The permanent second molars, erupted about 12-13 years old, are finally erupted except wisdom teeth. Although they are likely to be excluded in the orthodontic treatment because located in the most posterior area of the dentition, about twenty percents of the orthodontic patients have abnormal occlusion of the permanent second molars, and we usually observed the malalignrnent of the permanent second molars in the finished case without including this teeth. These permanent second molars should be necessarily corrected by orthodontic appliances for the dynamic-normal occlusion. Moreover, according to the previously mentioned treatment philosophy, there are clear advantages in the cases which the permanent second molars were used for anchorage source, and this has been proposed convincingly by many authers. Therefore it is reasonable that orthodontists determine to include the permanent second molars among orthodontic treatment, but particular cases.