Growth and Dev TMJ

7/23/2019 Growth and Dev TMJ

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GROWTH AND DEVELOPMENT OFTEMPOROMANDIBULAR JOINT


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CONTENTS

Introduction

Evolution of TMJEmbryology

Growth and Development

Age changes

Histology

unctional Anatomy and !iomechanics

Movements of TMJ

TMJ disorders

"ummary and #onclusion

$eferences


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INTRODUCTION


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Evolution of TMJ

The agnatha% the earliest type of vertebrae% had its

mouth opening on the ventral side anteriorly along thevertebral a&is' This opening led through an

oropharyngeal channel to the gut proper' "lits that

opened to the outside functioned both for respiration

and food filtration% and were moved simultaneously incooperation with the mouth by a series of cartilages

called gill arches'

A GI(( A$#H had an internal bend and the turningpoint of this bend was a synarthosis% which was

considered to be the earliest form of a )aw )oint' This

structure remains as an epiceratobranchial )oint in the

present day shar*'


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GNATHOSTOMES

+,st

and -nd

arches disappeared into the s*ull'+.rd and /th arch0s began to function in the prey capture1 the

apparatus of )aw

As evolution proceeded2

+A more highly developed moveable )aw )oint appeared in

3"TEI#H4TE"

+ormed by gill arches% the cartilagenous )aw was covered bysecond )aws'

+Teeth developed in the bony plates around the mouth'

+Amphibians


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In amphibians 5 had a dentary in the anterior end of original

cartilagenous )aw'

At posterior end it articulated with the 6uadrate bone% a structure of

ma&illa'Mammal li*e reptilia

E&1 Aligator

Is composed of a number of bony segments% of which only the

dentary is retained in the human mandible'

Two of these segment% 6uadrate and articulate both derived from

Mec*el0s cartilage 7,stbranchial arch8 constitue the non+mammalian

)aw )oint i'e' 9$IMA$4 J3I:T 3$ ;


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Associated with the formation of ear ossicles% a new )aw )oint

TMJ made its first appearance in mammals'

"econdary )oint = "6uamosodentary )oint

>As it is present between s6uamous part of temporal bone and the

mandible 7dentary8?'

+3ne can imagine this evolutionary transmission occurring bymeans of a bony process which appeared on the mandibular

anterior to 6uadratoarticular )oint which at one time became

large enough to contact the s*ull'

Difference inMammalian )aw+)oint :on mammalian )aw+)oint

A8 #onve& )oint surface #oncave

!8 Intra+articular dis* Absent


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EMBRYOLOGY

+Develops late in embryonic life'

+#ompared with large )oints of e&tremities'

+Associated with its late evolutionary development'

+During the @thprenatal wee*% the )aw )oint lac*s1

+#ondylar growth cartilage'

+Joint cavities'

+"ynovial tissues

+Articular capsule'

- s*eletal elements 1 mandible and temporal bone are not yet

in contact with each other'


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@ wee* old embryo

+Mec*el0s cartilage e&tends all the way from chin to base of the

s*ull'

+"erves as a scaffolding or strutt against which the mandible

develops'

+9rovides a temporary articulation between mandible and base of

the s*ull until TMJ ta*es over'

+:ear end of fetal life Mec*el0s cartilage completes its

transformation1

+Incus

+Malleus+Anterior ligament of malleus

+"phenomandibular ligament

Mec*el0s cartilage plays an a basic role in setting the evolutionary

stage for the emergence of this )oint'


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Ati!ul" Di#!$

+Earliest appearance in wee* old embryo'

+Muscular derivative of ,stbranchial arch'+Disc analge+ vague layer of mesenchyme stretching across upper

end of mandibular ramus'

+:o capsule'

+:o condyle'

+At its anterior end% mesenchymal analge e&tends laterally from

superior border of (9M% to medial side of masseter muscle'

+At the end of thwee*% lateral pterygoid inserts not on the

mandibular but on the posterior end of Mec*el0s cartilage'

