TS iscFr nicoRe and

mmonects.

echamallyshoulrequ

07 Els

Tboelewi(Fithedivmeforlin

takaxea major role in compensating the incongruities of the articu-lar surfaces. In the mandibular opening-closing movement,forto(Fimeingdis

BiMeen

notiorefllagforarttheofsprturbioits

tratation of these molecules into the extracellular matrix vary inthe different portions of the disc.7-9 Because of the inhomo-

*D

InAdd

192instance, the condylar head rotates and translates relativethe temporal bone with a simultaneous gliding of the discg. 3). Several theories have been proposed to explain thechanism that coordinates the disc-condyle complex dur-jaw movements.4 The biomechanical properties of the

c are largely involved in this coordination.5

omechanical Properties of the Discchanical loading of the TMJ occurs over highly incongru-t articular surfaces and limited contact areas. If loading was

geneous distribution of macromolecules and fluid in the con-nective matrix, the disc expresses region-specific viscoelasticproperties.10 Stiffness, strength, permeability, and otherphysical properties vary from the anterior to the posteriorband and in both lateral zones. Thus, each region of the discresponds to mechanical loading with a specific type of localdeformation. These plastic changes are considered adaptativeresponses to the different mechanical stresses experiencedlocally (ie, compression, tension, or shear). They also ensurethe physiological coordination of the disc-condyle complexduring jaw movements.

The equilibrium between mechanical forces acting in theTMJ and adaptative responses of the disc may change duringlife. Mechanical loading has a continuous influence on thecomposition and behavior of the disc. Although the mecha-

epartment of Bioimaging and Radiological Sciences, Catholic Universityof Rome, Italy.stitute of Clinical Dentistry, Catholic University of Rome, Italy.ress reprint requests to: Francesco Molinari, MD, Department of Bioim-emporomandibular Jointoft-Tissue Pathology, I: Dancesco Molinari, MD,* Paolo Francesco Manzo Raffaelli, MD, Tommaso Pirronti, MD,*

The internal derangements are the most codisc, observed even in asymptomatic subjshows large adaptative and compensatory mthese disorders may be asymptomatic or minievaluation, reinforced by imaging findings,rangements from painful conditions that maySemin Ultrasound CT MRI 28:192-204 20

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

ne and the condyle of the mandible. These two osseousments are enclosed into a fibrous capsule and articulateth each other by an interposed disc of connective tissuegs. 1 and 2).1-3 The disc is fixed to the articular capsule andlateral margins of the condyle. The joint cavity is thereforeided into an upper and a lower compartment. A synovialmbrane lines the inner side of the capsule and disc, exceptthe articulating surfaces. Synovial fluid produced by thising membrane fills the joint compartments.The TMJ is responsible for all movements of the jaw, whiche place in different orthogonal planes and aroundmultiples of rotation. In these movements, the articular disc playsnisne

aging and Radiological Sciences, Catholic University of Rome, L.go F.Vito n. 1, 00168 Rome, Italy. E-mail: fmolinari@rm.unicatt.it.

0887-2171/07/$-see front matter 2007 Elsevier Inc. All rights reserved.doi:10.1053/j.sult.2007.02.004Abnormalitiesne, MD, Luca Raffaelli, MD,

Lorenzo Bonomo, MD*

noninflammatory abnormalities of theBecause the temporomandibular jointnisms over dysfunctional disc motion,evident for a long time. A careful clinicald help differentiate asymptomatic de-ire treatment.evier Inc. All rights reserved.

t compensated by the TMJ disc, the nonuniform distribu-n of mechanical stress during jaw movements would beected directly over the articular surfaces, leading to carti-e damage. Peak loads are normally absorbed by local de-mations of the disc, occurring in the contact areas with theicular surfaces. As the movement of the TMJ proceeds,se deformations involve progressively different portionsthe disc. The result is a dynamic structural adaptation thateads the mechanical stress over larger surfaces.5,6 The na-e and extent of this adaptative response depend on themechanical properties of the disc and the forces acting onmolecular structure.Several investigators have reported that the local concen-tion of collagen, elastin and proteoglycans, and the orien-m is not clear yet, a modulation of the synthesis of con-ctive tissue has been suggested.11-15 Similarly, age-related

chthe

dutissvobiomatheulamaThdittat

TMJ soft-tissue pathology 193anges of the mineral and macromolecular components ofdisc cause variations of its viscoelastic properties.16-19

