NOTES ON TOOTH REPLACEMENT IN THE NILE CROCODILE CROCODILUS NILOTICUS
NOTES ON TOOTH REPLACEMENT IN THE NILE CROCODILE CROCODILUS NILOTICUS
复制标题
尼罗河鳄鱼 (Crocodilus Niloticus) 更换牙齿的注意事项
DOI：
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发表时间：
2009
期刊：
影响因子：
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通讯作者：
D. Poole
中科院分区：
文献类型：
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作者：
D. Poole
描述了鳄鱼牙齿的历史和更换。一颗新的牙齿长出来，只有一个短根，向下生长到牙槽中，因为牙冠中的髓腔开始被牙本质的进一步沉积所堵塞。当牙根完全伸展后，它的根部逐渐被吸收，为在牙槽舌侧形成的扩大的连续牙腾出空间。继承牙最终移动到部分吸收的功能性牙根内的位置，并直接位于功能性牙冠下方。功能性牙根逐渐缩小，以适应不断扩大的继承性牙齿，当吸收基本完成时，功能性牙齿福尔斯脱落，允许具有短而不完整牙根的继承性牙齿取代它的位置。由于这种更替循环，人们发现，在一定限度内，在任何给定的时间，功能性牙齿的形状和状况都与其下面的继承者的大小和状况有关。
对24个不同大小的头骨进行的各种测量表明，在鳄鱼一生的大部分时间里，牙齿都有规律地不断更换。据估计，在一条13英尺长的鳄鱼身上，每颗牙齿可能被替换了45次。
The history and replacement of crocodile teeth are described. A new tooth erupts with only a short root which grows downwards into the socket as the pulp cavity in the crown begins to be occluded by the further deposition of dentine. After the root has become fully extended, it is gradually resorbed at its base to make room for an enlarging successional tooth which has been forming on the lingual side of the socket. The successional tooth eventually moves to a position within the partly resorbed functional root and directly under the functional crown. Progressive reduction of the functional root now occurs to accommodate the continuously enlarging successional tooth and, when resorption is largely complete, the functional tooth falls away, allowing the successional tooth, with a short, incomplete root, to take its place. As a result of this successional cycle it is found, within certain limits, that at any given time the form and condition of a functional tooth is related to the size and condition of its successor lying below.
Consideration of various measurements made on a series of twenty-four skulls of different sizes indicates that a regular and continuous replacement of teeth occurs throughout a large part of a crocodile's life. It is estimated that in a crocodile which is thirteen feet long, each tooth is likely to have been replaced forty-five times.