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16
Disorders of the Temporomandibular Joint
CHAPTER OUTLINE
Overview‚ 253
16.1 Anatomy and Examination‚ 253
16.2 Temporomandibular Joint Disorders
(TMDs)‚ 255
Overview
Articulation of the mandible with the cranial base occurs
at the temporomandibular joints (TMJs). In health, the
right and left TMJs do not act independently of one another, as the mandible is a single bone. The TMJ can be
affected by a range of disorders, including pain/dysfunction and internal displacement of the disc. It is also affected
by trauma and by systemic diseases such as rheumatoid
arthritis. It has been estimated that 1 in 3 people have
symptoms of TMJ disorders and that an even greater proportion exhibit signs.
16.1 Anatomy and Examination
LEARNING OBJECTIVES
You should:
• understand the anatomy of the joint.
• be familiar with clinical examination and radiological
assessment of the joint.
ANATOMY
The TMJs are the two joints between the mandible and the
temporal bones. They are unique in the body in that they
contain two joint spaces separated by a fibrocartilage disc
(Fig. 16.1).
COMPONENTS
The Mandibular Condyle
The mandibular condyle is the bony ellipsoid head of the
mandible attached to the ramus by an elongated neck. Its
mediolateral dimension (around 20 mm) is larger than the
antero-posterior dimension (8–10 mm). Its articulating
surface is covered in a thin layer of fibrocartilage. There is
usually a clearly demarcated ridge running mediolaterally
along its anterior surface, marking the edge of the articulating surface. Below the ridge is a depression, for insertion
of the lateral pterygoid muscle.
16.3 Other Conditions Affecting the
Joint‚ 257
Self-Assessment: Questions‚ 259
Self-Assessment: Answers‚ 261
The Mandibular (Glenoid) Fossa
The mandibular fossa is a depression on the inferior surface
of the squamous temporal bone. The fossa is bounded anteriorly by a ridge of bone, the articular eminence, which
forms the anterior margin of the joint. It is also covered in a
thin layer of fibrocartilage. The mastoid air cells often extend into the bone of the articular eminence and the bone
of the fossa.
Interarticular Disc (Meniscus)
The interarticular disc is a biconcave sheet of avascular
fibrous connective tissue that divides the joint into superior
and inferior joint spaces. At its anterior margin, it blends
with fibres of the lateral pterygoid muscle. The posterior attachment attaches to looser connective tissue (bilaminar
zone) containing nerves, blood vessels and elastic fibres.
Capsule
The TMJ has a fibrous capsule attached to the rim of the
mandibular fossa and the neck of the condyle. The disc attaches to it medially and laterally. It is lined with synovial
membrane, secreting synovial fluid. The lateral aspects of
the capsule are thickened to form the lateral (temporomandibular) ligament.
Ligaments
The lateral ligament lies lateral to the TMJ and runs from the
root of the zygoma to the posterior aspect of the condylar
neck. It limits antero-posterior joint movement. The sphenomandibular and stylomandibular ligaments are also part of
the joint complex and probably also serve to limit movement.
Joint Movement
The joint has a combination of rotatory movement of the
condyle in the lower joint space and anterior translation of
the condyle, with sliding of the disc forwards along the
articular eminence (Fig. 16.2).
EXAMINATION
Clinical Examination
The dental examination should be systematic and include
the TMJ and the masticatory muscles.
253
254
G
Rotation Translation
Master Dentistry
H
E
F
Fig. 16.1 The structure of the temporomandibular joint. (A) Upper
joint space; (B) lower joint space; (C) interarticular disc; (D) condylar
head; (E) lateral pterygoid muscle superior head; (F) lateral pterygoid
muscle inferior head; (G) mandibular fossa; (H) articular eminence;
(I) external auditory canal.
A
C
B
D
I
assessed by direct palpation. The lateral pterygoid is indirectly examined by noting the response (in terms of any
preauricular pain) to attempted opening against the restriction of the examiner’s hand below the chin. The medial
pterygoid cannot be examined.
Radiology
Most clinical problems related to the TMJ are caused by
muscular parafunction, myofascial pain (e.g., caused by
bruxism) or internal disc derangements. Neither is likely to
be associated with any relevant bony abnormalities. Consequently, radiography is not normally indicated unless there
is any suggestion of bony abnormality, such as might be the
case in rheumatoid arthritis or degenerative joint disease.
