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ANATOMY OFTEMPOROMANDIBULAR JOINT
Presented By :
Dr. Abhishek Nagpal
Date :
29th August, 2006
Department of Prosthodontics Including Crown & Bridge,
Maxillofacial Prosthodontics & Oral Implantology.
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DEFINITIONS
CENTRIC OCCLUSION
The occlusion of the opposing teeth when the
mandible is in centric relation. This may or may notcoincide with the maximum intercuspal position
GPT-8th ed.
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DEFINITIONS
CENTRIC RELATION
The maxillomandibular relationship in which the
condyles articulate with the thinnest avascular
portion of their respective discs with the complex inthe anterior-superior position against the shapes of
the articular eminencies. This position is
independent of tooth contact. This position is
clinically discernible when the mandible is directed
superior & anteriorly. It is restricted to a purely
rotatory movement about the transverse horizontal
axis
GPT-8th ed.
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DEFINITIONS
MAXIMAL INTERCUSPAL POSITION
The complete intercuspation of the opposing teethindependent of condylar position, sometimes
referred to as the best fit of teeth regardless of the
condylar position
GPT-8th ed.
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TEMPOROMANDIBULAR JOINT
INTRODUCTION
The area where
craniomandibular
articulation occurs is called
the temporomandibularjoint
The TMJ is the most
complex joint in the body
It provides for hingingmovement in one plane &
therefore can be
considered a ginglymoid
joint
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TEMPOROMANDIBULAR JOINT
INTRODUCTION
At the same time it also provides for glidingmovement, which classifies it as anarthroidial joint
Thus it has been technically considered as aginglymoarthroidal joint
The TMJ is formed by the mandibularcondyle fitting into the mandibular fossa ofthe temporal bone
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TEMPOROMANDIBULAR JOINT
INTRODUCTION
Separating these two bones from direct articulation
is the articular disc
The TMJ is classified as a compound joint, a
compound joint requires the presence of at least
three bones, yet the TMJ is made up of 2 bones
Functionally the articular disc serves as a
nonossified bone that permits the complex
movement of the joint
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TEMPOROMANDIBULAR JOINT
INTRODUCTION
The articular disc iscomposed of dense fibrous
connective tissue devoid of
any blood vessels or nerve
fibers
The central zone is the
thinnest & is called the
intermediate zone
In the normal joint the
articular surface of thecondyle is located on the
intermediate zone of the disc,
bordered by the thicker
anterior & posterior zones
ARTICULAR DISC OF TMJ
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TEMPOROMANDIBULAR JOINT
TEMPOROMANDIBULAR J OINT (LATERALVIEW)
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TEMPOROMANDIBULAR JOINT
INTRODUCTION
The disc is attached posteriorly to an area of loose
connective tissue that is highly vascularized &
innervated, known as the retrodiscal tissue
Superiorly it is bordered by a lamina of connective
tissue that contains many elastic fibers, the superior
discal lamina
Since this region consists of two areas, it is referred
to as the bilaminary zone
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TEMPOROMANDIBULAR JOINT
INTRODUCTION The superior retrodiscal
lamina attaches thearticular disc posteriorlyto the tympanic plate
At the lower border ofthe retrodiscal tissues isthe inferior retrodiscallamina, attaching theinferior border of theposterior edge of thedisc to the posteriormargin of the articularsurface of the condyle TMJ : ANTERIOR VIEW
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TEMPOROMANDIBULAR JOINT
INTRODUCTION The remaining body of the retrodiscal tissue is
attached posteriorly to a large ligament that
surrounds the entire joint, the capsular ligament
The superior & inferior attachments of the anteriorregion of the disc are also by the capsular ligament
The superior attachment is to the anterior margin of
the articular surface of the temporal bone
The inferior attachment is to the anterior margin ofthe articular surface of the condyle
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TEMPOROMANDIBULAR JOINT
INTRODUCTION Anteriorly between the attachments of the capsular
ligament the disc is also attached by tendinous
fibers of the superior lateral pterygoid muscle
Like the articular disc the articular surfaces of the ofthe mandibular fossa & the condyle are lined with
dense fibrous connective tissue rather than hyaline
cartilage in most other joints
The fibrous connective tissue is generally lesssusceptible than hyaline cartilage to the effects of
ageing & therefore less likely to breakdown over
time
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TEMPOROMANDIBULAR JOINT
INTRODUCTION
