surgical anatomy of mandible with applied aspects of various structures.

1. GOOD MORNING

2. Department of Oral and Maxillofacial Surgery
Surgical Anatomy of Mandible
Date: 10/May/2019
Presented By:
Dr. Samarth Johari

3. INTRODUCTION
• Mandible Greek word ‘mandere’ which means to masticate or
chew
Latin word ‘mandibula’ which means lower jaw
• A ‘U’ shaped bone
• Largest and the strongest bone of the face
• Forms skeleton of lower jaw, thus known as the ‘lower facial skeleton’

4. EMBRYOLOGY
• Pharyngeal arches:
 Rod like
thickenings of
mesoderm
 Initially 6 pairs
of arches but
the fifth pair
soon
disappears and
only five pairs
remain

5. Arch Nerve of Arch Muscles of Arch
First Mandibular Medial and lateral pterygoids,
temporalis, mylohyoid, anterior belly of
digastric, tensor tympani, tensor palate
Second Facial Muscles of face, occipitofrontalis,
platysma, stylohyoid, posterior belly of
digastric, stapedius, auricular muscles
Third Glossopharyngeal Stylopharyngeus
Fourth Superior laryngeal
Muscles of pharynx
Muscles of larynxSixth Recurrent laryngeal

6.  Cartilage of 1st arch is called
Meckel’s cartilage or
mandibular arch and it
rise to incus and malleus of
middle ear.
 Cartilage of 2nd arch forms
stapes, styloid process and
part of hyoid bone
 Cartilage of 3rd arch forms
greater part of hyoid bone
 Cartilage of 4th and 6th
arches give rise to cartilage
of larynx

7.  Cartilages contributing to mandible:
i. Anterior ends of Meckel’s cartilages
These are invaded by bone from parent centres at 10th week of
IUL
ii. Coronoid cartilages
appear at 10th week of IUL & disappear before birth
iii. Condylar cartilages
appear at 10th week of IUL & persist till 3rd decade
iv. Cartilagenous nodules
1 or 2 nodules appear on each side of symphysis menti
at about 10th week of IUL
these ossify to form mental ossicles at about 7th month
of IUL & fuse with body at the age of 1 year

8.  Parts of mandible that are derived from the cartilage:
I. Incisive part below the incisor teeth
II. Coronoid & condylar processes
III. Part of ramus above the level of mental foramen
At birth, mandible consists of 2 halves that are connected at the
symphysis menti
Bony union starts from below upwards during 1st year of age &
is completed at the end of 3rd year

9. • Development of mandible:
 Prenatal growth-
 Ossification type- intramembranous
 Timing- 6th week of intrauterine life
 No. of ossification centres- 2 (right & left)
 Mandibular division of trigeminal nerve is the 1st structure
to develop in primordium of lower jaw
 This prior presence of the nerve is considered to be
important because it is necessary to induce osteogenesis
by the production of neurotrophic factors

10.  Derived from the ossification of an osteogenic membrane formed
from ectomesenchymal condensation at around 36 to 38 days IU
 The resulting intramembranous bone lies lateral to Meckel’s
cartilage of the first (mandibular) arch
A single ossification
center for each half of
the mandible arises in the
6th week IU, in the region
of the bifurcation of the
inferior alveolar nerve
and artery into the
mental and incisive
branches

11.  Bone begins to develop lateral to Meckel’s cartilage during the 7th
week and continues until the posterior aspect is covered with
bone
 Ossification stops at the point, which will later become the
mandibular lingula, and the remaining part of the Meckel’s
cartilage continues on its own to form the sphenomandibular
ligament and the spinous process of the sphenoid
 Secondary accessory
cartilages appear between
the10th and 14th weeks IU to
form the head of the condyle,
part of the coronoid process,
and the mental protuberance

12.  Post natal growth-
 At birth the two rami of the mandible are quite short
 Condylar development is minimal and there is practically no
articular eminence in the glenoid fossa
 Thin line of fibrocartilage and connective tissue exists at the
midline of the symphysis to separate right and eft mandibular
bodies
 Between four months of age and the end of the first year, the
symphyseal cartilage is replaced by bone
 During the first year of life, appositional growth is specially
active at the alveolar border, at the distal and superior surfaces
of the ramus, at the condyle, along the lower border of the
mandible and on its lateral surfaces

13.  After the first year of life condyle
does show considerable activity as
the mandible moves and grows
downward and forwards
 Heavy appositional growth occurs
on the posterior border of the
ramus and on the alveolar process.
Significant increments of growth are
still observed at the tip of coronoid
process
 Resorption occurs along the
anterior border of the ramus
lengthening the alveolar border and
maintaining the antero-posterior
dimension of the ramus

