TEMPOROMANDIBULAR JOINT · Temporomandibular Joint • The area where the craniomandibular articulation occurs is called the temporomandibular joint • Articulation is defined as

TEMPOROMANDIBULAR JOINT

Lecture by:

Dr. Suhasini G P

Lecturer Dept. of Oral Pathology & Microbiology

Dr. Suhasini GP, Subharti Dental College, SVSU


Temporomandibular Joint

• The area where the craniomandibular articulation occurs is called the temporomandibular joint

• Articulation is defined as a loose joining or connecting together so as to allow motion between the parts.

• When the two objects are the bones of a skeleton, the articulation is called a Joint.

• One of the most complex joints in the body


• Provides for hinging movement in one plane- ginglymoid

• However, at the same time it also provides for gliding movements, which classifies it as an arthroidal joint.

• Thus, technically considered a ginglymoarthroidal joint.

• By definition, a compound joint requires the presence of at least 3 bones, yet the TMJ is made up of only 2 bones. Functionally, the articular disc functions as a 3rd bone- compound joint


• Temporomandibular joint

• Craniomandibular joint

• Bilateral diarthrodial joint

• Atypical synovial joint

• Compound joint

• Ginglymoarthrodial joint

• Modified ball socket joint


CLASSIFICATION OF JOINTS

• Fibrous

• Cartilaginous

• Synovial


Fibrous joints • In fibrous joint 2 bones are connected by fibrous

tissue. They are 3 types:

• 1. Sutures: Its function is to permit growth as its articulating surfaces are covered by osteogenic layer responsible for new bone formation. It permits little or no movement. Eg- skull bones

• 2. Syndesmoses: Two bony compartments are apart from each other but are joined by an intraosseous ligament. It permits limited movement. Eg- b/n tibia & fibula, b/n radius & ulna


Fibrous joints

• 3. Gomphoses: It is the joint that gives socketed attachment of tooth to bone by fibrous periodontal ligament. Movement is restricted to intrusion and recovery in response to biting force.


Cartilaginous joints

• Primary cartilagenous joint : Bone and cartilage are in direct apposition.

eg - costochondral junction

• Secondary cartilagenous : Tissues in articulation occur in sequence as bone-cartilage-fibrous tissue-cartilage-bone.

eg – pubic symphysis


Synovial joints • In a synovial joint, which generally permits significant

movement, two bones (each with an articular surface covered by hyaline cartilage) are united and surrounded by a capsule that thereby creates a joint cavity. This cavity is filled with synovial fluid formed by a synovial membrane that lines the nonarticular surfaces. They are classified as under :

A. On the number of axis in which bones involved can move – uniaxial ,biaxial, multiaxial.

B. By the shapes of articulating surfaces – planar, gingylmoid, pivot, condyloid, saddle, ball and socket.



DEVELOPMENT

• PRIMARY JOINT- exists for about 4 MONTHS

• MALLEUS AND INCUS

• SECONDARY JAW JOINT – at about 3 MONTHS of gestation it appears.

• TEMPORAL BLASTEMA

• CONDYLAR BLASTEMA



ANATOMY OF THE

TEMPOROMANDIBULAR JOINT

• Articular fossa

• Mandibular condyle

• Articular disc

• Articular Capsule

• Ligaments of TMJ Dr. Suhasini GP, Subharti Dental College, SVSU


Glenoid fossa / Articular Fossa/ Mandibular fossa

• Concave shape depression in squamous part of temporal bone

Post. Squamo & pterygo tympanic fissure

Medial spine of sphenoid

Lateral root of the zygomatic process of the temporal bone

Anterior ridge of bone

(articular eminence)

Middle part- thin, upper surface

forms the middle cranial fossa


Condyloid process

• It is the portion of the mandible that articulates with the cranium around which movement occurs

• Anterior view- it has a medial and lateral projections which are called as poles

• ML length - 15 to 20 mm

• AP length - 8 to 10mm.


• Posterior articulating surface is greater than anterior surface.

• The articulating surface of condyle is quite convex anteroposteriorly and only slightly convex mediolaterally.

• Pterygoid fovea on the antero-medial aspect of the mandibular neck where inferior head and most fibres of the superior head of lateral pterygoid muscle insert on the mandible.

