the utility and validity of current diagnostic procedures for defining

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Advances in Dental Research

DOI: 10.1177/08959374930070022101 1993; 7; 97 Adv. Dent. Res.

G.T. Clark, R.E. Delcanho and J.-P. Goulet Patients

The Utility and Validity of Current Diagnostic Procedures for Defining Temporomandibular Disorder

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THE UTILITY AND VALIDITY OF CURRENT

DIAGNOSTIC PROCEDURES FOR DEFINING

TEMPOROMANDIBULAR DISORDER PATIENTS

G.T. CLARK

R.E. DELCANHO

J.-P. GOULET1

University of California, Los Angeles, Dental ResearchInstitute, UCLA School of Dentistry,73-017 Center for theHealth Sciences, 10833 Le Conte Avenue, Los Angeles, CA90024-1668; and 'Universite Laval, Ecole de MedecineDentaire, Montreal, Province Quebec, Canada

Adv Dent Res 7(2):97-112, August, 1993

Abstract—This paper describes the evolution of differentconcepts of classifying and defining TemporomandibularDisorders (TMD) for both clinical and research settings. Theliterature is reviewed with respect to the utility and validity ofthe different questionnaire and examination procedures thathave been used to assess TMD patients. The presented view isthat many of these procedures have not been validated, thatthere is a lack of standardization in the use of the proceduresthemselves, and that an ideal method of classifying this broadgroup of patients into better-defined subgroups has not yetbeen developed. More standardized and better-defined researchby trained and calibrated researchers is needed worldwide toelucidate these subgroups so that a better and widely agreedupon research classification system can be developed forwidespread use. It also seems clear that as research requirementsfor defining TMD patient subgroups become more stringentover time, it may not be practical for the clinician to implementthem on a day-to-day basis in his or her practice. As such, apractical utilitarian definition of the common subtype of TMDpatients is also needed which parallels any research grouping,so that data from research are valuable and generalizable to thepracticing clinician.

Presented at the 12th International Conference on OralBiology (ICOB), ^Modern Concepts in the Diagnosis ofOral Disease', held at Heriot-Watt University, Edinburgh,Scotland, July 6-7,1992, sponsored by the InternationalAssociation for Dental Research and supported by UnileverDental Research

T raditionally, Temporomandibular Disorders (TMD) havebeen defined as pathological conditions which producemusculoskeletal pain and dysfunction in theTemporomandibular (TM) system. These conditions are

characterized by a constellation of signs and symptomsincluding pain associated with jaw function, limited range ofmandibular motion, masticatory muscle and Temporo-mandibular Joint (TMJ) tenderness on palpation, and TMJsounds. The last two decades have witnessed continued interestand expansion of knowledge in the field of TMD. Undoubtedlythis has substantially increased the bulk of knowledge availableregarding clinical presentations of TMD, as well as anunderstanding of different facets of the associated diseaseprocesses. However, a critical analysis of what we have learnedso far leaves us with new challenges. The term TMD itself isvery broad and unrestrictive, and is used primarily to give thehealth care provider a term for globally describing the populationof patients with problems causing abnormal, usually painful,function of the jaw muscles and joints. Unfortunately, individualpatients with a TMD have quite distinct variations of theprimary signs and symptoms. Furthermore, the term TMDencompasses patients having clearly different mechanisms oftheir disease. For example, rheumatoid and traumatic arthritispatients may present with exactly the same clinical features.That such etiologic and symptomatic differences exist betweenvarious TMD patients supports the view that there are distinctsubgroups of TMD. Patients presenting with characteristicsigns and symptoms of TMD can therefore no longer be simplylabeled as "TMD patients". The term TMD does not help thehealth care provider to categorize individual patients into morespecific TMD subgroups with similar underlying mechanismsthat would allow appropriate treatment to be prescribed.Similarly, the above global, nonspecific definition of TMD isof little value to the researcher, since it is inadequate to definea specific, homogeneous population of subjects.

The aims of this review article are to: (1) give an overview ofhow TMDs have been defined in the past, (2) explain the presentneed for a way to separate the various subcategories of TMD forboth clinical and research purposes, (3) give a critical appraisalof the utility and validity of the diagnostic procedures currentlyused to identify TMD research subjects, and (4) point out areasof research required to help resolve key issues in appropriatedefinition of subgroups of the TMD patient population.

CLINICAL DEFINITIONS OFTEMPOROMANDIBULAR DISORDERS

The Myofascial Pain Dysfunction ConceptLaskin (1969) described a specific subgroup category withinTMD called Myofascial Pain Dysfunction Syndrome (MPD).

97 by James Howard on April 17, 2010 http://adr.sagepub.comDownloaded from


98 CLARK ET AL. ADV DENT RES AUGUST 1993

TABLE 1CRITERIA FOR MYOFASCIAL PAIN

DYSFUNCTION SYNDROME*Positive Inclusionary Signs:

—Unilateral pre-auricular pain—Muscle pain on palpation—Joint noise (clicking)—Limited opening

Negative Exclusionary Signs:—No joint tenderness when palpating through the

external auditory meatus—No clinical, radiographic, or biochemical evidence

of organic joint disease* From Laskin (1969).

MPD was proposed for use by clinicians for diagnostic andtreatment planning purposes and for researchers for the purposeof defining subject groups. For the diagnosis of MPD to bemade, four positive and two negative (i.e., exclusionary) signshad to apply (Table 1). If a negative sign was present, thediagnosis of MPD had to be excluded. It was unclear, however,if a patient had to possess all or only a few of the positive signsto be diagnostically categorized as MPD. The non-MPDpatients were also not clearly defined but, by implication,were considered to be TMJ arthritis patients. Another seriousflaw in the system was that specific operational definitions foreliciting the positive and negative signs were not provided.For example, with muscle pain on palpation, it was notspecified how much palpation pressure should be applied,which muscles or muscle sites were to be palpated, or howmany positive muscle sites were necessary for the findings tobe called a positive sign. Another problem with the MPDcriteria was that they included patients with internalderangements of the TMJ as well as patients with strictlymuscular problems, thus reducing the classification system'sclinical utility. Although Laskin's MPD criteria had someobvious flaws, and the validity of these criteria was nevertested, they did have good conceptual utility and were used byclinicians and researchers for over 14 years.

Subsequent Clinical Classificationsof Temporomandibular DisordersBecause an improved understanding of internal derangementsof the TMJ resulted following the rediscovery of TMJarthrography in the late 1970' s, Laskin' s MPD concept becameinadequate for clinical use. This problem prompted the Presidentof the American Dental Association to organize a conferenceto establish guidelines for the clinical diagnosis of TMD(Laskin et al., 1983). During the conference, use of the diagnosticnomenclature system suggested by Bell (1982) was decidedupon. As a clinical descriptive system, the Bell classificationhad more inherent utility than any previous system. Bell'ssystem, however, was never considered to be a researchdefinition for TMD or its subgroups, because no detailedoperational definitions were given, and no reproducibility orvalidity testing was ever performed upon it (Table 2).

