Which periodontal fibers cause problems once orthodontic treatment is completed and the tooth gets back-rotated?

Correct answer: D. Transeptal fibers

• A. Apical fibers anchor the apex of the root to the bone at the fundus of the socket — they are not responsible for rotational relapse.
• B. Oblique fibers are the most numerous PDL fibers and resist vertical occlusal forces — they do not cause rotational relapse.
• C. Gingival fibers in general play a role in relapse, but the SPECIFIC fiber type responsible for rotational relapse is the transeptal fibers.
• D. TRANSEPTAL fibers (a subdivision of gingival fibers that run from the cementum of one tooth to the cementum of the adjacent tooth, crossing the interdental septum) are responsible for RELAPSE of rotated teeth after orthodontic treatment. These fibers 'remember' the original tooth position and exert elastic recoil forces that rotate the teeth back. This is why overcorrection of rotations and extended retention are critical.