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

This study describes combined treatment and posttreatment effects for patie nts treated with the Herbst appliance in the mixed dentition followed by re tention with a prefabricated positioner. The sample included 24 female and 16 male patients with Class II malocclusions. Posttreatment lateral cephalo grams were taken an average of 17 months after Herbst removal, when the pat ients presented for phase II comprehensive orthodontics. The cumulative tre atment 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 he adgear effect of Herbst therapy was observed, as anterior maxillary displac ement 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 orthoped ic effects resulted in an increase in anterior facial height (1.6 mm) and i nferior displacement of the chin. Minimal changes in the displacement of co ndylion in relation to stable cranial base structures suggest that glenoid fossa displacement does not contribute in a clinically significant way to C lass II correction. Pretreatment, immediate posttreatment, and postretentio n corrected temporomandibular joint tomograms demonstrated a tendency for t he condyle to be slightly forward (0.2 mm) at the end of treatment and then to fall back after treatment. Statistically significant joint space change s were limited to the posttreatment period. We conclude that Herbst treatme nt in the mixed dentition, in combination with retention, produces signific ant long-term improvements in dental and skeletal relationships as a result of dentoalveolar changes and orthopedic effects in both jaws.