TABLE 2SUGGESTED TMD CLASSIFICATION SCHEME

FROM THE PRESIDENT'S CONFERENCEON EXAMINATION, DIAGNOSIS,

AND MANAGEMENT OFTEMPOROMANDIBULAR DISORDERS*

Acute Muscle Disorders:—Splinting—Spasm—Myositis

Disc Interference Disorders:—Class I interferences—Class II interferences—Class III interferences—Class IV interferences—Spontaneous anterior interferences

Inflammatory Disorders:—Synovitis—Capsulitis—Inflammatory arthritis

Chronic Mandibular Hypomobilities:—Contracture—Capsular fibrosis—Ankylosis

Growth Disorders:—Aberration of development—Acquired structural changes—Neoplasia

* From Laskin ef al (1983).

Furthermore, some of the categories proposed by Bell had lowutility, since it was never clear if such tissue-specific distinctionscould be made by a clinical examination (e.g., synovitis vs.capsulitis). Finally, the suggested nomenclature for describingTMJ derangements was not always self-evident (e.g., the terms"Class I, II, III, and IV").

In 1985, Eversole and Machado (1985) proposed anotherclassification system for TMD problems. Like the earlier MPDclassification scheme, it was suggested as useful for bothclinical and research definition purposes. This system specifiedthree main categories (Table 3) and was an improvement overBell's clinical classification system. Several of the distinctionsmade by Bell in the muscle pain subgrouping were eliminated,and the disk derangement system was simplified to have threesubtypes instead of four. These nomenclature changes improvedthe utility of this system for clinical diagnostic purposes, andit was frequently utilized in case-based reports in the literature.Since Eversole and Machado' s system was dually proposed foruse in a research vein, specific inclusionary and exclusionarycriteria were included. Unfortunately, two serious flaws werepresent. First, no operational definitions for the examinationprocedures were given. Second, the stated criteria were veryspecific and sometimes exclusionary (e.g., a myogenic facialpain patient could have no joint sounds). These exclusions



VOL. 7(2) CURRENT DIAGNOSTIC PROCEDURES FOR TMD 99

TABLE 3TMD CLASSIFICATION SCHEME*

Myogenic Facial Pain:—Described as sore, tender masticatory muscles, and no joint sounds or radiographic evidence of osseous changes was

to be present.Internal Derangements:

—Meniscus displacements with reducing click and normal opening—Meniscus displacement with reducing click, with periodic locking, often with joint pain—No clicking (closed lock without reduction) and severely limited mandibular opening

Degenerative Joint Disease:—Described as TMJ sounds (crepitation) along with radiographic signs of osseous changes.

From Eversole and Machado (1985).

made it very difficult for patients to be categorized into one ofthe proposed TMD subgroups. For this system's utility to beimproved, the specification rules spelled out by Eversole andMachado would have to be modified for cases where multiplediagnoses were clinically evident. For example, the alteredrules would need to be able to deal with a single patient who hada right TMJ internal derangement, a left TMJ degenerativearthritis, and a generalized myogenic facial pain problem.Overall, the Eversole and Machado system better captured themajor domains of TM dysfunction {i.e., muscle pain, jointpain, and arthritis) than did any prior system. It was, however,not a thorough clinical categorization system, in that many ofthe less-common conditions afflicting the jaw muscles andTMJ were not described {e.g., contracture, hypertrophy,dyskinesia, or open dislocation).

The issue of how to deal with multiple diagnoses whendefining a presumably homogeneous research population hasnot yet been solved. The newly proposed research diagnosticcriteria, described in the next section, attempt to do just this(LeResche etal., 1992). In order to achieve more homogeneoussubgroups, it is likely that researchers will wish to exclude amoderately large percentage of the patients who report to aTMD clinic. Of course, depending on the research question,such subgroup specification may not be necessary.

In an attempt to refine this clinical nomenclature systemfurther and give a more complete listing of the musculoskeletalconditions affecting the jaw, Clark et al. (1989a) publishedguidelines for the diagnosis of TMDs which specified severaladditional subgroups of patients under the general umbrella ofTMD (Table 4). These guidelines were not intended as researchdefinitions and did not contain specific quantifiable criteria foreach group. Similarly, no rules were specified on how to dealwith patients presenting with symptoms from more than onesubgroup. For clinicians, however, they provided easilyrecognized diagnostic categories which were based on criteriaderived from clinical signs and symptoms.

McNeill et al. (1990) also published a detailed diagnosticnomenclature system based on guidelines produced by acommittee established by the American Academy ofCraniomandibular Disorders (Table 5). These guidelines alsogave a thorough listing of the common and uncommonconditions afflicting the TM system, although a slightly differentnomenclature was suggested. McNeill etal. (1990) suggested

where these problems could be integrated within a broader listof painful conditions put forth by the International HeadacheSociety. As with the Clark et al. (1989a) diagnostic guidelines,the McNeill et al. (1990) guidelines were not designed asresearch criteria but were directed toward giving practicingclinicians a logical and useful nomenclature for describingtheir patients. In addition to the usual clinical subcategories forTMD, a parallel diagnostic classification system, based onpsychiatric and psychological disease descriptions, wassuggested as a future model to "increase the efficacy fordiagnosis of orofacial pain disorders and TMD".

RESEARCH DEFINITIONS OFTEMPOROMANDIBULAR DISORDERS

Epidemiologic Indices forTemporomandibular DisordersHelkimo (1974a,b,c) published an epidemiologic index, withfive commonly observed physical signs and symptoms (Table6), to score what was then called "functional disturbance of themasticatory system". The primary difference between Laskin' sMPD definition (1969) and Helkimo' s index was that the latterwas developed specifically as an epidemiologic surveyexamination for investigating the prevalence of "global" TMDsand the need for treatment. Applying this index to one of thefew probability-based study samples, Helkimo (1974c) reportedthat only 18% of the population he studied was free of all signsand symptoms, and that as many as 47% had at least one severeTMD symptom. Since the percentage of the population whichvoluntarily seeks treatment for TMD is much lower {i.e., closerto 5%), many challenged the above figures as overestimatingthe prevalence of TMD in the general population. The Helkimoindex remains the most widely used scoring system in TMDresearch but is not without serious flaws. For example, theindex does not contain several key operational definitions,such as muscle and joint palpation pressures, nor does itendorse a method for scoring joint sound severity. In addition,Helkimo's index does not consider that TMD patients mightmore accurately be described for some research and clinicalpurposes by use of more specific disease subgroupings {e.g.,myofascial pain, internal derangements, localized osteoarthritis,etc.). It was never Helkimo's intent that the index be used byclinicians as a TMD quantification system for individual




TABLE 4SUGGESTED CLASSIFICATION SYSTEM FOR

DIAGNOSING TEMPOROMANDIBULAR DISORDERS*

Muscle and Facial Disorders:—myalgia—muscle contracture—splinting—hypertrophy—spasm—dyskinesia—forceful jaw closure habit—myositis disorder (bruxism)

TMJ Disorders:—disk condyle incoordination—osteo-arthritis—disk condyle restriction—inflammatory polyarthritis—open dislocation—traumatic articular disease—arthralgia

Disorders of Mandibular Mobility:—Ankylosis—Adhesions (intracapsular)—Fibrosis of muscular tissue (contracture)—Coronoid elongation—Hypermobility of the TMJ

Disorders of Maxillo-Mandibular Growth:-Masticatory muscle hypertrophy/atrophy—Neoplasia (muscle, maxillo-mandibular or condylar)—Maxillo-mandibular or condylar hypoplasia/

hyperplasia* From Clarke al. (1989a).

patient diagnosis and treatment monitoring. Indeed, Helkimoclearly stated that his clinical dysfunction index had not beentested for validity and suffered from a lack of standardizationand from "subjective effects on the part of the examiner and ofthe person examined".

