Effects on occlusion and condylar position of clinical hinge axis localization of models mounted in the articulator

A real or virtual articulator is used for the analysis and reconstruction of the occlusion. The joint-related transfer from the clinical situation to the articulator is mostly performed with a facebow transfer. This is not based on a dynamically determined hinge axis but on nearby anatomical landmarks. The axis misalignment caused by this procedure unavoidably leads to an occlusion error in the case of a change in height in the articulator. When correcting the occlusion, the jaw relation is determined in the centric condylar position. This requires a bite-elevating centric relation record, and generally necessitates a change in height in the articulator when lowering the support pin to achieve contact. The error can be disregarded only if the deviation of the 'arbitrary axis' determined by the facebow transfer from the hinge axis of the patient happens to be very small. The repercussions of this problem have mostly been underestimated because no simple procedure has been available to date to calculate the occlusal and condylar deviation. For the first time, with the aid of the didactic Dyna-Sim-Axis software, the cause and effect of this complex problem can be explained in a way that can be grasped more easily and intuitively. Keywords: hinge axis, centric hinge axis, axis error, arbitrary axis, mounting the model, jaw relation, centric bite record, centric relation, centric relation record, facebow, locked jaw