From Bite to Mind: TMDA Personal and Literature Review Carl Molin, LDS, Odont Dt^

Purpose: The purpose o this study was to present a personal view of the development olprevailingopinionsaboLit temporomandibuiar disorders (TMD) during the last halfccnturv' from a mechanistic to a psychosomatic concept. It also presents some hypothesesconcerning: (Hthe role of stress in the etiology of human oral parafunaions and itsrelationship to oral stereotypies in domestic animals; and (2) the pathogeneticmechanisms of masticator\' muscle pain. Materials and Methods: The basis tor this articlewas a review of personal experiences derived from clinical and research work with TMDpatients. Studies of both older and more recent literature on TMD and related disordersespeciaily in the fields of stress research, psychosocial medicine, occupational medicine,and etiologywere also used. Results: A clear line is iound in the development ot theideas on etiology, pathogenesis, and therapy of TMD, trom the mechanistic attitude ofCosten syndrome through the introduction of psychologic and psychophysical theories bythe Columbia and Chicago schools to the now increasingly accepted biopsychosocialconcept and the view of refractory TMD as a chronic pain condition. Conclusion: Theformerly dominant bite-centered therapiesincluding intraorai appliances, the effects ofwhich still are unexplainedappear to be increasingly banished to the domain ofplacebo. Hence, to an ever-increasing extent occlusal treatments are replaced byphysiotherapy and cognitive behavior therapy. The presented hypotheses may haveimplications for the understanding of the origin of oral parafunction and masticatory'muscle pain, int i Prostbodont 1999; 12:279-288.

For more than half a century one of the most con-troversial fields in dentistry has been the syndromethat generally is known as temporomandibuiar dis-order ITMD).' At times the debate has been so heatedthat it can be well illustrated by the English philoso-pher Augustus De Morgan's comment: "I don't quitehear what you say, but I beg to differ entirely withyou" (cited in McNeill).'

'Professor Emeritus, Department of Orai and law Diseases,Karolinslca Hospitai, Stockholm, Sweden.Reprint requests: Dr Carl Molin, Ludvigsbergsgatan I2.S-IIS23Stockholm. Sweden, Fax: 46 10)8 669 49 09. e-maii:carl.molin&stockholm.mail.teha.com

This article is based on a paper that was presented at the XVIthConference of the Nordic Society ot the History of Medicine,28-31 May 1997.

The aim of this article was to depict, as personallyexperienced, the development of the concepts ofTMD from a mechanistic to a psychosomatic view.In addition, some hypotheses are presented about therole of stress in the etiology of human oral parafunc-tions as compared to oral stereot\'pies in domestic an-imals, as well as the pathogenetic mechanisms ofmasticatory muscle pain.

ASurvey of TMD

Symptoms and Nomenclature

The cardinal symptom of TMD is pain. Commonsigns are clicking noises in the joint, limited openingcapacity, and deviations in the movement patterns ofthe mandible."* In addition to local symptoms TMD

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patients often report more mental distress, sleep dys-functions, and psychosomatic disorders than non-TMD controls.''-^

The disparity in opinions regarding etiology is re-flected in the many different terms applied to this dis-order.'^ Previously, for pathogenetic reasons, thephrase "temporomandibular joint" (TMJ) almost al-ways was included. Nowadays, the more neutral andAmerican Dental Association-approved term "tem-poromandibular disorder" is used most frequently. Itis, however, evident that TMD is not a single entitybut comprises several diseases ofvarying etioiogy andpathology,^

The present article, however, will consider only dis-turbances affecting the musculature, ie, masticatorymuscle pain (MMP), according to a recent classifi-cation of TMD.^ The articular diseases or disorders ofthe TMJ, eg, rheumatoid arthritis or internal de-rangements, are beyond the scope of this article,which mainly deals with conditions without demon-strable physical pathology. While conditions withorganic pathology are classified as diseases, the neu-romuscular disorders that generally lack such signsbelongto the category called illness.''^^ Sufferers ofillness seem, in contrast to diseased patients, to bemore severely psychologically distressed and more atrisk of developing chronic pain conditions.^^

Prevalence

Temporomandibular disorder is not an uncommoncondition. At a 1996 conference arranged by the USNational institutes of Health (NIH) in 1996 it was es-timated that more than 10 mi I lion Americans were af-fected.''The syndrome, however, afflicts individualsselectively. It is more frequent among those who arebetter educated and more affluent. Women constituteabout' of those who seek treatment, and the major-ity of them are in their reproductive yearsbetween20 and 40 years of age.

