Face bow and Hinge axis

Literature abounds with studies, concepts, controversies, discussions and recommendations concerning hinge axis. If the maxillary cast is positioned without the correct maxillae hinge axis relationship, arcs of movement in the articulator will differ from those of the patient. Like centric relation, hinge axis is stable, reproducible and repeatable. Therefore, it is used as an important reference in mounting casts on articulator so that, opening axis on articulator coincides with the terminal hinge axis. Since the hinge axis is a definite fixed component of every closing position of the mandible, it is necessary to reproduce it on the appropriate instrument. Verification of the mandibular cast position by using inter occlusal records made at increased vertical dimension of occlusion will be difficult or impossible unless subsequent records are of the same thickness. Also an occlusion that is restored to an incorrect arc of closure may have interceptive and deflective tooth contacts in the closing movement. The mounting of maxillary casts is considered important due to the influence of this step, on the arc of closure and eventual occlusal errors.