mandible

3. CONTENTS
 INTRODUCTION
 DEVELOPMENT OF MANDIBLE
 GROWTH OF MANDIBLE
 ANATOMY OF MANDIBLE
 AGE CHANGES OF MANDIBLE
 APPLIED ASPECTS
 CONCLUSION
 REFERENCES

4. INTRODUCTION
 The mandible or lower jaw, is the largest & strongest bone of the
face.
 The word “Mandible” is derived from Greek word
“mandere” – to masticate or chew.
 The Latin word “ mandibula” – lower jaw.
 It is horse-shoe shaped & the only movable
bone of skull.
 Lower facial skeleton.

5. DEVELOPMENT OF MANDIBLE

6. Prenatal Growth of mandible
 About the 4th week of IU life, the developing brain & pericardium
form two prominent bulges which are separated by the primitive oral
cavity or stomodeum.
 The floor of stomodeum is formed by the bucco-pharyngeal
membrane, which separates it from forgut.
 Pharyngeal arches are laid in approximation
with stomodeum.

7.  In humans, six pairs of pharyngeal arches form on either side of the
pharyngeal forgut.
 The 5th arch disappears after its formation
 1st arch is known as mandibular arch,
 2nd arch as hyoid arch.

8.  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

9.  Each arch contains
1. A cartilaginous supporting element
2. An arch artery
3. An arch-associated cranial nerve
4. A muscular component –
branchiomere

10.  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

11.  Mandibular arch gives of a bud from dorsal
end called maxillary process
 It grows ventro-medially called mandibular
process.
 Mandibular processes of both sides grow
towards each other & fuse in midline.

12. MECKEL’S CARTILAGE:
 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.

13.  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

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

15.  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
Cartilage
• Whole of body except lower
incisive part
• Lower half of ramus upto
mandibular foramen
Membrane

16.  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.
Meckel’s cartilage
Inferior alveolar nerve
Mental branch
Initial site of osteogenesis

17.  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.

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

19.  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

20.  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.

21.  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.)

22. Postnatal Growth Of Mandible
 Overall pattern of growth of the mandible can be represented in two
ways,
1) If the cranium is the reference area ,the chin moves
downward and forward.
2) 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.

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

24.  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.

25.  Alveolar process:
 This develops in response to the developing tooth buds.

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

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

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

29.  Angle:
 The combined deposition and resorption causes flaring of the angle
of the mandible.

30.  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.

31.  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
o Carry away phenomenon

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

33. Body: Outer surface
 Symphysis Menti
 Mental Protuberance
 Mental Foramen
 Oblique Line
 Incisive Fossa / Mental Fossa

34. Body: Inner surface
 Mylohyoid line
 Submandibular fossa
 Sublingual fossa
 Superior genial tubercles
 Inferior genial tubercles
 Mylohyoid groove
 Attachment of
pterygomandibular raphe
 lingual nerve

35. Body: Superior & Inferior border
 The upper border, the alveolar part, contains 16 alveoli for roots of
the teeth.
 The lower border, the base, extends posterolaterally from the
symphysis into that of ramus behind the third molar.

36. Ramus: External/ lateral surface
 Upper & posterior smooth area
 Major rough area

37. Ramus: Medial/ Internal surface
 Mandibular foramen
 Lingula
 Rough area below & behind
mylohyoid groove
 Structures related above &
behind mandibular foramen

38. Ramus: Borders

39. Anterior
Superior Inferior
Posterior

40. Ramus: Coronoid process
 A flat, triangular projection
from the anterosuperior part
of the ramus
 Lateral to pterygoid plate
 Medial to zygomatic process
 Anteriorly continuous with ramus
 Posterior border bounds the
mandibular notch/incisure

41. Ramus: Condylar process
 Strong upward projection from postero-superior part of ramus
 It consists:
1. Upper part- Head
2. Lower part- Neck

42.  Head

43.  Neck

44. Salivary glands

45. Ligaments attached to mandible
 Stylomandibular ligament
 Sphenomandibular ligament
 Temporomandibular ligament
 Pterygomandibular raphe /
ligament

46. Nerve supply of mandible
 The trigeminal nerve- V cranial nerve
 Opthalmic (smallest)
 Maxillary
 Mandibular (largest)
MANDIBULAR NERVE
 Main trunk
 Anterior trunk
 Posterior trunk

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

49. Vascular supply of mandible
 Maxillary artery
 It is divided into 3 parts by the lateral pterygoid.
 Mandibular
 Pterygoid
 Pterygopalatine

50. INFERIOR ALVEOLAR ARTERY
Lingual
branch
Mental
branch
Mylohyoid
branch
Branch
supplying
mandible and
teeth

52. Venous drainage

53. Lymphatic drainage of the mandible

54. AGE CHANGES OF MANDIBLE
At Birth
Adult MandibleGeriatric Mandible
In Childhood

55. APPLIED ASPECTS:
 Dislocation
55

56. Reduction
Downward pressure followed by posterior and upward movement

57. Fracture

58. Surgical consideration:
• Mandibular canal Partially or completely edentulous cases→
placement of implants difficult.
• Injury to the mental nerve  paraesthesia to the skin of the chin, the
lower lip and the labial mucosa
• Injury to the lingual nerve during flap reflection, releasing incisions,
anesthestic injections

59.  External oblique ridge
 Resective surgery difficult because of the amount of bone to be
removed.
 Apical positioning of the flap is difficult in these areas.
 A high buccinator attachment results in a shallow vestibule, making
grafting procedures difficult.

60.  Mandibular tori
 The mucosa over the tori region is usually thin and hence is subject
to tearing.
 Source of autogenous bone for grafting procedures.

61.  Mylohyoid ridge
 A prominent ridge may →broad bony ledge resulting in limited
surgical access and also makes flap reflection difficult.

62.  Coronoid process
 A prominent coronoid process may be in close proximity to the
maxillary tuberosity resulting in limited surgical access
 Genial tubercle
 In cases of severe horizontal bone loss they may pose a problem
during implant placement and flap reflection
 Alveolar process
 Prominent teeth results in marginal tissue recession, bony dehiscence
or fenestration

63. CONCLUSION:
The selection of an appropriate surgical technique that can
best satisfy the treatment goals & objectives is directly influenced by
through knowledge of anatomic relations between bone, soft tissues
& teeth. The study of anatomy of mandible & surrounding structures
is essential

64. REFERENCES:
 Gray’s anatomy, 38th edition.
 Human anatomy, B.D Chaurasia, 4th edition.
 Essentials of human anatomy, A.K Datta, 2nd edition
 Fundamentals of human anatomy, N Chakraborty.
 Human embryology, William Larsen
 Contemporary orthodontics ,Proffit ,4th edition.
 Text book of orthodontics ,S.I Bhalaji ,3rd edition.

66.  Discuss the development, ossification & age changes of the
mandible (20 marks)
 Discuss in detail “ Trigeminal nerve” (20 marks)
 Describe in brief the functional anatomy of TMJ (20 marks)
 Discuss the related structures of maxilla & mandible to
determine the periodontal surgical procedure (20 marks)
 Describe muscles of mastication with their development, nerve
supply & action (20 marks)
 Submandibular salivary gland (5 marks)
 Inferior alveolar nerve (5 marks)
 Describe branches of mandibular nerve & structures supplied by
them (5 marks)