Also it has a much greater ability to repair than the
hyaline cartilage The articular disc is attached to the capsular
ligament not only anteriorly & posteriorly but also
medially & laterally, thus dividing the joint into 2
distinct cavities
The internal surfaces of the cavities are surrounded
by specialized endothelial cells that form a synovial
lining
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TEMPOROMANDIBULAR JOINT
INTRODUCTION
This lining, along with a specialized synovial fringe
located at the anterior border of the retrodiscaltissues, produces synovial fluid which fills both the
joint cavities
Thus the TMJ is referred to as a synovial joint
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TEMPOROMANDIBULAR JOINT
INTRODUCTION This synovial fluid serves following purposes
1. Provides metabolic requirements to the
nonvascular articular surfaces of the joint
2. Provides free & rapid exchange between thevessels of the capsule, the synovial fluid & the
articular tissues
3. Serves as a lubricant between articular surfaces
during function4. Minimizes the friction produced between the
articular surface of the disc, condyle & the fossa
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TEMPOROMANDIBULAR JOINT
INTRODUCTION
The synovial fluid lubricates the articular surfaces by
way of two mechanisms: Boundary Lubrication- Occurs when the joint is
moved & the synovial fluid is forced from one
area of the cavity into another. The synovial fluid
is forced upon the articular surfaces thus
providing lubrication. Boundary lubrication
prevents friction in the moving joint
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TEMPOROMANDIBULAR JOINT
INTRODUCTION
The synovial lubricates the articular surfaces by way
of two mechanisms: Weeping Lubrication- Ability of the articular
surfaces to absorb a small amount of synovial
fluid. Thus, when articular surfaces are placed
under compressive forces this small amount of
synovial fluid, is released, lubricating the tissues.
Weeping lubrication helps eliminate friction in the
compressed but not moving joint
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DEVELOPMENT OF THE JOINT
The components of the joint show the first indication
in the mesenchyme between the condylar cartilage
of the mandible & the developing temporal bone at
about 10 weeks of intrauterine life
Two slit like joint cavities & an intervening disc
appear in this region at about 12 weeks of
intrauterine life
The mesenchyme around the joint begins to form thefibrous capsule
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DEVELOPMENT OF THE JOINT
HISTOLOGY:
Bony structure
The condyle of the mandible is composed ofcancellous bone covered by a thin layer of compactbone
CANCELLOUS BONE COMPACT BONE
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DEVELOPMENT OF THE JOINT
HISTOLOGY:
Bony structure
The trabeculae radiate from the neck of themandible & reach the cortex at right angles, thus
giving maximum strength to the condyle
The red marrow in the condyle is of the myeloid or
cellular type & in older individuals it is sometimes
replaced by the fatty marrow
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DEVELOPMENT OF THE JOINT
HISTOLOGY:
Bony structure During this period of growth
a layer of hyaline cartilage
lies underneath the fibrous
covering of the condyle This cartilaginous plate
grows by the apposition from
the deepest layers of the
covering connective tissue Its deepest surface is
replaced by bone & the
remnants of this cartilage
may persist into old age
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DEVELOPMENT OF THE JOINT
HISTOLOGY:
Bony structure
The roof of the mandibular fossa consists of athin, compact layer of bone
In rare cases islands of hyaline cartilage are
found in the articular tubercle
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DEVELOPMENT OF THE JOINT
HISTOLOGY:
Articular Fibrous Covering The condyle as well as the
articular tubercle is covered by a
fairly even thickness of fibrous
tissue containing a variablenumber of chondrocytes
Its superficial layers consist of a
network of strong collagenous
fibers The deepest layer of the
fibrocartilage is rich in
chondroid cells as long as
growing hyaline cartilage is
present in the condyle
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DEVELOPMENT OF THE JOINT
HISTOLOGY: Articular Fibrous Covering
The fibrous tissue in thisregion shows a definite
arrangement in two layers,with a small transition zonebetween them & arecharacterized by the differentcourse of the constituent
fiber bundles In the inner zone the fibers
are at right angles to thebony surface, & in the outerzone they run parallel to that
surface
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DEVELOPMENT OF THE JOINT
HISTOLOGY:
Articular Disc
In young individuals thearticular disc is composed
of dense fibrous tissue
The interlacing fibers are
straight & tightly packed
Elastic fibers are found in
relatively small numbers
