| Budget Amount *help |
¥2,300,000 (Direct Cost: ¥2,300,000)
Fiscal Year 1989: ¥300,000 (Direct Cost: ¥300,000)
Fiscal Year 1988: ¥2,000,000 (Direct Cost: ¥2,000,000)
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| Research Abstract |
This work was designed to elucidate crystallographic changes in natural carious enamel lesions and in enamel experimentally demineralized in a 0.01M acetate buffer(PH 4.0) and remineralized in a solution containing lmM Ca, 0.6mM P, and 0.05mM F.
Microradiography showed the surface layer to be highly mineralized and the subsurface to be decalcified in both kinds of enamel. In experimental materials, X-ray diffraction study revealed fluoroapatite in the highly mineralized layer. High-resolution electron microscopy showed the mineralized layer to be composed of sharply outlined polygonal and hexagonal crystals of relatively uniform size. The crystal center in the decalcified layer showed a large perforation. Crystals in these 2 layers were wider and thicker than corresponding crystals in controls. New growth of surviving original crystals and formation of small crystallites among other crystals or inside perforations occurred in the transition zone between the decalcified and demineralized layers.
Results obtained from enamel in natural carious lesions were generally similar, although crystals were of various shapes and sized and were irregularly oriented in the mineralized layer and defective crystals extended from the peripheries in the decalcified layer. In some crystal defects, crystal dissolution had stopped at the so-called central dark line. No fluoroapatite was observed. When Burger's circuit was drawn around a crystal perforation in the decalcified area, lattice defects were seen in both experimental and and natural-carious materials.
The experiment showed that remineralization of decalcified enamel proceeds as the result of growth of surviving crystals and of surviving crystals with which newly formed crystals have fused. In fused crystals, edge dislocation, small-angle grain boundaries, and lattice displacement were frequently detected.
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