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TITLE:   TEMPOROMANDIBULAR JOINT DISORDERS
SOURCE:  Dept. of Otolaryngology, UTMB, Grand Rounds
DATE:    September 19, 1990
RESIDENT PHYSICIAN:      F. Brian Gibson, M.D.
FACULTY:                 Francis B. Quinn, Jr. , M.D.
DATABASE ADMINISTRATOR:  Melinda McCracken, M.S.
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"This material was prepared by resident physicians in partial fulfillment of 
educational requirements established for the Postgraduate Training Program of 
the UTMB Department of Otolaryngology/Head and Neck Surgery and was not 
intended for clinical use in its present form.  It was prepared for the purpose
of stimulating group discussion in a conference setting.  No warranties, either
express or implied, are made with respect to its accuracy, completeness, or 
timeliness.  The material does not necessarily reflect the current or past 
opinions of members of the UTMB faculty and should not be used for purposes of
diagnosis or treatment without consulting appropriate literature sources and 
informed professional opinion." 


I. INTRODUCTION

A. Definition - "TMJ Syndrome" is inappropriate catch-all termfor
a variety of disorders with symptoms related to temporomandibular
joint. Now prefer "TMJ Disorders" to reflect pathologic diversity of
problems leading patients to have complaints in this area. 

B. Incidence - approximately 25% of adults have some awareness
of masticatory symptoms but less than 10% have a condition
that warrants investigation. 

C. History

     1. TMJ problems first really publicized with description by
Costen (an otolaryngologist) in the 1930's of TMJ pain relieved by
a dental appliance. He attributed the pain to overclosure and
focused interest on role of occlusion in causing TMJ pain. This was
to dominate thought for many years. 

     2. 1940's - reconstructive dentistry used to treat TMJ and
bite-raising was major technique. Results were frustrating. 

     3. 1950's - Occlusal equilibration became popular. TMJ
tomography, arthrography were developed. Occlusion still dominated
thought about TMJ pain. 

     4. 1960's - Masticatory muscles were blamed for TMJ pain and
emotional stress/myofascial pain became buzzwords. 

     5. 1970's - Shift in focus to internal derangements of the TMJ
components. 

     6. 1980's - more eclectic approach emphasizing multifocal
etiology for many TMJ complaints. 

II. ANATOMY

A. Description - diarthroidal joint created by mandibular
condyle and its articulation with the glenoid fossa of temporal bone.


B. Components

     1. Mandible - condyle varies between 13-25 mm anteroposteriorly 
and 5.5-16 mm mediolaterally.  

     2. Disc - aka meniscus. Fibrous connective tissue divided into
four zones: bilaminar zone, posterior band, intermediate band and
anterior band. Disk has loose anterior and posterior attachments
allowing translation as joint opens and closes. Anterior
attachments blend into superior head of lateral pterygoid muscle.
The posterior attachment is bilaminar attaching to posterior margin
of glenoid and blending into capsule. It limits the sliding
component of joint movement. Medial and lateral attachments to
periosteum are more firm. The disk also separates joint into upper
(approximately 2 cc in volume) and lower joint compartments (l cc
in volume). 

     3. Cartilage - articular surfaces covered in layer of
fibrocartilage. This makes TMJ unique among synovial joints because
all others have hyaline cartilage. Fibrocartilage is excellent
shock absorber because of high content of elastic fibers. 

     4. Glenoid fossa - Bounded posteriorly by squamotympanic
fissure and anteriorly by convex articular eminence. Medially
bounded by suture between squamosa and greater wing of sphenoid.
Bone is quite thin and also lined with fibroelastic tissue. 

     5. Synovial membranes - cover all internal surfaces of joint
at birth but are lost from articulation points. In adulthood only
line inner surface of capsule. Highly vascular and composed of two
cell layers. Outer layer is fibrous and inner has secretory cells. 

     6. Joint capsule - funnel-shaped capsule runs from glenoid and
articular eminence to neck of condyle. Somewhat deficient
anteriorly. Lateral connective tissue thickening (temporomandibular
ligament) is actually part of capsule. 

     7. Ligaments - stylomandibular ligament is thickened band of
cervical fascia running from apex of styloid to posterior edge of
ramus. Sphenomandibular ligament is medial from spine of sphenoid
to lingula of mandibular foramen. Temporomandibular ligament is a
thickening of lateral portion of capsule which functions as a check
ligament to prevent dislocation. It limits downward and posterior
distraction of the joint. 

