Pre natal and post natal growth of mandible and tmj

GROWTH ANDGROWTH AND
DEVELOPMENT OFDEVELOPMENT OF
MANDIBLE AND TMJMANDIBLE AND TMJ
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CONTENTS:CONTENTS:
1.1. IntroductionIntroduction
2.2. AnatomyAnatomy
3.3. Pre natal growth of mandiblePre natal growth of mandible
A) Formation of fronto-nasal processA) Formation of fronto-nasal process
B) Formation of pharyngeal archB) Formation of pharyngeal arch
C) Role of meckle’s cartilage inC) Role of meckle’s cartilage in
mandibular growthmandibular growth
D) Role of secondary accessoryD) Role of secondary accessory
cartilagecartilage

D) Role of secondary accessory cartilageD) Role of secondary accessory cartilage
A) Growth In mental regionA) Growth In mental region
B) Growth in coronoid regionB) Growth in coronoid region
C) Growth in condylar regionC) Growth in condylar region
4)4) Pre natal growth of TMJPre natal growth of TMJ
5)5) Post natal growth of mandiblePost natal growth of mandible
6)6) Amount and directions of mandibular growthAmount and directions of mandibular growth
7)7) Growth relation to the maxillaGrowth relation to the maxilla
8)8) Post natal growth of TMJPost natal growth of TMJ
9)9) Theories of mandibular growthTheories of mandibular growth
10)10) Growth patternGrowth pattern

11)11) Factor influencing mandibular growthFactor influencing mandibular growth
12)12) ConclusionConclusion
13)13) ReferencesReferences

INTRODUCTION:INTRODUCTION:
The human mandible has no one designThe human mandible has no one design
for life. Rather, it adapts and remodelsfor life. Rather, it adapts and remodels
through the seven stages of life, from thethrough the seven stages of life, from the
slim arbiter of things to come in the infant,slim arbiter of things to come in the infant,
through a powerful dentate machine andthrough a powerful dentate machine and
even weapon in the full flesh of maturity,even weapon in the full flesh of maturity,
to the pencil-thin, porcelin like problemto the pencil-thin, porcelin like problem
that we struggle to repair in the adversitythat we struggle to repair in the adversity
of old age.of old age.
D.E.POSWILLO,1988D.E.POSWILLO,1988

2) ANATOMY OF MANDIBLE2) ANATOMY OF MANDIBLE

Muscles attachment of mandibleMuscles attachment of mandible

Medial aspect of mandibleMedial aspect of mandible

ANATOMY OF TMJANATOMY OF TMJ

3.PRE NATAL GROWTH OF3.PRE NATAL GROWTH OF
MANDIBLEMANDIBLE
A)Formation of fronto-nasalA)Formation of fronto-nasal
processprocess

A)Formation of fronto-nasal processA)Formation of fronto-nasal process

C)Formation of PharyngealC)Formation of Pharyngeal
ArchesArches

B)Formation of maxillary andB)Formation of maxillary and
mandibular processmandibular process

Pre natal development of mandiblePre natal development of mandible
 The first structure to develop in the regionThe first structure to develop in the region
of mandible is the mandibular division ofof mandible is the mandibular division of
thethe TRIGEMINAL NERVETRIGEMINAL NERVE that precedesthat precedes
the ecto mesenchymal condensationthe ecto mesenchymal condensation
forming the first (mandibular arch) .forming the first (mandibular arch) .
 The prior presence of the nerve has beenThe prior presence of the nerve has been
postulated as requisite for inducingpostulated as requisite for inducing
osteogenesis by the production ofosteogenesis by the production of NEURONEURO
TROPHIC factors .TROPHIC factors .

 The mandible is derived from ossificationThe mandible is derived from ossification
of an osteogenic membrane formed fromof an osteogenic membrane formed from
ecto mesenchymal condensation at 36 toecto mesenchymal condensation at 36 to
38 days of development .38 days of development .
 This mandibular ecto mesenchyme mustThis mandibular ecto mesenchyme must
interact initially with the epithelium of theinteract initially with the epithelium of the
mandibular arch before primarymandibular arch before primary
ossification can occur.ossification can occur.
 The resulting intra membranous bone liesThe resulting intra membranous bone lies
lateral to meckle’s cartilage .lateral to meckle’s cartilage .

 A single ossification centre for each half ofA single ossification centre for each half of
the mandible arises in the 6the mandible arises in the 6thth
week postweek post
conception in the region of the bifurcationconception in the region of the bifurcation
of the inferior alveolar nerve and arteryof the inferior alveolar nerve and artery
into mental and incisive branches .into mental and incisive branches .
 The ossification membrane is lateral toThe ossification membrane is lateral to
MECKEL’S CARTILAGEMECKEL’S CARTILAGE and itsand its
accompanying neuro vascular bundle .accompanying neuro vascular bundle .
 From this primary centre below andFrom this primary centre below and
around, ossification spreads upwards toaround, ossification spreads upwards to
form a trough for the developing teeth .form a trough for the developing teeth .

 The spread of the intra membranousThe spread of the intra membranous
ossification dorsally and ventrally formsossification dorsally and ventrally forms
the body and ramus of the mandible .the body and ramus of the mandible .

MECKEL’S CARTILAGE becomesMECKEL’S CARTILAGE becomes
surrounded and invaded by bone .surrounded and invaded by bone .

 Ossification stops dorsally at the site thatOssification stops dorsally at the site that
will become the mandibular lingula, wherewill become the mandibular lingula, where
meckle’s cartilage continues into themeckle’s cartilage continues into the
middle ear.middle ear.

The prior presence of the neuro vascularThe prior presence of the neuro vascular
bundle ensures the formation ofbundle ensures the formation of
mandibular foramen and canal and themandibular foramen and canal and the
mental foramen .mental foramen .

Role of meckel’s cartilageRole of meckel’s cartilage

 Meckel’s cartilage lacks the enzymeMeckel’s cartilage lacks the enzyme
PHOSPHOTASEPHOSPHOTASE in ossifying cartilages,in ossifying cartilages,
thus precluding its ossification .thus precluding its ossification .
 Almost all of meckel’s cartilage disappearsAlmost all of meckel’s cartilage disappears
by the 24by the 24thth
week after conception .week after conception .
 Parts transform intoParts transform into
1)sphenomandibular ligament1)sphenomandibular ligament
2)anterior malleolar ligaments2)anterior malleolar ligaments
 A small part of its ventral end formsA small part of its ventral end forms
accessory endocondral ossicles that areaccessory endocondral ossicles that are
incorporated to the chin region of theincorporated to the chin region of the
mandible .mandible .

 Meckel’s cartilage dorsal to the mentalMeckel’s cartilage dorsal to the mental
foramen undergoes resorption on itsforamen undergoes resorption on its
lateral surface at the same time as intralateral surface at the same time as intra
membranous bony trabaculae are formingmembranous bony trabaculae are forming
immediately lateral to the resorbingimmediately lateral to the resorbing
cartilage .cartilage .
 Thus, the cartilage from the mentalThus, the cartilage from the mental
foramen to the lingula is not incorporatedforamen to the lingula is not incorporated
into ossification of the mandible .into ossification of the mandible .

 The initial woven bone formed alongThe initial woven bone formed along
meckle’s cartilage is soon replaced bymeckle’s cartilage is soon replaced by
lamellar bone, and typical harvesianlamellar bone, and typical harvesian
systems are already present at the 5systems are already present at the 5thth
month post conception .month post conception .

Role of Secondary AccessoryRole of Secondary Accessory
CartilageCartilage
Secondary accessory cartilage appearsSecondary accessory cartilage appears
between 10between 10thth
and 14and 14thth
week postweek post
conception to form the head of theconception to form the head of the
condyle, parts of the coronoid process,condyle, parts of the coronoid process,
and the mental protruberance .and the mental protruberance .
The appearance of these secondaryThe appearance of these secondary
mandibular cartilage is dissociated frommandibular cartilage is dissociated from
the primary pharyngeal(meckle’s cartilage)the primary pharyngeal(meckle’s cartilage)
and chondrocranial cartilage .and chondrocranial cartilage .

