GROWTH AND DEVELOPMENT OF THE MANDIBLE1.ppt

PERIO

1. GROWTH AND DEVELOPMENT
OF THE MANDIBLE

2. GROWTH AND
DEVELOPMENT OF THE
MANDIBLE

ANATOMY

PRE NATAL GROWTH

POST NATAL GROWTH

ANOMALIES OF
DEVELOPMENT

3. Prenatal growth of the
mandible

4. Neural crest cells
I branchial arch
Mandibular
process
Mandibular
bone
CT tissue

6. 36 – 38 DAYS
Ectomesenchymal
condensation
Lateral to
Meckels cartilage
Osteogenic
membrane
mandible

7. 6
th
week
Ossification centre

8. 10
th
– 14
th
weeks

Secondary
accessory
cartilages
appear

9. 10 week - condylar
cartilage
Appears in the Ramal region
Endochondral bone
(14 week)

10. 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

11. 7
th
month IUL

1 or 2 small cartilages appear in
the future mental region

Mental ossicles

Incorporated into the
intramembranous bone of
symphsis

12. 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

13. Features of neonatal
mandible
High
Coronoid
process
Wide
Ramus

14. Differential growth

8 weeks - mandible > maxilla

11 weeks - mandible = maxilla

13 – 20 weeks maxilla > mandible
At birth

Mandible tends to be retrognathic

Post natal life - corrected
During fetal life

15. Post natal growth of the
mandible

16. Main sites of post natal
growth in the Mandible

Condylar cartilage

Posterior border of the Rami

Alveolar ridges

17. Symphysis Menti

Limited growth
till fusion

No widening
after fusion

18. Mental Foramen

19. Mental Foramen

Vertical relation
within the body
of the mandible

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

21. Mental Protruberance
Forms by
osseous
deposition during
childhood
Prominence is
accentuated by
bone resorption
above it

22. Mental Protuberance

Reversal between 2
growth fields

Concave convex

Reversal line could be
High or low

23. Alveolar process

Adds to the height
and thickness of the
mandibular body

Teeth absent
fails to develop

Teeth extracted
resorbs

24. Alveolar process

Acts as buffer zone

Maintains vertical height

Adaptive remodeling makes
orthodontic tooth movement
possible

25. Alveolar process
Lingual movement of anteriors

26. Condylar cartilage

Secondary cartilage

Important contribution to the
overall length of the mandible

27. 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

28. 
PETROVIC ET AL – role of hormones

Experiments involving transplantation of
the condyle

JOHNSTON ETAL detached condyle from
the body of mandible in guinea pigs

RANCHOW MOSS - Condylectomy –
immediate resumption of growth

29. CURRENT CONCEPT
Condylar cartilage does have a measure of intrinsic genetic
programming
But extra condylar factors are needed to sustain this activity
Increase pressure – growth inhibition
Decrease pressure – stimulates growth
Physiologic
inductors
Intrinsic and extrinsic
biomechanical forces
ENLOW :
based mainly
on animal
experiments

30. The new image of Condyle and
Condylar growth

Entire Ramus

Muscles attached

The Condyle

31. Lingual Tuberosity

Grows posterior
and medial by
deposition

Resorptive field
below-
Lingual fossa

32. Coronoid Process

Lingual surface

Follows ‘v’ principle
POSTERIOR
SUPERIOR
MEDIALLY

33. 
‘ v ‘ principle
of Enlow
CORONOID PROCESS

34. Coronoid Process

‘’V’ PRINCIPLE OF ENLOW

35. Coronoid Process

Deposition on lingual side

Resorption - buccal surface
MEDIAL
POSTERIOR
GROWTH
INCREASES
VERTICAL
LENGTH

36. RAMUS

Posterior
border -
deposition

Anterior
border -
resorption

37. Remodeling & Displacement

38. Ramus
Superior part of ramus
below sigmoid notch
Lower part of ramus
below the Coronoid
process
BUCCAL -
DEPOSITION
LINGUAL -
RESORPTION
LINGUAL -
DEPOSITION
BUCCAL -
RESORPTION

39. Ramus

40. Posterior border of Ramus
Depository and keeps pace
with condylar growth
Angle of growth
Posterior margin below
condyle --resorptive field
verticalhorizontal

41. Ramus Uprighting

Posterior border –
deposition
Inferior > superior

Anterior border –
resorption
Inferior >superior

42. Age related differences in
mandibular growth

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
MARK HANS , DONALD ENLOW
AO DEC 1995

43. Type A – Classical Pattern

44. Type B – Vertical Variation


45. Type C - Rotation Variation

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

47. Ramus corpus junction

Inferior Border of
junction -
resorption

Forms Antegonial
notch

48. The depth of the mandibular
antegonial notch as an indicator of
mandibular growth potential
Study showing –
Clinical presence of deep mandibular AG
notch is indicative of

Diminished mandibular growth potential &

Vertically directed mandibular growth
pattern
- AJO 1987, C P Singer , A H Mamandras

49. Gonial region

Anatomically variable

Gonial flares

Depends upon growth direction of ramus
and condyle
inwardly
outwardly
B - Resorption
L - deposition
B -deposition
L - resorption

50. Mandibular foramen

Ramus -- posterior
and superior
direction

Mandibular foramen
drifts in backward &
upward direction

Maintains constant
position -[A-P]

51. Combination of Condylar
and 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

52. Role of muscles in
Mandibular growth
CORONOID Temporalis
RAMUS and
GONIAL ANGLE Masseter & Medial
pterygoid
CONDYLE internal pterygoid
Tongue, perioral muscles --- Over all growth
MOSS

53. Skeletal units of mandible

54. Role of muscles in
Mandibular growth

Decrease muscle activity
Flattening of
Gonial angle
Reduction of
Coronoid process

55. Growth of mandible during
pubescence
Study to analyse relation between
magnitude & timing of pubertal
spurts in mandible,
ages at PHV & at menarche & levels
of skeletal maturity with in
individuals.
ARTHUR LEWIS , ALEX ROCHE
AO OCT 1982

56. Growth of mandible during
pubescence
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

57. Growth of mandible during Growth of mandible during
pubescencepubescence

58. Growth of mandible during
pubescence

Spurts in mandibular dimensions are common but
not universal

More common in boys

1.5 yrs earlier in girls

1
st
pubertal spurt usually occurs before PHV

Almost all 1
st
pubertal spurts occur one year after
US ossification and before menarche
conclusion

59. LATE GROWTH
CHANGES IN THE
MANDIBLE

Menton

B point

Gonion

Condyle

Gonial angle

60. CHANGES IN MANDIBULAR PLANE & DENTITION
FEMALES MALES

61. Anomalies of development

AGNATHIA – deficiency of neural crest
cells in lower part of the face

MICROGNATHIA -
DOWNS
TREACHER COLLINS
PIERRE ROBIN

62. Anomalies of development

BIFID /DOUBLE CONDYLE

MACROGNATHIA

MICROGENIA

TORUS MANDIBULARIS

64. 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 AO DEC 1995
The depth of the mandibular antegonial notch as an
indicator of mandibular growth potential- - AJO 1987,
C P Singer , A H Mamandras