Cephalometric reference planes and measurements. Yellow, vertical reference line (vert T); Blue, (a) S-N (b) U1-SN (c) mandibular plane (d) IMPA; Red, (1) U1 apex (2) L1 tip (3) U1 tip (4) L1 apex. Incisal movements were quantified by measuring the horizontal distance from incisor tip and apex to vert T, which is Nasion perpendicular line.