Frankfort Horizontal Occlusal Plane
Typically, the Frankfort plane (superior border of the external auditory meatus to the infraorbital rim) or plane of occlusion (vertical/up-down plane) is positioned parallel to the floor in panoramic imaging. The Tragal-canthus plane (tab in ear to outer corner of the eye), and the Ala-tragus (corner of nose to tab in the ear) plane are used to align the vertical position of the head as well. Some machines provide a horizontal alignment light to help assess the proper vertical position of the head. The patient’s forehead and chin should be in the same vertical plane.
Figure 16. Frankfort and Occlusal Plane.