As G.K. Chesterton once wrote, "A man does not know what he is saying until he knows what he is not saying."¹ Use of the term "temporomandibular disorders" (TMD) clearly fits this description. Having been introduced into the literature as a means of solving a complex taxonomic dilemma, the term has been misused to the degree that it now has led to more confusion than clarification. Perhaps it is time to reconsider the value of maintaining this diagnostic classification. In making this decision, it is important to understand how we arrived at the current situation.

	"TEMPOROMANDIBULAR DISORDERS": HISTORY OF THE TERM

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The earliest descriptions of conditions involving the temporomandibular joint (TMJ) date back to the fifth century and were concerned with the diagnosis and treatment of dislocation. Subsequently, there were references to so-called fixations that were related to TMJ ankylosis and arthritis. Thus, initially, although all of the conditions affecting the TMJ were not fully understood, there was a disease concept of TMJ involvement.

Before the establishment of formal dental education in the late 1800s, physicians generally treated these conditions. However, in 1918, a key article by Prentiss² sparked some interest in this subject in the dental community. Prentiss wrote, "When the teeth are extracted the condyle is pulled upward by the powerful musculature and pressure on the meniscus results in atrophy." Subsequently, articles by Summa,³ Monson,⁴ Wright⁵ and Goodfriend⁶ emphasized the role of missing teeth, lost vertical dimension and the resulting displacement of the mandible as the cause of the symptoms these patients experienced.

However, it was in 1934 that the first of a series of articles by otolaryngologist James Costen⁷ not only resulted in greater involvement of dentistry in the management of TMJ disorders and diseases, but also changed the entire diagnostic concept. In this article, Costen described a series of TMJ, ear and "sinus" symptoms that ultimately came to bear his name (Costen syndrome), which he attributed to nerve impingement from overclosure of the bite. Although it subsequently was shown that his anatomical explanations for the causes of the symptoms were incorrect,^8,9 his work still had a profound and long-lasting effect on the diagnosis and treatment of TMJ pain and dysfunction. As a result of his influence, there was a shift from the previous disease concept of diagnosis to a symptom (syndrome) concept of diagnosis, in which conditions of diverse etiology were combined under one diagnostic heading merely because they produced similar signs and symptoms (pain and dysfunction). Moreover, this also led to a "one diagnosis, one treatment" philosophy, which may explain some of the reasons why clinicians had difficulty in successfully managing the care of many of these patients.

Although the term "Costen syndrome" ultimately was abandoned and through the years was replaced by such terms as "TMJ syndrome," "TMJ pain-dysfunction syndrome," "mandibular pain-dysfunction syndrome" and "craniomandibular syndrome," the same diagnostic and treatment errors continued to be made. The focus still was on the TMJ, the etiology still was considered to be an alteration in the occlusion that caused condylar displacement (mechanical displacement theory),^10,11 and treatment consisted mainly of various modifications of the occlusion (occlusal equilibration, orthodontics and full-mouth reconstruction).^12,13 However, the evidence for these concepts was based mainly on the opinions of strong personalities and anecdotal success stories rather than on science, careful research and unbiased clinical data. As noted by Landa,^14(p12) "One of the gravest mistakes in the diagnosis of temporomandibular joint disturbances is the misinterpretation of certain positions of the condyle head in the glenoid fossa as evidence of pathology."

It was not until the 1950s that Schwartz^15,16 and his colleagues at Columbia University demonstrated that the masticatory muscles were contributing to some of the pain and dysfunction seen in patients with TMJ pain-dysfunction syndrome. Although they still believed that improper occlusion may be a contributing factor, they emphasized that what patients do with their teeth in reacting to stress may be even more important than any malocclusion that they may have.

In 1969, on the basis of investigations my colleagues and I conducted at the University of Illinois TMJ and Facial Pain Research Center, I¹⁷ expanded on the psychophysiological concepts of Schwartz¹⁶ and colleagues and proposed an entirely new theoretical concept of etiology for the muscular disorders. I also urged a change in nomenclature that would clearly separate the muscular disorders from the intracapsular TMJ pathology, suggesting use of the term "myofascial pain-dysfunction (MPD) syndrome" for the former conditions.