Many panoramic x-ray machines allow specific images of
the condyles to be taken without unnecessary radiography
of the rest of the jaws. The only radiographic projection to
show the whole joint is the transcranial oblique lateral
view. Occasionally, cone beam CT is useful to visualize the
bony structures in all three planes without superimposition. This is used as in diagnostic problem-solving, or in
monitoring developmental disorders or surgery.
A clinical diagnosis of suspected internal derangement
might lead to a requirement for imaging of the disc. This
requires soft tissue visualization and is done by magnetic
resonance (MR) imaging (Fig. 16.3). TMJ arthrography
(Fig. 16.4) is mainly of historical interest but may occasionally be used where patients are unsuitable for MR examination (e.g., because of severe claustrophobia).
Fig. 16.2 Movement of the temporomandibular joint.
Joint Examination
Movement
Face the patient and ask him/her to open slowly to maximum. Normal range (interincisal) is 35 to 40 mm. If opening is thought to be reduced, ask whether the limiting factor
is pain or an obstruction. Note the path of opening and any
lateral deviation.
Pain on Palpation
Palpate in front of the ear and within the external auditory
meatus.
Auscultation
This needs a stethoscope to be done properly. However,
clicks may well be audible without a stethoscope and/or apparent on palpation of the joint during movement. A click
implies a disc displacement that reduces into a normal position on opening. Crepitus (cracking/grating noise) implies
degenerative change or, sometimes, acute inflammation.
Arthroscopy
Arthroscopy allows visual examination of the upper joint
space and an opportunity for minor surgical treatment. A
small arthroscope can be used to facilitate lavage and division of joint adhesions. The lower joint space is difficult
to access without risk of damage to the articular disc.
Muscle Examination
Muscle tenderness suggests some abnormal function
(clenching, bruxism). Masseter and temporalis muscles are
Fig. 16.3 Magnetic resonance image of a TMJ. The disc can be seen as
the darker structure between the condylar head and the temporal bone.
Fig. 16.4 TMJ arthrogram. Contrast is injected into the joint spaces
below and, sometimes, above the disc. Consequently, the disc is outlined rather than directly seen.
Arthroscopy is undertaken under local anaesthesia; however, if lengthy arthroscopic surgery is to be undertaken,
then a conscious sedation technique would be appropriate
or even general anaesthesia.
16.2 Temporomandibular Joint Disorders (TMDs)
LEARNING OBJECTIVES
You should:
• understand the nature of TMDs.
• have a systematic approach to clinical history and
examination.
• know about the management options for patients with
TMDs.
16 • Disorders of the Temporomandibular Joint
255
WHAT ARE TMDS?
TMDs can be defined as a combination of symptoms and
clinical signs involving the TMJs and associated muscles.
Pain can arise from the muscles (myalgia, including myofascial pain) and/or joints (arthralgia); this pain may be
accompanied by intra-articular disorders (e.g., internal derangement, degenerative changes). Psychosocial factors
should be considered and their role explored.
Clinical Features
Symptoms are a combination of:
n
headache (usually temporal)
n
limitation/deviation on jaw opening
n
joint sounds
n
pain from the TMJ confirmed on palpation
n
pain from the associated muscles confirmed on palpation.
Radiology
Unless degenerative change is present there is no abnormality
visible.
Management
n
Reassurance and explanation to patients emphasizing the
benefits of self-management and home physiotherapy.
n
Jaw rest and soft diet.
n
Analgesics/anti-inflammatory drugs.
n
Occlusal splints to interfere with parafunction may offer
some help.
n
Physiotherapy.
n
Muscle relaxants.
Internal Derangement
The articular disc normally resides above the anterior aspect of the condylar head, with the disc posterior attachment lying within 10 degrees of the vertical (Fig. 16.5). A
disc may be anterior to this ‘normal’ position in asymptomatic individuals, suggesting that an anterior disc position is
a normal variant. Thus, an internal derangement is best
thought of as an abnormality in position that interferes
with function and that may be associated with other symptoms. An anterior disc ‘displacement’ is the most common
Closed Open
A
Fig. 16.5 The normal articular disc in the closed and open positions (A) and in an arthrogram showing the maximum opening (B).