     8. Related muscles - at rest these maintain stability of TMJ.

     a. Elevators : 

     i. Temporalis - arises from temporal fossa and converges into
tendon which passes deep to zygomatic arch and inserts on medial
surface of coronoid. Primary function is elevation. More posterior
fibers retrude mandible and limit translation. 

     ii. Masseter - arises from zygoma and maxilla. Inserts on
ramus and angle of mandible. Elevates mandible. 

     iii. Medial pterygoid - arises from medial lip of lateral
pterygoid plate of sphenoid and inserts on medial angle of mandible
and ramus. Elevates and protrudes mandible. 

     b. Depressors : 

     i. Lateral pterygoid - arises in two heads, the larger from
lateral lip of pterygoid plate and the smaller from infratemporal
surface of greater wing of sphenoid. The superior head inserts onto
articular disc and capsule and functions to rotate and pull the
disc anteriorly into anterior disc space. The inferior head inserts
on the condylar neck and functions to open the joint, protrude the
mandible and pull it to the opposite side. 

     ii. Geniohyoid, mylohyoid and digastric - all function to
depress the mentum and open TMJ. 

     9. Nerve supply - Three types of mechanoreceptors are present
in TMJ. Also one type of nociceptor distributed in capsule but
nowhere else in joint. Probably not the source of TMJ pain. A dense
plexus of unmyelinated fibers collects impulses from these and
travel via auriculotemporal, masseteric and lateral pterygoid
nerves to trigeminal. 

     10. Blood supply - basically deep auricular branch of internal
maxillary artery. 

C. Function - Mouth opening requires coordinated movement
between condyle, muscles of mastication and the meniscus. 

     1. The TMJ is structured to deliver rotatory component with
disc-condyle complex and linear sliding component between the disc
and the glenoid/articular eminence (upper joint space). In normal
state, during jaw opening, the meniscus and condyle move anteriorly
around the articular eminence with the meniscus maintaining its
relative position to the condylar head. 

     2. As mouth opens muscles contract in following order: 
mylo/geniohyoid, digastric and inferior lateral pterygoid mm.
Sup. lateral pterygoid remains inactive. 

     3. As the mouth closes the meniscus and condyle move
posteriorly together due to the combined effects of the pterygoids,
muscles of mastication and the posterior attachment. 

     4. This return phase is initiated by the medial pterygoids
followed by masseters. Temporalis does not contract strongly in
unloaded state. The sup. lateral pterygoid contracts to stabilize
the condyle and, at the conclusion of closure, to draw the disc
anteriorly. 

III. ETIOLOGY AND PATHOPHYSIOLOGY

A. Articular Disturbances - most common are meniscal
derangements and degenerative arthritis.

     1. Disc Derangements - most common is anterior displacement of
meniscus. Occurs in several progressive forms and may become more
severe with time.

     a. In the first type, when mouth is closed the meniscus slips
anteriorly into space normally occupied by lateral pterygoid fat
pad. It sits partially off condyle in an angle formed by anterior
surface of condyle and posterior surface of articular eminence.
     b. Meniscus displacement with reduction - anteriorly displaced
meniscus slips over the condyle as the mouth opens usually with a
clicking or popping sound. During closure the disc slips back into
place also frequently producing a click. Clinical features can include
deviation of the mandible to the involved side.  N.B. not all patients
with joint noises have a meniscus problem.

     c. No reduction - in some patients the meniscus remains
displaced regardless of degree of translation achieved. May or may
not limit degree of jaw opening.

     d. Etiology - probably arises from repetitive overloading of
joint. This occurs in several forms:

     i. Static overloading - the stationary application of
excessive pressure causes deformation of disc with roughening and
eventual perforation. Also induces condylar and glenoid remodeling.

     ii. Impact overloading - results from occlusal disharmony and
beats up disc as teeth are clenched. Loss of disc contour and
self-centering capability. Eventually helps cause displacement.

     iii. Frictional overloading - exceeding lubricating ability of
synovial fluid causes roughening of disc and articular cartilage.

