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DEFINATIONDEFINATION
Growth was concieved by anGrowth was concieved by ananatomist, born to a biologist, delivered by aanatomist, born to a biologist, delivered by aphysician, left on a chemist doorstep, andphysician, left on a chemist doorstep, and
adopted by a physiologist.At an early ageadopted by a physiologist.At an early age-- shesheeloped with a statistician, divorced him for aeloped with a statistician, divorced him for apsycologist, and is now wooed, alternativelypsycologist, and is now wooed, alternativelyand concurrently, by an endrocrinologist, aand concurrently, by an endrocrinologist, abiochemist,a physicist, a mathematician, anbiochemist,a physicist, a mathematician, anorthodontist, a eugenicist and the childrensorthodontist, a eugenicist and the childrensbureau.bureau.
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Growth and development of an indiviualGrowth and development of an indiviualis divided into two periodsis divided into two periods--
Prenatal periodPrenatal period
Post natal periodPost natal period
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THE PRENATAL LIFE IS DIVIDEDTHE PRENATAL LIFE IS DIVIDEDINTOTHREE PERIODSINTOTHREE PERIODS
1.PERIOD OF THEOVUM1.PERIOD OF THEOVUM
2.PERIOD OF THEEMBRYO2.PERIOD OF THEEMBRYO
3.PERIOD OF THE FETUS3.PERIOD OF THE FETUS
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PRE NATAL GROWTH PHASEPRE NATAL GROWTH PHASE
About theAbout the fourthfourth
week of intrauterine lifeweek of intrauterine life,,
thethepharyngealpharyngeal
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.
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Each of these five arches containEach 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.
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INTRAMEMBRANOUS BONEINTRAMEMBRANOUS BONE
FOR
MATIONFOR
MATIONThe first structure toThe first structure to
develop in thedevelop in the
primodium of the lowerprimodium of the lower
jaw is thejaw is the mandibularmandibulardivision ofdivision of trigeminaltrigeminal
nervenerve that precedes thethat precedes the
mesenchymalmesenchymal
condensation formingcondensation formingthe first [mandibular]the first [mandibular]
arch.arch.
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At around 36At around 36 --38 days38 days of intrauterine life thereof intrauterine life there
isis ectomesenchymal condensationectomesenchymal condensation
SomeSome mesenchymal cellsmesenchymal cells enlarges , acquire aenlarges , acquire abasophilic cytoplasm and formbasophilic cytoplasm and form osteoblastsosteoblasts
T
hese osteoblasts secrete a gelatinous matrixT
hese osteoblasts secrete a gelatinous matrixcalledcalled osteoidosteoid and result inand result in ossification of anossification of anosteogenic membrane.osteogenic membrane.
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The resultingThe resulting intramembranous boneintramembranous bone lies lateral to meckelslies lateral to meckelscartilage 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 ossification centrea single ossification centrefor each half of the mandible arises in thefor each half of the mandible arises in thebifurcation of inferiorbifurcation of inferior
alveolar nerve into mental and incisive branchesalveolar nerve into mental and incisive branches
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DuringDuring seventh week of intrauterine lifeseventh week of intrauterine lifebonebone
begin to develop lateral tobegin to develop lateral to meckels cartilagemeckels 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.
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Ossification stops at a piont , which later becomeOssification stops at a piont , which later become mandibularmandibularlingulalingula, 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 ofsphenoidsphenoid..
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
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ENDROCHONDRAL BONEENDROCHONDRAL BONE
FOR
MATIONFOR
MATIONEndrocondral bone formation is seen in 3Endrocondral bone formation is seen in 3
areas of mandibleareas of mandible--
1)1) The condylar processThe condylar process2)2) The coronoid processThe coronoid process
3)3) The mental processThe mental process
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THE CONDYLARPROCESSTHE CONDYLARPROCESS--
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 weekit 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.
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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.
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THE CORONOID PROCESSTHE CORONOID PROCESS--
SecondarySecondary
accessory cartilageaccessory cartilage appear in region ofappear in region of
coronoid process at aboutcoronoid process at about 1010-- 14 week of14 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.
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THE MENTAL REGIONTHE 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 ossifycompletely.completely.
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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 noarticular 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 midlineof symphysis to separate right & left mandibularof symphysis to separate right & left mandibularbodies.bodies.
At fourth month of age and end of first yearAt fourth month of age and end of first yearsymphysial cartilage is replaced by bonesymphysial cartilage is replaced by bone
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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 itslateral surface.lateral surface.
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After first year of life these changes occursAfter 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 onposterior border of theposterior border of theramus 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
anterioranterior-- posterior dimension of ramus.posterior dimension of ramus.
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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 atposterior border in anposterior border in an expanding V patternexpanding V pattern..
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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
interinter--ramus dimension.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 toaccommodate the larger permanent teeth.accommodate the larger permanent teeth.
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ScottScott divides the mandible into three basicdivides the mandible into three basic
types of bonetypes of bone
1)1) BasalBasal
2)2) MuscularMuscular
3)3) Alveolar Alveolar Basal portionBasal portion is tube like central foundation runningis tube like central foundation running
from condyle to the symphysis.from condyle to the symphysis.
Muscular portionMuscular portion [gonial angle &coronoid process][gonial angle &coronoid process]
is under influence ofis under influence ofmasseter, 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.
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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 forflattening of gonial angleflattening of gonial angle
and reduction of the coronoid process.and reduction of the coronoid process.
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MOSS say that the mandible as a group of microskeleton unitMOSS say that the mandible as a group of microskeleton unit
Coronoid processC
oronoid 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.
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THE CHINTHE CHIN
Enlow & harrisEnlow & harris feel that chin isfeel that chin isassociated with a generalised corticalassociated with a generalised cortical
recession in the flattened regions positionedrecession in the flattened regions positioned
between the canine teeth.T
he process involvesbetween the canine teeth.T
he process involvesa 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.
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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 inshape 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.
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