Dental and skeletal changes in patients with mandibular retrognathism following treatment with Herbst and pre-adjusted fixed appliance

OBJECTIVE: To assess the dentoskeletal changes observed in treatment of Class II, division 1 malocclusion patients with mandibular retrognathism. Treatment was performed with the Herbst orthopedic appliance during 13 months (phase I) and pre-adjusted orthodontic fixed appliance (phase II). METHODS: Lateral cephalograms of 17 adolescents were taken in phase I onset (T(1)) and completion (T(2)); in the first thirteen months of phase II (T(3)) and in phase II completion (T(4)). Differences among the cephalometric variables were statistically analyzed (Bonferroni variance and multiple comparisons). RESULTS: From T(1) to T(4), 42% of overall maxillary growth was observed between T(1) and T(2) (P < 0.01), 40.3% between T(2) and T(3) (P < 0.05) and 17.7% between T(3) and T(4) (n.s.). As for overall mandibular movement, 48.2% was observed between T(1) and T(2) (P < 0.001) and 51.8% between T(2) and T(4) (P < 0.01) of which 15.1% was observed between T(2) and T(3) (n.s.) and 36.7% between T(3) and T(4) (P < 0.01). Class II molar relationship and overjet were properly corrected. The occlusal plane which rotated clockwise between T(1) and T(2), returned to its initial position between T(2) and T(3) remaining stable until T(4). The mandibular plane inclination did not change at any time during treatment. CONCLUSION: Mandibular growth was significantly greater in comparison to maxillary, allowing sagittal maxillomandibular adjustment. The dentoalveolar changes (upper molar) that overcorrected the malocclusion in phase I, partially recurred in phase II, but did not hinder correction of the malocclusion. Facial type was preserved.