Estimates indicate that more than 10 million Americans have temporomandibular joint and muscle disorders, though a specific number is not known, according to the National Institute of Dental and Craniofacial Research. Women seem to have TMJ disorders more often than men.
TMJ is sometimes caused by a jaw or temporomandibular joint injury, explains the National Institute of Dental and Craniofacial Research. Scientists are also researching a possible link between TMJ and female hormones. As of 2015, however, scientists generally do not understand what causes TMJ.
TMJ usually does not signify a serious underlying health condition and its discomfort often goes away without medical treatment, according to the National Institute of Dental and Craniofacial Research. Self-care commonly eases symptoms, though some individuals have prolonged, significant TMJ symptoms.