As a result of the contributions of Schwartz¹⁶ and colleagues and my colleagues and me,¹⁷ there was a gradual acceptance by some clinicians that patients experiencing pain and dysfunction could have a joint problem, a muscle problem or both. Nevertheless, many clinicians continued to focus on correction of the occlusion as the way to manage these conditions. Recognizing the existing confusion in the field, in 1982 Robert H. Griffiths, then president of the American Dental Association, arranged for the organization of The President’s Conference on the Examination, Diagnosis and Management of Temporomandibular Disorders with the hope of "establishing a rational, unbiased approach to these disorders" (cited in Laskin and colleagues¹⁸). Some of the resulting recommendations from this conference were that the use of broad, nonspecific diagnostic labels such as "temporomandibular joint dysfunction" be discouraged, that the all-inclusive umbrella term be "temporomandibular disorders" and that separated under this heading would be conditions that primarily involved the muscles of mastication and those that involved the TMJ. Whereas this seemed like a logical solution to a confusing situation, a review of the literature since that time indicates that it has not necessarily had the desired effect. Unfortunately, many clinicians have merely substituted the inclusive term "TMD problem" for "TMJ problem" without changing their thinking about the source of each patient’s problem, its diagnosis, its etiology or its treatment. Perhaps even more confusing has been use of the term TMD as a singular noun in the literature, making it difficult to determine what condition (or conditions) the "TMD patient(s)" actually had and, therefore, making it impossible to interpret the findings logically and apply them clinically.

	THE CURRENT SITUATION

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A review of some of the current literature shows many instances of such confusion. For example, examination of the 18 issues of The Journal of the American Dental Association published from January 2006 to June 2007 revealed seven articles dealing with TMDs. In four of these articles, either the Research Diagnostic Criteria for Temporomandibular Disorders (RCD/TMD)¹⁹ were used correctly to indicate the patient population or the conditions being studied were specifically stated.^20–23

In three other articles, however, it was not possible to establish clearly what condition was being investigated^24–26 or, therefore, how to apply the findings. In an article entitled "Efficacy of an Early Intervention for Patients With Acute Temporomandibular Disorder–Related Pain: A One-Year Outcome Study,"²⁴ selection of the subjects was based on palpation of 20 muscle sites and potential subjects’ answers to the question, "Have you had pain in the face, jaw, temple, in front of the ear, or in the ear in the last month?" This would include patients with both myogenous and arthrogenous problems, who might respond differently to a biopsychosocial intervention; however, no distinction was made.

Another example of an ill-defined subject population is found in the article entitled "Third-Molar Extraction as a Risk Factor for Temporomandibular Disorder."²⁵ In this study, the authors examined the dental insurance records of 34,491 subjects who had had third molars removed for claims indicating subsequent development of TMD. The authors found that 391 patients had such claims and concluded that third-molar removal is a risk factor. However, without knowledge of the specific diagnoses of the conditions that were included, it is not possible to conclude that there is a cause-and-effect relationship, because there are temporomandibular disorders that could not possibly be caused by a tooth extraction such as degenerative arthritis, or an internal derangement in a patient with a previously normal TMJ.

Examples of similar problems in accurately identifying the subjects studied also can be found in articles published in other journals. In two reports published in a single issue of Journal of Orofacial Pain,^27,28 researchers studied coping mechanisms in patients who had at least one RDC/TMD Axis I TMD pain diagnosis.¹⁹ This, therefore, would include patients with a muscle diagnosis, a disk displacement, or arthralgia or arthritis. On the basis of their findings, one would have to assume that the coping mechanisms would be the same regardless of the cause of the chronic pain. Although this may be true, it also is possible that dividing the subjects into the three specific diagnostic categories would have revealed differences.

Clearly, the simplest way to avoid the diagnostic confusion in the literature is to eliminate use of the term "temporomandibular disorders."

An article in Angle Orthodontist entitled "TMD in Relation to Malocclusion and Orthodontic Treatment"²⁹ is another example of how using TMD as a single entity makes what could be useful information difficult to interpret. The purpose of this study was to answer the question "Are signs and symptoms of TMD related to malocclusion or orthodontic treatment?" After an extensive review of 58 articles, the authors found that associations between specific malocclusions and the development of significant signs and symptoms of TMD could not be verified. However, there was no indication of either the specific TMDs that were being evaluated or the types of malocclusion that were being considered. Whereas malocclusions may not be associated with the development of myofascial pain or an internal derangement, one certainly would expect to see various types of malocclusion in people with developmental disturbances.

	RESOLVING THE DIAGNOSTIC DILEMMA

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Clearly, the simplest way to avoid the diagnostic confusion in the literature is to eliminate use of the term "TMD." Although it once may have served a useful purpose as a transition from even worse diagnostic labeling, its continued use no longer can be defended in light of the many scientific advances that have been made in this field. Because TMD mixes conditions involving two anatomical areas, it is not logical to use such an umbrella term to describe disorders when the conditions in each area now can be diagnosed precisely and assigned specific names (Box). This is particularly important for clinicians to consider when determining the appropriate treatment for a patient.

	CONCLUSION

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Just as we once abandoned use of the term "TMJ syndrome" because our increased knowledge about the patients involved allowed more accurate diagnosis and treatment, so the time has come to eliminate TMD from our vocabulary. The box provides a list of the more common diagnostic terms that I suggest be substituted for TMD. Moreover, when reporting their findings, authors need to define clearly their study patient populations, and journal editors need to monitor more carefully that this is being done.