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 molar

it   The incisal tip of the most prominent mandibular central incisor

ii   The incisal apex of the most prominent mandibular central incisor

OL   Occlusal line, a line through m and the buccal cusp tip of the mandibular first premolar

OLP   Occlusal line perpendiculare, a line perpendicular to OL through the most anterior point of the bony chin symphysis