The temporomandibular joint (TMJ) connects the mandible to the temporal bone. It is a compound joint composed of bone and soft tissue structures. The TMJ develops from condylar and temporal blastemas and its structures allow for both hinging and gliding movements. Clinically, the TMJ is examined through inspection, palpation, auscultation and assessment of range of motion. Abnormal findings may include swelling, crepitus, limited movement or clicking sounds.
3. CONTENTS
• INTRODUCTION
• DEFINITION
• TYPE OF THE JOINT
• DEVELOPMENT OF THE JOINT
• BASIC ANATOMY OF THE JOINT
• MANDIBULAR MOVEMENTS
• CLINICAL EXAMINATION OF THE JOINT
• INVESTIGATIONS
• PROSTHODONTIC CONSIDERATIONS
4. TERMINOLOGIES:
• STOMATOGNATHIC SYSTEM: The combination of structures involved
in the speech, receiving food, mastication and deglutition as well as
the parafunctional actions.
-GPT 9
5. • Gnathology is a branch of dental care that
studies the work and interaction of
temporo-mandibular joint (jaw joint),
masticatory muscles and teeth, which
ensure proper performance of lower jaw.
GNATHOLOGY (TERM
COINED BY DR.HARVEY
STALLARD
Gnathos (GREEK) –
referring to JAW
Ology- meaning to
study
THE GNATHOLOGICAL APPROACH versus THE NEUROMUSCULAR APPROACH to Dental Diagnosis and Treatment
by Clayton A. Chan, D.D.S.
7. • DEFINITION:
“The articulation of the condylar process of the mandible and intra-
articular disc with the mandibular fossa of squamous portion of the
temporal bone; a diarthrodial, sliding hinge joint. Movement in the
upper joint compartment is mostly transitional, whereas that in the
lower joint compartment is mostly rotational. The joint connects the
mandibular condyle to the articular fossa of the temporal bone with the
temporomandibular disc interposed.”
-GPT 9
8. • TEMPOROMANDIBULAR JOINT IS ALSO
TERMED AS
1) Cranio-Mandibular Joint
2) Ginglymo-arthrodial joint
3) Modified ball and socket joint
4) Compound Joint
Okeson, JP: Management of temporomandibular disorders and occlusion. 6th edition
9. • The area where the mandible articulates with the cranium, the TMJ, is
one of the most complex joints in the body.
Provides for HINGING MOVEMENT in one plane
– GINGLYMOID JOINT
Also provides for GLIDING MOVEMENT –
ARTHRODIAL JOINT
Thus, considered as a GINGLYMOARTHRODIAL
JOINT
10. • TMJ is classified as a COMPOUND JOINT
COMPOUND
JOINT
MANDIBULAR
CONDYLE
ARTICULAR
DISC
MANDIBULAR
FOSSA
2 sets of Bone
12. DEVELOPMENT OF TEMPOROMANDIBULAR JOINT
TMJ structures originates
from 2 blastemas
CONDYLAR BLASTEMA
-Arises from the secondary
condylar cartilage of
mandible.
-Evolves to contribute to
the formation of: condylar
cartilage, aponeurosis of
lateral pterygoid muscle,
articular disc and the
capsular elements of the
joint.
TEMPORAL BLASTEMA
-arises from the otic
capsule.
-it develops into the
articular structures of the
upper level.
Shivlal Rawlani : manual of Temporomandibular Joint, 1st edition
13. INTRAUTERINE DEVELOPMENT OF TMJ
• 8th week – condylar blastema as a condensation of mesenchymal
cells.
-Temporal blastema is present posterior and lateral to the condyle.
• 10 – 12 weeks – growth in size of the condylar cartilage in
posterior and lateral direction to developing condyle.
Between the condylar and temporal blastema , third layer
of condensation of cells – develops into the articular disc.
• 12th week – when the two structures meet, cavitation
occurs to form : upper and lower joint spaces.
• 14 weeks – basic morphology of joint is achieved.
David A. -DEVELOPMENT OF THE HUMAN TEMPOROMANDIBULAR JOINT, British Journal of Oral Surgery, 1982.
