Dr Arunavo Nandy ( Pgt 1st year Department of Orthodontics and Dentofacial Orthopaedics Kothiwal Dental College and Research Centre)

1. GROWTH OF MANDIBLE
Dr Arunavo Nandy
(1st Year Orthodontics PGT)
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2. CONTENT
• Introduction
• Anatomy of Mandible
• Prenatal Growth of Mandible
• Postnatal Growth Of Mandible
• Rotation of Mandible
• Growth Timing of Mandible
• Developmental Anomalies
• References
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3. INTRODUCTION
• Mandible or the lower jaw is the largest and the
strongest bone of the face.
• Mandible is derived from the first pharyngeal arch
• Mandible is a horseshoe-shaped bone.
• Mandible lodges the tooth and a pair of rami which
projects upwards from the posterior end of the body
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4. ANATOMY OF MANDIBLE
Mandible consists of the following parts
 BODY
 RAMUS
 CONDYLAR PROCESS
 CORONOID PROCESS
 ALVEOLAR PROCESS
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5. 5

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7. BODY:- Outer surface :-
 Symphysis Menti
 Mental Protuberance
Mental Foramen
Oblique Line
Incisive fossa
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Inner Surface :-
Mylohyoid Line
Mylohyoid groove
Genial Tubercles
Submandibular Fossa
Sublingual Fossa
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• Upper Border :- Alveolar Process
• Lower border :- Digastric fossa
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• RAMUS
2 surfaces :- Lateral
Medial
 4 borders :- Upper
Lower
Anterior
Posterior
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2 Processes :- Coronoid
Condyle
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• CONDYLE
Strong upward projection from the
posterosuperior part of the ramus.
Upper part is expanded from side to side to
form the head.
The constriction below head is the neck .
Anterior surface presents a depression called
the pterygoid fossa.
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• CORONOID PROCESS
Flattened traiangular projection from
anterosuperior part of ramus.
Anterior border continuous with anterior
border of ramus.
Posterior border bounds the mandibular
notch.
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• ALVEOLAR PROCESS :-
In adults 16 sockets are present ; 8 on each
side
Covered by mucoperiosteum
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15. MUSCLE ATTACHMENTS
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PRENATAL DEVELOPMENT
OF MANDIBLE
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• The cartilages and bones of the mandibular
skeleton form from embryonic neural crest
cells that originate in the mid- and hindbrain
regions of the neural folds.
• The first structure to develop in the region of
the lower jaw is the mandibular division of the
trigeminal nerve .

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• The mandible is derived from ossification of
an osteogenic membrane formed from
ectomesenchymal condensation at 36 to 38
days of development.
• The intramembranous bone lies lateral to
Meckel’s cartilage of the first (mandibular)
pharyngeal arch
.
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• A single ossification center for each half of the
mandible arises in the 6th week post
conception in the region of the bifurcation of
the inferior alveolar nerve and artery into
mental and incisive branches.
• The ossifying membrane is lateral to Meckel’s
cartilage and its accompanying neurovascular
bundle.
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• Ossification spreads :-
 Upward – Forms trough for the developing
teeth
Dorsally – Forms body of the mandible
Ventrally – Forms ramus of the mandible
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• Ossification stops dorsally at the site that will
become the mandibular lingula, where
Meckel’s cartilage continues into the middle
ear.
• The first pharyngeal-arch core of Meckel’s
cartilage almost meets its fellow of the
opposite side ventrally. It diverges dorsally to
end in the tympanic cavity of each middle ear,
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• The dorsal end of Meckel’s cartilage ossifies to
form the basis of two of the auditory
ossicles(ie, the malleus and the incus).
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28. FATE OF MECKEL’S CARTILAGE
• Meckel’s cartilage lacks the enzyme
phosphatase found in ossifying cartilages,
thus precluding its ossification; almost all of
Meckel’s cartilage disappears by the 24th
week after conception.
• Parts transform into the sphenomandibular
and anterior malleolar ligaments.
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• A small part of its ventral end (from the
mental foramen ventrally to the symphysis)
forms accessory endochondral ossicles that
are incorporated into the chin region of the
mandible.