Condyloid process


• Articular surface of the condyle (and the mandibular fossa) are composed of 4 zones

1. Superficial layer- articular zone

– Unlike most other synovial joints, this articular layer is made of dense fibrous CT, rather than hyaline cartilage

– Tightly packed Col fibers –arranged parallel to the articular surafce

– Advantage of fibrous covering over hyaline cartilage- less susceptible to aging effects, less likely to break down over time, better repairing ability

HISTOLOGY OF THE ARTICULAR SURFACES


2. Proliferating layer

- cellular

-responsible for proliferation of articular cartilage in response to functional demands placed on articular surface

-undifferentiated mesenchymal cells found


3.Fibrocartilagenous zone -Collagen fiber bundles in crossing pattern - fibrocartilage in random orientation , provides 3

dimensional network that offers resistance against compressive & lateral forces

4. Calcified zone -deepest zone, made up of chondrocytes

&chondroblasts distributed throughout the articular cartilage

- chondroblasts become hypertrophic, endochondral ossification occurs, loss of chondrocytes, differentiation of osteoblasts



• Condyle of mandible- cancellous bone covered by a thin layer of compact bone

• Trabeculae are grouped in such a way that they radiate from neck of mandible & reach cortex at right angles; max. strength to condyle

• Large marrow spaces decrease in size with progressing age

• Red marrow in the condyle is of the myeloid type


CARTILAGE

• Condylar cartilage

• Proliferative layer of replicating cells functioning as

progenitor cells for growth of cartilage

chondroblasts type II collagen (extracellular

matrix of cartilage)

• Endochondral ossification

• Mineralized cartilagenous framework is formed


• Fibrous layer covering the articular surface of temporal bone-

thin in articular fossa

thick on post. slope of articular surfaces

in thickened region – fibrous tissue is arranged in 2 layers


ARTICULAR DISC

• Dense fibrous connective tissue devoid of blood vessels and nerves

• Plate of flexible dense connective tissue • Bi-concave 1-2mm thick in centre & 3-4mm

thick at its periphery • Devoid of blood vessels and nerves in the

centre • Vascular peripherally • Divides joint cavity into upper & lower

compartment


• Sagittal plane divided into 3 regions according to the thickness

• Central area is thinnest and it is called intermediate zone

• Anterior and posterior - thick

• Articular surface of the condyle located on the intermediate zone of the disc bordered by the thicker anterior and posterior regions

• Shape of the disc governed by the morphology of the condyle and the mandibular fossa


Articular disc


• The articular disc is attached posteriorly to the region of loose connective tissue that is highly vascularized and innervated which is called as retrodiscal tissue or posterior attachments or bilaminar region.

– Superior retrodiscal lamina is fibrous & elastic that attaches AD posteriorly to tympanic plate

– Inferior retrodiscal lamina is non-elastic that attaches AD to posterior margin of articular surface of the condyle


Anterior region of the disc is attached to the capsular ligament Superior attachment is to the anterior margin of the articular surface of temporal bone Inferior attachment is to the articular surface of the condyle

The articular disc is attached to the capsular ligament not only anteriorly and posteriorly and also medially and laterally this divides the joint into two distinct cavities.


ARTICULAR DISC HISTOLOGY

• In young adults

-Disc is composed of dense fibrous tissue

interlacing fibres are straight & tightly packed

elastic fibres found in small no.

-Fibroblasts in the disk are elongated and send cytoplasmic processes b/w bundles


• Chondrocytes, with typical territorial matrices stains heavily with basic dyes

• increase the resistance & resilience of fibrous tissue

• Fibrous tissue covering articular eminence & condyle & in central area of the disc

-- Avascular, no nerves

-- Limited reparative ability


JOINT CAPSULE Fibroelastic sac

– ascending slope of the articular eminence anteriorly

– Squamotympanic fissure posteriorly

– Glenoid fossa superiorly

– Neck of the condyle inferiorly

• Synovial membrane of capsule lines all nonarticular surfaces of upper & lower compartments of the joint


• Posterior part of the capsule is highly vascular –pis vasculosa

• Parotid gland is found in posterior portion of glenoid fossa b/w posterior capsule of the joint & postglenoid tubercle

• Inner surface of the capsule is smooth & glistening b’coz of a synovial membrane


• Seals joint space

• Passive stability

• Anatomically recognizable ligaments

• Active stability from proprioception (Maintain position of the disc over the joint during functional movements)


Ligaments

• As with any joint system, ligaments play an important role in protecting the structures

• The ligaments of joints are made up of collagenous connective tissues which do not stretch.

• They do not enter actively into joint function but instead act as a passive restraining devices to limit and restrict border movements


3 functional ligaments that support the TMJ

• Collateral ligaments

• Capsular ligaments

• Temporomandibular ligament

3 accessory ligaments

• Sphenomandibular ligament

• Stylomandibular ligament

• Retinacular ligament


Collateral ligaments

• Discal ligaments

• They attach the medial and lateral borders of the articular disc to the poles of the condyle

• Medial discal ligament –attaches the medial edge of the disc to the medial pole of the condyle

• Lateral discal ligament-attaches the lateral edge of the disc to the lateral pole of the condyle


• The attachment of discal ligaments permit the disc to be rotated anteriorly and posteriorly on the articular surface of the condyle thus these ligaments are responsible for the hinging movements of the TMJ.