Thus, the sociologie aspects of the syndrome areintriguing. The first to study this problem was ArnoldFranks.''' In Stockholm he once surprised his audi-ence by open ing his lecture on TMD by projecting amap of the Pacific. Pointing to the island of Guam,he declared that the US Armed Forces had set up amedical center there that included a TM| clinic. Sincethe natives ofthe island were privy to its medical ser-vices, an additional motive was the opportunity tostudy TMD in a population unaffected by V\/esterncivilization. This project, however, proved to be acomplete failure; nota single native appeared at theTMD clinic. Instead, the majority of the patients wereofficers' wives! (Franks AST, personal communica-tion, 1968.)

History

The fact that interest in TMD has been so pronouncedduring the last half century should not deceive us intobelieving that we are dealing with an ailment that hasrecently escaped from Pandora's box. We know from5,000-year-old papyri that describe the technique ofrepositioning a dislocated TMJ that TMD existed in an-cient Egypt, Dislocation of the TMJ may certainly be re-garded as the most advanced feature of the syndromeof muscle tension and disturbed coordination thatconstitutes the most common t/pe of TMD. Besides, theancient Greeks knew the repositioning technique thatis exactly the same as the one still used.'^

For more than 2 millennia, very little happened inthis field. At the end of the last century dentistrypassed through a period of dynamic progress, espe-cially in the United States. New materials had be-come available for prosthetic purposes, and to makethe best use of them it was necessary to increaseknowledge of mandibular movements and occlu-sion. This new awareness called into questionwhether disturbances in this field might have reper-cussions for the TMJ.

Etiology

Costen Syndrome

In 1918 the American anatomist Prentiss, with the den-tist Summa, published a study ofthe dental conditionsofhumancadavers. Their study reported lesions in theTMj, which they proposed were caused by defectivebites that had caused excessive load on the joints,'^

Far more attention was attracted by the 1934 arti-cle, "A syndrome of ear and sinus symptoms depen-dent upon disturbed function of the temporo-mandibular joint," written by the American otologistJames B. Costen.^' HereGosten brought together noless than 14 different symptoms, the most importantof which were pain in and around the ears, clickingin the joints, limited jaw opening, and other move-ment disturbances. Even impaired hearing, dizzi-ness, and headaches were included in the syndromebased on experience of 11 patients. Focusing on oc-clusion as the most important factor, Costen's paperhad immense impact, and its consequences were farreaching for both patients and dentists.

Costen's Concept

Gosten's pathogenetic conceptone may be temptedto call it a pathogenic theorywas that in the absenceof molar support the powerful elevating muscles ofthe mandible could press the condyles upward and

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backward, causing damage to vessels and nerves, in-cluding the corda tympani.'~ The logical treatment,ofcourse, was to restore the vertical dimension ofthebite. If molars were lacking, partial prostheses werefitted: in dentate cases where overclosure was diag-nosed the bite was raised. This mode of treatmentspread rapidly throughout the United States and thenthe world. The success of the concept was a result ofthe advantages it offered both patients and dentists.The patients found a simple, somatic explanation fortheir mysterious symptoms, hience, they willinglyaccepted even extensive occlusal treatment. The im-portance of a somatic diagnosis for legitimizing an ill-ness is ver\' powerful, and may explain the willing-ness of patients with psychogenic disorders toundergo drastic treatment.'^ ''' For dentists, Gosten'sconcept was a stroke of fortune because it providedthem with an expanded field of activity.