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• Secondary accessory cartilages appear
between the 10th and 14th weeks post
conception to form the head of the condyle,
part of the coronoid process,and the mental
protuberance
• The condylar secondary cartilage appears
during the 10th week post conception as a
cone-shaped structure in the ramal region
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• Cartilage cells differentiate from its center,
and the cartilage condylar head increases by
interstitial and appositional growth.
• By the 14th week, the first evidence of
endochondral bone appears in the condyle
region
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• By the middle of fetal life, much of the cone-
shaped cartilage is replaced with bone, but its
upper end persists into adulthood, acting as
both growth and articular cartilage.
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• The coronoid accessory cartilage becomes
incorporated into the expanding
intramembranous bone of the ramus and
disappears before birth
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• In the mental region, on either side of the
symphysis, one or two small cartilages appear
and ossify in the 7th month post conception to
form a variable number of mental ossicles in the
fibrous tissue of the symphysis
• The ossicles become incorporated into the
intramembranous bone when the symphysis
menti is converted from a syndesmosis into a
synostosis during the 1st postnatal year.
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• POST NATAL DEVELOPMENT
OF MANDIBLE
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• According to MOSS while mandible appears in the adult as
a single bone,it is divisible into several skeletal subunit
Ramus
Coronoid process
Condylar process
Angular process
Lingual Tuberosity
Body of mandible
Alveolar process
Chin
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RAMUS
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• Anterior border :-
Superior surface – Deposition
Inferior surface – Resorption
• Posterior border
Superior surface – Resorption
Inferior surface - Deposition
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• Mesial Surface :-Resorption
• Buccal Surface :- Deposition
• The Ramus is modified Posterosuperiorly
• Breadth of the ramus increases only till there
is enlargement of middle cranial fossa and
pharynx
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40. MANDIBULAR FORAMEN
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MANDIBULAR FORAMEN
Anterior – Deposition
Posteriorly – Resorption
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CORONOID PROCESS
Has a propeller like twist
Lingual surface faces 3 general directions at
once ; posterior ,superior,medially
Bone is added onto the lingual side of the
coronoid process ;growth procceds superiorly
and this part of ramus increases vertically.
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• The same deposit of bone on lingual side also
bring about a posterior direction of growth
movement ;producing backward movement of
two coronoid process even though deposits
on lingual side .
• The same deposit on lingual side also bring
medial direction of growth in order to
lengthen corpus
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• Buccal side – Resorptive
• Lingual side – Depository
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45. CORONOID PROCESS

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• LINGUAL TUBEROSITY
Grows posteriorly by deposition on its
posterior surface.
Closely overlies the maxillary tuberosity (both
are alligned on PM plane)
Prominence of tuberosity augmented by
presence of large resorptive field just below it
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• Resorptive field creates depression called
Lingual Fossa.
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50. LINGUAL TUBEROSITY
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CONDYLE
 Historically it has been cornucopia from
which the whole mandible pours forth
Recent times ,this ‘master center’ concept has
been abolished.
The condyle functions as a regional field of
growth that provides an adaptation for its
own localised growth circumstances
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• The condylar cartilage is a special non-vascular
tissue.
• The endochondral growth mechanism occurs
only at the articular contact part of condyle.
• The condyle has a multidirectional capacity for
growth.
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• Superior surface of condyle is depository
• The lingual and buccal sides of neck
characteristically have a resorptive
surface.This is because condyle is quite broad
and neck is narrow.
• The neck is progressively relocated into the
areas previously held by the much wider
condyle.
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• What used to be condyle in turn becomes the
neck as one is remodeled from other.(done by
periosteal resorption combined wih endosteal
deposition).
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• Explained another way ,the endosteal surface
of the neck actually faces the growth
direction;the periosteal side points away from
the course of growth.
• This is another example of V principle ,with
the V shaped cone of the condylar neck
growing towards its wide end.
•
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THE CONDYLAR QUESTION
• What is the physical force that produces the
forward and downward primary displacement
of mandible?
• Functional mandibles totally lacking condyles
exist in nature;bilaterally condyle lacking
mandible occupies essential normal anatomic
position; HOW?
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2 conclusions obtained:-
First; condyles may not play the kingpin role of
a “master center”.
