The etiology of temporomandibular disorders（TMD）is unknown. A variety of etiologic factors has been suggested as the cause of the disorders. The earliest and still-popular etiologic theory proposed TMD are induced malocclusion. In the early 1960's，the psychological distress have been recognized dominated the literature. From then on，other etiologic factors for TMD were，such as trauma of TM tissues，autoimmunity factory，anatomical susceptibility，and so on. The lack of clear single cause has resulted in the proposal of a multifactorial etiology.