Trauma and other pathological conditions usually pro-ce more extensive structural changes, involving also otherues of the TMJ. If these pathological changes do not in-lve primarily the disc, they may still have influences on itsmechanical behavior.20 For instance, a pathologic agenty alter the molecular composition and the properties ofarticular cartilage, increasing the roughness of the artic-r surface.21 The higher shear stress experienced locallyy induce changes on the viscoelastic properties of the disc.is adaptative response compensates the new loading con-

Figure 1 Schematic (A, C) and magnetic resonance T2*-weiin the coronal (A, B) and sagittal (C, D) view. Two ossetemporal bone (GF and E) and the condylar head of themanand temporal bone. In the closed-mouth position, the condThe articular eminence (E) forms the anterior wall of the gjoint during function. The entire articular surface of the tdegree of convexity and concavity. The condylar head marounded to flattened superior surface. An articular disc (*)the coronal view (A, B), the inferior, concave surface of thesuperior surface of the disc is slightly convex, fitting the conattached to the medial and lateral poles of the condyle byattachments increase the medial-lateral stability of the disinserted between the anterior and posterior margins of thethe disc-condyle complex during function. (Color versionions. However, if mechanical stress overcomes the adap-ive capabilities of the disc, degenerative changes may oc-

Thmar even on the osseous elements of the TMJ, because ofcompensated loading.Such interactions and reciprocal influences, mediated byme-nical loading, are common among the components of theJ andmay reach considerable complexity. In fact, concurrenth an altered disc function, histological changes have beenserved in other elements of the TMJ. These changes will bentioned in dealing with disc abnormalities.

sc Abnormalities: Internal Derangements

finition and Pathophysiology

(B, D) images of the temporomandibular joint (TMJ),ments form the TMJ: the squamous portion of theCo). An articular capsule (JC) attaches to the condyle) is housed in the bony roof of the glenoid fossa (GF).fossa and represents the load-bearing portion of theal bone (GF and E) is saddle shaped with a variablehave a significant variation in size and form, with arposed between the articular surfaces of the TMJ. Inatches the articular surface of the condylar head. Therface of the articular fossa. The articular disc is firmlyollateral, disco-mandibular ligaments (DML). Theseg condylar movements. Similarly, connective fibersd the capsule (1, 2) participate actively in stabilizingre is available online.)cuun

chaTMwitobme

Di

De

ghtedous eledible (yle (Colenoidempory alsois intedisc mcave suthe c

c durindisc anof figue internal derangements are the most common noninflam-tory abnormalities of the TMJ, being observed even in

asyaltlarthemestrinflsifiHodisint

194 F. Molinari et al.mptomatic subjects. The term derangement refers to aneration in the normal pathways of motion of the TMJ thatgely involves the function of the articular disc. Therefore,se alterations have been also referred to as disc derange-nts. They differ from degeneration because the quality anducture of the TMJ tissues are not necessarily altered. Theammatory and degenerative disorders of the joint are clas-ed in a different pathological group (ie, osteoarthritis).wever, much overlap in the clinical course of these two

Figure 2 Schematic (A, C) and magnetic resonance T2*-wemandibular joint in the sagittal view, in closed- (A, B, D) anis a biconcave (bow tie) or sigmoid-shaped structure, madfibrocartilage, interposed between the temporal bone and tparts: an anterior band (AB), a thinner avascular intermediadisc in these three parts differs in the medial-lateral directimechanical loads also influence themolecular compositionetc.). The AB prolongs anteriorly into connective fibers (Aplane. Medially, some of the fibers of the AP are continuouprobably with the fibers of the masseter and temporal muand vascularized attachment, the retrodiscal tissue (RT). Tand can be divided into temporal, intermediate, and conretrodiscal lamina (1) attaches to the most posterior areas oposterior region of condylar neck. Between these two lainnervated by sensory fibers. The shape of the disc and its cduring jaw movement (C) to adapt to the articular surfacposterior attachment increases significantly when the discstretching of the elastic fibers promotes the inflow of blooversion of figure is available online.)orders has been reported.22 The articular surfaces may beerested by degeneration with a normally located disc.23-25