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DEVELOPMENT OF THE JOINT
HISTOLOGY:
Articular Disc
The fibroblasts in the disc are elongated & sendflat cytoplasmic wiglike processes into the
interstices between the adjacent bundles
With advancing age, some of the fibroblasts
develop into chondroid cells, which later may
differentiate into chondrocytes, sometimes small
islands of chondrocytes may be found in discs of
older persons
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DEVELOPMENT OF THE JOINTHISTOLOGY:
Articular Capsule A small amount of a clear,
straw-colored viscous fluid,synovial fluid is found in thearticular spaces
It is a lubricant & also anutrient fluid for the avasculartissues covering the condyle& the articular tubercle & for
the disc It is elaborated by diffusion
from the rich capillarynetwork of the synovialmembrane, augmented by the
synovial cells
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ANATOMY OF THE JOINT
Articular Surface The upper articular surface
is formed by the followingparts of the temporal bone:
The articular eminence
Anterior part of themandibular fossa
The inferior articular surfaceis formed by the head of themandible
The articular surfaces arecovered with fibrocartilage
The joint cavity is dividedinto upper & lower parts byan intra-articular disc
ARTICULAR SURFACES OFTHE TMJ
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ANATOMY OF THE JOINT
Articular Disc
The articular disc is an
oval fibrous plate that
divides the joint into an
upper & lower
compartment
The upper compartment
permits the glidingmovements & the lower
compartment permits,
rotatory as well as
gliding movements
ARTICULAR SURFACES OFTHE TMJ
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ANATOMY OF THE JOINT
Articular Disc
The disc has a concavo-convex superior surface & a
concave inferior surface
The periphery of the disc is attached to the fibrous
capsule
The articular disc has been commonly referred to as
a meniscus, however it is not a meniscus at all
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ANATOMY OF THE JOINT
Articular Disc
A meniscus is a wedgeshaped crescent offibrocartilage attached onone side to the articularcapsule & unattached onthe other side, extendingfreely into the joint spaces
A meniscus does not dividea joint cavity, isolating the
synovial fluid, nor does itserve as a determinant ofthe joint movement
It functions passively tofacilitate the movement
between the bony parts
STRUCTURE OF ASYNOVIAL J OINT
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ANATOMY OF THE JOINT
Ligaments:
There are two accessory ligaments:-
The sphenomandibular ligament
The Stylomandibular ligament
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ANATOMY OF THE JOINT
Ligaments:
The Collateral (Discal) Ligaments:- The collateral
ligaments attach the medial & lateral borders of the
articular disc to the poles of the condyle
They are commonly called the discal ligaments, &
are two
The medial discal ligament
The lateral discal ligament
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ANATOMY OF THE JOINT
Ligaments:
The medial discal ligament
attaches the medial edge of
the disc to the medial pole
of the condyle
The lateral discal ligament
attaches the lateral edge of
the disc to the lateral pole
of the condyle
These ligaments areresponsible for dividing the
joint mediolaterally into
superior & inferior joint
cavities
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ANATOMY OF THE JOINT
Ligaments:
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
The capsular ligament is well innervated & providesthe proprioceptive feedback regarding the position& movement of the joint
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ANATOMY OF THE JOINT
Ligaments: The Lateral (Temporomandibular) Ligament:- It
reinforces & strengthens the lateral part of the
capsular ligament. Its fibers are directed downwards
& backwards. It is attached above to the auriculartubercle, & below to the posterolateral aspect of the
neck of the mandible
The oblique portion of the temporomandibular
ligament resists excessive dropping of the condyle,therefore limiting the extent of mouth opening
This portion of the ligament also influences the
normal opening movement of the mandible
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ANATOMY OF THE JOINT
Ligaments:
During the initial phase of opening, the condyle canrotate around a fixed point until the
temporomandibular ligament becomes tight as itspoint of insertion is on the neck of the condyle thatis rotated posteriorly
When the ligament is taut, the neck of the condylecannot rotate further
If the mouth were to be opened wider, the condylewould need to move downward & forward across thearticular eminence
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ANATOMY OF THE JOINT
Ligaments:
This unique feature of the temporomandibularligament, which limits the rotational opening, is
found only in humans The inner horizontal portion of the