A.CORONOID PROCESSA.CORONOID PROCESS
The secondary cartilage of the coronoidThe secondary cartilage of the coronoid
process develops within theprocess develops within the
TEMPORALIS MUSCLE,TEMPORALIS MUSCLE, as itsas its
predecessor.predecessor.
The coronoid accessory cartilageThe coronoid accessory cartilage
becomes incorporated into the expandingbecomes incorporated into the expanding
intramembranous bone of the ramus andintramembranous bone of the ramus and
disappears before birth .disappears before birth .www.indiandentalacademy.comwww.indiandentalacademy.com

B)MENTAL REGIONB)MENTAL REGION
In mental region on either side of theIn mental region on either side of the
symphysis, one or two small cartilagesymphysis, one or two small cartilage
appear and ossify in the 7appear and ossify in the 7thth
month postmonth post
conception to form a variable number ofconception to form a variable number of
mental ossicles in the fibrous tissue of themental ossicles in the fibrous tissue of the
symphysis .symphysis .
The ossicles become incorporated into theThe ossicles become incorporated into the
membranous bone when the symphysismembranous bone when the symphysis
menti is converted from a syndesmosismenti is converted from a syndesmosis
into a synostosis during the 1into a synostosis during the 1stst
post natalpost natal
life .life .

C)CONDYLAR REGIONC)CONDYLAR REGION
The condylar secondary cartilage appearsThe condylar secondary cartilage appears
during the 10during the 10thth
week post conception as aweek post conception as a
cone-shaped structure in the ramal region.cone-shaped structure in the ramal region.
This condylar cartilage is the primordiumThis condylar cartilage is the primordium
of the future condyle.of the future condyle.
By the 14By the 14thth
week, the first evidence ofweek, the first evidence of
endochondral bone appears in theendochondral bone appears in the
condyle region .condyle region .
The condylar cartilage serve as anThe condylar cartilage serve as an
important center of growth for the ramusimportant center of growth for the ramus
and body of the mandible .and body of the mandible .

Nature of growth of condylar cartilageNature of growth of condylar cartilage
Its nature of growthIts nature of growth
1)1)primaryprimary (an initial source of morphogenesis)(an initial source of morphogenesis)
2)2)secondarysecondary (compensation for functional(compensation for functional
stimulation)stimulation)
Is contoversial, but experimental evidenceIs contoversial, but experimental evidence
indicate the need for mechanical stimuli forindicate the need for mechanical stimuli for
normal growth.normal growth.
By the middle of fetal life, much of the coneBy the middle of fetal life, much of the cone
shaped cartilage is replaced with bone, but itsshaped cartilage is replaced with bone, but its
upper end persists into adulthood acting asupper end persists into adulthood acting as
both growth and articular cartilage.both growth and articular cartilage.www.indiandentalacademy.comwww.indiandentalacademy.com

EVOLUTION OF THEEVOLUTION OF THE
MAMMALIAN JAW JOINTMAMMALIAN JAW JOINT

Evolution of TMJEvolution of TMJ

CLASSIFICATION OF JOINTSCLASSIFICATION OF JOINTS
TENCATETENCATE classifies joint intoclassifies joint into
1)Fibrous joint1)Fibrous joint
2)Cartilagenous joint2)Cartilagenous joint
3)Synovial joint3)Synovial joint

PRE NATAL GROWTH OF TMJPRE NATAL GROWTH OF TMJ
The TMJ is a secondary development inThe TMJ is a secondary development in
both evolution and embryological history.both evolution and embryological history.
The primitive joint within meckle’s cartilageThe primitive joint within meckle’s cartilage
(before the malleus and incus form)(before the malleus and incus form)
functions briefly as a jaw joint , mouthfunctions briefly as a jaw joint , mouth
opening movements having started at 8opening movements having started at 8
weeks post conception, well before theweeks post conception, well before the
development of TMJ .development of TMJ .
When the TMJ forms at 10 weeks, bothWhen the TMJ forms at 10 weeks, both
the incudomalleal and definitive jaw jointthe incudomalleal and definitive jaw joint
move in synchrony , for about 8 weeks inmove in synchrony , for about 8 weeks in
fetal life.fetal life.

Most of the synovial joints complete theirMost of the synovial joints complete their
development by 7development by 7thth
week post conception,week post conception,
but TMJ does not start to appear until thisbut TMJ does not start to appear until this
time.time.
The limb joints develop directly into theirThe limb joints develop directly into their
adult form by cavity formation within theadult form by cavity formation within the
single blastemea from which bothsingle blastemea from which both
adjoining endocondral bones develops .adjoining endocondral bones develops .

The TMJ develops from initially widelyThe TMJ develops from initially widely
seperated temporal and condylarseperated temporal and condylar
blastemata that grow towards each other.blastemata that grow towards each other.
TheThe temporal blastematemporal blastema arises from thearises from the
otic capsule, a component of theotic capsule, a component of the
basicranium that forms the petrousbasicranium that forms the petrous
temporal bone .temporal bone .
TheThe condylar blastemacondylar blastema arises from thearises from the
secondary condylar cartilage of thesecondary condylar cartilage of the

The meckle’s cartilage plays no part in theThe meckle’s cartilage plays no part in the
development of the mandibular condyle, itdevelopment of the mandibular condyle, it
does not contribute to the formation of thedoes not contribute to the formation of the
TMJTMJ
Concomitently, the lateral pterygoidConcomitently, the lateral pterygoid
muscle develops medial to the futuremuscle develops medial to the future
condyle area, initiates movement ofcondyle area, initiates movement of
meckle’s cartilage by contraction at 8meckle’s cartilage by contraction at 8
weeks, functioning through the primaryweeks, functioning through the primary
meckelian joint .meckelian joint .

Between 10Between 10thth
and 12and 12thth
weeks postweeks post
conception , the accessory mandibularconception , the accessory mandibular
condylar cartilage develops as the firstcondylar cartilage develops as the first
blastema, growing towards the lateralblastema, growing towards the lateral
developing temporal blasteme .developing temporal blasteme .
The temporal articular fossa is initiallyThe temporal articular fossa is initially
convex but progressively assumes itsconvex but progressively assumes its
definitive concave shapedefinitive concave shape ..
The intervening mesenchyme is narrowedThe intervening mesenchyme is narrowed
by condylar growthby condylar growth

During the 10During the 10thth
week 2 clefts develop in theweek 2 clefts develop in the
interposed vascular fibrous connectiveinterposed vascular fibrous connective
tissue, forming the 2 joint cavities andtissue, forming the 2 joint cavities and
thereby defining the intervening articularthereby defining the intervening articular
disc .disc .
1) The inferior compartment forms first (at1) The inferior compartment forms first (at
1010thth
weeks ), separating the future diskweeks ), separating the future disk
from the developing condyle .from the developing condyle .
2) The upper compartment starts to2) The upper compartment starts to
appear at about 11appear at about 111/21/2
weeks .weeks .

Cavitation occurs by degradation ratherCavitation occurs by degradation rather
than by enzymatic liquefaction or cellthan by enzymatic liquefaction or cell
death .death .
Synovial membrane invasion may beSynovial membrane invasion may be
necessary for cavitation .necessary for cavitation .
Synovial-fluid production by this methodSynovial-fluid production by this method
lubricates movement in the joint .lubricates movement in the joint .
Muscle movement is requisite to jointMuscle movement is requisite to joint
cavitation .cavitation .

TheThe ARTICULAR DISCARTICULAR DISC appearing at 7appearing at 71/21/2
weeks, is biconcave ab initio , suggestingweeks, is biconcave ab initio , suggesting
genetic determination and not functionalgenetic determination and not functional
shaping .shaping .
It is subdivided intoIt is subdivided into
1)superior laminae1)superior laminae
2)intermediate laminae2)intermediate laminae
3)inferior laminae3)inferior laminae
The disc is continues ventrally with theThe disc is continues ventrally with the
tendon of the lateral ptergoid muscle .tendon of the lateral ptergoid muscle .

TheThe superior laminasuperior lamina, following the counter, following the counter
of the squamous temporal bone , insert inof the squamous temporal bone , insert in
the region of the peterosquamous fissure.the region of the peterosquamous fissure.
TheThe intermediate laminaeintermediate laminae continues intocontinues into
the middle ear through the ptergotympanicthe middle ear through the ptergotympanic
fissure , inserting into the malleus andfissure , inserting into the malleus and
anterior ligament of the malleus .anterior ligament of the malleus .
TheThe inferior laminainferior lamina curves caudally andcurves caudally and
insert into the dorsal aspect of theinsert into the dorsal aspect of the
mandibular condyle .mandibular condyle .

The joint capsule , composed of fibrousThe joint capsule , composed of fibrous
tissue and recognised by the 11tissue and recognised by the 11thth
weekweek
post conception forms lateral ligaments .post conception forms lateral ligaments .

