ヒト幼若エナメル質の萌出後成熟に関する研究

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  • Post-eruptive Maturation of Immature Young Enamel

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Post-eruptive changes in human dental enamel were examined by polarizing microscopy, microradiography, and an electron probe X-ray microanalyzer.<BR>Eleven caries-free permanent first premolars which were extracted for orthodontic dontic purposes from 6 patients who were in three groups,11,13, and 18 years of age were examined. Buccolingual sections were ground down to approximately 100 μm thickness.<BR>In the 11 year old age group,microradiography showed radiolucency in an approximately 70 μm surface layer which corresponded to positive birefringence in water with polarized light,and an electron probe X-ray microanalyzer showed a 6 to 7 % Ca and P decrease in an approximately 100 μm surface layer which corresponded to positive birefdngence in air.The most surface layer of 15 to 20 μm showed negative bireffingence,radio-opacity,and not as much of a decrease of Ca and P as did the inner layer. Therefore, it is obvious that positive birefringence fringence with polarized light is not due to a difference of crystal texture but to under calcification. In the 13 year old age group, the depth of the layer which showed positive birefringence, radiolucency, and decrease of Ca and P decreased. In the 18 year old age group, no layer of positive birefringence, radiolucency, and no decrease of Ca and P was seen. This indicated completion of calcification, i.e. fully mature enamel.<BR>From these findings, it is speculated that at first, after eruption, the most surface layer of immature young enamel is calcified by the effects of saliva, food, drinks etc., and then from the bottom of the subsurface inner layer the calcification increases. Finally, the enamel will complete calcification, and develop into fully mature enamel.

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