Temporomandibular Joint

Classification The temporomandibular joint (TMJ) is composed of the temporal

bone and the mandible, as well as a specialized dense fibrousstructure, the articular disk, several ligaments, and numerousassociated muscles.

The TMJ is a compound joint that can be classified by anatomictype as well as by function.

Anatomically the TMJ is a diarthrodial joint, which is adiscontinuous articulation of two bones permitting freedom ofmovement that is dictated by associated muscles and limited byligaments.

Its fibrous connective tissue capsule is well innervated and wellvascularized and tightly attached to the bones at the edges oftheir articulating surfaces. It is also a synovial joint, lined on itsinner aspect by a synovial membrane, which secretes synovialfluid. The fluid acts as a joint lubricant and supplies the metabolicand nutritional needs of the nonvascularized internal jointstructures.

Functionally the TMJ is a compound joint,composed of four articulating surfaces: thearticular facets of the temporal bone and of themandibular condyle and the superior and inferiorsurfaces of the articular disk.

The articular disk divides the joint into twocompartments. The lower compartment permitshinge motion or rotation and hence is termedginglymoid.

The superior compartment permits sliding (ortranslatory) movements and is therefore calledarthrodial. Hence the temporomandibular joint asa whole can be termed ginglymoarthrodial.

Bony Structures

The articular portion of the temporal bone is

composed of three parts.

The largest is the articular or mandibular fossa, a

concave structure extending from the posterior

slope of the articular eminence to the postglenoid

process, which is a ridge between the fossa and

the external acoustic meatus.

The surface of the articular fossa is thin and may

be translucent on a dry skull. This is not a major

stress-bearing area.

A, The left temporomandibular joint

viewed from the sagittal aspect on a

dry skull.

B, The left temporomandibular joint

viewed from the oblique/coronal

aspect on a dry skull.

C, The left glenoid fossa and

articular eminence.

The second portion, the articular eminence, is a

transverse bony prominence that is continuous

across the articular surface mediolaterally. The

articular eminence is usually thick and serves as

a major functional component of the TMJ.

The articular eminence is distinguished from the

articular tubercle, a nonarticulating process on

the lateral aspect of the zygomatic root of the

temporal bone, which serves as a point of

attachment of collateral ligaments.

The third portion of the articular surface of the

temporal bone is the preglenoid plane, a flattened

area anterior to the eminence.

The mandible is a U-shaped bone that articulates

with the temporal bone by means of the articular

surface of its condyles, paired structures forming

an approximately 145° to 160° angle to each

other. The mandibular condyle is approximately

15 to 20 mm in width and 8 to 10 mm in

anteroposterior dimension.

The condyle tends to be rounded mediolaterally

and convex anteroposteriorly.

On its medial aspect just below its articular

surface is a prominent depression, the pterygoid

fovea, which is the site of attachments of the

lateral pterygoid muscle.

The mandibular condyle

Cartilage and Synovium Lining the inner aspect of all synovial joints, including

the TMJ, are two types of tissue: articular cartilageand synovium. The space bound by these twostructures is termed the synovial cavity, which is filledwith synovial fluid.

The articular surfaces of both the temporal bone andthe condyle are covered with dense articularfibrocartilage, a fibrous connective tissue. Thisfibrocartilage covering has the capacity to regenerateand to remodel under functional stresses.

Deep to the fibrocartilage, particularly on the condyle,is a proliferative zone of cells that may develop intoeither cartilaginous or osseous tissue. Most changeresulting from function is seen in this layer.

The temporomandibular

joint (coronal view).

Articular cartilage is composed of chondrocytes andan intercellular matrix of collagen fibers, water, and anonfibrous filler material, termed ground substance.

Chondrocytes are enclosed in otherwise hollowspaces, called lacunae, and are arranged in threelayers characterized by different cell shapes.

The superficial zone contains small flattened cellswith their long axes parallel to the surface.

In the middle zone the cells are larger and roundedand appear in columnar fashion perpendicular to thesurface.

The deep zone contains the largest cells and isdivided by the “tide mark” below which some degreeof calcification has occurred. There are few bloodvessels in any of these areas, with cartilage beingnourished primarily by diffusion from the synovialfluid.

Articular cartilage

Collagen fibers are arranged in arcades with aninterlocking meshwork of fibrils parallel to thearticular surface joining together as bundles anddescending to their attachment in the calcifiedcartilage between the tide mark.

