The facebow record is used for all of the following EXCEPT:

Correct answer: D. Determining the dental midline

• A. IS a function. The facebow relates the maxillary arch to a chosen horizontal reference plane, usually Frankfort or Camper's plane.
• B. IS a function. The facebow records the relationship of the maxilla to the transverse horizontal axis of the condyles, which is precisely what allows accurate simulation of the opening arc.
• C. IS a function. This is the whole point of the instrument: transferring the maxillary cast to the articulator so that its position mirrors the patient's.
• D. CORRECT — this is the EXCEPTION. The facebow has nothing to do with the DENTAL MIDLINE. Midline is determined clinically from facial landmarks — the philtrum, nasion, and interpupillary line — and is recorded during try-in and tooth arrangement, not by an instrument that records arch-to-skull orientation.

Note: Without a facebow, the maxillary cast is mounted on an arbitrary axis, and errors in the arc of closure translate into occlusal errors that grow with the amount of vertical opening — most consequential in full-mouth rehabilitation.