14. BIRTH:
- Joint displays structural components
of adult joint, but it lies parallel to
occlusal plane instead of several mm
superior to it.
- Articular eminence – inferiorly
positioned, fossa - relatively flat and
joint functions as a pure hinge system
with no translation.
CHILDHOOD
- As primary dentition achieves
occlusion at about age of 3 years –
pressure placed on the joint,
results in change to non vascularity
of the articular surfaces.
16. MANDIBULAR CONDYLE
• Forms the inferior articular surface of
the joint.
• The condyle is the portion of mandible
that articulates with the cranium, around
which the movement occurs.
• Consists of medial & lateral projections
called as poles.
• Mediolateral Length- 18 to 23mm
Anteroposterior width- 8 to 10mm.
• Articulating surface – anterior and
posterior surface of most superior aspect
of condyle.
A – MANDIBULAR CONDYLE
B – MEDIAL AND LATERAL POLE OF THE CONDYLE
C – ANTERIOR ARTICULAR SURFACE OF CONDYLE
D - POSTERIOR ARTICULAR SURFACE OF CONDYLE
Okeson, JP: Management of temporomandibular disorders and occlusion. 6th edition
17. GLENOID FOSSA
• Forms the Superior articulating surface of the joint.
• Part of squamous part of temporal bone that houses
the mandibular condyle.
• Shape- concave
• Limited by :
Anteriorly – articular eminence
Posteriorly – squamotympanic fissure
Roof – covered by thin layer of compact bone (thus
cannot sustain heavy forces.)
18. ARTICULAR EMINENCE OR
ARTICULAR TUBERCLE
• Convex bony prominence present immediately
anterior to the mandibular fossa.
• Degree of convexity of articular eminence is highly
variable.
• Consists of – thick dense bone subjected to
loading during function.
• Steepness of the surface of articular eminence
dictates the pathway of the condyle when the
mandible is positioned anteriorly.
20. ARTICULAR DISC
• Composed of DENSE FIBROUS CONNECTIVE TISSUE and is positioned between
the two articulating bones i.e., the glenoid fossa and the mandibular condyle.
• Non vascularized and non innervated except
in the peripheral non - pressure bearing areas.
• Disc divides the joint space into 2 compartments
SUPERIOR JOINT
CAVITY
-Bordered by the glenoid
fossa and superior surface of
the disc.
-Allows translational
movement
INFERIOR JOINT
CAVITY
-Bordered by the mandibular
condyle and the inferior
surface of the disc.
-Allows rotational
movement.
21. ARTICULAR DISC DIVISION IN
SAGITTAL PLANE : ACCORDING
TO THICKNESS OF THE REGION
ANTERIOR
BORDER
Thicker than the
intermediate
zone.
INTERMEDIATE
ZONE
-Thinnest portion of
the disc.
-In normal joint,
articular surface of
the mandibular
condyle is located in
this zone.
POSTERIOR
BORDER
Even thicker
than the
anterior border.
22. ARTICULAR DISC IS ATTACHED POSTERIORLY TO-
Retrodiscal tissue OR Posterior
Attachment
-Region of loose connective tissue that is highly
vascularized and innervated.
bordered by superior retrodiscal lamina
-Lamina of loose connective tissue containing
ELASTIC FIBRES.
-Lamina attaches the articular disc to the tympanic
plate.
bordered by inferior retrodiscal lamina
-lamina chiefly composed of COLLAGENOUS FIBRES.
-Lamina attaches inferior border of posterior edge of the
disc to posterior margin of articular surface of condyle
RT – retrodiscal tissue
SRL – superior retrodiscal lamina
IRL – inferior retrodiscal lamina
23. FUNCTIONS OF ARTICULAR DISC
1. Shock absorption.
2. Prevents undue forward gliding.
3. A ball bearing action.
4. Allows a combination of different movement by dividing the joint
into compartments and allows bony elements to move
independently on the disc.
5. Assists in lubrication of the joint.
24. SYNOVIAL FLUID
-Clear, straw colored, viscous fluid, composed of dialy-sate of blood
plasma in combination with mucopolysaccharide – hyaluronic acid.
