Anatomy and development of mandible reference from b.d. chaurasia & embryology and content from osteology also

2. ANATOMY& DEVELOPMENTOF
MANDIBLE

3.  INTRODUCTION
 ANATOMY OF MANDIBLE
 Parts
 Attachments and its relations
 Nerve supply
 Vascular supply
 Foramina and its relations
 DEVELOPMENT OF MANDIBLE
 Prenatal growth
 Postnatal growth
 Age changes
 Anomalies of development

4.  The word mandible derived from Latin word
mandibula- "jawbone" or inferior maxillary
bone.
 It forms the lower jaw and holds the lower
teeth in place.
 It is the largest, strongest and lowest bone in
the face.

5.  Only movable bone in the skull
 It consists of an anterior Horseshoe-shaped body, and of
two rami that project upwards from the posterior part of
the body.
 It provides structure and protective support
for the oral cavity.
 The mandible is articulated in ball and socket fashion at
the condylar process.
 Strength resides in its dense cortical plates.

6. ANATOMY
OF
MANDIBLE

7. Mandible
Body Two Rami
Surfaces SurfacesBorders Borders Processes
External/
Outer
Internal/
Inner
Superior/
Alveolar
Inferior/
Base
CoronoidCondyloidLateral/
External
Medial/
Internal
Anterior Posterior Superior Inferior

8.  Horseshoe-shaped BODY
 Has two surfaces EXTERNAL and
INTERNAL surfaces ,
 Two borders UPPER and LOWER borders.

9. 1. SYMPHYSIS MENTI : The line at
which the right and left halves of the
bone meet each other. It is marked by a
faint ridge.
2. MENTAL PROTUBERANCE : median
triangular projecting area in the lower
part of the midline.
3. MENTAL FORAMEN : It lies below
the interval between the premolar teeth
4. EXTERNAL OBLIQUE LINE :
Continuation of the sharp anterior
border of the ramus of mandible.
5. INCISIVE FOSSA : Depression that
lies just below the incisor teeth

13. 1. MYLOHYOID LINE :
Prominent ridge that runs
obliquely downwards and
forwards from below the third
molar tooth to the median area
below genial tubercle.
2. SUBMANDIBULAR FOSSA : It
lies below the mylohyoid line,
which lodges the submandibular
gland
3. SUBLINGUAL FOSSA : It lies
above the mylohyoid line, which
lodges the sublingual gland
4. GENIAL TUBERCLES :
Posterior surface of the symphysis
menti is marked by four small
elevations called the superior and
inferior tubercle

14. 5. MYLOHYOID GROOVE : Extends
from ramus to the body below the
posterior end of the mylohyoid line.
6.UPPER ALVEOLAR BORDER : It
bears socket for the teeth.
7. LOWER BORDER /BASE :
8. DIGASTRIC FOSSA : Near the midline
the base shows an oval depression.

15.  SUPERIOR BORDER
(ALVEOLAR BORDER)
 It is hollowed into cavities for the
reception of the teeth, these cavities
are sixteen in number, and vary in
depth and size according to the teeth
which they contain.

16.  is rounded, longer
than the superior,
and thicker in front
than behind.

17.  Is quadrilateral
 2 surfaces
1. Lateral
2. Medial
 4 borders
1. Superior
2. Inferior
3. Anterior
4. Posterior
 2 processes
1. Coronoid
2. Condylar

18.  Lateral surface – flat with
oblique ridges
 Medial surface –
Features-
1. MANDIBULAR FORAMEN : It
lies little above the centre
of ramus at the level of
occlusal plane. It leads into
mandibular canal.
2. LINGULA : Anterior margin
of foramen marked by
tongue shaped projection

19. 3. MYLOHYOID GROOVE :
Begins just below
mandibular foramen,
runs forwards and
downwards to be
gradually lost over the
submandibular fossa.
4. UPPER BORDER -Forms
mandibular notch
5. LOWER BORDER- Forms
angle( junction of the
body and ramus )

20.  The lower border of the ramus is
thick, straight, and continuous with
the inferior border of the body of
the bone. At its junction with the
posterior border is the angle of the
mandible, and is marked by rough,
oblique ridges on each side.
 The upper border is thin, and is
surmounted by two processes, the
coronoid in front and the
condyloid behind, separated by a
deep concavity, the mandibular
notch.

