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Journal of Electron Microscopy 48(4): 455-463 (1999)
© 1999 Oxford University Press

Ultrastructural observations of dental epithelial cells and enameloid during enameloid mineralization and maturation stages in stingrays, Urolophus aurantiacus, an elasmobranch

Ichiro Sasagawa*, and Junji Akai1

Department of Anatomy, The Nippon Dental University 1-8 Hamaura-cho, Niigata 951-8580
1Department of Geology, Niigata University 8050 Ikarashi-ninocho, Niigata 950-2181, Japan

*To whom correspondence should be adressed. E-mail: ichsasgw{at}ngt.ndu.ac.jp

The fine structure of enameloid and dental epithelial cells in tooth germs of sepia stingrays, Urolophus aurantiacus, an elasmobranch, during enameloid mineralization and enameloid maturation was investigated using light and transmission electron microscopy. The findings suggest that dental epithelial cells are involved in the degeneration and removal of the enameloid matrix during later stages of enameloid formation, and its peak is during the mineralization stage. During the mineralization stage, a large number of denned crystals were observed in the enameloid layer. In demineralized sections, small fragments of cell membrane and electron-dense fibrils remained. The inner dental epithelial (IDE) cells contained well-developed smooth endoplasmic reticulum, and many vesicles, vacuoles and granules containing electron-dense substance. Thick lamina densa was found beneath the distal end of the IDE cells. The outer dental epithelial (ODE) cells possessed many mitochondria, small electron-dense bodies, vesicles and intermediate filaments, and the capillaries usually approached the ODE cells. During the maturation stage, the IDE cells were reduced in height, and had many lysosomal bodies, vesicles, and mitochondria in the distal cytoplasm. The ODE cells became smaller. The lamina densa was almost absent and the distal end of the IDE cells often seemed to be in direct contact with the enameloid surface.

Keywords     ameloblasts, biomineralization, elasmobranchs, enameloid, odontogenesis, transmission electron microscopy

Received     21 January 1999, accepted 26 May 1999


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