-Produced by the specialized endothelial cell lining that form
synovial lining in the joint cavities along with the specialized
synovial fringe.
It fills both the joint cavities that is superior (1.2ml) and inferior
(0.9ml) cavities. Hence, TMJ is referred to as a SYNOVIAL JOINT.
Serves 2 purposes:
1. Acts as a medium for providing metabolic requirements to the
articular tissues.
2. Serves as a lubricant between the articular surfaces during
function.
25. Synovial fluid lubricates articular surfaces by 2
mechanisms:
BOUNDARY LUBRICATION
• Primary mechanism of joint lubrication.
• Lubricates the articular tissues by surface contact.
• When synovial fluid becomes too viscid , its lubricating qualities are impaired –
i.e., clinically termed as GELATION.
WEEPING LUBRICATION
• Refers to ability of the articular surfaces to absorb small amount of synovial
fluid.
• Under compressive forces – small amount synovial fluid released that acts as a
lubricant between articular tissues.
• Helps eliminate friction in compressed but not moving joint.
Bell, W.E: Temporomandibular disorders, classification, diagnosis & management. 3rd edition
26. LIGAMENTS OF TMJ
FUNCTIONAL LIGAMENTS:
COLLATERAL (DISCAL)
LIGAMENT – MEDIAL
AND LATERAL
CAPSULAR LIGAMENT
TEMPOROMANDIBULAR
LIGAMENT
ACCESORY LIGAMENTS:
• SPHENOMANDIBUL
AR LIGAMENT
• STYLOMANDIBULA
R LIGAMENT
as
27. COLLATERAL (DISCAL) LIGAMENTS
• Attach the MEDIAL and LATERAL borders of the
articular disc to the poles of the mandibular condyle.
• Two discal ligaments- medial and lateral.
• MEDIAL discal ligament- attaches medial edge of disc to
medial pole of condyle.
• LATERAL discal ligament- attaches lateral edge of disc to
lateral pole of condyle.
• Function: Restrict movement of the disc away from the
condyle.
• They are responsible for the HINGING MOVEMENT. MDL – MEDIAL DISCAL LIGAMENT
LDL – LATERAL DISCAL LIGAMENT
Okeson, JP: Management of temporomandibular disorders and occlusion. 6th edition.
28. CAPSULAR LIGAMENT
• Capsular Ligament surrounds and
encompasses the entire TMJ.
• Acts to resist any medial, lateral or
inferior forces that tends to separate or
dislocate the articular surfaces.
• Encompass the joint, thus retaining the
synovial fluid.
29. TEMPOROMANDIBULAR LIGAMENT
CONSISTS OF 2 PARTS:
OUTER OBLIQUE PORTION:
• Resists excessive dropping of the condyle, therefore
limiting the extent of mouth opening.
• During initial phase of opening, the condyle can
rotate around a fixed point until the TM ligament
becomes tight.
• When ligament is taut, neck of condyle cannot
rotate further. If the mouth is to be opened wider,
the condyle would need to move downward and
forward across the articular eminence.
OUTER OBLIQUE
TM LIGAMENT
30. EFFECT OF OUTER
OBLIQUE PORTION
OF TM LIGAMENT
• This can be demonstrated by closing the mouth and applying mild posterior force to the
chin.
• The jaw will easily rotate to open until the teeth are 20 to 25 mm apart. When opened
wider than this, resistance is felt. At this point resistance will be felt when jaw is opened
wider.
• If jaw opened wider than this, rotation of the condyle at a fixed point to a movement
forward and down the articular eminence is seen.
31. INNER HORIZONTAL PORTION
• Limits posterior movement of the condyle and
disc.
• when force applied to the mandible, displaces
the condyle posteriorly.
• Therefore the ligament protects the retrodiscal
tissues from trauma created by the posterior
displacement of the condyle.
• It also protects lateral pterygoid muscle from
overlengthening and extension.
