Tooth anatomy The three equal divisions of teeth are easy to describe. The axial surface of the tooth is often divided into three equal parts in one direction, one of which is called 1/3.
Such as in the vertical direction of the crown can be divided into incisor (occlusion) 1/3, 1/3 and 1/3 of the neck;
The root can be divided into cervical 1/3, middle 1/3 and apical 1/3.
In the meso-distal direction, the crowns can be divided into meso-1/3, meso-1/3 and meso-1/3.
In the direction of the lip (buccal) and tongue, the adjacent surface of the tooth crown is divided into lip (buccal) 1/3, middle 1/3 and tongue 1/3.