Functionally these arcades provide a frameworkfor interstitial water and ground substance toresist compressive forces encountered in jointloading.

Formed by intramembranous processes theTMJ’s articular cartilage contains a greaterproportion of collagen fibers (fibrocartilage) thanother synovial joints, which are covered insteadby hyaline cartilage.

Articular cartilage

The ground substance contains a variety of plasma

proteins, glucose, urea, and salts, as well as

proteoglycans, which are synthesized by the

Golgi apparatus of the chondrocytes. Proteoglycans

are macromolecules consisting of a protein core

attached to many glycosaminoglycan chains of

chondroitin sulfate and keratan sulfate.

Proteoglycans play a role in the diffusion of nutrients

and metabolic breakdown products. Ground

substance permits the entry and release of large

quantities of water, an attribute thought to be

significant in giving cartilage its characteristic

functional elasticity in response to deformation and

loading.

Lining the capsular ligament is the synovialmembrane, a thin, smooth, richly innervated vasculartissue without an epithelium.

Synovial cells, somewhat undifferentiated inappearance, serve both a phagocytic and a secretoryfunction and are thought to be the site of production ofhyaluronic acid, a glycosaminoglycan found insynovial fluid.

Some synovial cells, particularly those in closeapproximation to articular cartilage, are thought tohave the capacity to differentiate into chondrocytes.The synovium is capable of rapid and completeregeneration following injury.

Recently, synovial cells (as well as chondrocytes andleukocytes) have been the focus of extensiveresearch regarding the production of anabolic andcatabolic cytokines within the TMJ.

Synovial fluid is considered an ultrafiltrate of plasma.It contains a high concentration of hyaluronic acid,which is thought to be responsible for the fluid’s highviscosity.

The proteins found in synovial fluid are identical toplasma proteins; however, synovial fluid has a lowertotal protein content, with a higher percentage ofalbumin and a lower percentage of α-2-globulin.

Alkaline phosphatase, which may also be present insynovial fluid, is thought to be produced bychondrocytes.

Leukocytes are also found in synovial fluid, with thecell count being less than 200 per cubic millimeterand with less than 25% of these cells beingpolymorphonuclear.

Only a small amount of synovial fluid, usually lessthan 2 mL, is present within the healthy TMJ.

Functions of the synovial fluid include lubrication of

the joint, phagocytosis of particulate debris, and

nourishment of the articular cartilage.

Joint lubrication is a complex function related to the

viscosity of synovial fluid and to the ability of articular

cartilage to allow the free passage of water within the

pores of its glycosaminoglycan matrix.

Application of a loading force to articular cartilage

causes a deformation at the location. It has been

theorized that water is extruded from the loaded area

into the synovial fluid adjacent to the point of contact.

The concentration of hyaluronic acid and hence the

viscosity of the synovial fluid is greater at the point of

load, thus protecting the articular surfaces.

As the load passes to adjacent areas the

deformation passes on as well, while the original

point of contact regains its shape and thickness

through the reabsorption of water.

Exact mechanisms of flow between articular

cartilage and synovial fluid are as yet unclear.

Nevertheless the net result is a coefficient of

friction for the normally functioning joint—

approximately 14 times less than that of a dry

joint.

The Articular Disk The articular disk is composed of dense fibrous

connective tissue and is nonvascularized andnoninnervated, an adaptation that allows it to resistpressure.

Anatomically the disk can be divided into threegeneral regions as viewed from the lateralperspective: the anterior band, the centralintermediate zone, and the posterior band.

The thickness of the disk appears to be correlatedwith the prominence of the eminence. Theintermediate zone is thinnest and is generally the areaof function between the mandibular condyle and thetemporal bone.

The temporomandibular joint (lateral view).

Despite the designation of separate portions of

the articular disk, it is in fact a homogeneous

tissue and the bands do not consist of specific

anatomic structures.

The disk is flexible and adapts to functional

demands of the articular surfaces.

The articular disk is attached to the capsular

ligament anteriorly, posteriorly, medially, and

laterally.

Some fibers of the superior head of the lateral

pterygoid muscle insert on the disk at its medial

aspect, apparently serving to stabilize the disk to

the mandibular condyle during function.

Retrodiskal Tissue Posteriorly the articular disk blends with a highly vascular,

highly innervated structure— the bilaminar zone, which is

involved in the production of synovial fluid.

