RESUMEN
<p><b>OBJECTIVE</b>The purpose of this investigation is to compare the differences of hard tissue changes and stability in patients with Class II division 1 treated with extraction of four first premolars by Begg appliance and Edgewise appliance.</p><p><b>METHODS</b>The study was conducted using lateral cephalometric radiographs taken pretreatment, posttreatment and following-up. Thirty patients who had an Angle's Class II division 1 malocclusion were treated with first premolar extractions (19 by Begg appliance and 11 by Edgewise appliance). Cephalometric radiographs were scanned and the data were analyzed according to the paired and unpaired t-test.</p><p><b>RESULTS</b>The differences between the pretreatment and posttreatment periods were statistically significant for all the incisor and molar cephalometric variables (P<0.05) except UMA-PPV and UMC-PPV by Edgewise appliance. During treatment the incisors moved lingual-inclined and extrusively, the molar moved mesially and extrusively except that the upper molar of the Edgewise group stayed relatively stable anteroposteriorly. During the follow-up period the anterior teeth moved forward and extrusively, the upper molar moved mesially and extrusively. There was no significant differences of tooth movement and stability between Begg appliance and Edgewise appliance (P>0.05).</p><p><b>CONCLUSION</b>There is no significant differences of hard tissue changes and stability between Begg appliance and Edgewise appliance.</p>