Morphological changes in dental arches following prefabricated myofunctional appliance therapy in patients with growing Class II

Objectives: This study aimed to quantitatively evaluate morphological changes in dental arches following prefabricated myofunctional appliance therapy in growing patients with Class II malocclusion through dental cast analysis.Methods: This retrospective study included patients aged 8-12 years with skeletal Class II division 1 malocclusion who were treated with prefabricated myofunctional appliances.Dental casts were obtained at baseline (T0) and 12 months after treatment (T1).The measurements included intercanine width, intermolar width, arch perimeter, arch length, overjet, overbite, sagittal molar relationship, and irregularity index.Statistical analysis was performed using the Wilcoxon signed-rank test, with significance set at P<0.05.Results: Following prefabricated myofunctional appliance therapy, significant increases were observed in maxillary intercanine and intermolar widths.However, the changes in mandibular arch width were not statistically significant.While the maxillary arch length and perimeter remained unchanged, mandibular measurements showed a decreasing pattern.The overjet and overbite showed significant reductions, and the sagittal molar relationship improved toward Class I occlusion.The irregularity index decreased significantly, indicating an improvement in mandibular anterior crowding.Conclusions: Prefabricated myofunctional appliance therapy effectively promoted maxillary transverse expansion and enhanced occlusal relationships in patients with growing Class II division 1 malocclusion.Despite limited mandibular arch expansion, the treatment successfully resolved mandibular anterior crowding through incisor proclination.These findings suggest that prefabricated myofunctional appliances can be an effective interceptive treatment option for skeletal Class II malocclusion in growing patients; however, long-term stability requires further investigation.