• The discal ligaments have a vascular supply and are innervated

• This innervation provides information regarding joint position and movement

• Strain on these ligaments produce pain


Capsular ligament

• Entire TMJ is surrounded and encompassed by the capsular ligament

• The fibers of capsular ligament are attached superiorly to the temporal bone along the borders of articular surfaces of the mandibular fossa and articular eminence

• Inferiorly attach to the neck of the condyle


• Capsular ligament acts to resist any medial, lateral or inferior forces that tend to separate or dislocate articular surfaces

• A significant function of the capsular ligament is to encompass the joint, thus retaining the synovial fluid.

• The capsular ligament is well innervated and provides proprioceptive feedback regarding position and movement of the joint.


Temporomandibular ligament

• The lateral aspect of the capsular ligament is reinforced by strong, tight fibers that make up lateral ligament or temporomandibular ligament.

• The temporomandibular ligament is composed of 2parts-

1. Outer oblique portion

2. Inner horizontal portion


• Outer oblique portion-extends from the outer surface of the articular tubercle and zygomatic process posteroinferiorly to the outer surface of condylar neck.

• Inner horizontal portion-extends from outer surface of the articular tubercle and zygomatic process posteriorly and horizontally to the lateral pole of the condyle and the posterior part of the articular disc.


Sphenomandibular ligament

• Arises from sphenoid process & extends

downwards & forwards to the lingula of the

mandible.

• limits excessive protrusive movements of the mand.


Stylomandibular ligament • Arises from styloid process & extends downwards &

forwards to the angle & posterior border of the

ramus of the mand.

• Limits protrusive movement of the mandible.


Synovial membrane

• Lines the articular capsule • Contain synovial villi which project into joint

space • Contain internal cells which do not form a

continuous layer i.e. gap b/w cells

• Ability to regenerate

• Membrane does not cover articular disk except for posterior bilaminar region


Consists of 2 layers 1. Cellular intima- 1-4 layers of synovial cells

2. Vascular sub-intima -prevents folding of

membrane- loose connective tissue contains vascular elements with fibroblasts, macrophages, mast cells & fat cells

• Cells forming the cellular intima are of 3 types

1.fibroblast like or B-cell type (secretory or S cell)

2.macrophage like or A-cell type

3.between type A and type B.


Synovial fluid

• Clear, straw coloured viscous fluid found in articular spaces

• Liquid environment for joint surface

• Lubricant (increases efficiency & reduce erosion.)

• Nutrient fluid for avasular tissues covering condyle, articular tubercle & disc


SYNOVIAL FLUID

• Composition - dialysate of plasma with some added protein of mucin

• Cells:

Monocytes

Lymphocytes

Free synovial cells

PMN leukocytes

• Protein mucin & hyluronic acid



INNERVATION

• Movements of synovial joint initiated & effected by muscle coordination.

• Achieved in part through sensory innervation.

• Hilton’s Law: • The muscles acting on a joint have the same nerve supply as

the joint.

• Therefore: Branches of the mandibular division of the fifth cranial nerve supply the TMJ (auriculotemporal, deep temporal, and masseteric)


capsule

capsule

most abundant

INNERVATION


Vascularization of TMJ

• Predominant vessels:

Superficial temporal artery (post.)

Middle meningeal artery (ant.)

Inferior maxillary artery

• Other arteries

Deep auricular

Ant. Tympanic

Ascending pharyngeal


CLINICAL CONSIDERATIONS

• FRACTURES results because of thinness of bone in articular fossa injury to the dura mater & brain.

• Change in force/ direction of stress degeneration of fibrous covering of articulating surfaces & disc

• Remodelling of the articular surface- functional demands, loss of teeth, attrition, othodontic treatment.

• Abnormal functional activity injury to fibrous covering & articular disc


• Deviation of mandible on opening & closing popping & clicking noise

• Internal DISC DERRANGEMENT or dislocation.

• DISLOCATION of TMJ

• TMJ ANKYLOSIS

• MYOFACIAL PAIN SYNDROME : dysfunction of TMJ, consists of • Masticatory muscle tenderness • Limited opening of mandible < 37 mm. • Joint sounds


Diagnostic techniques

• CT scan

• MRI

• Arthroscopy

• X rays


REFERENCE

• Fundamentals of occlusion and TMJ disorders - Okeson

• Williams PL: Gray’s anatomy, in Skeletal System (ed38).

• Orban's oral histology and embrology 13th ed.

• Ten Cate's Oral Histology, 8ed


THANK U


TEMPOROMANDIBULAR JOINT · Temporomandibular Joint • The area where the craniomandibular articulation occurs is called the temporomandibular joint • Articulation is defined as

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