بسم الله الرحمن الرحيم

Growth Changes Of MandibleDone By :

Rahma Mohammed Younis

Mandible Growth

o Prenatal developmento Postnatal development

Prenatal growth of madible

Cartilage and bones of mandibular form from

“Embryonic neural crest cells

Thickening develop in lateral & ventral aspect of cranial most part of foregut called pharyngeal/branchial arches.

During 4th week

Later pharyngeal arches grow. First Branchial arch called MANDIBULAR ARCH . It grows ventro-medially cranial to main part of the

arch which is called mandibular process.

Meckel’s cartilage

Primary cartilage of first pharyngeal arch is Meckel’s cartilage helps in formation of lower jaw.Meckel’s cartilage first appear at 6th week IUL.

Centre of ossification

Ossification starts at the division of mental and incisive branch of inferior alveolar nerve lateral to meckel’s cartilage around 6th week IUL.

From center of ossification bone formation spreads:

Anteriorly - midline Posteriorly - where mandibular nerve divided into

lingual and inferior alveolar branch.

Bone formation spreads rapidly and surrounds the inferior alveolar nerve to form mandibular canal.

Intramembranous ossification spreads in anterior and posterior direction forms the Body & Ramus of the mandible.

Centre of ossification

Ossification spread posteriorly to form ramus of mandible, turning away from meckel’s cartilage.

Ossification stops at site where it whould be Lingula.

Major cartilage disappears .

secondary cartilage :

Between 10th and 14th week three secondary cartilage develops:

I. Condylar cartilage – largest and appear beneath the fibrous articular layer of future condyle.

II. Coronoid cartilage - seen associated with coronoid process.

SECONDARY CARTILAGES IN MANDIBULAR DEVELOPMENT

Mandible develops largely by

intramembranous ossification and by endochondral ossification in :

1. Condylar process

2. Coronoid process

3. Mental region

Develops from condylar cartilage appear as

separate area of mesenchymal condensation along developing mandible around 8th week.

This area develop in cone-shaped cartilage around 10th week.

By the 14th week first evidence of endochondral bone formation appear in condylar region.

CONDYLAR PROCESS

• Cartilage fuses with mandibular ramus around 4th month.

Cartilage replaced by bone but upper end persists in adulthood acting as Growth and Articular cartilage.

Condylar growth rate increases at puberty .

Peaks between 12 to 14 years of age.

Secondary cartilage appears in coronoid

process around 10-14th week.

Cartilage grow as a response of developing temporalis muscle.

Coronoid cartilage become incorporated into expanding intramembranous bone of ramus and disappear before birth.

CORONOID PROCESS

Throughout intrauterine life left and right

mandible are not fused at midline.

Joined by connective tissue at midline.

On either side of symphysis, symphyseal cartilage appear between 10th & 14th week postconception.

MENTAL REGION

Ossify in 7th month to form mental ossicles in

fibrous tissue of symphysis.

Mental ossicles fuses with mandibular body at the end of first year after birth.

MENTAL REGION

POST NATAL DEVELOPMENT OF MANDIBLE

POST NATAL DEVELOPMENT OF MANDIBLE•Mandible undergoes greatest amount of postnatal growth of all facial bones.

GROWTH AT CONDYLE

Major site of mandibular growth.

Growth of condylar cartilage increases length & height of mandible.

Interstitial & appositional growth within plate produce linear movement of condyle in upward & backward direction towards temporal bone.

.

•Cartilage plate moves by growth on one side & bone replacement on other side.

•As condylar growth cartilage moves obliquely upward & posteriorly

- entire head of condyle moves in same direction by forming new condyle behind moving cartilage.

•This process is continuous & condyle moves by growth.

•Formation of bone within condyle causes mandible rami to grow Upward & Backward

•Displacing entire mandible in Downward & Forward direction.

CONDYLAR NECK

•As ramus elongates, former level occupied by head remodeled into upper neck

•Buccal & lingual cortical plates moves inward towards each other results in reduced transverse dimension of neck.

Inward growth of buccal & lingual cortices

SIGMOID NOTCH

•The height of the ramus increased by :

- addition of new bone along the entire superior surface of the sigmoid notch only at lingual surface.

SIGMOID NOTCH

• Bone deposition – • post. Border of • coronoid process

• Bone resorption -

• ant. Face of neck.

CORONOID PROCESS•To produce backward movement of ramus : - Ant. Margin of ramus & coronoid process, must undergo progressive removal.

-Forward facing ant. Border of coronoid process is resorptive around temporal crest on lingual side.-Greater portion of lingual surface is depositive -Entire buccal surface is resorptive.

Light stippling – bone depositionDark stippling – bone resorption

•Coronoid process follows “v” principle.

•Movement of this v towards its wider ends.

•Bone Deposition - inner surface

•Bone Resorption - outer surface

•Which bring about growth in upward & backward direction.

.

Vertical section of coronoid process

•BONE DEPOISITION -

lingual surface (+ +)

•BONE RESORPTION -

buccal surface (- -)

GROWTH AT RAMUS•Ramus moves backward in relation to body of mandible

•Post. displacement of ramus converts the formal ramal bone in post. Part of body of mandible.

•Body of mandible lengthens & increase in mandibular arch to accommodate erupting permanent molars.

GROWTH AT RAMUS

• Bone deposition (++) post. border of Ramus

• Bone resorption (--) ant. border of Ramus

• Leads to AP growth of mandibe

CHIN•Growth of chin occurs at puberty .•Chin become prominent at puberty especially in males, by selective remodelling.•Alveolar region growths posteriorly.

•Mental protuberance growths forwardly.

•Which brings increase projection of chin.

•Bone deposition - mental protuberance.

•Bone resorption - alveolar region above the prominence, creating a concavity.

ALVEOLAR PROCESS

•Alveolar growth occurs around tooth buds.

•As teeth develop & begin to erupt, alv. Process increases in size & height.

•Continued growth of alveolar Bone increases height of mandibuar body.

• Alveolar Process growths upward & outward on expanding arch.

INFANTS

Mental foramen - near lower border Mandibular canal - lower border of

body of mandible Angle of mandible - obtuse around

140* or more

Age changes in mandible

• Mental foramen - midway of

upper & lower border.

• Mandibular canal - runs parallel

with mylohyoid line.

• Angle of mandible - 110* - 120*

ADULTS

OLD AGE

Mandibular foramen - near alv. Bone Mandibular canal - near alv. Bone Angle of mandible - obtuse 140*

*Thank You