Journal of Dental Medicine

Facial prognathism, which is a problem in some orthodontic patients, is characterized by a number of cephalometric changes. Most clinicians use SNA angle in lateral cephalometric analysis to evaluate the amount of maxillary prognathism. Since SNA angle is not a reliable measurement for maxillary prognathism, and taking into account that the amount of prognathism changes in relation to cranial anatomy, according to Bjork it's better to measure the facial prognathism by the angle between anterior and posterior cranial base. According, two angles are recommended NSBa and NSAr.In this study 80 lateral cephalograms from three malocclusion groups, were studied and the amount of maxillary prognathism in relation to SNA and NSAr angles and their relationship to each other were measured.

The results were as follows:
1- Studying facial prognathism in relation to SNA and NSAr angles it was found that SNA angle is influenced by cranial base shape
2- The mean value of anterior and posterior cranial bases didn't show significant differences.
3- The mean value of SNA angle didn't show significant statistical difference in various malocclusion groups.
4- The correlation coefficient of ANB angle and wit's measurement is low.