     2. Arthritides

     a. Degenerative - Tissues of joint react to functional demands
with trophic changes which include remodeling. Attempts to
harmonize morphology and function with forces acting on it. Step
from remodeling to degenerative change may be a subtle one.
Degenerative arthritis is a noninflammatory process accompanied by
damage to articular cartilage. Symptoms include pain in joint and
muscles, limitation of motion and crepitance. Thought to be end
point of a variety of derangements of the TMJ with repetitive
microtrauma and cartilage damage.

     b. Inflammatory

     i. Rheumatoid arthritis - Present in 1-3% of general
population. Male:Female ratio of 1:2.7. Autoimmune inflammatory
polyarthritis. Occasionally involves TMJ. Histopath. findings of
inflammatory changes in synovial membranes with granulomatous
change in later stages. Eventually progresses to ankylosis and
joint destruction.

     ii. Gout - metabolic disorder rarely involves TMJ. Joint
becomes red, swollen, quite tender. Responds well to certain
anti-inflammatory agents.

     iii. Ankylosing spondylitis - associated with HLA-B27 group.
More typically involves SI joint, vertebral column. 5-25% of
patients have TMJ symptoms. Most common of these is progressive
limitation of motion.

     iv. Psoriatic arthritis - Erosive polyarthritis more common in
men.

     v. Sarcoid arthritis - very uncommon. Most commonly seen as a
granulomatous polyarthritis late in course of disease.

     vi. Scleroderma - see resorption of ramus and condyle thought
to be secondary to pressure ischemia caused by tightening of soft
tissues as disease progresses.

     3. Inflammatory conditions - much less common now than
formerly. Infection reaches TMJ through penetrating wounds, direct
extension form contiguous structures and hematogenous spread.
Clinical signs include intense, localized pain, edema, erythema and
trismus. Systemic toxicity also common. Radiographically, see early
widening of joint space followed by narrowing caused by loss of
cartilage and meniscus. Ankylosis and scarring are late
complications. Etiologic agents include Staph and Strep (most
common) followed by GC, H. influenzae and granulomatous infections.
Treatment geared toward delivering high dose antibiotics and
surgical debridement as needed. Physical therapy is also very
important.

     4. Condylar Displacement - some patients present with acute or
chronic (recurrent) condylar dislocations. Comprise 5-10% of all
patients with TMJ disturbances.

     a.  Etiology - laxity of supporting tissues either from
previous trauma or a variety of predisposing factors contributes to
problem of recurrent dislocation. Hypermobility is term for a joint
which is capable of extended ROM because of lax ligaments, etc. NB
spontaneous dislocations are freq. bilateral while those from
trauma are more often unilateral.

     b. Diagnosis - pain, inability to close the mouth, tense
masticatory muscles, salivation, open bite. Tenderness in the joint
is more typical of fx while in temporal fossa suggests dislocation.

     c. Treatment - For acute dislocation reduction and rest are
suggested. Chronic dislocations can be treated in a variety of
ways. PT, sclerosis and correction of occlusal abnormalities are
non-surgical options. Surgical options include three major
categories:

     i. Limit translocation - anchoring procedures such as fascial
or alloplastic slings, blocking (suturing disc to eminence to block
translation) or myotomy (section of lateral pterygoid to reduce
anterior force on mandible).

     ii. Limit blocking factors to reduction - eminectomy or
discectomy.

     iii. Combination procedures - e.g. condylotomy or
condylectomy, myotomy with discectomy, etc.

     5. Ankylosis - to define terms: trismus is condition in which
muscle spasm or contracture prevents opening of mouth,
pseudoankylosis mimics true ankylosis and can be due to fractures,
fibrous scar within joint, etc., and ankylosis which is bony fusion
of the joint from condyle to glenoid fossa.

     a. Etiology - most frequently trauma. Early mobilization of
condylar fractures is essential to reduce risk of ankylosis. Other
causes include rheumatoid arthritis, neoplasia and infection.

     b. Diagnosis - based on clinical exam and plain films.

     c. Treatment - In children, joint is approached through
preauricular incision and condylectomy carried out. If meniscus is
gone then a Silastic or other replacement must be inserted. If a
lot of bone is excised, some of this may need to be replaced with
a bone graft. In adults a total arthroplasty is the preferred
procedure. If pseudo-ankylosis caused by coronoid interference is
present, this can be corrected by coronoidectomy.

     6. Fractures - condylar and related fractures comprise about
30% of mandibular fractures. Variety of clinical pictures from no
displacement to fracture dislocation of condyle out of glenoid
fossa. Complications include ankylosis, growth disturbances and
post-traumatic arthritis. Malocclusion remaining after fracture
heals may need to be treated via osteotomies and orthodontics. 

