An understanding of TMJ anatomy is important for proper diagnosis and treatment planning of Tmj disdorders.

1. Applied Anatomy and Mandibular Movements
TEMPOROMANDIBULAR
JOINT
Dr. Abhidha Tripathi
MDS First Year

2. CONTENTS
1. Introduction
2. Definition
3. Components
4. Histology
5. Vascular Supply
6. Innervations
7. Biomechanics
8. Movements
9. Conclusion
10. References

3. INTRODUCTION
• The TMJ is a giglymoarthrodial joint, a term that is derived from
ginglymus, meaning a hinge joint, allowing motion only backward
and forward in one plane and arthrodial, meaning a joint of which
permits a gliding motion of the surfaces.

4. DEFINITION
• The articulation of the condylar process of the mandible and the intra-
articular disc with the mandibular fossa of the squamous portion of the
temporal bone; a diarthrodial, sliding hinge (ginglymus) joint; movement in
the upper joint compartment is mostly translational, 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 joint articular disc interposed. (GPT9)

5. • The right and left TMJ form a bicondylar articulation and ellipsoid
variety of the synovial joints.
• Common features of the synovial joints exhibited by this joint
include a disk, bone, fibrous capsule, fluid, synovial membrane
and ligaments.

6. • The TMJ is classified as a compound joint. By definition, a
compound joint requires the presence of at least three bones, yet
the TMJ is made up of only two bones.
• Functionally, the articular disc serves as a nonossified bone that
permits the complex movements of the joint.

7. • Functionally-
• Composed of 4 articulating
surfaces:
Articular facets of Temporal bone
Mandibular condyle
Superior surface of articular disc
Inferior surface of articular disc

8. Articular Disc – divides the joint into
2 compartments
1. Lower compartment - permits
hinge motion and rotation
(ginglymoid)
2. Superior compartment – permists
sliding/translatory motion
(arthrodial)

9. ANATOMIC COMPONENTS
• Skeletal Components
• Dentition and their supportive structures
• Temporomandibular Joints
• Histology of Articular Surfaces
• Ligaments
• Muscular components

10. DENTITION AND SUPPORTIVE
STRUCTURES
• The 32 permanent teeth are distributed equally in the alveolar bone of the maxillary and
mandibular arches.
• The maxillary arch is slightly larger than the mandibular arch, which usually causes the
maxillary teeth to overlap the mandibular teeth both vertically and horizontally when in
occlusion.
• This size discrepancy results primarily from the fact that
1. The maxillary anterior teeth are much wider than the mandibular teeth, which creates a
greater arch width.
2. The maxillary anterior teeth have a greater facial angulation than the mandibular anterior
teeth, which creates a horizontal and vertical overlapping

11. SKELETAL COMPONENTS
• The three major skeletal
components that make up the
masticatory system are the
1. Maxilla
2. Mandible (which support the teeth)
3. Temporal bone (which supports the
mandible at its articulation with the
cranium)

12. THE MAXILLA
• Developmentally, two maxillary bones are fused together at the mid palatal suture.
• Superiorly, border of Maxilla forms the floor of the nasal cavity.
• Inferiorly, Maxillary bones forms the palate and the alveolar ridges.
• Maxillary teeth are considered to be a fixed part of the skull and hence make the stationary
component of the maxillary system.

13. THE MANDIBLE
• The mandible is a U-shaped bone that supports the lower teeth.
• It has no bony attachments to the skull and is suspended below the maxilla
by muscles, ligaments and other soft tissues.
• The condyle is the portion of the mandible that articulates with the cranium,
around which movement occurs.
• From the anterior view, it has a medial and a lateral projection called poles.

14. THE MANDIBLE
• The medial pole is generally more prominent than
the lateral.
• The posterior articulating surface is greater than
the anterior surface.

15. THE TEMPORAL BONE
• The mandibular condyle articulates at
the base of the cranium with the
squamous portion of the temporal
bone.
• This portion is called the Glenoid
fossa.
• Immediately anterior to the fossa is a
convex bony prominence called the
articular eminence.

16. TEMPOROMANDIBULAR JOINT
• The area where the mandible articulates with the temporal bone of the
cranium is called the temporomandibular joint (TMJ).
• Separating these two bones from direct articulation is the articular disc.
• Functionally, the articular disc serves as a non ossified bone that permits
the complex movements of the joint.
• The articular disc is composed of dense fibrous connective tissue, for the
most part devoid of any blood vessels or nerve fibers except the extreme
periphery.

