Skeletal Class II patterns in the primary dentition.

The aim of this longitudinal cephalometric study was to investigate early characteristics of favorable and unfavorable growth. Two groups of untreated subjects with skeletal Class II pattern were formed on the basis of an ANB angle at least 2.5 degrees above the individual norm, according to Järvinen, at age 5. The subjects were followed longitudinally until age 12. The favorable growth group (n = 13) consisted of subjects who exhibited a decrease in the individualized ANB angle of at least 1.5 degrees during follow-up. The unfavorable growth group (n = 10) was characterized by an increase in the individualized ANB angle during the growth period from 5 to 12 years. Early characteristics of unfavorable growth included increased mandibular plane angle (measured to the sella-nasion line and the palatal plane, P <.05), increased lower gonial angle (P <.05), and a decreased ratio of posterior-to-anterior face height (P <.05) [corrected]. At the longitudinal follow-up at age 12, the 2 groups showed significant differences in SNB (P <.01) and individualized ANB (P <.01). The improved sagittal jaw relationship in the favorable growth group was the result of changed mandibular position. Morphogenetic posterior rotation seems to occur early in patients with skeletal Class II pattern and unfavorable growth and might be part of an adaptive mechanism compensating for insufficient mandibular growth.