temporomandibular ligament limits the posteriormovement of the condyle & the disc
When a displacing force is applied to the condyleposteriorly, this portion of the ligament becomestight & prevents the condyle from moving into theposterior region of the mandibular fossa
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ANATOMY OF THE JOINT
Ligaments:
The Sphenomandibular
Ligament:- It is an
accessory ligament, that
lies on a deep plane awayfrom the fibrous capsule. It
is attached superiorly to
the spine of the sphenoid,
& inferiorly to the lingula ofthe mandibular foramen. It
does not have any
significant limiting effects
on mandibular movement
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ANATOMY OF THE JOINT
Ligaments: The Stylomandibular ligament:- It is another
accessory ligament of the joint. It represents the
thickened part of the deep cervical fascia which
separates the parotid & the submandibular salivary
glands. It is attached above to the styloid process, &
below to the angle & posterior border of the ramus of
the mandible
It becomes taut when the mandible is protruded,
but is the most relaxed when the mandible isopened. Therefore the stylomandibular ligament
limits excessive protrusive movements of the
mandible
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ANATOMY OF THE JOINT
Relations Of The Temporomandibular J oint:
Anterior:-
Lateral pterygoid
Massetric nerve & vessels
Posterior:-
The parotid gland separates the joint from
the external auditory meatusSuperficial temporal vessels
Auriculotemporal nerve
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ANATOMY OF THE JOINT
Relations Of The Temporomandibular J oint:
Superior:-
Middle cranial fossa
Superior meningeal vessels
Inferior:-
Maxillary artery
Maxillary nerve
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ANATOMY OF THE JOINT
Nerve Supply:
The nerve supply to
the TMJ arises from
the mandibulardivision of the
trigeminal nerve
specifically the:
The deeptemporal
branchesNERVE SUPPLY OF TMJ
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ANATOMY OF THE JOINT
Blood supply:
The blood supply to the
TMJ is from 4 arteries:-
Branches from
the superficial
temporal artery
The deep
auricular artery
The anterior
tympanic artery
The ascending
pharyngeal artery ARTERIAL SUPPLY OF TMJ
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ANATOMY OF THE JOINT
Lymph Drainage:
It is to the pre-auricular nodes
The intraparotid nodes
The upper deep cervical nodes
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ANATOMY OF THE JOINT
Muscles responsible forthe movement of the
jaw:
Opening:- Lateralpterygoid & the
digastric muscles
Closing:- Masseter,
medial pterygoid &temporalis muscles
MUSCLES OF MASTICATION
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FUNCTIONAL ANATOMY OF THE
JOINT
MECHANISM OF MANDIBULAR MOVEMENTS
Mandibular movements occur as a complex series of
interrelated 3-dimensional rotational & transitional
activities
It is determined by the combined & simultaneous
activities of both TMJs
TMJs cannot function entirely independently of each
other & rarely function with identical concurrentmovements
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FUNCTIONAL ANATOMY OF THE JOINT
HORIZONTAL AXIS OFROTATION:
Mandibular movement
around the horizontal
axis is an opening &closing motion
It is referred to as a
hinge movement
The horizontal axisaround which it occurs
is there fore referred to
as the hinge axis
ROTATIONAL MOVEMENTAROUND THE HORIZONTAL
AXIS
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FUNCTIONAL ANATOMY OF THE
JOINT
HORIZONTAL AXIS OF ROTATION:
This axis runs horizontally from the right side of the
condyle to the left side
Hinge movement is probably the only example of the
mandibular activity in which purerotational
movement occurs
In all other movements rotation around the axis is
accompanied by translation of the axis
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FUNCTIONAL ANATOMY OF THE
JOINT
FRONTAL (VERTICAL) AXIS OF ROTATION:
When the condyles are in their most superior
position in the articular fossae & mouth is purely
rotated open, the axis around which the movementoccurs is called the terminal hinge axis
The vertical axis runs through the condyle & the
ramus of the mandible, & the mandible rotates
around this vertical axis during lateral movements
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FUNCTIONAL ANATOMY OF THE
JOINT
TRANSLATIONAL MOVEMENT
Translation can be defined as a movement in which
every point of the moving object has simultaneously
the same velocity & direction
In the masticatory system, translation occurs when
the mandible moves forward, as in protrusion
The teeth, condyles, & rami all move in the same
direction & to the same degree
FUNCTIONAL ANATOMY OF THE JOINT
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FUNCTIONAL ANATOMY OF THE JOINT
TRANSLATIONAL MOVEMENT
Translation occurs within thesuperior cavity of the joint,
between the superior surface of
