AMELOGENESIS OF HUMAN TEETH AS REVEALED BY ELECTRON MICROSCOPY .2. DEVELOPMENT OF ENAMEL CRYSTALLITES
AMELOGENESIS OF HUMAN TEETH AS REVEALED BY ELECTRON MICROSCOPY .2. DEVELOPMENT OF ENAMEL CRYSTALLITES
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DOI：
10.1016/s0022-5320(62)80036-7
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发表时间：
1962-01-01
期刊：
影响因子：
--
通讯作者：
RONNHOLM, E
中科院分区：
文献类型：
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作者：
RONNHOLM, E
人类牙釉质的微晶石出现在特征性的“陶氏”过程发展之前。最初的晶体与胶原纤维混合在一起。后来，与淀粉变性有关的胶原蛋白不能被观察到。第一个晶体似乎是突然形成的，厚度约为15a的相当长的板或带状。它们很早就达到了成熟晶体的宽度和长度，釉质钙化是由于晶体的厚度逐渐增加。在一个早期阶段，以交错方式排列的薄晶似乎发生了融合。在4-5个月大的胚胎中，最成熟的晶体厚度达到170 a。晶体的平均长度约为1600 A，平均宽度约为400 A。在青少年牙釉质中，靠近牙本质-牙釉质交界处的晶状体比靠近牙釉质自由表面的晶状体薄。这种差异解释了珐琅质帽的这些区域的牙釉质棱柱直径的差异。因此，除了一个非常早期阶段的例外，牙釉质的钙化主要是由于在钙化的第一步形成的晶体厚度的增长。新晶状体的形成是釉质棱柱纵向生长的原因。牙釉质钙化的第一步似乎与牙釉质基质的形成同时或几乎同时发生。棱镜中晶体的取向差异可以用棱镜与成釉细胞表面形成的角度和晶体的大致垂直取向来解释。棱镜最初是紧密排列的，但后来形成了棱镜间的间隙。在电子束中部分升华后的晶体特征结构可能表明它们不是均匀的。
The crystallites of human enamel appear before a characteristic Tomes'' process has been developed. The very first crystallites are mixed with collagen filaments. Later no collagen can be observed in connection with the amelogenesis. The first crystallites appear to be formed abruptly as fairly long plates or ribbons about 15 A in thickness. They attain very early the width and length of mature crystallites enamel calcification then being due to a gradual increase of the thickness of the crystallites. During one early stage a fusion of the thin crystallites arranged in rows in a staggered fashion seems to occur. The most mature crystallites have grown to a thickness of 170 A in the 4-5-month old embryo. Mean length of crystallites is about 1600 A and mean width about 400 A. In adolescent enamel the crystallites close to the dentine-enamel junction are thinner than the crystallites close to the free surface of the enamel. This difference accounts for the difference in diameter of the enamel prisms at these regions of the enamel cap. Therefore, with a possible exception for one very early stage in amelogenesis the calcification of the enamel is due to a growth mainly with respect to thickness of crystallites formed during the first step of calcification. The formation of new crystallites accounts for the length-wise growth of the enamel prism. The first steps of calcification of the enamel appear to occur simultaneously or almost simultaneously with the formation of an enamel matrix. The difference in orientation of the crystallites in the prism is explained by the angle the prism forms with the ameloblast cell surface and by the roughly perpendicular orientation of crystallites. The prisms are first closely packed but later interprismatic gaps develop. A characteristic structure of the crystallites after partial sublimation in the electron beam might indicate that they are not hemogeneous.