Starting from centric relation, in which direction does the mandible travel during a protrusive movement?

Correct answer: B. Downward and forward

• A. Downward and backward is not anatomically possible from centric relation; the condyle is already in its most superior-anterior seated position against the eminence, and the posterior wall blocks retrusion.
• B. CORRECT. In protrusion the condyle translates DOWN the posterior slope of the articular eminence and FORWARD. Because the eminence slopes downward and forward, the mandible necessarily moves downward and forward — this is what produces posterior disclusion when anterior guidance is adequate (Christensen's phenomenon creates the posterior space).
• C. Upward and forward would require the condyle to climb above the eminence, which does not occur in normal function.
• D. Purely horizontal translation would require a flat eminence; the eminence has a defined inclination that forces vertical descent.

Note: Steeper eminence = more posterior disclusion in protrusion. This drives cusp height and incisal guidance decisions.