If treatment of the bite did not give the desired ef-fect, it was interpreted as not having been radicalenough. In a lecture (Stockholm 1965), the late ProfSigurd Ramfjord of Ann Arbor-of whom, certainly,no undervaluingofthe importance of occlusion maybe suspected^told of an American colleague whohad had his bite raised 3 times to improve his hear-ing (Ramfjord S, personal communication, 1968). Asmentioned, "impaired hearing" was among the symp-toms included in Gosten syndrome.'' Soon after thelast procedure the apices of the mandibular incisorscould be palpated under his chin! iRamfjord S, per-sonal communication, 1968.}

Other Etiologic and Pathogenetic Tbeories

Since Costen put forth his concept an enormous bodyof literature has been published about these disorders,Costen's theory' of overclosure assumed major defectsin the bite; later the tendency was to consider evenvery minute occlusal disturbances to be dangerous.In a way, smaller disturbances were thought to beeven more pathogenic by disturbing the intricate pro-prioception and coordination, thus causing effectseven on the central nervous system.--'

As late as the 1970s this belief in the ability of oc-clusal disturbances to cause irritation was generallyembraced. One leading Scandinavian textbook atthis time stated:

The anxiety that many patients with muscular hyperac-tivity in the masticatory apparatus demonstrate may there-fora, thanks to the close co-operation between ihe reticularsystem, the cortex and the limbic system, be a consequenceof disturbances or the interocclusal morphology and ac-cordingly a secondary phenomenon. Clinically, this is notan uncommon experience.^' (Italics in original.)

Laszio Scbwartz: Pioneer for a Scientific Approacb

Gosten's theories were soon questioned, and finallydisproved by anatomists." Laszio L. Schwartz, a gen-eral dental practitioner, adopted a new approachand founded the first academic research center atGolumbia University, with a multidisciplinary col-laboration on what he called the "temporomandibu-lar joint pain dysfunction syndrome."-^ Despite thechosen term, Schwartz considered the disorders to belocalized in the masticatory muscles rather than in thejoint. Themental constitution of the patient was con-sidered to be more important than occlusal distur-bances, which play but a contributing role. The ef-fects of stress and anxiety in increasing tension in themasticator\' muscles were considered to be the basisofthe disorder. Alarming diagnoses or physiologicallyor psychologically traumatic treatment can aggra-vate the disorder.-"* In the team of medical and den-tal specialists that Schwartz assembled at Golumbia-Presbyterian Medical Genter, psychiatrist RuthMoulton played an important role in furthering theunderstanding of the significance of emotionalfactors.'"-"

More than any other author in the field of TMD,Laszio Schwartz broke new ground for understand-ing the many problems in this area. Under his guid-ance the work at the Columbia TMj clinic broughtabout a paradigm shift in understanding what causesTMD. The acceptance of Schwartz's ideas, however,was very slow. To understand Laszio Schwartz'sachievements it is necessary- to mention his devotionto the humanities, especially to the history of medi-cine and dentistr\'. He was a founder ofthe Academyofthe FHistory of Dentistry, and he managed to add acourse on this subject to the curricula at GolumbiaDental School .^ ^

The Psychophysiologic School

After Schwartz's death in 1966, the center of researchactivity moved to Chicago. At the University ofIllinois, surgeon Daniel M- Laskin, with orthodontistChariesS. Greene, founded theTemporomandibularResearch Center with a focus on psychophysiologicfactors.-" As with other psychophysiologic condi-tions (eg, hypertensionl, TMD was considered to becaused by an interaction between a physiologic pre-disposition and psychologic and physical stress. Theeffect on the individual depended on his or her abil-ity to adapt to stress. This adaptation is referred to as"coping" and has come to the forefront of researchactivity on stress and chronic pain.^^ -^ To emphasizethat the muscles, not the joint, are the most importantcomponent, the group adopted the term "myofascial

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Fig 1 The oonoept of dynamic equilibrium may be illustratedby considering the manner in which jets of water can balance aball alotl in a fountain; tlie position of the ball is not static althoughtlie ball appears to be virtually fixed in place. Teeth maintain theirpositions in a bite in a similar way.

pain dysfunction (MPD) syndrome,"^" which hadbeen introduced in medicine for similar disorders byJanet Travell et al.^^

In conformity with Ruth Moulton, parafunctionswere seen as subconscious attempts to work off psy-chic tension. The fatigue and pain spasms producedin the masticatory muscles by such efforts, especiallybruxism, were thought to bring about, maintain, andeven aggravate the symptoms.^ Thus, the groupshared Travell et al's opinion that muscular overex-ertion produces a vicious circle." This theory hasproven to be erroneous'^; the disorders seldom getworse if they are not fixated by improper treatment.Moulton's view of the relationship between symp-toms and psychic tension, however, holds true andwill be considered later in this article.