The superior aspect of the retrodiskal tissue contains

elastic fibers and is termed the superior retrodiskal lamina,

which attaches to the tympanic plate and functions as a

restraint to disk movement in extreme translatory

movements.

The inferior aspect of the retrodiskal tissue, termed the

inferior retrodiskal lamina, consists of collagen fibers

without elastic tissue and functions to connect the articular

disk to the posterior margin of the articular surfaces of the

condyle.

It is thought to serve as a check ligament to prevent

extreme rotation of the disk on the condyle in rotational

movements.

Ligaments Ligaments associated with the TMJ are composed of

collagen and act predominantly as restraints to motionof the condyle and the disk.

Three ligaments—collateral, capsular, andtemporomandibular ligaments— are consideredfunctional ligaments because they serve as majoranatomic components of the joints.

Two other ligaments—sphenomandibular andstylomandibular— are considered accessoryligaments because, although they are attached toosseous structures at some distance from the joints,they serve to some degree as passive restraints onmandibular motion.

The collateral (or diskal) ligaments are short

paired structures attaching the disk to the

lateral and medial poles of each condyle.

Their function is to restrict movement of the

disk away from the condyle, thus allowing

smooth synchronous motion of the disk-

condyle complex.

Although the collateral ligaments permit

rotation of the condyle with relation to the

disk, their tight attachment forces the disk to

accompany the condyle through its translatory

range of motion.

The capsular ligament encompasses each joint,attaching superiorly to the temporal bone along theborder of the mandibular fossa and eminence andinferiorly to the neck of the condyle along the edge ofthe articular facet. It surrounds the joint spaces andthe disk, attaching anteriorly and posteriorly as well asmedially and laterally, where it blends with thecollateral ligaments.

The function of the capsular ligament is to resistmedial, lateral, and inferior forces, thereby holding thejoint together. It offers resistance to movement of thejoint only in the extreme range of motion. A secondaryfunction of the capsular ligament is to contain thesynovial fluid within the superior and inferior jointspaces.

Capsular ligament (lateral view).

Temporomandibular joint

(lateral aspect)

The temporomandibular (lateral) ligaments arelocated on the lateral aspect of each TMJ. Unlike thecapsular and collateral ligaments, which have medialand lateral components within each joint, thetemporomandibular ligaments are single structuresthat function in paired fashion with the correspondingligament on the opposite TMJ. Eachtemporomandibular ligament can be separated intotwo distinct portions, that have different functions.

The outer oblique portion descends from the outeraspect of the articular tubercle of the zygomaticprocess posteriorly and inferiorly to the outer posteriorsurface of the condylar neck. It limits the amount ofinferior distraction that the condyle may achieve intranslatory and rotational movements.

The inner horizontal portion also arises from the

outer surface of the articular tubercle, just medial

to the origin of the outer oblique portion of the

ligament, and runs horizontally backward to

attach to the lateral pole of the condyle and the

posterior aspect of the disk.

The function of the inner horizontal portion of the

temporomandibular ligament is to limit posterior

movement of the condyle, particularly during

pivoting movements, such as when the mandible

moves laterally in chewing function. This

restriction of posterior movement serves to

protect the retrodiskal tissue.

The sphenomandibular ligament arises from the spine

of the sphenoid bone and descends into the fan-like

insertion on the mandibular lingula, as well as on the

lower portion of the medial side of the condylar neck.

The sphenomandibular ligament serves to some

degree as a point of rotation during activation of the

lateral pterygoid muscle, thereby contributing to

translation of the mandible.

The stylomandibular ligament descends from the

styloid process to the posterior border of the angle of

the mandible and also blends with the fascia of the

medial pterygoid muscle. It functions similarly to the

sphenomandibular ligament as a point of rotation and

also limits excessive protrusion of the mandible.

Temporomandibular ligament

(medial view).

Vascular Supply and Innervation The vascular supply of the TMJ arises primarily from

branches of the superficial temporal and maxillary arteriesposteriorly and the masseteric artery anteriorly.

There is a rich plexus of veins in the posterior aspect of thejoint associated with the retrodiskal tissues, whichalternately fill and empty with protrusive and retrusivemovements, respectively, of the condyle disk complex andwhich also function in the production of synovial fluid.

The nerve supply to the TMJ is predominantly frombranches of the auriculotemporal nerve with anteriorcontributions from the masseteric nerve and the posteriordeep temporal nerve. Many of the nerves to the jointappear to be vasomotor and vasosensory, and they mayhave a role in the production of synovial fluid.