B
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Master Dentistry
internal derangement, but antero-medial, medial, and
antero-lateral displacements are all seen.
DISC DISPLACEMENT WITH REDUCTION
Reduction means that a displaced disc ‘reduces’ into a normal position on opening but reverts to an abnormal position
on closing (reciprocal click; Fig. 16.6A).
Clinical Features
n
Clicking on opening.
n
Clicking on closing.
n
Transient jaw deviation during opening/closing.
Radiology
No abnormalities are apparent on plain radiographs. Disc
imaging shows the displaced disc in a closed/rest position
(Fig. 16.6B).
Management
n
Consider no treatment other than reassurance and
explanation.
n
Occlusal splints to interfere with parafunction may offer
some help.
n
Physiotherapy.
It should be emphasised that treatment should only be
considered where the abnormality is affecting the patient’s quality of life; a clicking joint may be considered
as normal.
DISC DISPLACEMENT WITHOUT REDUCTION
If there is no reduction, a displaced disc remains in a displaced
position regardless of the stage of opening. This interferes
with movement and may cause pain (Fig. 16.7A).
Clinical Features
n
Reduction in opening.
n
In unilateral cases, lasting deviation on opening.
n
No click.
n
Pain may be present in front of the ear.
Radiology
Plain films usually show nothing. In long-standing
cases there may be signs of degenerative joint disease
(see later).
Disc imaging shows an abnormal disc position in closed
and open positions (Fig. 16.7B). In long-standing cases,
perforation of the disc may be seen and joint space adhesions inferred.
Closed Open
B
A
Fig. 16.6 A displaced disc with reduction showing the movement diagrammatically and on MRI in open and closed positions.
Open (post-‘click’)
B
Closed OpenA
Fig. 16.7 A displaced disc without reduction showing the movement diagrammatically (A) and on MRI (B).
Management
n
Explanation of the condition and reassurance.
n
Muscle relaxants and physiotherapy.
n
Manipulation under anaesthetic.
n
TMJ surgery.
SURGICAL TREATMENT OF INTERNAL DERANGEMENT
Surgery is only indicated where non-surgical methods have
failed and symptoms are severe. Meniscoplasty is a procedure to reposition the disc. Access to the joint is gained via
a vertical incision in front of the ear (preauricular incision)
most commonly, although some favour an incision behind
or within the ear. Various techniques have been devised to
avoid damage to the facial nerve. The capsule is then
opened, the disc visualised, repositioned and sutured in
place. Studies suggest various success rates such as 90% of
patients show improvement in symptoms, 5% no better and
5% worse.
The disc may be removed (menisectomy) if it cannot be
repositioned because of deformity or degeneration. It may
have been replaced with an alloplastic material in the past
but is more likely to be replaced now with an autogenous
tissue such as temporalis muscle or auricular cartilage.
16 • Disorders of the Temporomandibular Joint
Fig. 16.8 Radiograph of degenerative joint disease showing marginal
bony proliferation (“lipping”).
257
16.3 Other Conditions Affecting the Joint
LEARNING OBJECTIVES
You should:
• know the effects of trauma on the joint.
• know what systemic diseases will also affect the TMJ.
DEGENERATIVE JOINT DISEASE
Degenerative joint disease is a non-inflammatory disorder
of joints in which there is joint deterioration with bony
proliferation. The deterioration leads to loss of articular
cartilage and bone erosions. The proliferation manifests as
new bone formation at the joint periphery and subchondrally. It has an unknown aetiology, but previous trauma,
parafunction and internal derangements are all suggested
as aetiological factors.
Clinical Features
n
Pain localised to the TMJ region.
n
Limitation of opening, worse with prolonged function.
n
Crepitus.
n
Tenderness on palpation of TMJ.
Radiology
Plain films show erosions of the articular surfaces of the
condyle and less commonly of the mandibular fossa. Sclerosis of the bone and marginal bony proliferation (“lipping”
or osteophytes) are seen (Fig. 16.8) and narrowing of the
radiographic joint space. Bony proliferations may break
away and be seen as loose bodies in the joint space.
