Development of mandible /certified fixed orthodontic courses by Indian dental academy

INDIAN
ACADEMY

DENTAL

Leader in continuing dental education
www.indiandentalacademy.com




Contents
Introduction
 Prenatal growth
 Ossification
 Concept of remodeling
 Postnatal growth
 Clinical implications



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?

Prenatal Growth


Prenatal Growth

36-38 day Iul

Ectomesenchymal cells
Epi. Of 1st arch

Osteogenic Memb.

Prenatal Growth

6th week


Prenatal Growth
Trough for dev. teeth
Trough for dev. teeth

1°centre of ossification
1°centre of ossification
below

Infr alv. Nerve &
Infr alv. Nerve &
Incisive branch
Incisive branch

around

Prenatal Growth
Fate of Meckel’s cartilage


Prenatal Growth
New bone

Woven bone
Woven bone
5th month i. u.
5th month i. u.

Lamellar bone + haversian system
Lamellar bone + haversian system

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
During fetal life
During fetal life
8 weeks -- mandible > maxilla
8 weeks
mandible > maxilla
11 weeks -- mandible = maxilla
11 weeks
mandible = maxilla
13 – 20 weeks maxilla > mandible
13 – 20 weeks maxilla > mandible
At Birth
At Birth
Mandible tends to be retrognathic
Mandible tends to be retrognathic
Early post natal life -- orthognathic
Early post natal life orthognathic

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
Centre of ossification
Osteoid matrix


Intramembranous


Endochondral
Mesenchymal cells

osteoblast

Cart. Matrix of glycoproteins

Cart. template
Blood vessels

Osteoid matrix

mineralized

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 part
Regional part

counter part
counter part

Balanced growth
Balanced growth

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

articular
articular

growth
growth
Not a pri. Centre of growth but rather
2° in evolution
2° in evolution
2° in embryonic origin
2° in embryonic origin
2°in adaptive responses to changing dev.
2°in adaptive responses to changing dev.

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
experiments

Ramus


Moves progressively posterior
by:Deposition
POSTERIOR PART



Resorption



ANTERIOR PART


Ramus
Superior part of ramus
below sigmoid notch

Lingual -Deposition
Buccal - Resorption

Lower part of ramus
below the Coronoid
process

Buccal - Deposition
Lingual - Resorption


Ramus


Coronoid process
Posterior

Lingual surface

Superior
Medially
Follows ‘v’ principle


Coronoid process
‘’V’ PRINCIPLE OF ENLOW


Coronoid process


Medial



Increases
vertical length

Deposition on lingual side

Posterior Growth

Resorption - buccal surface


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 belowLingual 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 anteriors
Lingual 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 -- microgenia
Under 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


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


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

2. Developmental

• Agnathia

•

Infantile cortical hyperostosis

•

Achondroplasia

• Macrognathia

•

Torus mandibularis

• Facial
hemihypertrophy

•

Stafne’s cyst

• Facial hemiatropy

•

Odontogenic cyst

•

Odontogenic tumor

• Micrognathia


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



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Development of mandible /certified fixed orthodontic courses by Indian dental academy

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