Dean M Christopher
Department of Cell and Developmental Biology, University College London, London, UK.
Methods Mol Biol. 2012;915:89-100. doi: 10.1007/978-1-61779-977-8_5.
Teeth contain an incremental record of their growth in the form of periodic growth markings that are literally embodied within the structure of enamel. These can be revealed when ground sections of teeth are prepared for transmitted light microscopy. This chapter sets out one method for estimating the time taken to form the crowns of permanent teeth. First, the daily rates of enamel formation are estimated at three positions within the crown close to the enamel dentine junction (EDJ). Then a 200 μm length along an enamel prism that take ∼80 days to form is followed out from the EDJ at the dentine horn. From this point a line is then tracked back along the direction of the oblique striae of Retzius that are contained within enamel to a lower position further along the EDJ. This procedure is repeated until the cervix of the tooth is reached. The total time for enamel formation is estimated by summing the number of 80 day segments traced out.
牙齿以周期性生长标记的形式包含其生长的递增记录，这些标记实际上体现在牙釉质的结构中。当制备牙齿磨片用于透射光显微镜观察时，这些标记就可以显现出来。本章阐述了一种估算恒牙牙冠形成所需时间的方法。首先，在牙冠内靠近牙釉质牙本质界（EDJ）的三个位置估算牙釉质形成的每日速率。然后，从牙本质角处的EDJ沿着一条大约需要80天形成的牙釉质棱柱追踪200μm的长度。从这一点开始，沿着牙釉质中包含的雷丘斯斜纹的方向向EDJ上更低的位置回溯一条线。重复这个过程，直到到达牙齿的颈部。通过将追踪出的80天时间段的数量相加来估算牙釉质形成的总时间。