     7. Neoplasia - tumors of TMJ are very uncommon. These can
arise as primary tumors, from spread of adjacent sites or as
metastases. Primary benign tumors include osteomas, osteochondromas
and chondromas. Malignant tumors include: osteosarcomas,
chondrosarcomas, synovial fibrosarcomas, malignant fibrous
histiocytoma and ameloblastomas. Metastatic lesions are most
commonly carcinomas. Primary sites include: breast, lung, prostate,
colorectum, skin and pancreas.
 
     8. Developmental abnormalities - treatment requires
understanding of the morphologic defect, secondary distortion of
contiguous and contra-lateral facial structures and the effects of
early surgery on facial growth and body image. 

     a. Congenital Defects

     1. Hemifacial Microsomia - occurs in 1:5600 births and is
developmental defect of first and second branchial arches
(mechanism unknown). Second most common congenital facial defect
behind cleft lip/palate. Asymmetric mandibular and maxillary growth
is accompanied by maldevelopment of the overlying soft tissues. The
end-stage deformity consists of a short, medially displaced ramus
and TMJ. The chin deviates to the affected side and the occlusal
plane is tilted. Treatment aimed at reconstructing the ramus and
joint to allow normal function and development. 

     2. Bilateral microsomia - much less common. Treatment is
similar. 

     b. Acquired Growth Defects

     i. Condylar Hyperplasia - most common post-natal growth
abnormality of the TMJ. Results from abnormal proliferation of an
aberrant condylar growth center during the prepubertal growth
spurt. TMJ symptoms include noise in joint, limitation of motion,
inability to translate because of large condylar head. Two growth
patterns: vertical  (vertically long ramus, open bite on affected
side with no crossbite or chin deviation) or rotational (vertically
long ramus while chin deviates to normal side with crossbite on
normal side). Treatment with high condylectomy and orthodontics to
restore normal occlusion. 

     2. Ankylosis - can result from many causes. These include:
trauma, XRT, surgery in area, JRA and infection. See above. 

B. Non-Articular Disturbances

     1. Masticatory muscle abnormalities - may have associated
myalgias, acute malocclusion and restricted opening. 

     a. Protective muscle splinting - response to perceived injury
arises through central excitation. Pts. report functional myalgia
without malocclusion or restriction. 

     b. Elevator spasm - restricted opening and pain with closing.

     c. Lateral pterygoid spasm - acute malocclusion and pain with
clenching. 

     d. myositis - dysfunction secondary to immobilization,
soreness at rest and pain with all motion. 

     2. Occlusal abnormalities - Many patients have poor occlusion
without TMJ symptoms. Occlusal disharmony can be a predisposing
factor in the development of TMJ pain. When other "activating
factors" such as emotional stress with associated bruxism are
present then can develop TMJ dysfunction. Thought that potentially
damaging malocclusion causes problems as teeth are clenched in
mximal intercuspation. Force is transmitted to articular disc and
condyle with resultant trauma. 

     3. Bruxism - rhythmic or spasmodic grinding of teeth. Usually
occurs during REM sleep and is associated with high levels of
stress. May directly contribute to displacement of disc through
action of superior head of lateral pterygoid on disc. 

     4. Myofascial Pain Disorder or Syndrome - pain with or without
associated autonomic phenomena referred from active myofascial
trigger points with associated dysfunction. Pain derived from these
trigger points is referred to other structures. The involved muscle
may be otherwise normal. Mechanism of activation unclear but
emotional stress appears to be involved. Can produce secondary
internal joint derangements from altered muscular activity. 

5. Disorders of surrounding structures

C. Conditions Mimicking TMJ Disorders

     1. Trigeminal or Glossopharyngeal Neuralgia
     2. Atypical facial neuralgia 
     3. CNS lesions - certain brainstem lesions can present with
facial/TMJ pain 
     4. Odontogenic pain
     5. Neoplasms
     6. Otologic pain

IV. PATIENT EVALUATION

A. History - need to obtain the following:

a. Patient's description of problem. 
b. Location of symptoms (e.g. pain, restriction of movement,
headache, malocclusion). 
c. Length of time symptoms have been present. 
d. How often the symptoms occur. 
e. Preceding/predisposing events. 
f. Character of pain and any joint noises. 
g. Overall life stressors, history of migraines, bruxism, etc. 
h. Previous therapy. 

