目的　为代偿下颌第一恒磨牙的缺失 ,将下颌第二、三磨牙前移到原第一、二磨牙的位置后 ,再将前倾阻生的第三磨牙矫正到正常位置并发挥正常功能。方法　用方丝弓固定矫治器将第二、三磨牙前移到第一、二磨牙的位置 ,再后推第三磨牙 ,解除第二磨牙对其的阻生 ,最后 ,后倾竖直该牙。结果　 9例前倾阻生的下颌第三磨牙在第一恒磨牙缺失时 ,通过该方法矫治 ,均成功地使第三磨牙竖直到正常位置。结论　下颌第一恒磨牙缺失后 ,可用矫正的方法使第二、三磨牙前移 ,分别代替原第一、二磨牙 ,前倾阻生的第三磨牙可以矫正 Objective To compensate for the absence of mandibular first permanent molars, move the second and third mandibular molars forward to the position of first and second molars, and then correct the anterior third impacted molar to normal position and exert normal function . Methods With the arch wire fixation appliance, the second and third molars were advanced to the position of the first and second molars, and then the third molars were pushed to release the impaction of the second molars. Finally, . Results 9 cases of mandibular third molars anteriorly obstructed were corrected by this method when the first permanent molars were absent, all of which successfully made the third molars upright to the normal position. Conclusions After the first mandibular permanent molars are absent, the second and third molars can be advanced by orthodontic methods to replace the first and second molars, respectively, and the anterior third molar can be corrected