This report shows an orthodontic treatment case with a pain disorder. The patient complained of impaired molar masticatory function after a first orthodontic treatment. The lower midline was shifted to the right direction caused by initial occlusal contact at second molars. She had also severe upper molar spontaneous pain, although there was no organic disease at this area. During second orthodontic treatment, the pain increased gradually. She was diagnosed as a Pain disorder (PD) and Tricyclic antidepressants (TCAs) was administered at the pain clinic. Two month after medicinal treatment, the patient stated that the pain had completely disappeared. Also a good occlusion was achieved by the second orthodontic treatment after 1 year. She did not have a pain without any medication and occlusion continued to be stable during these 5 years. Because an atypical odontalgia increases these days, orthodontists should have the knowledge of this disease and appropriate coping to a patient is necessary. There are a few patients with dental pain without any identifiable dental etiology. Such patients are classified under the category of atypical odontalgia. Because an atypical odontalgia such as somatoform pain disorder increases these days, orthodontists should have the knowledge of this disease and appropriate coping to a patient is necessary. This case report suggests that it is possible that PD can be caused by improper orthodontic treatment and dentists should care much about atypical odntalgia such as somatoform pain disorder.