Development of mandible

Contents
 Introduction
 Prenatal growth
 Ossification
 Concept of remodeling
 Postnatal growth
 Clinical implications
www.indiandentalacademy.com

Introduction
Measurements in the
ceph show the results of
Growth of something,
somewhere, at some
time,
But of what? Why? And
in response to which
Biologic stimuli or
energies?
Measurements in the
ceph show the results of
Growth of something,
somewhere, at some
time,
But of what? Why? And
in response to which
Biologic stimuli or
energies?

Prenatal Growth

Prenatal Growth
Ectomesenchymal cells
Epi. Of 1st
arch
Osteogenic Memb.
36-38 day Iul

Prenatal Growth
6th
week

Prenatal Growth
1°centre of ossification1°centre of ossification
Infr alv. Nerve &
Incisive branch
Infr alv. Nerve &
Incisive branch
Trough for dev. teethTrough for dev. teeth
below around

Prenatal Growth
Fate of Meckel’s cartilage

Prenatal Growth
New bone
Woven boneWoven bone
Lamellar bone + haversian systemLamellar bone + haversian system
5th
month i. u.5th
month i. u.

Prenatal Growth
10th
& 12th
week
Sec. accessory cartilage

Prenatal Growth
 Secondary cartilage of coronoid process
 Develop within temporalis muscle
 Incorporated into IMB of ramus
 Disappear before birth

Prenatal Growth
 Sec. cartilage at Mental region
 1 or 2 small cartilage mental ossicles(7th
IUL)
 Incorporated into IMB
syndesmosis synostosis

Prenatal Growth
 Sec. Condylar cartilage (10th
week of IUL)
 Grow interstitially & appositionally
 14th
week 1st
evidence of Endochondral bone
formation

Condylar cartilage
 Serves as a growth site
 Brings changes in the mandibular position and form
 Growth increases during puberty
 Peak 12 – 14 years
 Ceases by 20 years

Neonatal mandible
 Ascending Ramus low and wide
 Large Coronoid process
 Body – open shell containing tooth buds and partially
formed deciduous teeth
 Mandibular canal that runs low in the body

Differential growth
8 weeks - mandible > maxilla
11 weeks - mandible = maxilla
13 – 20 weeks maxilla > mandible
8 weeks - mandible > maxilla
11 weeks - mandible = maxilla
13 – 20 weeks maxilla > mandible
During fetal lifeDuring fetal life
At BirthAt Birth
Mandible tends to be retrognathic
Early post natal life - orthognathic
Mandible tends to be retrognathic
Early post natal life - orthognathicwww.indiandentalacademy.com

Post Natal Growth
 Types of ossification
 Mechanism of bone growth
 Anatomy
 Theories of growth

Types Of Ossification
 Mandible is the second bone in the body to be ossified
 There are two types of ossification :
 INTRAMEMBRANOUS
 ENDOCHONDRAL

Intramembranous
Ectomesenchyme Epithelium
Osteogenic membrane
Osteoblast
Osteoid matrix
Centre of ossification

Intramembranous

Endochondral
Mesenchymal cells Cart. Matrix of glycoproteins
Cart. templateosteoblast
Osteoid matrix mineralized
Blood vessels

Endochondral

Clinical significance
 In postnatal life distinction b/w two is of no
significance:-
 # of intramembranous bone
 Surface remodelling of endochondral bone
 Prenatal life – congenital defects
 Achondroplasia – Endochondral bone
 Cleidocranial dysostosis – Intramembranous bone
 Osteogenesis Imperfecta – both type

Parts Of Mandible Derived From
1. INTRAMEMBRANOUS OSSIFICATION
i) Whole body of mandible except the anterior part
ii) Ramus of mandible as far as mandibular foramen
2 . ENDOCHONDRAL OSSIFICATION
i) Anterior portion of the mandible (symphysis)
ii) Part of ramus above the mandibular foramen
iii) Coronoid process
iv) Condylar process

Mechanisms Of Bone Growth
Growth Of The Mandible Primarily Involve
1. Bone remodelling
Process Of Bone Deposition And Resorption
2. Cortical drift
Combination of bone deposition and resorption resulting in growth movement
towards deposition surface
3. Displacement
Movement of whole bone as a unit
I) Primary displacement
II) Secondary displacement

Anatomy

Theories Of Growth

Other Theories
 ENLOW’S “V”
PRINCIPLE
 The growth and
enlargement of bones
occur towards wide end
of ‘v’ due to differential
deposition and
resorption

Enlow’s Counterpart Principle
 ‘The growth of any given facial or cranial part relates
specifically to other structural and geometric “counter” parts
in the face and cranium’.
 Eg. Maxillary arch is counter part of mandibular arch.
Regional partRegional part counter partcounter part
Balanced growthBalanced growthwww.indiandentalacademy.com

“The human mandible has no one design for
life. Rather it adapts and remodels through
the seven stages of life, from the slim
arbiter of things to come in the infant,
through a powerful dentate machine and
even weapon in the full flesh of maturity,
to the pencil thin, porcelain like problem
that we struggle to repair in the adversity
of old age.”
“The human mandible has no one design for
life. Rather it adapts and remodels through
the seven stages of life, from the slim
arbiter of things to come in the infant,
through a powerful dentate machine and
even weapon in the full flesh of maturity,
to the pencil thin, porcelain like problem
that we struggle to repair in the adversity
of old age.”
D.E. Poswillo, 1988D.E. Poswillo, 1988