Regarding occlusai factors, the opinion of theChicago group was at least as negative as Schwartz's.One example is the farcical, but also to some extentseriously intended "American Non-EquilibrationSociety" that Daniel Laskin founded in 1977. (Itwasa great honor to have been appointed one of its 12fellows.) The barb was aimed at the "AmericanEquilibration Society," which by that time was verymechanistic.

Occlusion and Bruxism n the Etiology of TMD

Costen posited that the cause of the syndrome wasin the bite, and consequentiy the treatment ought tobe directed against it.'-' Bruxism or other parafunc-tions, however, were not mentioned in his article. Asalready mentioned, both Schwartz and Laskin re-garded occiusal factors as fairly unimportant. Whatthe patient does with his or her bite was consideredmore important than how it looks.

Among dentists, however, resistance to this notionwas considerable. Occiusal treatment, equilibration,and orthodontic and/or prosthetic reconstruction be-came the fashion. The ideal occlusion and articula-tion of a complete denture became the object, evenfor "prophylaxis."" The American EquilibrationStjciety set the tone, and among occlusion-fixatedpropagandists, Drs Peter Dawson and Nathan Shoremay be mentioned.^"'^^ Finally, this policy becameso widely accepted that it brings to mind MarkTwain's statement: "Ifyour only tool isa hammer, youmay treat everything as nails."

How Do Occiusal Disturbances Arise?

It has been proposed that the noniatrogenic occlusaidisturbances often observed and subjected to treat-ment are not tbe cause o, hut are instead caused by,parafunctional activity,^'^^The positions of the teethin the occlusion are not stable; they are determinedby the dynamic activity of the oral environment.The requirement for keeping the teeth in unchangedpositions is that the sum total of all forces actingupon them is constant. These forces may include theocciusal and articulating ones as well as the pressurefrom surrounding tissues, ie, the lips, cheeks, andtongue (Fig 1 ). When such an equilibrium exists, noperceptible movements take place, and, conse-quently, the teeth rnaintain their positions for longperiods of time. If equilibrium does not exist, theteeth are driven by the acting forces into new posi-tions, where they often constitute what is called oc-ciusal disturbances. It is then futile to treat the oc-clusion without taking the causes of the patient'sbehavior into consideration.^'' The common expe-rience of the nonlasting effects of equilibration sup-ports this opinion. The disturbances that are elimi-nated often recur or new ones arise.^''^^

EMG Studies

In 1961 Sigurd Ramfjord published a study that prob-ably has been more influential than any otherto strengthen the doctrine of the importance ofocclusion.^^ Studying conscious experimental sub-

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jects, he reported that occlusal adjuslment could re-duce eleciromyographic (EMC) activity. There was,however, rno control group, eilher of an active (treatedwith placebo) or passive (on a waiting list) nature.

In a sur\'ey, Clark and Adler**" state that there isneither experimental nor epidemiologic evidenceot the capability of premature contacts or other oc-clusal disturbances to produce bruxism during sleep,nor is there evidence for the cessation of such activityif the interferences are removed. Moreover, recentstudies indicate that during rapid eye rTiovement(REM), sleep receptors, eg, in the periodontium, arenot functioning."'^

The tendency in recent reviews of bruxism is to di-minish the role of local factors and to emphasize acentral genesis.-'--'^ The results of Ramfjord's studytherefore are not without objeaions applicable tosleeping subjects. Furthermore, when dealing withconscious subjects the effects of placebo or nocebofactors are difficult to exclude.-'"' In addition, thevalue of EMC investigations for clinical purposeswas called into question in a study demonstrating thatincreased rest activity- does not necessarily mean thatthe patient experiences muscle pain "'^

