MANDIBLE DESCRITION, EARLY STAGE, NEONATALM STAGE, CHANGES IN AGE

1. DEVELOPMENT OF MANDIBLE
PRESENTER: SRAVYA
MODERATOR: Dr. ANULEKHA

2. CONTENTS
INTRODUCTION
DEVELOPMENT OF MANDIBLE
PRENATAL DEVELOPMENT OF MANDIBLE
POSTNATAL DEVELOPMENT OF MANDIBLE
BLOOD SUPPLY
NERVE SUPPLE
LYMPHATIC DRAINAGE
PHYSIOLOGICAL VARIANTS
AGE CHANGES
APPLIED ANATOMY
CONCLUSION
REFERENCES

3. INTRODUCTION
• Largest and strongest bone of face
• Greek word ‘mandere’-to masticate/chew
• Latin word ‘mandibula’-lower jaw
• It forms the lower jaw and holds the lower teeth in place
• It has:
a horseshoe shaped body
2 rami
2 condylar heads
2 coronoid processes

4. • The mandible is the only bone in the entire skull that
does not articulate with its adjacent skull bones with
sutures.
• It articulates on either side with temporal bone to
form temporomandibular joint.

5. DEVELOPMENT OF MANDIBLE
Mixed bone: Develops by both endochondral and intramembranous ossification
Majorly it is by intramembranous ossification

6. The development can be divided into:
PRENATAL POSTNATAL

7. 4th
week of i.u developing brain
and pericardium form two
prominent bulges separated by
primitive oral cavity
(stomodeum)
Pharyngeal arches will be laid down in
close approximation to stomodeum.
1st
arch mandibular arch
2nd
arch hyoid arch

8. PRENATAL DEVELOPMENT OF MANDIBLE
Develops from the first pharyngeal arch , with the
help of cartilage of the 1st arch (Meckel’s cartilage).
The first branchial arch
Divides into a maxillary process and a mandibular
process
Forms the bones of the lower two-thirds of the face
and the jaw.
The first structure to develop in the primordium of
lower jaw is the mandibular division of trigeminal
nerve.

9. MECKEL’S CARTILAGE
Derived from 1st
arch around 41st
- 45th
day i.u
It provides framework and delimits the region
where bone formation would takes place.
The major portion of it disappears and the rest
forms the following structures:

10. The cartilage extends as a solid unbroke rod of hyaline cartilage with its proximal ends
connected with the ear capsules and its distal extremity is joined with its anatomic
counterpart through mesodermal tissue.

11. Meckel’s cartilage extends from cartilaginous
otic capsule to the symphysis and provides a
template for guiding the growth of the
mandible.
A single ossification center for each half of the
mandible arises in 6th
week i.u in the region of
division of bifurcation of inferior alveolar
nerve into mental and incisive branches.
The ossifying membrane is located lateral to
the cartilage.

12. At the lateral aspect of cartilage a mesenchymal
condensation occurs at the angle formed between the
mental and incisive nerves. This mesenchymal
condensation is considered as the initial site of
osteogenesis.

13. From this initial site of osteogenesis ,
intramembranous bone formation will first proceed
anteriorly and posteriorly to the point where the
mandibular nerve divides into INFERIOR
ALVEOLAR NERVE and LINGUAL NERVE.

14. From the primary center ossification spreads below and
around the inferior alveolar nerve and upwards to form a
trough for accommodating the developing tooth buds.

15. Ossification stops at a point , which later become mandibular
lingula , the remaining part of Meckel's cartilage continues into
middle ear and develops malleus and incus. It also forms
sphenomandibular ligament.

16. FATE OF MECKEL’S CARTILAGE
 The proximal portion gives the Malleus and
Incus, two of the bones of the middle ear.
 The distal portion gives rise to the cartilaginous
remnants in the midline of the mandible.
 The middle portion is replaced by fibrous tissue,
which persists to form the sphenomandibular
ligament.

17. Endochondral bone formation is seen only in 3
areas of mandible:
Condylar process
Coronoid process
Mental region
Secondary accessory cartilage appear between 10th
& 14th
week of IU to form head of condyle , part of
coronoid process & mental protuberance.

18. CONDYLAR PROCESS
At 5th week of IU life ,an area of mesenchymal condensation is seen above the ventral part
of developing mandible.
At about 10th week, it develops in cone shaped cartilage. It migrate inferior & fuses with
mandibular ramus at about 4 month.
This cone shaped cartilage is replaced by bone but its upper end persists into adulthood
acting as both growth cartilage & articular cartilage.