the articular disc & the inferior
surface of the articular fossa During most normal movements
of the mandible, both rotation &
translation occur
simultaneously, i.e while themandible is rotating around one
or more of the axes, each of the
axes is translating (i.e changing
its orientation in space)
TRANSLATIONALMOVEMENT OF THE
MANDIBLE
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C O O O O
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FUNCTIONAL ANATOMY OF THE JOINT
The border & typical functional
movements of the mandible foreach reference plane: Sagittal plane border &
functional movements Mandibular motion viewed
in the sagittal plane can beseen to have 4 distinctmovement components:-
1. Posterior openingborder
2. Anterior openingborder
3. Superior contactborder
4. Functional
FUNCTIONAL &BORDER MOVEMENTSIN SAGITTAL PLANE
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FUNCTIONAL ANATOMY OF THE JOINT
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FUNCTIONAL ANATOMY OF THE JOINT
Posterior opening border
movements:
Posterior opening border
movements occur in the
sagittal plane as two-stage
hinging movements In the 1st stage the condyles are
stabilized in their most superior
positions in the articular fossae
(i.e terminal hinge position) The most superior condylar
position from which a hinge
axis movement can occur is the
centric relation (CR) position
ROTATIONAL MOVEMENT OFTHE MANDIBLE WITH THE
CONDYLES IN TERMINAL
HINGE POSITION
FUNCTIONAL ANATOMY OF THE
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FUNCTIONAL ANATOMY OF THE
JOINT
Posterior opening border movements:
The mandible can be lowered (i.e mouth opening) in
a pure rotational movement without translation of
the condyle Theoretically, a hinge movement (i.e pure rotation)
can be generated from any mandibular position
anterior to the centric relation
For this to occur the condyles must be stabilized sothat the translation of the horizontal axis does not
occur
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FUNCTIONAL ANATOMY OF THE JOINT
Posterior opening border movements: Since the stabilization of the condyles is difficult to
establish, posterior opening border movements that
use the terminal hinge axis are the only repeatable
hinge axis movement of the mandible In centric relation the mandible can be rotated
around the horizontal axis to a distance of only 20 to
25 mm, as measured between the incisal edges of
the maxillary & mandibular incisors
At this point of opening the temporomandibular
ligaments tighten, after which continued opening
results in an anterior & inferior translation of the
condyles
FUNCTIONAL ANATOMY OF THE JOINT
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FUNCTIONAL ANATOMY OF THE JOINT
Posterior opening border
movements: As the condyles translate
the axis of rotation of the
mandible shifts into the
bodies of the rami,resulting in the 2nd stage of
the posterior opening
border movements
The exact location of theaxis of rotation in the rami
is likely to be the area of
attachment of the
sphenomandibular
ligaments
2ND STAGE OF ROTATIONALMOVEMENT DURING
MOVEMENT
FUNCTIONAL ANATOMY OF THE
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FUNCTIONAL ANATOMY OF THE
JOINT
Posterior opening border movements:
During this stage in which the mandible is rotating
around a horizontal axis passing through the rami,
the condyles are moving anteriorly & inferiorly & theanterior portion if the mandible is moving posteriorly
& inferiorly
Maximum opening is achieved when the capsular
ligaments prevent the further movement of thecondyles
Maximum opening is in the range of 40 to 60 mm
when measured between the incisal edges of
maxillary & mandibular teeth
FUNCTIONAL ANATOMY OF THE JOINT
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FUNCTIONAL ANATOMY OF THE JOINT
Anterior opening border movements:
With the mandible maximally opened, closure
accompanied by contraction of inferior lateral
pterygoids, will generate the anterior opening border
movement
Theoretically, if the condyles were stabilized in this
anterior position, a pure hinge movement could
occur while the mandible was closing from the
maximally opened to the maximally protruded
position As the maximum protrusive movement is determined
in part by the stylomandibular ligament, when
closure occurs, tightening of the ligaments produces
a posterior movement of the condyles
FUNCTIONAL ANATOMY OF THE JOINT
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FUNCTIONAL ANATOMY OF THE JOINT
Anterior opening border
movements: Condylar position is the most
anterior in the maximally
open but not the maximally
protruded position The posterior movement of
the condyle from the
maximally open position to
the maximally protrudedposition produces
eccentricity in the anterior
border movement, therefore it
is not a pure hinge movement
ANTERIOR OPENINGBORDER MOVEMENT IN THE
SAGITTAL PLANE
FUNCTIONAL ANATOMY OF THE
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FUNCTIONAL ANATOMY OF THE
