The first 20-25 mm of mouth opening corresponds to which movement?

The first 20-25 mm of mouth opening corresponds to which movement?

• A. Depression
• B. Hinge/Rotational Movement
• C. Translational Movement
• D. Elevation

Answer: (A)

Opening the mouth begins with a hinge-like rotation of the mandible around a horizontal axis through the condyles. This rotational phase accounts for roughly the first 20–25 mm of opening. After this initial rotation, further opening involves translational movement, where the condyle-disc complex slides forward along the articular eminence. So the first 20–25 mm corresponds to hinge/rotational movement. Depression describes the overall downward movement that creates opening, but the specific early phase is rotation, not just a simple vertical drop. Elevation would close the mouth, not open it.

Opening the mouth begins with a hinge-like rotation of the mandible around a horizontal axis through the condyles. This rotational phase accounts for roughly the first 20–25 mm of opening. After this initial rotation, further opening involves translational movement, where the condyle-disc complex slides forward along the articular eminence. So the first 20–25 mm corresponds to hinge/rotational movement. Depression describes the overall downward movement that creates opening, but the specific early phase is rotation, not just a simple vertical drop. Elevation would close the mouth, not open it.