In recent years, methods have been developed that calculate three-dimensional (3D) co-ordinates of orthodontic landmarks from lateral and frontal cephalograms. However, precise measurement has been impossible with these methods because, although they corrected the magnification of the image, they did not correct 3D cephalic malpositioning that occurs during the measurement of human subjects. In this study, we developed a 3D cephalometric system that corrected not only for magnification of the image, but also 3D cephalic malpositioning during cephalogram exposure. Magnification of the image was corrected for first. Cephalic revolution was then sequentially corrected and divided into elements of x-, y-, and z-axes. The origin was parallelly translated to the mid-point of bilateral porion. In order to examine the accuracy of this system, seven human dry skulls were measured. The accuracy unaffected by the cephalic revolution in any direction and standard errors was within 0.8 mm in any orthodontic landmarks. It was suggested that this measurement system would have sufficient accuracy for clinical application. The results indicated that precise cephalometric measurement was possible with this system and it was suggested that its clinical application would be possible.
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