Musculature All muscles attached to the mandible influence its

movement to some degree. Only the four largemuscles that attach to the ramus of the mandible areconsidered the muscles of mastication; however, atotal of 12 muscles actually influence mandibularmotion, all of which are bilateral. Muscle pairs mayfunction together for symmetric movements orunilaterally for asymmetric movement.

For example, contraction of both lateral pterygoidmuscles results in protrusion and depression of themandible without deviation, whereas contraction ofone of the lateral pterygoid muscles results inprotrusion and opening with deviation to the oppositeside.

Muscles influencing mandibular motion may be divided into two

groups by anatomic position. Attaching primarily to the ramus

and condylar neck of the mandible is the supramandibular

muscle group, consisting of the temporalis, masseter, medial

pterygoid, and lateral pterygoid muscles.

This group functions predominantly as the elevators of the

mandible. The lateral pterygoid does have a depressor function

as well. Attaching to the body and symphyseal area of the

mandible and to the hyoid bone is the inframandibular group,

which functions as the depressors of the mandible. The

inframandibular group includes the four suprahyoid muscles

(digastric, geniohyoid, mylohyoid, and stylohyoid) and the four

infrahyoid muscles (sternohyoid, omohyoid, sternothyroid, and

thyrohyoid).

The suprahyoid muscles attach to both the hyoid bone and the

mandible and serve to depress the mandible when the hyoid

bone is fixed in place. They also elevate the hyoid bone when

the mandible is fixed in place. The infrahyoid muscles serve to fix

the hyoid bone during depressive movements of the mandible.

Supramandibular Muscle Group The temporalis muscle is a large fan-shaped muscle

taking its origin from the temporal fossa and lateralaspect of the skull, including portions of the parietal,temporal, frontal, and sphenoid bones. Its fibers passbetween the zygomatic arch and the skull and inserton the mandible at the coronoid process and anteriorborder of the ascending ramus down to the occlusalsurface of the mandible, posterior to the third molartooth.

Viewed coronally the temporalis muscle has abipennate character in that fibers arising from theskull insert on the medial aspect of the coronoidprocess, whereas fibers arising laterally from thetemporalis fascia insert on the lateral aspect of thecoronoid process.

The temporalis muscle with the zygomatic arch

and masseter muscle removed.

In an anteroposterior dimension the temporalismuscle consists of three portions: the anterior,whose fibers are vertical; the middle, with obliquefibers; and the posterior portion, withsemihorizontal fibers passing forward to bendunder the zygomatic arch.

The function of the temporalis muscle is toelevate the mandible for closure. It is not a powermuscle. In addition contraction of the middle andposterior portions of the temporalis muscle cancontribute to retrusive movements of themandible. To a small degree unilateral contractionof the temporalis assists in deviation of themandible to the ipsilateral side.

The masseter muscle, a short rectangular muscle taking itsorigin from the zygomatic arch and inserting on the lateralsurface of the mandible, is the most powerful elevator ofthe mandible and functions to create pressure on the teeth,particularly the molars, in chewing motions.

The masseter muscle is composed of two portions,superficial and deep, which are incompletely divided, yethave somewhat different functions. The superficial portionoriginates from the lower border of the zygomatic bone andthe anterior two-thirds of the zygomatic arch and passesinferiorly and posteriorly to insert on the angle of themandible.

The deep head originates from the inner surface of theentire zygomatic arch and on the posterior one-third of thearch from its lower border. The deep fibers pass verticallyto insert on the mandible on its lateral aspect above theinsertion of the superficial head.

The superficial portion in particular has a multipennateappearance with alternating tendinous plates and fleshybundles of muscle fibers, which serve to increase thepower of the muscle.

Both the superficial and deep portions of the massetermuscle are powerful elevators of the mandible, but theyfunction independently and reciprocally in othermovements.

Electromyographic studies show that the deep layer of themasseter is always silent during protrusive movementsand always active during forced retrusion, whereas thesuperficial portion is active during protrusion and silentduring retrusion.

Similarly the deep masseter is active in ipsilateralmovements but does not function in contralateralmovements, whereas the superficial masseter is activeduring contralateral movements but not in ipsilateralmovements.

The masseter muscle

The medial pterygoid muscle is rectangular and takes

its origin from the pterygoid fossa and the internal

surface of the lateral plate of the pterygoid process,

with some fibers arising from the tuberosity of the

maxilla and the palatine bone. Its fibers pass inferiorly

and insert on the medial surface of the mandible,

inferiorly and posteriorly to the lingual.