Post Natal Growth And
Development
GROWTH TIMING
Growth of width of mandible is completed first, then growth in
length and finally growth in height

Development
WIDTH OF MANDIBLE
 Growth in width is completed before adolescent growth
spurt
 Intercanine width does increase after 12 years
 Both molar and bicondylar width shows small increase until
growth in length ends

Development
GROWTH IN LENGTH
 Growth in length continues through puberty
 Girls—14-15 years
 boys---18-19 years

Development
 Main sites of post natal growth in the Mandible
 Condylar cartilage
 Posterior border of the Rami
 Alveolar ridges

Condylar cartilage
Secondary cartilage
Dual function
articulararticular
growthgrowth
Not a pri. Centre of growth but rather
2° in evolution2° in evolution
2° in embryonic origin2° in embryonic origin
2°in adaptive responses to changing dev.2°in adaptive responses to changing dev.www.indiandentalacademy.com

Is the Condylar cartilage the principle
force that produces the displacement of
the mandible ?
For many years considered primary growth center
FMH - Condyle absent yet mandible positioned normally
Considered secondary cartilage -no intrinsic growth
potential

Petrovic et al - Role of hormones
Experiments involving transplantation of the condyle
Johnston et al - Detached condyle from the body of
mandible in guinea pigs
Injection of papain - Inhibition of chondrogenesis
Koski et al - Periosteal tension in condylar neck-lateral
pterygoid- controls condylar growth

 Condylar cartilage and functioning muscles translate the
mandible and in the absence of one the other does best to
compensate
 Integrity of periosteum is important
 When environment is changed compensatory contributions
are enhanced

Current Concept
 Condylar cartilage does have a measure of intrinsic genetic
programming
 But extra condylar factors are needed to sustain this activity
Physiologic
inductors
Intrinsic and extrinsic
biomechanical forces
ENLOW :
Increase pressure – growth inhibition
Decrease pressure – stimulates growth
based mainly on animal
experimentswww.indiandentalacademy.com

Ramus
 Moves progressively posterior
by:-
 Deposition
 Resorption ANTERIOR PART
POSTERIOR PART

Ramus
Superior part of ramus
below sigmoid notch
Buccal - Resorption
Lingual -Deposition
Lower part of ramus
below the Coronoid
process
Buccal - Deposition
Lingual - Resorption

Ramus

Coronoid process
Superior
Medially
Follows ‘v’ principle
Lingual surface Posterior

Coronoid process
‘’V’ PRINCIPLE OF ENLOW

Coronoid process
 Deposition on lingual side
 Resorption - buccal surface
Increases
vertical length
Posterior GrowthMedial

Body of mandible
 The increase in width of the mandible occurs primarily due
to resorption on the inside and deposition on the outside
 Increase in length occurs due to drift of the ramus
posteriorly
 Increase in height occurs due to eruption of the teeth

Ramus corpus junction
 Inferior Border of junction
- resorption
 Forms Antegonial notch

Antegonial notch
Size depends upon ramus – corpus angle

Lingual Tuberosity
 Grows posterior and
medial by deposition
 Resorptive field below-
Lingual fossa

Alveolar Process
 Adds to the height and
thickness of the
mandibular body
 Teeth absent fails to
develop
 Teeth extracted resorbs

Alveolar Process
 Maintain occlusal relationship during differential mandibular
& midfacial growth– buffer zones
 Maintains vertical height
 Adaptive remodeling makes orthodontic tooth movement
possible

Alveolar Process
Lingual movement of anteriorsLingual movement of anteriors

Mental Protuberance
 Formed by mental ossicles from accessory
cartilage and ventral end of Meckel’s
cartilage
 Poorly developed in infants

Mental Protuberance
 Forms by osseous
deposition during
childhood
 Prominence is accentuated
by bone resorption above
it

Mental Protuberance
 Reversal between 2
growth fields
 Concave  convex
 Reversal line could be
High or low

Chin
 Protrusive chin is unique human trait
 More prominent in male
 Less prominent in female
Under dev. Of chin - microgeniaUnder dev. Of chin - microgenia

Symphysis Menti
 Limited growth till fusion
 No widening after fusion

Mental Foramen

Factors Affecting Growth
A)Systemic Factors
1. Genetic
2. Hormonal imbalance
3. Nutrition
4. Systemic illness or chronic illness
5. Localized alteration/ diseases of uterus
6. Systemic illness in mother
7. Drugs www.indiandentalacademy.com

B) Local factors
1. Vascular abnormality
2. Lymphatic disturbance
3. Neurologic disease
4. Local infection
5. Ear infection or mastoiditis
6. Ankylosis
7. Trauma or fracture
8. Birth injury
9. Habits www.indiandentalacademy.com

Anomalies of mandible
 Some of the syndromes associated with mandibular
abnormality
i) Down’s syndrome
i) Marfan’s syndrome
ii) Turners syndrome
iii) Kleinfelter’s syndrome
iv) Pierre-robin syndrome
v) Treacher- collin syndrome

1. Congenital
• Agnathia
• Micrognathia
• Macrognathia
• Facial
hemihypertrophy
• Facial hemiatropy
2. Developmental
• Infantile cortical hyperostosis
• Achondroplasia
• Torus mandibularis
• Stafne’s cyst
• Odontogenic cyst
• Odontogenic tumor

Age Changes Of The Mandible

References
 Craniofacial embryology – SPERBER
 Facial growth – ENLOW
 Contemporary orthodontics – PROFFIT
 Handbook of orthodontics – MOYERS
 Principles and practice of orthodontics –GRABER

Development of mandible

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