アジアゾウ(Elephas maximus)の切歯(牙)の組織学的研究 : エナメル質とセメント質について

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The material used was a tusk of a young Indian elephant (Elephas maximus LINNE) without any abrasion on its surface. The tip was covered with a thin enamel layer on the inner and with a thin cementum layer on the outer. Histological examinations by lightmicroscopy and scanning-electronmicroscopy revealed certain characteristics which differed from those of the molar teeth. Hunter-Schreger bands were developed in the inner two-thirds of the enamel layer, although the outer one-third was a prismless enamel layer with distinct Retzius lines. The Hunter-Schreger bands formed more regular rows in the tusk than in the molar teeth. Each band was some 30μm wide and was composed of 10-15 enamel prisms in a parazone. The enamel prism was 4-5μm in diameter and showed a key-hole pattern like that of human enamel. The gingko-leaf patterns characteristic of molar enamel could not be observed in the tusk enamel. Processes of dentinal tubes several μm in length were present in the enamel layer just adjacent to the dentino-enamel junction, although no large enamel spindles were observed. The above-mentioned histological features of Indian elephant tusk enamel are similar to those of the molar enamel of Stegodon, which is considered to represent the ancestral genus of the Indian elephant. The coronal cementum of the tusk was 1-2 mm thick and contained a number of cementocytes and Sharpey's fibers. This structure resembled to that of the root cementum of the molar teeth. The coronal cementum adjacent to the dentine was divided into inner and outer layers by an acellular cementum layer. These two layers were distinguished according to their arrangement patterns of Sharpey's fibers. The cemento-enamel junction formed a rather smooth line in the tusk, whereas an irregular line with many resorption lacunae was observed in the molars.
地学団体研究会の論文
1982-09-25

アジアゾウ(Elephas maximus)の切歯(牙)の組織学的研究 : エナメル質とセメント質について

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