temporomandibular joint soft-tissue pathology, i: disc abnormalities

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emporomandibular Jointoft-Tissue Pathology, I: Disc Abnormalities

rancesco Molinari, MD,* Paolo Francesco Manicone, MD,† Luca Raffaelli, MD,†

enzo Raffaelli, MD,† Tommaso Pirronti, MD,* and Lorenzo Bonomo, MD*

The internal derangements are the most common noninflammatory abnormalities of thedisc, observed even in asymptomatic subjects. Because the temporomandibular jointshows large adaptative and compensatory mechanisms over dysfunctional disc motion,these disorders may be asymptomatic or minimally evident for a long time. A careful clinicalevaluation, reinforced by imaging findings, should help differentiate asymptomatic de-rangements from painful conditions that may require treatment.Semin Ultrasound CT MRI 28:192-204 © 2007 Elsevier Inc. All rights reserved.

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he temporomandibular joint (TMJ) is a diarthrodialjoint, formed by the squamous portion of the temporal

one and the condyle of the mandible. These two osseouslements are enclosed into a fibrous capsule and articulateith each other by an interposed disc of connective tissue

Figs. 1 and 2).1-3 The disc is fixed to the articular capsule andhe lateral margins of the condyle. The joint cavity is thereforeivided into an upper and a lower compartment. A synovialembrane lines the inner side of the capsule and disc, except

or the articulating surfaces. Synovial fluid produced by thisining membrane fills the joint compartments.

The TMJ is responsible for all movements of the jaw, whichake place in different orthogonal planes and around multiplexes of rotation. In these movements, the articular disc playsmajor role in compensating the incongruities of the articu-

ar surfaces. In the mandibular opening-closing movement,or instance, the condylar head rotates and translates relativeo the temporal bone with a simultaneous gliding of the discFig. 3). Several theories have been proposed to explain theechanism that coordinates the disc-condyle complex dur-

ng jaw movements.4 The biomechanical properties of theisc are largely involved in this coordination.5

iomechanical Properties of the Discechanical loading of the TMJ occurs over highly incongru-

nt articular surfaces and limited contact areas. If loading was

Department of Bioimaging and Radiological Sciences, Catholic Universityof Rome, Italy.

Institute of Clinical Dentistry, Catholic University of Rome, Italy.ddress reprint requests to: Francesco Molinari, MD, Department of Bioim-

aging and Radiological Sciences, Catholic University of Rome, L.go F.
nVito n. 1, 00168 Rome, Italy. E-mail: [email protected].
92 0887-2171/07/$-see front matter © 2007 Elsevier Inc. All rights reserved.doi:10.1053/j.sult.2007.02.004

ot compensated by the TMJ disc, the nonuniform distribu-ion of mechanical stress during jaw movements would beeflected directly over the articular surfaces, leading to carti-age damage. Peak loads are normally absorbed by local de-ormations of the disc, occurring in the contact areas with therticular surfaces. As the movement of the TMJ proceeds,hese deformations involve progressively different portionsf the disc. The result is a dynamic structural adaptation thatpreads the mechanical stress over larger surfaces.5,6 The na-ure and extent of this adaptative response depend on theiomechanical properties of the disc and the forces acting on

ts molecular structure.Several investigators have reported that the local concen-

ration of collagen, elastin and proteoglycans, and the orien-ation of these molecules into the extracellular matrix vary inhe different portions of the disc.7-9 Because of the inhomo-eneous distribution of macromolecules and fluid in the con-ective matrix, the disc expresses region-specific viscoelasticroperties.10 Stiffness, strength, permeability, and otherhysical properties vary from the anterior to the posteriorand and in both lateral zones. Thus, each region of the discesponds to mechanical loading with a specific type of localeformation. These plastic changes are considered adaptativeesponses to the different mechanical stresses experiencedocally (ie, compression, tension, or shear). They also ensurehe physiological coordination of the disc-condyle complexuring jaw movements.The equilibrium between mechanical forces acting in the

MJ and adaptative responses of the disc may change duringife. Mechanical loading has a continuous influence on theomposition and behavior of the disc. Although the mecha-ism is not clear yet, a modulation of the synthesis of con-
ective tissue has been suggested.11-15 Similarly, age-related

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TMJ soft-tissue pathology 193

hanges of the mineral and macromolecular components ofhe disc cause variations of its viscoelastic properties.16-19