INNER HORIZONTAL
TM LIGAMENT
32. ACCESSORY
LIGAMENTS
SPHENOMANDIBULAR
LIGAMENT
• Arises from spine of
sphenoid bone and
extends downward and
inserts over LINGULA.
STYLOMANDIBULAR
LIGAMENT
• Arises from the styloid
process and extends
downward and forward to
the angle and posterior
border of mandibular
ramus.
• Limits excessive protrusion
of mandible.
33. PINTO LIGAMENT:
• The mandibular-malleolar ligament
found connecting the neck and
anterior process of the malleus to
the medio-postero-superior part of
the capsule, interarticular disc and
sphenomandibular ligament.
• Starching of the Pinto Ligament
causes ringing in the ears
(TINNITUS).
DML, Discomalleolar ligament
fibers; PML, fibers from sphenomandibular
ligament; PMAL, fibers from the discomalleolar
and sphenomandibular ligament.
T. Rowicki1 , A study of the discomalleolar ligament in the adult human, Folia Morphol., 2006
35. • TWO JOINT SYSTEMS IN ONE JOINT:
1. CONDYLE DISC COMPLEX – ROTATIONAL / HINGING MOVEMENT
2. CONDYLE DISC COMPLEX functioning against the mandibular fossa –
TRANSLATORY MOVEMENTS
3. ROTATIONAL / HINGING MOVEMENT –
initial mouth opening from 20 to 25mm
4. TRANSLATORY MOVEMENTS –
After 20 to 25 mm when the mouth is opened further.
Okeson, JP: Management of temporomandibular disorders and occlusion. 6th edition.
44. 1. INSPECTION
• Presence of any local swelling or erythema in preauricular region.
• Any gross asymmetry or hypertrophy of muscles.
• Any deformation, deviation of chin and tooth wear.
45. 2. PALPATION
• On palpation – if severe
effusion present, bulge is
palpated.
• Note the abnormal sound and
crepitus and the
anteroposterior gliding
movements of the condyle.
46. 3. AUSCULTATION
• Examined using stethoscope.
1. Joint sounds of single event for a
short duration – as CLICK,
• If loud – generally referred as POP.
• Clicking most commonly associated
with Internal Disc Derangement.
2. Crepitus- rough gravel like sound.
• The character of the sound and
timing of its occurrence should be
noted – as this may explain
presence of various conditions like
osteoarthritis, condyle- disk
incoordination, etc.
47. 4. RANGE OF MOTION
• ROM assessment is a simple and objective method to evaluate the
function of masticatory system.
• Degree of mandibular opening measured using – distance between
the incisal edges of upper and lower anterior teeth.
• Normal jaw opening – 40 to 60mm (directly related to the height)
• Opening if < 35mm in an adult – considered abnormal.
48. 5. PALPATION OF MUSCLES OF MASTICATION
MASSETER
MUSCLE
Only superficial
part can be
examined
extraorally.
Patient is asked to
clench his teeth.
MEDIAL
PTERYGOID
MUSCLE
Only inferior part
of the muscle can
be palpated by this
method.
TEMPORALIS
MUSCLE
Palpation is done
while clenching of
teeth.
50. PANORAMIC RADIOGRAPHY
-Method for observing acute bone deformation
and presence of cysts or tumours.
-The superimposition of the base of the skull and
zygomatic arch restricted the evaluation of the
condyle and glenoid fossa in the panoramic film.
TRANSCRANIAL RADIOGRAPHY
-provides relationship between head of
the condyle and glenoid fossa
-Used to examine the joint for fracture
with marked dislocation, gross arthritic
changes.
Pramod Kumar : Recent advances in Temporomandibular joint imaging – an update . Journal of Dental Sciences and Oral Rehabiltation- dec2013
51. COMPUTED TOMOGRAPHY
• For diagnosis of disc
displacement, condylar fracture,
degenerative bone changes,
ankylosis.
• Less convenient than MRI.
CONE BEAM COMPUTED
TOMOGRAPHY (CBCT)
• It is also known as volumetric CT.
• For examination of osseous
components of the TMJ.
• Has high diagnostic quality, less
radiation exposure than CT.