In recognition of the shortcomings of the Helkimo index,additional indices for TMD have since been proposed. To date,the best was described by Fricton and Schiffman (1986), whopresented an epidemiological index, the CraniomandibularIndex (CMI), which was based on a detailed, standardizedclinical assessment of mandibular movements, TMJ sounds,and tenderness to palpation of the TMJ and masticatory andcervical muscles (Table 3). Some 62 different items weregrouped and scored as a negative or positive clinical finding toyield two composite scores (i.e., the dysfunction index andpalpation index) from which a global summary score (i.e.,craniomandibular index) could be calculated. Detailedexamination guidelines and specific scoring rules were providedin an attempt to reduce interexaminer discrepancies. Frictonand Schiffman (1987) showed excellent inter- and intra-examiner consistency when they tested the index on a

TABLESAMERICAN ACADEMY OF CRANIOMANDIBULAR

DISORDERS GUIDELINES*Congenital and Developmental Disorders:

—Agenesis—Hypoplasia—Condylosis—Hyperplasia—Neoplasia

Temporomandibular Joint Disorders:—Deviation in form—Disc displacement (with and without reduction)—Hypermobility—Dislocation—Inflammatory conditions—synovitis, capsulitis—Arthritides—osteo-arthrosis, osteo-arthritis,

polyarthritides—Ankylosis—fibrous, bony

Masticatory Muscle Disorders:—Myofascial pain—Myositis—Sprain—Reflex splinting—Contracture—Hypertrophy—Neoplasm

Note: The diagnostic outline and categorization were designed tofollow the International Headache Society's Classificationand Diagnostic Criteria for Headache Disorders, CranialNeuralgias, and Facial Pain. In particular, Category 11 of theIHS classification was expanded. The InternationalClassification of Diseases (ICD) code for each diagnosis wasalso given. All of the terms were defined, and clinicaldiagnostic criteria were listed.

* From McNeill et al (1990).

representative TMD patient sample, but the testing was notdone using a blind-to-subject-status methodology. Furthermore,the finding of high consistency between examiners was basedon a summary item score, while the individual examinationitems showed a much lower interexaminer consistency. Ideally,each item of an examination must show good consistency;otherwise the resulting summary score is suspect. Although theauthors stated that they could use the resulting scores for thedysfunction and palpation index to yield valid diagnosticsubgroups, this assumption has never been validated. Finally,the CMI incorporates palpation of extra-oral and intra-oralmasticatory muscles as well as neck muscle sites. Therefore,subjects with an identical palpation index score may havemuscle pain coming from either the neck or the jaw musclesand still be viewed as having a similar problem. Theseshortcomings make it clear that this index needs additionalmodification and validation testing by a blind-to-subject-status methodology before it is accepted as valid.




TABLE 6CLINICAL DYSFUNCTION INDEX (CDI) CRITERIA*

Impaired Range of Mandibular Movement:—Maximal opening and lateral and protrusive movements were measured and each assigned a score of 0, 1, or 5

according to stated criteria.Impaired TMJ Function:

—A score of 0,1, or 5 was based on the presence/absence of sounds, locking, or luxation and on the degree of deviationduring opening and closing.

Muscle Pain:—A score of 0, 1, or 5 was based on the presence and number of tender sites in the masticatory muscles.

TMJ Tenderness to Palpation:—A score of 0, 1, or 5 was based on the presence of tenderness and site, either lateral or dorsal.

Pain on Movement of Mandible:—A score of 0, 1, or 5 was based on the presence of pain if it occurred on one or more mandibular movements.

* From Helkimo (1974a).

With regard to the CMI's utility for clinical diagnosticpurposes, it suffers from the fact that the CMI requires asummary score to be calculated from the numerous examinationitems. The resulting score does not intuitively describe thepatient. As a result, widespread clinical use of the CMI todescribe an individual patient's diagnosis has not occurred inthe TMD literature. Indeed, neither the Helkimo index nor theCMI proved to be of great utility in clinical patient care. Thislack of utility is because practicing clinicians are not engagedin epidemiological research but are in search of an intuitivelyand easily explainable diagnosis.

New Research Definition Guidelines for TMDSince none of the previously reviewed guidelines was shownto be satisfactory as a research diagnostic guideline, or theywere never intended as research definitions (apart fromHelkimo's CDI and the CMI), a National Institute of DentalResearch conference was sponsored to help develop a set ofresearch diagnostic criteria (RDC) for TMD (Table 8). Thesenew guidelines were published in late 1992 and will undoubtedlyimprove upon the shortcomings of the prior systems. The new

RDC are separated into a clinical-examination-based axis(LeResche et ai, 1992) and a chronic-pain-disability-and-psychological-based questionnaire axis (Von Korff et ah,1992). It remains to be seen whether they will be the definitiveTMD research diagnostic criteria. This hesitation is based onthe fact that any clinical-examination-based diagnosticspecification system for TMD must be based on data whichshow that the individual component examination items are thecorrect parameters to use. For example, the new RDC proposesmuscle palpation pressure at one pound for intra-oral sites andtwo pounds for extra-oral sites (Widmer et al., 1992).Unfortunately, it appears that the level of palpation pressureand the palpation method to be used are still arbitrarily selected.Similarly, the duration of the pressure is not specified. Suchissues have been consistently overlooked in all prior researchdiagnostic methods. The use of 20 muscle palpation sites (10per side) and selection of a dichotomous (i.e., yes/no) scoringsystem vs. apolychotomous system (i.e., none, mild, moderate,and severe) are also arbitrary. Many of the proposed sites havenever been tested as sites which can be used to discriminatereliably (with 2 pounds of pressure used extra-orally and 1

TABLE 7CRANIOMANDIBULAR INDEX (CMI) CRITERIA*

Mandibular Movement:—Specific items with their own operational criteria were listed for examination and scored as either a positive (1) or

negative (0) finding (e.g., pain or limitation on active or passive jaw opening, lateral and protrusive movements,deviation or jerkiness on opening, dislocation or blocking of the condylar head, or rigidity of the jaw).

TMJ Noise:—Specific items were listed for examination under this heading and scored as 0 (negative) or 1 (positive). Each item

had its own operational and inclusionary criteria.Muscle and TMJ Palpation:

—Muscle and joint palpation procedures were described and scored as 0 (negative) or 1 (positive) for pain. Eighteenpairs of specific muscle sites were listed, including nine extra-oral sites, three intra-oral sites, and six neck sites. Thepairs of specific TM joint sites were listed, including two extra-meatal sites (i.e., lateral and superior capsule) and oneintra-meatal site (i.e., posterior capsule).

