The variation in appearance of the hard palate and the nasal floor in rotational panoramic radiography.

This study was performed to find the origin of the radiopacity in the region of the hard palate and to explain the variability in appearance of this radiopacity in panoramic radiographs. It could be demonstrated, with the use of metal markers attached to a dry human skull, that the radiopacities seen in the region of the hard palate represent the junction of the nasal septum and the hard palate and the junction of the maxillary sinus to the hard palate. The appearance of one or two lines depends on the angulation of the skull. A more inclined (chin-down) position of the skull produces two lines, whereas a chin-up position results in a superimposition of the two lines and produces only one line. The image of the junction of the bony septum and palate is unsharp because of the greater distance from the focal plane. The junction of the maxillary sinus to the hard palate is closer to the image layer and will appear as a sharp line.