52. MAGNETIC REASONANCE IMAGING
• Non invasive technique, imaging of soft
tissue better than CT, less invasive than
arthrography.
• Used for imaging articular disc
displacement helpful to indicate any
fibrosis, joint effusion, neoplasm etc.
• Contraindicated in pregnant women,
patients with cardiac pacemakers,
claustrophobic patients.
54. A] CONGENITAL AND DEVELOPMENTAL TMJ ANOMALIES
Condylar aplasia or hypoplasia
• Failure of the condyle to develop
• May occur unilaterally or bilaterally
• Shift of the mandible towards affected side
• Alters occlusion and mastication
• In bilateral cases, the shift is not evident
Condylar hyperplasia
• Gradual enlargement of the mandibular condyle,
• progressive unilateral enlargement of the mandible,
• facial asymmetry and shifting of the midline of the chin to the
unaffected side, with resulting cross-bite malocclusion.
Keiseki Kaneyama: Congenital deformities and developmental abnormalities of the mandibular condyle in the temporomandibular joint , Congenital Anomalies
55. B] JOINT DISORDERS
a) Disc displacement with reduction:
Treatment : 1. if recent and painless, sometimes possible to
reduce the dislocated by manipulation.
2. If painful, a modified occlusal bite plane can be used to
reduce displacement.
b) Disc Displacement without reduction:
Treatment: 1. Patient education and self care
2. Pharmacotherapy
3. Occlusal therapy
William 6. Farrar, Differentiation of temporomandibular joint dysfunction to simplify treatment, J. Prosthet. Dent. December, 1972
57. REFERENCES:
• THE GNATHOLOGICAL APPROACH versus THE NEUROMUSCULAR APPROACH to Dental Diagnosis and
Treatment by Clayton A. Chan, D.D.S.
• Okeson, JP: Management of temporomandibular disorders and occlusion. 6th edition
• Shivlal Rawlani : manual of Temporomandibular Joint, 1st edition
• David A. -DEVELOPMENT OF THE HUMAN TEMPOROMANDIBULAR JOINT, British Journal of Oral
Surgery, 1982.
• Bell, W.E: Temporomandibular disorders, classification, diagnosis & management. 3rd edition
• T. Rowicki1 , A study of the discomalleolar ligament in the adult human, Folia Morphol., 2006
• Pramod Kumar : Recent advances in Temporomandibular joint imaging – an update . Journal of
Dental Sciences and Oral Rehabiltation- dec2013
• Keiseki Kaneyama: Congenital deformities and developmental abnormalities of the mandibular condyle in
the temporomandibular joint , Congenital Anomalies 2008
• William 6. Farrar, Differentiation of temporomandibular joint dysfunction to simplify treatment, J. Prosthet.
Dent. December, 1972
58. NOTHING IS MORE FUNDAMENTAL TO TREATING
PATIENTS THAN KNOWING THE ANATOMY.
-Jeffrey P. Okeson
THANK YOU
Editor's Notes
Performing these various functions are the teeth, jaws, the masticatory muscles, tongue, lips, surrounding soft tissues, and the nerves controlling these structures.
Adequate functioning of temporo-mandibular joint (TMJ) enables all the components of dental system to maintain flawless body operation.
If one component malfunctions then the entire system is affected.
Diarthrodial- junction or union of two bones. Allowing movement of the joint in various planes.
The TMJ is unique in that, even though the joint is synovial, the articulating surfaces of the bones are covered not by hyaline cartilage but by fibrocartilage. Fibrocartilage has greater proportion of dense collagen fibers that serves as a shock absorber . Has better ability to repair than the hyaline cartilage.
As the mandible is connected to the cranium through this joint.
Anatomically it is ball and socket type of joint allowing movements in all three planes - Sagittal Transverse Coronal
TMJ is made up of 2 bones - mandibular fossa of squamous part of temporal bone and the mandibular condyle which are interposed by a disc i.e., lubricated by synvial fluid and it is a joint that shows gliding as well as rotatory movements
Condylar blastema situated at the distal end of the developing mandible.
