Before the orthodontic treatment, the problems of the teeth should he well-controlled. During the orthodontic processing, the resorption of tooth root and pathologic changes of pulp always happened. In these conditions, we must treat these apical lesions with endodontic procedures as soon as possible. Herein, we present a clinical case that there were pulps necrosis because of poor oral hygiene during orthodontic treatment. After complete endodontic management, the apical lesions were significantly improved without root resorption and the orthodontic processing was performed smoothly.