1997 Fiscal Year Final Research Report Summary
High-resolution electron microscopy of abnormal crystals appeared in fluorotic enamel.
| Project/Area Number |
07457433
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Morphological basic dentistry
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| Research Institution | Tokyo Dental College |
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Principal Investigator |
YANAGISAWA Takaaki Tokyo Dental College, Department of Dentistry, Professor, 歯学部, 教授 (10096513)
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| Co-Investigator(Kenkyū-buntansha) |
MIAKE Yasuo Tokyo Dental College, Department of Dentistry, Assistant Professor, 歯学部, 助教授 (00157421)
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| Project Period (FY) |
1995 – 1997
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| Keywords | fluoride / dental fluorosis / enamel / ameloblats / optical microscopy / polarized microscopy / microradiography / high-resolution electron microscopy |
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| Research Abstract |
This study attempts to clarify the changes caused by fluoride in enamel crystals from incisors of male wistar rats given drinking water containing 200ppm F for 10 weeks. Enamel and ameloblats were observed by means of optical-and polarized-microscopies, contact micro-radiography, transmission and high-resolution transmission electron microscopies.
Areas immediately beneath the enamel surface layr were cloudy to opaque, had lost their negative birefringence, and were hypomineralized. The surface layr, on the other hand, was translucent, negative birefringent, and highly minerlized.
The highly mineralized surface layr was composed of many large and small crystals.Some large crystals had a central dark line and showed a elongated hexagonal configuration. The crystalline (001) planes revealed lattice striations, with 0.817nm intervals, crossing each other at a 60ﾟ angle. Crystal growth on the surface of the large crystals, the attachment of extremely small crystallites to their surfaces, and crystal-to-crystal fusion were frequently observed. Though varied somewhat in configuration, the small crystals were basically regular or irregular hexagons. The (001) crystalline planes of the small crystals too demonstrated sets of lattice striations crossing each other at a 60ﾟ angle. However, the intervals of the striations were 0.812nm.
The hypomineralized subsurface enamel area was composed of fairly sparsely arranged, elongated hexagonal crystals. The crystal size of them was smaller than those observed in the highly mineralized layr. In addition, fluoridated-hydrxyapatite and modified octacalcium phosphate were observed sometimes in wide intercrystalline spaces. Ameloblasts showed morphological changes and functions.
These findings strongly suggest that fluoride administration causes excessive crystal growth in the highly mineralized layr and the appearance of abnormally crystals directly and/or indirectly.
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[Publications] Sasaki, T., Takagi, M., and Yanagisawa, T.: Structure and function of secretory ameloblasts in enamel formation, in "Dental Enamel", Ciba Foundation Symposium #205. John Wiley and Sons, Chichester, England, 32-50
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