Management
n
Explanation and reassurance.
n
Anti-inflammatory drugs.
n
Physiotherapy.
n
Restore deficiencies in the posterior occlusion to reduce
loading on TMJs.
n
Intra-articular steroid injections (advanced disease). Intraarticular injections of hyaluronic acid have also been
found to be beneficial for some patients.
n
Surgery (advanced disease; final option) to smooth irregular
condylar head where there are osteophytes or irregularities.
RHEUMATOID ARTHRITIS
Rheumatoid arthritis is a disorder associated with synovial
membrane inflammation in several joints. The TMJs are involved in approximately half of affected individuals. Villous
synovitis leads to the formation of synovial granulomatous
tissue (pannus) that involves fibrocartilage and the underlying bone. The pannus releases enzymes that cause cartilage/
bone destruction.
Clinical Features
n
Pain over TMJs.
n
Tenderness over TMJs.
n
Swelling over TMJs.
n
Stiffness and limitation of opening.
n
Crepitus.
n
Developing anterior open bite and retrusion of chin in
advanced disease.
n
Joints of hands, wrists, knees and feet commonly involved.
Radiology
Radiology demonstrates reduction in bone density in the TMJ.
There is marked erosion of the condylar head and articular
fossa and narrowing of the joint space.
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Master Dentistry
In long-standing disease, there is:
n
destruction of the entire condyle
n
anterior open bite
n
secondary degenerative joint disease
n
ankylosis.
Management
n
Analgesics/anti-inflammatory drugs.
n
Steroids.
n
Physiotherapy.
JUVENILE IDIOPATHIC ARTHRITIS (JUVENILE CHRONIC ARTHRITIS)
Juvenile idiopathic arthritis differs from rheumatoid arthritis in the age of onset (mean age 5 years), the severe systemic involvement and the absence (in some cases) of
rheumatoid factor.
While it shares clinical and radiological features with
rheumatoid arthritis, the age of onset means that there is
often a severe effect on mandibular growth, leading to a
“bird face” appearance owing to the mandibular retrusion,
often accompanied by an anterior open bite. The disease
often has periods of remission/quiescence, during which
time the erosions of the joint may “smooth over” with formation of a new cortex. Ankylosis may occur.
precluding examination or cervical lymphadenopathy. If a
patient with a TMD fails to respond after interventions in the
expected way, then the possibility of an underlying malignancy should be considered.
RARE DISORDERS OF THE TMJ
A number of very uncommon conditions may affect the
TMJ and these are so rare that they may easily go unrecognised in a busy TMD service (Table 16.1).
TRAUMA
Trauma may have a number of effects upon the TMJ. Fractures
are discussed in Chapter 8.
Effusion
Effusion is influx of fluid into the joint, usually either bleeding
following trauma or inflammatory exudate. It is important to
differentiate this from septic (infective) arthritis.
Clinical Features
n
Pain over joint.
n
Swelling over joint.
n
Limitation of movement.
n
Sensation of a blocked ear.
n
Difficulty in occluding posterior teeth.
MALIGNANCY MIMICKING A TMD
Careful history taking and examination with follow up are
important, particularly if trismus is present, or if symptoms
and progress are atypical. Malignancy can mimic TMD when
present in the infra-temporal fossa where the pterygoid plates
There is a widened joint space.
Management
n
Anti-inflammatory drugs.
n
Rarely, surgical drainage may be needed.
and muscles may be affected. Squamous cell carcinoma can
Radiology
arise in the maxillary antrum without other signs or symptoms until it erodes through the posterior bony wall to invade
the infra-temporal fossa. Adenoid cystic carcinoma and salivary duct carcinoma frequently exhibit perineural invasion
and may also cause TMD-like features. Metastasis to the infratemporal fossa, primary sino-nasal cancers and central nervous system (CNS) disorders are also rare mimics. Recurrent
epistaxis, anosomia, nasal discharge, hearing loss and cranial
nerve dysfunction are concerning features. Particular care
should be taken if the patient has a history of previous
head and neck cancer, a preauricular mass, complete trismus
Table 16.1 Rare Disorders of the TMJ
Disorder Features
Ganglion cyst or bursa Preauricular swelling of the TMJ capsule due to degeneration and distension by synovial fluid.
Crystal arthropathy Gout is quite common and can lead to deposition of needle-shaped urate crystals in the TMJ. The joint
becomes painful and acutely inflamed.
