Kozawa Y, Iwasa Y, Mishima H
Department of Anatomy, Nihon University School of Dentistry at Matsudo, Chiba, Japan.
Eur J Oral Sci. 1998 Jan;106 Suppl 1:509-12. doi: 10.1111/j.1600-0722.1998.tb02214.x.
The aim of this study was to examine the developmental aspects of the dental lamina and the tooth germ of the marsupial opossum (Monodelphis domestica), and to clarify the dental formula of this animal. Specimens were 12-, 16-, and 18-d-old opossums. 3-D reconstructions were constructed from frontal serial sections. In these animals, the tooth germs of the deciduous maxillary and mandibular canine, deciduous third premolar and first molar, and the deciduous maxillary first incisor and second molar had a successional dental lamina and a replacement tooth germ. The tooth germ of the deciduous maxillary fourth incisor and the mandibular first incisor were reduced. The dental lamina was continuous in each jaw except for the deciduous maxillary first incisor. The first dentition (deciduous dentition) remained as the permanent dentition on the deciduous maxillary first incisor, and the deciduous maxillary and mandibular canine and first molar. The maxillary fourth incisor and the mandibular first incisor were the second dentition (successional dentition). Only the deciduous third premolars were replaced. These results showed monophyodonty caused by both deciduous and replacement tooth germ degeneration.
本研究的目的是研究有袋负鼠（短尾负鼠）牙板和牙胚的发育情况，并阐明该动物的牙式。标本为12日龄、16日龄和18日龄的负鼠。通过额状连续切片构建三维重建模型。在这些动物中，上颌和下颌乳犬齿、乳第三前磨牙和第一磨牙，以及上颌乳第一切牙和第二磨牙的牙胚具有继承性牙板和替换牙胚。上颌乳第四切牙和下颌第一切牙的牙胚退化。除上颌乳第一切牙外，每个颌骨中的牙板都是连续的。第一套牙列（乳牙列）在上颌乳第一切牙、上颌和下颌乳犬齿及第一磨牙上保留为恒牙列。上颌第四切牙和下颌第一切牙为第二套牙列（继承牙列）。只有乳第三前磨牙被替换。这些结果表明，乳牙和替换牙胚退化导致了单牙列现象。
