What is a cause of relapse of tooth rotation in the shaft?

• A. Tension of the periodontal ligament fibers surrounding the tooth
• B. Lack of occlusal stop
• C. Lack of posterior occlusal plane
• D. Lack of anterior occlusal plane

Answer: (A)

The restoring tendency of rotated teeth comes from the elastic memory of the periodontal ligament around the tooth. When you rotate a tooth, the fibers on the compressed side become stressed and those on the stretched side are pulled taut. Once the appliance is removed, these fibers recoil toward their original orientation, pulling the tooth back and causing relapse of the rotation. Occlusal issues can influence stability, but they don’t drive the rotation relapse as directly as the PDL’s elastic recoil.