efffaigenerative changes of the TMJ may also occur because ofchanical derangements of the disc.Many etiologic factors have been proposed to explain discrangements. Traumatic events may cause stretching, tear-, or rupture of the disc, lateral ligament, or capsule. Wheneding occurs, fibrotic or hyperplastic intra-articular reac-ns may lead to restricted mobility and pain.26 Less obviousuries of the TMJ may also cause soft-tissue responses andd to permanent intra-articular changes, with long-term

(B, D, E) images of the articular disc of the temporo-n-mouth position (E). The articular disc or meniscusf fibrous connective tissue with varying amounts ofndible (see also Fig. 1). The disc is divided into threee (IZ), and a posterior band (PB). The thickness of theording to a differential loading pattern. Site-specificdisc (the distribution of proteoglycans, cartilage cells,ich insert on the anterior margin of the preglenoidthe superior head of the lateral pterygoid muscle andhe PB continues posteriorly into a richly innervatedis a fibroelastic structure covered by a synovial layerlayers or laminae. The temporal lamina or superiorenoid fossa. The inferior lamina (2) is attached to theis a loose connective tissue (intermediate layer, 3)areas with the articular surfaces continuously changee mandible and temporal bone. The volume of thele complex moves anteriorly (D and E), because thethe vessels-rich intermediate layer of the RT. (ColorDeme

deingbletioinjlea

ightedd opee up ohe mate zonon, accof theP), whs withscles. The RTdylarf the glminaeontactes of th-condyd intoects on the disc function. However, several studies haveled to confirm these theories.27,28

diserawipu

deconasseveha

theThand

du

TMJ soft-tissue pathology 195A laxity of the ligaments of the TMJ has also been related toc derangements.29-31 However, the prevalence in the gen-l population of disc derangements appears not to matchth that of joint laxity. Controversial data have been alsoblished on this issue.32

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

Changes in the compositionof the synovial fluidmay increaseintra-articular friction, leading to unstable disc motion.36,37

ese biochemical changes may also affect the joint lubricationnutritional requirements of the articular surfaces.

Figure 3 Schematic representation of the TMJ during physto l). Jaw opening occurs with a rotation and anterior tranand disc move forward simultaneously (disc-condyle compreglenoid plane, beyond the apex of the articular eminencband and the intermediate zone of the disc, whereas the posame time, the temporal layer of the retrodiscal tissue is p(e to i). During jaw closing (h to l), the movement of the diThe lateral movements of the mandible are rare during chetion (eg, tooth grinding).An improper activity of the lateral pterygoid muscle (LPM)ring TMJ motion has been also related to disc derange-

anfibnts.38 Morphologic changes of LPM, such as hypertrophy,ophy, or contracture, have been found in patients withterior disc displacement without reduction.39 A higherpensity toward anterior disc displacement has also beennd in subjects in which the LPM attaches to the disc butt to the condyle.40

Independently from the etiologic factors and concurrentfavorable conditions, disc derangements occur when thection of the disc is compromised. An initial adaptativeponse, triggered by overloading, induces structuralanges in the TMJ. This is a slow but continuous process ofdeling that involves all the elements of the TMJ, withinue-specific limits. Although physiological changes occurthe disc, its ability to remodel is lower than that of otherues of the TMJ, such as the capsule, capsular ligaments,

opening-closing movement of the mandible (from aof the condyle of the mandible (a to c). The condylet maximal jaw opening (g), the condyle reaches theis position, the condylar surface contacts the anteriorband is stretched over the articular eminence. At theagainst the fossa, whereas the condylar layer loosensdyle complex is the exact reverse of the opening one.They are detected more frequently during parafunc-meatranprofouno

unfunreschmotissintiss

iologicslationplex). Ae. In thsteriorressedsc-conwing.d retrodiscal tissues.41 Decreased vascularity and extensiverous transformation have been reported in the retrodiscal

