Age effects on orthodontic treatment: skeletodental assessments from the Johnston analysis

We have compared differences in treatment outcomes dependent on patient age, either adolescent (means = 12.5 years at start) or adult (means = 27.6). Subjects were female patients whose Class II, Division 1 malocclusions were treated with Tweed edgewise mechanics and four-premolar extractions. Cephalometric records were assessed according to the Johnston analysis. The functional occlusal plane remained stable during mechanotherapy in the adolescents, whereas it steepened considerably in the adults. Differential mandibular growth in adolescents contributed 70% of the total molar correction, with orthodontic tooth movement accounting for the other 30%. Maxillary growth in the adults detracted from the Class II molar correction; tooth movement accounted for virtually all of the correction.