8/9/2019 Development of Jaws
1/43
DEVELOPMENT OF JAWS
Dr. Ayesha A
PG Res
Dept. of Prosthodo
Army Medical Co
National Universit of Sciences and Technolo N
8/9/2019 Development of Jaws
2/43
JAWS
•Mandible
• Maxilla
8/9/2019 Development of Jaws
3/43
MECKEL’S CARTILAG
8/9/2019 Development of Jaws
4/43
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
8/9/2019 Development of Jaws
5/43
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 $and of mesenchyme
8/9/2019 Development of Jaws
6/43
MANDIBULAR NERVE• Nerve of the %st arch
• /ranch of Trigeminal nerve CN 0!• 1as a close relationship to Mec*el2s cartilage
• Begins two-third of the way along the length of the cartilage
• Divides into Lingual and Inferior Alveolar branches
•Lingual nerve runs on the medial aspect of the cartilage, while inferior alveo
the lateral aspect
• Inferior alveolar nerve (I!" further divides into
• Incisor/ incisive nerve
•
Mental nerve
8/9/2019 Development of Jaws
7/43
MANDIBLE
8/9/2019 Development of Jaws
8/43
MANDIBLE
•
/ody• Ram)s
• Alveolarprocess
8/9/2019 Development of Jaws
9/43
+th 'ee* ofem$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
8/9/2019 Development of Jaws
10/43
8/9/2019 Development of Jaws
11/43
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.
8/9/2019 Development of Jaws
12/43
Tro)gh of
$one
Comes into approimation 'ith the tro)gh ofopposite side
The t'o centers of ossi,cation remain separated at the7 symphysis2
/one forms over thenerve
3ateral and medial plates are (oined
Tro)gh converts into a
canal
8/9/2019 Development of Jaws
13/43
/ac*'ard etension of8ssi,cation
8n the lateral aspect of Mec*el2scartilage
To the point 'here Mandi$)lar nerve divides into ling)al
and #AN
8/9/2019 Development of Jaws
14/43
&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
8/9/2019 Development of Jaws
15/43
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
8/9/2019 Development of Jaws
16/43
MANDIBLE
•
Rudimenta! mandi"#e• #ormed by $% wee&s of I' life
• ntirely by intramembranous ossification
• )ith little or no involvement of Mec&el*s cartilage
• +as neural, alveolar and muscular elements
• rowth is assisted by secondary cartilages*
8/9/2019 Development of Jaws
17/43
8/9/2019 Development of Jaws
18/43
8/9/2019 Development of Jaws
19/43
GROWT$ OF MANDIBLE
•
rowth until birth is influenced by the appearance of• 03 secondary cartilages (aka growth cartilages)
• Muscular attachments
8/9/2019 Development of Jaws
20/43
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
8/9/2019 Development of Jaws
21/43
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
8/9/2019 Development of Jaws
22/43
8/9/2019 Development of Jaws
23/43
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
8/9/2019 Development of Jaws
24/43
MA2ILLA
8/9/2019 Development of Jaws
25/43
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
8/9/2019 Development of Jaws
26/43
#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$erior"y To form the
frontal process
Tro)gh of
8/9/2019 Development of Jaws
27/43
Tro)gh of$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
8/9/2019 Development of Jaws
28/43
8/9/2019 Development of Jaws
29/43
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
8/9/2019 Development of Jaws
30/43
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
8/9/2019 Development of Jaws
31/43
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
8/9/2019 Development of Jaws
32/43
CONGENITAL DEFECT
8/9/2019 Development of Jaws
33/43
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<
8/9/2019 Development of Jaws
34/43
CAUSES OF CONGENITAL DEFECTS
• +ereditary #actors
• nvironmental #actors=
1. Infectious Agents
2. X-ray Radiation
3. Drugs
4. Hormones
5. Nutritional Deciencies
8/9/2019 Development of Jaws
35/43
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
8/9/2019 Development of Jaws
36/43
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
8/9/2019 Development of Jaws
37/43
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
8/9/2019 Development of Jaws
38/43
Te((ie C#a((i)i*ati+n
8/9/2019 Development of Jaws
39/43
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
8/9/2019 Development of Jaws
40/43
Van de Meu#en *#a((i)i*ati+n
8/9/2019 Development of Jaws
41/43
CLEFTS
8/9/2019 Development of Jaws
42/43
CLEFT LIP AND PALATE
8/9/2019 Development of Jaws
43/43
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