Like the masseter muscle the medial pterygoid fibers

have alternating layers of fleshy and tendinous parts,

thereby increasing the power of the muscle. The main

function of the medial pterygoid is elevation of the

mandible, but it also functions somewhat in unilateral

protrusion in a synergism with the lateral pterygoid to

promote rotation to the opposite side.

The lateral pterygoid muscle has two portions that canbe considered two functionally distinct muscles. Thelarger inferior head originates from the lateral surfaceof the lateral pterygoid plate. Its fibers pass superiorlyand outward to fuse with the fibers of the superiorhead at the neck of the mandibular condyle, insertinginto the pterygoid fovea.

The superior head originates from the infratemporalsurface of the greater sphenoid wing, and its fiberspass inferiorly, posteriorly, and outward to insert in thesuperior aspect of the pterygoid fovea, the articularcapsule, and the articular disk at its medial aspect, aswell as to the medial pole of the condyle. Anatomicstudies have shown that the majority of the superiorhead fibers insert into the condyle rather than thedisk.

The inferior and superior heads of the lateralpterygoid muscle function independently andreciprocally. The primary function of the inferior headis protrusive and contralateral movement. When thebilateral inferior heads function together, the condyleis pulled forward down the articular eminence, withthe disk moving passively with the condylar head.

This forward movement of the condyle down theinclined plane of the articular eminence alsocontributes to opening of the oral cavity. When theinferior head functions unilaterally the resulting medialand protrusive movement of the condyle results incontralateral motion of the mandible. The function ofthe superior head of the lateral pterygoid muscle ispredominantly involved with closing movements of thejaw and with retrusion and ipsilateral movement.

Medial and lateral pterygoid muscles

Inframandibular Muscle Group The inframandibular muscles can be subdivided into two

groups: the suprahyoids and the infrahyoids. Thesuprahyoid group consists of the digastric,geniohyoid,mylohyoid, and stylohyoid muscles; liesbetween the mandible and the hyoid bone; and serves toeither raise the hyoid bone, if the mandible is fixed inposition by the supramandibular group, or depress themandible, if the hyoid bone is fixed in position by theinfrahyoids.

The infrahyoid group, consisting of the sternohyoid,omohyoid, sternothyroid, and thyrohyoid muscles, attachesto the hyoid bone superiorly and to the sternum, clavicle,and scapula inferiorly. This group of muscles can eitherdepress the hyoid bone or hold the hyoid bone in position,relative to the trunk, during opening movements of themandible.

Biomechanics of Temporomandibular

Joint Movement Complex free movements of the mandible are made possible by

the relation of four distinct joints that are involved in mandibularmovement: the inferior and superior joints—bilaterally. Two typesof movement are possible: rotation and translation.

The inferior joints, consisting of the condyle and disk, areresponsible for rotation, a hinge-like motion. The center ofrotation is considered to be along a horizontal axis passingthrough both condyles.

In theory pure hinge motion of approximately 2.5 cm measuredat the incisal edges of the anterior teeth is possible.

Nevertheless most mandibular movements are translatory aswell, involving a gliding motion between the disk and thetemporal fossa, which are the components of the superior joints.

The mandible and disk glide together as a unit because they areheld together by the collateral ligaments. The maximum forwardand lateral movement of the upper joint in translation isapproximately 1.5 cm.

All movements of the mandible, whether

symmetric or asymmetric, involve close contact of

the condyle, disk, and articular eminence. Pure

opening, closing, protrusive, and retrusive

movements are possible as a result of bilaterally

symmetric action of the musculature.

Asymmetric movements, such as those seen in

chewing, are made possible by unilateral

movements of the musculature with different

amounts of translation and rotation occurring

within the joints on either side.

The positioning of the condyle and disk within the

fossa, as well as the constant contact between

the condyle, disk, and eminence, is maintained by

continuous activity of the muscles of mastication,

particularly the supramandibular group.

The ligaments associated with the TMJ do not

move the joint. Although they can be lengthened

by movements of muscles, they do not stretch (ie,

do not have an elastic recoil that returns them to

a resting position automatically).

Instead the role of the ligaments is that of a

passive restriction of movement at the extreme

ranges of motion. During normal function

rotational and translational movements occur

simultaneously, permitting the free range of

motion necessary in speaking and chewing.