Synovial chondromatosis Multiple cartilaginous or osteo-cartilaginous nodules form around the synovial lining causing stiffness.
Tenosynovial giant cell tumour A benign disorder of tendon sheath that rarely leads to destruction of the condyle and adjacent soft tissue.
Condylar hyperplasia Unilateral or bilateral progressive enlargement of the condyle in the 1st to 3rd decades. Overgrowth leads to
facial asymmetry and occlusal derangement (Fig. 16.9A & B).
Primary neoplasms Benign tumours such as chondromyxoid fibroma, osteocartilaginous exostosis and primary malignancy such as
osteosarcoma and chondrosarcoma can occur but are very uncommon.
DISLOCATION
In dislocation of the TMJ, the condyle is abnormally positioned outside the mandibular fossa but within the joint
capsule. Dislocation may occur during trauma or be caused
by failure of muscular coordination.
Clinical Features
n
Inability to close the jaw.
n
Pain.
n
Muscle spasm.
16 • Disorders of the Temporomandibular Joint
A B
Fig. 16.9 Coronal (A) and surface rendered (B) CBCT images of a 21-year-old female with left-sided condylar hyperplasia. The condyle is L-shaped, with
normal bony architecture, enlarged body, midline shift to the right and unilateral posterior open bite.
259
joint replacement with a prosthetic joint unless the patient’s
facial development is not yet complete, when a costochondral
(rib) graft is used in an attempt to provide a bony replacement
that may grow.
Fig. 16.10 Manual manipulation to reduce a dislocated jaw.
Radiology
Radiography confirms a clinical diagnosis. The condyle
may translate beyond the articular eminence normally,
without a dislocation, so clinical information is essential.
The condyle will be anterior and superior to the “summit”
of the articular eminence.
Management
Manual manipulation to reduce the dislocation (Fig. 16.10).
Intravenous sedation with midazolam provides muscle relaxation and greatly facilitates this manoeuvre. The patient
should avoid wide mouth opening for some days and use the
hand to prevent this when yawning.
ANKYLOSIS
Fusion across a TMJ may occur as a result of trauma, mastoid
infection or juvenile chronic arthritis. Surgical treatment is by
Self-Assessment Questions
TRUE/FALSE
1. The following contribute to mouth opening:
a. Medial pterygoid muscle
b. Lateral pterygoid muscle
c. Masseter muscle
d. Temporalis muscle
e. Stylomandibular ligament
2. The following radiographs/imaging methods can be
used to measure joint space width:
a. Panoramic radiograph
b. Transpharyngeal radiograph
c. Transcranial oblique lateral radiograph
d. Transorbital (Zimmer) radiograph
e. Computed tomography (CT)
3. Condylar hyperplasia:
a. Is a developmental disorder
b. Is an inflammatory disorder
c. Is assessed using radioisotope imaging
d. Is usually self-limiting
e. Causes ankylosis
4. Erosion of the condyle may occur in:
a. Pain/dysfunction
b. Internal derangement
c. Psoriasis
d. Synovial chondromatosis (SC)
e. Dislocation
5. Deviation to the left side on opening could be caused by:
a. Right TMJ disc anterior displacement without
reduction
b. Left TMJ disc anterior displacement without reduction
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Master Dentistry
c. Right TMJ effusion
d. Left TMJ effusion
e. Bony ankylosis
6. The following may be associated with inflammatory
arthritides of the TMJ:
a. Osteopaenia
b. Prognathia
c. Atlanto-axial subluxation
d. Osteophytes
e. Unilateral disease alone
Single Best Questions
1. A 25-year-old male has just had a blow to the face playing rugby. He complains of pain over his right TMJ and
limitation of jaw movement. On examination there is no
gross facial asymmetry. There is a tender swelling over
the affected joint and the ipsilateral posterior teeth do
not seem to occlude completely. Which of the following
is your preferred working diagnosis?
a. Internal derangement: anterior displacement with
reduction
b. Joint dislocation
c. Fracture of condylar neck
d. Joint effusion
e. Internal derangement: anterior displacement without
reduction
2. Which of the following would best describe joint
sounds associated with anterior displacement without
reduction?
