2. INTRODUCTION
The word mandible derived from Latin word mandibula-
"jawbone" or inferior maxillary bone.
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 structural 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
4. embryology
Mandible is the second bone after clavicle to
ossify in the body.
Parts that ossify in cartilage includes: incisive
part below the incisor teeth, coronoid and
condyloid processes
Upper half of ramus above the level of the
mandibular foramen
A single ossification centre for each half of the
mandible arises in the 6th week of I.U. life in
the region of bifurcation of inferior alveolar
nerve into mental and incisive branches. As the
ossification continues, the meckel’s cartilage
become surrounded and invaded by bone.
5. 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
6. OSTEOLOGY
BODY OF THE MANDIBLE
Horseshoe-shaped BODY
Has two surfaces EXTERNAL and INTERNAL surfaces ,
Two borders UPPER and LOWER borders
7. FEATURES SEEN ON OUTER SURFACE OF THE BODY
Symphysis Menti
Mental Protuberance
Mental Tubercles
Mental foramen
External Oblique line
Incisive fossa
8. FEATURES ON THE INNER SURFACE OF THE BODY
Genial tubercles
Mylohyoid line
Submandibular fossae
Sublingual fossae
Mylohyoid groove
Upper alveolar border
Lower border base
Digastric fossae
10. 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.
11. INFERIOR BORDER (base of mandible)
Is rounded, longer than the superior,
and thicker in front than behind.
12. RAMUS OF MANDIBLE
Is quadrilateral
2 surfaces
Lateral
Medial
4 borders
Superior
Inferior
Anterior
Posterior
2 processes
Coronoid
Condylar
13. PROCESSES
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
14. 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
16. ON THE LATERAL
SURFACE:
1. From The Oblique line :
Buccinator, and depressor anguli
oris below the mental foramen
2. Incisive fossa:
gives origin to MENTALIS mental
slips of ORBICULARIS ORIS.
3. Whole of lateral surface of
ramus except posterosuperior part
provides insertion to MASSETER.
4.Posterosuperior part : covered
by PAROTID GLAND
17. 5. Lateral surface of the neck
provides insertion to the
LATERAL LIGAMENT OF
TMJ.
6. Parts of both the inner and
outer surfaces just below the
alveolar margins are covered by
mucous membrane of the
mouth.
7. PLATYSMA is inserted into
the lower border.
8. The deep cervical fascia (
investing layer) is attached to
the whole length of the lower
border.
18. 1. Digastric fossa: arises
ANTERIOR BELLY OF
DIGASTRIC
2. Genial tubercles: arises
GENIOGLOSSUS and
GENIOHYOID.
3. Mylohyoid line : arises
MYLOHYOID MUSCLE.
4. From an area above the
posterior end of mylohyoid line:
arises SUPERIOR
CONSTRICTOR OF PHARYNX.
5. Pterygomandibular raphe:
Attached immediately behind the
third molar tooth in continuation
with the origin of superior
constrictor
ON THE MEDIAL SURFACE
19. 7.Below and behind the mylohyoid
groove: insertion of MEDIAL
PTERYGOID muscle .
8.At the apex of coronoid process :
TEMPORALIS is inserted ;extend
downwards on ant. Border of ramus.
9.Into the pterygoid fovea: insertion
of LATERAL PTERYGOID.
10.Sphenomandibular ligament : is
attached to the lingula.
20. BLOOD SUPPLY OF THE MANDIBLE
ARTERIAL SUPPLY
Mainly by Maxillary artery,
Branch of external carotid
artery
By its branches, mainly
through inferior alveolar
artery
21. Venous supply of mandible
Drains into
Internal jugular vein and external
jugular vein through maxillary vein,
facial vein and pterygoid plexus
22. Nerve supply of mandible
Mainly through the trigeminal nerve -
V cranial nerve
MANDIBULAR NERVE
Main trunk
Anterior trunk
Posterior trunk
23. FORAMINA AND OTHER RELATIONS
Mental foramina - mental nerve and
vessels
Mandibular notch - massetric nerve
and vessels
Medial side of neck - auriculo
temporal nerve
Mylohyoid groove - mylohyoid nerve
and vessels
Mylohyoid groove in front of ramus -
lingual nerve
Mandibular canal and foramina -
inferior alveolar nerve and vessels
25. 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.
Postnatal Growth Of Mandible
26. The mandible can be divided into several sub-units like
Chin
Alveolar process
Body
Lingual tuberosity
Ramus
Angular process
Coronoid process
Condylar process
27. 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.
29. Body: (corpus)
The length of the body increases as the ramus
moves posteriorly
30. Lingual tuberosity:
It forms the boundary between
the ramus & body
A combination of the resorption
and deposition accentuates its
prominence.
31. Ramus:
The ramus is seen to move posteriorly due to
deposition at its posterior border and resorption on
its anterior border
32. Angle:
The combined deposition and resorption causes flaring
of the angle of the mandible
33. Coronoid process :
Enlow’s enlarging “V” principle.
Birth: Coronoid process is at
higher level than condylar
process.
Childhood: Coronoid & condylar
processes are at same level.
Adult: Condylar process is at
higher level.
34. 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
35.
36. APPLIED ANATOMY OF MANDIBLE
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 and mental
foramen
The body of the mandible is considerably thicker than the
ramus and the junction between these two portions
constitutes a line of structural weakness.
Strength of the lower jaw varies with the presence or absence
of teeth. The presence of impacted lower third molars or
excessive long roots of canines make the area more
vulnerable for fracture.
