2. Classification
The temporomandibular joint (TMJ) is composed of the temporal
bone and the mandible, as well as a specialized dense fibrous
structure, the articular disk, several ligaments, and numerous
associated muscles.
The TMJ is a compound joint that can be classified by anatomic
type as well as by function.
Anatomically the TMJ is a diarthrodial joint, which is a
discontinuous articulation of two bones permitting freedom of
movement that is dictated by associated muscles and limited by
ligaments.
Its fibrous connective tissue capsule is well innervated and well
vascularized and tightly attached to the bones at the edges of
their articulating surfaces. It is also a synovial joint, lined on its
inner aspect by a synovial membrane, which secretes synovial
fluid. The fluid acts as a joint lubricant and supplies the metabolic
and nutritional needs of the nonvascularized internal joint
structures.
3. Functionally the TMJ is a compound joint,
composed of four articulating surfaces: the
articular facets of the temporal bone and of the
mandibular condyle and the superior and inferior
surfaces of the articular disk.
The articular disk divides the joint into two
compartments. The lower compartment permits
hinge motion or rotation and hence is termed
ginglymoid.
The superior compartment permits sliding (or
translatory) movements and is therefore called
arthrodial. Hence the temporomandibular joint as
a whole can be termed ginglymoarthrodial.
4. 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.
5. 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.
6. 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.
7. 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.
9. Cartilage and Synovium
Lining the inner aspect of all synovial joints, including
the TMJ, are two types of tissue: articular cartilage
and synovium. The space bound by these two
structures is termed the synovial cavity, which is filled
with synovial fluid.
The articular surfaces of both the temporal bone and
the condyle are covered with dense articular
fibrocartilage, a fibrous connective tissue. This
fibrocartilage covering has the capacity to regenerate
and to remodel under functional stresses.
Deep to the fibrocartilage, particularly on the condyle,
is a proliferative zone of cells that may develop into
either cartilaginous or osseous tissue. Most change
resulting from function is seen in this layer.
11. Articular cartilage is composed of chondrocytes and
an intercellular matrix of collagen fibers, water, and a
nonfibrous filler material, termed ground substance.
Chondrocytes are enclosed in otherwise hollow
spaces, called lacunae, and are arranged in three
layers characterized by different cell shapes.
The superficial zone contains small flattened cells
with their long axes parallel to the surface.
In the middle zone the cells are larger and rounded
and appear in columnar fashion perpendicular to the
surface.
The deep zone contains the largest cells and is
divided by the “tide mark” below which some degree
of calcification has occurred. There are few blood
vessels in any of these areas, with cartilage being
nourished primarily by diffusion from the synovial
fluid.
13. Collagen fibers are arranged in arcades with an
interlocking meshwork of fibrils parallel to the
articular surface joining together as bundles and
descending to their attachment in the calcified
cartilage between the tide mark.
Functionally these arcades provide a framework
for interstitial water and ground substance to
resist compressive forces encountered in joint
loading.
Formed by intramembranous processes the
TMJ’s articular cartilage contains a greater
proportion of collagen fibers (fibrocartilage) than
other synovial joints, which are covered instead
by hyaline cartilage.
15. 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.
16. Lining the capsular ligament is the synovial
membrane, a thin, smooth, richly innervated vascular
tissue without an epithelium.
Synovial cells, somewhat undifferentiated in
appearance, serve both a phagocytic and a secretory
function and are thought to be the site of production of
hyaluronic acid, a glycosaminoglycan found in
synovial fluid.
Some synovial cells, particularly those in close
approximation to articular cartilage, are thought to
have the capacity to differentiate into chondrocytes.
The synovium is capable of rapid and complete
regeneration following injury.
Recently, synovial cells (as well as chondrocytes and
leukocytes) have been the focus of extensive
research regarding the production of anabolic and
catabolic cytokines within the TMJ.
17. 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 high
viscosity.