Trauma and other pathological conditions usually pro-uce more extensive structural changes, involving also otherissues of the TMJ. If these pathological changes do not in-olve primarily the disc, they may still have influences on itsiomechanical behavior.20 For instance, a pathologic agentay alter the molecular composition and the properties of

he articular cartilage, increasing the roughness of the artic-lar surface.21 The higher shear stress experienced locallyay induce changes on the viscoelastic properties of the disc.his adaptative response compensates the new loading con-itions. However, if mechanical stress overcomes the adap-

Figure 1 Schematic (A, C) and magnetic resonance T2*-win the coronal (A, B) and sagittal (C, D) view. Two ostemporal bone (GF and E) and the condylar head of the mand temporal bone. In the closed-mouth position, the coThe articular eminence (E) forms the anterior wall of thjoint during function. The entire articular surface of thdegree of convexity and concavity. The condylar headrounded to flattened superior surface. An articular discthe coronal view (A, B), the inferior, concave surface of tsuperior surface of the disc is slightly convex, fitting the cattached to the medial and lateral poles of the condyleattachments increase the medial-lateral stability of the dinserted between the anterior and posterior margins of tthe disc-condyle complex during function. (Color versi

ative capabilities of the disc, degenerative changes may oc- m

ur even on the osseous elements of the TMJ, because ofncompensated loading.Such interactions and reciprocal influences, mediated by me-

hanical loading, are common among the components of theMJ and may reach considerable complexity. In fact, concurrentith an altered disc function, histological changes have beenbserved in other elements of the TMJ. These changes will beentioned in dealing with disc abnormalities.

isc Abnormalities: Internal Derangements

efinition and Pathophysiologyhe internal derangements are the most common noninflam-

d (B, D) images of the temporomandibular joint (TMJ),elements form the TMJ: the squamous portion of thele (Co). An articular capsule (JC) attaches to the condyleCo) is housed in the bony roof of the glenoid fossa (GF).id fossa and represents the load-bearing portion of theoral bone (GF and E) is saddle shaped with a variableso have a significant variation in size and form, with anterposed between the articular surfaces of the TMJ. Inmatches the articular surface of the condylar head. Thesurface of the articular fossa. The articular disc is firmlycollateral, disco-mandibular ligaments (DML). These

ring condylar movements. Similarly, connective fibersand the capsule (1, 2) participate actively in stabilizinggure is available online.)

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he disc

atory abnormalities of the TMJ, being observed even in

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194 F. Molinari et al.

symptomatic subjects. The term derangement refers to anlteration in the normal pathways of motion of the TMJ thatargely involves the function of the articular disc. Therefore,hese alterations have been also referred to as disc derange-ents. They differ from degeneration because the quality and

tructure of the TMJ tissues are not necessarily altered. Thenflammatory and degenerative disorders of the joint are clas-ified in a different pathological group (ie, osteoarthritis).owever, much overlap in the clinical course of these twoisorders has been reported.22 The articular surfaces may be

Figure 2 Schematic (A, C) and magnetic resonance T2*-wmandibular joint in the sagittal view, in closed- (A, B, Dis a biconcave (bow tie) or sigmoid-shaped structure, mfibrocartilage, interposed between the temporal bone anparts: an anterior band (AB), a thinner avascular intermedisc in these three parts differs in the medial-lateral diremechanical loads also influence the molecular compositietc.). The AB prolongs anteriorly into connective fibersplane. Medially, some of the fibers of the AP are continuprobably with the fibers of the masseter and temporal mand vascularized attachment, the retrodiscal tissue (RT)and can be divided into temporal, intermediate, and cretrodiscal lamina (1) attaches to the most posterior areaposterior region of condylar neck. Between these twoinnervated by sensory fibers. The shape of the disc and itduring jaw movement (C) to adapt to the articular surfposterior attachment increases significantly when the dstretching of the elastic fibers promotes the inflow of blversion of figure is available online.)

