aarhus, Denmark, 歯学部(Denmark), 助教授
JOSEPHSEN Kej Royal Dental College, Aarhus, Denmark, 歯学部(Denmark), 教授
FEJERSKOV Ole Royal Dental College, Aarhus, Denmark, 歯学部(Denmark), 教授
TOHDA Hisako Tokyo Dental College, Chiba, Japan, 歯学部, 講師 (80085828)
MIAKE Yasuo Tokyo Dental College, Chiba, Japan, 歯学部, 助教授 (00157421)
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| Project Period (FY) |
1989 – 1991
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| Keywords | Fluorotic Dental Enamel / Hypermineralized Layer / Hypomineralized Area / High-resolution Transmisshin Electron Microscopy / High-resolution Scanning Electron Microscopy / Microanalyses / Hydroxyapatite / Fluorapatite |
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| Research Abstract |
Materials were unerupted, erupting, and erupted premolars from young pigs given 2mg/kg b. w. of fluoride in the daily diet for 10 months. Light and polarized microscopic, microradiographic, high-resolution transmission and scanning electron microscopic, energy- and wave-dispersive microanalytic. and microbeam electron and X-ray diffraction studies were made.
Enamel surfaces of unerupted and erupting teeth were cloudy to opaque, defectless, and stain-free. Areas immediately beneath the thin enamel surface layer were opaque, had lost negative birefringence, and were hypomineralized. The thin' surface layer. however, was translucent, negatively birefringent. and hypermineralized. The hypermineralized layer was composed of many large and a few extremely small crystals. Large crystals were elongated hexagons with dark central lines. Though varying somewhat, small crystals were basically regular hexagons without dark central lines. The (001) crystalline planes of large and small crystals revealed lattice striations with 0.817nm and 0.812nm intervals, respectively. Large crystals were identified as hydroxyapatite and small crystals as fluorapatite. Identifications were confirmed by electron and X-ray diffractin studies. The hypomineralized area showed sparcely arranged large crystals and practically no small crystals. A high fluoride concentration was determined in the hypermineralized layer.
After tooth eruption, several pits or defects of various sizes and brownstaining intensities appeared on the surface enamel. In the hypermineralized layer, numbers of small fluorapatite crystals increased. Crystal growth was frequently observed on large-crystal peripheries and on small crystals attached to large-crystal peripheries. A few small crystals appeared in the hypomineralized areas.
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