17. • In the sagittal plane, it can be divided into
three regions according to thickness.
• The central area is the thinnest and is called
the intermediate zone. The disc becomes
considerably thicker both anterior and
posterior to the intermediate zone.

18. • The articular disc is attached posteriorly
to a region of loose connective tissue
that is highly vascularized and
innervated. This tissue is known as the
retrodiscal tissue or posterior
attachment.
• The superior and inferior attachments of
the anterior region of the disc are to the
capsular ligament.
• Superior attachment
temporal bone
• Inferior attachment condyle.

19. • The internal surfaces of the cavities are surrounded by specialized
endothelial cells that form a synovial lining. This lining, along with a
specialized synovial fringe located at the anterior border of the retrodiscal
tissues, produces synovial fluid, which fills both joint cavities.
• Synovial fluid lubricates the articular surfaces by way of two mechanisms.
• The first is called boundary lubrication, which occurs when the joint is
moved and the synovial fluid is forced from one area of the cavity into
another. It prevents friction in the moving joint.

20. • A second lubricating mechanism is called weeping lubrication. This refers
to the ability of the articular surfaces to absorb a small amount of synovial
fluid.
• Weeping lubrication helps eliminate friction in the compressed but not
moving joint.
• Only a small amount of synovial fluid is expressed as a result of weeping
lubrication; therefore prolonged compressive forces to the articular surfaces
will exhaust this supply.

21. HISTOLOGY OF ARTICULAR SURFACES
• The articular cartilage of the mandibular
condyle and fossa are composed of four
distinct layers or zones.
1. Articular Zone – Fibrous connective tissue
2. Proliferative Zone – Undifferentiated
mesenchymal tissue
3. Fibrocartilaginous Zone – Collagen fibres
4. Calcified Cartilage Zone- Chondrocytes
and chondroblasts

22. INNERVATION OF THE TMJ
• The Trigeminal nerve provides motor and sensory innervation to the
muscles that control it.
• Branches of the Mandibular nerve (V3) provide the afferent innervation.
• Most innervation is provided by the Auriculotemporal nerve as it leaves
the mandibular nerve behind the joint and ascends laterally and superior to
wrap around the posterior region of the joint.
• Additional innervation is provided by the Deep temporal and Masseteric
nerves.

23. VASCULARIZATION OF THE TMJ
• The predominant vessels are
Posterior - Superficial Temporal artery
Anterior – Middle meningeal Artery
Inferior – Maxillary Artery
Other important arteries: Deep auricular, Anterior Tympanic, Ascending Pharyngeal arteries
along with Inferior Alveolar artery.

24. LIGAMENTS
• Ligaments are made up of collagenous connective tissues fibers that do not stretch unless
extensive forces are applied.
• Three functional ligaments support the TMJ:
1. The collateral ligaments
2. The capsular ligament
3. The temporomandibular ligament.
• There are also two accessory ligaments:
1. The sphenomandibular
2. The stylomandibular.

25. COLLATERAL (DISCAL) LIGAMENTS
• The collateral ligaments attach the medial
and lateral borders of the articular disc to the
poles of the condyle.
• There are two discal ligaments:
The medial discal ligament
The lateral discal ligament
They function to restrict movement of the
disc away from the condyle and are
responsible for the hinging movement of
TMJ.

26. CAPSULAR LIGAMENTS
• The entire TMJ is surrounded and encompassed by
the capsular ligament.
• Superiorly : Fibers are attached to temporal bone
• Inferiorly : The fibers are attached to the neck of the
condyle.
• The capsular ligament acts to resist any medial,
lateral, or inferior forces that tend to separate or
dislocate the articular surfaces.
• A significant function of the capsular ligament is to
encompass the joint, thus retaining the synovial fluid

27. TEMPOROMANDIBULAR LIGAMENT
• The TM ligament is composed of two parts,
• an outer oblique portion: resists excessive
dropping of the condyle hence limiting the
extent of mouth opening.
• an inner horizontal portion: limits posterior
movements of condyle and disc, therefore
protects the retrodiscal tissues from trauma.
• It also protects Lateral Pterygoid muscle from
overextension

29. SPHENOMANDIBULAR LIGAMENT
• It arises from the spine of the sphenoid
bone and extends downward to a small
bony prominence on the medial surface
of the ramus of the mandible called the
lingula.
• It does not have any significant limiting
effects on mandibular movement.

30. STYLOMANDIBULAR LIGAMENT
• It arises from the styloid process and extends
downward and forward to the angle and
posterior border of the ramus of the mandible.
• It becomes taut when the mandible is
protruded, but is most relaxed when the
mandible is opened.
• The stylomandibular ligament therefore limits
excessive protrusive movements of the
mandible.

