Treatment Effects of the Edgewise Herbst Appliance: A Cephalometric and Tomographic Investigation

Objectives: To identify skeletal and dental changes in Class II malocclusion corrected with the Edgewise Herbst appliance. Methods: 32 subjects (18 females, 14 males) treated with Edgewise Herbst appliance by author T.D. Control group obtained from Case Western Reserve University, Bolton-Brush Study. Cephalometric measurements taken at pre-treatment (T1), post-treatment (T2), and 16 months following removal (T3). Position of condyle relative to glenoid fossa was determined using horizontally corrected axis tomograms taken at T1 and T2. Data analyzed using ANOVA, Tukey-Kramer multiple comparison test, and a two-tailed t-test. Results: Following 8 months of treatment (T1-T2), overjet improved by 8.4 mm compared to control group. The maxilla moved backward at point A by 1.4 mm and the mandible moved forward by 1.7 mm. Maxillary incisors moved lingually by 1.7 mm and mandibular incisors proclined by 3.6 mm. At T2, tomograms showed only 0.2 mm of forward condyle movement within the fossa. Sixteen months following Herbst removal (T2-T3), maxilla moved forward 1.2 mm, mandible relapsed posteriorly 0.7 mm. Maxillary incisors moved labially 1.7 mm and mandibular incisors moved lingually 3.3 mm. The net treatment effects (T1-T3) were an overjet correction of 2.7 mm with 85% contributed by skeletal corrections (1.3mm restraint in maxillary growth and 1.0 mm of forward mandibular growth as compared to controls). Conclusion: Class II treatment results using the Herbst appliance are contributed to by both skeletal and dental changes with minimal changes in the position of condyles in the fossa.