An improved method for the assessment of the sagittal skeletal pattern and its correlation to previous methods

The true horizontal with the head in natural posture is a less variable reference plane than conventional intracranial planes. Variables based on natural head posture have the further advantage that they better describe true life appearance. All current assessments of the sagittal skeletal pattern have known inherent errors, especially in subjects with facial patterns which deviate markedly from the average. A new variable for the assessment of the sagittal skeletal pattern, the angle between the AB line and the true horizontal, has been evaluated in a large study involving both Caucasians (British n = 80) and non-Caucasians (Chinese n = 240). It was found to be simple and clinically practical. A suggested range of 12° to 18° for a Class I skeletal pattern was established, based on the normal Caucasian distribution of the ANB angle. The AB/Hor angle was compared with a ‘corrected’ ANB angle, the Wits angular appraisal and the angle between the AB line and the occlusal plane. The coefficients of correlation ranged from 0.5 to 0.7. It was concluded that the new AB/Hor variable functioned as a fundamentally different variable and not as a minor variation of conventional measures. It eliminates the problems associated with the use of nasion and of the functional occlusal plane.