Growth and development of temporo mandibular joint / invisible aligners

GROWTH AND DEVELOPMENT OF
TEMPOROMANDIBULAR JOINT
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com

CONTENTS
Introduction
Evolution of TMJ
Embryology
Growth and Development
Age changes
Histology
Functional Anatomy and Biomechanics
 Movements of TMJ
TMJ disorders
Summary and Conclusion
References

INTRODUCTION

Evolution of TMJ
The agnatha, the earliest type of vertebrae, had its
mouth opening on the ventral side anteriorly along the
vertebral axis. This opening led through an
oropharyngeal channel to the gut proper. Slits that
opened to the outside functioned both for respiration
and food filtration, and were moved simultaneously in
cooperation with the mouth by a series of cartilages
called gill arches.
A GILL ARCH had an internal bend and the turning
point of this bend was a synarthosis, which was
considered to be the earliest form of a jaw joint. This
structure remains as an epiceratobranchial joint in the
present day shark. www.indiandentalacademy.com

GNATHOSTOMES
-1st
and 2nd
arches disappeared into the skull.
-3rd
and 4th
arch’s began to function in the prey capture: the
apparatus of jaw
As evolution proceeded;
-A more highly developed moveable jaw joint appeared in
OSTEICHYTES
-Formed by gill arches, the cartilagenous jaw was covered by
second jaws.
-Teeth developed in the bony plates around the mouth.
-Amphibians www.indiandentalacademy.com

In amphibians – had a dentary in the anterior end of
original cartilagenous jaw.
At posterior end it articulated with the quadrate bone, a
structure of maxilla.
Mammal like reptilia
Ex: Aligator
Is composed of a number of bony segments, of which
only the dentary is retained in the human mandible.www.indiandentalacademy.com

Two of these segment, quadrate and articulate both derived
from Meckel’s cartilage (1st
branchial arch) constitue the
non-mammalian jaw joint i.e. PRIMARY JOINT OR
QUADRATO-ARTICULAR JOINT are incorporated in all
mammals into the middle ear as:
-Incus
-Malleus
-Therefore the incudomalleolar joint is thus homologus
with repitilia jaw joint

Associated with the formation of ear ossicles,
a new jaw joint
TMJ made its first appearance in mammals.
Secondary joint / Squamosodentary joint
[As it is present between squamous part of temporal bone
and the mandible (dentary)].
- One can imagine this evolutionary transmission
occurring by means of a bony process which appeared
on the mandibular anterior to quadratoarticular joint
which at one time became large enough to contact the
skull.

Difference in
Mammalian jaw-joint Non mammalian jaw-joint
A) Convex joint surface Concave
B) Intra-articular disk Absent

EMBRYOLOGY
-Develops late in embryonic life.
-Compared with large joints of extremities.
-Associated with its late evolutionary development.
-During the 7th
prenatal week, the jaw joint lacks:
-Condylar growth cartilage.
-Joint cavities.
-Synovial tissues
-Articular capsule.
2 skeletal elements : mandible and temporal bone are
not yet in contact with each other.

7 week old embryo
-Meckel’s cartilage extends all the way from chin to base of the
skull.
-Serves as a scaffolding or strutt against which the mandible
develops.
-Provides a temporary articulation between mandible and base of
the skull until TMJ takes over.
-Near end of fetal life Meckel’s cartilage completes its
transformation:
-Incus
-Malleus
-Anterior ligament of malleus
-Sphenomandibular ligament
Meckel’s cartilage plays an a basic role in setting the evolutionary
stage for the emergence of this joint.www.indiandentalacademy.com

Articular Disc:
-Earliest appearance in 6 week old embryo.
-Muscular derivative of 1st
branchial arch.
-Disc analge- vague layer of mesenchyme
stretching across upper end of mandibular
ramus.
-No capsule.
-No condyle.

