Peterka M, Vonesch J L, Ruch J V, Cam Y, Peterková R, Lesot H
Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, Prague.
J Craniofac Genet Dev Biol. 2000 Jan-Mar;20(1):35-43.
The secondary palate formation in mouse has been associated with the period of fast growth of the mandible from embryonic days (ED) 13.0 to 16.0. During that time, the incisors and first molars develop from the bud to the bell stage. We investigated the position and growth of the tooth during prenatal elongation of the lower and upper jaws, and searched for the developmental stage when alignment of opposing teeth was achieved. Computer-aided 3D representations allowed us to represent the position of incisors and molars in the embryonic head from ED 13.5 to 18.0 on the basis of data obtained from histological sections. The atlas-hypophysis connection exhibited minimum change in length and orientation during the prenatal period, and thus was used as a reference line. The length of the teeth was calculated from 3D data. The upper first and second molars were longer than the lower ones. When viewed from the upper side, the upper and lower molar primordia were parallel from ED 13.5 to 15.0. During this period, the upper molars had a more lateral position than the lower ones. This situation was maintained in the anterior extremity of the first molars at later stages, while the posterior part of the upper and lower molar epithelia reached opposition in the medio-lateral direction from ED 16.0. The lower incisors exhibited an apparently backward position when compared to the upper incisors at earlier stages. However, the distance between the prospective anterior tips of the opposing incisors gradually decreased. The part of Meckel's cartilage associated with the lower dental quadrant elongated more than 3-fold from ED 13.5 to 18.0, and the lower jaw grew faster than the upper one. This difference resulted from the fast growth of the lower diastema from ED 14.0 to 18.0. The different growth speeds of the upper and lower jaws did not change the relative antero-posterior adjustment of the upper and lower molars, but contributed to achieving the opposition of the gnawing ends of the incisors.
小鼠次生腭的形成与下颌骨从胚胎期（ED）13.0至16.0的快速生长阶段相关。在此期间，门牙和第一磨牙从芽期发育至钟状期。我们研究了上下颌在产前伸长过程中牙齿的位置和生长情况，并寻找相对牙齿对齐时的发育阶段。计算机辅助3D模型使我们能够根据组织学切片获得的数据，呈现ED 13.5至18.0胚胎头部中门牙和磨牙的位置。寰椎 - 垂体连接在产前期间长度和方向变化最小，因此用作参考线。牙齿长度由3D数据计算得出。上颌第一和第二磨牙比下颌的长。从上方观察时，ED 13.5至15.0期间上颌和下颌磨牙原基相互平行。在此期间，上颌磨牙比下颌磨牙位置更靠外侧。这种情况在后期第一磨牙的前端得以保持，而上颌和下颌磨牙上皮的后部从ED 16.0开始在内外侧方向上相对。早期阶段，与上门牙相比，下门牙位置明显靠后。然而，相对门牙预期前端之间的距离逐渐减小。与下颌牙象限相关的Meckel软骨部分从ED 13.5至18.0伸长超过3倍，下颌生长比上颌快。这种差异源于ED 14.0至18.0期间下颌牙间隙的快速生长。上下颌不同的生长速度并未改变上下磨牙相对的前后调整，但有助于实现门牙啃咬端的相对。
