What occurs during the first phase of jaw opening?

What occurs during the first phase of jaw opening?

• A. Anterior translation
• B. Condylar rotation
• C. Lateral excursion
• D. Posterior glide

Answer: (B)

Opening the jaw starts with a hinge-like rotation of the mandibular condyles within the glenoid fossa, mainly in the inferior joint space. This rotation lowers the jaw without much forward sliding, so the first phase is essentially a rotational (hinge) movement. As opening continues, the condyle-disc complex then translates anteriorly along the articular eminence to achieve greater mouth opening. Lateral excursion is a side-to-side motion and isn’t part of the initial opening, and posterior glide describes backward movement that isn’t the primary mechanism of the first phase.

Opening the jaw starts with a hinge-like rotation of the mandibular condyles within the glenoid fossa, mainly in the inferior joint space. This rotation lowers the jaw without much forward sliding, so the first phase is essentially a rotational (hinge) movement. As opening continues, the condyle-disc complex then translates anteriorly along the articular eminence to achieve greater mouth opening. Lateral excursion is a side-to-side motion and isn’t part of the initial opening, and posterior glide describes backward movement that isn’t the primary mechanism of the first phase.