The opening phase of jaw movement is associated with which disc movement?

• A. Disc retraction
• B. No disc movement
• C. Disc advancement
• D. Disc rotation

Answer: (C)

During the opening phase, the jaw mainly translates forward, with the condyle and the articular disc gliding anteriorly as a unit. This forward glide of the disc relative to the fossa is called disc advancement, and it allows the mandible to open smoothly under the articular eminence. The anterior movement is facilitated by the lateral pterygoid pulling the disc forward, maintaining proper articulation in the superior joint space. The other movements aren’t characteristic of the opening phase: retraction would be a backward shift, rotation isn’t the primary movement during the initial opening, and there is indeed disc movement to accommodate the forward glide.