From Fricton and Schiffman (1986).




TABLE 8RESEARCH DIAGNOSTIC CRITERIA

FOR TMD DISORDERS (AXIS I)*Muscle Diagnoses:

—Myofascial pain—Myofascial pain with limited opening

Disk Displacements:—With reduction—Without reduction, with limited opening—Without reduction, without limited opening

Arthalgia, Arthritis, Arthrosis:—Arthralgia—Osteo-arthritis of the TMJ—Osteo-arthrosis of the TMJ

* From LeResche et al (1992).

pound intra-orally) between TMD and non-TMD subjects. Ofcourse, the selection of a palpation system, even an arbitraryone, to begin validity testing is essential. Before assuming thatthe new RDC are the ultimate criteria, it would be more logicalto test and compare several of the published palpation systems

which have been used in prior research. Another problem withthe proposed RDC is the adoption of terminology to describeinternal derangements which require actual dynamicvisualization of the disk to confirm that disk displacementoccurs with or without reduction. However, disk imaging is notrequired to use the terminology. It might be best to use a less-specific anatomic term {e.g., disk-condyle dysfunction orincoordination with or without intracapsular restriction) todescribe the clinical findings until confirmatory imaging isperformed. One of the major advantages in the new criteria isrules regarding how to deal with a patient who has symptomswhich would qualify him or her in several of the TMDdiagnostic subgroups. Unfortunately, this system does not yetprovide a way of scoring the relative strength of each diagnosticsubgroup when multiple attributions are made. For example,it is not clear if a patient with an occasional non-painfulclicking TM joint and severe generalized facial and jaw musclepain will be distinguished from a patient with painful, frequentclicking and one or two sites of localized jaw muscle tenderness.Of course, depending on the research question, such a distinctionmay not be necessary. Finally, a second axis of diagnosis in thedomain of pain-related disabilities and psychological disordersis proposed and described. As with the clinical-signs-and-symptoms-based axis, this proposed system will need critical

TABLE 9JAW PAIN AND DYSFUNCTION QUESTIONNAIRE*

INSTRUCTIONS: Please check the appropriate answer to the following questions.A. Jaw Pain Questions: Doesn't Unbearable

Hurt At Hurts Hurts Almost Pain WithoutAll a Little a Lot Unbearable Relief

1. Does it hurt when you open wide or yawn?

2. Does it hurt when you chew, or use the jaws?

3. Does it hurt when you are not chewing or using the jaws?

4. Is your pain worse on waking?

5. Do you have pain in front of the ears or earaches?

6. Do you have jaw muscle (cheek) pain?

7. Do you have pain in the temples?

8. Do you have pain or soreness in the teeth?

B. Jaw Function Questions:

NoMaybea Little

Quitea Lot

Almost Allthe Time

All the TimeWithoutStopping

9. Do your jaw joints make noise so that it bothers you or others?

10. Do you find it difficult to open your mouth wide?

11. Does your jaw ever lock closed so you cannot open it?

12. Does your jaw ever lock open so you cannot close it?

13. Do you have a problem with your bite being uncomfortable?

* Gerstner et al. (1990).



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assessment and validation from comparative studies with otherpsychosocial assessment instruments which claim utility aspsychological-based axes of diagnosis. While these newlyproposed research definitions are an improvement over priordefinitions, they have not yet been tested for precision, validity,or utility. Researchers attempting to use any of the availablediagnostic systems must first establish the precision, validity,and utility of the system in a more rigorous fashion than hasbeen done in the past. Undoubtedly, these and other criticalpoints can be resolved as researchers begin testing the proposedcriteria.

In summary, the definition of TMD and its various subgroupshas progressed steadily since the concept of MPD was firstintroduced as both a clinical and research definition by Laskinin 1969. Clinicians now routinely describe their patients in amore detailed fashion, and rarely is the global concept of"Temporomandibular Disorder" considered a sufficientdiagnosis. A greater understanding of masticatory musclepain, internal derangements, and arthritis problems of the TMJover the last two decades has resulted in further specificationof the TMD patient pool. Unfortunately, this specificationprocess has made it very impractical to try to have a dual-purpose diagnostic system (i.e., one that can be readily utilizedby both clinicians and researchers). The more researchers tryto define their subject population to increase their study samplehomogeneity, the less these disease specifications are able tobe used by practicing clinicians to define TMD patients. On theother hand, the currently available clinical diagnosticnomenclature systems (Clark et al., 1989a; McNeill et al.,1990) used to describe TMD subgroups are useful, intuitivelylogical, and generally consistent with patient symptomaticpresentations and so have gained widespread acceptance amongclinicians. Clinicians are not concerned with the problem offorming homogeneous subject groups. Thus, the presence ofmultiple symptoms in a single patient is not an issue. Becauseclinicians are the sole examiners, they also are not highlyconcerned with reproducibility of examination methodology.Finally, the exact criteria for the presence of a positiveexamination finding are less critical, in that the clinician canand does easily integrate the patient's history and interviewfindings in making this determination.

In contrast, there remains a lack of agreement on the exactcriteria with which to define the various TMD researchsubgroups. This is creating great problems in the researcharena, and more work is required to improve the subgroupspecification process. Researchers must address the issue ofsymptom overlap and create a system which allows multiplesubgroup attributions as well as scores specific symptomlevels when multiple signs and symptoms exist, so that therelative strength of each subgroup assignment can be assessed.As a starting point, any research diagnostic categorizationsystem must at least deal with the four cardinal clinical featuresof TMD (i.e., masticatory muscle pain, TMJ pain, TMJ noises,and restriction of mouth opening). For TMJ and muscletenderness assessment, the exact location, method, and pressureparameters must be specified. For TMJ noise and mandibularmovement assessment, the verbal instructions, sequence ofexamination, and method of measurement must also be

specified. These specifications must be based on data,reproducible, and validated as being discriminatory items.Only when such criteria are available will individual symptomand sign scores be combinable for categorizing patients intovarious TMD subcategories.

TEMPOROMANDIBULAR DISORDERQUESTIONNAIRES

A potential diagnostic aid that the health care practitionercould use to detect the presence of TMD is a brief questionnaire.In fact, the 1983 American Dental Association Guidelines onthe Diagnosis and Treatment of Temporomandibular Disordersproposed such a questionnaire (Griffiths, 1983). A specificrecommendation of the ADA guidelines was that generaldentists ought to use a brief "TMD questionnaire to help screenfor TMD problems in a general dental patient population."Unfortunately, the questionnaire published by the ADA wasnever tested for validity. A 97-item questionnaire (TMJ Scale)has been described for the purposes of detecting and quantifyingthe severity of apatient's TMD problem (Lundeen etal., 1986;Levitt et al., 1988; Levitt 1990a,b, 1991). The TMJ scalequestionnaire contains questions regarding the physical signsof TMD and also screens for psychosocial and non-TMDproblems. The negative utilitarian aspects of such aquestionnaire for screening TMD are that, at 97 items, thequestionnaire is not "brief and requires either a computer withscoring software or commercial scoring via the mail. In addition,because it includes multiple psychological questions,interpretation by a psychologist is also recommended. As aninstrument to detect psychological distress in known TMDpatients, it needs to be compared with other available methods(e.g., established psychometric instruments or psychologicalinterviews) before recommendations about its utility in thisarena can be made. The validity of the questionnaire has beenevaluated by its creators, and the instrument appears useful asan aid for diagnosis by supplying a global view of the patient'sproblems. However, a cost-benefit analysis of the questionnaireis required, and further blinded validation studies to determinethe sensitivity and specificity for TMD in a general dentalpopulation are still needed. Such studies should be performedby individuals not proprietarily associated with the instrument.

