The document discusses the growth and development of the mandible from prenatal to postnatal stages. It describes how the mandible develops from neural crest cells and the main sites of growth, including the condylar cartilage, rami, alveolar processes, and symphysis menti. The condylar cartilage contributes to overall mandibular length through endochondral bone formation, though its role as the primary growth center is debated. Other factors like muscles and biomechanical forces also influence mandibular positioning and shape. Growth patterns vary during development and puberty, with growth spurts typically occurring earlier in girls. Certain anomalies can also affect mandibular development.
10. 10 week - condylar cartilage
Appears in the Ramal region
Endochondral bone
(14 week)
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11. 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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12. 7 th month IUL
1 or 2 small cartilages appear in the
future mental region
Mental ossicles
Incorporated into the
intramembranous bone of symphsis
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13. Features of 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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17. Main sites of post natal growth
in the Mandible
Condylar cartilage
Posterior border of the Rami Width
Height
length
Alveolar ridges
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21. Mental Protuberance
Formed by mental ossicles
from accessory cartilage
and ventral end of Meckel’s
cartilage
Poorly developed in infants
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24. Alveolar process
Adds to the height and
thickness of the
mandibular body
Teeth absent
fails to develop
Teeth extracted
resorbs
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25. Alveolar process
Acts as buffer zone
Maintains vertical height
Adaptive remodeling makes orthodontic
tooth movement possible
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29. 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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30.
PETROVIC ET AL – role of hormones
Experiments involving transplantation of the condyle
JOHNSTON ETAL
detached condyle from the body
of mandible in guinea pigs
Injection of papain –inhibition of chondrogenesis
RANCHOW MOSS
- Condylectomy – immediate
resumption of growth
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31.
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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32. 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
38. Ramus
Superior part of
ramus below sigmoid
notch
Lower part of ramus
below the Coronoid
process
LINGUAL
-DEPOSITION
BUCCAL RESORPTION
BUCCAL DEPOSITION
LINGUAL RESORPTION
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40. Posterior border of Ramus
Depository and keeps pace
with condylar growth
Angle of growth
vertical
horizontal
Posterior margin below
condyle --resorptive field
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42. Age related differences in
mandibular growth
MARK HANS , DONALD ENLOW
AJO DEC 1995
30 well preserved human mandibles from
dental ages 1 – 13 years
Ground and polished microscopic sections
were obtained from the Ramus
Distribution of various types of resorptive vs
depository surfaces were recorded
2 additional patterns of Ramal remodeling
were noted
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43. Type A – Classical Pattern
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44. Type B – Vertical Variation
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45. Type C - Rotation Variation
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46. Conclusions
All 3 patterns cause downward & forward
displacement but to varying degree
ENLOW’S original description of general
body growth & remodeling type A most
common but one pattern of remodeling is
incomplete
The difference in pattern were large enough
to influence orthodontic treatment
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48. Gonial region
Anatomically variable
B - Resorption
Gonial flares
inwardly
outwardly
L - deposition
B -deposition
L - resorption
Depends upon growth direction of ramus and
condyle
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49. Mandibular foramen
Ramus -- posterior
and superior direction
Mandibular foramen
drifts in backward &
upward direction
Maintains constant
position -[A-P]
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51. Ramal growth
Backward transportation of entire ramus –
elongation of mandibular body
Displacement of corpus –anterior direction
Vertical lengthening of ramus as mandible is
displaced
Movable articulation during various growth
changes
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52. Role of muscles in
Mandibular growth
MOSS
CORONOID
GONIAL ANGLE
Medial
CONDYLE
Temporalis
Masseter &
pterygoid
internal pterygoid
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54. Role of muscles in Mandibular
growth
Decrease muscle activity
Flattening of
Gonial angle
Reduction of
Coronoid process
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55. Growth of mandible during
pubescence ARTHUR LEWIS , ALEX ROCHE
AJO OCT 1982
Spurts in the mandible were analyzed in 67
subjects from Fels longitudinal study
Spurts in Ar-Go , Ar-Gn , Go-Gn
A spurt was defined as an annual increment
exceeding the immediately preceding annual
increment by at least 1 mm
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57. Growth of mandible during
pubescence
conclusion
Spurts in mandibular dimensions are common but not
universal
More common in boys
1.5 yrs earlier in girls
1st pubertal spurt usually occurs before PHV
Almost all 1st pubertal spurts occur one year after US
ossification and before menarche
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58. Anomalies of development
AGNATHIA – deficiency of neural crest
cells in lower part of the face
DOWNS
MICROGNATHIA -
TREACHER COLLINS
PIERRE ROBIN
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60. References
Craniofacial embryology – SPERBER
Facial growth – ENLOW
Contemporary orthodontics – PROFFIT
Handbook of orthodontics – MOYERS
Principles and practice of orthodontics –
GRABER
Growth of mandible during pubescence –
ROCHE,LEWIS AO OCT 1982
Age related differences in Ramus growth –
ENLOW,HANS AJO DEC 1995
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