POST NATAL GROWTH OFPOST NATAL GROWTH OF
MANDIBLEMANDIBLE
The shape and size of the diminutive fetalThe shape and size of the diminutive fetal
mandible undergo considerable transmandible undergo considerable trans
formation during its growth andformation during its growth and
development .development .
Although the mandible appears as a singleAlthough the mandible appears as a single
bone in the adult , it is developmentally andbone in the adult , it is developmentally and
functionally divisible into several skeletalfunctionally divisible into several skeletal
subunits .subunits .

The functioning of the related tongue andThe functioning of the related tongue and
the perioral muscles and the expansion ofthe perioral muscles and the expansion of
the oral and the pharyengeal cavitiesthe oral and the pharyengeal cavities
provide stimuli for mandibular growth toprovide stimuli for mandibular growth to
reach its full potential .reach its full potential .
Of all the facial bones, the mandibleOf all the facial bones, the mandible
undergoes the most growth postnatally .undergoes the most growth postnatally .

The initial seperation of the right and leftThe initial seperation of the right and left
bodies of the mandible at the midlinebodies of the mandible at the midline
symphysis menti is gradually eliminatedsymphysis menti is gradually eliminated
between the 4between the 4thth
and 12and 12thth
months after birth .months after birth .
When ossification converts theWhen ossification converts the
syndesmosis into a synostosis , uniting thesyndesmosis into a synostosis , uniting the
two halves .two halves .
Limited growth takes place at theLimited growth takes place at the
symphysis menti until fusion occurs .symphysis menti until fusion occurs .

The main sites of the post natalThe main sites of the post natal
mandibular growth are at the condylarmandibular growth are at the condylar
cartilage , the posterior border of the rami,cartilage , the posterior border of the rami,
and the alveolar ridges .and the alveolar ridges .
These area of bone deposition largelyThese area of bone deposition largely
account for increase in the height, length,account for increase in the height, length,
and width of the mandible .and width of the mandible .
However , superimposed upon thisHowever , superimposed upon this
increment growth are numerous , regionalincrement growth are numerous , regional
remodelling changes that are subject toremodelling changes that are subject to
local functional influences involvinglocal functional influences involving
selective resorption and displacement ofselective resorption and displacement of
individual mandibular elements .individual mandibular elements .

By the end of 1By the end of 1stst
year life , the mandibleyear life , the mandible
appears as a single bone.appears as a single bone.
It configures symmetrically as a U- shapedIt configures symmetrically as a U- shaped
structure as it accomodates thestructure as it accomodates the
mandibular dentition and completes , withmandibular dentition and completes , with
the maxillary dentition, the dental arches .the maxillary dentition, the dental arches .

Ramus remodelingRamus remodeling
The significance of the ramus of theThe significance of the ramus of the
mandible is mostly that its provide anmandible is mostly that its provide an
attachment base for masticatory muscles .attachment base for masticatory muscles .
what usually isn’t mentioned, however, iswhat usually isn’t mentioned, however, is
the key role of the ramus in placing thethe key role of the ramus in placing the
corpus and dental arch into ever changingcorpus and dental arch into ever changing
fit with the growing maxilla and the face’sfit with the growing maxilla and the face’s
limitless structural variations.limitless structural variations.
This is provided by critical remodeling andThis is provided by critical remodeling and
adjustments in ramus alingment, verticaladjustments in ramus alingment, vertical
length, and anteroposterior breadth .length, and anteroposterior breadth .

The ramus remodelling is important ;The ramus remodelling is important ;
1)It positions the lower arch in occlusion1)It positions the lower arch in occlusion
with the upperwith the upper
2)It is continously adaptive to the multitude2)It is continously adaptive to the multitude
of changing cranio facial conditions .of changing cranio facial conditions .
The principal vectors of mandibular growthThe principal vectors of mandibular growth
areare posterior and superiorposterior and superior
The ramus is therby remodelled in aThe ramus is therby remodelled in a
generally posterosuperior manner whilegenerally posterosuperior manner while
the mandible as a whole becomesthe mandible as a whole becomes
displaceddisplaced antero-inferiorlyantero-inferiorly

The whole ramus becomes relocatedThe whole ramus becomes relocated
posteriorly by resorptive and depositoryposteriorly by resorptive and depository
remodelling , and the former anterior part ofremodelling , and the former anterior part of
the ramus is structurally altered into anthe ramus is structurally altered into an
addition to the corpus, which therby becomesaddition to the corpus, which therby becomes
lengthened by this remodelling process .lengthened by this remodelling process .
The remodelling of ramus in a backwardThe remodelling of ramus in a backward
direction has been pictured as 2-dimensionaldirection has been pictured as 2-dimensional
process.process.
But it cannot be represented in a conventionalBut it cannot be represented in a conventional
2-dimensional headfilms and tracing2-dimensional headfilms and tracing
Among this is the lingual tuberosityAmong this is the lingual tuberositywww.indiandentalacademy.comwww.indiandentalacademy.com

Lingual tuberosityLingual tuberosity

Yet, this structure is not even included inYet, this structure is not even included in
thethe BASIC VOCABULARY OFBASIC VOCABULARY OF
CEPHALOMETRICSCEPHALOMETRICS ..
The reason is simple that it is notThe reason is simple that it is not
recognizable in the headfilm .recognizable in the headfilm .
This presence a severe handicap becauseThis presence a severe handicap because
the lingual tuberosity is not only a majorthe lingual tuberosity is not only a major
growth and remodeling site but it also thegrowth and remodeling site but it also the
effective boundary betweeneffective boundary between ramusramus andand
thethe corpus .corpus .

The lingual tuberosity grows posterioly byThe lingual tuberosity grows posterioly by
deposition on posterior facing surface .deposition on posterior facing surface .
It protrudes noticeably in a lingualIt protrudes noticeably in a lingual
direction .direction .
The prominence is augumented by theThe prominence is augumented by the
presence of a large resorptive field justpresence of a large resorptive field just
below it .below it .
This resorotive field produces aThis resorotive field produces a
depression, thedepression, the LINGUAL FOSSA.LINGUAL FOSSA.
The tuberosity remodels in an almostThe tuberosity remodels in an almost
directly posterior direction, with a slightdirectly posterior direction, with a slight
lateral shift .lateral shift .

The posterior growth is accomplished byThe posterior growth is accomplished by
continued new deposits of bone on itscontinued new deposits of bone on its
posterior-facing exposure.posterior-facing exposure.
As this take place , that part of the ramusAs this take place , that part of the ramus
just behind the tuberosity remodelsjust behind the tuberosity remodels
medially .medially .
This area becomes a part of the corpus,This area becomes a part of the corpus,
thereby lengthening it .thereby lengthening it .

RAMUS TO CORPUSRAMUS TO CORPUS
REMODELLING CONVERSIONREMODELLING CONVERSION
In general the arch length is increasedIn general the arch length is increased
and corpus has been lengthened byand corpus has been lengthened by
1)Deposits on the posterior surface of the1)Deposits on the posterior surface of the
lingual tuberosity and the contiguouslingual tuberosity and the contiguous
lingual side of the ramuslingual side of the ramus
2)A resultant lingual shift of the anterior part2)A resultant lingual shift of the anterior part
of the ramus to become added to theof the ramus to become added to the
corpus .corpus .

The presence of resorption on the anteriorThe presence of resorption on the anterior
border of the ramus is described asborder of the ramus is described as
“making the room for the last molar”.“making the room for the last molar”.
It results in the entire relocation of theIt results in the entire relocation of the
ramus in a posterior direction.ramus in a posterior direction.
This movement continues from the tinyThis movement continues from the tiny
mandible of the fetus to the attainment ofmandible of the fetus to the attainment of
full adult mandible size.full adult mandible size.

Because the bicondylar dimension isBecause the bicondylar dimension is
established much earlier in childhood ,established much earlier in childhood ,
bilateral growth seperation between thebilateral growth seperation between the
right and the left condyles is minimalright and the left condyles is minimal
beyond the early childhood years .beyond the early childhood years .

Coronoid processCoronoid process
It has a propeller-like twist, so that itsIt has a propeller-like twist, so that its
lingual surface face 3 general directions atlingual surface face 3 general directions at
once posteriorly, superiorly and medially.once posteriorly, superiorly and medially.

