a brief description of the anatomy of the mandible, its muscular attachments and its importance in implant placement

1. ANATOMY OF MANDIBLE
AND ITS IMPORTANCE IN IMPLANT TREATMENT
SHASHI KIRAN S
20/06/18

2. INTRODUCTION
• The mandible- largest and strongest bone of the face.
• Horseshoe shaped body which lodges the teeth
• Pair of Rami

3. BODY OF THE MANDIBLE
• Outer and inner surfaces and upper and lower borders
 Outer surface
• Symphysis menti
• Mental protuberance
• Mental foramen
• Oblique line
• Incisive fossa

4.  Inner surface
• Mylohyoid line
• Sub-mandibular fossa
• Sub-lingual fossa
• Superior and inferior genial tubercles
• Mylohyoid groove
• Upper border- sockets
• Lower border- base, digastric fossa

5. RAMUS
• Quadrilateral in shape
• Lateral and medial surfaces
• Anterior, posterior, upper and lower borders
• Coronoid and condylar processes

6. • Lateral surface- relatively featureless, bears the oblique
ridge in lower half
• Medial surface- Mandibular foramen, mandibular canal
• Lingula
• Mylohyoid groove
• Upper border- thin, mandibular notch
• Lower border- base, continuous with posterior border at
the angle
• Coronoid process
• Condylar process- fibrocartilage- TMJ, neck, pterygoid
fovea

7. ATTACHMENTS AND RELATIONS
• Buccinator, depressor labii inferioris, depressor anguli oris
• Incisive fossa-Mentalis, mentalis slips of orbicularis oris
• Deep cervical fascia
• Platysma
• Masseter
• Parotid gland

8. • Mylohyoid muscle
• Superior constrictor
• Pterygomandibular raphe
• Genioglossus, geniohyoid
• Anterior belly of digastric
• Sphenomandibular ligament
• Medial pterygoid
• Temporalis
• Lateral pterygoid
• Latreal part of the neck- Lateral ligament of temporomandibular joint

9. FORAMINA, NERVES AND VESSELS
• Mental foramen- mental nerves and vessels
• Mandibular foramen and canal- IAN and vessels
• Mylohyoid groove- mylohyoid nerve and vessels
• Lingual nerve
• Maxillary artery
• Mandibular notch- masseteric nerves and vessels
• Auriculotemporal nerve and superficial temporal artery- neck
• Facial artery
• Accessory foramina

10. ALVEOLAR PROCESS
• That portion of maxilla and mandible that forms
and supports the tooth socket.
• Parts-
• 1. external plate of cortical bone
• 2. alveolar bone proper (lamina dura) –
cribriform plate
• 3. cancellous trabeculae

11. OSSIFICATION
• Mandible is the second bone next to clavicle to ossify in the body. Its greater part ossifies in
membrane.
• The parts ossifying in cartilage- incisive part below the incisors, coronoid and condylar
process, and upper half of the ramus above the level of mandibular foramen
• Each half of the mandible ossifies from only one centre which appears at about the 6th week
of intrauterine life in the mesenchymal sheath of meckels cartilage near the future mental
foramen
• At birth mandible consists of 2 halves connected at the symphysis menti by fibrous tissue.
Bony union takes place during the first year of life.

12. AGE CHANGES IN MANDIBLE
 Infants and children-
• 2 halves fuse during the first year of life
• At birth the mental foramen opens below the sockets for the two deciduous molar teeth near
the lower border.
• Mandibular canal runs near the lower border. The foramen and canal gradually shifts
upwards
• Angle- obtuse 140 degrees or more
• The coronoid process is large and projects upward above the level of the condyle.

