Mechanics, growth, and class II corrections.

Growth of the orofacial region is quantitatively described by locating the center of mandibular rotation relative to the cranial base. The center of mandibular rotation is positioned by the ratio of vertical facial growth (AFH/PFH) and the direction of condylar growth. Appliance therapy is associated with changes in the means of both of these parameters. These changes reduce or stop favorable anterior mandibular rotation and redirect the mean condylar growth vector more posteriorly. When appliance therapy is stopped, these parameters return toward their resting values. The mean direction of the condylar growth vector became even more anteriorly directed after treatment than the pretreatment mean value. These data support the hypothesis that orthodontic appliances significantly alter the facial growth pattern and when they are stopped, the growth pattern tends to rebound to or beyond the pretreatment values.