Growth of mandible

www.indiandentalacademy.comwww.indiandentalacademy.com

DEFINATIONDEFINATION
““Growth was concieved by anGrowth was concieved by an
anatomist, born to a biologist, delivered by aanatomist, born to a biologist, delivered by a
physician, left on a chemist doorstep, andphysician, left on a chemist doorstep, and
adopted by a physiologist.At an early age- sheadopted by a physiologist.At an early age- she
eloped with a statistician, divorced him for aeloped with a statistician, divorced him for a
psycologist, and is now wooed, alternativelypsycologist, and is now wooed, alternatively
and concurrently, by an endrocrinologist, aand concurrently, by an endrocrinologist, a
biochemist,a physicist, a mathematician, anbiochemist,a physicist, a mathematician, an
orthodontist, a eugenicist and the children’sorthodontist, a eugenicist and the children’s
bureau”.bureau”.

Growth and development of an indiviualGrowth and development of an indiviual
is divided into two periods-is divided into two periods-
 Prenatal periodPrenatal period
 Post natal periodPost natal period

THE PRENATAL LIFE IS DIVIDEDTHE PRENATAL LIFE IS DIVIDED
INTO THREE PERIODS –INTO THREE PERIODS –
1.PERIOD OF THE OVUM1.PERIOD OF THE OVUM
2.PERIOD OF THE EMBRYO2.PERIOD OF THE EMBRYO
3.PERIOD OF THE FETUS3.PERIOD OF THE FETUS

PRE NATAL GROWTH PHASEPRE NATAL GROWTH PHASE
 About theAbout the fourthfourth
week of intrauterine lifeweek of intrauterine life,,
thethe pharyngealpharyngeal
archesarches are laid downare laid down
 The first arch isThe first arch is
called thecalled the mandibularmandibular
archarch and theand the
second arch thesecond arch the hyoidhyoid
arch.arch.

Each of these five arches contain -Each of these five arches contain -
1.1. A central cartilageA central cartilage rod that form the skeletonrod that form the skeleton
of the arch.of the arch.
2.2. A muscular componentA muscular component termed astermed as
bronchomerebronchomere
3.3. A vascular componentA vascular component..
4.4. A neural element.A neural element.

INTRAMEMBRANOUS BONEINTRAMEMBRANOUS BONE
FORMATIONFORMATION
The first structure toThe first structure to
develop in thedevelop in the
primodium of the lowerprimodium of the lower
jaw is thejaw is the mandibularmandibular
division ofdivision of trigeminaltrigeminal
nervenerve that precedes thethat precedes the
mesenchymalmesenchymal
condensation formingcondensation forming
the first [mandibular]the first [mandibular]
arch.arch.

At around 36 -38 daysAt around 36 -38 days of intrauterine life thereof intrauterine life there
isis ectomesenchymal condensationectomesenchymal condensation
SomeSome mesenchymal cellsmesenchymal cells enlarges , acquire aenlarges , acquire a
basophilic cytoplasm and formbasophilic cytoplasm and form osteoblastsosteoblasts
These osteoblasts secrete a gelatinous matrixThese osteoblasts secrete a gelatinous matrix
calledcalled osteoidosteoid and result inand result in ossification of anossification of an
osteogenic membrane.osteogenic membrane.

The resultingThe resulting intramembranous boneintramembranous bone lies lateral to meckel’slies lateral to meckel’s
cartilage of first [mandibular ] arch.cartilage of first [mandibular ] arch.
In theIn the sixth week of the intrauterine lifesixth week of the intrauterine life a single ossificationa single ossification
centre for each half of the mandible arises in thecentre for each half of the mandible arises in the bifurcation ofbifurcation of
inferior alveolar nerve into mental and incisive branchesinferior alveolar nerve into mental and incisive branches

DuringDuring seventh week of intrauterine lifeseventh week of intrauterine life bonebone
begin to develop lateral tobegin to develop lateral to meckel’s cartilagemeckel’s cartilage
& continues until the posterior aspect is& continues until the posterior aspect is
covered with bonecovered with bone
BetweenBetween eigth & tewelth week of intrauterineeigth & tewelth week of intrauterine
lifelife mandibular growth accelerate , as a resultmandibular growth accelerate , as a result
mandibular length increses.mandibular length increses.