EVALUATION

The evaluation of the patient with

temporomandibular pain, dysfunction, or both is

like that in any other diagnostic work up.

This evaluation should include a thorough history,

a physical examination of the masticatory system,

and problem-focused TMJ radiography.

Interview The patient's history may be the most important part of the

evaluation because it furnishes clues for the diagnosis.The history begins with the chief complaint, which is astatement of the patient's reasons for seeking consultationor treatment.

The history of the present illness should becomprehensive, including an accurate description of thepatient's symptoms, chronology of the symptoms,description of how the problem affects the patient andinformation about any previous treatments (including thepatient's response to those treatments).

To have patients complete a general questionnaire is oftenuseful to help provide information about the history of theirproblem. The use of a visual analog pain scale may alsohelp obtain an under· standing of the patient's perceptionof the severity of their pain.

Examination The physical examination consists of an

evaluation of the entire masticatory system. The

head and neck should be inspected for soft tissue

asymmetry or evidence of muscular hypertrophy.

The patient should be observed for signs of jaw

clenching or other habits. The masticatory

muscles should be examined systematically. The

muscles should be palpated for the presence of

tenderness, fasciculations, spasm, or trigger

points.

Systematic evaluation of muscles of

mastication.

A, Palpation of masseter muscle.

B, Palpation of temporalis muscle.

C, Palpation of temporalis tendon

attachment on coronoid process

and ascending ramus.

The TMJs are examined for tenderness andnoise. The location of the joint tenderness (e.g.,lateral or posterior) should be noted. If the joint ismore painful during different areas of the openingcycle or with different types of functions, thisshould be recorded.

The most common forms of joint noise areclicking (a distinct sound) and crepitus (i.e.,scraping or grating sounds). Many joint soundscan be easily heard without specialinstrumentation or can be felt during palpation ofthe joint; however, in some cases auscultationwith a stethoscope may allow less obvious jointsounds, such as mild crepitus, to be appreciated.

Evaluation or temporomandibular

joint for tenderness and noise. Joint

is palpated laterally in closed

position (A) and open position (B).

The mandibular range of motion should bedetermined. Normal range of movement of an adult'smandible is about 45 mm vertically (i.e., interincisally)and 10 mm protrusively and laterally.

The normal movement is straight and symmetric. Insome cases, tenderness in the joint or muscle areasmay prevent opening. The clinician should attempt toascertain not only the painless voluntary opening butalso the maximum opening that can be achieved withgentle digital pressure.

In some cases the patient may appear to have amechanical obstruction in the joint causing limitedopening but with gentle pressure may actually be ableto achieve near normal opening. This may suggestmuscular rather than intracapsular problems.

Measurement of

range of jaw

motion.

A, Maximum

voluntary vertical

opening.

B, Evaluation or

lateral excursive

movement

(should be

approximately 10

mm). Protrusive

movements

should be similar

to excursion.

The dental evaluation is also important. Odontogenicsources of pain should be eliminated. The teethshould be examined for wear facets, soreness, andmobility, which may be evidence of bruxism.

Although the Significance of occlusal abnormalities iscontroversial, the occlusal relationship should beevaluated and documented. Missing teeth should benoted, and dental and skeletal classification should bedetermined.

The clinician should note any centric relation andcentric occlusion discrepancy or Significant posturingby the patient. The examination findings can besummarized on a TMD evaluation form and includedin the patient's chart. In many cases a more detailedchart note may be necessary to document adequatelyall of the history and examination findings describedpreviously.

Radiographic Evaluation Radiographs of the TMJ are helpful in the

diagnosis of intraarticular, osseous, and softtissue pathologic conditions. The use ofradiographs in the evaluation of the patient withTMD should be based on the patient's signs andsymptoms instead of routinely ordering astandard set of radiographs. In many cases thepanoramic radiograph provides adequateinformation as a screening radiograph inevaluation of TMD. A variety of other radiographictechniques are available that may provide usefulinformation in certain cases.

Panoramic Radiography One of the best overall radiographs for screening

evaluation of the TMJs is the panoramic radiograph.This technique allows visualization of both TMJs onthe same film.

Because a panoramic technique provides atomographic-type view of the TMJ , this can frequentlyprovide a good assessment of the bony anatomy ofthe articulating surfaces of the mandibular condyleand glenoid fossa; and other areas, such as thecoronoid process, can also be visualized.

