Relation of the SNA angle to the saddle angle.

The degree of the individual facial prognathism, considering the relationship between the SNA and NSAr angles, was studied in a sample of forty-two children with Class I (Angle) malocclusion. A definite relationship was found between the NSAr and SNA angles. When the NSAr angle was large, the SNA angle was relatively small; on the contrary, when the NSAr angle was small, the SNA angle was significantly large. The conclusion was drawn that in persons with Class I malocclusion, a marked part of the variation of the SNA angle is to be explained by the variation of the NSAr angle. Since the value of the SNA angle can be affected by the configuration of the cranial base, it should be used with caution, especially if the value of the NSAr angle is abnormal.