| Research Abstract |
The osteodentin, which is physiologically seen in the anterior extrimity of rat incisors and is formed experimentally by exposing the pulp chambers of rat molars, was used in the present study. The animals were fixed with glutaraldehyde; and their teeth were disseected out of the jaws, decalcified with EDTA, and prepared into ultrathin sections following usual procedures for electron microscopy. For demonstraton of phosphatase, the demineralized teeth were prepared into frozen sections of 20 m thick. The sections were incubated by means of the metal-salt technique for the demonstration of ACPase activity (Gomori, 1952) or ALPase activity (Mayahara et al., 1967), postfixed with OsO_4, and then ultrathin sections were preared for electron microscopy. Newly formed osteodentin was characterized by the presence of a number of globular clusters of apatite crystals distributed among mineralizing collagen fibrils. Most cells related to osteodentin formation had round profiles and a rich cytoplasm including a well-developed, ough-surfaced endoplasmic reticulum and a Golgi apparatus. Multivesicular bodies, cytosegresomes, and other sytoplasmic bodies classified by nagai (1970) as cytosome-3, -4 and -6, appeared in the cells. ACPase-activity reaction products were observed in such Golgi elements as lamellae, vacuoles, and vesicles. Cytosom-3, -4 and -6 and multivesicular bodies demonstrated reaction products. In the case of ALPase, reaction products were observed on the cell membraneand in cytosome-6.
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