nterested by degeneration with a normally located disc.23-25 f

egenerative changes of the TMJ may also occur because ofechanical derangements of the disc.Many etiologic factors have been proposed to explain disc

erangements. Traumatic events may cause stretching, tear-ng, or rupture of the disc, lateral ligament, or capsule. Whenleeding occurs, fibrotic or hyperplastic intra-articular reac-ions may lead to restricted mobility and pain.26 Less obviousnjuries of the TMJ may also cause soft-tissue responses andead to permanent intra-articular changes, with long-termffects on the disc function. However, several studies have

ed (B, D, E) images of the articular disc of the temporo-pen-mouth position (E). The articular disc or meniscusp of fibrous connective tissue with varying amounts of

andible (see also Fig. 1). The disc is divided into threene (IZ), and a posterior band (PB). The thickness of the

according to a differential loading pattern. Site-specifice disc (the distribution of proteoglycans, cartilage cells,which insert on the anterior margin of the preglenoidth the superior head of the lateral pterygoid muscle and. The PB continues posteriorly into a richly innervatedT is a fibroelastic structure covered by a synovial layerr layers or laminae. The temporal lamina or superiorglenoid fossa. The inferior lamina (2) is attached to the

ae is a loose connective tissue (intermediate layer, 3)ct areas with the articular surfaces continuously changef the mandible and temporal bone. The volume of thedyle complex moves anteriorly (D and E), because theto the vessels-rich intermediate layer of the RT. (Color

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A laxity of the ligaments of the TMJ has also been related toisc derangements.29-31 However, the prevalence in the gen-ral population of disc derangements appears not to matchith that of joint laxity. Controversial data have been alsoublished on this issue.32

Bruxism has been also reported as a potential cause of discerangements, since compressive overloading may alter theonnective tissue of the TMJ.33,34 Bruxism is also frequentlyssociated with various temporomandibular disorders. How-ver, a causal relationship between this nonphysiologic be-avior and disc derangements has not yet been proven.35

Changes in the composition of the synovial fluid may increasehe intra-articular friction, leading to unstable disc motion.36,37

hese biochemical changes may also affect the joint lubricationnd nutritional requirements of the articular surfaces.

An improper activity of the lateral pterygoid muscle (LPM)

Figure 3 Schematic representation of the TMJ during phto l). Jaw opening occurs with a rotation and anterior trand disc move forward simultaneously (disc-condyle copreglenoid plane, beyond the apex of the articular emineband and the intermediate zone of the disc, whereas thesame time, the temporal layer of the retrodiscal tissue is(e to i). During jaw closing (h to l), the movement of theThe lateral movements of the mandible are rare duringtion (eg, tooth grinding).

uring TMJ motion has been also related to disc derange- fi

ents.38 Morphologic changes of LPM, such as hypertrophy,trophy, or contracture, have been found in patients withnterior disc displacement without reduction.39 A higherropensity toward anterior disc displacement has also beenound in subjects in which the LPM attaches to the disc butot to the condyle.40

Independently from the etiologic factors and concurrentnfavorable conditions, disc derangements occur when theunction of the disc is compromised. An initial adaptativeesponse, triggered by overloading, induces structuralhanges in the TMJ. This is a slow but continuous process ofodeling that involves all the elements of the TMJ, within

issue-specific limits. Although physiological changes occurn the disc, its ability to remodel is lower than that of otherissues of the TMJ, such as the capsule, capsular ligaments,nd retrodiscal tissues.41 Decreased vascularity and extensive

ic opening-closing movement of the mandible (from an of the condyle of the mandible (a to c). The condyle

). At maximal jaw opening (g), the condyle reaches thethis position, the condylar surface contacts the anterior

ior band is stretched over the articular eminence. At thed against the fossa, whereas the condylar layer loosensondyle complex is the exact reverse of the opening one.g. They are detected more frequently during parafunc-

ysiologanslatiomplexnce. Inposterpressedisc-c

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issue for continuous compression and shear.42-44 These ad-ptative changes can also have mechanical implications onhe behavior of the articular disc. However, as long as theystem preserves the ability to adapt to the new functionaltatus, the altered mechanical loading is compensated by thetructural modeling of the TMJ. Although the coordination ofhe disc-condyle complex may be lost, in this stage the pa-ient is usually asymptomatic.