The proteins found in synovial fluid are identical to
plasma proteins; however, synovial fluid has a lower
total protein content, with a higher percentage of
albumin and a lower percentage of α-2-globulin.
Alkaline phosphatase, which may also be present in
synovial fluid, is thought to be produced by
chondrocytes.
Leukocytes are also found in synovial fluid, with the
cell count being less than 200 per cubic millimeter
and with less than 25% of these cells being
polymorphonuclear.
Only a small amount of synovial fluid, usually less
than 2 mL, is present within the healthy TMJ.
18. 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.
19. 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.
20. The Articular Disk
The articular disk is composed of dense fibrous
connective tissue and is nonvascularized and
noninnervated, an adaptation that allows it to resist
pressure.
Anatomically the disk can be divided into three
general regions as viewed from the lateral
perspective: the anterior band, the central
intermediate zone, and the posterior band.
The thickness of the disk appears to be correlated
with the prominence of the eminence. The
intermediate zone is thinnest and is generally the area
of function between the mandibular condyle and the
temporal bone.
22. 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.
23. 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.
24. Ligaments
Ligaments associated with the TMJ are composed of
collagen and act predominantly as restraints to motion
of the condyle and the disk.
Three ligaments—collateral, capsular, and
temporomandibular ligaments— are considered
functional ligaments because they serve as major
anatomic components of the joints.
Two other ligaments—sphenomandibular and
stylomandibular— are considered accessory
ligaments because, although they are attached to
osseous structures at some distance from the joints,
they serve to some degree as passive restraints on
mandibular motion.
25. 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.
26.
27. The capsular ligament encompasses each joint,
attaching superiorly to the temporal bone along the
border of the mandibular fossa and eminence and
inferiorly to the neck of the condyle along the edge of
the articular facet. It surrounds the joint spaces and
the disk, attaching anteriorly and posteriorly as well as
medially and laterally, where it blends with the
collateral ligaments.
The function of the capsular ligament is to resist
medial, lateral, and inferior forces, thereby holding the
joint together. It offers resistance to movement of the
joint only in the extreme range of motion. A secondary
function of the capsular ligament is to contain the
synovial fluid within the superior and inferior joint
spaces.
30. The temporomandibular (lateral) ligaments are
located on the lateral aspect of each TMJ. Unlike the
capsular and collateral ligaments, which have medial
and lateral components within each joint, the
temporomandibular ligaments are single structures
that function in paired fashion with the corresponding
ligament on the opposite TMJ. Each
temporomandibular ligament can be separated into
two distinct portions, that have different functions.
The outer oblique portion descends from the outer
aspect of the articular tubercle of the zygomatic
process posteriorly and inferiorly to the outer posterior
surface of the condylar neck. It limits the amount of
inferior distraction that the condyle may achieve in
translatory and rotational movements.
31. 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.
32. 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.
34. Vascular Supply and Innervation
The vascular supply of the TMJ arises primarily from
branches of the superficial temporal and maxillary arteries
posteriorly and the masseteric artery anteriorly.
There is a rich plexus of veins in the posterior aspect of the
joint associated with the retrodiskal tissues, which
alternately fill and empty with protrusive and retrusive
movements, respectively, of the condyle disk complex and
which also function in the production of synovial fluid.
The nerve supply to the TMJ is predominantly from
branches of the auriculotemporal nerve with anterior
contributions from the masseteric nerve and the posterior
deep temporal nerve. Many of the nerves to the joint
appear to be vasomotor and vasosensory, and they may
have a role in the production of synovial fluid.
35. Musculature
All muscles attached to the mandible influence its
movement to some degree. Only the four large
muscles that attach to the ramus of the mandible are
considered the muscles of mastication; however, a
total of 12 muscles actually influence mandibular
motion, all of which are bilateral. Muscle pairs may
function together for symmetric movements or
unilaterally for asymmetric movement.