Parafunctions and Stereotypies

Moulton's opinion of parafunctions as an outlet for in-ternal tension and stress receives support from an un-expected sourceour domestic animals. Cattle ranch-ers and veterinarians are well acquainted with thephenomenon that animals under stress engage in para-functional activities, referred io in veterinary termi-nology as "stereotypies.""'^ Cows manifest these sterec-typies by rolling of the tongue (Fig 2], horses bycrib-biling, and tethered pigs by biting on the chain (insome parts of the world tethering of pigs in barns is stillallowed)."*' Particularly frequent is tongue rolling inheifers when they are tethered in a cow shed duringthe autumn months. During the summer they graze for8 to 10 hours a day and ruminate for nearly as long.Once confined, they receive their feed calculated andportioned out by a computer, and devour the fodderin barely 45 minutes. After ruminating rapidly, theyhave nothing meaningful with which to occupy them-selves and therefore begin rolling their tongues.

In collaboration with the ethologist Dr Ingrid Redboat the Swedish Universityof Agricultural Sciences, anarticle comparing human parafunctions with stereo-typies in domestic animals is under preparation.

Psychologic and Psychosocial Factors in TMD

During Schwartz's lifetime his pioneering clinical andtheoretical achievements were not fully recognized.

Fig 2 When undei stress animais can develop so-calied eralsterectypies, which correspond to human oral paratunctions.Shown here is a heifer pertorming tongue rcliing' after being teth-ered after the end of the grazing season. (Repnnted by pennis-sion ot Bedbo.''")

Later, however, in pace with the developing knowl-edge in the wide and complicated fields of stress andchronic pain, Schwartz's concepts increasingly gainedcredence, while the belief in the importance of oc-clusal faaors correspondingly has lessened.

Even though Schwartz himself did not use the term"biopsychosocial," all of his aaivitles were character-ized by this view. Schwartz's research work has chieflybeen carried on by his pupil Joseph J.Marbach. In a cas-cade of articles he has argued that psychosocial factors,not the state of the occlusion, should be the guidingprinciples for therapy. (For example, see Marbach.^ '^ )His severe criticism of the prevailing treatments, di-rected at occlusal factors, has caused colleagues to con-sider him the most dangerous dentist In Americanotewellnot for patients, but for dentists!

For obvious reasons this vexation is easily under-stood. Studies show that the great majority of cl iniciansin the United Statesand around the worldstillconsider bruxism caused by occlusal anomalies to bethe single most important factor in TMD.''^'^Pecuniarily, it would certainly not be a small changeto modify this view. A 199S article in the journal ofthe American Dental Association estimated ^htt$^ bil-lion was spent annually in the United States on pro-ducing 3.6 million splints.^'

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Bruxism

In clinical studies the reported prevalence of bruxismvaries between 6.5% and 88%, while the figures inepidemioiogic studies generally are lower.''^ Thevalidity ofthese assessments has been questioned byMarbach andothers, who consider that patients havebeen influenced by their dentist's attitude.^ '^^ "* As ithas been all butaxiomatic that bruxism is the crucialfactor in TMD, the dentists take for granted that thepatient is a bruxist. Consequently, they influence thepatient by their explanations and leading questionsto believe in and concede to such activity. Moreover,there is no reliable method for determining whetherwear facets are caused by bruxism or by otherfactors. "-5^

Other Parafunctional Activities

The concept that bruxism is the dominant factor forcausing TMD has had such impact that other para-functional activities have been totally eclipsed.Bruxism is just onemaybe not even the most dele-teriousof the parafunctions in which the mastica-tory system can be engaged. Examples of such prob-lematic habits are tongue thrusting and sucking andbiting on the lips and cheeks.

In bruxing the working mode of the muscles isdynamiclie, they alter their length), while in pressingit is static, isometric, tivcn more deleterious isantagonistic tension, that is, when groups of muscleswith different tasks counteract each other. The phys-iologically most noxious effects, however, are causedwhen muscles work eccentrically, that is, when theyare elongated during simultaneous contraction.^^^'' Inthis type of action the forces within the muscle mayexceed the strength ofthe connective tissue, resultingin microruptures, edema, and pain.^^'^^ An illustrationis the well-known fact that climbing downhill causesmore stiffness and aching than climbing uphill.

