Fig. (6) Lower incisor position change. Mandibular tracings super-imposed on anterior contour, internal cortical surface of the sym-physis and mandibular canal. Pretreatment (black line), posttreat-ment (red line)m The mesiobuccal cusp tip of the mandibular permanent first molarit The incisal tip of the most prominent mandibular central incisorii The incisal apex of the most prominent mandibular central incisorOL Occlusal line, a line through m and the buccal cusp tip of the mandibular first premolarOLP Occlusal line perpendiculare, a line perpendicular to OL through the most anterior point of the bony chin symphysis