growth and dev tmj
TRANSCRIPT
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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&le% 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