A method for integrating facial cephalometry and corrected lateral tomography of the temporomandibular joint

Objectives: To test the validity of an indirect method for obtaining the Frankfort horizontal (FH) plane and transferring it from the originating cephalogram to a tomogram. Methods: One hundred and fifty-two corrected lateral tomograms from 38 individuals, taken before and after treatment, were used for this study. The tomograms were scanned and digitized. The angle between the FH plane and the long axis of the pterygopalatine fossa was measured on the reciprocal cephalograms. In addition, a tangent was drawn at the uppermost point of the glenoid fossa and parallel to the upper border of the film. Common variables regarding these two planes were measured and compared. Results: It was found that the tangent to the fossa roof, parallel to the superior border of the film, did not coincide with the transferred cephalometric FH plane. Statistically significant differences were found between all variables for the two groups. Conclusions: In cases where integration of cephalometric and tomographic measurements are needed, the drawing of a tangent on the roof of the fossa is not a reliable method.