14.  Scott divides the mandible into three basic types of bone: basal,
muscular and alveolar
(gonial angle and the coronoid process)
is under the influence of the masseter,
medial pterygoid and temporalis muscle
a tube like central foundation running
from the condyle to the symphysis
Alveolar bone exists to hold the teeth and it is gradually resorbed in
the event of tooth loss

15.  According to Moss, mandible is
composed of micro skeletal
units
 coronoid process which is
under the influence of
temporalis
 Gonial angle that is under the
influence of temporalis and
medial pterygoid muscle
 alveolar process which is under
the influence of the dentition

16. PARTS OF MANDIBLE
I. Body:
• Horse shoe shaped
• Is thick & has rounded lower borders & carries alveolar process on its
upper border
• Extends antero-posteriorly from chin at mid symphysis to anterior limit
of ramus
• It presents as-
 Two surfaces
External surface
Internal surface

17.  Two borders
Superior border of body (alveolar process)
Inferior border or base of mandible
Body
Surfaces
External Internal
Borders
SuperiorInferior

18. EXTERNAL SURFACE:
• Symphysis menti- faint ridge on upper part of midline indicating fusion
of 2 halves of mandible
• Mental protuberance- triangular area in lower part of midline. Its upper
angle marks lower end of symphysis menti
• Mental tubercle- on each side of mental protruberance marking
its lower angle
• Mental foramen- between premolar teeth
• Incisive fossa- below incisors. Mentalis & orbicularis originate from this
fossa

19. Parasymphysis region lateral to the
mental prominence is a naturally
weak area susceptible for
parasymphyseal fracture. This is
because of the presence of incisive
fossa, long root of canine and
mental foramen.

20. • Oblique line- continuation of
anterior border of ramus on
external surface of body &
runs downwards & forwards
to reach mental tubercle
Muscles attached to it from
anterior to posterior:
a) Depressor labii inferioris
b) Depressor anguli oris
c) Buccinator (below
molars)
Junction of ramus & body is
marked by courses of facial
artery & vein
Pulse of facial artery can easily be
felt at lower border of mandible or
slightly above it & in front of
masseter muscle

21. Applied Anatomy Of Facial Artery In View
Of Surgeries In The Region Of Angle Of
Mandible
 When performing operative procedures
on the lower premolars and molars the
facial artery can be severed accidentally
if an instrument enters the buccal
region.
 Deep incisions may endanger the facial
artery.
 Precaution : The incision should be
made downward and outward instead
of straight downward.

22. Triangle of Marginal Mandibular Branch
(MMB)
The advantages of MMB landmark triangle:
1. Locate the marginal mandibular branch
using palpable reference points, reliable and
easy to identify by clinical examination and
surgical exploration.
2. Make precise measurements to facilitate
the approach of the upper and lateral
region of the neck.
3. Specify the position of the furthest MMB
below the lower border of the mandible.
4. Guide the surgeon to avoid or locate the
MMB.
5. Determine the location of the incision.
AB = The distance between the angle of the
mandible and the intersection of MMB with LBM.
AX = The distance between the angle of the
mandible and the intersection of the facial vein
with LBM.
AY = The distance between the angle of the
mandible and the projection of point C which is
the position of the MMB farthest from LBM.
CY = The distance where the MMB is farthest
down LBM.
El Ayoubi Ali, Laamarti Sara, El Ayoubi Said, Bjijou Younes, Bouchikhi Mohamed.
Triangle of Marginal Mandibular Branch (MMB): Anatomical Zone, Constant
Reference of the MMB in Cervical Surgical Position. International Annals of
Medicine. 2017;1(5).

23. INTERNAL SURFACE:
• Mylohyoid line- oblique ridge extending downwards & forwards from
behind 3rd molars (1cm below alveolar border) to midline near lower
border between digastric fossae.
• Submandibular fossa- present below posterior part of mylohyoid line &
lodges following structures:
a) Submandibular gland
b) Facial artery
c) Submandibular lymph nodes
• Sublingual fossa- area above anterior part of mylohyoid line & lodges
sublingual salivary gland

25. • Genial tubercles- irregular elevations on either
side of midline just above anterior ends of
mylohyoid lines. Upper genial tubercle provides
attachment to genioglossus muscle while lower
genial tubercle gives origin to geniohyoid
muscle
• Attachment of pterygomandibular raphae-
attached in continuation with origin of superior
constrictor just behind 3rd molar
• Attachment of superior constrictor of pharynx-
originates above posterior end of mylohyoid line
• Relation of lingual nerve- between origin of
superior constrictor & mylohyoid muscle

