Hinge axis and Facebow

To secure a centric inter-occlusal record, we attempt to freeze the terminal hinge closure at a convenient vertical opening. Without the hinge axis, we would be unable to secure an accurate centric inter-occlusal record. Cohen stated that once the hinge-axis points had been located and marked permanently it was never necessary to repeat the procedure since the anatomic structures they represented never changed during life.The transverse axis of rotation can be located by use of an instrument called the
Face-Bow. Facebow is a caliper-like instrument used to record the spatial relationship of the maxillary arch to some anatomic reference point or points and then transfer the relationship to the articulator. The two main types of facebow is the kinematic and arbitrary type. The arbitrary type is commonly used in clinical practice and is again of two types: earpiece and fascia type.