Temporomandibular Joint Syndrome (Temporomandibular Disorders)

Temporomandibular disorder(s) (TMD), or temporomandibular joint syndrome, is the most common cause of facial pain after toothache. In the past, many physicians called this condition TMJ disease or TMJ syndrome. TMD was previously known under the eponymous title of Costen syndrome, after Dr. James Costen, who elucidated many aspects of the syndrome as it relates to dental malocclusion. Today, a much more comprehensive view of this condition exists, and the term temporomandibular disorder (TMD) is the preferred term according to the American Academy of Orofacial Pain (AAOP) and most other groups who sponsor studies into its origins and treatment.

Interestingly, the National Institute of Dental and Craniofacial Research (NIDCR) puts TMJ and TMD together and refers to them as temporomandibular joint disorder (TMJD). However, the term TMD is preferred and used in this article.



No unequivocal definition of the disease exists and 2 classification schemes are used. The AAOP classification divides TMD broadly into 2 syndromes:

• Muscle-related TMD (myogenous TMD), sometimes called TMD secondary to myofascial pain and dysfunction
• Joint-related (arthrogenous) TMD, or TMD secondary to true articular disease

Of note, these 2 types often coexist in one patient, making diagnosis and treatment more challenging.
Myogenous TMD is more common. In its pure form, it lacks apparent destructive changes of the TMJ on radiograph and can be caused by multiple etiologies such as bruxism and daytime jaw clenching.
Arthrogenous TMD can be further specified as disk displacement disorder, chronic recurrent dislocations, degenerative joint disorders, systemic arthritic conditions, ankylosis, infections, and neoplasia.
The Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) also exist. The RDC/TMD criteria are composed of algorithms that aid in obtaining a diagnosis along 2 separate axes. The Axis I score provides what is considered the clinical diagnosis, and the Axis II score provides an assessment of mandibular function, psychological status, and level of TMD-related psychosocial disability. This discussion emphasizes the terminology and viewpoint of the AAOP approach. However, the authors are mindful of the important features of the RDC/TMD system. As is the case for most diseases and syndromes, the effect on the patient's life is a major feature of the problem and the psychological and psychosocial aspects are of great importance.

Pathophysiology

In myogenous temporomandibular disorder, the cause of the symptomatology (ie, pain, tenderness, and spasm of the mastication muscles) is muscular hyperactivity and dysfunction due to malocclusion of variable degree and duration. Psychological factors may also play a role.
In TMD of articular origin, disk displacement is the most common cause. Abnormal anterior displacement and interposition of the posterior band between the condyle and the eminence cause pain, pops, and crepitus. If the anteriorly displaced posterior band spontaneously returns to the normal position before the completion of jaw opening, it is called anterior displacement with reduction.
The sudden reduction of the posterior band causes the characteristic pop or click. If the posterior band remains anteriorly displaced at all times during jaw opening, it is called anterior displacement without reduction; full jaw opening may not be possible. Inability to attain a jaw opening of more than 10 mm is known as closed lock. In TMD of articular origin, the spasm of the mastication muscle is secondary in nature.
The other causes of arthrogenous TMD are diseases such as degenerative joint disease, rheumatoid arthritis, ankylosis, dislocations, infections, and neoplasia, the pathophysiology of which are self-explanatory. One study found that, in patients with chronic inflammatory connective tissue disease, the pain on mandibular movement and tenderness on posterior palpation of temporomandibular joints was related to the level of tumor necrosis factor alpha in the synovial fluid.