The lateral pterygoid is especially vulnerable in thisrespect. Besides being the prime mover of protrusionand laterotrusion, it also acts as a stabilizer of both themandible and the meniscus.^''^^ During times of stress,it probably is as common to tense the masticatorymuscles antagonistically as it is to bite together or tobrux. Certainly many of us have noticed how a patientduring history taking tenses the masticatory musclesand moves the jaw to one side without biting togetherwhen we happen to touch upon some emotionally del-icate topic. The force that the lateral pterygoid can de-velop in such isometric or negative contraction wouldbe sufficient to produce pain. Eurthermore, the upperbellyofthe lateral pterygoid is exceptional because ithas no antagonistic muscle. It protracts the articular

disc, but the returning movement is carried out by theelasticity ofthe connective tissue that joins the disc tothe dorsal part of the articular fossa. IHyperactivitymay be responsible for fatigue and disruption of thisconnective tissue, which in turn can lead to anteriordislocation ofthe meniscus.'^ ^

The Origin of Muscle Pain in TMD

No satisfactory explanation of the muscle pain inTMD has so far been presented. The most promisingexplanation so far was proposed by Widmer.''^ EHesuggests that the cause of masticatory muscle pain issimilarto that of angina pectoris, ie, because of localdisturbances in microcirculation. This gives a credi-ble explanation ofhow but not why pain develops ina muscle when it is producing only a small portionof its maximum voluntary force. Erom quantitativeEMCJ studies we know that the forces in such activi-ties are rather moderate.''^'^'''^^ Also, in the related dis-order of tension-type headache recorded EiVlG levelsare not very great.^^

By drawing experiences from another field, occu-pational medicine, it may be proposed that TrMD hasso much in common with some vocational disor-ders, for example shoulder-neck complaints, that itmay be justifiable to regard them as branches ofthesame tree. Strong support for this view can be derivedfrom the fact that psychosocial conditions have beenshown to be mure important than physical strain inproducing symptoms,'''^'^^

At moderate loads, it is the length of time ratherthan the level of muscle activity that is the most im-portant factor in pain.^'' The reason for this is thatthe activation of individual motor units takes place insuch a fixed order that the same motor units are al-ways recruited first.^^ ''^ When the force is reduced,the motor units are disengaged in reverse order. Thismeans that a few muscle fibers are heavily loaded fora long time even if the entire muscle is only slightlyloaded. The appropriate name "Cinderella fibers"has been suggested for these hard-working units.'''

The fact that muscles can be activated by psychicconditions is an old experience that has had new ap-plications in sports. When an athlete mentally pre-pares for an activity by imagining the movement pat-tern, the appropriate muscles increase theirperformance to some extent.''^''^ An observation thatcorroborates this effect is that no difference in EMGactivity was found between physical pain producedby injecting the masseter muscle with hypertonic (.5%)saline and "sham" pain, ie, pain evoked by imagin-ing pain.^^ Moreover, studies of occupational work sit-uations demonstrate that emotional and environ-mental factors, ie, psychosocial conditions, are

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capable of producing increased unconscious muscleactivity.''''

In the facial muscles, those of facial expression aswell as those of mastication, psychic and especiallyemotional conditions are particularly prone to man-ifest themselves.' " '^ The face is our facade, which weunconsciously try to keep unaffected by tensing themuscles ofthe face and aw. In antagonistic tension,as mentioned above, some motor units may remainactive for such a long time that pain is evoked.

The time of recovery between periods of activity isimportant. When a muscle works, metabolites accu-mulate and the balance of Na+, K*, and Ga"^ is dis-turbed. IntracellularK* decreases, while extraceliularlyit increases. This may act on free nerve endings andcause pain."" Impaired microcirculation in the musclefibers and/or in the vessels that supply the nerve maycontribute. To elucidate the problem, however, moreresearch is needed, especially on the conditions in sep-arate muscle fibers. Research involving the separatefibers is possible using ultrathin needle electrodes.^^

Why Does the Belief in Occiusai Etiology Survive?

