Figure 4-6. Axial surface of a tooth.
4-8.
DIVISION OF TEETH
To simplify the description of the surface anatomy of teeth, the crown and roots
are divided into imaginary thirds. Each axial surface of the crown is divided into both
vertical and horizontal thirds. The root is divided into horizontal thirds only. See figure
4-7.
a. Each crown is divided into horizontal thirds--occlusal (or incisal), middle, and
cervical (or gingival).
b. Each mesial and distal surface of the crown is divided into vertical thirds--
facial, middle, and lingual.
c. Each facial and lingual surface of the crown is divided into vertical thirds--
mesial, middle, and distal.
d. Each root is divided into horizontal thirds--cervical, middle, and apical.
MD0501
4-9