Many machines are equipped to provide special viewsof the mandible, focusing primarily on the area of theTMJs. These radiographs can often be complete inthe open and closed position.

Panoramic imaging. A, Normal anatomy or right

condyle. B, Imaging illustrates degenerative changes or

left condyle via remodeling.

Tomograms

The tomographic technique allows a more

detailed view of the TMJ. This technique allows

radiographic sectioning of the joint at different

levels of the condyle and fossa complex, which

provides individual views visualizing the joint in

"slices" from the medial to the lateral pole. These

views eliminate bony superimposition and overlap

and provide a relatively clear picture of the bony

anatomy of the joint.

Temporomandibular Joint

Arthrography This imaging method was the first technique available

that allowed visualization (indirect) of the intraarticular disk. Arthrography involves the injection ofcontrast material into the inferior or superior spaces ofa joint, after which the joint is radiographed.

Evaluation of the configuration of the dye in the jointspaces allows evaluation of the position andmorphology of the articular disk.

This technique also demonstrates the presence ofperforations and adhesions of the disk or itsattachments. With the availability of more advanced,less invasive techniques, arthrography is rarely used.

Arthrogram shows dye in inferior and superior joint spaces.

Anatomy and location of disk is indirectly interpreted from dye

pattern observed after injection of joint spaces above and below

disk. This arthrogram demonstrates anterior disk displacement

without reduction. A, Closed position. B, Open position.

Computed Tomography Computed tomography (CT) provides a combination

of tomographic views of the joint, combined withcomputer enhancement of hard and soft tissueimages. This technique allows evaluation of a varietyof hard and soft tissue pathologic conditions in thejoint. CT images provide the most accurateradiographic assessment of the bony components ofthe joint.

CT scan reconstruction capabilities allow imagesobtained in one plane of space to be reconstructed sothat the images can be evaluated from a differentview. Thus evaluation of the joint from a variety ofperspectives can be made from a single radiationexposure.

Computerized

tomography.

A , Coronal images

illustrate normal

architecture of the right

(R) condyle with

alteration

of the left condyle

resulting from a history

of trauma.

B, Axial views depict

the altered condylar

anatomy referenced

against the

contralateral joint.

Magnetic Resonance Imaging The most effective diagnostic imaging technique to

evaluate TMJ soft tissues is magnetic resonance

imaging.

This technique allows excellent images of intra

articular soft tissue, making MRI a valuable technique

for evaluating disk morphology and position.

MRI images can be obtained showing dynamic joint

function in a cinematic fashion, providing valuable

information about the anatomic components of the

joint during function. The fact that this technique does

not use ionizing radiation is a significant advantage.

Magnetic resonance image. A, Normal positioning of the

articular disk between the articular eminence and condyle

during translation. B, Image demonstrates anterior disk

displacement without reduction, limiting range of motion.

Nuclear Imaging Nuclear medicine studies involve intravenous injection

of technetium-99, a y-emitting isotope that isconcentrated in areas of active bone metabolism.Approximately 3 hours after injection of the isotope,images are obtained using a gamma camera. Single-photon emission computerized tomography imagescan then be used to determine active areas of bonemetabolism.

Although this technique is extremely sensitive, theinformation obtained may be difficult to interpret.Because bone changes, such as degeneration, mayappear identical to repair or regeneration, thistechnique must be evaluated cautiously and incombination with clinical findings.

Single-photon

emission computed

tomography (bone

scan). Area of

increased activity is

apparent in both

temporomandibular

joints.

Psychological Evaluation Many patients with temporomandibular pain and

dysfunction of long-standing duration developmanifestations of chronic pain syndrome behavior.

This complex may include gross exaggeration ofsymptoms and clinical depression. The comorbidity ofpsychiatric illness and temporomandibular dysfunctioncan be as high as 10% to 20% of patients seekingtreatment

A third of these patients is suffering from depressionat the time on initial presentation, whereas more thantwo thirds have had a severe depressive episode intheir history.

Psychiatric disorders may elicit somaticcomponents through parafunctional habitsresulting in dystonia and myalgia, and individualswith chronic pain commonly have a higherincidence of concomitant anxiety disorders.

Behavioral changes associated with pain anddysfunction can be elicited in the history throughquestions regarding functional limitation thatresults from the patient's symptoms.

If the functional limitation appears to be excessivecompared with the patient's clinical signs or thepatient appears to be clinically depressed, furtherpsychological evaluation may be warranted.