SD大鼠牙列的显微CT观测

The morphology of dentitions of SD rats observed by Micro-CT

目的:研究SD大鼠牙齿的解剖特点。方法:取39只不同鼠龄的SD大鼠的牙列进行显微CT扫描及三维重建,观测牙齿内、外部的解剖结构及生长发育过程中的形态学变化。结果:大鼠切牙高度弯曲,与一段圆弧完全拟合;上切牙比下切牙平均弯曲半径更小(7.01 mm比12.93 mm),长度更短(25.04 mm比27.71 mm)。上颌第一磨牙通常有8个牙尖、5个牙根;下颌第一磨牙通常有7个牙尖、4个牙根。第二、三磨牙与第一磨牙相比,牙尖及牙根数逐渐减少,体积减小;下颌第一、二磨牙远中根为扁根,多为1-2型根管,其余牙根多为单根管。第二、三磨牙存在牙根数目变异。第一、二、三磨牙牙冠发育完成的时间依次为2、3、4周龄,牙根发育完成的时间依次为8、8、10周龄。结论:SD大鼠不同牙位的牙冠及牙根具有不同的形态学特征,第二、三磨牙存在牙根数目变异。

Objective: To investigate the dental anatomy of SD rats. Methods: The dentitions of 39 SD rats with different age were scanned by a micro-CT scanner. After 3 D reconstruction, the internal and external anatomy of the teeth was examined, and the morphological changes of teeth during different development stages were assessed. Results: The upper incisors were more curved(mean radius: 7.01 mm vs. 12.93 mm) and shorter(mean tooth length: 25.04 mm vs. 27.71 mm) than the lower incisors. The upper first molars commonly exhibited 8 cusps and 5 roots, while the lower counterpart exhibited 7 cusps and 4 roots. The 2 nd and 3 rd molars exhibited decreased number of cusps and roots, and decreased dimensions. The distal roots of the mandibular 1 st and 2 nd molars were flat and always displayed a type 1-2 canal, and all the other roots commonly had a single canal. For the 1 st, 2 nd and 3 rd molars, the development of the crown was completed at the age of 2, 3 and 4 weeks, respectively;and the development of the root apex completed at the age of 8, 8 and 10 weeks, respectively. Conclusion: The morphological features of the crown and roots were quite different from the tooth type of SD rats, and root number variations can be detected in the 2 nd and 3 rd molars.