The buccal side of the coronoid processThe buccal side of the coronoid process
has a resorptive type of periosteal surface.has a resorptive type of periosteal surface.
The remainder of most of theThe remainder of most of the superior partsuperior part
of the ramusof the ramus, including the whole area just, including the whole area just
below the mandibular (sigmoid) notch andbelow the mandibular (sigmoid) notch and
the superior portion of the condylar neckthe superior portion of the condylar neck
grows superiorly by deposition on thegrows superiorly by deposition on the
lingual side and resorption on the buccallingual side and resorption on the buccal
side .side .

The lower part of the ramus below theThe lower part of the ramus below the
coronoid process also has a twistedcoronoid process also has a twisted
contour.contour.
Its buccal side faces posteriorly towardsIts buccal side faces posteriorly towards
the direction of the backward growth andthe direction of the backward growth and
thus , has a depository surface .thus , has a depository surface .
The opposite lingual side, facing awayThe opposite lingual side, facing away
from the direction of growth, is resorptive.from the direction of growth, is resorptive.

Antegonial notchAntegonial notch

The gonial region is anatomically variableThe gonial region is anatomically variable
and, therefore much variations is involvedand, therefore much variations is involved
in its pattern of growth.in its pattern of growth.
Mandibular foramen relocates backwardMandibular foramen relocates backward
and upward by deposition on the anteriorand upward by deposition on the anterior
and resorption from the posterior part ofand resorption from the posterior part of
the rim .the rim .
The foramen, from childhood through oldThe foramen, from childhood through old
age, maintains a constant position aboutage, maintains a constant position about
midway between the anterior and posteriormidway between the anterior and posterior
borders of the ramus.borders of the ramus.

Even when the ramus undergoes markedEven when the ramus undergoes marked
alterations associated with edentulismalterations associated with edentulism
(during which it may become narrow) ,this(during which it may become narrow) ,this
foramen usually sustains a midwayforamen usually sustains a midway
location.location.

ROLE OF CONDYLARROLE OF CONDYLAR
CARTILAGECARTILAGE
The condyle is of special interest becauseThe condyle is of special interest because
it is a major site of growthit is a major site of growth
It is involved in one of the mostIt is involved in one of the most
complicated articulation of the body , andcomplicated articulation of the body , and
there have been so many opinions aboutthere have been so many opinions about
its role in mandibular growth .its role in mandibular growth .
The mandible is really a membrane boneThe mandible is really a membrane bone
remodelling over all surfaces, though oneremodelling over all surfaces, though one
part develops in response to apart develops in response to a
phylogenetically altered developmentalphylogenetically altered developmental
situation and becomes condylar region .situation and becomes condylar region .

The condylar cartilage is a secondaryThe condylar cartilage is a secondary
cartilage (meaning that it did not developcartilage (meaning that it did not develop
by differentiation from embryonic primaryby differentiation from embryonic primary
cartilage) which makes an importantcartilage) which makes an important
contribution to the over all length of thecontribution to the over all length of the
Regional adaptive growth in the condylarRegional adaptive growth in the condylar
area is important because the corpus ofarea is important because the corpus of
the mandible must be maintained inthe mandible must be maintained in
functioning juxtaposition with the base offunctioning juxtaposition with the base of
the skull where it articulates.the skull where it articulates.

The many arguments about condylarThe many arguments about condylar
growth focous mostly on one question; Isgrowth focous mostly on one question; Is
the condylar cartilage the principal forcethe condylar cartilage the principal force
that produces the forward and downwardthat produces the forward and downward
displacement of the mandible ?displacement of the mandible ?
For many years it was considered theFor many years it was considered the
primary growth centre of bone .primary growth centre of bone .
Proponents of the functional matrix theoryProponents of the functional matrix theory
claims that some mandibles functionclaims that some mandibles function
adequately and seem to be positionedadequately and seem to be positioned
rather normally when condyles are absent.rather normally when condyles are absent.

They concluded thatThey concluded that
soft tissuesoft tissue
development cariesdevelopment caries
the mandible forwardthe mandible forward
and downward whileand downward while
condylar growth fills incondylar growth fills in
the resultant space tothe resultant space to
maintain the contactmaintain the contact
with the basicranium.with the basicranium.

The growth mechanism of the condylarThe growth mechanism of the condylar
area is fairely clear, the main factors beingarea is fairely clear, the main factors being
the mesenchymal cells i.e(the periosteum)the mesenchymal cells i.e(the periosteum)
above the cartilage itself, how they growabove the cartilage itself, how they grow
and what they influence them.and what they influence them.
The condyle does not determine theThe condyle does not determine the
mandibular growth, rather it is themandibular growth, rather it is the
mandible which determines condylarmandible which determines condylar
growth .growth .
Articular function determines condylarArticular function determines condylar
growth, and articular function is dependentgrowth, and articular function is dependent
on how the mandible grows.on how the mandible grows.

Mandible growth is determined by factorsMandible growth is determined by factors
outside the mandible –muscles, maxillaryoutside the mandible –muscles, maxillary
growth, etcgrowth, etc
An endocondral growth mechanism isAn endocondral growth mechanism is
required because the condyle grows in arequired because the condyle grows in a
direction of the articulation in the face ofdirection of the articulation in the face of
pressure, a situation which purepressure, a situation which pure
intramembrenous bone growth could notintramembrenous bone growth could not
tolerate .tolerate .
The condyle is a secondary cartilage andThe condyle is a secondary cartilage and
is presumed not to have such potential.is presumed not to have such potential.
This assumption fits nearly withThis assumption fits nearly with
F.M.TheoryF.M.Theory www.indiandentalacademy.comwww.indiandentalacademy.com

The growth cartilage may act as aThe growth cartilage may act as a
“functional matrix” to stretch the“functional matrix” to stretch the
periosteum, inducing the lengthenedperiosteum, inducing the lengthened
periosteum to form intramembrenous boneperiosteum to form intramembrenous bone
beneath it .beneath it .
The formation of the bone within theThe formation of the bone within the
condylar head causes the mandibular ramicondylar head causes the mandibular rami
to grow upwards and backwards,to grow upwards and backwards,
displacing the entire mandible in andisplacing the entire mandible in an
opposite downward and forward direction.opposite downward and forward direction.

In the infants the condyles of the mandibleIn the infants the condyles of the mandible
are inclined almost horizontally, so thatare inclined almost horizontally, so that
condylar growth leads to an increase incondylar growth leads to an increase in
the length of the mandible.the length of the mandible.
Due to the posterior divergence of the 2Due to the posterior divergence of the 2
halves of the body of the mandible, growthhalves of the body of the mandible, growth
in the condylar head of the increasinglyin the condylar head of the increasingly
more widely displaced rami results inmore widely displaced rami results in
overall widening of the mandibular bodyoverall widening of the mandibular body

Alteration of the direction of theAlteration of the direction of the
mental foramenmental foramen

ALVEOLAR PROCESSALVEOLAR PROCESS
It develops as a protective trough inIt develops as a protective trough in
response to the tooth buds and becomesresponse to the tooth buds and becomes
superimposed upon the basal bone of thesuperimposed upon the basal bone of the
mandibular body.mandibular body.
It adds to the height and thickness of theIt adds to the height and thickness of the
body of the mandible .body of the mandible .
It fails to develop if teeth are absent andIt fails to develop if teeth are absent and
resorbs in response to tooth extraction.resorbs in response to tooth extraction.
The ortho dontic movement of teeth takesThe ortho dontic movement of teeth takes
place in the labile alveolar bone of bothplace in the labile alveolar bone of both
maxilla and mandible and fails to involvemaxilla and mandible and fails to involve
the underlying basal bonethe underlying basal bone

THE CHINTHE CHIN
It is formed in part of the mental ossiclesIt is formed in part of the mental ossicles
from accessory cartilages and the ventralfrom accessory cartilages and the ventral
end of meckel’s cartilage, is very poorlyend of meckel’s cartilage, is very poorly
developed in the infant .developed in the infant .
It develops almost as an independentIt develops almost as an independent
subunits of the mandible , influenced bysubunits of the mandible , influenced by
sexual as well as specific genetic factors .sexual as well as specific genetic factors .
Thus, the chin becomes significant only atThus, the chin becomes significant only at
adolescence, from the development of theadolescence, from the development of the
mental protruberence and tubercles.mental protruberence and tubercles.

