Errors in oblique cephalometric radiographic projections of the edentulous mandible. Part I: Geometric errors.

Geometric errors that occur in oblique cephalometric radiographic projections of the edentulous mandible were calculated for different focal-spot-to-object distances (1500, 3000, and 6000 mm). The horizontal errors from tolerance of the porion and nasion fixation in the cephalostat were calculated. The same was done for the vertical errors caused by the variability of the rest position. From the results of this study it can be concluded that the distance between focal spot and object should be as large as possible. It was also found that it is important to minimize the differences in enlargement that may occur on radiograms of different subjects because of changes in the position of the mandible. This position can be standardized by the use of an individual support.