B. Physical Examination - careful physical exam with
particularattention to pain in masticatory muscles, clicks,
jaw sounds, other signs or symptoms of systemic problems.

V. RADIOGRAPHIC EVALUATION - attempts to define the nature ofintra-
or extra-articular abnormality which is producing dysfunction. 

A. Plain Films - On any given plain film only a portion of thejoint
can be seen. Another problem is the superimposition of surrounding
structures on the joint because of the TMJ'slocation at the base of
skull. Plain films remain useful screening tools. Lateral films are
obtained most freq., AP less commonly. Useful projections include
following: 

     1. Transcranial - one of two major lateral projections used.
Closed and open mouth views usually obtained. To minimize
superimposition a degree of vertical angulation freq. used. This
takes away the view of the cortical surface of the condyle. Central
and medial cortical erosions of the condyle may not be appreciated
on this view. 

     2. Transpharyngeal - Demonstrates condylar neck, head and
upper portion of ramus (shows ramus and neck better than
transcranial because contralat. petrous apex does not overlap).
Good for showing condylar head and neck fractures. 
     3. Trans-orbital - optimal AP view. At max. opening the
condylar head, upper ramus and medial and lateral poles of the
condyle are shown.
 
     4. Towne's projection - gives satisfactory view of both
condyles, particularly neck and ramus. Condylar surface and
eminence are freq. not seen well. 

     5. Interpretation - In most patients with TMJ symptoms some
degenerative changes will be seen. This suggests an internal
derangement. Erosions typically occur first on the posterolateral
condyle in those with meniscus displacement with reduction. As this
progresses anterior erosion suggests lack of reduction.
Obliteration of joint space suggests ankylosis. 
B. Tomography - divided into plain tomograms (gradually
being displaced by CT and MRI) and CT. Indicated for
further evaluation of abnormalities picked up on screening
plain films. CT good for assessing the osseous components of
the joint and the position and function of the disc. Main advantages
are that it allows simultaneous assessment of both bony and
soft-tissue components of the joint. 

C. Arthrography - very good for evaluating soft tissue
components especially disc position, function and shape. Performed
by injecting about 0.5cc of contrast into joint. 

D. MRI - Outstanding for evaluation of soft-tissue components. 

VI. NON-SURGICAL TREATMENT - management aimed at treating
the symptoms, underlying causes, predisposing factors andpathologic
effects. 

A. Reassurance - Common to all therapies for these
disorders.Patients frequently concerned that a serious condition
is present and need to have their anxiety allayed. This may inturn
lessen the severity of their symptoms. May also be agood idea to go
over the prognosis and need for fairly long course of therapy. 

B. Rest - After reassuring patient then need to palliate and allow
natural resolution of symptoms if possible. Counsel pt. to avoid
excessive jaw movements and hard foods. 

C. Analgesics and Muscle Relaxants - nonsteroidals are first line of
therapy. May also prescribe diazepam or otherbenzodiazepine as both
anti-anxiety and muscle-relaxing agent. Valium at night will
frequently decrease nocturnal bruxism. After 2-4 weeks can monitor
progress. 

D. Occlusal Splints - designed to "open" bite and
preventover closure . Most useful and best tolerated appears to be an
appliance (bite plane) which occludes with the anterior six
mandibular teeth. All the posterior teeth are discluded and the
appliance is retained with loops around the upper first molars. This
type of appliance is best used at night. If the patient needs one
during the day a total occlusal splint is frequently used.
Indications forusing a bite plane:

     a. Treating a click - raising the bite freq. abolishes clicks.

     b. Prevention of bruxing. 
     c. Relief of pain.

The bite plane appears to work by decreasing the load on the joint
and maintaining a normal meniscal-condylar relationship. 


E. Other Treatments

     1. Heat - local heat valuable to decrease pain and muscular
stiffness. Can use local diathermy or ultrasonics or Wal-Mart
heating pad. Sophisticated machines provide greater psychological
benefits. 

     2. Remedial exercises - help to promote more normal mandibular
movements.
 
     3. Psychotherapeutic approaches - helpful to reduce anxiety
and stress. Tricyclics or other agents may play a role in this
approach.

     4. Hypnotherapy - can help relieve nocturnal bruxing and
anxiety. 

     5. Dental therapy - need to treat caries, replace missing
teeth with appliances and can consider occlusal adjustment if
necessary. Best to avoid the last unless absolutely sure it's
indicated. 

