Final answer:
The two portions of teeth that can be divided into thirds are the roots and the crown, with the divisions used to describe locations for dental treatment and assessment.
Step-by-step explanation:
The two portions of teeth that can be divided into thirds are the roots and the crown. The roots are the parts of the tooth that are embedded in the bone of the jaw and provide support. The crown is the visible part of the tooth that is above the gum line and includes the enamel-covered top of the tooth.
More specifically, the crown can be divided into three parts: the incisal or biting edge, the middle third, and the cervical third near the gum line. Similarly, the root is often divided into thirds for clinical and anatomical discussion: the cervical third closest to the crown, the middle third, and the apical third nearest to the tip of the root.
This division into thirds helps dental professionals describe locations for treatment and assessment. While these divisions are more conceptual and used for description, they provide a systematic approach to discussing and treating dental conditions effectively.