Articular Disc:
-At its anterior end, mesenchymal analge extends laterally
from superior border of LPM, to medial side of masseter
muscle.
-At the end of 6th
week, lateral pterygoid inserts not on
the mandibular but on the posterior end of Meckel’s
cartilage.
-During 7th
week – (LPM) joins upper end of mandibular
ramus; also continues posteriorly beyond this point with
mesenchyme analge des abv; these 2 structures insert in
common part of Meckel’s cartilage which becomes the
malleus.

At 7 weeks: the future condyle is still only a condensation of
mesenchyme resting on osseous lamella, which forms the mandibular
ramus.
12 week – condylar growth cartilage makes its 1st
appearance and
begins to develop a hemi-spherical articular surface.
By 13th
week – condyle and articular disc having moved up into
contact with temporal bone.
Only when such articular contact has been made do the joint cavities
develop.
Inferior space appearing first.
Disc begins to get compressed.
When central portion of disc is compressed this part becomes
avascular.

The articular capsule:
-Becomes recognizable during twelth week as a faint cellular
condensation along the medial and lateral sides of joint connecting
mandible with temporal bone.
-Articular disc merges peripherally with these condensations.
-Formation of capsule posterior to joint does not occur until
twenty-second week; when the Glaserian fissure; becomes narrow;
encroaching upon Meckel’s cartilage as it passes into middle ear.
-Articular disc becomes intercepted at the Glaserian fissure, loses
its continuity with malleus and develops definitive attachment to
anterior lip of GF.
-Joint cavities are now lined by synovial tissue and according to
Symons (1952), temporal bone now shows area of secondary
cartilage in medial part of the joint.www.indiandentalacademy.com

By 26th
week:
All components of TMJ present except articular eminence.
Meckel’s cartilage still extends through GF, but by thirty-
first week is transformed into sphenomandibular ligament.
By 39th
week:
Ossification of bones in this region has proceeded to the
point where; ligament gains its apparent attachment to
spine of sphenoid.

HISTOLOGY OF TMJ
Composed of 4 distinct layers:
-Articular.
-Proliferative.
-Fibro cartilaginous.
-Calcified cartilage.

The growth of face and cranium involves two basic types of growth
changes:
1) Displacement
2) Remodelling
- Both these process, together constitute the growth mechanism of
craniofacial skeleton.
- One of the most familiar phrases in facial biology is that the
face grows downwards and forwards.
- As mandibular moves forward and downward, it grows upward
and backward at the same time by an equal amount.
- The process of mandibular growth is complex; does not merely
involves condylar growth to accomplish these changes.
- About half of the periosteal surfaces of bone (mand) have fields
that are characteristically resorptive in character and about halfwww.indiandentalacademy.com

-For example, mandibular ramus grows
posteriorly, with about half of outside surfaces
undergoing resorption and about half deposition.
-The ramus at the same time becomes broader
because the amount of posterior bone deposition
exceeds the amount of anterior resorption on the
various surfaces.
-As the ramus grows posteriorly, the mandibular
condyle grows upward and backward by an
endochondral mode of bone formation, in contrast
to intermembranous manner of growth in other
parts of the ramus. www.indiandentalacademy.com

-The bone located where the condyle used to be
during past growth stages is remodelled,
successively into mandibular neck and a part of
the ramus.
-The endosteal surface of the mandibular neck,
rather than the outersurface, is oriented so that it
faces the upward and backward of condylar
growth.

The condyle as a major growth site:
-The condyle has been singled out as a special site
(centre) because it has a distinctive growth
cartilage, which provides certain special function
during growth.
-The posterior and superior manner of growth of
mandibular ramus required an endochondral type
of bone formation at its condylar junction with the
cranial floor because of the surface compression
involved. www.indiandentalacademy.com

-Cartilage of the condyle is a secondary or
adventitious cartilage as it was developed
secondarily often the original primary cartilage was
modified for a different function elsewhere in the
skull.
-The upward and backward growth of the condyle
has a resultant push effect against the basicranium,
with a subsequent displacement of the entire
mandibular downward and forward. (Condylar
thrust concept). www.indiandentalacademy.com

TMJ in the first decade of life:
-At birth, the mandible as a whole continues the
exuberant, but progressively diminishing period of
overall growth that was begun during the last
trimester in utero.
-During the first year of life the condyle : ↓
vascularization, entire growth cartilage layer
becomes significantly thinner. This continues upto
the third year.