The exposure to excessive or prolonged loading may over-ome the biomechanical limits of the TMJ. If modeling isnable to restore a functional equilibrium, the tissues of theMJ can still show compensatory mechanisms to prevent or

imit potential damages. When the reserve of adaptative andompensatory responses is exhausted, the changes takinglace in the TMJ are known as regressive modeling (ie, mal-daptation).3 At this stage, decompensated and destructiveorphologic changes are usually revealed with pain and

ther clinically evident signs and symptoms. With time, thelinical manifestations may become less obvious because aate-stage response allows for functioning, even when the

Figure 4 Disc derangements: schematic representation odirections of dislocation (E to H). The images refer to the(A), the posterior band of the disc is normally located wipassing through the axis of rotation of the condylar heaposterior band locates anteriorly to the area enclosed inwhen, in the sagittal view, the posterior band falls intomedial displacements occur when, in the coronal view, tits borders bulge from the borders of the condylar heunidirectional displacements are often associated. The pof a multidirectional displacement. The oblique orientacondyle tend to direct most meniscal displacements in a

MJ is altered. d

lassification and Clinical Courseifferent criteria have been used to classify disc derange-ents. A common approach, used in reporting magnetic res-

nance imaging examinations of the TMJ, is to assess theirection of disc displacement, which may be anterior, me-ial, lateral, or even posterior (Fig. 4). Multidirectional dis-lacements are considered more frequently than unidirec-ional ones (Fig. 5). Posterior derangements are rare.45,46 Theblique orientation of the lateral pterygoid muscle and thengulation of the condyle direct most meniscal displace-ents in an anterior-medial path.Anterior disc derangements are grouped into four cate-

ories based on the degree of dislocation, reversibility dur-ng the opening-closing movement, and changes in dischape (Table 1 and Figs. 6 and 7). In the early stage, jointoise or dysfunction is not evident. However, at mouthpening, the patients may feel a slight catching sensation.his may be the earliest sign that a change in the frictionalroperties of the joint has occurred. Therefore, this stagef derangement has been referred to as TMJ disc incoor-

ormal position of the articular disc (A to D) and mainMJ in rest position (closed-mouth). In the sagittal view

10-degree angle counterclockwise from the vertical lineerior displacement (E) should be considered when the-degree-angle range. Posterior displacement (F) occursegree angle clockwise from the vertical line. Lateral oresponding lateral or medial attachments of the disc andand H, from the normal position in C and D). Theser displacement is rare either unidirectionally or as a partthe lateral pterygoid muscle and the angulation of therior-medial path.

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In the next stage, the articular disc has slipped forward in annterior-medial position. In rest position and in centric occlu-ion, the posterior band of the disc is located behind the apex ofhe condylar head. Mouth opening occurs with a clicking oropping sound, because the posterior band of the disc slips backver the condylar head. As a result, in the open-mouth positionhe intermediate zone of the disc will be placed correctly be-ween the condylar head and the eminence of the temporalone. Because the opening movement relocates the disc in the

oint, this stage is referred to as disc displacement with reduc-ion. Occasionally, a second clicking sound is heard duringouth closure (“reciprocal click”), because the posterior band of

he disc slips forward off the condyle. Other clicking sounds canlso be produced by irregularities or defects in the surface of theisc or by changes in the convexity of the condyle and/or artic-lar eminence. These sounds are usually less obvious than thoseaused by anterior disc displacement. They are also found at theame point of the TMJ translator movement rather than at dif-erent points, as occurs with reciprocal clicking.

In the third category of internal derangement, a greateregree of anterior displacement of the disc is found. The disclso acts as an obstacle, preventing the condyle to overcomehe posterior band when mouth opening is attempted. In thisondition the joint appears as “locked.” Clicking sounds areot heard. This stage is referred to as disc displacement with-ut reduction or closed lock.The fourth category is also characterized by a limitation ofouth opening. However this limitation may not be caused byisc displacement. The disc may be in a normal position butdvanced degenerative changes have occurred. Adherences are

Figure 5 Anterior-lateral displacement demonstrated bysagittal (A to E) and coronal (F to L) planes in closeddisplacement of the articular disc, which bulges anterioThe lateral component of the displacement is better rarrowheads). The morphology of the disc is irregular anthe lateral aspect of the joint capsule (B and I). Multidirones. A careful analysis of all sagittal and coronal imagesdisc derangement.

sually found with the disc and the articular eminence, so that j

nly condylar rotation is allowed. On the other hand, adher-nces also limit the mobility of the disc (ie, “stuck,” “fixed,” orfrozen disc”).38 In addition, late-stage changes in disc morpho-ogic and magnetic resonance signal become more evident. Aiconvex, rounded, irregular, or flat disc usually indicates moredvanced disease.47-49 Tear and perforations of the disc may alsoccur.38