27. Applied aspect in view of genial tubercle
 The genial tubercle at midsymphysis is the attachment point for the
genioglossus muscle & it houses the lingual foramen, through which the
lingual artery courses
 This artery is approximately 1–2 mm in diameter and can be seen in
cross-sectional views to anastomose with the incisive canal
 This artery may be injured during the drilling procedures causing
elevation of tongue due to hematoma in floor of mouth which may
further lead to respiratory collapse
Robert J. Miller, Warren C. Edwards, Jonathan H. Cohen; maxillofacial
anatomy: the mandibular symphysis; J of Oral Implantology 2011.37:745-753

28. Fig.: Multiple perforating vessels on the lingual
surface of the anterior mandible-
(A) Lingual artery (B) Sublingual artery
(C) Submental artery (D) Mylohyoid artery
(E) Secondary mylohyoid artery
 Injury to the sublingual artery has been
observed when sharp instruments or
rotating discs slips off a lower tooth and
injure the floor of the mouth.
 If this injury is in the region of the
premolar or the first molar, the sublingual
artery may be severed where it is in
considerable volume.
 The hemorrhage from this artery may then
be a serious incident.
 Management :
• Local clamping of the artery can be
attempted, although it is rather difficult.
• If attempts to stop the bleeding at the
place of injury fail, the lingual artery
must be ligated.

29. SUPERIOR BORDER:
• Also known as alveolar part of mandible
• Consists of sockets which my be single or subdivided by septa
according to teeth which they contain

30. INFERIOR BORDER:
• Also known as base
of mandible
• Digastric fossa is a
depression on each
side of midline &
receives attachment
of anterior belly of
digastric

31. II. Ramus:
• Has 2 surfaces (lateral &
medial), 4 borders
(upper, lower, anterior
& posterior) & 2
processes (coronoid &
condylar)
LATERAL SURFACE-
• small posterosuperior area
is related to parotid gland
& rest of the part provides
attachment to the
masseter

32. MEDIAL SURFACE-
• Mandibular
foramen & canal
• Lingula
• Mylohyoid groove
• Medial surface of
ramus between
mylohyoid groove
& angle of mandible
is marked by ridges
which is meant for
the attachment of
medial pterygoid

33. UPPER BORDER-
• Thin
• Forms mandibular
notch
• Massetric nerve &
vessels cross the
mandibular notch

34. Applied Anatomy Of Masseteric Artery
A careful dissection of 16 intact human
cadaveric head specimens revealed the
location of the masseteric artery in relation
to 3 points:
1) the anterior-superior aspect of the
condylar neck = 10.3 mm;
2) the most inferior aspect of the articular
tubercle = 11.4 mm;
3) the inferior aspect of the sigmoid notch =
3mm
Journal of Oral and Maxillofacial Surgery.
2009;67 (2) : 369–371

35. LOWER BORDER-
• Backward
continuation of base
of mandible
• Meets with posterior
border of ramus to
form angle of
mandible
Clinical angle represents
the junction between the
alveolar bone and the
ramus of the mandible
where the internal oblique
ridge originates.
Surgical angle is the
junction between the
ramus and the body
where the external
oblique ridge
originates.
Anatomical angle
denotes the union
where the inferior
border of the
mandible joins the
posterior border of
ramus.

36. The bony trajectories transmit and
disperse the forces of mastication
towards the condyles from the body, thus
preventing injury to middle cranial fossa
The body of the mandible is considerably
thicker than the ramus and the junction
of these two portions constitutes a line of
structural weakness. Impacted 3rd molars
adds up the risk for angle fracture
Angle fractures are commonly seen due
to the curvature of trajectories in this
region

37. ANTERIOR BORDER-
• Continuous above
with coronoid
process & below
with alveolar border
of body
• Temporalis is
inserted to this
border & adjoining
medial surface

38. POSTERIOR BORDER-
• Continuous above
with condylar
process
• Meets with lower
border to form
angle of mandible

39. CORONOID PROCESS-
• Triangular upward
projection from
anterosuperior part of
ramus
• Anterior border
continuous with anterior
border of ramus &
posterior border forms
part of mandibular
• Temporalis is attached
to medial surface, apex
& margins of coronoid
process