VII. SURGICAL TREATMENT - decision to proceed with surgery based on
level of pain, source of symptoms, previous treatments, amenability
to surgical correction and occlusal stability. 

A. Intra-articular Corticosteroids - First TMJ injectionsreported
in 1953. Has been shown that repeated injections can cause permanent
articular changes including cartilage destruction. However, single
injections are effective in many patients and will permanently
relieve their symptoms.Technique: 

     1. Asepsis needed because entering joint. Local anesthesia
obtained by blocking auriculotemporal nerve. Pass needle behind
head of condyle to 1 cm deeper than bone and inject about 1 cc. If
inject near neck of condyle can anesthetize facial nerve. 

     2. Aqueous solution of corticosteroid injected through 21
gauge needle. Following tract to condylar head the needle is walked
up and backwards on condyle over the posterosuperior aspect . 5mm
deeper the needle will be in synovial cavity. .5 cc is injected. 

     3. The upper joint space can be entered by asking the patient
to open the jaw widely. The needle is directed upwards and
anteriorly towards the anterior part of the glenoid. The correct
depth is when bone is encountered and the needle is twice as deep
as the lower injection. Another 0.5 cc is injected. 

     4. The day after injection, the pt. will have fairly
significant pain and will require analgesics. 

B. Arthroscopy - first developed with advent of fiberoptics in 1960s. 
Extended to TMJ by Ohnishi in 1975 followed byMurakami et al. 

     1. Indications - Provides valuable information regarding
intra-articular pathology and can be used to supplement more
traditional examinations. Other indications include: trauma and
post-traumatic complaints, internal derangements, diseases
primarily affecting the synovial tissues, e.g. gout,
chondromatosis, pseudogout, RA, osteoarthrosis. 

     2. Equipment - includes cannulas, rod-lens telescopes (2.4mm)
and light sources as well as various operating forceps. 

     3. Technique - See Oral Surgery texts.

     4. Examination - look at posterior disc attachment for
integrity, synovial membranes for hyperemia or synovitis. Joint
surfaces should also be inspected. 

C. Meniscus Procedures

     1. Repair - if disc is just displaced but is not eroded or
torn it can be replaced into normal position and secured via
plication, etc. 

     2. Replacement - temporary replacement with Silastic or
Proplast discs for 2-3 months while remainder of joint heals is
advocated by some. 

D. Condylar Resection and Remodelling

     1. Condylotomy - used mainly in Europe. Success rate of 6070%
complete improvement and 10-15% partial. 

     2. Condylectomy - total excision has many complications
including shortening of ramus with premature occlusion and
deviation to ipsilateral side. Indications include ankylosis in
children or severe remodeling with pain.

     3. Condylar shave - get benefits of condylectomy without
complications. Should excise no more than 2-3 mm. 

     4. Arthroplasty - Reshaping to remove osteophytes, etc. 

E. Articular Replacement
     1. Eminence implants - frequently bony grafting used to
restore height of eminence when degenerative disease present. 

     2. Glenoid implants - variety of materials available.

     3. Meniscus replacements - see above.

     4. Condylar and total joint prostheses - considered for those
with loss of condyle secondary to degenerative disease or severe
ankylosis. Frequently also need to put implant in glenoid fossa to
prevent resorption. Implants are made of titanium, Proplast and
Proplast/Teflon. This is a procedure which still has many
complications. 


F. Complications

     1. Continued Pain - Anywhere from 10-50% depending on series.

     2. Infection - 5-6% infection rate quoted in literature. 

     3. Nerve Damage - Frontotemporal branch of VII is at highest
        risk. 

     4. Frey's syndrome - injury to auriculotemporal nerve. 

     5. Superficial Temporal Aneurysm -

     6. Hemorrhage - Uncommon. 

     7. Implant Failures - foreign body reaction is typical for all
alloplastic implants. Can eventually necessitate removal.  Metallic
prostheses can also loosen and induce bone resorption. 
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                          BIBLIOGRAPHY

1. Bell WE. Temporomandibular Disorders. Year Book. Chicago. 1990.

2. Keith DA. Surgery of the Temporomandibular Joint. Blackwell.
   Boston. 1985. 

3. Kraus SL. TMJ Disorders: Management of the Craniomandibular
   Complex. Churchill Livingstone. New York. 1988. 

4. Ogus HD. Common Disorders of the Temporomandibular Joint.
   Wright, Ltd. Bristol. 1986.
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