牙冠
Corona dentis
定义
每颗牙齿由三个部分组成：牙冠，突出于牙龈之上；牙根，嵌入牙槽内；以及牙颈，即位于牙冠与牙根之间的缩窄部分。
參考資料
This definition incorporates text from a public domain edition of Gray's Anatomy (20th U.S. edition of Gray's Anatomy of the Human Body, published in 1918 – from http://www.bartleby.com/107/).
