Palamara J, Phakey P P, Rachinger W A, Sanson G D, Orams H J
Cell Tissue Res. 1984;238(2):329-37. doi: 10.1007/BF00217305.
Teeth of three macropod species, M. giganteus, W. bicolor and P. concinna, have been studied using the techniques of light microscopy, scanning- and transmission-electron microscopy and hardness measurement. Light microscope observations showed that the teeth of these species had a translucent enamel region close to the dentine and an outer opaque enamel region at the tooth's surface. These regions were not related to the presence or absence of tubules which are a characteristic feature of marsupial enamel. Hardness tests showed that the opaque enamel was softer than the translucent enamel. Scanning electron microscope observations revealed that there was no correlation between any particular prism packing or orientation and the opaque and translucent enamel regions. Transmission electron microscope observations showed that the translucent enamel region consisted of well defined prisms and well packed, lath-like crystals, whereas the opaque enamel was disrupted by voids (which ranged in size from enlarged micropores to about 2 microns in diameter in extreme cases) between crystals and some randomly oriented, loosely packed crystals. This disruption within the opaque enamel region was more common at prism boundaries but pockets of disrupted enamel were also found within prisms and interprismatic regions. The opacity of the enamel was caused by scattering of light from the voids. The ultrastructure of the opaque enamel region indicated that this region was hypomineralized; hardness tests and polarized light microscope observations were consistent with these results.
已使用光学显微镜、扫描电子显微镜和透射电子显微镜技术以及硬度测量方法，对三种袋鼠物种，即大袋鼠（Macropus giganteus）、双色袋鼩（Wallabia bicolor）和优美侏袋貂（Planigale concinna）的牙齿进行了研究。光学显微镜观察表明，这些物种的牙齿在靠近牙本质处有一个半透明的釉质区域，在牙齿表面有一个外部不透明的釉质区域。这些区域与有袋动物釉质的特征性小管的有无无关。硬度测试表明，不透明釉质比半透明釉质软。扫描电子显微镜观察显示，任何特定的棱柱排列或取向与不透明和半透明釉质区域之间均无相关性。透射电子显微镜观察表明，半透明釉质区域由界限分明的棱柱和排列紧密的板条状晶体组成，而不透明釉质则被晶体之间的空隙（大小从扩大的微孔到极端情况下直径约2微米不等）以及一些随机取向、排列松散的晶体所破坏。不透明釉质区域内的这种破坏在棱柱边界处更为常见，但在棱柱内和棱柱间区域也发现了不连续的釉质区域。釉质的不透明是由空隙对光的散射引起的。不透明釉质区域的超微结构表明该区域矿化不足；硬度测试和偏光显微镜观察结果与这些结果一致。