40. CONDYLAR PROCESS-
Condylar Head:
• An ovoid process located
above the mandibular neck
• It is the articulating surface of
the
mandible
• Convex in all directions
but wider latero-medially
(15-20 mm) than
antero-posteriorly (8-10 mm)
• Has a medial & lateral
pole

41. Medial Pole
 Directed more posteriorly
 If long axes of 2 condyles are
extended medially, they meet
at basion on anterior limit of
foramen magnum
 Forms an angle ranging from
145º to 160º
 Extends sharply inward from
plane of ramus

42. Lateral pole
 Rough, bluntly pointed
 Articular surface lies on its
antero-superior aspect, facing
posterior slope of articular
eminence of temporal bone
 Projects moderately form
plane of ramus

43. Condylar Neck:
• Constricted part below neck
• Pterygoid fovea on its anterior
aspect gives attachment to
lateral pterygoid muscle
• Medially related to
auriculotemporal nerve above
& maxillary artery below

44. According to Fonseca
(1974)
Whenever there is a blow
mental region while the
mouth is open, the medial
& the lateral poles of the
condyle strike against the
medial & the lateral
elevated margins of the
glenoid fossa & only a
round part impinges the
thin central part of the
preventing the penetration
of condyle in the middle
cranial fossa
According to Yale et al
(1963), slender neck of
the mandible is liable
to fracture as a result
of violence received
at the anterior region

46. Applied Anatomy Of Facial Nerve In
View Of Surgeries In Region of
Condyle Or TMJ Surgeries
 Exits skull at stylomastoid formen
 Incise the superficial layer of
temporalis fascia & periosteum
over arch within 8mm boundary,
prevent damage to branches of
upper trunk

47. ROLE OF MUSCLES IN DISPLACEMENT OF
FRACTURED SEGMENTS
Strong muscles attached to
mandible causes displacement of
fractured segments & are divided
into 3 groups:
i. Depressor group-
includes geniohyoid &
digastric muscles
these cause posterior &
inferior displacement of fractured
anterior mandibular segment

48. ii. Elevator group-
consists of
masseter, temporalis &
medial pterygoid
their contraction
causes upward
displacement of fractured
segments if the fracture
occurs in region of angle
of mandible

49. ii. Protrusor group-
consists of lateral
pterygoid muscle
it causes forward
displacement of head in
cases of fracture of
mandibular neck

51. AGE CHANGES IN MANDIBLE
I. Children:
• Body of mandible is more like a
shell consisting of sockets for both
deciduous & permanent teeth
• Angle of mandible measures around
140º
• Coronoid process is above the level
of the condylar process
• Mandibular canal & mental foramen
are close to lower border of body

52. II. Adult:
• Alveolar & subalveolar parts of
body are of equal depths
• Angle of mandible measures
110º
• Condylar process projects
above level of condylar
process
• Mandibular canal runs parallel
to mylohyoid line
• Mental foramen is at midway
between upper & lower
borders of body

53. III. Old Age:
• Resorbed alveolar part
• Angle of mandible
measures about 140º
• Neck of mandible is
bent backwards making
level of coronoid
process higher than
level of condylar process
• Mandibular canal and
mental foramen are
closer to upper border
of body

54. 1. Central blood supply via the
inferior alveolar artery except the
coronoid process , which is
supplied by temporalis muscle
vessels
2. Peripheral blood supply via the
periosteum. Periosteal supply,
which generally runs parallel to
cortical surfaces of bone, giving
off nutrient vessels that penetrate
cortical bone and anastomose
with the branches of inferior
alveolar artery.
BLOOD SUPPLY OF THE
MANDIBLE

55. • It is basically derived from mandibular branch of trigeminal
nerve.
1. The long buccal nerve: The anterior division of the
mandibular nerve. It supplies mucosa opposite the last
three mandibular molars on their buccal aspect.
2. The inferior alveolar nerve: The posterior division of the
mandibular nerve. It supplies all lower jaw teeth, lower lip,
buccal mucosa from the incisors to the premolar & the skin
over the chin.
3. The lingual nerve: The posterior division of the mandibular
nerve. It gives sensory supply to the anterior 2/3rd of
tongue, the mucosa on the lingual aspect of the lower
teeth & the floor of mouth.
NERVE SUPPLY OF MANDIBLE