The main reason for the continued confusion aboutthe etiology of TMD is the fact that in most individ-uals, it is possible to identify some "bite disturbance"and often also some kind of dysfunction, even whentheydonot have any complaints, A comparison withother bodily conditions may be worthwhile; howmany individuals have a perfect gait^ Analogously,should those who do not have a perfect gait beequipped with arch supports?

In a discerning article Nigel G. Clarke once madethe critical comment that

the masticatory system mus! either be unique in thebody's evoluiionary development in its failure to fulfillits function profierly or else our comprehension of thesystem has mistakenly led us to describe as abnormal-ities conditions tbat in fact may be normal and play norole in bruxism and

Apparently Clarke is alluding to those epidemioiogicstudies that overrate the occurrence of occiusai dis-turbances and symptoms: these studies were also se-verely criticized by Greene and Marbach.^^ In recentyears, however, it is obvious that a more realistic at-titude has emerged.^^-^^ Especially important is thatthis more matter-of-fact assessment also includes the

Treatment

Given the high prevalence of symptoms and signsof TMD in epidemioiogic studies and the considerably

lower rate of treatment seekers, it may be concludedthat most of those affected by TMD recoverspontaneously. 5tudies of treatment outcome showthat between 70% and 90% improve or get well irre-spective of the treatment method, and no particularprocedure has proven to be superior to any other oreven to placebo.'^^^-^' Thus, every dortor can assertwithout risk that it is just his or her method of treatmentthat worksat least in their hands. After all, the mostimportant consideration is that irreversible aaions beavoided.^^ Such measures may increase the risk thatthe patient's bite will become fixatedor even expe-rience what Marbach calls a "phantom bite" and thusbecome a chronic pain case.^-

However, as in other psycho physic a I disorders, thereis a considerable minority of patients who fail to re-spond to the conventional physically aimed therapyand continue to suffer from persistent or recurring painand disability.^ '^^ "* Gmcial factors behind a negative out-come seem to he psychosocial faaors such as depres-sion, hypochondria, an extemal locus of health control,abnormal illness behavior, and lack of emotional sup-port resulting in impaired coping capability.^^^^^ Thus,for these patients treatment ought to aim more at psy-chosocial factors than at physical ones.^^"* This ap-proach is corroborated by the fact that successful treat-ments are more effective against symptoms, eg, pain,than against clinical signs ofthe disorder.^ '^^ ^

At a 1996 treatment conference arranged by theNIH, a recommendation was given that disorderssuch as tension-type headache and TMD be treatedwith tension-relieving actions, including relaxationand counseling with information about the disorderand its background.'^ The importance of reassur-ance cannot be overestimated. "The Doaor is themost potent drug," as the Hungarian-British psycho-analyst Michael Balint expressed it.'' These meas-ures may suffice to decrease stress and anxiety andalleviate the symptoms.'^ Very important, however,is that this strategy is applied as early as possible,preferably by the first care provider.

For patients who nevertheless develop chronic dis-order, the general rules for treatment of chronic painshould be applied. For developing such strategies, thelate Dr lohn Bonica at the University of Washingtonin Seattle probably has contributed more than anyoneelse. His deep devotion was based on experience withpatients during and after the war in the Pacific.'"' Hewas also a founder ofthe International Association forthe Study of Pain. Nowadays, treatment at special paincenters is organized in the form of pain schools witha multidisciplinar/ approach.'^ Gognitive behavioraltherapy plays an important role in increasing the pa-tienf s awareness of his or her personal mode of reac-tion and its underlying causes.''*'"^5 Even if treatment

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cannot fully remove the pain, it may help the patientto cope and therefore alleviate suffering.'^^

