The position of the upper occlusal rim in the articulator is accurately determined by using a facebow because it records the spatial relationship of the maxillary arch to the temporomandibular joint (TMJ). This transfer allows the maxillary cast to be mounted in the articulator in the same anatomical position as in the patient’s skull, ensuring proper occlusion and function. Facebow use improves accuracy in jaw relation records and facilitates better denture fabrication by replicating the true hinge axis and occlusal plane orientation. This precision cannot be achieved by vertical dimension measurement, wax rims alone, or hand articulation.

Reference: Prosthodontics: Principles and Management Strategies, Deepak Nallaswamy, 3rd Edition.