The bridge abutment teeth should have sufficient clinical length, a more normal tissue structure and a large volume to ensure a good retention of fixed teeth.
1. Ante's rule: the periodontal membrane area of the abutment tooth is greater than or equal to the total area of the missing periodontal membrane.
2. Crown-to-root ratio: 2:3 in ideal situations, at least 1:1.
3. Tooth root shape and structure: the relative support force of long and thick root and large root interval is better.
4. Tilt and shift of abutment teeth: The inclination of abutment teeth generally does not exceed 25 degrees.