Effective condylar growth and chin position changes in activator treatment: a cephalometric roentgenographic study

Effective condylar growth (a summation of condylar remodeling, glenoid fossa remodeling, and condylar position changes within the fossa) and its influence on the position of the chin was analyzed in 40 class II, division I malocclusions treated successfully with activators. Additionally, the amount of mandibular rotation was assessed. Lateral head films in habitual occlusion from before and after an average treatment period of 2.6 years were evaluated. The Bolton Standards (32 untreated individuals with ideal occlusion) served as controls. Two different treatment effects were evaluated: overall growth change and treatment effects (overall growth changes minus age-related Bolton values). In comparison with the Bolton group, the activator patients exhibited an increase in the amount of vertical effective condylar growth (3.0 mm; P < .001), a decrease in the amount of sagittal effective condylar growth (0.6 mm; P < .05), and an increase in the amount of vertical development of the chin (1.8 mm; P < .001). No group differences could be found for sagittal development of the chin. In the Bolton group, the mandible rotated posteriorly, and in the activator group it rotated anteriorly (2.7 degrees; P < .001). The present investigation revealed that effective condylar growth can be increased and the chin position can be changed by activator treatment. Thus activator treatment induces skeletal changes, although not always in the desired (sagittal) therapeutic direction.