Second;the whole mandible can become
displaced anteriorly and inferiorly in its
functional position without a “push” against
the basicranium.(this observation led to
Functional matrix theory)
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• BODY OF MANDIBLE
• Most of the outer surface of mandibular
corpus receive bone deposition on both
buccal and lingual side;with resorption
occuring from the endosteal
surface(resorptive periosteal area occurs on
labial side of incisor region and below lingual
tuberosity)
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• The remodeling of former ramal bone into
posteror part results in lengthening of the
body of mandible.
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• ANGLE OF MANDIBLE
• Buccal Surface :-
• Bone deposition- postero-inferior surface
• Bone resorption – antero-superior surface
• Lingual Surface
• Bone deposition – antero-superior surface
• Bone resorption – postero-inferior surface
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• ANTEGONIAL NOTCH
• A single field of surface resorption is present
on the inferior edge of mandible at the ramus
corpus junction.This forms the antegonial
notch.
• In vertical growth it is deep ;horizontal growth
its shallow.
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• ALVEOLAR PROCESS
• As teeth errupt the alveolar process develops
and increases in height by bone deposition in
the margins.
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• THE CHIN
• Deposition in the chin itself while the area of
anterior surface of alveolus above the chin is
resorptive.
• Deposition happens in its lower
border;increasing the size of symphysis.
• Thickening of symphysis takes place by
apposition in the posterior surface.
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• MANDIBULAR GROWTH ROTATION
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FORWARD ROTATION
Occurs in 3 ways :-
 Type 1 – axis centers into joint ;this can give
rise to deepbite.
 Type 2 – center located at the incisal edges of
lower anterior ;posterior part of mandible
rotates away from maxilla.
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• Type 3 – center of rotation lies to the level of
premolar
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• BACKWARD ROTATION
• 2 TYPES :-
 Type 1 – Center of rotation lies in the
temperomandibular joints.
Type 2 – Center situated at the most distal
occluding molar
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• STRUCTURAL SIGNS OF GROWTH ROTATION
• 1> Inclination of the condylar head
• 2> Curvature of the mandibular cannal.
• 3> Shape of the lower border of mandible
• 4> inclination of the symphysis
• 5> interincisal angle
• 6> intermolar or interpremolar relations
• 7> anterior lower facial height
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• GROWTH TIMING OF MANDIBLE
• The overall growth of mandible takes place at
different stages
• The chronology follows :-
1> Width
2> Length
3> Height
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• GROWTH IN WIDTH
Completed before adolescent growth spurts
Intercanine width does not increase after 12
Both molar and bicondylar width shows small
increase until growth in length ends.
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• GROWTH IN LENGTH
Growth in length continues through puberty.
Girls – 14-15 years
Boys – 18-19 years
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• GROWTH IN HEIGHT
Continues in both the sexes for longer
duration
Growth increase occurs with erruption of
teeth and continues to increase throughout
life but the decline to the adult level often
does not occur until the early 20s in boys and
somewhat earlier in girls.
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• DEVELOPMENTAL ANOMALIES
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• Agnathia
Hypoplasia or absent of mandiblewith
abnormally positioned ear.
Autosomal recessive
It is probably due to failure of neural crest
mesenchyme into the maxillary prominence
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• Micrognathia
Small jaw
Severe retrusion of chin.
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• Macrognathia
Abnormally large jaw
Eg Paget’s disease, Fibrous dysplasia
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• Coronoid Hyperplasia
Rare developmental anamoly
Results in limited mandibular movement
May be unilateral or bilateral ; bilateral more
common
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• Condylar Hyperplasia
Excessive growth of one of the condyle.
Cause is unknown ,but local circulating
problems,endocrine disturbances and trauma
has been suggested as possible etiological
factors.
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• Condylar hypolplasia
Congenital or acquired
Eg – Mandibulofacial dyostosis,Goldenhar
syndrome,hemifacial microsomia.
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• REFERENCES
• Craniofacial Development – Geoffrey
H.Sperber (Ch- The Mandible ;pg- 127)
• Essential of facial growth – Enlow and Hans
(Ch-Growth of Mandible ; pg -57)
• Prediction of Mandibular Growth –
A.Bjork(AJO)
• Human Anatomy –BD Chaurasia’s (ch-
Osteology ;pg 31)
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• Contemporary Orthodontics –Wiiliam
R.Profit(ch 2,ch-4)
• Google images
• Shafer’s textbook of Oral Pathology sixth
edition
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