The effect of changes in head position on enlargement of structures during panoramic radiography

Accuracy of panoramic radiographs is essential for distance measurements during implant planning, but it might be compromised by various factors. The aim of the present study was to evaluate the effect of vertical and horizontal head positioning on area-dependent enlargement ratios of digital panoramic radiography.

The mandible of a dry skull was marked with small steel globes. The skull was moved 1 to 4 degrees in 1-degree increments to the left and right and up and down. A series of 17 panoramic radiographs was obtained with the same digital radiographic device. For the rotated skull, horizontal and vertical distances, indicated by the steel globes, were compared to the distances with the ideal positioning of the skull. The results were analyzed statistically.

Head positioning and angulation, anatomical site, and distance orientation influenced horizontal measurements. Enlargement ratios of horizontal distances of the right canine and first molar regions (skull rotation to the right 2 to 4 degrees) were significantly lower than those for the corresponding anatomical sites on the left side. Horizontal distance measurements of the different anatomical sites of the left and the right jaw did not differ significantly from each other when the skull was moved downward. When the skull was rotated upward, no significant differences were obtained for corresponding anatomical sites of the right and left arches. Enlargement ratios of vertical distances of different anatomical sites, as well as within the same anatomical site, were not significantly different from each other for the given skull rotations.

Ideal head positioning for digital panoramic radiographs is mandatory to avoid improper enlargement ratios of horizontal distances, which can be important in implant dentistry.