tissapthesysstastrthetie

comunTMlimcomplaadmoothclilatTM

196 F. Molinari et al.ue for continuous compression and shear.42-44 These ad-tative changes can also have mechanical implications onbehavior of the articular disc. However, as long as thetem preserves the ability to adapt to the new functionaltus, the altered mechanical loading is compensated by theuctural modeling of the TMJ. Although the coordination ofdisc-condyle complex may be lost, in this stage the pa-

nt is usually asymptomatic.The exposure to excessive or prolonged loading may over-e the biomechanical limits of the TMJ. If modeling is

able to restore a functional equilibrium, the tissues of theJ can still show compensatory mechanisms to prevent orit potential damages. When the reserve of adaptative andpensatory responses is exhausted, the changes taking

ce in the TMJ are known as regressive modeling (ie, mal-aptation).3 At this stage, decompensated and destructiverphologic changes are usually revealed with pain ander clinically evident signs and symptoms. With time, thenical manifestations may become less obvious because a

Figure 4 Disc derangements: schematic representation of tdirections of dislocation (E to H). The images refer to the ri(A), the posterior band of the disc is normally located withpassing through the axis of rotation of the condylar head.posterior band locates anteriorly to the area enclosed in thwhen, in the sagittal view, the posterior band falls into a 1medial displacements occur when, in the coronal view, theits borders bulge from the borders of the condylar headunidirectional displacements are often associated. The postof a multidirectional displacement. The oblique orientatiocondyle tend to direct most meniscal displacements in ane-stage response allows for functioning, even when theJ is altered.

ofdinassification and Clinical Coursefferent criteria have been used to classify disc derange-nts. A common approach, used in reporting magnetic res-ance imaging examinations of the TMJ, is to assess theection of disc displacement, which may be anterior, me-l, lateral, or even posterior (Fig. 4). Multidirectional dis-cements are considered more frequently than unidirec-nal ones (Fig. 5). Posterior derangements are rare.45,46 Thelique orientation of the lateral pterygoid muscle and thegulation of the condyle direct most meniscal displace-nts in an anterior-medial path.Anterior disc derangements are grouped into four cate-ries based on the degree of dislocation, reversibility dur-the opening-closing movement, and changes in disc

ape (Table 1 and Figs. 6 and 7). In the early stage, jointise or dysfunction is not evident. However, at mouthening, the patients may feel a slight catching sensation.is may be the earliest sign that a change in the frictionalperties of the joint has occurred. Therefore, this stage

mal position of the articular disc (A to D) and mainJ in rest position (closed-mouth). In the sagittal view-degree angle counterclockwise from the vertical lineor displacement (E) should be considered when theegree-angle range. Posterior displacement (F) occursree angle clockwise from the vertical line. Lateral orponding lateral or medial attachments of the disc andd H, from the normal position in C and D). Theseisplacement is rare either unidirectionally or as a parte lateral pterygoid muscle and the angulation of ther-medial path.ClDimeondirdiaplatioobanme

goingshnoopThpro

he norght TMin a 10Anteriis 10-d0-degcorres(G anerior dn of thanterioderangement has been referred to as TMJ disc incoor-ation.

antsiothepoovethetwbojoitiomothealsdisulacausamfer

dealstheconnoou

modisadvusu

onencfrologbic

gneticouth pand lagnizedavy. Tional dthe MR

TMJ soft-tissue pathology 197In the next stage, the articular disc has slipped forward in anerior-medial position. In rest position and in centric occlu-n, the posterior band of the disc is located behind the apex ofcondylar head. Mouth opening occurs with a clicking or

pping sound, because theposterior bandof thedisc slips backr the condylar head. As a result, in the open-mouth positionintermediate zone of the disc will be placed correctly be-

een the condylar head and the eminence of the temporalne. Because the opening movement relocates the disc in thent, this stage is referred to as disc displacement with reduc-n. Occasionally, a second clicking sound is heard duringuth closure (reciprocal click), because theposterior bandofdisc slips forward off the condyle. Other clicking sounds cano be produced by irregularities or defects in the surface of thec or by changes in the convexity of the condyle and/or artic-r eminence. These sounds are usually less obvious than thosesed by anterior disc displacement. They are also found at thee point of the TMJ translator movement rather than at dif-