A much simpler approach to screen for TMD-related painin a general population was utilized by D workin etal. (1990)on a probability-based sample of the population. A singlequestion was asked regarding the presence of "facial ache orpain in the jaw muscles, the joint in front of the ear, or theinside of the ear in the previous 6 months (other thaninfection)." They found that 12.1% of members of a Seattle-based health maintenance organization responded positivelyto the question. As a sole criterion for the presence of a TMD,this single question is likely to identify most TMD patientswith pain. However, it would exclude a small group ofpatients with nonpainful but clearly abnormal TM function(e.g., jaw-opening restrictions, TMJ noises, or open locking).The validity of this screening question has never beenspecifically tested, and it would not necessarily differentiateamong painful conditions associated with regional structures—such as the eyes, ears, and sinuses—as well as headache and




TABLE 11SUMMARY RESULTS OF THE RELIABILITY STUDIES ON TMD EXAMINATION METHODS

Pain on palpation:

Total number of sites

extra-oral

intra-oral

neck

TMJ

all sites

Overall severity score

Individual sites:

extra-oral (mean)

intra-oral (mean)

TMJ (mean)

TMJ noise:

Detection:

palpation

stethoscope

Summary score

Mandibular movements:

Specific measurements:

Maximum opening

without pain

Maximum active

opening

Maximum passive

opening

Lateral excursions

Protrusion

Carlsson

etaU 1980

Inter

Inter

3Cv

6-14 Cv

6-7 Cv

Mandibular mobility indices:

From Helkimo Index 0.44 Sc

From Craniomandibular

Index

Dysfunction Indices:

Helkimo Index

Craniomandibular Index

Dysfunction index

Palpation index

Overall Index

Inter

0.58-0.69

Kopp andWenneberg

1983Intra/Inter

0.25/0.33 Sc

Intra/Inter

2-3/2-3 Cv

Intra/Inter

Sc 0.31-0.33

/0.16-0.30 Sc

Diunkerke Fricton and

et aU 1986a Schiffman

Intra/Inter

0.87-0.95/

0.80-0.87 r

0.47/0.35 Sc

0.54/0.50 Sc

Intra/Inter

0.96-0.98/

0.95-0.97 r

1986Inter

0.81 ICC

0.58 ICC

0.84 ICC

Inter

0.85 ICC

Inter

0.88 ICC

Inter

0.84 ICC

0.87 ICC

0.95 ICC

Stockstill Dworkin

et aU 1989 etai,1990

Inter Inter

0.91 ICC

0.90 ICC

0.94 ICC

0.37-0.70 K

0.65 K

0.61 K

0.52 K

Inter

0.62 K

0.61 K

0.68 ICC

Inter Inter

0.90 ICC

-.96 ICC

0.98 ICC

0.70 ICC

0.68 ICC

Goulet

et al.,

1993bInter

0.63 ICC

0.50 ice

Inter

0.78 ICC

0.87 ICC

0.93 ICC

0.63 ICC

Types of reliability: Intra = intra-examiner reliability; Inter = inter-examiner reliability.Statistics: Cv = Coefficient of variation; Sc = Scott's pi; r=Pearson Correlation Coefficient; K = Kappa; ICC = Intraclass Correlation Coefficient.




TABLE 12PREDICTIVE VALUE OF THE PAIN-FREE OPENING AND MUSCLE TENDERNESS RULE

ACCORDING TO PRIOR ESTIMATE OF LIKELIHOOD OF TM DISORDERS

Prior estimateof likelihood

of disease

90

80

70

60

50

40

30

20

10

PFO + OBSensitivity:Specificity:

Positivepredictive

value

97

93

89

84

77

69

59

46

27

<430.680.80

Negativepredictive

value

22

38

52

63

71

79

85

91

96

3 Muscle Score > 4Sensitivity: 0.70Specificity: 0.74

Positivepredictive

value

96

92

86

80

73

64

54

40

23

Negativepredictive

value

22

38

51

62

71

79

85

91

96

facial pain disorders not involving the TM apparatus.Considering the above limitations of a 97-item commercialquestionnaire and the potential false-positive in using asingle-question-based method, it would seem logical that abrief, multiple-item questionnaire might be advantageous inidentifying TMD. Most recently, Gerstner et al. (1990)performed research on the diagnostic validity of a brief 13-item questionnaire (Table 9). This questionnaire was modeledafter the questionnaires which appeared in the ADA (Laskinet al, 1983) and the Clark et al (1989a) guidelines. Thequestionnaire consisted of eight questions related to jaw pain{i.e., location of pain, precipitating factors, and temporalpattern of pain) and five questions related to jaw function{i.e., TMJ noises, locking, and difficulty in opening). Theresearch was conducted on TMD subjects and non-TMDcontrols. There were five possible answers to each question,ranging from 0 (no symptoms) to 4 (unbearable or constantsymptoms). The total scores for the eight pain questions andthe five jaw-function questions were used to determine thequestionnaire's sensitivity and specificity in each group, andROC curves were plotted to identify the best cut-off point fordisease presence or absence. Analysis of the data showed thatthe questionnaire reliably distinguished between the controlgroup and the TMD group, with a 96.5% sensitivity and96.4% specificity at cut-off values between 5 and 9. Theseresults support the use of the questionnaire as a supplementaryscreening tool for clinical TMD studies.

Additional research is needed to evaluate the validity of theindividual items in the brief screening questionnaire for TMD.Comparing and contrasting several brief targeted questionnaireswhich can be scored by a clinician on site {e.g., questionnairesfor headache, cervical disease, and TMD detection) might be

a useful line of investigation. Such research must also examinewhether these questionnaires can be used alone or must havean accompanying clinical examination to validate their results.

UTILITY AND VALIDITY OF CLINICALEXAMINATION METHODS

The remainder of this review will focus on the utility andvalidity of various questionnaires and examination methods todetermine or define the presence of a TMD.

