Growth of Mandible Ortho

8/9/2019 Growth of Mandible Ortho

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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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Growth of Mandible Ortho