JOINT
Superior contact border movements:
The superior contact border movements are
determined by the characteristics of the occluding
surfaces of the teeth Throughout this entire movement the tooth contact
is present
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FUNCTIONAL ANATOMY OF THE JOINT
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FUNCTIONAL ANATOMY OF THE JOINT
Superior contact border movements:
As this border movement is totallytooth determined, changes in theteeth will result in changes in thenature of the border movement
In the centric relation position the,the tooth contacts are normallyfound on one or more opposingpairs of posterior teeth
The initial tooth contact is
terminal hinge closure, or centricrelation, occurs between themesial inclines of a maxillarytooth & the distal inclines of amandibular tooth
COMMONRELATIONSHIP OFTEETH WHEN THECONDYLES ARE INCENTRIC RELATION
POSITION
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Superior contact border movements:
If a muscular force is applied to themandible, a superoanterior
movement or shift will result until
the intercuspal position is reached
This centric relation to theintercuspal slide may have a lateral
component, & this slide is present
in approximately 90% of the
population, the average distance is
1.25+1 mm
In the intercuspal position the
opposing anterior teeth usually
contact
INTERCUSPALPOSITION ATTAINED
WHEN THE FORCE ISAPPLIED ON THE
MANDIBLE
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Superior contact bordermovements:
When the mandible is protruded
from maximum intercuspation,
contact between the incisal
edges of the mandibular teeth &
the lingual inclines of themaxillary teeth results in an
anteroinferior movement of the
mandible
This continues until themaxillary & the mandibular teeth
are in an edge to edge
relationship, at which time a
horizontal pathway is followed
ANTEROINFERIORMOVEMENT OF THE
MANDIBLE
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FUNCTIONAL ANATOMY OF THE JOINT
The occlusal contacts of the posterior teeth thendictate the remaining pathway to the maximum
protrusive movement, which joins with the most
superior position of the anterior opening border
movement
CONTINUED BORDERMOVEMENT OF THE
MANDIBLE
CONTINUED BORDERMOVEMENT OF THE
MANDIBLE
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FUNCTIONAL ANATOMY OF THE
JOINT
Superior contact border movements:
When a person has a discrepancy between thecentric relation & maximum intercuspation, the initial
description of the superior contact border movementis altered
From centric relation there is no superior slide tointercuspal position
The beginning protrusive movement immediately
engages the anterior teeth, & the mandible movesinferiorly, as detected by the lingual anatomy of themaxillary anterior teeth
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Functional movements:
Functional movements occur during the functional
activity of the mandible
They usually take place within the bordermovements & therefore are considered free
movements
Most functional activities require maximum
intercuspation & therefore begin at & below theintercuspal position
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FUNCTIONAL ANATOMY OF THE JOINT
Functional movements:
When the mandible is at rest it isfound to be 2 to 4 mm below the
intercuspal position, which has been
called the clinical rest position
It has also been determined that theso called clinical rest position is not
the position at which the muscles
have their least amount of
electromyographic activity
The muscles of mastication are at
their lowest level of activity when the
mandible is positioned approximately
8 mm inferior & 3 mm anterior to the
intercuspal position
POSTURAL POSITIONOF THE MANDIBLE
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FUNCTIONAL ANATOMY OF THE
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Functional movements:
At this point the force of gravity pulling the mandible
down is in equilibrium with the elasticity & resistance
to the stretching of the elevator muscles & other softtissues supporting the mandible
Thus, this position is best described as the clinicalrest position
As function cannot occur readily from this position,the myotactic reflex, which counteracts forces of
gravity & maintains the jaw in a more functionally
ready position 2 to 4 mm below the intercuspal
position, is activated
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Functional movements:
In this position the teeth can be quickly & effectively
brought together for immediate function
The increased levels of electromyographic muscleactivity in this position are indicative of the
myotactic reflex
As this is not a true resting position, the position in
which the mandible is maintained is moreappropriately termed the postural position
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Functional movements:
If the chewing stroke is