The skeletal “unit” of the chin may be anThe skeletal “unit” of the chin may be an
expression of the functional forces exertedexpression of the functional forces exerted
by theby the lateral pterygoid muscleslateral pterygoid muscles that, inthat, in
pulling the mandible forward, indirectlypulling the mandible forward, indirectly
stress the mental symphyseal region bystress the mental symphyseal region by
their concomitant inward pull.their concomitant inward pull.
Bone buttressing to resist muscleBone buttressing to resist muscle
stressing which is more powerful in male,stressing which is more powerful in male,
is expresed in the more prominent maleis expresed in the more prominent male
chinchin
It is lacking in all other primates and inIt is lacking in all other primates and in
hominid ancestors.hominid ancestors.www.indiandentalacademy.comwww.indiandentalacademy.com

TheThe MENTAL PROTRUBERENCEMENTAL PROTRUBERENCE formsforms
by osseous deposition during childhood.by osseous deposition during childhood.
Its prominence is accentuated by boneIts prominence is accentuated by bone
resorption in the alveolar region above it,resorption in the alveolar region above it,
creating the supramental concavity knowncreating the supramental concavity known
asas “POINT B”.“POINT B”.
Under development of the chin is knownUnder development of the chin is known
asas microgenia.microgenia.

2) AMOUNT AND DIRECTIONS2) AMOUNT AND DIRECTIONS
A)HEIGHT:A)HEIGHT: The RAMUS height correlatesThe RAMUS height correlates
well with corpus length and overallwell with corpus length and overall
mandibular lengthmandibular length
Alveolar process height increases areAlveolar process height increases are
highly correlated with erruptionhighly correlated with erruption
Anterior mandibular height is related toAnterior mandibular height is related to
dental development and overalldental development and overall
mandibular growth downwards andmandibular growth downwards and
forwards.forwards.

Ramus uprightingRamus uprighting

B)WIDTH:B)WIDTH: bigonial and bicondylarbigonial and bicondylar
diameter increases are a function ofdiameter increases are a function of
growth in overall mandibular length.growth in overall mandibular length.
Most width increases occur simplyMost width increases occur simply
because the mandible grows longer ,because the mandible grows longer ,
though some periosteal deposition occurs.though some periosteal deposition occurs.

C)LENGTH:C)LENGTH:

D)ROTATIOND)ROTATION
Serial ceph studies , using cranial baseSerial ceph studies , using cranial base
registrations, imply that normally theregistrations, imply that normally the
mandible is carried away from themandible is carried away from the
posterior cranial base in a downward andposterior cranial base in a downward and
forward direction.forward direction.
When the mandibular corpus is steeplyWhen the mandibular corpus is steeply
related to the posterior cranial base andrelated to the posterior cranial base and
anterior facial height increases are greateranterior facial height increases are greater
than those of posteriorly, the mandiblethan those of posteriorly, the mandible
sometime said to rotate “POSTERIORLY”.sometime said to rotate “POSTERIORLY”.

Obversely, when posterior facial height isObversely, when posterior facial height is
greater than normal , the bite tends to begreater than normal , the bite tends to be
deeper and mandible is said to displaydeeper and mandible is said to display
“ANTERIOR”“ANTERIOR” rotationrotation
BJORK and others studies this so calledBJORK and others studies this so called
“mandibular rotation” by use of metallic“mandibular rotation” by use of metallic
implants and other methodsimplants and other methods
The nature and amount of rotation areThe nature and amount of rotation are
misinterpreted through the use of severalmisinterpreted through the use of several
land marksland marks
Confusion was eliminated by the use ofConfusion was eliminated by the use of
natural markersnatural markers

He also made clear distinction betweenHe also made clear distinction between
1)matrix rotation1)matrix rotation: often goes in the form: often goes in the form
of a pendulum movement with theof a pendulum movement with the
rotation point in the condylerotation point in the condyle

2)INTER MATRIX ROTATION:2)INTER MATRIX ROTATION: Is theIs the
rotationrotation of the mand corpus inner half of itsof the mand corpus inner half of its
matrix within the mand copusmatrix within the mand copus

E) TIMINGE) TIMING
Spurts in mandibular dimensions areSpurts in mandibular dimensions are
common but are not universal and arecommon but are not universal and are
more frequently seen in boys than girls,more frequently seen in boys than girls,
occuring app 1occuring app 11/21/2
years earlier in girls.years earlier in girls.
The most imp spurt in mand growth is thatThe most imp spurt in mand growth is that
related to pubertyrelated to puberty
Almost all first pubertal spurts occur afterAlmost all first pubertal spurts occur after
ulnar sesamoid occification and beforeulnar sesamoid occification and before
menarchy -2 developmental events whichmenarchy -2 developmental events which
have been used to predict skeletal growthhave been used to predict skeletal growth
spurt.spurt. www.indiandentalacademy.comwww.indiandentalacademy.com

Growth relative to the maxillaGrowth relative to the maxilla
In fetal lifeIn fetal life
Initially the mandible is considered largerInitially the mandible is considered larger
than the maxillathan the maxilla
By 8By 8thth
week post conception theweek post conception the
development of maxilla overlaps thedevelopment of maxilla overlaps the
mandiblemandible
The subsequent greater growth in theThe subsequent greater growth in the
mandible results in the app equal size ofmandible results in the app equal size of
upper and lower jaw by 11upper and lower jaw by 11thth
weeksweeks

Mandibular growth lags behind maxillaryMandibular growth lags behind maxillary
growth between 13growth between 13thth
and 20and 20thth
week due toweek due to
change over from meckle’s cartilage tochange over from meckle’s cartilage to
condylar secondary cartilage .condylar secondary cartilage .
At birthAt birth
The mandible tend to be retrognathic toThe mandible tend to be retrognathic to
the maxilla although the 2 may be equalthe maxilla although the 2 may be equal
size .size .
This retrognathic is normally correctedThis retrognathic is normally corrected
early inearly in post natal lifepost natal life by rapid mandibularby rapid mandibular
growth and forward displacement togrowth and forward displacement to
establishestablish ANGLE CLASS 1ANGLE CLASS 1
MAXILLOMANDIBULARMAXILLOMANDIBULAR relationshiprelationship

POST NATAL GROWTH OF TMJPOST NATAL GROWTH OF TMJ
The TMJ of the new born is aThe TMJ of the new born is a
comparitively lax structure, with stabilitycomparitively lax structure, with stability
solely depend on the capsule surroundingsolely depend on the capsule surrounding
the joint .the joint .
It is more mobile then at any time later.It is more mobile then at any time later.
At birth the mandibular fossa is almost flatAt birth the mandibular fossa is almost flat
and bears no articular tubercle .and bears no articular tubercle .
Only after the eruption of the permanentOnly after the eruption of the permanent
dentition at 7 years, articular tubercledentition at 7 years, articular tubercle
begins to become prominent .begins to become prominent .

POST NATAL GROWTH OF TMJPOST NATAL GROWTH OF TMJ

Its development accelerates until the 12Its development accelerates until the 12thth
year of life .year of life .
When the condyle is absent , there is noWhen the condyle is absent , there is no
well defined fossa or tubercle .well defined fossa or tubercle .
The joint structure grow laterallyThe joint structure grow laterally
concomitant with the widening of theconcomitant with the widening of the
neuro-cranium.neuro-cranium.
The temporal rather than condyle is criticalThe temporal rather than condyle is critical
in establishing this lateral growth.in establishing this lateral growth.
The articular surface of the fossa andThe articular surface of the fossa and
tubercle becomes more fibrous and lesstubercle becomes more fibrous and less
vascular with age .vascular with age .

In post natal life , as the articular tubercleIn post natal life , as the articular tubercle
grows, the disc changes shape andgrows, the disc changes shape and
becomes more compact, less cellular, andbecomes more compact, less cellular, and
more collagenous.more collagenous.
The mature disc is avascular and aneuralThe mature disc is avascular and aneural
in its central position but is filled within its central position but is filled with
vessels, nerves, and elastic fibresvessels, nerves, and elastic fibres
posteriorly attaching it to theposteriorly attaching it to the
squamotympanic suture.squamotympanic suture.

