A study of the zone of sharpness of three panoramic x-ray machines and the effect of screen speed on the sharpness zone.

Sharpness zones of the Orthopantomograph-5, Autopan, and Panorex were delineated with the use of a standard multiline test object at 1.7 line pairs per millimeter. In addition, Panorex zones made with medium- and high-speed screens were compared. The focal troughs of all machines covered most tooth positions. The Autopan and Orthopantomograph troughs were narrow anteriorly, while the Panorex trough was not close to the condyle posteriorly. There was little difference between focal troughs produced with the use of high- and medium-speed screens.