A cephalometric and tomographic evaluation of Herbst treatment in the mixed dentition.

This study describes combined treatment and posttreatment effects for patients treated with the Herbst appliance in the mixed dentition followed by retention with a prefabricated positioner. The sample included 24 female and 16 male patients with Class II malocclusions. Posttreatment lateral cephalograms were taken an average of 17 months after Herbst removal, when the patients presented for phase II comprehensive orthodontics. The cumulative treatment and retention effects were compared with a sample of untreated Class II controls matched for age, sex, and mandibular plane angle. The overjet and molar relationship were corrected by 3. 4 and 3.3 mm, respectively. A headgear effect of Herbst therapy was observed, as anterior maxillary displacement was reduced by 1.2 mm. Condylar growth was redirected to produce 2.0 mm greater posterior growth in the treatment group. These effects produced significantly greater decreases in SNA (0.8 degrees ) and ANB (1.4 degrees ), and a tendency toward an increase in SNB (0.5 degrees ) Mandibular orthopedic effects resulted in an increase in anterior facial height (1.6 mm) and inferior displacement of the chin. Minimal changes in the displacement of condylion in relation to stable cranial base structures suggest that glenoid fossa displacement does not contribute in a clinically significant way to Class II correction. Pretreatment, immediate posttreatment, and postretention corrected temporomandibular joint tomograms demonstrated a tendency for the condyle to be slightly forward (0.2 mm) at the end of treatment and then to fall back after treatment. Statistically significant joint space changes were limited to the posttreatment period. We conclude that Herbst treatment in the mixed dentition, in combination with retention, produces significant long-term improvements in dental and skeletal relationships as a result of dentoalveolar changes and orthopedic effects in both jaws.