-Morphologic changes take place from birth to the end of
mixed dentition by 8 months: Enlargement of articular
eminence and post glenoid region.
-During this time tympano-squamosal tissue begins to
close as the postglenoid process becomes fused with the
tympanic plate.
-By 2 ½ years the articular eminence increase from 2 to
4mm. This is due to resorption of the bone in the roof of
the mandibular fossa and bone deposition anterior and
posterior to the fossa leading to formation of ‘S’ shape
curve.

The process continues so that by 6-7 years the articular eminence
enlarges to 5-6mm in height.
By approximately 6-7 years of age
Articular layer of condyle becomes thicker
Cartilage layer becomes thinner – 0.3mm
Underlying trabeculae becomes progressively thicker.
Growth continues - 7 to 12 years of age.
Articular disk – highly vascularized and rich in fibroblasts during
the 1st
few years.
Progressively the vascularization decreases.
Posterior surface of the ramus the condylar neck and the condyle are
sites of active skeletal growth leading to relocation of the
mandibular condyle in superior and posterior direction (V principle
of Enlow).

TMJ in 2nd
and 3rd
decade:
Characterized by progressive slowing of growth process.
By 13-15 years decreased thickness of cartilage layer.
Presence of proliferative layer atleast till age of 18 years.
A cortical bone cap coalescing with subchondral trabecular
bone by 10-12 years of age. This increases in thickness
upto 3rd
decade of life.
Bone cap is completed by 20 years of age although
cartilage and sparse cartilage cells remain.

ADULT TMJ
-Cartilage completely replaced by the bone around the
beginning of 4th
decade.
-Articular tissue: Relatively unchanged – may undergo
changes depending on biomechanical loading.
-Deep to the articular layer in the region where
subchondral growth cartilage was located a chondroid
type bone may be found which directly overlies the bone
cap.

-This marks the end of active growth of the condyle.
-In older adult temporal fossa: less pronounced chondroid
layer.
-Articular eminence : is made of chondroid bone.
-Up through the 5th
decade mandibular fossa became
more deep and articular eminence becomes more
prominent.
-As age progresses further there is flattening of the
articular fossa and decrease in prominence of the articular
eminence.

FUNCTIONAL ANATOMY
(1) Bony components
-Condylar head
-Glenoid fossa
-Articular eminence
(2) Muscles
1) Muscles involved
in mastication.
2) Facial muscles.
3) Muscles of the
neck
(3) Soft tissue
-Articular disc
-Joint capsule
-Ligaments
-Muscles attached to
joint
(4) Arterial Supply
(5) Nerve supply
(6) Lymphatic drainage

BIOMECHANICS OF TMJ
- Complex joint system.
- Compound joint – Its structure and function can be divided
into 2 distinct system:
i) Condyle disc complex.
ii) Condyle disc complex and articulating surface of mandibular
fossa.
- Constant contact between joint surfaces for stability is
required.
- Disc space more at rest, decreases with an increase in pressure
of the joint.
- Retrodiscal lamina
- Lateral pterygoid. www.indiandentalacademy.com

 Movement involving the joints has beenMovement involving the joints has been
divided different phasesdivided different phases
• Occlusal or rest positionOcclusal or rest position
• Retruded opening phase or rotationRetruded opening phase or rotation
• Early protrusive opening phase or functionalEarly protrusive opening phase or functional
openingopening
• Late protrusive opening phase or translationLate protrusive opening phase or translation
• Early closing phaseEarly closing phase
• Retrusive closing phaseRetrusive closing phase

