[Position changes of mandibular condyle in Herbst treatment. Radiographic study]

The study aimed to analyse the short- und long-term changes in condyle position in Class II/1 malocclusions treated with the Herbst appliance. Cephalometric reoentgenograms from a Herbst group (n = 30, mean age 12.1 years) were compared to those of a Control group (n = 12, mean age 11.0 years). The total observation period was 3 1/2 years. Centric occlusion and mouth open profile roentgenograms (to visualize the condyle) were analysed at four occasions. Mandibular tracings from the mouth open headfilms were superimposed on the centric occlusion headfilms using the Nasion-Sella-Line (NSL) for reference. NSL and its perpendicle NSLP through Sella (S) were used as a reference grid for linear measurements. When starting Herbst treatment the condyle was displaced 6 mm anteriorly and caudally. After 7 months of treatment the condyle was located 0.8 mm caudally to the pre-treatment position. No difference existed, however, between the Herbst and Control group. During the total observation period of 3 1/2 years the condyle in both examination groups moved caudally and posteriorly. This was thought to be a result of normal growth changes. It was concluded that Herbst treatment did not have an adverse effect on the position of the condyle.