Clinical Examination MethodsThe practicing clinician's "gold standard" for TMD is patientself-report in combination with a validating clinicalexamination. This combination is necessary because, at present,TMDs have no reliable histopathologic markers, a substantialsegment of the general population has one or more of thecharacteristic signs or minor symptoms, and the condition ismore or less defined as being present only when it has asubstantial impact on the patient's life or well-being. Datagathered through the traditional clinical examination indicatethat masticatory muscle and, to a lesser extent, TMJ tendernesson palpation are the most consistent features of TMD (Laskin,1969; Perry, 1969; Eversole and Machado, 1985; McNeill etal, 1990; Truelove et al, 1992). Although the data resultingfrom this examination, usually performed by fingertip palpation,are of diagnostic importance to an individual health carepractitioner, their validity for clinical research is frequentlyquestioned. No agreement exists on the number of muscle andTMJ sites that need to exhibit tenderness and how severe thesite tenderness must be in order for the presence of TMD to bedefined for clinical research purposes. Other frequentlydescribed and undefined features of a TMD are limited




mandibular motion and TMJ sounds. Regardless of the itemsselected for inclusion in the examination, the lack of validationfor these items as diagnostic discriminators has made it almostimpossible to establish a universally acceptable clinical,examination-based research definition for TMD patients.

Reliability Studies of Examination MethodsOne essential aspect of validity is the precision or reliability ofan examination procedure. It is important to distinguish betweentwo types of examiner reliability: one referring to the consistencyof each individual to perform the same task over and over again(i.e., intra-examiner reliability), and the other indicating if thesame consistency exists between individuals when makingobservations of the same variable (i.e., inter-examinerreliability). An observer's reliability reflects the precision ofthe measurement but is not an indication of its accuracy (i.e.,validity). In other words, agreement may exist, yet examinersmay be wrong when compared with a gold standard. Severalinvestigators (Table 10) have researched the reliability of theexamination methods for detection and quantification of signsand symptoms of TMD, but very few studies were appropriatelydesigned to draw any firm conclusions on the true validity ofthe current examination methods (Smith, 1977, 1981a,b;Carlsson etal, 1980; Kopp and Wenneberg, 1983; Duinkerkeetal, 1986a,b; Fricton and Schiffman, 1986; Stockstill etal.,1989; Dworkin et al, 1991; Goulet et al, 1993b). In order totest for consistency or reliability, standardization of theexamination protocol, as well as training and calibration ofexaminers, is needed to ensure that each technical step of aselected procedure is performed according to recommendedguidelines. Another prerequisite in any reliability study is thatspecific criteria be stated regarding the interpretation of anyclinical sign and symptom which requires a clinical judgment.Reliability studies must also fulfill several other basicrequirements (Chilton, 1982). Unfortunately, theserequirements were rarely complied with in prior TMDexamination studies, as pointed out by Dworkin et al. (1988)in a previous review.

Table 10 summarizes the principal features of the majorreliability studies conducted in the TMD field. Obviousdifferences in examiner characteristics and methodology makethe results of these studies, summarized in Table 11, hardlycomparable. However, the emerging consensus is that themeasurement of subjective clinical symptoms (i.e., pain uponpalpation or joint noises) is less reliable and subject to moreexaminer variability than are more objective clinical signs (i.e.,mandibular movement measurement). So far, no serious efforthas been made to determine to what extent the source of thevariability was a function of the subject's report, the examiner'smethod of examination, or the unstable nature of the symptoms.In general, the following remarks apply to all of the citedstudies except the two (Dworkin et al., 1991; Goulet et al,1993b) specifically designed to fulfill the major basicrequirements suggested by Chilton (1982): (1) Despitestandardized examination protocols, the training and calibrationof examiners were usually lacking; (2) study samples did notalways include a mixture of TMD patients and controls, andwhen they did, examiners were usually not blind to the status

of the subjects; (3) randomized assignment of subjects tocontrol for the order effect of the different examination methodswas rarely present; (4) the tendency was to report agreementdata derived from summary scores—such summary scoresgathered in a blind fashion may reflect the global severity of thepatient' s problem more than the reliability of each examinationitem comprising the score, and only with an item-by-item,blinded assessment can the weakness of the method be detected;(5) a strategy to control for the variation of signs and symptomsover time and upon repeated examination was often lacking;and (6) only a few studies expressed their results using theappropriate statistical analyses, namely, Kappa statistics andintra-class correlation coefficient (ICC).

Calibration of ExaminersTo gain more insight into the ability of examiners consistentlyto perform technical tasks related to muscle and joint palpation,Goulet et al. (1993a) conducted a study. It involved fourexaminers who were trained and calibrated to deliver on apressure algometer two different standard pressures with theirindex fingers (a high pressure between 1.5 and 2.1 kg/cm2 anda low pressure between 0.5 and 1.1 kg/cm2) and locate (within7 mm) specifically defined palpation sites on patients.Examiners were monitored over a three-month period for theirability to perform these two tasks. Overall, 89.5% of thepalpation trials were within the target pressure range. Allexaminers but one, who had 79% success, achieved an 80%success rate in all pressure-level trials. Furthermore, pairedexaminers were able to select the palpation sites within 7 mmof each other more than 85% of the time. Overall, this studyshowed that examiners were able consistently to perform thespecific technical tasks required during the experimentalpalpation examination. For research purposes, the authorssuggested calibration procedures and set criteria for acceptableexaminer performance in the assessment of muscle and TMJtenderness.

Undoubtedly, training and calibration protocols for TMDexaminers will need to be extended and refined in the future.These protocols must involve the following: (1) a reproducibilitystudy assessing consistency of other clinical examinationmethods during repeated exams of both TMD patients andcontrol subjects, as well as (2) testing of examiners' performanceover a period of time following their calibration.

Muscle and Joint Tenderness ExaminationsThere is a consensus that muscle tenderness is an importantclinical sign in myofascial pain and related musculoskeletaldisorders. Digital (i.e., fingertip) muscle palpation representsa potential clinical test, with other clinical findings, which mayhelp discriminate among subtypes of TMD patients in a selectionprocess for clinical trials. Many debates and unsolved issuesexist regarding the usefulness of muscle tenderness elicited bydigital palpation as a diagnostic aid and a major inclusionarycriterion for TMD subtypes. This is partly due to the mixedresults of reliability studies looking at examiner agreement forthe assessment of muscle tenderness (Carlsson et al., 1980;Kopp and Wenneberg, 1983; Duinkerke etal., 1986a; Frictonand Schiffman, 1987; Stockstill et al, 1989; Dworkin et al,




1991; Goulet et al, 1993b). At best, the most relevant researchreports show moderate inter-examiner agreement for thispalpation method when repeatedly tested over individual musclesites (Dworkin et a/., 1991; Goulet et al, 1993b). The level ofagreement, however, increased substantially when summarytenderness scores were derived from a clinical data set (Frictonand Schiffman, 1987; Dworkin et al, 1991). This alternativemay be worth considering if the palpation test is limited tomuscle and joint sites that have the best reproducibility anddiscriminative value. As previously shown by Dworkin et al.(1991), summary-score-to-report-examiner-agreement givesa false impression of the true reproducibilty of the digitalmuscle palpation technique, since examiner agreement overspecific items making up the summary score is rarely as good.