They are situated at a relatively larger distance from one another and grow towards each other.
The 1st evidence of the development of TMJ is seen at 8 weeks after conception.
The next 2 weeks the cells proliferate and differentiate in condylar cartilage.
The vascularisation and innervation of the joint occurs after 4th month of fetal life.
Birth 3) throughout the fetal life, fibrous articular surfaces are vascularised and innervated. This will disappear as function induces compression of the disc b/w condyle and temporal bone.
Childhood 2) afall or trauma to the joint before 3 yrs of age will often result in a heamarthrosis and possible fibrous ankylosis.
Medial pole generally is more prominent than the lateral.
Posterior articulating surface is greater than the anterior.
It is not called as a meniscus.
Anterior zone is 2mm thick and posterior is 2.7 mm thick and intermediate is 1mm thick.
Retrodiscal tissue is attached to a venous plexus that fill with blood as the condyle and disc translate while jaw opens and fills the space of mandibular fossa. This is known as the vascular knee.
Anteriorly disc is attached to capsular ligament connecting it superiorly with the articular surface of temporal bone and inferiorly with the articular surface of condyle.
Disc is also anteriorly attached to superior lateral pterygoid muscle fibres.
Free and rapid exchange exists between the capsule, synovium and articular tissues.
Boundary lubrication-and is means of replenishing the synovial fluid that has entered into the weeping lubrication.
This is mechanism by which metabolic exchange occurs.
Conditions altering the composition and consistency of synovial fluid may influence this normal lubrication system. Ex. Synovitis ( effusion within synovial sac.)
1. ligaments do not actively enter into the joint function but instead act as passive restraining devices to limit and restrict border movements.
1. The attachments of discal ligaments permit disc to be rotated anteriorly or posteriorly on articular surface of condyle.
2.They are innervated and have vascular supply and strain on these produces pain.
The fibres are attached superiorly to temporal bone along the borders of articular surfaces of mandibular fossa and articular eminence.
Inferiorly fibres attach to the neck of the condyle.
Provide proprioceptive feedback regarding position and movement of joint.
Lateral aspect of capsular ligament is reinforced by strong tight fibres that make up lateral or tm LIGAMENT
Outer portion extends from the outer surface of the articular tubercle and the zygomatic process posteroinferiorly to the condylar neck.
This unique feature of tm ligament which limits its rotational opening is seen only in humans .
With this force applied, patient should be asked to open the mouth.
The inner horizontal portion extends from the outer surface of the articular tubercle and the zygomatic process posteriorly and horizontally to the lateral pole of the condyle and posterior part of articular disc.
, this portion of the ligament becomes tight and prevents condyle from moving into the posterior region mandibular fossa
The effectiveness of this muscle is seen during trauma cases of mandible. In which the neck of the condyle will be seen to fracture before the retrodiscal tissues are severed or the condyle enters the middle cranial fossa.
Stylomandibular becomes taut when mandible is protruded.
The oto-mandibular ligaments are the discomalleolar ligament (DML), which arises from the malleus (one of the ossicles of the middle ear) and runs to the medial retrodiscal tissue of the TMJ, and the anterior malleolar ligament (AML), which arises from the malleus and connects with the lingula of the mandible via the sphenomandibular ligament. A positive correlation has been found between tinnitus and ipsilateral TMJ disorder. It has been proposed that a TMJ disorder may stretch the DML and AML, thereby affecting middle ear structure equilibrium.
Branch of – ECA
Branch of – 3rd branch of 1st part(retromandibular part) of maxillary artery
Branch of- ECA
Innervated by same nerve that provides both motor and sensory innervation to the muscles that control it i.e., the trigeminal nerve.
Branches of mandibular nerve provides afferent innervation.
All are branches of v3.
1)Boder ovements are defined as the mandibular movements a t the limits dictated by the anatomic structures, as viewed in a given plane.
frontal plane border movement : Left lateral superior border ,Left lateral opening border, Right lateral superior border, Right lateral opening border.
