Evaluation of the modified maxillary protractor applied to Class III malocclusion with retruded maxilla in early mixed dentition.

The purpose of this study was to evaluate the effects of orthodontic treatment with a maxillary protraction bow appliance on anterior crossbite patients with Class III malocclusion in the mixed dentition. The 29 patients treated with a maxillary protraction bow appliance (11 boys, 18 girls) were compared with 25 matched, untreated controls with anterior crossbite (10 boys, 15 girls). The mean age before treatment was 8 years 7 months (range, 6 years 3 months to 11 years 6 months). The mean treatment period to achieve a normal overjet was 10.2 months (range, 5 to 18 months). Fifty-nine cephalometric angular and linear parameters were compared between the treated group and the untreated controls using the analysis of variance and the paired t test to evaluate the effect of gender and the maxillary protraction bow appliance treatment. Skeletal and dentoalveolar advancement of the maxilla and retrusion of the mandible contributed significantly to the improvement of Class III malocclusion in the treated group. These results suggest that a maxillary protraction bow appliance is effective for correcting anterior crossbite with a retruded maxilla in the early mixed dentition.