Recently, Clark et al (1993) looked at the diagnosticvalidity of digital palpation, using a standard force, todifferentiate TMD patients from non-TMD subjects. Trainedand calibrated examiners gathered tenderness measurementsfrom three groups of experimental subjects (i.e., control subjects,TMD clinic subjects, and tension-type headache subjects).Four masticatory muscle and two TMJ sites were tested fortenderness (0 to 4 severity scale) on each side of the head, anda composite one-sided score was produced by combining theelicited tenderness scores from the superficial and deep masseterand the anterior temporalis muscles. The palpation pressureutilized was 1.8 kg for a two-second duration. These three siteswere retained based on the findings of a previous reliabilitystudy (Goulet et al, 1993b) that digital palpation was a highlyreproducible method at these sites. With respect to muscletenderness, a TMD case was defined as the combined scorebeing greater than or equal to four. Applying this criterionusing the Jackknife method resulted in 25.8% of the controlsand 30.0% of the TMD cases being misclassified, which isassociated with odds in the range of 25 % for a false-positive or-negative test. Given the sensitivity and specificity of thissimple test, Table 12 illustrates how its use adds up to the pre-test likelihood of TMD if the test result is positive for variousclinic base rate prevalences of TMD. The composite muscletenderness score was, however, unsuccessful at discriminatingchronic temporalis region tension-type headache subjects fromthe TMD subjects, since, by sole use of this criterion, 89.7% ofthe headache subjects would have been misclassified.

In summary, with the exception of a few studies and despitethe fact that digital muscle palpation is widely used, very fewoperational guidelines are explicitly described to assist cliniciansand researchers to systematize and standardize the procedurein an attempt to enhance its reproducibility. Palpation involvesseveral steps, among which are the technical aspects of whichfingers are used, the amount of pressure applied, the site beingpalpated, and the selection of a pain measurement tool (e.g.,visual analogue score, polychotomous rating scale, or adichotomous system). While various pressures have beenarbitrarily selected by different investigator teams, this decisionshould be supported by data showing the discriminative valueof such pressure. Only one preliminary report addressing thisquestion has been published, and the results of this pilot study(Goulet and Clark, 1990), derived from pressure-pain thresholddata, suggest that the pressure currently selected by Fricton and

Schiffman (1987) and Dworkin et al (1991) (respectively, 1and 2 pounds) may be too low for muscle tenderness assessmentand may be associated with an unacceptable false-negativerate. Undoubtedly, more research is needed to specify if whole-muscle palpation presents an advantage over the palpation ofselected, specific muscle sites. It is also unclear which methodof grading severity (i.e., patient verbal report of tendernessusing a dichotomous pain scale, a multiple validated pain worddescriptor scale, or examiner assessment of patient reaction topalpation) is most reliable. All of these factors must be takeninto consideration, since it may differently influence theprecision and ultimate validity of muscle and joint pain detectionmethods. As more objective methods to detect and quantifysubjective muscle and joint pain symptoms become available,a better definition of disease state will be developed. Thedigital (i.e., fingertip) pressure method remains the currentgold standard, and any new methods must be compared with itfor all of its advantages and possible shortcomings to beidentified. Clearly, results of the reliability studies on assessmentof tenderness illustrate that research using this clinical parameterfor diagnostic discrimination of patients from non-patientsmust use a reproducible examination technique.

PRESSURE ALGOMETRY DEVICESPressure algometry has been used in several studies to measurepressure-pain threshold over specific muscle sites in normalsubjects (Jensen et al, 1986; Fischer, 1987a; Burgess et al,1988; Lest et al, 1989; Ohrbach and Gale, 1989a) and patientssuffering from musculoskeletal disorders (McCarty et al,1965; Campbell et al, 1983; Reeves et al, 1986; Fischer,1987b; Schiffman et al, 1988; Ohrbach and Gale, 1989b).Good-to-excellent intra- and inter-examiner reliability hasbeen reported for assessment of pressure-pain threshold andmuscle tenderness (Jenson et al, 1986; Reeves et al, 1986;Fischer, 1987a,b; Schiffman et al, 1988; Lest et al, 1989).Goulet et al (1993b) tested the reproducibility of pressurealgometry vs. the traditional digital muscle palpation procedureused to assess masticatory muscle and TMJ tenderness. Bothtechniques entailed application of a standard constant pressurefor a two-second period over six anatomically definedmasticatory muscle and joint sites on each side of the face. Abalanced sample of 72 subjects (i.e., 36 patients and 36 age-and gender-matched controls) were evaluated by trained andcalibrated examiners in a single-blind study design. By meansof a randomized sequence, each subject was examined twicewith each method over a two-hour experimental period. Usingsix standard verbal descriptors, the subjects self-reported thelevels of tenderness elicited by the pressure. Intraclasscorrelation coefficients varied between sites, ranging from0.22 to 0.74 for the digital method (i.e., testing interexamineragreement) and from 0.39 to 0.88 for the pressure algometermethod (testing intra-examiner agreement). Only fair agreementexisted for the middle temporalis and lateral TMJ capsule sitewhen either method was used, but the results indicated good-to-excellent examiner agreement for the two masseter (i.e.,superficial and deep) and the anterior temporalis sites, withmean ICC values, right and left, ranging from 0.67 to 0.69 forthe digital method and from 0.74 to 0.85 for the algometer




method. This study shows better examiner agreement for thepressure algometer technique, partly explained by the fact thatrepeat examinations were done by the same examiner, whoapplied exactly the same amount of pressure. Nevertheless, theresults clearly demonstrate that multiple examiners can befairly reliable using the digital palpation method when trainedand calibrated within a range of ± 0.3 kg/cm2 of a targetpressure. Furthermore, the reproducibility of either techniquewas not worse over unmarked vs. marked palpation sites whenaccurate replication of site location was considered in attemptsto explain any variability in technique.

MANDIBULAR MOVEMENT EXAMINATIONBecause limited jaw opening is frequently seen in TMDpatients, measurement of maximum pain-free, maximumunassisted, and maximum passive opening range of mandibularmovement is an essential element of a clinical examination.The gold standard for evaluation of mandibular movementremains the use of the millimeter ruler (Goulet and Clark,1990; Widmer et al, 1990), a technique that has been shownto be highly reproducible within and between investigators(Carlsson et al, 1980; Kopp and Wenneberg, 1983; Frictonand Schiffman, 1987; Dworkin etal, 1988; Alam etal, 1989;Dworkin et al, 1991; Goulet et al, 1993b). Fairly high ICCvalues ranging from 0.78 to 0.93 and from 0.90 to 0.98 werereported by Goulet et al (1993b) and Dworkin et al (1991),respectively, for the three opening measurements. This method,however, cannot be used to assess dynamic movementirregularities such as abnormal but nonrestricted pathways ofmovement. Whether dynamic movement assessment isimportant diagnostically has yet to be determined.

Extensive descriptive data on jaw movement ability havebeen gathered on patients and healthy study populations(Agerberg, 1974; Agerberg and Osterberg, 1974; Helkimo,1974a,b,c; Hansson and Nilner, 1975; Molin et al, 1976;Rieder, 1978; Solberg et al, 1979; Nilner, 1981; Gross andGale, 1983; Rieder, 1983; Heft, 1984; Nielson et al, 1988;Agerberg and Bergenholtz, 1989; Dworkin et al, 1990).However, no attempt was made in these prior studies todetermine which mandibular movement measurements, if any,can differentiate TMD patients from non-patients.