31. MUSCLES OF MASTICATION
• According to amount of myoglobin present, muscles can be either
1. Slow/Type I muscle fibers- Red in color due to high concentration of myoglobin
Capable of slow but sustained contraction
Aerobic metabolism and therefore resistant to
fatigue.
2. Fast/type II muscle fibers- Whiter due to low concentration of myoglobin
Fewer mitochondira and rely more on anaerobic
activity
Capable of quick contraction but fatigue more
quickly.

32. MUSCLES OF MASTICATION
• Four pairs of muscles make up a group called the muscles of mastication:
the masseter, temporalis, medial pterygoid, and lateral pterygoid.
• The digastrics also play an important role in mandibular function.

33. THE MASSETER
• Origin- The zygomatic process of the
maxilla and the anterior two thirds of the
lower border of the zygomatic arch.
• Insertion- The angle and lower half of the
lateral surface of the ramus of the
mandible.
• Function- Elevates the mandible and
contributes to protrusion

34. THE TEMPORALIS
• Origin- The lateral aspect of the skull to
the full extent of the superior temporal line
• Insertion- The anterior border of the
coronoid process and the anterior border
of the ramus of the mandible as far
forward as the last molar tooth
• Function- Elevates the mandible,
contributes to retrusion

35. THE MEDIAL PTERYGOID
• Origin- The medial surface of the lateral
pterygoid plate and the grooved surface
of the pyramidal process of the palatine
bone.
• Insertion- The inferior and posterior
portion of the medial surface of the
ramus and angle of the mandible, as high
as the mandibular foramen
• Function- Elevates the mandible,
contributes to protrusion

36. THE LATERAL PTERYGOID
• The lateral pterygoid is divided and identified as two distinct and different muscles, since
their functions are nearly opposite.
1. Superior Lateral Pterygoid
2. Inferior Lateral Pterygoid

37. SUPERIOR LATERAL PTERYGOID
• Origin- The lower part of the lateral
surface of the great wing of the sphenoid
and from the infratemporal crest.
• Insertion- The neck of the mandibular
condyle and into the front margin of the
articular disc.
• Function- Stabilizes the condyle and disc
during mandible loading (i.e., unilateral
chewing)

38. INFERIOR LATERAL PTERYGOID
• Origin- The lateral surface of the lateral pterygoid
plate.
• Insertion- The neck of the mandibular condyle
• function- Protrudes the mandible, contributes to
lateral movements and mouth opening

39. PERSPECTIVES ON THE ROLE OF THE LATERAL PTERYGOID
MUSCLE AND THE SPHENOMANDIBULAR LIGAMENT IN
TEMPOROMANDIBULAR JOINT FUNCTION
• S Abe , Y Ouchi, Y Ide, H Yonezu
• According to observations, the lateral pterygoid muscle fibers attach to the articular disk at the
inner point of the medial pole. Based on this finding, the muscle fibers can both draw the
articular disk anteriorly and balance it by supporting it posteriorly.
• Thus the lateral pterygoid muscle has two actions: to elevate the articular disk anteriorly and to
support the articular disk.
• Furthermore, the sphenomandibular ligament has continuity with the articular disk tissue
medially. This relationship suggests that the ligament fibers attached to the articular disk draw
the disk posteriorly in its course of mandibular closing, thus enabling the articular disk to move
smoothly.

40. THE DIGASTRIC
• Although the digastric is not generally considered a muscle of mastication, it does have an
important influence on the function of the mandible.
• It is divided into two portions or bellies
1. Anterior belly
2. Posterior belly

41. ANTERIOR DIGASTRIC
• Origin- A depression on the inner side of the lower
border of the mandible, close to the symphysis.
• Insertion- A tendon which passes through a
tendinous pulley attached to the hyoid bone. The
anterior digastric attaches to the tendon of the
posterior digastric muscle.
• Function- Depresses the mandible and elevates
the hyoid bone

42. POSTERIOR DIGASTRIC
• Origin- The inferior surface of the skull, from the
mastoid notch on the medial surface of the
mastoid process of the temporal bone and a
deep groove between the mastoid process and
the styloid process.
• Insertion- The posterior digastric attaches to the
tendon of the anterior digastric muscle.
• Function- Depresses the mandible and elevates
the hyoid bone.