Border movements produced in this plane produce a characteristic ‘Shield tracing’. Here the patient is instructed to move his mandible from centric occlusion to canine guided disocclusion on the right side and then to the maximum right lateral position then arc downwards to the maximum mouth opening position . From this position, the patient is instructed to arc upward to the maximum left lateral position, return medially to canine guided disocclusion on the left side and then return to centric occlusion .
2) Horizontal plane border movement Left lateral border Continued left lateral border with protrusion Right lateral border Continued right lateral border with protrusion.
Border movements recorded in the horizontal plane produced a characteristic “Diamond tracing’. While recording the tracing, the patient is instructed to move mandible from the centric relation position. To the maximum right lateral position to the maximum protrusive position, to the maximum left lateral position and return to centric. GOTHIC ARECH TRACER in which record mandibular movement in the horizontal plane.
3) Sagittal plane border movement. Posterior open border ,Anterior open border, Superior contact border. Functional movements.
A characteristic ‘Beak tracing’ is formed while recording border movements in the sagittal plane.
posterior opening border:- determined by ligament and morphology of TMJ
anterior opening border:- SAME
superior contact border :- determined occlusal and incisal surface of the tooth.
Functional:- determined by neuromuscular system.
4) Envelop of motion : Given by POSSELT (1952)
Combination of mandibular border movements in the three planes. Represents the maximum range of movement of the mandible.
When we combine the border movements of all the three planes, we get a three dimensional space with which mandibular movement is possible. This three dimensional limiting space is called the envelope of motion. The envelope of motion is longest and widest superiorly and narrows down to a point near the maximum mouth opening position. Hence, as the jaw separation increases, space for movement decreases to a zero at the maximum mouth opening position.
The choice of imaging technique will depend on the specific clinical problem, whether hard or soft tissues will be imaged, radiation dose, cost, availability of the imaging technique, and the amount of diagnostic information provided by the technique.
Usually the hard tissues are imaged first to evaluate osseous contours, positional relationship of the condyle and glenoid fossa, and range of motion. Soft tissue imaging is indicated when information about disk position or morphology is needed or to image abnormalities in the surrounding muscles or soft tissues.
Panoromic - It is also indicated when the patienthas reduced mouth opening and the differential diagnosis offracture is considered. It can reveal advanced bone alter-ations in the condyle, such as asymmetries, erosions, osteophytes, fractures, changes in size and shape, degenerative and inflammatory processes, growth alterations, maxillary tumors, metastases, and ankylosis.
CT - Displaced and dislocated condylar fracture on a reconstructed CT scan (b) Coronal section CT showing antero-medially displaced and dislocated condylar neck fracture and telescoping of the ramus superiorly due to pterygomasseteric pull.
Hard tissues, teeth, and bones are well demonstrated and measured in their real morphological condition, with minimal noise and artifacts.However, few details are provided on soft tissue and it is not possible to evaluate the joint disc.
CBCT- uses a cone beam instead of collimated fan shaped beam used with spiral CT.
MRI - If used in patients with pacemakers the magnetic field might cause pacemaker to become dysfunctional or dislodge metallic objects leading to undesirable bleeding.
Other techniques – radionuclide imaging, arthroscopy, ultrasonography .
Treatment of condylar aplasia : osteoplasty in severe case and orthodontic correction of malocclusion.
Treatment of condylar hyperplasia : unilateral condylectomy
DDWR - Clicking, popping and/or snapping noise detected during both opening and closing, with palpation during at least one of three repetitions of jaw opening and closing. In the maximum intercuspal position, the posterior band of the disc is located anterior to the 11:30 position and the intermediate zone of the disc is anterior to the condylar head and On full opening, the intermediate zone of the disc is located between the condylar head and the articular eminence.
DDwoR - On full opening, the intermediate zone of the disc is located anterior to the condylar head. Maximum assisted opening of <40 mm is determined clinically
Complains of difficulty in mastication, pain on the affected side TMJ and masseter muscle region and trismus , deviation of mandible to affected side. Limited mouth opening and limited lateral movement to unaffected side. Intraorally, midline shift seen. 1st a stabilization splint was given and then after 1 month repositioning splint given.