+During @thwee* 5 7(9M8 )oins upper end of mandibular ramus2

also continues posteriorly beyond this point with mesenchyme

analge des abv2 these - structures insert in common part of

Mec*el0s cartilage which becomes the malleus'


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At @ wee*s1 the future condyle is still only a condensation of

mesenchyme resting on osseous lamella% which forms the mandibular

ramus'

,- wee* 5 condylar growth cartilage ma*es its ,stappearance and

begins to develop a hemi+spherical articular surface'

!y ,.thwee* 5 condyle and articular disc having moved up into

contact with temporal bone'

3nly when such articular contact has been made do the )oint cavities

develop'

Inferior space appearing first'Disc begins to get compressed'

Bhen central portion of disc is compressed this part becomes

avascular'


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T%& "ti!ul" !"'#ul&$

+!ecomes recogniCable during twelth wee* as a faint cellular

condensation along the medial and lateral sides of )oint connectingmandible with temporal bone'

+Articular disc merges peripherally with these condensations'

+ormation of capsule posterior to )oint does not occur until

twenty+second wee*2 when the Glaserian fissure2 becomes narrow2encroaching upon Mec*el0s 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 G'

+Joint cavities are now lined by synovial tissue and according to

"ymons 7,-8% temporal bone now shows area of secondary

cartilage in medial part of the )oint'


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By 26thweek:

All components of TMJ present e&cept articular eminence'

Mec*el0s cartilage still e&tends through G% but by thirty+first wee*

is transformed into sphenomandibular ligament'

By 39thweek:

3ssification of bones in this region has proceeded to the pointwhere2 ligament gains its apparent attachment to spine of sphenoid'


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HISTOLOGY OF TMJ

#omposed of / distinct layers1+Articular'

+9roliferative'

+ibrocartilagenous'

+#alcified cartilage'


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The growth of face and cranium involves two basic types of growth

changes1

,8 Displacement

-8 $emodelling

+ !oth these process% together constitute the growth mechanism of

craniofacial s*eleton'

+ 3ne of the most familiar phrases in facial biology is that theface grows downwards and forwards'

+ As mandibular moves forward and downward% it grows upward

and bac*ward at the same time by an e6ual amount'

+ The process of mandibular growth is comple&2 does not merely

involves condylar growth to accomplish these changes'

+ About half of the periosteal surfaces of bone 7mand8 have fields

that are characteristically resorptive in character and about half


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+or e&ample% 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 amountof posterior bone deposition e&ceeds the amount of anterior

resorption on the various surfaces'

+As the ramus grows posteriorly% the mandibular condyle grows

upward and bac*ward by an endochondral mode of bone

formation% in contrast to intermembranous manner of growth in

other parts of the ramus'

+The bone located where the condyle used to be during past growth

stages is remodelled% successively into mandibular nec* and a part

of the ramus'

+The endosteal surface of the mandibular nec*% rather than the

outersurface% is oriented so that it faces the upward and bac*ward

of condylar growth'


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The condyle as a ma)or growth site1

+The condyle has been singled out as a special site 7centre8 because

it has a distinctive growth cartilage% which provides certain special

function during growth'

+The posterior and superior manner of growth of mandibular ramus

re6uired an endochondral type of bone formation at its condylar

)unction with the cranial floor because of the surface compressioninvolved'

+#artilage 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 s*ull'

+The upward and bac*ward growth of the condyle has a resultant

push effect against the basicranium% with a subse6uent displacement

of the entire mandibular downward and forward' 7#ondylar thrust

concept8'

TMJ in the first decade of life1


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TMJ in the first decade of life1

+At birth% the mandible as a whole continues the e&uberant% but

progressively diminishing period of overall growth that was begun

during the last trimester in utero'

+During the first year of life the condyle 1 vasculariCation% entire

growth cartilage layer becomes significantly thinner' This continues

upto the third year'

+Temporal component1

+Morphologic changes ta*e place from birth to the end of mi&ed

dentition by F months1 Enlargement of articular eminence and post

glenoid region'