43. FUNCTIONS
Elevation
Temporalis
Retrusion
Medial Pterygoid
Temporalis
Depression
Mylohyoid
Inf belly of Digastric
Lateral
Movements
Medial Pterygoid
Lateral Pterygoid
Protusion
Medial Pterygoid
Lateral Pterygoid

44. BIOMECHANICS OF THE TMJ
• The TMJ is an extremely complex joint system.
• The fact that there are two TMJs connected to the same bone further
complicates the function of the entire masticatory system.

45. BIOMECHANICS OF THE TMJ
• The TMJ is a compound joint.
• Its structure and function can be divided into two distinct systems:
1. Joint system - surrounds the inferior synovial cavity (condyle- disc
complex)
 Since the disc is tightly bound to the condyle by the lateral and medial
discal ligaments, the only physiologic movement that can occur between
these surfaces is rotation of the disc on the articular surface of the condyle.
 The disc and its attachment to the condyle are called the condyle-disc
complex and is the joint system responsible for rotational movement in the
TMJ.

46. BIOMECHANICS OF THE TMJ
2. The Condyle-disc complex functioning against the surface of the mandibular
fossa.
 Since the disc is not tightly attached to the articular fossa, free sliding
movement is possible between these surfaces in the superior cavity.
 This movement occurs when the mandible is moved forward (referred to as
translation).
Translation occurs in this superior joint cavity between the superior surface of
the articular disc and the mandibular fossa.
Thus the articular disc acts as a nonossified bone.

47. • The articular surfaces of the joint have no structural attachment or union,
yet contact must be maintained constantly for joint stability.
• Stability of the joint is maintained by constant activity of the muscles that
pull across the joint, primarily the elevators.
• Even in the resting state, these muscles are in a mild state of contraction
called tonus.
• As muscle activity increases, the condyle is increasingly forced against the
disc and the disc against the fossa, resulting in an increase in the
interarticular pressure of these joint structures.

48. • When the pressure is low, (in the closed rest position) the disc
space widens slightly.
• When the pressure is high (during clenching) the disc space
narrows
• As the interarticular pressure increases the condyle seats itself
on the intermediate zone.
• When the pressure is decreased and the disc space is widened, a thicker
portion of the disc is rotated to fill the space.
• The width of the articular disc space varies with interarticular pressure.

49. • When the mouth is closed, the elastic traction on the
disc is minimal to none.
• During mandibular opening, when the condyle is
pulled forward down the articular eminence, the
superior retrodiscal lamina becomes increasingly
stretched, creating increased forces to retract the
disc.
• As the mandible moves into a full forward position
and during its return, the retraction force of the
superior retrodiscal lamina holds the disc rotated as
far posteriorly on the condyle as the width of the
articular disc space will permit

50. • Anterior border of the articular disc is attached
to – Superior Lateral Pterygoid.
• Constantly maintained in a mild state of
contraction – exerts slight anterior and medial
force on the disc.
• In resting closed joint position, anterior and
medial force will normally exceed that of
nonstretched superior retrodiscal lamina.

51. MOVEMENTS
OF TMJ

52. MANDIBULAR MOVEMENTS
• The movements can be categorized into the following types:
1. Basic movements
2. Excursive movements
3. Border movements
4. Functional movements
5. Parafunctional movements

53. BASIC MOVEMENTS
A. Rotation (hinge movement)
 Definition: The action or process of rotating
on or as if on an axis or centre (GPT9).
 Occurs in first 12mm of mouth opening.
 Inferior portion of the joint between the head
of the condyle and lower surface of the disc

54. B. Translation
 Definition: That motion of a rigid body in which a
straight line passing through any two points always
remains parallel to its initial position. The motion
may be described as a sliding or gliding motion
(GPT9)
 This refers to bodily movement of the condyle. It
occurs during all the excursive mandibular
movements.
Translation occurs in the superior joint cavity
between the superior surface of the articular disc
and the inferior surface of the glenoid fossae

55. EXCURSIVE MOVEMENTS
• Definition: Movement occurring when the mandible moves away from maximum
intercuspation.
• Excursive movements are a combination of rotation and translation.
• The excursive movements are
1. Opening and closing
2. Protrusion and retrusion
3. Lateral excursion

56. • Protrusion: A position of the mandible
anterior to CR (GPT9).
• The condyles translate downwards and
forwards in the glenoid fossa depending on
the degree of protrusion.
• The movement is not in a straight line and is
dictated by the contour of the glenoid fossa.
• Retrusion: Movement towards the posterior
(GPT9).