38. Mandibular Foramen
The location of the mandibular foramen may vary based on race and
ethnicity
Among adult cadaveric mandibles, the foramen was found inferior to the
occlusal plane, at its level, or above it 75%, 22.5%, and 2.5% of the time,
respectively
Therefore, according to these investigations, 2.5% to 23.5% of block
injections given at the level of occlusion would be ineffective.
Advisable to inject patients 6 to10mmsuperior to the occlusal plane, which
usually accounts for anatomic variations
Short needles can be used to attain anesthesia in the mandible
39. Inferior Alveolar Canal
The inferior alveolar canal houses the IAN nerve , artery, vein and
lymphatics
The canal is; 3.4mm wide, and the nerve is ;2.2mm thick
Therefore, during implant placement it is possible to in advertently
penetrate into the mandibular canal and induce neurologic damage
without provoking hemorrhaging and vice versa.
When developing an osteotomy over the mandibular canal, cortical
bone is penetrated first, and the preparation terminates within softer
cancellous bone
The IAN may present in different anatomic configurations
40. The IAN may present in different anatomic configurations
The variation in the course of IAN is frequent
Liu et al OPG classification of course of nerve
41.
42. Mental Foramen and Nerve
Commonly, three nerve branches of the mental nerve emerge from the
mental foramen (each ;1 mm in diameter).
Location- Differs in horizontal and vertical plane
Atypically near canine or molar.
43. The anterior loop of the mental foramen refers to the IAN when it
courses inferiorly and anteriorly to the foramen and then loops back to
emerge from the foramen
The dimensions of anterior loops in panoramic radiographs varied
from 0.5 to 3 mm, and cadaver specimens manifested anterior
loops that ranged from 0.11to3.31mm
Choose an implant length a safety margin of 2mm
It is prudent to place the distal aspect of the implant 6 mm anterior
to the mental foramen to avoid damaging the loop when drilling the
osteotomy
44.
45. Mandibular Incisive Canal
Numerous investigations reported that there is ‘‘true’’ incisive canal
mesial to the mental foramen, which is a continuation of the mandibular
canal.
The incisive canal is typically found in the middle third of the mandible
(in 86%of cases).It usually narrows as it approaches the midline and
only reaches the midline 18%of the time
Terminates apical to lateral or central incisor
OPG -15% CT-93%
Only large sized canal posed problems
46. Lingual Foramen and Lateral Canals
The lingual foramen was detected in 99% of the mandibles when
evaluating skull dissections, but only 45% in radiographs
The lingual foramen harbors an artery that corresponds to an
anastomosis of the right and left sublingual arteries.
Risk of haemorrhage if canal size > 1mm
Submental and Sublingual Arteries
The submental artery (2-mm average diameter) is derived from the
facial artery, and the sublingual artery (2-mm average diameter) is a
branch of the lingual artery
If resected can cause haematoma in submandibular and sublingual
space, leading to swelling and airway obstruction
47. Submandibular and Sublingual Fossae
The submandibular and sublingual Fossae must be palpated prior to
osteotomy development; if there is a large undercut, the lingual
bony plate can be perforated in advertently, resulting in
hemorrhaging.
If there is a large undercut, an instrument Can be placed into and
parallel to the undercut to visualize and measure the extent of the
depression
A CT scan with radiopaque markers provides the most accurate
information.
48. The Lingual and Mylohyoid Nerves
The lingual nerve is usually located 3 mm apical to the osseous crest and
2 mm horizontally from the lingual cortical plate in the flap.
It is recommended that lingual, vertical releasing incisions be avoided.
Furthermore, incisions distal to the second molar should be made on the
buccal aspect of the ridge to provide additional room for safety.
Mylohyoid nerve- may contribute to incomplete anesthesia of mandibular
nerve
49. Mandibular zone of safety
Given by Carl E Misch
Determined radiograpically or clinically during surgery
50. CONCLUSION
Familiarity with the anatomic structures pertaining to dental
implantology is critically important.
Preplanning and review of anatomy before surgical procedures can
help to avoid problems.
Also many of the shortcomings of two-dimensional radiography for
treatment planning can be eliminated with the use of three-
dimensional imaging.
And an understanding of basic surgical principle is necessary to
insure a successful implant.
51. REFERENCES:
B.D CHAURASIA’S HUMAN ANATOMY – 6TH EDITION
TEXTBOOK OF ANATOMY BY INDERBIR SINGH- 5TH EDITION •
GRAY’S ANATOMY – 2ND EDITION
Greenstein G1, Cavallaro J, Tarnow D. J Periodontol. 2008 Oct;79(10):1833-46
J Oral Maxillofac Res 2010 (Jan-Mar) | vol. 1 | No 1 | e2 | p.1 -5
Editor's Notes
by four small elevations called the superior and inferior tubercle
Lateral surface – flat with oblique ridges Medial surface -. MANDIBULAR FORAMEN (centre of ramus at the level of occlusal plane. It leadsmandibular
canal. ) LINGULA : Anterior margin of foramen marked by tongue shaped projection MYLOHYOID GROOVE , UPPER BORXER , LOWER BORDER
MAIN – meningeal and nerve to medial ptretgoid
Anterior- buccal, masseteric , deeep temporal and lateral ptyerygoid
Mainly sensory fibres
Occasionally, the mental nerve emerges from the buccal plateof bone and reenters thealveolarboneto provide innervation for the incisor teeth.
Surgical dissection furnished the best evidence for validating thepresence of the anteriorloop ofthe mental foramen
Thus, when there is concern with respect to the location of the mental nerve, it should be exposed to identify its position before implant insertion. First, determineontheradiographwherethementalforamenis located