+During this time tympano+s6uamosal tissue begins to close as the

postglenoid process becomes fused with the tympanic plate'

+!y - years the articular eminence increase from - to /mm' 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 "0 shape curve'


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The process continues so that by +@ years the articular eminence

enlarges to +mm in height'

!y appro&imately +@ years of age

Articular layer of condyle becomes thic*er

#artilage layer becomes thinner 5 '.mm


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TMJ in (n)"n) *))&!")&$

#haracteriCed by progressive slowing of growth process'

!y ,.+, years decreased thic*ness of cartilage layer'

9resence of proliferative layer atleast till age of ,F years'

A cortical bone cap coalescing with subchondral trabecular bone

by ,+,- years of age' This increases in thic*ness upto .rd

decade of life'

!one cap is completed by - years of age although cartilage and

sparse cartilage cells remain'


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ADULT TMJ

#artilage completely replaced by the bone around the beginning of

/thdecade'

Articular tissue1 $elatively unchanged 5 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 mar*s the end of active growth of the condyle'

In older adult temporal fossa1 less pronounced chondroid layer'

Articular eminence 1 is made of chondroid bone'


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FUNCTIONAL ANATOMY

(1) Bony components

+#ondylar head

+Glenoid fossa

+Articular eminence

(2) Msc!es

,8 Muscles involved

in mastication'

-8 acial muscles'

.8 Muscles of the

nec*

(3) "o#t t$sse

+Articular disc

+Joint capsule

+(igaments

+Muscles attached to

)oint

(%) &'te'$! "pp!y

() Ne'*e spp!y

(6) +ympht$c ,'$n-e


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BIOMECHANICS OF TMJ


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BIOMECHANICS OF TMJ

+ #omple& )oint system'

+ #ompound )oint 5 Its structure and function can be dividedinto - distinct system1

i8 #ondyle disc comple&'

ii8 #ondyle disc comple& and articulating surface of mandibular

fossa'

+ #onstant contact between )oint surfaces for stability is

re6uired'

+ Disc space more at rest% decreases with an increase in pressureof the )oint'

+ $etrodiscal lamina

+ (ateral pterygoid'


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Movement involving the )oints has beenMovement involving the )oints has beendivided different phasesdivided different phases

K 3cclusal or rest position3cclusal or rest position

K $etruded opening phase or rotation$etruded opening phase or rotationK Early protrusive opening phase or functionalEarly protrusive opening phase or functional

openingopening

K (ate protrusive opening phase or translation(ate protrusive opening phase or translationK Early closing phaseEarly closing phase

K $etrusive closing phase$etrusive closing phase

3##(


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3##(


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$ET$


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9HA"E 3$


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9HA"E9HA"E

3$ T$A:"(ATI3:3$ T$A:"(ATI3:

The condyle moves inferiorly and anteriorly beneath the

anterior band i.e there is full

openin more, space develops

in the superior compartment

The upper and lower head of

"ateral pteryoid contract to uide the disk and the condyle fully

forward

The posterior connective tissues tihtens

EA$(4 #(3"I:G 9HA"EEA$(4 #(3"I:G 9HA"E


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EA$(4 #(3"I:G 9HA"EEA$(4 #(3"I:G 9HA"E

The condyle translates posteriorly, about 6 to

! mm, to the intermediate zone

There is simultaneous reduction of space

posteriorly in the superior compartment


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$ET$


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Cl"##ifi!"tion$

1) .'owth ,$so',e's n, the /o$nt

a8 Developmental disorders'

b8 Ac6uired disorders'c8 :eoplastic disorders'

2) Mst$cto'y msc!e ,$so',e's:

a8 9rotective muscle splinting'

b8 Muscle hyperactivity or spasm'

c8 Myositis 7muscle inflammation8'