The progression from the subclinical or clinical manifestationowards the late stages of disc derangements has been confirmedy retrospective and cross-sectional studies.50,51 Lundh et al52

eported that 9% of reducing disc derangements progressed toonreducing ones within 3 years. However, reducing disc dis-lacements can also remain constant for many years, suggestinghat the clicking joint does not necessarily progress to lockingerangement.52-56

The morphologic and functional changes of the TMJ usu-lly correlate well with the clinical signs and symptoms thatharacterize each stage. However, because altered loadingnduces structural changes in the TMJ tissues (ie, remodel-ng), large inconsistencies may also be found between imag-ng findings and clinical manifestations of disc derangementFig. 8).

linical Assessment ofemporomandibular Disordersnd Diagnostic Protocolsisc derangements may have clinical manifestations sim-

lar to those of other disorders of the facial region. Pain and

tic resonance fast spin-echo DP-weighted images in theh position. Sagittal sections in the first line show the

laterally against the joint capsule (black arrowheads).zed in the coronal sections in the second line (white. The disc also shows a tendency to bend and fold overl displacements are more common than unidirectionalMR examination is mandatory to define the direction of

magne-moutrly andecognid wavyectionaof the

aw dysfunction can be related to toothache, pericoronitis,

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axillary sinusitis, earache, salivary gland pathosis, tem-oral arteritis, neuralgias, and tension-type headache. Allhese conditions should be excluded when assessing pa-ients with clinical suspicion of disc derangements. In ad-ition, two other temporomandibular disorders (TMDs)ust be considered in the differential diagnosis of symp-

omatic disc derangements: myofascial pain and dysfunc-ion (MPD), and painful inflammatory or degenerativeonditions of the TMJ.

MPD differs from primary TMJ disorders, because in theormer pain originates from the masticatory muscles. Myo-ascial pain is the most common TMD. It is characterizedy a dull ache in the TMJ region that increases duringunction, with other possible ancillary findings (ie, ten-

able 1 Classification of Disc Derangements

ClinicalStages Type C

tage I(incoordination)

Incoordination ● Catching sen● No joint nois● No pain, join● No opening

tage II(intermittentlocking)

Displacement withreduction

● Asymptomatpopping sou

● Episodes offor various le

● In the late stlocking

● Joint pain wi● Association

palpation● Lateral devia

unilateral co● Headache an

to protective● “Hitting an o

attempted● Obstruction

or manipulatinterference

tage III(closed lock)

Displacementwithoutreduction

● Clicking nois● Referred hist● Inability to o● Localized pa

attempted m● Joint tendern● Deviation of

side with mo

tage IV (discadhesion)

Stretchedretrodiscaltissue loses itselasticity, thins,and perforates.

Progression toosteoarthrosis

● Restricted m● Absence of p

opening or ccapsule

RI, magnetic resonance imaging.

ion-type headache, earache, or toothache; a sensation of a

uscle stiffness; reduced motion of the mandible).57 Inhe same group (MPD) are included regional problems ofhe muscles, such as myositis, myospasm, local myalgia,yofibrotic contracture, as well as the centrally mediated

hronic muscle pain. Systemic disorders, such as fibromy-lgia, may also have considerable overlap in clinical fea-ures with MPD.58

The diagnosis of painful conditions of the temporoman-ibular region requires a careful evaluation of the historyf the patient (dental, medical, and psycho-social data)nd a detailed examination of signs and symptoms. Clin-cal assessment should be always performed before imag-ng (Fig. 9A to F). If the most important symptom reportedy the patient is pain, its characteristics should be assessed

l Hallmarks Imaging Features (MRI)

during mouth opening

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reasing functionint tenderness on lateral

f the mandible in

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isappear spontaneouslymandible beyond the

● Disc displacement incentric occlusion

● Normally located disc inopen-mouth position

appearclicking or popping

outh widelyhe TMJ increasing withpening and chewingn lateral palpationandible to the affectedening

● Disc displacement inboth centric occlusionand maximal open-mouthpositions

● Limited condylartranslation

● Morphologicalpathologic changes ofdisc (rounded, irregulardisc, etc.)