The discriminative value of mandibular movementmeasurements was recently studied by Clark et al (1993).Examiners gathered similar mandibular movementmeasurements from three groups of experimental subjects(i.e., control subjects, TMD clinic subjects, and tension-typeheadache subjects). The only measurement which reliablyseparated TMD clinic patients from control subjects was thepain-free opening. Logistic regression was used to establish arule that a pain-free opening of less than 43 mm (includingoverbite) defined a TMD case. Jackknife misclassificationestimates that use of this rule resulted in 20% of the controlsand 34% of the TMD cases being misclassified and an associatedodds of false-positive or -negative test in the range of 25%.Given the sensitivity and specificity of the rule, Table 12illustrates how its use adds up to the pre-test likelihood of TMDif the test result is positive for various prevalence rates of TMDin a clinic. Finally, pain-free opening ability was only partially

successful at discriminating tension-type headache subjectsfrom TMD subjects, since, if only this criterion were used, 36%of the headache subjects would have been misclassified asTMD cases. Future research is needed to determine whetherthe combination of mandibular movement measurements withother aspects of the examination would give a better distinctionbetween patients with TMD and non-TMD patients.

TEMPOROMANDIBULAR JOINTSOUND EXAMINATION

Joint sounds are a characteristic feature of many TMDpatients, but the simple presence of these sounds does notdefine the disease labeled "TMD", since many people havejoint sounds without any demonstrable illness. Therefore,the character, severity, and timing of the joint sound must beclinically assessed to determine if disease is present. Althoughelectronic devices have been developed to amplify andmonitor the timing of the sound and run spectral analysis ofTMJ sounds, there is still no clear gold standard for theevaluation of TMJ sounds (Widmer etal.,\ 990). This discussionwill therefore focus on the most commonly used method,which is the clinical examination using light finger palpationof the TMJ during motion, with stethoscope auscultation asneeded. Information regarding the clinician's ability reliablyto assess the various features of joint sounds is limited. In onereliability study (Dworkin etal, 1991), marginally acceptableagreement was observed for detection of joint sound associatedwith mouth opening measured by either the digital palpationor the stethoscope technique (Kappa = 0.62 and 0.63,respectively). Examiner agreement was less than acceptableduring lateral and protrusive jaw movements (Kappa = 0.30and 0.44, respectively).

In prior research, the same investigators used a splitstethoscope with double earpieces and a single diaphragm toallow two examiners to listen simultaneously to the same TMJduring repeated jaw opening (Dworkin et al, 1988). Dataanalysis revealed that a pair of trained examiners disagreed onthe type of joint noise 35% of the time, even though they werelistening to the same patient. Furthermore, consecutive pairs ofexaminers, listening successively to the same TMJ, disagreed50% of the time with respect to the timing pattern of the TMJsound detected by the previous pair of examiners. Thesefindings indicate that a common clinical diagnostic procedureto detect TMJ sounds is moderately reproducible betweenexaminers, and may not be adequately reliable for researchpurposes. It is also evident that further variation will resultwhere there are differences in examination procedures,especially where the examiners are untrained and not calibrated.

Thus far, no real attempt has been made to correlate theinterexaminer variability to any specific factors that couldaccount for variability of the joint sounds themselves. Forexample, is the variability due to examiner errors or due tochanges in the joint sound phenomena with repeated jawopenings? It is known that clear definitions for symptomsbeing observed and calibration procedures will enhanceexaminer consistency and accuracy, but this will not help if thephenomena being measured are constantly altering.

Other factors influencing joint sound evaluation include the




speed and path of the jaw movement. An inherent inaccuracyof the examination to determine the timing of a dynamicmeasure such as TMJ sounds is the fact that the use of amillimeter ruler requires a static position of the mandible. Thismeans that the subjects must try to stop jaw opening at themoment the joint sound is elicited and then hold the jaw steadyat that position so that the amount of opening can be measured.Finally, the best method for assessing the severity of the TMJsounds has not been agreed upon. Should the day-to-dayseverity be assessed as a function of the associated pain, thedegree of movement interference, the number of lockingepisodes, or the number of occurrences of the TMJ soundsduring a set time period? As further research evolves, answersto these questions will contribute to the development of newways reliably to assess TMJ sounds.

SUMMARYFor research purposes, the refinement of existing clinicalexamination methodology and the addition of more objectivemethods (e.g., algometry) to quantify subjective signs andsymptoms could benefit any study dealing with repeatedmeasurements over a period of time. Each individual item andany new method would be tested for reliability and validity bycomparing it with an acknowledged gold standard to identifyits advantages and any possible shortcomings. Unfortunately,the only current gold standard for TMD is a global clinicalexamination and history by an expert examiner, thus makingthe validation process somewhat circular. Finally, researchersmust recognize that their efforts to achieve precision andaccuracy will likely lower the utility of their eventual researchexamination for day-to-day clinical purposes.

New TMD indices have been developed to define, quantify,and score the degree of TMJ dysfunction based on clinicalexamination findings (Smith, 1981a,b;Duinkerkeeta/., 1986a;Fricton and Schiffman, 1986). Unfortunately, it is not clear ifthe resulting summary score is definitive of TMD. For example,most indices incorporate the examination of neck muscle sitesand palpation of intra-oral masticatory muscle sites frequentlyreported to be tender in non-TMD patients (Hansson andNilner, 1975; Molin et al, 1976; Solberg et al, 1979; Grossand Gale, 1983; Agerberg and Bergenholtz, 1989). As a result,the score may indicate the presence of a more generalizedmusculoskeletal disorder or may generate information that isof limited clinical value for the diagnosis of a TMD. Aclassification needs to be developed that addresses the issue ofsymptom overlap and which scores specific symptom levelswhen multiple symptoms exist.

Data on sensitivity, specificity, and predictive value of theshort questionnaires for the detection of TMD are published(Levitt 1990a,b, 1991; Gerstner etal, 1990), but further workis needed before these can be used as both research and clinicaltools to facilitate communication between both researchersand clinicians. In particular, validation of the individual itemsin the brief screening questionnaire is required, and the use ofbrief targeted questionnaires should be investigated. Researchis also required to determine whether these questionnaires canbe used alone or require an accompanying clinical examinationto validate the result.

Finally, systematic investigation can result in full knowledgeof the factors that contribute to the examiners' variability in anyclinical technique. Once the development of better standardizedcalibration procedures and examination protocols is complete,this will enhance the validity of any future research. Furtherwork is also required to understand other sources of variability,such as the consistency of TMJ sounds or patient reports, whenrecording clinical signs for research purposes. Only after validquestionnaire and examination procedures have been developedcan further research be performed to attain ultimately greaterunderstanding and the subsequent development of a valid anduseful classification system for TMDs.

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the utility and validity of current diagnostic procedures for defining

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