[Morphology and position of mandible in Herbst treatment. Cephalometric analysis of changes to end of growth period].

The purpose of this investigation was to analyse mandibular morphologic and jaw position changes in Herbst treatment on a short and long term basis. The patient material consisted of 12 boys with a Class II, Division 1 malocclusion treated with the Herbst appliance for a period of 6 months. The subjects were examined before treatment, after treatment, 1 year after treatment and at completion of growth (7 years after treatment). 10 boys with the same malocclusion as the Herbst cases served as controls. The method comprised of an analysis of profile roentgenograms in centric occlusion and with the mouth wide open. Herbst treatment resulted in an increase in jaw length and mandibular prognathism. The gonion angle was opened. These changes were accomplished by an increase in sagittal condylar growth and by bone resorption at the posterior part of the mandibular lower border. During the follow up period after removal of the Herbst appliance the treatment changes reverted and were comparable to those of the control subjects. No statistically significant long-term influence of Herbst treatment on mandibular morphology and jaw position could be verified.