Development of Jaws

8/9/2019 Development of Jaws

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DEVELOPMENT OF JAWS

Dr. Ayesha A

PG Res

Dept. of Prosthodo

Army Medical Co

National Universit of Sciences and Technolo N


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JAWS

•Mandible

• Maxilla


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MECKEL’S CARTILAG


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MECKEL’S CARTILAGE

•

Cartilage of the %st

pharyngeal arch

• &orms lo'er (a' in primitive verte$rates

• #n h)mans

•

a close positional relationship to the developing man• Ma*es no direct contri$)tion

• Delimits the region 'here $one formation 'ill ta*e pl


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MECKEL’S CARTILAGE

•

DEVELOPMENT• At + 'ee*s

• A solid hyaline cartilagino)s rod

• S)rro)nded $y a ,$rocell)lar caps)le

• -tends from the developing ear region otic caps)le! to th

of the f)sed mandi$)lar processes

• T'o cartilages" one on each side of midline" do not meet at

• Separated $y a thin $and of mesenchyme


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MANDIBULAR NERVE• Nerve of the %st arch

• /ranch of Trigeminal nerve CN 0!• 1as a close relationship to Mec*el2s cartilage

• Begins two-third of the way along the length of the cartilage

• Divides into Lingual and Inferior Alveolar branches

•Lingual nerve runs on the medial aspect of the cartilage, while inferior alveo

the lateral aspect

• Inferior alveolar nerve (I!" further divides into

• Incisor/ incisive nerve

•

Mental nerve


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MANDIBLE


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MANDIBLE

•

/ody• Ram)s

• Alveolarprocess


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+th 'ee* ofem$ryonic life

3ateral aspect of Mec*el2scartilage

Angle formed $y the division of #AN into its 4$ranches

Condensation ofmesenchyme

5th 'ee* of #Ulife

#ntra6mem$rano)s ossi,cation in thecondensation

&orms the ,rst $one of the7 2


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Centre of8ssi,cation

Spread of /oneformation

Anteriorly 9 to themidline

/one forms along the lateral aspect ofcartilage

&orms a tro)gh 'ith lateral andmedial plates

The t'o plates )nite $eneath theincisor nerve

Tro)gh etends to themidline

Posteriorly 9division of mnerve.


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Tro)gh of

$one

Comes into approimation 'ith the tro)gh ofopposite side

The t'o centers of ossi,cation remain separated at the7 symphysis2

/one forms over thenerve

3ateral and medial plates are (oined

Tro)gh converts into a

canal


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/ac*'ard etension of8ssi,cation

8n the lateral aspect of Mec*el2scartilage

To the point 'here Mandi$)lar nerve divides into ling)al

and #AN


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&rom the point of division of Mandi$)lar n. tothe midline

Medial and lateral alveolar plates of

$one develop

#n relation to the forming toothgerms

S)$divide the tro)gh of

$one

Teeth occ)py individ)alcompartments

Compartments enclosed $y gro'th of $one over thetooth germs

BODY OF THEMANDIBLE


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Rapid spread of ossi,cation posteriorly into themesenchyme

T)rns a'ay from the Mec*el2scartilage

Point of divergence 9 mar*ed $y 7ling)la2 inad)lt mandi$le

3ing)la 9 point 'here #AN enters the $ody ofthe mandi$le

RAMUS OF THE MANDIBLE


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MANDIBLE

•

Rudimenta! mandi"#e• #ormed by $% wee&s of I' life

• ntirely by intramembranous ossification

• )ith little or no involvement of Mec&el*s cartilage

• +as neural, alveolar and muscular elements

• rowth is assisted by secondary cartilages*


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GROWT$ OF MANDIBLE

•

rowth until birth is influenced by the appearance of• 03 secondary cartilages (aka growth cartilages)

• Muscular attachments


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SECONDAR% CARTILAGES

•

.alled as secondary* to distinguish from the primary Mec&el*

• +ave a different histologic structure

• +ave larger cells and less inter-cellular matrix

1 !ondylar !artilage

" !oronoid !artilage

3 #ym$hyseal !artilage


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SECONDAR% CARTILAGES,) -ONDYLAR -ARTILA.E

• ppears at $/ wee&s of development

• #orms a cone0carrot-shaped mass that occupies the developing ram

• 1uic&ly converted to bone 2 by endochondral ossification

• t /% wee&s of I' life

• only a thin layer of cartilage remains in the condylar head

• 3emnant cartilage

• Persists till 4nd decade of life age %: 9 4: years!