Histo morphology of TMJHisto morphology of TMJ
The tissue comprising both the condylarThe tissue comprising both the condylar
portion and of the TMJ and the temporalportion and of the TMJ and the temporal
portion of the TMJ is divided into 2 ways:portion of the TMJ is divided into 2 ways:
1)an articular tissue layer1)an articular tissue layer
2)a subarticular layer of growth cartilage2)a subarticular layer of growth cartilage
Each of this layer is present in neonatesEach of this layer is present in neonates
and remains in the condyle throughand remains in the condyle through
maturitymaturity

1)The1)The ARTICULAR LAYERARTICULAR LAYER of the condyleof the condyle
surface of the TMJ is continues with the outer,surface of the TMJ is continues with the outer,
fibrous layer of the bilaminar periosteumfibrous layer of the bilaminar periosteum
encapsulating the condylar neckencapsulating the condylar neck
It consists of a largely avascular denseIt consists of a largely avascular dense
fibroelastic connective tissue whose collegenfibroelastic connective tissue whose collegen
fibres are oriented parallel to the articularfibres are oriented parallel to the articular
surfacesurface
Few fibroblast which are present in theFew fibroblast which are present in the
articular layer , functions primarily inarticular layer , functions primarily in
maintenance rather than actual growthmaintenance rather than actual growth
processprocess www.indiandentalacademy.comwww.indiandentalacademy.com

2)The2)The SUB ARTICULAR LAYER OFSUB ARTICULAR LAYER OF
GROWTH CARTILAGEGROWTH CARTILAGE in the condyle isin the condyle is
comprised of hyaline cartilage that iscomprised of hyaline cartilage that is
derived secondarly i.e. is not a primaryderived secondarly i.e. is not a primary
growth cartilage.growth cartilage.
It consist of 3 layersIt consist of 3 layers
1)proliferative layer1)proliferative layer
2)chondroblastic layer2)chondroblastic layer
3)zone of endocondral ossification3)zone of endocondral ossification

In general, the growth cartilage begins asIn general, the growth cartilage begins as
a relatively thick structure ina relatively thick structure in neonateneonate (1.25(1.25
to 1.5 mm thick) but becomes muchto 1.5 mm thick) but becomes much
thinner (0.3mm) bythinner (0.3mm) by mixed dentition stagemixed dentition stage..
The cartilage remains thin but well-definedThe cartilage remains thin but well-defined
and actively growing in theand actively growing in the permanentpermanent
dentition stagedentition stage until, by age 20-30 yrs, theuntil, by age 20-30 yrs, the
cartilage disappears and the condyle iscartilage disappears and the condyle is
capped by bony plate .capped by bony plate .

TEMPORAL BONETEMPORAL BONE
The temporal component of the TMJ in theThe temporal component of the TMJ in the
neonateneonate is essentially flat and aricular disc isis essentially flat and aricular disc is
highly vascularhighly vascular
DuringDuring primary dentitionprimary dentition, app 3 yrs of age, th, app 3 yrs of age, th
temporal surface takes S-SHAPEDtemporal surface takes S-SHAPED
COUNTER and articular disc becomesCOUNTER and articular disc becomes
avascular in the central regionavascular in the central region
Thereafter the temporal surface of TMJ growsThereafter the temporal surface of TMJ grows
slowly, with articular eminence becomesslowly, with articular eminence becomes
steeper with bone deposititon the fossasteeper with bone deposititon the fossa
becomes deeper.becomes deeper.
This process continues forThis process continues for 4 decades4 decadeswww.indiandentalacademy.comwww.indiandentalacademy.com

Movements of the of TMJMovements of the of TMJ

THEORIES OF MANDIBULARTHEORIES OF MANDIBULAR
GROWTHGROWTH
1)GENETIC THEORY1)GENETIC THEORY
2)CARTILAGENOUS THEORY2)CARTILAGENOUS THEORY
3)FUNCTIONAL MATRIX THEORY3)FUNCTIONAL MATRIX THEORY
4)SERVO SYSTEM THEORY OF4)SERVO SYSTEM THEORY OF
MANDIBULAR GROWTHMANDIBULAR GROWTH
5)ENLOW’S “V” PRINCIPLE5)ENLOW’S “V” PRINCIPLE

GENETIC THEORYGENETIC THEORY
The historically earlier paradigms assertsThe historically earlier paradigms asserts
that the growth of the mandible isthat the growth of the mandible is
genetically determined .genetically determined .
According to this view, the cartilage of theAccording to this view, the cartilage of the
mandibular condyle is a primary growthmandibular condyle is a primary growth
centre that is analogous to an epiphysealcentre that is analogous to an epiphyseal
growth plate and whose growth forces thegrowth plate and whose growth forces the
mandible to expand downward andmandible to expand downward and
forward away from the tmjforward away from the tmj

CARTILAGENOUS THEORYCARTILAGENOUS THEORY
 This theory was put forward byThis theory was put forward by JAMESJAMES
SCOTTSCOTT..
 According to him intrinsic growthAccording to him intrinsic growth
controlling factors are present in cartilagecontrolling factors are present in cartilage
andand periosteumperiosteum andand suturessutures being onlybeing only
secondarysecondary..
 He feels that cartilaginous sites throughHe feels that cartilaginous sites through
the skull as primarythe skull as primary centrescentres of growth.of growth.

Growth inGrowth in maxillamaxilla is attributed to theis attributed to the nasalnasal
septal cartilageseptal cartilage..
TheThe mandiblemandible is considered as theis considered as the
diaphysis of a long bonediaphysis of a long bone, bent into horse, bent into horse
shape with epiphysis removed so thatshape with epiphysis removed so that
there is cartilage constituting half anthere is cartilage constituting half an
epiphyseal plate at the ends which areepiphyseal plate at the ends which are
represented by the condyle.represented by the condyle.

If this analogy was correct, of course theIf this analogy was correct, of course the
cartilage at the mandibular condylescartilage at the mandibular condyles
should behave like true growth cartilage.should behave like true growth cartilage.
Modern experiments indicates that,Modern experiments indicates that,
although the analogy is attractive, it isalthough the analogy is attractive, it is
incorrectincorrect
Transplantation experimentsTransplantation experiments
demonstrated that no growth wasdemonstrated that no growth was
observed when mandibular condyle wasobserved when mandibular condyle was
transplanted.transplanted.
The cartilage from the mandibular condyleThe cartilage from the mandibular condyle
showed less growth in culture than othershowed less growth in culture than other
cartilagecartilage www.indiandentalacademy.comwww.indiandentalacademy.com

A blow to one side of mandible mayA blow to one side of mandible may
fracture the condylar process on thefracture the condylar process on the
opposite side. When this happens the pullopposite side. When this happens the pull
of the lateral pterygoid muscle distractsof the lateral pterygoid muscle distracts
the condylar fragments including all thethe condylar fragments including all the
cartilage and it subsequently resorbs .cartilage and it subsequently resorbs .
The condylar fracture occurs relativelyThe condylar fracture occurs relatively
frequent in children.frequent in children.
If the condyle was an important growthIf the condyle was an important growth
centre, one would expect to see severecentre, one would expect to see severe
growth impairment after such an injury atgrowth impairment after such an injury at
an earlier age.an earlier age.

FUNCTIONAL MATRIX THEORYFUNCTIONAL MATRIX THEORY
FOR MANDIBULAR GROWTHFOR MANDIBULAR GROWTH
Mandibular growth (as well as neuralMandibular growth (as well as neural
growth) is seen now to be a combinationgrowth) is seen now to be a combination
of both capsular and periosteal matrices.of both capsular and periosteal matrices.
The capsular matrix growth causes anThe capsular matrix growth causes an
expansion of the capsule as a whole.expansion of the capsule as a whole.
The enclosed and embedded macroThe enclosed and embedded macro
skeletal units (the mandible as a whole), isskeletal units (the mandible as a whole), is
passively and secondarily translated inpassively and secondarily translated in
space to successively new positions.space to successively new positions.

In normal conditions the periostealIn normal conditions the periosteal
matrices related to the constituentmatrices related to the constituent
mandibular microskeletal units alsomandibular microskeletal units also
respond to this volumetric expansion.respond to this volumetric expansion.
Such an alteration in their spatial positionSuch an alteration in their spatial position
inevitably causes them to grow, causesinevitably causes them to grow, causes
changes in their functional demands.changes in their functional demands.
These causes direct alteration in the sizeThese causes direct alteration in the size
and shape of their microskeletal units.and shape of their microskeletal units.
The sum of translation plus changes inThe sum of translation plus changes in
form comprises the totality of mandibularform comprises the totality of mandibular
growth.growth. www.indiandentalacademy.comwww.indiandentalacademy.com

Points in favoring functional matrixPoints in favoring functional matrix
theorytheory
The diminution in size of the coronoidThe diminution in size of the coronoid
process subsequent to expt denervation ofprocess subsequent to expt denervation of
the temporalis muscle.the temporalis muscle.
The shrinkage of alveolar processThe shrinkage of alveolar process
subsequent to tooth removalsubsequent to tooth removal
Mandibular ankylosis caused by severeMandibular ankylosis caused by severe
infection in the area of TMJ , leading toinfection in the area of TMJ , leading to
destruction of tissue and ultimate scarring.destruction of tissue and ultimate scarring.