Ossification stops at a piont , which later becomeOssification stops at a piont , which later become mandibularmandibular
lingulalingula, the remaining part of meckels cartilage continues to, the remaining part of meckels cartilage continues to
formform sphenomandibular ligament & spinous process ofsphenomandibular ligament & spinous process of
sphenoidsphenoid..
Secondary accseeory cartilageSecondary accseeory cartilage appear between tenth &appear between tenth &
fourteenth week of intrauterine life to formfourteenth week of intrauterine life to form head of condyle ,head of condyle ,
part of coronoid process & mental protuberancepart of coronoid process & mental protuberance

ENDROCHONDRAL BONEENDROCHONDRAL BONE
FORMATIONFORMATION
Endrocondral bone formation is seen in 3Endrocondral bone formation is seen in 3
areas of mandible-areas of mandible-
1)1) The condylar processThe condylar process
2)2) The coronoid processThe coronoid process
3)3) The mental processThe mental process

THE CONDYLAR PROCESS-THE CONDYLAR PROCESS-
At fifth week ofAt fifth week of
intruterine lifeintruterine life , an area of mesenchymal, an area of mesenchymal
condensation is seen above thecondensation is seen above the ventral part ofventral part of
developing mandible.developing mandible.
At aboutAt about tenth weektenth week it develops init develops in cone shapedcone shaped
cartilage.cartilage.
It migrate inferior & fuses withIt migrate inferior & fuses with mandibular ramusmandibular ramus atat
aboutabout 4 month.4 month.

This cone shaped cartilageThis cone shaped cartilage is replaced by bone but itsis replaced by bone but its
upper end persists acting asupper end persists acting as growth cartilage & articulargrowth cartilage & articular
cartilage.cartilage.

THE CORONOID PROCESS-THE CORONOID PROCESS-
SecondarySecondary
accessory cartilageaccessory cartilage appear in region ofappear in region of
coronoid process at aboutcoronoid process at about 10- 14 week of10- 14 week of
intrauterine life.intrauterine life.
This cartilage become incorporated intoThis cartilage become incorporated into
expandingexpanding intramembranous bone of ramusintramembranous bone of ramus &&
dissapear before birth.dissapear before birth.

THE MENTAL REGION-THE MENTAL REGION-
In mental region , onIn mental region , on
either side of symphysis , one or two smalleither side of symphysis , one or two small
cartilage appear and ossify incartilage appear and ossify in seventh week ofseventh week of
intrauterine lifeintrauterine life to becometo become mental ossicles.mental ossicles.
These ossicles become incorporated intoThese ossicles become incorporated into
intramembranous boneintramembranous bone when symphysis ossifywhen symphysis ossify
completely.completely.

POST NATAL GROWTH PHASEPOST NATAL GROWTH PHASE
At birthAt birth the two rami of the mandible are short ,the two rami of the mandible are short ,
condylar development is minimum and there is nocondylar development is minimum and there is no
articular eminence in glenoid fossa. A thin layer ofarticular eminence in glenoid fossa. A thin layer of
fibrocartilage & connective tissue existsfibrocartilage & connective tissue exists at the midlineat the midline
of symphysis to separate right & left mandibularof symphysis to separate right & left mandibular
bodies.bodies.
At fourth month of age and end of first yearAt fourth month of age and end of first year
symphysial cartilage is replaced by bonesymphysial cartilage is replaced by bone

During first year of lifeDuring first year of life
appositional growth isappositional growth is
active at alveolaractive at alveolar
border,border, at distal &at distal &
superior surfaces of thesuperior surfaces of the
ramus, at the condyle,ramus, at the condyle,
along the lower borderalong the lower border
of mandible and on itsof mandible and on its
lateral surface.lateral surface.

After first year of life these changes occurs -After first year of life these changes occurs -
 Mandibular growth become more selective , condyleMandibular growth become more selective , condyle
shows considerable activities,shows considerable activities, mandible moves andmandible moves and
grows downward & forward.grows downward & forward.
 Appositional growth occurs onAppositional growth occurs on posterior border of theposterior border of the
ramus and on the alveolar process.ramus and on the alveolar process.
 Resorption occurs along theResorption occurs along the anterior border of ramusanterior border of ramus
lenthening the alveolar border & maintaining thelenthening the alveolar border & maintaining the
anterior- posterior dimension of ramus.anterior- posterior dimension of ramus.

