ABSTRACT

“The SUM of Posterior Angles” in Björk’s Polygon is being used for predicting the patients growth direction. The angle between Mandibular Plane and SN is also used for similar purpose. Geometrically there is a direct relationship between the sum of posterior angles and the mandibular plane angle presented as; SUM=360°+SNGoMe. The SUM only changes as much as mandibular plane angle changes. Therefore in case of SNGoMe measurement is available, the sum of posterior angles is unnecessary and invalid in predicting the growth direction.