peningless in voluntary mouth

g with stretching of joint

● Stuck or fixed disc● Disc perforation (difficult

to assess)

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ion, intensity, quality, duration, modifiers, chronicity ofain, and associated symptoms suggest a potential masti-atory muscle disorder, a panoramic radiograph should berst obtained to exclude possible dental, periodontal, orther problems of the oral region. If the patient’s historynd clinical findings suggest an intracapsular joint prob-em, the assessment of the TMJ should be performed using

RI. Such an imaging tool can be used concurrently toxclude some causes of muscular problems (ie, focal my-sitis, abscess, muscle atrophy, etc.) and local diseases ofhe oral region, providing helpful information in the dif-erential diagnosis of TMDs.38

herapeutic Outlineslthough genetic, biochemical, and histological aspects of

Figure 6 Schematic representation of disc position andnormal subject (A to C), the disc adapts to the articularthe temporal bone and the condylar head. Simultaneodirection. The intermediate zone maintains a consistentopen or intermittent lock (D to F). Anterior disc displacreduces behind the condyle on partial opening and appe(G to I). Anterior disc displacement does not disappeprevents forward and downward motion of mandible. Sdetails).

he TMDs have been studied, the etiology of these disorders d

emains largely unknown. Therefore, therapy is largely de-endent on the initial clinical assessment of the patient.hen signs and symptoms are correctly interpreted, the ap-

lication of research-based therapeutic guidelines can lead toreatment success. According to literature, a positive out-ome can be achieved by therapy in 75 to 90% of pa-ients.59-64

A wide consensus has been reached through the years ononsidering conservative and reversible approaches as first-lineherapy of symptomatic disc derangement.65-69 Included in thisroup are various medications, such as nonsteroidal anti-inflam-atory drugs and muscle relaxant, oral appliances, home carerocedures, and cognitive-behavioral information program.hen these approaches fail to produce clinical improvements

n painful dysfunctional conditions of the TMJ, surgical proce-ures (ie, arthrocentesis, arthroscopic surgery, discoplasty, and

ology during the stages of anterior derangement. In as of the TMJ, and it glides during jaw opening betweene condylar head rotates and translates in the anteriorship with the condyle and temporal eminence. Stage 2,is found in the closed-mouth position. Posterior bandmal at full open-mouth position. Stage 3-4, closed lockng jaw opening. Severe anterior displacement of discis not displayed in the drawing (see the text for further

morphsurfaceusly, threlationementars norar duritage 1

iscectomy) may be indicated. Several case-based studies have

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hown that surgical management may be effective. However, toncrease the chances of treatment success in patients not respon-ive to conservative therapy, the least invasive procedure thatan be effective should be first proposed.

Oral appliances (Fig. 9G and H) are used in patientsith symptomatic disc derangement for stabilizing or re-ositioning the occlusal maxillomandibular relationship.he stabilizing approach is reversible. It produces changes

n the occlusal behavior of the patient, by inducing con-ciousness of any oral parafunction. Therefore, it reduceshe chance of further wear, chipping, or cracking of theeeth. In unstable occlusion caused by absence of multipleosterior contacts bilaterally, stabilization restores the au-omatism of normal occlusion. It is also indicated in pa-ients suffering from bruxism and for managing symptomsssociated with TMJ disc derangement.70 The mandibular

Figure 7 Fast spin-echo DP-weighted MR images in closubjects. Images in the first line indicate the normal poImages in the second line (C, D) were obtained from aaccident, she reported lateral deviation of the jaw and trafrom the TMJ of the affected side occurred after she fdisplacement of the articular disc in centric occlusion (Dthe third line (E, F) are relative to a young woman withopening, after repeated episodes of jaw blockage in opappears dislocated anteriorly. The superior contour of thin the upper joint compartment. In the open-mouth posifossa, suggesting a limitation in the forward translation oupper joint cavity collects into the increased concavity. T

Figure 8 Example from a patient with inconsistent clinclosed-mouth position (A), the T2*-weighted MR imagposterior band is positioned beyond the condylar headspatially adjacent T2*-weighted MR images confirm a nto the articular eminence and the condylar head (small ais twisted. Concurrently, the roundness of the condylaralterations can be found. Based on these MRI findings,displacement was not reduced by jaw opening. Howevderangement, because he was asymptomatic and had reintermittent locking. Physical examination had shown nthe MR images in the open-mouth position (B, C) as theclinical-radiological inconsistencies can be explained byloading conditions (see the text for further details).

