Tooth movement in class II division 1 malocclusion after premolar extraction

Objective To investigate the magnitude and pattern of tooth movement in class Ⅱ division 1 malocclusion cases treated with extraction of upper first and lower second premolars.Methods Thirty cases of class Ⅱ division 1 malocclusion were examined with pre-and post-treatment lateral cephalometric radiographs.The movement of both front and posterior teeth,on both upper and lower jaws were measured and compared.Results The crowns of the upper and lower central incisors moved distally for(3.59±2.39) mm and(2.32±1.58) mm,respectively.The root apexs moved distally for(1.19±2.44) mm and(1.56±0.98) mm.The labial inclinations of the upper and lower central incisors decreased by 9.87°±7.68° and 2.64°±3.99°.The crowns of the upper and lower first molars moved mesially for(4.32±4.87) mm and(4.38±1.46) mm,respectively.The buccal root apexs moved mesially for(2.74±1.56) mm and(4.43±2.12) mm.The upper and lower first molars rotated 3.90°±4.55° and 1.25°±6.06° counterclockwisely.The changes were statistically significant(P0.05).Conclusion The ratio of front and posterior teeth movement is 1∶1.3 for maxillary teeth and 3∶5 for mandibular teeth.Upper incisors move as controlled tipping and lower incisors exhibit bodily movement.