• Aids in post6natal gro'th of mandi$le

• Similar to the epiphyseal cartilage of long $ones


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SECONDAR% CARTILAGES

0) SYMPHYSEAL -ARTILA.E• %/ in number

• ppear in the connective tissue between the two ends of Mec&el*s

• ntirely independent of the Mec&el*s cartilage

• 6ssified within the first year after birth

1) OTHER• 5mall island of cartilage

• ppear in developing alveolar processes

• 7ariable and transient structures


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MA2ILLA


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MA&ILLA ' ANATOM%

•

/ody 9 large and pyramidal• Processes

• &rontal

• ;ygomatic

• Alveolar

•

Palatine

• 1o)ses the largest sin)s 9 maillary sin)s

Closely associated 'ith cartilage of


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#n the mesenchyme of the maillary process ofthe %st arch

Closely associated 'ith cartilage ofnasal caps)le

Angle formed $y the division #nferior 8r$ital Nerve into anteros)pealveolar nerve

Centre of ossi,cation 5th 'ee*

/one formationspreads

Posterior"y$elo' the or$it to'ard

the developing< oma

Anterior"y To'ards the f)t)re

incisor region

Su$erior"y To form the

frontal process

Tro)gh of


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Tro)gh of$one

&orms for the infraor$italnerve

Do'n'ard etension of $one fromthe tro)gh

Lter" "(eo"r $"te for the maillarytooth germs

Me!i" "(eo"r $"te 9 develops from ()nction of palatal processof forming mailla

3ateral and medial plates (oin to form a tro)gh aro)ndmaillary tooth germs

Tooth germs enclosed in $ony crypts $y gro'th of$one over them


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MA&ILLA• At 'irt%3 mxi"" %s

• =ell mar*ed frontal process

• /ody 9 'ith little more than the alveolar process containing too

• Small $)t disting)isha$le


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MA&ILLA

• SE-ONDARY -ARTILA.E

• 8ygomatic or malar cartilage

• ppears in the developing 8ygomatic process

• dds considerably to the development of maxilla for a short period of tim


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COMMON FEATURES OF JAW DEVELOP

i9 Membranous ossification

ii9 Begin from a single ossification center related to a nerve

iii9 #orm a neural element related to the nerve

iv9 #orm an alveolar element related to the developing teeth

v9 Develop secondary cartilages to assist in their growth


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CONGENITAL DEFECT


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EMBR%OGENESIS

• complicated and delicately balanced process

• Between 4th and :th wee&s of development

• Morphogenesis

• +istodifferentiation

• #ormation of face, mouth, tongue and associated structures

• ny malfunction* produces ;congenital defects<


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CAUSES OF CONGENITAL DEFECTS

• +ereditary #actors

• nvironmental #actors=

1. Infectious Agents

2. X-ray Radiation

3. Drugs

4. Hormones

5. Nutritional Deciencies


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TIMING OF T$E FACTORS

• D)ring the ,rst ? 'ee*s

• !"tensi#e damage of cells $ deat% of em&ryo occurs

• If only a fe' cells are damaged $ normal (roliferation

eliminates t%e damage

• /et'een ? and @ 'ee*s 1istodierentiation B or

dierentiation!

• )alformations


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CLEFTS

• Malformation of a part of the face

• May appear as an opening or gap

• A collective term 9 $one" soft6tiss)es" s*in etc. a

aected


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CLASSIFICATION• Te((ie C#a((i)i*ati+n

• .lefts are numbered % to $49

• $> different types of clefts can be put into 4 groups, based on their

• Midline clefts

• %aramedian clefts

• &r'ital clefts

• Lateral clefts

• Describes the clefts at soft tissue level as well as at bone level9


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Te((ie C#a((i)i*ati+n


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CLASSIFICATION• Van de Meu#en *#a((i)i*ati+n

• based on where the development arrest occurs in the embryogenesis

• can be divided in four different location groups=

• Internasal

• !asal

• !asalmaxillar

• Maxillar

• Median

• Lateral clefts


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Van de Meu#en *#a((i)i*ati+n


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CLEFTS


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CLEFT LIP AND PALATE


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CAUSES OF CLEFT PLATE• &ail)re of palatine shelves and sept)m to contact each ot

•

*ac+ of gro't%• Distur&ance in t%e mec%anism of s%elf ele#ation

• &ail)re of shelves and sept)m to f)se after contact has $e

• !(it%elium co#ering t%e s%el#es does not resor&

• R)pt)re after f)sion of shelves has occ)rred

• Defective merging and consolidation of the mesenchyme

shelves

Development of Jaws

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