a. like the “rustling of a crisp bag”
b. single click on opening
c. reciprocal clicks on opening and closing
d. previous history of joint clicking
e. grating sounds
3. A 28-year-old woman presented for a check-up. The
dentist noticed that the occlusal plane was depressed on
the left side. The molar teeth did not make contact with
the maxillary teeth on that side, though wear facets
were present. Choose one of the following as your working diagnosis.
a. Acromegaly
b. Osteochondroma of left condyle
c. Left condylar hyperplasia
d. Right condylar hyperplasia
e. Left condylar hypoplasia
4. Once a clinical diagnosis of ankylosis has been made,
cone beam CT may be useful in distinguishing between
fibrous and bony ankyloses. Which of the following conditions may result in fibrous ankylosis?
a. Internal derangement
b. Juvenile idiopathic arthritis
c. Septic arthritis
d. Degenerative joint disease
e. Trauma to the developing condyle
5. Which of the following modalities is your first choice for
imaging myofascial pain?
a. Magnetic resonance imaging
b. Cone beam CT
c. Panoramic radiography
d. Computed tomography
e. No imaging.
6. Select the most appropriate imaging for a fracture of the
condylar neck
a. Panoramic radiograph (collimate to TMJ regions)
b. Occipitomental view at 30 degrees
c. Cone beam CT
d. Reverse Townes radiograph
e. Reverse Townes and Panoramic radiographs
Case History Questions
CASE HISTORY 1
Amanda is a 22-year-old dental receptionist who complains of sharp pain in the right preauricular region that
increases when trying to move her jaw, with an associated
headache. This has been present for 3 months. There are
no joint noises when she opens her mouth and there is
very limited opening. There is a deviation of the jaw to the
right that occurs only in the final stages of opening. She
says that she used to have a clicking jaw but no longer
does so.
1. What diagnosis is suggested?
2. What would be the management?
CASE HISTORY 2
Mrs Johnson is a 50-year-old woman who attends the surgery complaining of a chronic localised pain over her left TMJ
and limited opening. The masticatory muscles are not particularly tender. She finds opening her mouth wide for dental
treatment painful. She says that the pain gets worse as the
day goes on. You notice crepitus on examining the TMJ.
1. What diagnosis is suggested?
2. What would be the management?
CASE HISTORY 3
David is a 19-year-old man who was struck on the left side
of his chin during a game of Saturday football. He arrives at
the surgery on Monday morning in pain from the right TMJ.
He cannot open his mouth as wide as he could. His right
TMJ/preauricular region is very tender and swollen, and he
deviates towards the right side on opening.
1. What diagnosis is suggested?
2. What would be the management?
CASE HISTORY 4
Mr Jones is a busy bank manager and your regular patient.
At a check-up, he mentions that he has pain when opening
his mouth, associated with intermittent clicking from the
left TMJ. There is pain when you palpate the muscles of
mastication and when you palpate the left preauricular region. There is a slight reduction in mouth opening and the
jaw deviates towards the left side on opening.
1. What diagnosis is suggested?
2. What would be the management?
16 • Disorders of the Temporomandibular Joint
261
Viva Questions
1. Is a clicking temporomandibular joint (TMJ) abnormal?
2. What clinical signs would suggest that a patient was a
bruxist?
3. Are TMJ disorders a manifestation of mental health
problems?
4. Should you take a panoramic radiograph for patients
with TMJ disorders?
5. What are the indications and contraindications for TMJ
arthrography?
6. How would you examine the lateral pterygoid muscle
when assessing a patient with a TMJ disorder?
7. What are the uses of arthroscopy in managing TMJ
disorders?
8. When might you use a soft bite guard for a patient with
TMJ problems?
Self-Assessment Answers
TRUE / FALSE
1. a. False. It helps in closing the mouth.
b. True. Only the lateral pterygoid muscle is a “mouth
opener”. In fact, it has two parts; its lower head is active
in opening, protrusion and lateral movements, while
its upper head has activity during mouth closing.
c. False. It helps in closing the mouth.
d. False. It helps in closing the mouth.
e. False. The stylomandibular ligament extends from
the styloid process on the skull base to the angle of
the mandible; its role is probably to limit movement
of the mandible, but it has no active role to play.