19. CORONOID PROCESS
Secondary accessory cartilage appear in region of coronoid
process at about 10- 14 week of intrauterine life.
This cartilage become incorporated into expanding
intramembranous bone of ramus & disappear before birth

20. MENTAL REGION
In mental region , on either side of symphysis , one or
two small cartilage appear and ossify in 7th week of
IU to become mental ossicles.
These ossicles become incorporated into
intramembranous bone when symphysis ossify
completely.

21. DEVELOPMENT OF ALVEOLAR PROCESS
At the end of the 2nd
month of fetal life the maxilla & mandible
forms a groove that is open towards the surface of the oral cavity.
As the tooth develops, so does the alveolar bone which keeps pace
with the lengthening of roots.
At first , alveolar process forms labial and lingual plates between
which a trench is formed where the tooth organs develop.

22. As the walls lining this trench increase in height , bony septa
appear gradually between the teeth to complete the
Crypts.
Much later the primitive mandibular canal is separated from
the dental crypts by a horizontal plate of bone.
The alveolar process forms with the development &
eruption of teeth & conversely it gradually diminishes in
height after the loss of teeth.

23. Mandible of human embryo
24 mm. long. Outer aspect.
Mandible of human embryo
24 mm. long. Inner aspect.
Mandible of human embryo 95 mm. long.
Outer aspect. Nuclei of cartilage stippled.
Mandible of human embryo 95 mm. long. Inner
aspect. Nuclei of cartilage stippled.

24. SUMMARY OF EVENTS
 24 days-formation of mandibular arch.
 27 days-appearance of mandibular division of trigeminal
nerve.
 36 days-formation of osteogenic membrane.
 42 days-first ossification center between incisive and mental branch
of inferior alveolar nerve.
 55 days – beginning of coronoid and condyle.
 Before end of 2nd
month – tooth germs distinguished.
 Fetus at mid term – mandible consists of body and alveolar process.
 4 ½ months I.U.L. – adult form recognized.

25. POST NATAL GROWTH OF MANDIBLE
Of the facial bones, mandible undergoes the largest amount of growth post-natally and
also exhibits largest variability in morphology.
While in the adults it appears as a single bone, it is developmentally and functionally
divisible into several skeletal sub-units like:
Ramus
Body of mandible
Angle of mandible
Lingual tuberosity
Alveolar process
Condyle
Coronoid process
Mental protuberance

26. RAMUS
• Ramus of the mandible develops by a rapid
spread of ossification backwards in to the
mesenchyme of the first brachial arch
diverging away from Meckels cartilage .
• This point of divergence is marked by the
mandibular foramen

27. It moves progressively posterior by combination of resorption and
deposition.
Resorption – anterior part
Deposition – posterior part
Results in a drift of ramus in posterior direction

28. ANGLE OF MANDIBLE
On the lingual side of the angle of mandible,
resorption takes place on the posterio-inferior
aspect and deposition occurs on the antero-
superior aspect and on buccal side vice-versa.
This results in flaring of the angle of mandible as age
advances.

29. LINGUAL TUBEROSITY
•The lingual tuberosity is a direct equivalent of
the maxillary tuberosity, which forms the
major site of growth for the lower bony arch.
•It forms boundary between ramus and body.
•The prominence of the tuberosity is increased
by the presence of large resorption field just
below it .
•This resorption field produces a sizable
depression, the lingual fossa.

30. ALVEOLAR PROCESS
It develops in response to the presence of tooth buds.
As the teeth erupt the alveolar process develops and increases in
height by bone deposition at margins.
In case of absence of teeth, the alveolar bone fails to develop and it
resorbs in the event of tooth extraction.

31. MENTAL PROTUBERANCE
The chin is a specific human characteristic and is found
in its fully developed form in recent man only.
The mental protuberance forms by bone deposition
during childhood.
Its prominence is accentuated by bone resorption that
occurs in alveolar region above it, creating a concavity.

32. CONDYLE
The mandibular condyle has been recognized as an important
growth site.
The head is covered by the condylar cartilage.
It gives rise to:
1. Condyle head and neck of the mandible.
2. The posterior half of the ramus to the level of
inferior dental foramen
It shifts the mandible forward and downward.

33. CORONOID PROCESS
The growth of the coronoid process follows the enlarging ‘V’
principle.
The deposition occurs on the lingual surface.
The vertical dimension of coronoid process also increases.

