Anatomy of TMJ - Copy

7/29/2019 Anatomy of TMJ - Copy

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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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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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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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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 J OINT (LATERALVIEW)


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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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Ligaments:

There are two accessory ligaments:-

The sphenomandibular ligament

The Stylomandibular ligament


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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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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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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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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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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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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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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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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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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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Relations Of The Temporomandibular J oint:

Superior:-

Middle cranial fossa

Superior meningeal vessels

Inferior:-

Maxillary artery

Maxillary nerve


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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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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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Lymph Drainage:

It is to the pre-auricular nodes

The intraparotid nodes

The upper deep cervical nodes


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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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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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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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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



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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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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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Posterior opening border

movements:


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



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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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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



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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



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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



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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



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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



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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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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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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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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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JOINT


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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JOINT

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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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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JOINT


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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JOINT


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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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 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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JOINT


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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JOINT


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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JOINT


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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JOINT

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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JOINT

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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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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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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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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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


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


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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Documents

Anatomy of TMJ - Copy