ent points, as occurs with reciprocal clicking.In the third category of internal derangement, a greatergree of anterior displacement of the disc is found. The disco acts as an obstacle, preventing the condyle to overcomeposterior band whenmouth opening is attempted. In thisdition the joint appears as locked. Clicking sounds aret heard. This stage is referred to as disc displacement with-t reduction or closed lock.The fourth category is also characterized by a limitation ofuth opening. However this limitation may not be caused byc displacement. The disc may be in a normal position but

Figure 5 Anterior-lateral displacement demonstrated by masagittal (A to E) and coronal (F to L) planes in closed-mdisplacement of the articular disc, which bulges anteriorlyThe lateral component of the displacement is better recoarrowheads). The morphology of the disc is irregular and wthe lateral aspect of the joint capsule (B and I). Multidirectones. A careful analysis of all sagittal and coronal images ofdisc derangement.anced degenerative changes have occurred. Adherences areally found with the disc and the articular eminence, so that

ilajawly condylar rotation is allowed. On the other hand, adher-es also limit the mobility of the disc (ie, stuck, fixed, orzen disc).38 In addition, late-stage changes in disc morpho-ic and magnetic resonance signal become more evident. Aonvex, rounded, irregular, or flat disc usually indicates moreanced disease.47-49 Tear and perforations of the discmay alsour.38

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

orted that 9% of reducing disc derangements progressed tonreducing ones within 3 years. However, reducing disc dis-cements can also remain constant for many years, suggestingt the clicking joint does not necessarily progress to lockingangement.52-56

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

linical Assessment ofemporomandibular Disordersd Diagnostic Protocols

sc derangements may have clinical manifestations sim-

resonance fast spin-echo DP-weighted images in theosition. Sagittal sections in the first line show theterally against the joint capsule (black arrowheads).in the coronal sections in the second line (white

he disc also shows a tendency to bend and fold overisplacements are more common than unidirectionalexamination is mandatory to define the direction ofadvocc

towbyrepnoplathader

allchindinging(Fi

CTanDir to those of other disorders of the facial region. Pain anddysfunction can be related to toothache, pericoronitis,

mapothetieditmutomtioco

forfasbyfunsio

Tab

ical H

Sta(

tion d

enderitation

Sta(l

excep

ited mths oe, pre

increth join

n of t

Sta(

Staa

MR

198 F. Molinari et al.xillary sinusitis, earache, salivary gland pathosis, tem-ral arteritis, neuralgias, and tension-type headache. Allse conditions should be excluded when assessing pa-nts with clinical suspicion of disc derangements. In ad-ion, two other temporomandibular disorders (TMDs)st be considered in the differential diagnosis of symp-atic disc derangements: myofascial pain and dysfunc-

n (MPD), and painful inflammatory or degenerativenditions of the TMJ.MPD differs from primary TMJ disorders, because in themer pain originates from the masticatory muscles. Myo-cial pain is the most common TMD. It is characterizeda dull ache in the TMJ region that increases during

le 1 Classification of Disc Derangements

ClinicalStages Type Clin

ge Iincoordination)

Incoordination Catching sensa No joint noise No pain, joint t No opening lim

ge IIintermittentocking)

Displacement withreduction

Asymptomaticpopping sound

Episodes of limfor various leng

In the late staglocking

Joint pain with Association wi

palpation Lateral deviatio

unilateral cond Headache and

to protective sp Hitting an obs

attempted Obstruction ma

or manipulatinginterference

ge IIIclosed lock)

Displacementwithoutreduction

Clicking noises Referred histor Inability to ope Localized pain

attempted mou Joint tendernes Deviation of th

side with mout

ge IV (discdhesion)

Stretchedretrodiscaltissue loses itselasticity, thins,and perforates.

