Two cases of impaction of the mandibular second molar treated by means of orthodontic techniques, were presented. It takes about 6 to 8 months for uprighting mandibular second molar. There is no significant difference in the uprighting times between in the case of extraction of the third molar or not. We consider that the corticotomy of the diatal part of the mandibular second molar shortens the uprighting times of the mandibular second molar. Treatment results of both cases were favorable at 2 years after uprighting of the mandibular second molar.