It is logical that one ofthe most active TMD researchgroups is connected with the University of Washingtonin Seattle. Under the leadership of Dr Samuel F, Dwor-kin its activity has principally been devoted to psycho-social problems in connection with TMD and otherchronic pain conditions. A further area of focus hasbeen the development of standardized diagnostic cri-teria, primarily for research purposes on TMD.^ Theclassification system (Research Diagnostic Criteria forTMD, RDC/TMD) contains 2 axes: one consisting ofphysical TMD conditions and one concerning pain-re-lated disability and psychologic status. A recent studyindicates the capacity ofthe RDC/TMD to predict whichpatients are at risk of developing chronic disorders.^^

Looking back, the mechanistic etiologic ideas thattransferred the treatment of TMD from medicine todentistry seem very far away. Looking ahead, it is ev-ident that dental training must be directed toward amore comprehensive medical knowledge, especiallyincluding a more phychosomatic view that will helpdentists understand the etiology and natural history ofTMD; this will allow them to treat sufferers of these dis-orders. Put simply, the focus must be shifted from thebite to the mind.

References

1. Greene CS.MyofascisI pain syndrome: Noniurgical trcaimert.In: Sarnat BS, Laskir DM (eds). The Temporomandihular loint.Springfield, HI: Charles C Thomas, 190.

2. McNeill C. Vive la diffrence leditorial|. J Orofac Pain 1996;10:197-198.

3. Dworkin S, LeResche L. Research diagnostic criteria for tem-poromandibular disorders: Review, criteria, examinations andspecifications, critique. J Craniomandih Disord Facial Oral Pain1992:6:301-355.

4. Kydd W. Psychosomatic aspecls of temporomandibular joint dys-funtl ion. I Am Dent Assc1959;59:3I.-44.

5. Molin C, Studies in Mandibular Pain Dysfunction Syndrome|thesis|. Stockholm: Kiirolinska Institute. Swed Dent] 1973 (suppi41.

6. Marhacii ||. Candidate risk factors for temporomandibular pairand dysfunction syndrome: Psychosocial, health behavior, phys-ical illness and injury. Pain 1988;34:1 39-151.

7. Bealon R, Egan K, Nakagawa-Kogan H, Morrison K. Self-reportedsymptoms of stress vi-ith temporomandihular disorders:Comparison 10 healthy men and women. I Prosthet Dent 1991;65:289-293.

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Literature Afistract-

A meta-analysis of EMG biofeedback treatment of temporomandibuiar disorders.

How efficient is electromyographio (EMG) bioteedback in treating temporomandibuiar disonJers(TMD)? This study reviewed tbe available literature from the last 3 decades to eyaluate treat-ment etficacy and estimate treatment etfect sizes. A iiterature search located 13 studies ot EMGbiofeedback treatment tor TMD patients. 6 controlied, 4 comparative treatment, and 3 uncon-troiled triais. Patients had been screened tor or diagnosed with myofascial pain disorder. Threetypes of outcome ot EMG bioteedback training were examined: giobai improvement, patient-reported pain, and clinical examination findings. Meta-analytic methods were used to estimatethe magnitude ot EMG biofeedback treatment effeots tor these 3 types of outcome. Foliow-updata were available tor 8 of the 12 bioteedback trials. Six of the triais oombined biofeedbackwith stress-m an age ment training. Five ot six controlied studies with EMG biofeedback trainingwere superior to no treatment or psychologic placebo controls tor at least one ct the three typesof outcome. Data from 12 studies contributed to a meta-analysis of pretreatment to postlreat-ment etfeot sizes tor EMG bioteedback treatments. Mean etfect sizes for both reported pain andclinical examination outcome were larger for bioteedback treatments than tcr control conditions.For example, 69% of patients who received biofeedback were rated as symptom free or signifi-cantly improved, compared with 35% of patients treated with a variety of placebo interventions.Foilow-up outcomes for EMG bioteedback treatments showed no deterioration from posttreat-ment ieveis. The conciusions of this meta-anaiysis support the etiicacy of EMG biofeedbacktreatments for TMD. However, the available data tcr analysis were limited in extent.

Crider AB, GlarosAG. JOfoiac Pain 1999;13.29-37. Relerences: 44. Reprints; Dr Ai an Gla ros, 650 East251h Street, Kansas City, Missouri 64103. Fax: 816-235-2157. e-mail: giarosa@umkc.eduAW

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