The spatial maintainence of theThe spatial maintainence of the
appropriate foramina along a logarithmicappropriate foramina along a logarithmic
spiral path during growth in response tospiral path during growth in response to
the demand for an unloaded trigeminalthe demand for an unloaded trigeminal
neuro vascular bundle.neuro vascular bundle.
It is noted in some 20 to 25% children inIt is noted in some 20 to 25% children in
whom a growth deficit occurs afterwhom a growth deficit occurs after
condylar fracture could be somecondylar fracture could be some
inteference with function be the reason forinteference with function be the reason for
growth deficiency.growth deficiency.

Points against functional matrixPoints against functional matrix
theorytheory
MOSS theorises that the major determinantMOSS theorises that the major determinant
of growth of the maxilla and mandible is theof growth of the maxilla and mandible is the
enlargement of the nasal and oral cavities,enlargement of the nasal and oral cavities,
which grow in response to functoinal needs.which grow in response to functoinal needs.
The THEORY does not make it clear howThe THEORY does not make it clear how
functional needs are transmitted to thefunctional needs are transmitted to the
tissues.tissues.
In 75 to 80% of human children who suffer aIn 75 to 80% of human children who suffer a
condylar # , the resulting loss of the condylecondylar # , the resulting loss of the condyle
does not impede mandibular growth. Thedoes not impede mandibular growth. The
condyle regenates very nicely.condyle regenates very nicely.www.indiandentalacademy.comwww.indiandentalacademy.com

The emphasis of the functional matrixThe emphasis of the functional matrix
hypothesis is on all skeletal tissue ashypothesis is on all skeletal tissue as
responsive, as having degrees of plasticityresponsive, as having degrees of plasticity
during their growth and development .during their growth and development .
As a result, the focus of this theory isAs a result, the focus of this theory is
not on skeletal tissues per se , but on thenot on skeletal tissues per se , but on the
factors that influence their growth andfactors that influence their growth and
development.development.

SERVO SYSTEM THEORY OFSERVO SYSTEM THEORY OF
MANDIBULAR GROWTHMANDIBULAR GROWTH
This theory was proposed byThis theory was proposed by PETROVICPETROVIC andand
STUTZMANNSTUTZMANN (1977,1982,1984)(1977,1982,1984)
It was described most effectively in terms ofIt was described most effectively in terms of
CYBERNETIC MODELCYBERNETIC MODEL
According to this theory the growth of theAccording to this theory the growth of the
primary cartilages of the cephalic region andprimary cartilages of the cephalic region and
epiphyses is controlled primarily by the growthepiphyses is controlled primarily by the growth
harmone-stomatodeum complex.harmone-stomatodeum complex.
Extrinsic factors have little or no significantExtrinsic factors have little or no significant
affect on this growth except in the extreme.affect on this growth except in the extreme.

The growth of secondary cartilages suchThe growth of secondary cartilages such
as the condylar cartilage, on the otheras the condylar cartilage, on the other
hand, in influenced in two wayshand, in influenced in two ways
1)Directly by the harmone stomatideum1)Directly by the harmone stomatideum
complex andcomplex and
2)Indirectly by extrinsic factors such as2)Indirectly by extrinsic factors such as
muscle activity assosiated with oralmuscle activity assosiated with oral
function, which act to enhance the effectfunction, which act to enhance the effect
of the direct factors .of the direct factors .

Central elements in the servo system theoryCentral elements in the servo system theory
are the sagittal position of the maxillary dentalare the sagittal position of the maxillary dental
arch, which acts as a point of referencearch, which acts as a point of reference
(reference input according to cybernatic(reference input according to cybernatic
theory) for the mandible and the occlusaltheory) for the mandible and the occlusal
interface (the comparator or deviationinterface (the comparator or deviation
detector).detector).
According to servo system theory, the sagittalAccording to servo system theory, the sagittal
growth of the maxilla is primarily a result of thegrowth of the maxilla is primarily a result of the
growth of the nasal septal cartilage which isgrowth of the nasal septal cartilage which is
comprised of primarily cartilage andcomprised of primarily cartilage and
therefore is affected relatively little bytherefore is affected relatively little by
extrinsic factors .extrinsic factors .www.indiandentalacademy.comwww.indiandentalacademy.com

The position of the maxilla is “percived” byThe position of the maxilla is “percived” by
the mandible via the manner in which thethe mandible via the manner in which the
upper and lower dental arches fit together.upper and lower dental arches fit together.
As the maxilla grows downwards andAs the maxilla grows downwards and
forwards during the active growth periods,forwards during the active growth periods,
the mandible detects this growth throughthe mandible detects this growth through
minor changes in the occlusion, which areminor changes in the occlusion, which are
percived by the proprioceptors in thepercived by the proprioceptors in the
periodontal ligament as the teeth come inperiodontal ligament as the teeth come in
contact .contact .

The deviation between the maxilla and theThe deviation between the maxilla and the
mandible is then corrected by a slightmandible is then corrected by a slight
adjustment of the position of the mandibleadjustment of the position of the mandible
via neuro muscular activity sufficient tovia neuro muscular activity sufficient to
protrude the mandible to the optimal occlusalprotrude the mandible to the optimal occlusal
position.position.
The net effect of this process of adjustmentThe net effect of this process of adjustment
is the stimulation of chondrogenesis at theis the stimulation of chondrogenesis at the
mandibular condyle.mandibular condyle.

Growth patternGrowth pattern
The growth of the mandible from app oneThe growth of the mandible from app one
year of age through the end of pubertyyear of age through the end of puberty
follows a general growth curve.follows a general growth curve.
Downward and forward displacement ofDownward and forward displacement of
the mandible continues at a relativelythe mandible continues at a relatively
steady period.steady period.
Mandibular width is completed relativelyMandibular width is completed relatively
early in childhood, and shows significantlyearly in childhood, and shows significantly
less overall change during growth.less overall change during growth.

The rate of increase in mandibular lengthThe rate of increase in mandibular length
and height varies somewhat duringand height varies somewhat during
development, being precipitated duringdevelopment, being precipitated during
infancy, leveling off in the deciduousinfancy, leveling off in the deciduous
dentition period, intensifying during perioddentition period, intensifying during period
of mixed dentition , and finally showingof mixed dentition , and finally showing
significant growth spurt in the prepubertalsignificant growth spurt in the prepubertal
period and puberty, particularly in males.period and puberty, particularly in males.

According to an analysis of mandibularAccording to an analysis of mandibular
growth using the BURLINGTONgrowth using the BURLINGTON
GROWTH STUDYGROWTH STUDY

The presence of a pubertal growth spurt inThe presence of a pubertal growth spurt in
the craniofacial complex of boys in generalthe craniofacial complex of boys in general
and in the mandible in particular wasand in the mandible in particular was
reported by BJORK and HELM (1967)reported by BJORK and HELM (1967)

Factors influencing mandibularFactors influencing mandibular
growthgrowth
The mechanism responsible for the growth of theThe mechanism responsible for the growth of the
mandible have been investigated from the standmandible have been investigated from the stand
point of two broad concerns. The historicallypoint of two broad concerns. The historically
earlier of these relates primarily to the role ofearlier of these relates primarily to the role of
muscle function on the growth and form of themuscle function on the growth and form of the
mandible. Later particular attention was focussedmandible. Later particular attention was focussed
on two related issues;on two related issues;
1.Factors controlling the growth and adaptation of1.Factors controlling the growth and adaptation of
the TMJthe TMJ
2.And the extent to which the growth of the2.And the extent to which the growth of the
mandibular condyle can be influenced.mandibular condyle can be influenced.

Role of muscle functionRole of muscle function
The classic example was performed byThe classic example was performed by
Washburn(1947, scott 1954 ) who is an anatomistWashburn(1947, scott 1954 ) who is an anatomist
and anthropologist interested primarily in theand anthropologist interested primarily in the
evolution of primate skull.evolution of primate skull.
In order to evaluate the relationship between theIn order to evaluate the relationship between the
presence and function of temporalis muscle and thepresence and function of temporalis muscle and the
coronoid process..coronoid process..
Washburn removed the temporalis muscleWashburn removed the temporalis muscle
unilaterally in one day old rats. 3-5 months later, heunilaterally in one day old rats. 3-5 months later, he
found that the coronoid process had atrophied to thefound that the coronoid process had atrophied to the
point of disappearing on the operated side and waspoint of disappearing on the operated side and was
essentially normal on the side, the temporal crestessentially normal on the side, the temporal crest
was also absent on the operated side.was also absent on the operated side.

