Which statement best describes hinge/rotational movement in jaw motion?

• A. It occurs after 25 mm of opening
• B. It is the initial phase of opening
• C. It is the same as translational movement
• D. It occurs only during maximum intercuspation

Answer: (A)

Hinge/rotational movement is the mandible turning around the condyles during the opening phase. This pure rotation happens in the early portion of opening, roughly the first 20–25 mm of vertical opening, before the condyles start translating forward on the articular eminence. Once that initial phase is done, the movement shifts to translational (gliding) as the condyles glide forward. So the best description is that hinge movement occurs in the initial phase of opening, not after a fixed 25 mm threshold or only at maximum intercuspation.