OCCLUSAL OROCCLUSAL OR
REST POSITIONREST POSITION
• The rest position is the first step and involves a static jaw
position with maximum intercuspation.
• In this, the joint is in loose pack
position, the connective tissue at rest
• The posterior band occupies the
deepest part of the mandible fossa
• The intermediate zone and the anterior band lies between
the condyle and posterior slope of the eminence

RETRUDED OPENING PHASERETRUDED OPENING PHASE
OR ROTATIONOR ROTATION
•The condyle rotates and moves 5 to 6 mm inferior to the
intermediate zone
•The condyle joint surface glides forward
and the medial pole of the condyle
moves anterosuperiorly and the
lateral pole moves posteroinferiorly
•The shape of inferior compartment
changes the most
•The upper lateral pterygoid relaxes and the lower lateral
pterygoid contracts
•The posterior connective tissues is in a functional state of
rest www.indiandentalacademy.com

EARLY PROTRUSIVE OPENINGEARLY PROTRUSIVE OPENING
PHASE OR FUNCTIONAL OPENINGPHASE OR FUNCTIONAL OPENING
•The condyle moves inferiorly and anteriorly approximately 6 to 9
mm below the intermediate zone.
•The disk and the condyle
experience the short anterior
translatory glide
•The upper and lower head of lateral pterygoid contract to guide
the disk and the condyle shortly forward
•The posterior connective tissues is in a functional tightning

LATE PROTRUSIVE OPENINGLATE PROTRUSIVE OPENING
PHASEPHASE
OR TRANSLATIONOR TRANSLATION
• The condyle moves inferiorly and anteriorly beneath the
anterior band i.e there is full
opening more, space develops
in the superior compartment
• The upper and lower head of
Lateral pterygoid contract to guide the disk and the condyle
fully forward
• The posterior connective tissues tightens

EARLY CLOSING PHASEEARLY CLOSING PHASE
The condyle translates posteriorly, about 6 to
9 mm, to the intermediate zone
There is simultaneous reduction of space
posteriorly in the superior compartment

RETRUSIVE CLOSING PHASERETRUSIVE CLOSING PHASE
• The condyle rotates superiorly but remains inferior to the
posterior band
• This movement reduces the space
in the inferior compartment
• The upper head of the lateral
pterygoid contracts and
• The lower head of the lateral
pterygoid relaxes
• This tightens the mandibular attachment, and forces blood
from the posterior compartments
• The posterior connective tissues returns to the functional rest
movements www.indiandentalacademy.com

TMJ DISORDERS
Classification:
1) Growth disorders and the joint
a) Developmental disorders.
b) Acquired disorders.
c) Neoplastic disorders.
2) Masticatory muscle disorders:
a) Protective muscle splinting.
b) Muscle hyperactivity or spasm.
c) Myositis (muscle inflammation).
3) Disk interference disorders (internal derangement)
a) Incoordination.
b) Deformation of articular disk.
c) Partial anterior disk displacement.
d) Anterior disk displacement with reduction.
e) Anterior disk displacement without reduction.
f) Anterior disk displacement with perforation.
g) Posterior disk displacement.

4) Problems that result from extrinsic trauma:
a) Tendonitis.
b) Myositis.
c) Traumatic arthritis.
d) Dislocations.
e) Fracture.
f) Internal derangements.

5) Degenerative joint disease:
• Arthrosis (non-inflammatory phase).
• Osteoarthritis (inflammatory phase).
• Osteochondritis disecans.
6) Inflammatory joint disorders:
• Synovitis and capsulitis
• Retrodiskitis.
• Inflammatory arthritis

7) Chronic mandibular hypomobility:
• Ankylosis.
• Fibrosis.
• Contracture of elevator muscle.
• Internal disk derangement.
8) Post surgical problems

