Fig. 4From: The crown-root morphology of central incisors in different skeletal malocclusions assessed with cone-beam computed tomographya The Collum angle is formed by the extension of the long axis of the crown and the long axis of the root. b Tangent L passes through upper and lower intersections of labial surface of crown and circle with the T center and radius of 0.5 mm. c The measuring example of Collum angle and labial surface angleBack to article page