For example, contraction of both lateral pterygoid
muscles results in protrusion and depression of the
mandible without deviation, whereas contraction of
one of the lateral pterygoid muscles results in
protrusion and opening with deviation to the opposite
side.
36. 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.
37. Supramandibular Muscle Group
The temporalis muscle is a large fan-shaped muscle
taking its origin from the temporal fossa and lateral
aspect of the skull, including portions of the parietal,
temporal, frontal, and sphenoid bones. Its fibers pass
between the zygomatic arch and the skull and insert
on the mandible at the coronoid process and anterior
border of the ascending ramus down to the occlusal
surface of the mandible, posterior to the third molar
tooth.
Viewed coronally the temporalis muscle has a
bipennate character in that fibers arising from the
skull insert on the medial aspect of the coronoid
process, whereas fibers arising laterally from the
temporalis fascia insert on the lateral aspect of the
coronoid process.
39. In an anteroposterior dimension the temporalis
muscle consists of three portions: the anterior,
whose fibers are vertical; the middle, with oblique
fibers; and the posterior portion, with
semihorizontal fibers passing forward to bend
under the zygomatic arch.
The function of the temporalis muscle is to
elevate the mandible for closure. It is not a power
muscle. In addition contraction of the middle and
posterior portions of the temporalis muscle can
contribute to retrusive movements of the
mandible. To a small degree unilateral contraction
of the temporalis assists in deviation of the
mandible to the ipsilateral side.
40. The masseter muscle, a short rectangular muscle taking its
origin from the zygomatic arch and inserting on the lateral
surface of the mandible, is the most powerful elevator of
the 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, yet
have somewhat different functions. The superficial portion
originates from the lower border of the zygomatic bone and
the anterior two-thirds of the zygomatic arch and passes
inferiorly and posteriorly to insert on the angle of the
mandible.
The deep head originates from the inner surface of the
entire zygomatic arch and on the posterior one-third of the
arch from its lower border. The deep fibers pass vertically
to insert on the mandible on its lateral aspect above the
insertion of the superficial head.
41. The superficial portion in particular has a multipennate
appearance with alternating tendinous plates and fleshy
bundles of muscle fibers, which serve to increase the
power of the muscle.
Both the superficial and deep portions of the masseter
muscle are powerful elevators of the mandible, but they
function independently and reciprocally in other
movements.
Electromyographic studies show that the deep layer of the
masseter is always silent during protrusive movements
and always active during forced retrusion, whereas the
superficial portion is active during protrusion and silent
during retrusion.
Similarly the deep masseter is active in ipsilateral
movements but does not function in contralateral
movements, whereas the superficial masseter is active
during contralateral movements but not in ipsilateral
movements.
43. 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.
44. The lateral pterygoid muscle has two portions that can
be considered two functionally distinct muscles. The
larger inferior head originates from the lateral surface
of the lateral pterygoid plate. Its fibers pass superiorly
and outward to fuse with the fibers of the superior
head at the neck of the mandibular condyle, inserting
into the pterygoid fovea.
The superior head originates from the infratemporal
surface of the greater sphenoid wing, and its fibers
pass inferiorly, posteriorly, and outward to insert in the
superior aspect of the pterygoid fovea, the articular
capsule, and the articular disk at its medial aspect, as
well as to the medial pole of the condyle. Anatomic
studies have shown that the majority of the superior
head fibers insert into the condyle rather than the
disk.
45. The inferior and superior heads of the lateral
pterygoid muscle function independently and
reciprocally. The primary function of the inferior head
is protrusive and contralateral movement. When the
bilateral inferior heads function together, the condyle
is pulled forward down the articular eminence, with
the disk moving passively with the condylar head.
This forward movement of the condyle down the
inclined plane of the articular eminence also
contributes to opening of the oral cavity. When the
inferior head functions unilaterally the resulting medial
and protrusive movement of the condyle results in
contralateral motion of the mandible. The function of
the superior head of the lateral pterygoid muscle is
predominantly involved with closing movements of the
jaw and with retrusion and ipsilateral movement.