2. a. False. Panoramic radiographs are taken with the jaw
protruded and, therefore, cannot show any information about joint space width.
b. False. The transpharyngeal radiograph is taken with
the mouth open.
c. True. A “closed” transcranial oblique lateral radio-
graph is the only radiograph that shows joint space
width. However, the angulation used means that it is
the joint space width in the lateral part of the joint
that is demonstrated.
d. False. This rarely used antero-posterior radiograph is
taken with the mouth open. The x-ray source has to
be positioned close to the eye and consequently gives
a high dose to the lens.
e. True. CT can give measurements of joint space width.
However, conventional axial scans must be reassembled in a two-dimensional reconstruction to make
measurement easier, so fine sections are best. Direct
sagittal scanning is preferable.
Joint space narrowing is a sign of degenerative joint
disease. However, it is important to remember that
imaging should not be carried out just to ensure that
all pathological findings have been demonstrated.
The purpose of imaging is to aid in diagnosis and to
make a contribution to management. If you have established the diagnosis clinically and know what
treatment you are going to do, then the presence/
absence of joint space narrowing is irrelevant!
3. a. True. Condylar hyperplasia is a developmental anomaly causing excessive growth of the condyle, leading
to a developing facial asymmetry, enlargement of the
condyle and sometimes deformity of the condylar
head. It usually arises before age 20 years and is more
common in males.
b. False.
c. True. Radioisotope bone scanning (using 99 mTc-
labelled methylene bisphosphonate as the radiopharmaceutical) is used to assess activity in the
condyle; ideally surgery is carried out when the
activity is reduced to background level.
d. True. The jaw on the affected side often shows an in-
crease in height of the ramus and body. There may be
a posterior open bite on the affected side but often
there is compensatory maxillary alveolar overgrowth. Treatment is ideally by orthognathic surgery, but this should be delayed until the condition
has stopped developing.
e. False. Ankylosis is not associated with the condition.
4. a. False. Erosion of the condylar head is a fairly nonspecific feature. It is most commonly seen in degenerative joint disease.
b. True. Erosion in internal derangements represents
advanced disease with progression to degenerative
joint disease.
c. True. Psoriasis is a seronegative systemic arthritis.
Radiologically and clinically it is similar to rheumatoid arthritis.
d. True. SC is a rare disorder where there is formation
of multiple cartilagenous and osseocartilagenous
nodules in the synovial membrane of joints. These
nodules can detach and become loose in the joint
spaces. Patients with SC have variable symptoms
ranging from none to pain, swelling, joint noises
and trismus. Treatment is by surgery to remove
the nodules and resect the abnormal synovial
membrane.
e. False. There is no association with erosions.
5. a. False. Deviation occurs towards the affected side.
b. True. Any limitation on TMJ movement will lead to
deviation of the jaw towards the affected side.
c. False. This would cause deviation to the right.
d. True. Effusion will limit movement, causing deviation
to the left.
e. False. Bony ankylosis would not show this sign because
true ankylosis will prevent all but a tiny degree of jaw
movement.
6. a. True. Periarticular bone loss is a feature probably caused
by stimulation of osteoclasts by cytokines released from
the pannus.
b. False. Retrognathia and anterior open bite may
result.
c. True. Atlanto-axial subluxation can occur with
rheumatoid arthritis and is a risk that dentists must
bear in mind when manipulating patients in the dental chair
d. True. Degenerative joint disease follows primary inflam-
matory joint disease
e. False. These are systemic disorders affecting all synovial
joints, albeit at different rates and times
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Master Dentistry
Single Best Answers
1. d. Trauma has precipitated this problem, so the differential diagnosis is essentially between B, C and
D. In this case the occlusion is a helpful clue. If
there was a unilateral fracture of the condylar
neck, then there would probably be a posterior
open bite on the contralateral side. Dislocation is
usually bilateral and gives an anterior open bite.
Effusion, apart from other local signs of inflammation, tends to produce difficulty in bringing the
posterior teeth together, but no dramatic change in
the occlusion. Of course, if there is any doubt, radiography should be used as to exclude B and C.
Ultrasound and MRI can demonstrate joint effusion, but this is rarely necessary.
