Temporomandibular disorders (TMDs) are a set of musculoskeletal disorders affecting the temporomandibular joint (TMJ), the masticatory muscles, or both. TMDs comprise many diverse diagnoses with similar signs and symptoms affecting the masticatory system, which can be acute, recurrent, or chronic. TMDs are rarely life threatening, but can impact heavily on an individual's quality of life. Studies show that about 3–7% of the population need treatment.
TMDs occur disproportionately in women of childbearing age in a ratio of 4:1 to 6:1, and the role of estrogens seems to show an association. The prevalence drops off dramatically for both men and women after age 55.
Al-Jundi MA, John MT, Setz JM, Szentpétery A, Kuss O. Meta-analysis of treatment need for temporomandibular disorders in adult nonpatients. J Orofac Pain
[PubMed—indexed for MEDLINE]. (A meta-analysis of nonpatient studies to determine the prevalence of treatment need for temporomandibular disorders in adult populations is about 15%.)
Wang J, Chao Y, Wan Q, Zhu Z. The possible role of estrogen in the incidence of temporomandibular disorders. Med Hypotheses
2008 Oct;71(4):564–567 [Epub Jul 1, 2008]
[PubMed—indexed for MEDLINE]. (The overwhelming majority of patients treated for temporomandibular disorders are women and the available literature is examined to evaluate the role of estrogens in TMD.)
The cause of TMD is variable and uncertain, and it is thought to be multifactorial in most cases. Genetic factors have recently been implicated. Most factors are not proven causal factors, but they are associated with TMDs. Predisposing factors increase the risk of TMDs. Predisposing factors are trauma, both direct (eg, blows to the jaw) and indirect (eg, whiplash injuries), and stress. Microtrauma is caused by clenching and grinding of the teeth. Stress can be a predisposing factor owing to the disruption of restorative sleep and the increase of nocturnal bruxism. Trauma and stress are also precipitating factors.
Perpetuating factors that sustain a TMD are stress, poor coping skills, harmful habits such as clenching and grinding, and poor posture. Nonrestorative sleep also may be a major factor in the perpetuation of chronic jaw pain.
Diatchenko L, Slade GD, Nackley AG, Bhalang K, Sigurdsson A, Belfer I, Goldman D, Xu K, Shabalina SA, Shagin D, Max MB, Makarov SS, Maixner W. Genetic basis for individual variations in pain perception and the development of a chronic pain condition. Hum Mol Genet
2005 Jan 1;14(1):135–143 (Epub 2004 Nov 10)
[PubMed—indexed for MEDLINE]. (Genetic variants (haplotypes) are strongly associated (P
= 0.0004) with variation in the sensitivity to experimental pain and risk of developing myogenous temporomandibular joint disorder (TMD).
Bruxism, or grinding the teeth during sleep, has been thought to be a predisposing, precipitating, and ...