Introduction
An articulator is a mechanical device that holds the casts of the patient's jaws and copies the movements of the mandible. It mechanically reproduces the paths of the TMJs, the posterior determinants, so that crowns, bridges and dentures can be built to fit those movements before they reach the mouth.
Border movements are limited by ligaments and repeat reliably, which is why they can be set on the mechanical fossae of an instrument. The better an articulator copies them, the less adjustment the restoration needs in the mouth.
Getting the casts in the right place
For the casts to close on the right arc, they must sit at the same distance from the hinge as the patient's teeth sit from the condyles. The facebow records three points, the transverse hinge axis on both sides and a third reference point on the face, and transfers the position of the upper teeth to the articulator. The lower cast is then mounted against it with an interocclusal (bite) record.