21.  Anterior border- thin &
continuous with coronoid process
 Posterior border- thick &
extends from condyle to angle
AB

22. CORONOID PROCESS
 Flat ,triangular
 Upward and forward projection
from anterolateral part of ramus
 Anterior border continuous with
anterior border of ramus
 Posterior border bounds the
mandibular notch

23. CONDYLAR PROCESS
 Upward projection from postero
superior part of ramus
 Apically enlarged as head of
condyle.
 Articulates with temporal bone’s
mandibular fossa to form
temperomandibular joint
 Lateral aspect palpable in front of
tragus
 Pterygoid fovea anterior to neck

24. 1. External oblique line- origin to
buccinator, depressor
inferioris, depressor anguli
oris
2. Incisive fossa -origin of
mentalis, mental slips of
orbicularis oris
3. Mylohyoid line – origin to
mylohyoid muscle ,
attachment to superior
constrictor of pharynx,
pterygomandibular raphae
4. superior genial tubercles -
genioglossus

27. 5. Lower genial tubercles –origin to
geniohyoid
6. Diagastric fossa- anterior belly of
diagastric
7. Lower border -deep cervical fascia
and platysma
8. Lateral surface of ramus - insertion
for masseter
9. Posterosuperior lateral surface of
ramus-parotid gland

28. 10. Lingula-sphenomandibular ligament
11. Medial surface of ramus-medial
pterygoid muscle attachment
12. Apex of coronoid process - temporalis
attachment
13. Pterygoid fovea - lateral pterygoid
muscle
14. Lateral surface of neck - attachment to
lateral ligament of temperomandibular
joint , parotid gland

29. ARTERY SUPPLY OF MANDIBLE; Mainly by
Maxillary artery, Branch of external carotid artery By
its branches, mainly through inferior alveolar artery
INFERIOR ALVEOLAR ARTERY
Lingual
branch
Mental
branch
Mylohyoid
branch
Incisive
artery

31.  Drains into
Internal jugular vein
and external jugular
vein through
maxillary vein, facial
vein and pterygoid
plexus

32.  Mainly through the trigeminal nerve - V cranial
nerve
MANDIBULAR NERVE
 Main trunk
 Anterior trunk
 Posterior trunk

33. Posterior division of the mandibular nerve
Mylohyoid
nerve
Inferior alveolar nerve
Mental
nerve
Incisive
nerve
Auriculotemporal
nerve
Lingual

35. 1. Mental foramina - mental
nerve and vessels
2. Mandibular notch - massetric
nerve and vessels
3. Medial side of neck -
auriculo temporal nerve
4. Mylohyoid groove -
mylohyoid nerve and vessels
5. Mylohyoid groove in front of
ramus - lingual nerve

36.  Mandibular canal and
foramina - inferior alveolar
nerve and vessels
Articulation
 Mandibular process of
temporal bone and
condylar part of mandible
articulate to form
temporomandibular joint.

37.  DEVELOPMENT OF MANDIBLE

38. PRENATAL GROWTH OF
THE MANDIBLE

39.  Around the 4th week of intrauterine
life a shallow depression appears in
the embryo it corresponds to future
mouth called as – stomadeum.
 Between the stomadeum and
pericardium, mesodermal thickenings
develops, these are called as
pharyngeal arches or brancheal
arches.

40.  In humans, six pairs of pharyngeal
arches form on either side of the
pharyngeal foregut.
 1st arch is known as mandibular arch,
 2nd arch as hyoid arch.
 Other arches don’t have any specific
names
 The 5th arch disappears after its
formation

41.  Each arch has
1. Outer covering of ectoderm
2. An inner covering of endoderm
3. Core of mesoderm.
 Arches are separated from each other by
1.Pharyngeal cleft or groove externally
2.Pharyngeal pouches internally

42.  With in the arch,
1. A cartilaginous supporting
element
2. An aortic arch
3. An arch-associated cranial
nerve
4. A muscular component –
branchiomere

43.  The development of face begins
in the 4th to 8th week of intra-
uterine life.
 The face is derived from
 An unpaired frontonasal process
 A pair of Maxillary process
 A pair of Mandibular process

44.  Mandibular arch gives of a bud
from dorsal end called maxillary
process
 It grows ventro-medially, it is
called as mandibular process.
 Mandibular processes of both
sides grow towards each other &
fuse in midline by fibrous tissue.