48. Inframandibular Muscle Group
The inframandibular muscles can be subdivided into two
groups: the suprahyoids and the infrahyoids. The
suprahyoid group consists of the digastric,
geniohyoid,mylohyoid, and stylohyoid muscles; lies
between the mandible and the hyoid bone; and serves to
either raise the hyoid bone, if the mandible is fixed in
position by the supramandibular group, or depress the
mandible, if the hyoid bone is fixed in position by the
infrahyoids.
The infrahyoid group, consisting of the sternohyoid,
omohyoid, sternothyroid, and thyrohyoid muscles, attaches
to the hyoid bone superiorly and to the sternum, clavicle,
and scapula inferiorly. This group of muscles can either
depress the hyoid bone or hold the hyoid bone in position,
relative to the trunk, during opening movements of the
mandible.
49. 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 mandibular
movement: the inferior and superior joints—bilaterally. Two types
of movement are possible: rotation and translation.
The inferior joints, consisting of the condyle and disk, are
responsible for rotation, a hinge-like motion. The center of
rotation is considered to be along a horizontal axis passing
through both condyles.
In theory pure hinge motion of approximately 2.5 cm measured
at the incisal edges of the anterior teeth is possible.
Nevertheless most mandibular movements are translatory as
well, involving a gliding motion between the disk and the
temporal fossa, which are the components of the superior joints.
The mandible and disk glide together as a unit because they are
held together by the collateral ligaments. The maximum forward
and lateral movement of the upper joint in translation is
approximately 1.5 cm.
50. 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.
51. 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).
52. 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.
53. 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.
54. 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 a
statement of the patient's reasons for seeking consultation
or treatment.
The history of the present illness should be
comprehensive, including an accurate description of the
patient's symptoms, chronology of the symptoms,
description of how the problem affects the patient and
information about any previous treatments (including the
patient's response to those treatments).
To have patients complete a general questionnaire is often
useful to help provide information about the history of their
problem. The use of a visual analog pain scale may also
help obtain an under· standing of the patient's perception
of the severity of their pain.
55. 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.
56. 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.
57. The TMJs are examined for tenderness and
noise. The location of the joint tenderness (e.g.,
lateral or posterior) should be noted. If the joint is
more painful during different areas of the opening
cycle or with different types of functions, this
should be recorded.
The most common forms of joint noise are
clicking (a distinct sound) and crepitus (i.e.,
scraping or grating sounds). Many joint sounds
can be easily heard without special
instrumentation or can be felt during palpation of
the joint; however, in some cases auscultation
with a stethoscope may allow less obvious joint
sounds, such as mild crepitus, to be appreciated.
58. Evaluation or temporomandibular
joint for tenderness and noise. Joint
is palpated laterally in closed
position (A) and open position (B).
59. The mandibular range of motion should be
determined. Normal range of movement of an adult's
mandible is about 45 mm vertically (i.e., interincisally)
and 10 mm protrusively and laterally.
The normal movement is straight and symmetric. In
some cases, tenderness in the joint or muscle areas
may prevent opening. The clinician should attempt to
ascertain not only the painless voluntary opening but
also the maximum opening that can be achieved with
gentle digital pressure.
In some cases the patient may appear to have a
mechanical obstruction in the joint causing limited
opening but with gentle pressure may actually be able
to achieve near normal opening. This may suggest
muscular rather than intracapsular problems.
60. 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.
61. The dental evaluation is also important. Odontogenic
sources of pain should be eliminated. The teeth
should be examined for wear facets, soreness, and
mobility, which may be evidence of bruxism.
Although the Significance of occlusal abnormalities is
controversial, the occlusal relationship should be
evaluated and documented. Missing teeth should be
noted, and dental and skeletal classification should be
determined.