Progression toosteoarthrosis

Restricted mou Absence of pai

opening or checapsule

I, magnetic resonance imaging.ction, with other possible ancillary findings (ie, ten-n-type headache, earache, or toothache; a sensation of

byasscle stiffness; reduced motion of the mandible).57 Insame group (MPD) are included regional problems ofmuscles, such as myositis, myospasm, local myalgia,ofibrotic contracture, as well as the centrally mediatedronic muscle pain. Systemic disorders, such as fibromy-ia, may also have considerable overlap in clinical fea-es with MPD.58

The diagnosis of painful conditions of the temporoman-ular region requires a careful evaluation of the historythe patient (dental, medical, and psycho-social data)d a detailed examination of signs and symptoms. Clin-l assessment should be always performed before imag-(Fig. 9A to F). If the most important symptom reported

allmarks Imaging Features (MRI)

uring mouth opening

ness

None

t for the clicking or

outh opening that lastf timesence of intermittent

asing functiont tenderness on lateral

he mandible in

le muscle pain relatedg of the mandiblen when opening is

ppear spontaneouslyandible beyond the

Disc displacement incentric occlusion

Normally located disc inopen-mouth position

pearlicking or poppingth widelyTMJ increasing withning and chewing

lateral palpationdible to the affecteding

Disc displacement inboth centric occlusionand maximal open-mouthpositions

Limited condylartranslation

Morphologicalpathologic changes ofdisc (rounded, irregulardisc, etc.)

ningss in voluntary mouth

with stretching of joint

Stuck or fixed disc Disc perforation (difficult

to assess)muthethemychalgtur

dibofanicaing

itionpossiblintintructio

y disathe m

disapy of cn mouin theth opes on

e manh open

th open unlewingthe patient is pain, its characteristics should be assessedpart of a routine diagnostic protocol. When the loca-

tiopacatfirsothanlemMRexosithefer

TAltthe

TMJ soft-tissue pathology 199n, intensity, quality, duration, modifiers, chronicity ofin, and associated symptoms suggest a potential masti-ory muscle disorder, a panoramic radiograph should bet obtained to exclude possible dental, periodontal, orer problems of the oral region. If the patients historyd clinical findings suggest an intracapsular joint prob-, the assessment of the TMJ should be performed usingI. Such an imaging tool can be used concurrently to

clude some causes of muscular problems (ie, focal my-tis, abscess, muscle atrophy, etc.) and local diseases oforal region, providing helpful information in the dif-

ential diagnosis of TMDs.38

herapeutic Outlines

Figure 6 Schematic representation of disc position and mnormal subject (A to C), the disc adapts to the articular surthe temporal bone and the condylar head. Simultaneousldirection. The intermediate zone maintains a consistent relopen or intermittent lock (D to F). Anterior disc displacemreduces behind the condyle on partial opening and appears(G to I). Anterior disc displacement does not disappearprevents forward and downward motion of mandible. Stagdetails).hough genetic, biochemical, and histological aspects ofTMDs have been studied, the etiology of these disorders

dudisains largely unknown. Therefore, therapy is largely de-ndent on the initial clinical assessment of the patient.hen signs and symptoms are correctly interpreted, the ap-cation of research-based therapeutic guidelines can lead toatment success. According to literature, a positive out-e can be achieved by therapy in 75 to 90% of pa-

nts.59-64

A wide consensus has been reached through the years onsidering conservative and reversible approaches as first-linerapy of symptomatic disc derangement.65-69 Included in thisupare variousmedications, suchasnonsteroidal anti-inflam-tory drugs and muscle relaxant, oral appliances, home carecedures, and cognitive-behavioral information program.en these approaches fail to produce clinical improvementspainful dysfunctional conditions of the TMJ, surgical proce-

ogy during the stages of anterior derangement. In af the TMJ, and it glides during jaw opening betweencondylar head rotates and translates in the anteriorip with the condyle and temporal eminence. Stage 2,found in the closed-mouth position. Posterior bandal at full open-mouth position. Stage 3-4, closed lockjaw opening. Severe anterior displacement of disc

not displayed in the drawing (see the text for furtherrempeWplitrecomtie

conthegromaproWhon

orpholfaces oy, theationshent isnormduringe 1 isres (ie, arthrocentesis, arthroscopic surgery, discoplasty, andcectomy) may be indicated. Several case-based studies have

200 F. Molinari et al.

shoincsivcan

wipoThinscitheteepotomtieass

repofocapfor

al andsuggestarge arreducinws). Td is retage IVthe pared onmal opndylarhe abil

TMJ soft-tissue pathology 201wn that surgical management may be effective. However, torease the chances of treatment success in patients not respon-e to conservative therapy, the least invasive procedure thatbe effective should be first proposed.