examined in the sagittal plane,
the movement will be seen to
begin at the intercuspal
position & drop downwards &slightly forward to the
position of the desired
opening
It then returns in a straighterpathway, slightly posterior to
the opening movementCHEWING STROKE
WITH BORDERMOVEMENT IN THESAGITTAL PLANE
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FUNCTIONAL ANATOMY OF THE JOINT
Functional movements:Postural effects of functional
movement-
When the head ispositioned erect & uprightthe postural position of themandible is located 2 to 4mm below the intercuspalposition
On contraction of theelevator muscles, themandible will be elevateddirectly into the intercuspalposition
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Functional movements:
Postural effects of functional
movement-
The normal head positionduring eating is with the
face directed downwards
30 degrees, this is referred
to as alert feeding position In it the mandible shifts
slightly anteriorly to the
upright postural position
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Functional movements:
Postural effects of functional movement-
If the elevator muscles contract with the head in this
position, the path of closure will be slightly anteriorto that in the upright position
Thus, the tooth contacts will occur anterior to the
maximum intercuspal position
Such an alteration in closure leads to heavy anteriortooth contacts
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Functional movements:
Postural effects of functional movement-
The 45-degree head position is the head posture
assumed during drinking
In this position the mandible is maintained more
posterior to maximum intercuspation
Thus, closure with the head back often results in
tooth contacts posterior to the intercuspal position
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HORIZONTAL PLANEBORDER & FUNCTIONALMOVEMENTS
Gothic arch tracers havebeen used to record the
mandibular movement in
the horizontal plane
It consists of a recordingplate attached to the
maxillary & mandibular
teeth
GOTHIC ARCH TRACER
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HORIZONTAL PLANE BORDER &
FUNCTIONAL MOVEMENTS Mandibular movements in the
horizontal plane can beviewed as a rhomboid-shapedpattern that has a functionalcomponent, as well as 4distinct movementcomponents
1. Left lateral border
2. Continued left lateralborder with protrusion
3. Right lateral border
4. Continued right lateral
border with protrusion
MANDIBUALR BORDERMOVEMENTS IN THEHORIZONTAL PLANE
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HORIZONTAL PLANE BORDER& FUNCTIONAL MOVEMENTSLeft lateral border movements:
With the condyles in centricrelation position, contraction
of the right inferior lateralpterygoid will cause the rightcondyle to move anteriorly &medially (also inferiorly)
Simultaneously if the leftinferior lateral pterygoidremains relaxed, the leftcondyle will remain situated incentric relation & the resultwill be a left lateral bordermovement
LEFT LATERAL BORDERMOVEMENT IN
HORIZONTAL PLANE
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HORIZONTAL PLANE BORDER & FUNCTIONALMOVEMENTS
Left lateral border movements:
Therefore the left condyle is called the rotatingcondyle as the mandible is rotating around it, the leftcondyle is also called the working condyle as it is onthe working side
The right condyle is called the orbiting condyle as it
is orbiting around the rotating condyle, the rightcondyle is also called the nonworking condyle as itis on the nonworking side
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HORIZONTAL PLANE BORDER &
FUNCTIONAL MOVEMENTSContinued left lateral border movements:
With the mandible in the left lateral
border position, contraction of the left
inferior lateral pterygoid along with
continued contraction of the rightlateral pterygoid muscle will cause the
left condyle to move anteriorly & to the
right
As the right condyle is already in its
maximal anterior position, themovement of the left condyle to its
maximum anterior position will cause a
shift in the mandibular midline back to
coincide with the midline of the face
CONTINED LEFTLATERAL BORDER
MOVEMENT
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HORIZONTAL PLANE BORDER &
FUNCTIONAL MOVEMENTSRight lateral border movements:
Contracting of the left inferiorlateral pterygoid muscle will causethe left condyle to move anteriorly& medially (also inferiorly)
If the right inferior lateralpterygoid muscle stays relaxed,the right condyle will remainsituated in centric relationposition
The resultant mandibularmovement will be a right lateralborder movement (e.g., the leftcondyle rotating around the thefrontal axis of the right condyle)
RIGHT LATERAL BORDERMOVEMENT
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HORIZONTAL PLANE BORDER &
FUNCTIONAL MOVEMENTSContinued right lateral border
movements with protrusion:
With the mandible in the rightlateral border position, contractionof the right inferior lateral
