Advanced Dental Admission Test (ADAT)

What occurs at the frontal axis of rotation during mouth opening?

1. Both condyles move posteriorly

2. One condyle moves anteriorly, the other remains in RCP

3. Both condyles remain in RCP

4. One condyle drops while the other rises

The correct answer is: One condyle moves anteriorly, the other remains in RCP

During mouth opening, the movement around the frontal axis of rotation primarily involves the relationship between the two condyles of the mandible and their positions in the glenoid fossae. The correct answer indicates that one condyle moves anteriorly, while the other remains in an initial reference position known as the retruded contact position (RCP). This is significant because during the opening of the mouth, the mandible rotates around the frontal axis, which allows for this differential movement of the condyles. Specifically, the condyle that moves anteriorly is doing so to accommodate the downward and forward path of the mandible, while the other condyle maintains its position in RCP. This distinct motion is essential in creating the balance and asymmetry necessary for effective opening movements, ensuring that the mandible can articulate properly with the maxilla. The positions of the condyles during this motion affect the kinematics of the temporomandibular joint (TMJ), which is crucial for oral function. Understanding this motion helps in diagnosing and treating various temporomandibular disorders and optimizing occlusal relationships. In summary, the correct answer reflects the complex biomechanics of jaw movement where one condyle advances while the other stays steady, highlighting the dynamic nature of the opening