# Reference Planes for Model Adjustment

The working models (maxilla and mandible) have to be adjusted in the articulators so that the movement paths of the device are congruent with the occlusal guidance paths of the rows of teeth being depicted.

It must therefore be possible to transfer to the articulator the geometric reference points and planes of the skull or masticatory system as well as their spatial relationships to the dentition. The reference planes are the Camper plane, the hinge-axis orbital plane, and the midface horizontal plane, and each plane has corresponding reference points (Fig 8-2). The reference planes are used not only for arbitrary (average-value) methods but also for individual, custom measurements.

The Camper plane runs from the superior edges of the outer orifices of the ears to the subnasal point and, in articulators, lies parallel to the upper and lower arm (Fig 8-3a); the occlusal plane lies midway between the model holders parallel to the Camper plane.The models are aligned with the occlusal plane and then lie parallel to the table plane. Even when joint-related adjustment of the models is carried out using individual transfer methods, the occlusal plane as a parallel to the Camper plane is the reference plane for reconstruction of the occlusal field.

The hinge-axis orbital plane runs from the hinge-axis point to the main orbital point and, in the appropriate articulators, also lies parallel to the upper and lower arms.The occlusal plane and hence the models are inclined at an individual angle (approximately 10 to 20 degrees) (Fig 8-3b). In addition to the hinge-axis orbital plane, the Frankfort plane and the auriculo-infraorbital plane are used as corresponding reference planes.

The midface horizontal plane or patient horizontal plane lies between the hinge-axis orbital plane and the Camper plane. It is referenced on the articulator and runs through the hinge-axis points and a reference point approximately 43 mm above the mandibular incisal point (Fig 8-3c).