45.  FORMATION OF BONE : Mainly by two
mechanisms
• Intramembranous ossification
• Endochondral ossification

46. 46
Mesenchymal
condensation
Increased vascularity
A membrane is formed
( collage fibres)

47. 47
Mesenchymal cells enlarge
to become osteoblast
Secretion of gelatinous
matrix
Fibres swell
up(osteoid)

48. Deposition of calcium salts
Layer of osteoid becomes
lamellas of bone
(trabeculae)
Anastomosing network of
trabeculae form spongy or
cancellous bone
Continuing appositional
growth & remodelling of bony
trabeculae - convert cancellous
bone into compact bone
48

49. 49
Mesenchymal condensation
– differentiation into
chondroblasts – cartilage
model with perichondrium
Capillaries grow into
perichondrium – inner layer
differentiates into
osteoblasts – thin collar of
bone matrix forms
Perichondrium is now called
periosteum
Thin collar of bone –
subperiosteal bone

50. 50
 osteogenic cells & periosteal
capillaries invade cartilage model -
periosteal bud forms – initiate
primary centre of ossification (
primary areolae)
 Osteogenic cells give rise to
osteoblasts- arranged along
secondary areolae
 Layer of ossein fibrils embedded in
gelatinous intercellular substance
 Osteoid is calcified and a lamellae
of bone is formed

51.  Mandible is the second bone to ossify in the body.
 It is partly membranous & partly cartilaginous in
ossification.
• Incisive part below symphysis menti
• Coronoid
• Condyloid process
• Upper half of ramus
Cartilage
• Whole of body except lower incisive
part
• Lower half of ramus upto mandibular
foramen
Membrane

52.  Each half of mandible ossifies from only one
centre of ossification at 6th week of
intrauterine life, in the mesenchymal sheath
of meckel’s cartilage near the future mental
foramen.

53.  The ventral end of meckel’s cartilage ossifies
from parent centre during 10th week and
forms the incisive part.
Secondary cartilages.
Condyloid cartilage
Coro
noid
cartil
age
Symphyseal cartilage.

54. MECKEL’S CARTILAGE:
 Cartilage of first arch.
 Meckel’s cartilage is derived from 1st
branchial arch around 41st – 45th day of
IU life.
 It extends from the cartilagenous otic
capsule to the midline.
 Provides a framework around which the
growth of the mandible occurs.

55.  Meckel’s cartilage lacks the enzyme alkaline
phosphatase found in the ossifying cartilages, thus
precluding its early ossification.
 A major portion of the Meckel’s cartilage
disappears. It persists until as long as the 24th
week IU life

56.  Remaining part develops:
1. Mental ossicles.
2. Incus & Malleus.
3. Spine of sphenoid bone.
4. Anterior ligament of malleus.
5. Spheno – mandibular
ligament.

57.  The 1st structure to develop in the primordium of the lower
jaw is the mandibular division of the trigeminal nerve.
 6th week of IU life → a single ossification centre for each
half of mandible in the region of the bifurcation of inferior
alveolar nerve.

58.  Ossification spreads below & around the inferior alveolar nerve.
 The Meckel’s cartilage is surrounded by bone and ossification then
stops at the lingula
 The bony plate extends towards the midline where it comes to lie in
close relationship with the bone forming on the opposite side.
 However, two plates of bone remain separated at the Mandibular
symphysis by fibrous tissue.
 Bony union takes place at around 18 months after birth.

59.  Endochondral bone formation seen in 3 areas.
 They appear between the 10th and 14th week of IU life.

60.  Condylar process:
 5th week of IU life - mesenchymal condensation at the ventral
aspect mandible.
 10th week - develops into a cone shaped cartilage.
 14th week- begins ossifying.
 4th month - fuses with the Ramus of the developing mandible.
 It persists as Growth cartilage & Articular cartilage

61.  Coronoid process:
 10-14th week of IU life→ Secondary accessory cartilage appear in
the region of coronoid process.
 It grows as a response to Temporalis muscle.
 This accessory cartilage fuses with the ramus and disappears by
birth.

62.  Mental region:
 On either side of the symphysis, one or two
cartilages appear which ossify to form the mental
ossicles at 7th month of IU life.
 These get incorporated into the intramembranous
bone when the symphysis ossify completely ( 1st
year of post natal life.)

63. POSTNATAL GROWTH OF
THE MANDIBLE

64.  According to the data from the vital staining
experiments, the posterior surface the ramus, the
condyle and coronoid process are principal sites of
growth.
 Growth is quite general during the first year of life
with all surfaces showing bone apposition.
 Mandibular growth becomes more selective.