57. • Lateral excursion: Movement produced when
the mandible moves laterally (side to side or
right and left).
• When the mandible moves laterally (side to
side), the side to which it moves is termed as
the ‘working side’ or ‘functional side’ and the
other side is termed as the ‘nonworking side’,
‘balancing side’ or ‘nonfunctional side.
• The working side condyle can just rotate on its
axis or move outwards and laterally. This is
termed as the ‘laterotrusion’ or ‘mandibular
lateral translation’ or ‘Bennett movement’.

58. BORDER MOVEMENTS
• Definition: Mandibular movement at the limits
dictated by anatomic structures, as viewed in a
given plane (GPT9).
• Border movement in sagittal plane:
• This traces the movement as the mandible moves
from centric occlusion (CO) to maximal protrusion
(F) to maximal mouth opening (E) and then closing
while returning to CO.
• While closing, condyle translates (EB) and then
rotates (B-CO) as explained in ‘opening movements’

59. • Border movement in horizontal plane
• This traces the movement from CR to right and
left extreme lateral movements, maximal
protrusion and then returns to CR.
• This characteristic tracing forms the basis of
‘gothic arch tracing’ used to record centric and
eccentric jaw relations.

60. • Border movement in frontal plane
• This traces the movement from CR to right
and left extreme lateral movements to
maximal mouth opening and back

61. • Envelope of motion
• Definition: The three-dimensional space
circumscribed by mandibular border
movements within which all unstrained
mandibular movements occur (GPT9).

62. 1. Depression
 Lateral Pterygoid
2. Elevation
 Temporalis
 Masseter
 Medial Pterygoid
4. Retraction
 Posterior fibres
of Temporalis
3. Protusion
 Lateral and
 Medial Pterygoid

63. FUNCTIONAL MOVEMENTS
• Chewing, swallowing, speaking, yawning and
associated movements constitute the
functional movements of the mandible.
• These take place within the border
movements.
• The envelope of motion recorded during
chewing appears as a characteristic ‘tear
drop’ and can be viewed in all three planes.

64. CHEWING CYCLE
• The chewing cycle can be divided into opening and closing phases.
• Closing phase is further divided into crushing phase and grinding phase.
• The chewing cycle was divided into the following six phases by Murphy:
(i) Preparatory phase: The mandible deviates towards the chewing side and
the tongue positions the food within the oral cavity.
(ii) Food contact phase: Sensory receptors are triggered due to food
contact.
(iii) Crushing phase: Starts at a high velocity and slows down as the food
gets crushed.

65. (iv) Phase of tooth contact: Reflex muscular adjustments for tooth contact
are made. A slight change in the direction occurs without delay.
(v) Grinding phase: Maxillary and mandibular occlusal tables guide the
grinding movement.
(vi) Centric occlusion: The cuspal inclines slice the food, as the mandible
moves in an incline and then returns into a single terminal point before going
into the preparatory phase. Usual masticatory frequency is one to two strokes
per second. A tear drop tracing is obtained, when tracing is recorded for the
chewing cycle in the sagittal plane

66. PARAFUNCTIONAL MOVEMENTS
• These are sustained movements of the mandible that occur other than
normal, manifested by long periods of increased muscle activity.
• They are almost impossible for the patient to control.
• The two most common parafunctional activities are bruxism and clenching.
• Parafunctional movements of the mandible are activities that serve no
useful function and are potentially harmful to the dentition and its contiguous
structures. They can cause restricted mandibular movements.

67. NEUROMUSCULAR SYSTEM
• The muscles responsible show increased activity and may be associated
with movement, fixation or stabilization of mandible such that there is a
smooth and coordinated movement from one position to another.
• The impulses may arise at the conscious or subconscious levels and result
in voluntary or involuntary muscular activity respectively.

68. CONCLUSION
 It is impossible to comprehend the fine points of occlusion without an in
depth awareness of the anatomy, physiology and biomechanics of the TMJ.
The first requirement for a successful occlusal treatment is stable and
comfortable TMJ.
The jaw joints must be able to accept maximum loading by the elevator
muscles with no signs of discomfort.
It is only through an understanding of how the normal, healthy TMJ
functions that we can make sense out of what is wrong when it isn’t
functioning comfortably.

69. REFERENCES
• Fundamentals of Occlusion and TMj disorders – Okeson
• Gray’s Anatomy
• Grant’s Atlas of Human Anatomy
• Occlusion – Ash Ramfjord
• Abe S, Ouchi Y, Ide Y, Yonezu H. Perspectives on the role of the lateral pterygoid muscle
and the sphenomandibular ligament in temporomandibular joint function. Cranio. 1997
Jul;15(3):203-7.

70. THANKYOU