Oral appliances (Fig. 9G and H) are used in patientsth symptomatic disc derangement for stabilizing or re-sitioning the occlusal maxillomandibular relationship.e stabilizing approach is reversible. It produces changesthe occlusal behavior of the patient, by inducing con-ousness of any oral parafunction. Therefore, it reduceschance of further wear, chipping, or cracking of the

th. In unstable occlusion caused by absence of multiplesterior contacts bilaterally, stabilization restores the au-atism of normal occlusion. It is also indicated in pa-

nts suffering from bruxism and for managing symptomsociated with TMJ disc derangement.70 The mandibular

Figure 7 Fast spin-echo DP-weighted MR images in closedsubjects. Images in the first line indicate the normal positImages in the second line (C, D) were obtained from a nuaccident, she reported lateral deviation of the jaw and transfrom the TMJ of the affected side occurred after she fordisplacement of the articular disc in centric occlusion (D),the third line (E, F) are relative to a young woman with aopening, after repeated episodes of jaw blockage in openappears dislocated anteriorly. The superior contour of the din the upper joint compartment. In the open-mouth positiofossa, suggesting a limitation in the forward translation of t

Figure 8 Example from a patient with inconsistent clinicclosed-mouth position (A), the T2*-weighted MR imageposterior band is positioned beyond the condylar head (lspatially adjacent T2*-weighted MR images confirm a nonto the articular eminence and the condylar head (small arrois twisted. Concurrently, the roundness of the condylar heaalterations can be found. Based on these MRI findings, a sdisplacement was not reduced by jaw opening. However,derangement, because he was asymptomatic and had referintermittent locking. Physical examination had shown northe MR images in the open-mouth position (B, C) as the coclinical-radiological inconsistencies can be explained by tloading conditions (see the text for further details).upper joint cavity collects into the increased concavity. The condydisc, which acts as an obstacle to the movement of the TMJ.ositioning appliance has deeper effects on the positionmaximum intercuspation and may cause a permanentclusal change.71,72 The theory behind the use of thispliance is to shift the mandibular condyles in a moreward position and, therefore, to allow for recapturing ofisplaced disc.73 This appliance is often used in patientsth painful clicking or intermittent locking. However,results of this strategy may not be as good as expected.

ng-term case report studies have suggested that TMJcking may recur over time and, even without audiblent sounds, disc position can remain altered.74-77

onclusionsder nonphysiologic loading, the various structures of theJ show adaptative and compensatory responses to prevent

, F) and open (A, C, E) mouth position, from threethe articular disc in an asymptomatic subject (A, B).posed to face trauma at work. Immediately after theficulty in mouth opening. Reciprocal clicking soundsjaw open. The MR examination revealed anterior

eduction in full open-mouth position (C). Images innth history of bilateral TMJ pain and limited mouthposition. In resting position (F), the articular disc

lso slightly concave, retaining a small fluid collectionhe condylar head remains almost stuck in the glenoiddyle itself. The disc is bent inferiorly. The fluid in the

MRI findings of anterior disc derangement. In thes anterior displacement of the articular disc, whoserow). In the open-mouth position (B to C), the twog disc displacement, as the disc is located anteriorlyhe shape of the disc is deeply altered and its structureduced and, just below its articular surface, MR signaldisc derangement might be suspected, because thetient had been clinically classified as a stage II discly occasional episodes of limited mouth opening andening range of the mouth. This may be sensed fromhead appears beyond the articular eminence. Theseity of the TMJ tissues to remodel under unfavorablea dwitheLoclijoi

CUnTM

(B, Dion ofrse exient difced thewith r2-mo-mouthisc is an (E), the conlar head does not pass over the posterior band of the

pepemoDichpamitioasytha

Re1.