57. Applied aspect in view of inferior alveolar nerve & incisive nerve
 two-thirds of the inferior alveolar nerve (IAN) exits at the mental foramen
while remaining one-third continues through the incisive canal and
anastomoses with the contralateral side & is the neurovascular supply to
all anterior teeth and the chin closer to the midline
 Clinicians performing autogenous block graft procedures often prefer
symphyseal bone for the shape and volume of the graft needed
 in this block harvesting procedure incisive nerve is inadvertently resected
causing altered sensation in the affected anterior teeth even after healing
Robert J. Miller, Warren C. Edwards, Jonathan H. Cohen; maxillofacial anatomy: the mandibular
symphysis; J of Oral Implantology 2011.37:745-753

58. • Most of the mandible & lower teeth drain
into the submandibular group of lymph
nodes.
• Except a small wedge in the symphysis region
& the lower incisors which drain into the
submental group of lymph nodes.
• From the submental group the lymph drains
to the submandibular group of nodes.
• Most of the submandibular nodes ultimately
drain to the jugulo-omohyoid group of deep
cervical lymph nodes.
• Few extremely posterior submandibular
nodes drain to jugulo-digastric group of
deep cervical lymph nodes.
LYMPHATIC DRAINAGE

59. VARIATIONS IN THE MANDIBULAR ANATOMY
1. Bifurcated Mental Foramen:
 The secondary smaller foramen
may be viewed as artifact on a
periapical or panoramic film.
 This neurovascular component
may be inadvertently injured or
transected during surgery, leading
to paresthesia of the lip and chin
on that side
Fig.: Distal bifurcated
branch of the mental
nerve
Fig.: Axial tomography
tracing the path of a
bifurcated mental nerve
Robert J. Miller, Warren C. Edwards, Jonathan H. Cohen; maxillofacial anatomy: the mandibular
symphysis; J of Oral Implantology 2011.37:745-753

60. 2. Superior Genial Foramen:
 Occasionally, periapical or panoramic films may indicate
an anterior extension to the IAN.
 Some of these foramina can have a diameter of up to 2
mm, indicating a substantial neurovascular component
exiting to supply the chin
 Reports of substantial bleeding in the symphysis after
raising may be attributable to these larger vessels
 Following block graft harvesting, paresthesia of the
midline chin area has been reported and may be the
result of transection of these anterior neurovascular
components
 Injury to these vessels can be avoided by limiting the
apical extension of flaps during implant placement and
by harvesting block grafts closer to the midline
Fig.: Cross
section of
superior
genial
foramen
at the
cuspid
position
Fig.: Reconstructed 3-
dimensional image
showing positions and
relative sizes of the
superior genial and
mental foramina

61. 3. Submental artery:
 Branches of the submental
artery are seen to
anastomose with the incisive
canal at, or adjacent to, the
symphyseal midline
a branch of the facial artery & is
considered to be the main
arterial blood supply to the floor
of the mouth and the
lingual gingival
Fig.: submental artery anastomoses
with the incisive canal at
midsymphysis

62.  Runs medial to the mandible and
may insert into the mandibular
symphysis at the inferior border
 Transection of the submental
artery requires deep dissection in
the floor of the mouth and ligation
of the facial artery
 Also supplies the submandibular
lymph nodes, the submandibular
salivary gland, the mylohyoid and
digastric muscles, and the skin of
the chin

63. 4. Mylohyoid Artery:
 Facial artery gives off some perforating
branches to the overlying platysma and
mylohyoid branch to the underlying
mylohyoid muscle during its course
 Terminal branches continue toward the
midline, crossing the anterior belly of the
digastric muscle superficially or deep, and
end at the mental region in general
 The mylohyoid artery tends to course
the lingual cortex at the bicuspid region
and finally anastomoses with the incisive
canal at the cuspid position
Fig.: anteroposterior
course of mylohyoid
artery
Fig.:
anastomoses
of mylohyoid
artery with
incisive canal

64. REFERRENCES
 SICHER & DuBRUL’s ORAL ANATOMY
 Gray’s Anatomy
 Atlas of Operative Maxillofacial Trauma Surgery by Springer
 Oral & Maxillofacial Surgery by Fonseca
 Robert J. Miller, Warren C. Edwards, Jonathan H. Cohen; maxillofacial anatomy: the
mandibular symphysis; J of Oral Implantology 2011.37:745-753
 Textbook of Human Embryology by Inderbir Singh
 Human Osteology by Nafis Ahmad Faruqi
 El Ayoubi Ali, Laamarti Sara, El Ayoubi Said, Bjijou Younes, Bouchikhi Mohamed. Triangle
of Marginal Mandibular Branch (MMB): Anatomical Zone, Constant Reference of the
MMB in Cervical Surgical Position. International Annals of Medicine. 2017;1(5)

65. THANK YOU