65.  The mandible can be divided into several sub-units like
 Chin
 Alveolar process
 Body
 Lingual tuberosity
 Ramus
 Angular process
 Coronoid process
 Condylar process

66.  Chin:
 1-2 years→ chin prominence is seen
 The mental protuberance forms by bone deposition
 The change in the contour occurs by following two
mechanism.
1) The area just above the chin and
the base of the alveolar process,
is a resorptive area.
2) There is forward translation of
chin as mandible grows forward.

67.  Alveolar process:
 This develops in response to the developing tooth
buds.

68.  Body: (corpus)
 The length of the body increases as the ramus moves
posteriorly

69.  Lingual tuberosity:
 It forms the boundary
between the ramus & body
 A combination of the
resorption and deposition
accentuates its
prominence.

70.  Ramus:
 The ramus is seen to move posteriorly due to deposition
at its posterior border and resorption on its anterior
border

71.  Angle:
 The combined deposition and resorption causes
flaring of the angle of the mandible.

72.  Coronoid process :
 Enlow’s enlarging “V” principle.
 Birth: Coronoid process is at higher
level than condyloid process.
 Childhood: Coronoid & condyloid
processes are at same level.
 Adult: Condyloid process is at
higher level.

73.  Condyle:
 Condylar growth rate increases at
puberty and reaches its peak by
12-14 years.
 The growth ceases at around 20
years
 Role of condyle:
o Primary displacement

74. AT BIRTH :
 The two halves of the mandible are united by a
fibrous symphysis menti.
 At this stage the body is a mere shell,
enclosing imperfectly separated sockets of
deciduous teeth.
 The mandibular canal is near the lower border
 The mental foramen opens below the first
deciduous molar and is directed forwards.
 The coronoid process projects above the
condyle
 The angle of the mandible is obtuse (above
140degrees or more) because the head is in
line with the body.

75. IN ADULTS :
 The mental foramen opens midway
between the upper and lower borders as
the alveolar and sub-alveolar regions are
about equal in depth.
 The mandibular canal nearly parallels the
mylohyoid line
 The angle between the lower border of the
body and a plane touching the posterior
surface of the condyle above and ramus
below diminishes as ramal height increases
with age (about 110 –120degrees)

76. In OLD AGE :
 Bone is reduced in size as teeth are lost
and alveolar region resorbed
 The mandibular canal and the mental
foramen are nearer the superior border
 The ramus becomes oblique as angle
becomes obtuse (140degrees) and the neck
inclined backwards.

78. At Birth
Adult MandibleGeriatric Mandible
In Childhood

79.  Agnathia : Agnathia is an
extremely rare congenital
defect characterized by
absence of the maxilla or
mandible. More commonly
only a portion of one jaw is
missing.
 Micrognathia : It likely
means a small jaw. Many
cases of apparent
micrognathia are due not
to an abnormally small jaw
in terms of absolute size,
but rather to an abnormal
positioning or an abnormal
relation of one jaw to the
other or to the skull which
produces the illusion of
micrognathia.

80.  Macrognathia : It refers to
the condition of abnormally
large jaws. It may be
associated with
 Pagets disease
 Acromegaly
 Leontiasis ossea, a form of
fibrous dysplasia.

81.  Facial hemi atrophy :
 It is a progressive atrophy of
some or all of the tissues on one
side of the face, occasionally
extending to other parts of the
body. The etiology is unknown.
 As the dental effects the
hemiatrophy of the lips and the
tongue is reported, the roots of
the teeth may exhibit deficiency of
root development and reduced
growth of the jaws on the
affected side. Eruption of teeth on
the affected side may also be
retarded. There is no specific
treatment.

82.  Cleft lip and cleft palate
 Cleft lip occurs due to
failure of fusion of maxillary
process with the medial and
lateral nasal process.
 Cleft palate is due to
failure of fusion between
maxillary process and
frontonasal process.
 They can be treated by
surgical management or by
fabrication of passive
obturator.

83.  In order to construct a prosthesis a dentist
requires an understanding of the
foundation,it’s components,its properties and
qualities must be analysed to assure proper
support for the proposed prosthesis.

84.  Inderbersingh :text book of human osteology.
 B.D.Chaurasia: human osteology.
 Inderbersingh : human embryology.
 Warren .H.Lewis.-Gray’s anatomy of the human
body.2000:20th edition
 Langman’s medical embryology – T.W. Sadler, 5th
edition.
 Oral histology, development, structure and function
– a.R. Ten cate, 4th edition