2. d. Patients with a reducing disc (disc displacement with
reduction) sometimes present with a sudden event of
inability to open their mouth (disc displacement
without reduction). The event usually arises suddenly, during eating, yawning or on waking from
sleep. Reciprocal clicking is the essential sign of anterior disc displacement with reduction. In the absence
of other symptoms, such as pain, difficulty in eating
etc., this can be seen as normal variation rather than
disease. Crepitus can be detected on palpation or
heard with a stethoscope and sounds like the “rustling a bag of crisps”. This and grating sounds indicate degenerative joint change, or sometimes acute
inflammation.
3. c. The dental features suggest that the ascending ramus
of the jaw on the left side continued growing after the
right side ceased. This is typical of condylar hyperplasia. As the occlusal plane becomes depressed the corresponding maxillary teeth overerupt. A would result
in bilateral hyperplasia and an anterior open bite, and
the patient is not in the correct age group for this
condition. D and E would result in right sided posterior open bite. Osteochondroma is a possibility, but
will be excluded by radiography.
4. b. Septic arthritis and trauma to the developing condyle
tend to result in bony ankylosis, whilst juvenile
chronic arthritis results in fibrous ankylosis. Bony
ankylosis means that mandibular movement is essentially nonexistent, although a few millimetres of
movement may be observed through flexing of the
bone. Sometimes, however, the ankylosis is due to fibrous union of the joint components, and a little
greater movement may be possible. Management is
however, the same for both.
5. e. As there is nothing to image in this condition, and as
the provisional diagnosis is reached on clinical evidence, no imaging is required.
6. e. When evaluating fractures, it is de rigueur to have two
images at different angulations, and this pair offers a
90 degree difference. It is becoming increasingly
common for CT to be used in this situation; while this
provides excellent images of the TMJ, it does this at a
higher radiation dose than E, and the relative cost/
benefit has not been evaluated.
Case History Answers
CASE HISTORY 1
1. The previous history of clicking suggests that there was,
in the past, a displaced disc in the right TMJ that could
reduce when opening. The change in symptoms, with
loss of the click and limitation of opening with late deviation, is typical of a nonreducing disc displacement. A
displaced disc without reduction is usually preceded by a
reducing disc.
2. Describe the problem to Amanda and try to reassure her.
Provide advice with respect to self-management and
home physiotherapy. Treatment should be carried out in
conjunction with her doctor, unless you are a hospital
practitioner. A referral for physiotherapy would be appropriate and a muscle relaxant drug could be prescribed. Benzodiazepine drugs are used for their muscle
relaxant effects. The form may be diazepam 5 mg at
night, or temazepam elixir (10 mg in 5 mL) at night.
Caution must always be exercised with respect to the use
of benzodiazepines. The lowest dose for the shortest time
should be prescribed. Review the patient after 1 month.
Longer review might be useful, particularly if there has
been some improvement, as spontaneous resolution can
occur. In the absence of any improvement, it may be appropriate to consider disc imaging and manipulation of
the jaw under general anaesthesia.
CASE HISTORY 2
1. The symptoms and signs suggest that the diagnosis is
degenerative joint disease.
2. First, take a radiograph of the affected TMJ to confirm
the diagnosis by identification of the radiological signs of
the disease. A panoramic (TMJ programme) radiograph
would be reasonable. Mrs Johnson is concerned about
the effect this condition is having on her life. Therefore, it
is worth attempting treatment. Reassure the patient and
describe the nature of the condition. Examine the mouth
and assess whether there is a satisfactory posterior occlusion. Prescribe a non-steroidal antiinflammatory drug.
An appropriate prescription would be 400 mg ibuprofen
three times a day after food for 1 month. Some patients
find topical NSAIDs to be useful, but at present there is
insufficient evidence to support their use. This should not
be prescribed for patients with any history of peptic ulceration or asthma, during pregnancy or for patients
with kidney or liver disorders. A course of physiotherapy
would be valuable. Review after 1 month. In the absence
of improvement, refer to a specialist clinic. The specialist
may consider intra-articular steroid injection or, as a last
resort, surgery.
CASE HISTORY 3
1. There is a clear link to the traumatic incident and the
differential diagnosis is a joint effusion or a fracture of
the right condylar neck.
2. Check the occlusion. An effusion would either have no effect on the occlusion or cause a difficulty in approximating