Vertical dentofacial changes during Herbst appliance treatment. A cephalometric investigation.

The effect of bite jumping with the Herbst appliance on the vertical dimensions of the dentofacial complex was analysed on profile roentgenograms. The material consisted of 42 Class II, Division 1 malocclusion cases with a deep anterior overbite. Twenty-two of the cases were successfully treated with the Herbst appliance for six months. The other 20 cases served as a control group. The Herbst appliance had a pronounced effect on vertical tooth position. The mandibular incisors and maxillary molars were intruded during treatment while the mandibular molars were allowed to erupt freely. As a result of the dental changes the overbite was reduced, lower facial height was increased as well as the angulation of the maxillary and mandibular occlusal planes. A small positive correlation existed between vertical bite opening at the start of treatment and the treatment changes of overbite, lower facial height and mandibular vertical tooth position. The appliance had a limited effect on vertical mandibular and maxillary jaw position, expressed by the angles ML/NSL and NL/NSL. In four patients, however, a marked posterior rotation of the entire maxillary complex was noted. The clinician should be aware of the vertical dentofacial changes occurring during Herbst appliance treatment and consider these changes when designing his treatment strategy and planning post-treatment retention.