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Development of mandible /certified fixed orthodontic courses by Indian dental academy
1. DEVELOPMENT OF MANDIBLE
INDIAN DENTAL ACADEMY
Leader in continuing dental education
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3. 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?
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12. Prenatal Growth
New bone
Woven bone
Woven bone
5th month i. u.
5th month i. u.
Lamellar bone + haversian system
Lamellar bone + haversian system
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14. Prenatal Growth
Secondary cartilage of coronoid process
Develop within temporalis muscle
Incorporated into IMB of ramus
Disappear before birth
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15. Prenatal Growth
Sec. cartilage at Mental region
1 or 2 small cartilage mental ossicles(7th IUL)
Incorporated into IMB
syndesmosis
synostosis
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16. Prenatal Growth
Sec. Condylar cartilage (10th week of IUL)
Grow interstitially & appositionally
14th week 1st evidence of Endochondral bone
formation
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17. 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
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18. 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
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19. 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
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20. Post Natal Growth
Types
of ossification
Mechanism
of bone growth
Anatomy
Theories
of growth
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21. Types Of Ossification
Mandible is the second bone in the body to be ossified
There are two types of ossification :
INTRAMEMBRANOUS
ENDOCHONDRAL
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28. 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
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29. 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
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30. 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
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35. Other Theories
ENLOW’S “V”
PRINCIPLE
The growth and
enlargement of bones
occur towards wide end
of ‘v’ due to differential
deposition and
resorption
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36. 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
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37. “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
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38. Post Natal Growth And
Development
GROWTH TIMING
Growth of width of mandible is completed first, then growth in
length and finally growth in height
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39. Post Natal Growth And
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
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40. Post Natal Growth And
Development
GROWTH IN LENGTH
Growth in length continues through puberty
Girls—14-15 years
boys---18-19 years
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41. Post Natal Growth And
Development
Main sites of post natal growth in the Mandible
Condylar cartilage
Posterior border of the Rami
Alveolar ridges
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42. 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.
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43. 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
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44. 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
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45.
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
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46. 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
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based mainly on animal
experiments
48. Ramus
Superior part of ramus
below sigmoid notch
Lingual -Deposition
Buccal - Resorption
Lower part of ramus
below the Coronoid
process
Buccal - Deposition
Lingual - Resorption
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54. 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
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58. Alveolar Process
Adds to the height and
thickness of the
mandibular body
Teeth absent fails to
develop
Teeth extracted resorbs
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59. Alveolar Process
Maintain occlusal relationship during differential mandibular
& midfacial growth– buffer zones
Maintains vertical height
Adaptive remodeling makes orthodontic tooth movement
possible
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61. Mental Protuberance
Formed by mental ossicles from accessory
cartilage and ventral end of Meckel’s
cartilage
Poorly developed in infants
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62. Mental Protuberance
Forms by osseous
deposition during
childhood
Prominence is accentuated
by bone resorption above
it
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64. 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
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