Inability to open one side of the mouth may be caused by temporomandibular arthritis, pericoronitis of wisdom teeth or acute apical infection with interstitial infection. 1. Temporomandibular arthritis is a common cause of restricted mouth opening, clinically manifested as inability to open one side of the mouth, which can be treated with physical therapy or surgery. 2. Wisdom tooth pericoronitis attack or acute apical infection accompanied by gap infection, inflammation invades the occlusal space will cause mouth opening limitation, that is, one side of the affected side of the mouth can not open, you can carry on the wisdom tooth pericoronary rinsing medication or root canal treatment to relieve the tooth, if the serious accompanied by the symptoms of systemic fever need to carry on the systemic anti-infective treatment. Therefore, the inability to open one side of the mouth is related to temporomandibular arthritis, and also related to the inflammation of the bite muscle, need to go to the stomatology department for examination.