"Effective condylar growth" and chin position changes in Herbst treatment: a cephalometric roentgenographic long-term study.

In 98 Class II Division 1 malocclusions treated with the Herbst appliance "effective condylar growth" (a summation of condylar remodeling, glenoid fossa remodeling, and condylar position changes within the fossa) and its influence on the position of the chin was analyzed. Lateral head films in habitual occlusion from before and after 0.6 years of Herbst treatment as well as 0.6 years and 3.1 years posttreatment were evaluated. All patients were treated to Class I or overcorrected Class I dental arch relationships. During the treatment period, effective condylar growth was relatively more backward directed and about three times larger than that in untreated subjects with ideal occlusion (Bolton Standards). During the first posttreatment period of 0.6 years, effective condylar growth recovered with respect to both the direction and amount of changes. During the second posttreatment period of 2.5 years, effective condylar growth was "normal." The corresponding chin position changes during the different examination periods were a mirror image of effective condylar growth provided no mandibular autorotation occurred. In cases with anterior mandibular autorotation, relatively more forward and in cases with posterior mandibular autorotation relatively more backward directed chin position changes resulted.