34. ENLOW’S EXPANDING ‘V’ PRINCIPLE
The growth of the bones occur towards the wide
ends of ‘V’
Bone deposition occurs on inner side of ‘V’ and
resorption occurs on the outer surface.
Deposition also occurs at the ends of the 2 arms of
the ‘V’ resulting in growth movement towards the
ends,

35. ARTERIAL SUPPLY
•The predominant blood supply is
from Inferior alveolar artery.
•It is one of the branches of 1st
part of
Maxillary artery which in turn is a terminal
branch of External Carotid artery .

36. VENOUS DRAINAGE

37. NERVE SUPPLY
•Mainly through the Trigeminal nerve
MANDIBULAR NERVE
• Main trunk
• Anterior trunk
•Posterior trunk

38. LYMPHATIC DRAINAGE
Submental lymph nodes
Submandibular lymph nodes

39. MUSCLE ATTACHMENT OF MANDIBLE
BUCCAL ASPECT LINGUAL ASPECT

40. STRUCTURE OF BONE
The mandible is made up of compact bone on its outer surface and cancellous or
spongy bone on its inner surface.

41. According to Misch , bone density is classified as:-
1. D1-Dense cortical bone.
2. D2-Thick dense to porous cortical bone on crest and
coarse trabecular bone.
3. D3-Thin porous cortical bone on crest and coarse
trabecular bone.
4. D4-Fine trabecular bone.
5. D5-Immature,Non mineralized bone.
QUALITY OF BONE

42. PHYSIOLOGICAL VARIANTS
Males generally have squarer, more prominent mandibles than
females.
This is due to the larger size of the mental protuberance in males
and the decreased gonial angle.
The gonial angle is 90 degrees in males, compared to 110 in
females.

43. In rare instances, a bifid or trifid inferior alveolar canal may
be present.
This can be detected on X-ray as a second or third
mandibular canal.

44. A cleft chin can result from inadequate or absent fusion of
the mandibular symphysis during embryonic development.
This often results in a depression of the overlying soft tissue
at the midline of the mandible.

45. AGE CHANGES IN MANDIBLE

47. RESIDUAL RIDGE RESORPTION
RESIDUAL ALVEOLAR RIDGE is that portion of alveolar ridge and its soft
tissue covering which remains following removal or loss of teeth.
It consists of – denture bearing mucosa, submucosa and periosteum,
and the underlying residual alveolar bone.

48. ATWOOD’s Classification
Order 1 : Pre-extraction
Order 2 : Post-extraction
Order 3 : High, well rounded
Order 4 : Knife-edge
Order 5 : Low, well rounded
Order 6 : Depressed

49. RESORPTION PATTERN IN MANDIBLE
RRR is centripetal in maxilla and centrifugal in mandible.
The mandibular arch appears to become wider, while the maxillary
arch becomes narrower.

50. APPLIED ASPECT OF ANATOMY OF MANDIBLE

51. STRESS
BEARING
AREAS
RELIEF
AREAS
LIMITING
STRUCTURE
PRIMARY SECONDARY
DENTURE BASE AREAS
MANDIBULAR
ARCH

52. LIMITING STRUCTURES

53. PRIMARY STRESS BEARING AREAS

54. SECONDARY STRESS BEARING AREAS
Part of alveolar process and its
soft tissue covering that remains
after extraction of teeth

55. RELIEF AREAS

56. DEVELOPMENTAL ANAMOLIES OF MANDIBLE:
1. AGNATHIA
2. MICROGNATHIA
3. ACQUIRED MICROGNATHIA
4. MACROGNATHIA - often associated with :
PAGETS DISEASE OF BONE
ACROMEGALY
LEONTIASIS OSSEA
5. FACIAL HEMIHYPERTROPHY
6. MANDIBULAR DYSOSTOSIS
7 .CHERUBISM
8. EXOSTOSES
9. TORUS MANDIBULARIS

57. CONCLUSION
•Knowledge of the mandibular anatomy is necessary
for making impression, recording jaw relations,
adjusting dentures for better outcome.

58. REFERENCES
B.D.chaurasia Text book of anatomy vol 3 HEAD AND NECK.
Zarb , bolender, carlson – BOUCHER’S prosthodontic treatment for edentulous
patients,12th
edition
 Inderbir singh ,Human anatomy – 7th
edition.
 S.I. Bhalajhi, Orthodontics- arts and sciences.
 A K Datta ,Human anatomy head and neck .
 Nafis Ahmed Faruqi. Human osteology-[clinical orientation]
 YI – Pingliu ; Peter – mandibular development , remodelling and age changes,
(2010)80(1)97 – 105
 Heba M . Elsabba ,Development and growth of mandible – Oral biology
 A S MONI ,Anatomy -.

59. THANK YOU