Diseases affecting the TMJ are primarily
inflammatory and degenerative, while
developmental, metabolic and neoplastic conditions
are rare occurrences.
Developmental anomalies:
-Congenital
Genetic / Prenatal / Postnatal
Trauma
Nutritional deficiencies etc.
Acquired www.indiandentalacademy.com

Condylar agenesis
-Is frequently associated with various symptoms.
- if unilateral pronounced facial asymmetry under
developed mandible leads to distortion and depression
of that side of the face.
-Macrostomia.
-Absence of external ear.
-Alterations in dental occlusion.
-Bilateral condylar agenesis may present with
symmetrical severe underdevelopment of the
mandible. www.indiandentalacademy.com

Condylar Hypoplasia
-More frequent
-Causes: infection and trauma
-C/F: Facial deformity
-Limitation of lateral excursion.
-Shift of mandibular midline during opening of mouth.
Double mandibular condyle:
Etiology, embryologic, traumatic………..
-Usually unilateral
-Two condyles with one mandibular neck are involved.www.indiandentalacademy.com

Condylar hypoplasia:
Causes:
Infection
Trauma
Clinical features
-Symmetric enlargement of entire condylar
process.
-Limited movements.
-In adults lateral displacement and open bite.www.indiandentalacademy.com

ANKYLOSIS
Defined as chronic hypo mobility or immobility of a
usually moveable articulating surface.
Causes:
- Infection, trauma.
Classification:
1. Unilateral / bilateral.
2. Fibrous / bony.
3. Partial / complete.
4. True / false. www.indiandentalacademy.com

Degenerative Joint Diseases:
-Osteoarthritis.
-Non inflammatory process caused by local disease
involving one particular joint.
-Etiology is multifactorial: systemic factors, mechanical
stress, trauma.
-Other factors: tooth loss, Occlusal interferences,
Excessive forces of muscles in bruxism.
C/F: Crepitation, unilateral pain, feeling of stiffness after a
period of inactivity.
Treatment: NSAIDS, heat, soft diet, occlusal splints, intra
articular steroids, arthroplasty.www.indiandentalacademy.com

MPDS:
Is a pain referred from a localized tender area, a
trigger point, in a taut band of skeletal muscle,
including muscles of mastication.
Laskin stated that TMJ pain dysfunction syndrome
is a misnomer because the diorder was primarily
related to masticatory muscle spasm.

Signs and symptoms: Unilateral, dull pain in the
ear or preauricular region.
Tenderness of one or more muscles of mastication
on palpation.
Limitation or deviation of the mandible on
opening.
Causes: Chronic microtrauma, overuse,
irregularities in occlusion, posterior bite collapse,
deep overbite- overjet relationship.www.indiandentalacademy.com

Treatment:
•Treatment of emotional and physical components.
•Reviewing history of patients problems.
•Placebo drugs, splints or occlusal equilibration patient
reassurance.
•Spray and stretch : fluoromethane refrigerant spray.
•Injection LA at trigger point.
•Soft diet.
•NSAIDs
•Discontinuing parafunctional habits.
•Occlusal splint…….

CONCLUSION
The efforts of the prosthodontist to record the
movements of the TMJ and to reproduce them on the
articulator have been the chief stimulus for studies on
the functional structure of this joint.
In order to understand fully the nature of this joint, one
must begin with its evolutionary history, for its popular
evolution explained its astonishing embryological
development, from which comes its unique gross and
histological structure, all of this reaching final clinical
significance in the various functional and morphologic
disorders seen in this joint.

References:
1. Boucher: Prosthodontic treatment for Edentulous
Patients.
2. Donald H.Enlow : Essentials of Facial growth.
3. Laskin : Temporomandibular Joint
4. Orban’s: Oral Histology and Embryology.
5. Sharry: Complete denture Prosthodontics.
6. Sheldon Winkler : Essentials of Complete Denture
Prosthodontics.
7. Y.Ide: Anatomy of TMJ
8. Zarb : Temporomandibular Disorders.

Thank You
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Growth and development of temporo mandibular joint / invisible aligners

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