 Gonial angleGonial angle changes after little muscle activity.changes after little muscle activity.
 Transverse dimension is mainly due to growth atTransverse dimension is mainly due to growth at
posterior border in anposterior border in an expanding V patternexpanding V pattern..

 The two rami alsoThe two rami also diverge outwarddiverge outward from below tofrom below to
above so that additive growth atabove so that additive growth at coronoid notch ,coronoid notch ,
coronoid process &condylecoronoid process &condyle also increses the superioralso increses the superior
inter-ramus dimension.inter-ramus dimension.
 Alveolar process of mandibleAlveolar process of mandible growsgrows upward &upward &
outwardoutward on an expanding arc. This permit dental arc toon an expanding arc. This permit dental arc to
accommodate the larger permanent teeth.accommodate the larger permanent teeth.

ScottScott divides the mandible into three basicdivides the mandible into three basic
types of bone –types of bone –
1)1) BasalBasal
2)2) MuscularMuscular
3)3) AlveolarAlveolar
 Basal portionBasal portion is tube like central foundationis tube like central foundation
running from condyle to the symphysis.running from condyle to the symphysis.
 Muscular portionMuscular portion [gonial angle &coronoid process][gonial angle &coronoid process]
is under influence ofis under influence of masseter, internal pterygoid &masseter, internal pterygoid &
temporal muscle.temporal muscle. They determine the ultimate formThey determine the ultimate form
of the mandible in these areas.of the mandible in these areas.

 Alveolar portionAlveolar portion exists to hold the teeth &exists to hold the teeth &
gradually resorbed in the event of tooth loss.gradually resorbed in the event of tooth loss.
Reduced muscular activityReduced muscular activity
would account forwould account for flattening of gonial angleflattening of gonial angle
and reduction of the coronoid process.and reduction of the coronoid process.

MOSS say that the mandible as a group of microskeletonMOSS say that the mandible as a group of microskeleton
unit –unit –
 Coronoid processCoronoid process as one skeleton unit under influence of temporalis.as one skeleton unit under influence of temporalis.
 Gonial angleGonial angle is another skeleton unit under influence of massetor &is another skeleton unit under influence of massetor &
internal pterygoid muscles.internal pterygoid muscles.
 Alveolar processAlveolar process is under the influence of the dentition.is under the influence of the dentition.
Basal tubular portion of mandibleBasal tubular portion of mandible serves as protection for theserves as protection for the
mandibular canal and follows amandibular canal and follows a logarithim spirallogarithim spiral in its downward &in its downward &
forward movement from beneath the cranium.forward movement from beneath the cranium.

THE CHINTHE CHIN ––
Enlow & harrisEnlow & harris feel that chin isfeel that chin is
““associated with a generalised corticalassociated with a generalised cortical
recession in the flattened regions positionedrecession in the flattened regions positioned
between the canine teeth. The process involvesbetween the canine teeth. The process involves
a mechanism of endosteal cortical growtha mechanism of endosteal cortical growth.”.”
 On lingual surface, behind the chin heavyOn lingual surface, behind the chin heavy
periosteal growthperiosteal growth occurs , with the denseoccurs , with the dense
lamellar bone merginglamellar bone merging and overlaping on theand overlaping on the
labial side of the chin.labial side of the chin.

 In male ,In male , thethe apposition of the boneapposition of the bone atat
symphysissymphysis seems to be about the last change inseems to be about the last change in
shape during the growing period. This changeshape during the growing period. This change
is much less apparent inis much less apparent in the females.the females.

Growth of mandible

Recomendados

Recomendados

Mais conteúdo relacionado

Mais procurados

Mais procurados (20)

Destaque

Destaque (13)

Semelhante a Growth of mandible

Semelhante a Growth of mandible (20)

Mais de Indian dental academy

Mais de Indian dental academy (20)

Último

Último (20)

Growth of mandible