From this he concluded that the presenceFrom this he concluded that the presence
and function of temporalis muscle areand function of temporalis muscle are
necessary for the normal development ofnecessary for the normal development of
coronoid process.coronoid process.
Although the numerous studies involvingAlthough the numerous studies involving
muscle abalation all indicated that musclemuscle abalation all indicated that muscle
is an important factor influencing theis an important factor influencing the
growth and form of certain components ofgrowth and form of certain components of
the mandible ,the mechanism by whichthe mandible ,the mechanism by which
muscle accomplishes is not clearmuscle accomplishes is not clear
The altered blood supply to the skeletalThe altered blood supply to the skeletal
unit after muscle abalation could haveunit after muscle abalation could have
been the determining factorbeen the determining factor

BOYD and CO-WORKERSBOYD and CO-WORKERS detached thedetached the
temporalis muscle unilaterally in youngtemporalis muscle unilaterally in young
guinea pigs but did not completely removeguinea pigs but did not completely remove
the muscle from its insertion .the muscle from its insertion .
An alternative way to remove the function ofAn alternative way to remove the function of
the muscles of mastication without removingthe muscles of mastication without removing
the muscle and blood supply is by removingthe muscle and blood supply is by removing
the nerve .the nerve .
MOSS(1972,1975)MOSS(1972,1975) studies involvingstudies involving
unilateral lesioning of the trigeminal nerveunilateral lesioning of the trigeminal nerve
result in deviation of the maxillomandibularresult in deviation of the maxillomandibular
complex due to lesser growth on affectedcomplex due to lesser growth on affected
sideside

In summary all the available evidenceIn summary all the available evidence
indicates that the growth and form ofindicates that the growth and form of
certain regions of the mandible are relatedcertain regions of the mandible are related
to the associated muscle of mastication.to the associated muscle of mastication.
Muscle function acts primarily asMuscle function acts primarily as
1)a determinant of the growth and form of1)a determinant of the growth and form of
specific aspects of the periosteal matrix ofspecific aspects of the periosteal matrix of
the mandible, such as the coronoid andthe mandible, such as the coronoid and
angular processangular process
A modifier of the growth and form of theA modifier of the growth and form of the
rest of the mandible.rest of the mandible.

Growth and adaptation of TMJGrowth and adaptation of TMJ
Over the last two decades, the factorsOver the last two decades, the factors
controlling the growth and adaptation ofcontrolling the growth and adaptation of
TMJ and condyle have been central foci inTMJ and condyle have been central foci in
craniofacial biology.craniofacial biology.
Research have been influenced by 2Research have been influenced by 2
competing paradigms of cranio facialcompeting paradigms of cranio facial
biologybiology

Experimental investigations of the growthExperimental investigations of the growth
and adaptation of the mandibular condyleand adaptation of the mandibular condyle
have used a variety of analytical approachhave used a variety of analytical approach
1)studies in vivo translantation of the1)studies in vivo translantation of the
condylar cartilage to ectopic sites and incondylar cartilage to ectopic sites and in
vitro organ culture of the condylar cartilagevitro organ culture of the condylar cartilage
2)studies of condylectomy2)studies of condylectomy
3)studies of alteration of the position and3)studies of alteration of the position and
function of the mandibular condyle in situ.function of the mandibular condyle in situ.

In vivo transplantation and Iv vitro organIn vivo transplantation and Iv vitro organ
culture:culture:
The primary purpose of transplantation ofThe primary purpose of transplantation of
the condyle to an ectopic site is to controlthe condyle to an ectopic site is to control
for local factors (biomechanicalfor local factors (biomechanical
/functional) that affect growth ./functional) that affect growth .
Similarly, placing the condylar cartilage inSimilarly, placing the condylar cartilage in
organ culture in vitro make it possible toorgan culture in vitro make it possible to
remove extrinsic influence on growth.remove extrinsic influence on growth.

These studies indicate that condylarThese studies indicate that condylar
cartilage explants, as well as othercartilage explants, as well as other
secondary explants, undergo only limitedsecondary explants, undergo only limited
growth when transplanted into nongrowth when transplanted into non
functional ectopic sites and organ culturefunctional ectopic sites and organ culture
media.media.
The growth of the secondary cartilage isThe growth of the secondary cartilage is
not determined to any great extent bynot determined to any great extent by
intrinsic, genetic factors.intrinsic, genetic factors.

Condylectomy studies:Condylectomy studies:
These studies provide an indirect analysisThese studies provide an indirect analysis
of the role of the mandibular condyle in theof the role of the mandibular condyle in the
growth of the mandible as its focus ongrowth of the mandible as its focus on
mandibular growth in the absence of themandibular growth in the absence of the
condyle rather than the growth of thecondyle rather than the growth of the
condyle itself.condyle itself.
Virtually all expt studies involvingVirtually all expt studies involving
condylectomies in growing animals havecondylectomies in growing animals have
found that removal of the condyle resultsfound that removal of the condyle results
in abnormal condylar growthin abnormal condylar growth

After condylectomy, the mandible isAfter condylectomy, the mandible is
deficient anteroposteriorly , there is adeficient anteroposteriorly , there is a
reduction in facial height and in unilateralreduction in facial height and in unilateral
case , the mandible is deviated tocase , the mandible is deviated to
operated site .operated site .
A study byA study by MELANSON AAND VANMELANSON AAND VAN
DYKEN(1962)DYKEN(1962) provide a unique approachprovide a unique approach
to the condylectomy studiesto the condylectomy studies
They excised the temporal aspect of theThey excised the temporal aspect of the
TMJ in growing rats, thus freeing theTMJ in growing rats, thus freeing the
condyle.condyle.

After several months they found that thereAfter several months they found that there
was a pronounced increase in the lengthwas a pronounced increase in the length
of the condylar neck on the operated side,of the condylar neck on the operated side,
while the un operated site was normal.while the un operated site was normal.
These results indicate that the condylarThese results indicate that the condylar
cartilage grew at a greater than normalcartilage grew at a greater than normal
rate and amount , and that it was therate and amount , and that it was the
release of any inhibiting structurerelease of any inhibiting structure
proximally that permited to do so.proximally that permited to do so.

Developmental Anomalies ofDevelopmental Anomalies of
MandibleMandible
AGNATHIAAGNATHIA
MANDIBULO-FACIAL DYSOSTOSISMANDIBULO-FACIAL DYSOSTOSIS
APLASIA OF THE MANDIBLE ANDAPLASIA OF THE MANDIBLE AND
HYOID ARCHHYOID ARCH
MICROGNATHIAMICROGNATHIA
MACROGNATHIAMACROGNATHIA

Developmental Anamolies of TMJDevelopmental Anamolies of TMJ
Aplasia of mandibular condyleAplasia of mandibular condyle
Hypoplasia of mandibular condyleHypoplasia of mandibular condyle
Hyperplasia of mandibular condyleHyperplasia of mandibular condyle
AnkylosisAnkylosis
Unilateral ankylosisUnilateral ankylosis
Bilateral ankylosisBilateral ankylosis

CONCLUSIONCONCLUSION
Human growth and developmentHuman growth and development
encompasses physical, mental,encompasses physical, mental,
psychological, social and moralpsychological, social and moral
development. Growth is the interplaydevelopment. Growth is the interplay
between several factors.between several factors.
Thus understanding growth andThus understanding growth and
development of mandible and TMJ is adevelopment of mandible and TMJ is a
complex process which requires an abilitycomplex process which requires an ability
to visualize and conceptualize it.to visualize and conceptualize it.

REFERENCESREFERENCES
Essential of facial growth – DONALD H. ENLOWEssential of facial growth – DONALD H. ENLOW
Introduction to craniofacial biology – DAVIDIntroduction to craniofacial biology – DAVID
S.CARLSONS.CARLSON
Craniofacial development –SPERBERCraniofacial development –SPERBER
Growth of the craniofacial skeleton – MOYERSGrowth of the craniofacial skeleton – MOYERS
Contemporary orthodontics – WILLIAM R.Contemporary orthodontics – WILLIAM R.
PROFFITPROFFIT
Oral histology – TEN CATE’SOral histology – TEN CATE’S

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Pre natal and post natal growth of mandible and tmj

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