The clinician should note any centric relation and
centric occlusion discrepancy or Significant posturing
by the patient. The examination findings can be
summarized on a TMD evaluation form and included
in the patient's chart. In many cases a more detailed
chart note may be necessary to document adequately
all of the history and examination findings described
previously.
62. Radiographic Evaluation
Radiographs of the TMJ are helpful in the
diagnosis of intraarticular, osseous, and soft
tissue pathologic conditions. The use of
radiographs in the evaluation of the patient with
TMD should be based on the patient's signs and
symptoms instead of routinely ordering a
standard set of radiographs. In many cases the
panoramic radiograph provides adequate
information as a screening radiograph in
evaluation of TMD. A variety of other radiographic
techniques are available that may provide useful
information in certain cases.
63. 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 on
the same film.
Because a panoramic technique provides a
tomographic-type view of the TMJ , this can frequently
provide a good assessment of the bony anatomy of
the articulating surfaces of the mandibular condyle
and glenoid fossa; and other areas, such as the
coronoid process, can also be visualized.
Many machines are equipped to provide special views
of the mandible, focusing primarily on the area of the
TMJs. These radiographs can often be complete in
the open and closed position.
64. Panoramic imaging. A, Normal anatomy or right
condyle. B, Imaging illustrates degenerative changes or
left condyle via remodeling.
65. 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.
66. Temporomandibular Joint
Arthrography
This imaging method was the first technique available
that allowed visualization (indirect) of the intra
articular disk. Arthrography involves the injection of
contrast material into the inferior or superior spaces of
a joint, after which the joint is radiographed.
Evaluation of the configuration of the dye in the joint
spaces allows evaluation of the position and
morphology of the articular disk.
This technique also demonstrates the presence of
perforations and adhesions of the disk or its
attachments. With the availability of more advanced,
less invasive techniques, arthrography is rarely used.
67. 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.
68. Computed Tomography
Computed tomography (CT) provides a combination
of tomographic views of the joint, combined with
computer enhancement of hard and soft tissue
images. This technique allows evaluation of a variety
of hard and soft tissue pathologic conditions in the
joint. CT images provide the most accurate
radiographic assessment of the bony components of
the joint.
CT scan reconstruction capabilities allow images
obtained in one plane of space to be reconstructed so
that the images can be evaluated from a different
view. Thus evaluation of the joint from a variety of
perspectives can be made from a single radiation
exposure.
69. 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.
70. 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.
71. 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.
72. Nuclear Imaging
Nuclear medicine studies involve intravenous injection
of technetium-99, a y-emitting isotope that is
concentrated 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 images
can then be used to determine active areas of bone
metabolism.
Although this technique is extremely sensitive, the
information obtained may be difficult to interpret.
Because bone changes, such as degeneration, may
appear identical to repair or regeneration, this
technique must be evaluated cautiously and in
combination with clinical findings.
73. Single-photon
emission computed
tomography (bone
scan). Area of
increased activity is
apparent in both
temporomandibular
joints.
74. Psychological Evaluation
Many patients with temporomandibular pain and
dysfunction of long-standing duration develop
manifestations of chronic pain syndrome behavior.
This complex may include gross exaggeration of
symptoms and clinical depression. The comorbidity of
psychiatric illness and temporomandibular dysfunction
can be as high as 10% to 20% of patients seeking
treatment
A third of these patients is suffering from depression
at the time on initial presentation, whereas more than
two thirds have had a severe depressive episode in
their history.
75. Psychiatric disorders may elicit somatic
components through parafunctional habits
resulting in dystonia and myalgia, and individuals
with chronic pain commonly have a higher
incidence of concomitant anxiety disorders.
Behavioral changes associated with pain and
dysfunction can be elicited in the history through
questions regarding functional limitation that
results from the patient's symptoms.
If the functional limitation appears to be excessive
compared with the patient's clinical signs or the
patient appears to be clinically depressed, further
psychological evaluation may be warranted.