pterygoid muscle along withcontinued contraction of the leftinferior lateral pterygoid will causethe right condyle to moveanteriorly & to the left
As the left condyle is already in its
maximum anterior position, themovement of the right condyle toits maximum anterior position willcause a shift back in themandibular midline to coincidewith the midline of the face
CONTINUED RIGHTLATERAL BORDER
MOVEMENT
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HORIZONTAL PLANE BORDER &
FUNCTIONAL MOVEMENTSContinued right lateral border
movements with protrusion:
This completes the mandibular border
movement in the horizontal plane
Lateral movements can be generated
by varying levels of mandibular
opening
The border movement generated with
each increasing degree of opening will
result in increasingly smaller tracing
until, at the maximally opening
position, little or no lateral movements
can be made
MANDIBULAR BORDERMOVEMENTS AT
VARIOUS DEGREES OFJ AW SEPARATION
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HORIZONTAL PLANE BORDER &FUNCTIONAL MOVEMENTS
Functional movements:
As in the sagittal plane, functionalmovements in the horizontal plane
most often occur near theintercuspal position
During chewing the range of jawmovements begin some distancefrom the maximum intercuspalposition, however, as the food is
broken down into smaller particlesizes jaw action moves closer &closer to the intercuspal position
The exact position of the mandibleduring chewing is dictated by theexisting occlusal configuration
FUNCTIONAL RANGEWITHIN THEHORIZONTAL
BORDERMOVEMENTS
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FRONTAL (VERTICAL) BORDER &
FUNCTIONAL MOVEMENTS When the mandibular motion is
viewed in the frontal plane, ashield-shaped pattern can beseen that has a functional
component as well as 4 distinctmovement components
1. Left lateral superior border
2. Left lateral opening border
3. Right lateral superior border4. Right lateral opening border
movements
MANDIBUALR BORDERMOVEMENTS IN THE
FRONTAL PLANE
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U C O O O
JOINT
FRONTAL (VERTICAL) BORDER & FUNCTIONALMOVEMENTS
Left lateral superior border movements:
With the mandible in maximum intercuspation, alateral movement is made to the left
An inferiorly concave path is generated, the precise
nature of this path is determined by the morphology
& interarch relationships of the maxillary &mandibular teeth that are in contact during this
movement
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FRONTAL (VERTICAL)
BORDER & FUNCTIONALMOVEMENTSLeft lateral opening border
movements:
From the left lateral superior
border position, an openingmovement of the mandibleproduces a laterally convexpath
As the maximum opening isapproached the ligamentstighten & produce a mediallydirected movement thatcauses a shift back in themandibular midline tocoincide with the midline of
the face
LEFT LATERAL OPENINGBORDER MOVEMENTS
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FRONTAL (VERTICAL)
BORDER & FUNCTIONALMOVEMENTS
Right lateral superior
border movements:
From the maximumintercuspation position a
lateral movement is made
to the right that is similar
to the left lateral superiorborder movement
Slight differences may
occur because of the
tooth contacts involved
RIGHT LATERAL SUPERIORBORDER MOVEMENTS
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FRONTAL (VERTICAL) BORDER
& FUNCTIONAL MOVEMENTSRight lateral opening bordermovements:
From the maximum right lateralborder position, an opening
movement of the mandibleproduces a laterally convexpath similar to that of the leftopening movement
As maximum opening isapproached, ligaments tighten& produce a medially directedmovement that causes a shiftback in the mandibular midlineof the face to end this leftopening movement
RIGHT LATERALOPENING BORDER
MOVEMENT
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FRONTAL (VERTICAL)
BORDER & FUNCTIONALMOVEMENTS
Functional movements:
As in the other planes,
functional movements inthe frontal plane begin &
end at the intercuspal
position
During chewing themandible drops directly
inferiorly until the desired
opening is achieved
FUNCTIONALMOVEMENT WITHINTHE MANDIBULAR
BORDER MOVEMENTIN FRONTAL PLANE
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ENVELOP OF MOTION
When we combine the
border movements of all
the 3 planes (i.e sagittal,
horizontal & frontal) a
three- dimensional envelop
of motion can be produced
that represents the
maximum rage of
movements of themandible
It was 1st described by
Posselt in 1952MODEL OF ENVELOP
OF MOTOIN
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ENVELOP OF MOTION The envelop of motion
is longest & widest
superiorly & narrows
down to a point nearthe maximum mouth
opening position
Hence, as the jaw
separation increases,
space for movement
decreases to zero at the
maximum mouth
opening position
COMBINATION OFMOVEMENTS IN ALL THE
THREE PLANES
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