On the developmental aspect of tooth germs, and the structure and function of tubular enamel in the opossum(Monodelphis domestica).

Abstract

Abstract:The aim of this study is to examine the developmental aspect of the dental lamina and the tooth germ, the structure of the tubular enamel and the function of the enamel tubules in the marsupial, opossum (Monodelphis domestica). The dental formula of the animal used in the present study was 5134/4134=50. In 12-, 16-, and 18-day-old opossum, the tooth germs of the upper and lower deciduous canines, third deciduous molars and first molars, and the upper first deciduous incisor and second molar had successional dental laminae and the replacement tooth germ. The tooth germs of the upper fourth deciduous incisor and the lower first deciduous incisor were reduced. The dental lamina was continued in each jaw except for the upper first deciduous incisor. This dental lamina continued with the oral epithelium in the mesial or distal region of each tooth germ, except for the lower third molar. The first dentition (deciduous dentition) remained as the permanent dentition on the upper first deciduous incisor, and the upper and lower deciduous canines and first molars. The upper fourth incisor and the lower first incisor were the second dentition (successional dentition). The third deciduous molars were replaced by the third premolars in both jaws.Tissue differentiations such as the enamel knot, enamel cord and stratum intermedium were observed as in eutherian mammals. Most enamel prisms, surrounded by interprismatic enamel, ran obliquely from the dentinoenamel junction (DEJ), and bent near the enamel surface. The enamel tubules were distributed in both enamel prisms and the interprismatic enamel near the DEJ. Several enamel tubules ran within one enamel prism. From the middle to the surface of the enamel, one enamel tubule ran in a single enamel prism.One enamel tubule continued from the DEJ to near the enamel surface, and was speculated to develop in relation to one ameloblast. The fiber of the odontoblast process continued from the dentinal tubule distribut-

Plastic casts and confocal laser scanning microscopy applied to the observation of enamel tubules in the red Kangaroo (Macropus rufus)

“…Aligned enamel prisms and well‐developed interprismatic enamel in red kangaroos generally resemble those of other marsupials (Kozawa, 1987; Gilkeson and Lester, 1989; Stern et al ., 1989). However, the distribution of enamel tubules is different from those of some marsupials, such as the opossum, whose tubules run through the enamel and openings of tubules are found on the unworn surface of the enamel (Iwasa, 1997). In the red kangaroo, most tubules are found only in the deep and middle strata.…”