An analysis of the variation of the ANB angle: a statistical appraisal.

The variation of the ANB angle was studied in a sample which consisted of 138 orthodontically untreated children 7 to 15 years of age with Class I, Class II, or Class III (Angle) malocclusion. A regression analysis was used in order to describe the proportion of the distorting variation caused by some usual changes in the cranial and facial skeleton. The results revealed that a part of the variation of the ANB angle could be attributed to factors other than the actual apical base difference, among these factors being the rotation of the S-N plane, the relative length of the S-N plane, and the rotation of the jaws. Because the ANB angle can vary without any marked abnormalities in the sagittal jaw relationship, the use of the so-called normal limits for the ANB angle is not justified. It would be better to replace the ANB angle with a more accurate indicator.