Physicians – Definition
A Complex and Unique Anatomy
Anatomically, the temporomandibular joints are the most complex joints in the body. Located at the base of the skull anterior to the ears, their position places them among the most sensitive and vulnerable areas of the head, where they are richly innervated by sensory and motor branches of the Trigeminal nerve. The jaw joints are synovial joints that are unique because of the cartilage forming the oval-shaped disc that cushions each joint and also lines the head of the mandible (the condyle) and its insertion into the fossa of the temporal bone: It is less resilient fibrocartilage, not the typical joint hyaline cartilage. The joints are special in that they always work as a pair. Their coordinated action, controlled by 4 sets of masticatory muscles, enables the complex three-dimensional movements that orchestrate the repertoire of human facial movements critical in speaking, singing, expressing a smile, frown, kiss or other emotion, as well as governing the vital functions of biting, chewing and swallowing food. Not surprisingly, anything that disrupts the ability to perform these usually unconscious acts sounds an alarm of fear and anxiety that can be devastating.
A Common Disorder
TMJDs are surprisingly common.
A National Health Interview Survey, conducted by the National Center for Health Statistics of the Centers for Disease Control and Prevention in connection with the Third National Health and Nutritional Examination Survey indicated that 7 percent of the sample reported jaw pain and/or face/cheek pain, generally lasting more than 6 months. When extrapolated to the adult U.S. population, the figures for joint pain alone suggest that some 10 million people in the community at large experience symptoms of TMJDs in any year.
Other studies have confirmed that ballpark figure and have consistently shown that up to twice as many women as men experience symptoms of TMJDs. Most of the individuals surveyed did not seek professional treatment for their pain, using home remedies or over-the-counter drugs, or ignoring the pain. Indeed, many mild cases of TMJDs resolve over time with no treatment.
The picture changes for those seeking care. Women are three or more times more likely to seek primary care than men and represent the vast majority – up to 90 percent – of patients with severe cases who seek tertiary care At any level of severity, female TMJD patients are primarily women in their childbearing years.
As information has accumulated in recent years (serving partly as a reminder of the importance of obtaining a complete patient history), it appears that many patients with jaw problems experience co-morbidities, including chronic fatigue syndrome, fibromyalgia, irritable bowel syndrome, multiple chemical sensitivity/allergies, tension and migraine headaches, sleep disturbances and a variety of cardiovascular symptoms, including mitral valve prolapse and arrhythmias. Neither the extent of the association nor the sequence of onset of symptoms is known. In any case, two independent peer reviewed studies confirm that TMJD patients utilize health care at double to triple the rate of comparable patients and this health care is not for TMJ treatments.
TMJDs, once considered an above-the-neck pain problem, are beginning to be seen as complex diseases influences by sex, gender (defined as the cultural manifestations of sexual identity), and genetic, environmental and behavioral triggers.
Why Women?
The issue of how biological sex affects pain physiology has become a lively area of study in recent years. Investigators discovered estrogen receptors in the temporomandibular joint. Follow-up studies indicate that pain intensity varies over the menstrual cycle, usually increasing around the time of the menses and at ovulation. Population studies of 11- to 17-year-olds also indicate that with increased pubertal development, there is a statistically significant increase in back pain, headache and jaw pain reported by girls. The effects of exogenous hormones have also been examined, with one study indicating that the odds of being a TMJD patient increase by 30 percent and 20 percent, respectively, for women using postmenopausal estrogen or oral contraceptives, compared to controls.
In general, the female, jaw is smaller than that of the male, with a smaller range of jaw motions and vertical and protrusive openings. Based on animal studies, some muscle physiologists suggest that androgen exposure allows male masseter muscles to produce larger and faster forces than those of females, possibly increasing female, vulnerability to jaw problems.