disc, which acts as an obstacle to the movement of the TMJ.

epositioning appliance has deeper effects on the positionf maximum intercuspation and may cause a permanentcclusal change.71,72 The theory behind the use of thisppliance is to shift the mandibular condyles in a moreorward position and, therefore, to allow for recapturing ofdisplaced disc.73 This appliance is often used in patientsith painful clicking or intermittent locking. However,

he results of this strategy may not be as good as expected.ong-term case report studies have suggested that TMJlicking may recur over time and, even without audibleoint sounds, disc position can remain altered.74-77

onclusionsnder nonphysiologic loading, the various structures of theMJ show adaptative and compensatory responses to prevent

D, F) and open (A, C, E) mouth position, from threef the articular disc in an asymptomatic subject (A, B).

exposed to face trauma at work. Immediately after thedifficulty in mouth opening. Reciprocal clicking soundsthe jaw open. The MR examination revealed anteriorh reduction in full open-mouth position (C). Images inonth history of bilateral TMJ pain and limited mouth

uth position. In resting position (F), the articular discs also slightly concave, retaining a small fluid collection), the condylar head remains almost stuck in the glenoidondyle itself. The disc is bent inferiorly. The fluid in thedylar head does not pass over the posterior band of the

d MRI findings of anterior disc derangement. In theests anterior displacement of the articular disc, whosearrow). In the open-mouth position (B to C), the twocing disc displacement, as the disc is located anteriorly. The shape of the disc is deeply altered and its structurereduced and, just below its articular surface, MR signalIV disc derangement might be suspected, because thepatient had been clinically classified as a stage II discnly occasional episodes of limited mouth opening andopening range of the mouth. This may be sensed fromlar head appears beyond the articular eminence. Thesebility of the TMJ tissues to remodel under unfavorable

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ermanent tissue damages and allow for function. Decom-ensation and degenerative changes may occur when TMJodeling is unable to restore a biomechanical equilibrium.isc derangements may lead to altered loading and regressivehanges in the TMJ. However, because of the adaptative ca-acity of the joint, these changes may be asymptomatic orinimally evident for a long time. A careful clinical evalua-

ion, reinforced by imaging findings, should help distinguishsymptomatic disc derangements from pathologic conditionshat may require treatment.

eferences1. Haskin CL, Milam SB, Cameron IL: Pathogenesis of degenerative joint

disease in the human temporomandibular joint. Crit Rev Oral Biol Med6:248-27, 1995

2. Oberg T, Carlsson GE, Fajers CM: The temporomandibular joint. Amorphologic study on a human autopsy material. Acta Odontol Scand29:349-34, 1971

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Figure 9 Phases of clinical examination of a patient with splanning with oral appliance on the maxillary arch (Gevaluated, noting developmental abnormalities, trauma,opening movement of the mouth (B) should be assessederangements. The range of motion in the vertical planefor women. If the interincisal distance differs largely beopening, a muscle based limitation should be suspectedand their possible limitations should be assessed. Joint so(F) during jaw movements. However, clicking is unspalpation, performed both from common external appmuscle tension and alterations of muscular trophism. Ftogenic causes of patient’s orofacial pain or parafunctionappliance of the upper maxillary bone (G, H). (Color ve

Publishing Co., Inc., 1997, pp 23-40

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of a TMJ disorder (A to F) and conservative therapeutic). In each patient, face symmetry (A) should be firstelling of external tissues. Similarly, the symmetry of thedeviations at jaw opening may suggest unilateral disc

normal subjects is 40 � 3 mm for men and slightly lessmaximum-unassisted opening and maximum-assistedhorizontal plane, lateral and protrusive jaw movementhould be evaluated with palpation (D) and auscultation, being heard also in asymptomatic subjects. Muscle(D) and from intraoral manipulation (E), might revealintraoral examination should consider possible odon-its that have special relevance to myofascial pain. Oralf figure is available online.)

uspectto H

and swd. Side(C) intween. In theunds specificroachinally,al hab

disc. J Dent Res 76:1760-1769, 1997

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temporomandibular joint soft-tissue pathology, i: disc abnormalities

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