3) D$sk $nte'#e'ence ,$so',e's ($nte'n! ,e'n-ement)

a8 Incoordination'

b8 Deformation of articular dis*'

c8 9artial anterior dis* displacement'

d8 Anterior dis* displacement with reduction'

e8 Anterior dis* displacement without reduction'

f8 Anterior dis* displacement with perforation'9osterior dis* dis lacement'

/8 9roblems that result from e&trinsic trauma1


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/8 9roblems that result from e&trinsic trauma1

a8 Tendonitis'

b8 Myositis'

c8 Traumatic arthritis'd8 Dislocations'

e8 racture'

f8 Internal derangements'

8 Degenerative )oint disease1

a8 Arthrosis 7non+inflammatory phase8'

b8 3steoarthritis 7inflammatory phase8'

c8 3steochondritis disecans'

@8 #hronic mandibular hypomobility1

a8 An*ylosis'

b8 ibrosis'

c8 #ontracture of elevator muscle'

8 Inflammatory )oint disorders1

K "ynovitis and capsulitis

K $etrodis*itis'

K Inflammatory arthritis

F8 9ost surgical problems


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Diseases affecting the TMJ are primarily inflammatory and

degenerative% while developmental% metabolic and neoplasticconditions are rare occurrences'

D&v&lo'+&nt"l "no+"li$

+#ongenital

Genetic = 9renatal = 9ostnatal

Trauma

:utritional deficiencies etc'

Ac6uired

# d l i


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#ondylar agenesis

+Is fre6uently associated with various symptoms'

+if unilateral pronounced facial asymmetry under developedmandible leads to distortion and depression of that side of the

face'

+Macrostomia'

+Absence of e&ternal ear'

+Alterations in dental occlusion'

+!ilateral condylar agenesis may present with symmetrical

severe underdevelopment of the mandible'


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Con),l" H,'o'l"#i"

+More fre6uent

+#auses1 infection and trauma

+#=1 acial deformity

+(imitation of lateral e&cursion'

+"hift of mandibular midline during opening of mouth'

Do0!e mn,$0!' con,y!e:

Etiology% embryologic% traumaticLLL''

+


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Con),l" %,'o'l"#i"$

#auses1

Infection

Trauma

#linical features

+"ymmetric enlargement of entire condylar process'

+(imited movements'+In adults lateral displacement and open bite'

AN-YLOSIS


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AN-YLOSIS

Defined as chronic hypomobility or immobility of a usually

moveable articulating surface'#auses1

+ Infection% trauma'

#lassification1

,'


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D&.&n&"tiv& Joint Di#&"#$

+3steoarthritis'

+:on inflammatory process caused by local disease involvingone particular )oint'

+Etiology is multifactorial1 systemic factors% mechanical stress%

trauma'

+3ther factors1 tooth loss% 3cclusal interferences% E&cessive

forces of muscles in bru&ism'

#=1 #repitation% unilateral pain% feeling of stiffness after a

period of inactivity'

Treatment1 :"AID"% heat% soft diet% occlusal splints%

intraarticular steroids% arthroplasty'


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M9D"1 Is a pain referred from a localiCed tender area% a trigger

point% in a taut band of s*eletal muscle% including muscles of

mastication'(as*in stated that TMJ pain dysfunction syndrome is a misnomer

because the diorder was primarily related to masticatory muscle

spasm'

"igns and symptoms1


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T&"t+&nt$

Treatment of emotional and physical components'

$eviewing history of patients problems'

9lacebo drugs% splints or occlusal e6uilibration patient

reassurance'

"pray and stretch 1 fluoromethane refrigerant spray'

In)ection (A at trigger point'

"oft diet'

:"AIDs

Discontinuing parafunctional habits'

3cclusal splintLL'


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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 )oint'

In order to understand fully the nature of this )oint% onemust begin with its evolutionary history% for its popular

evolution e&plained its astonishing embryological

development% from which comes its uni6ue gross and

histologic structure% all of this reaching final clinical

significance in the various functional and morphologic

disorders seen in this )oint'


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Thank You

Growth and Dev TMJ

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