2.

3.

4.

pect of

202 F. Molinari et al.rmanent tissue damages and allow for function. Decom-nsation and degenerative changes may occur when TMJdeling is unable to restore a biomechanical equilibrium.sc derangements may lead to altered loading and regressiveanges in the TMJ. However, because of the adaptative ca-city of the joint, these changes may be asymptomatic ornimally evident for a long time. A careful clinical evalua-n, reinforced by imaging findings, should help distinguishmptomatic disc derangements from pathologic conditionst may require treatment.

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Figure 9 Phases of clinical examination of a patient with susplanning with oral appliance on the maxillary arch (G tevaluated, noting developmental abnormalities, trauma, anopening movement of the mouth (B) should be assessed.derangements. The range of motion in the vertical plane (Cfor women. If the interincisal distance differs largely betwopening, a muscle based limitation should be suspected. Inand their possible limitations should be assessed. Joint soun(F) during jaw movements. However, clicking is unspepalpation, performed both from common external approamuscle tension and alterations of muscular trophism. Fintogenic causes of patients orofacial pain or parafunctionalappliance of the upper maxillary bone (G, H). (Color vers(ed). Science and Practice of Occlusion. Chicago, IL, QuintessencePublishing Co., Inc., 1997, pp 23-40Tanaka E, van Eijden T: Biomechanical behavior of the temporoman-dibular joint disc. Crit Rev Oral Biol Med 14:138-150, 2003Scapino RP, Canham PB, Finlay HM, et al: The behaviour of collagenfibres in stress relaxation and stress distribution in the jaw-joint disc ofrabbits. Arch Oral Biol 41:1039-1052, 1996Teng S, Xu Y, Cheng M, et al: Biomechanical properties and collagenfiber orientation of temporomandibular joint discs in dogs: 2. Tensilemechanical properties of the discs. J Craniomandib Disord 5:107-114,1991Mills DK, Fiandaca DJ, Scapino RP: Morphologic, microscopic, andimmunohistochemical investigations into the function of the primateTMJ disc. J Orofac Pain 8:136-154, 1994Minarelli AM, Del Santo M Jr, Liberti EA: The structure of the humantemporomandibular joint disc: a scanning electron microscopy study. JOrofac Pain 11:95-100, 1997del Pozo R, Tanaka E, Tanaka M, et al: The regional difference ofviscoelastic property of bovine temporomandibular joint disc in com-pressive stress-relaxation. Med Eng Phys 24:165-71, 2002Carvalho RS, Yen EH, Suga DM: Glycosaminoglycan synthesis in the ratarticular disk in response to mechanical stress. Am J Orthod Dentofa-cial Orthop 107:401-410, 1995Sindelar BJ, Evanko SP, Alonzo T, et al: Effects of intraoral splint wearon proteoglycans in the temporomandibular joint disc. Arch BiochemBiophys 379:64-70, 2000Kuboki T, Shinoda M, Orsini MG, et al: Viscoelastic properties of the

a TMJ disorder (A to F) and conservative therapeuticIn each patient, face symmetry (A) should be firstling of external tissues. Similarly, the symmetry of theeviations at jaw opening may suggest unilateral discrmal subjects is 40 3 mm for men and slightly lessaximum-unassisted opening and maximum-assistedrizontal plane, lateral and protrusive jaw movementuld be evaluated with palpation (D) and auscultationeing heard also in asymptomatic subjects. Muscle) and from intraoral manipulation (E), might revealtraoral examination should consider possible odon-that have special relevance to myofascial pain. Oralgure is available online.)5.

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204 F. Molinari et al.

Temporomandibular Joint Soft-Tissue Pathology, I: Disc AbnormalitiesBiomechanical Properties of the DiscDisc Abnormalities: Internal DerangementsDefinition and PathophysiologyClassification and Clinical Course

Clinical Assessment of Temporomandibular Disorders and Diagnostic ProtocolsTherapeutic OutlinesConclusionsReferences