13.  In adults
• The mental foramen opens midway between the upper and
lower borders
• Mandibular canal runs parallel to the mylohyoid line
• Angle- 110-120 degrees
 In old age
• Height of the bone is markedly reduced
• Mental foramen and the mandibular canal are close to the
alveolar border
• Angle- obtuse 140 degrees

14. MYLOHYOID MUSCLE
• Severely resorbed ridge- origin of mylohyoid muscle approximates the crest
of the ridge, especially in the posterior mandible. In these cases, surgical
manipulation of the crest may injure the muscle.
• A mandibular periosteal reflection for sub periosteal implant often reflects
this muscle to the second molar region. The sub structure of the implant
then has a permucosal site in the 1st molar region and a lingual primary strut
above and below the muscle.
• Surgical manipulation of the tissue of the floor of the mouth- edematous
swelling of the sub lingual and the sub mandibular space, echymossis can
occur sub-cutaneously or sub-mucosally.
• In some cases- cellulitis or abcess sub-lingually or sub-mandibularly

15. GENIOGLOSSUS
• Origin- superior genial tubercle
• Main protruder of the tongue, branch of hypoglossal nerve
• During elevation of lingual mucosa and before impression making for a
sub periosteal implant, one should be aware of the origin to avoid
causing injury.
• A portion of the muscle can be reflected from the tubercle but should
not be completely detached from the tubercle because it may result in
retrusion of the tongue and possible airway obstruction.

16. MEDIAL PTERYGOID
• Medial pterygoid bounds the pterygo mandibular space
medially. This space is entered when an IANB is admistered
• Infection of this space is dangerous because of its proximity
to parapharyngeal space and the potential spread of
infection to mediastinum.
• Mandibular nerve

17. TEMPORALIS
• Origin from temporal fossa and inserts into the coronoid process
and anterior border of the ramus
• Retromolar triangle- surgical exposure of mandibular ramus
medially would involve this triangle which may lead to transaction
and post op pain.
• Incisions placed on the anterior ascending ramus should be
placed below the insertion of the two tendons of the muscle.
• Retractor and elevator, mandibular nerve

18. MENTALIS
• Origin- mental tubercles, insertion- skin of the chin
• Complete reflection of the mentalis muscle for the purpose of extension of a sub periosteal
implant may result in witch’s chin due to failure of muscle re attachment.
• If the muscle is completely detached to expose the symphysis, then an elastic bandage is
applied externally to the chin for 4 days to help in re attachment.
• Facial nerve

19. MASSETER
• This muscle can easily be deflected during surgery to expose bone
for ramus extension needed for lateral support for a sub periosteal
implant.
• The space between the masseteric fascia and the muscle is a
potential surgical space known as the masseteric space into which
infection may spread causing myositis and trismus.
• Mandibular nerve

20. INFERIOR ALVEOLAR NERVE
• In an excessively resorbed ridge, mental foramen
with its contents can be found on the crest of the
ridge. While making incisions or reflection of mucosa
in this region, care should be taken to avoid injury to
these vital structures.
• Knowledge of the position of the mandibular canal in
vertical and buccolingual dimensions is of paramount
importance during site prep for implants

21. LINGUAL NERVE
• Because this nerve lies just medial to the retromolar pad, incisions in this
region should remain lateral to the pad.
• And the mucosal reflection should be done with the periosteal elevator in
constant contact with bone to prevent injury to the nerve.
• Improper reflection of a lingual mucoperiosteal flap may injure the lingual
nerve and produce ipsilateral paraesthesia or anaesthesia, loss of taste, and
reduction of salivary secretion.

22. LONG BUCCAL NERVE
• The nerve courses between the 2 heads of lateral pterygoid and precedes medial to the medial
tendon of the temporalis to gain access to the buccinator.
• The nerve supplies the skin of the cheek and runs down to the level of the external oblique ridge,
penetrates the buccinators and spread its branches under the cheek mucosa alveolar mucosa and
attached gingiva opp molar teeth
• An implantologist planning to access the ramus for the purpose of excising block graft should be
aware of the buccal nerve and avoid injuring it.
• In addition, surgical manipulation in this area (insertion of sub periosteal implant) may injure this
nerve

23. BLOOD SUPPLY OF THE MANDIBLE
• Major artery- inferior alveolar artery
• Incisive branch is often severed during the harvest of a mono cortical symphyseal block of
bone for grafting resorbed ridges
Changes with age
• Reversal of flow
• Atherosclerotic changes- tortuous and narrow
• Arteries that supply blood after the interruption – mental artery, mandibular branch of sub
lingual artery, facial artery
• These anastomoses are critical in procedures with mucoperiosteal flaps.

24. CONCLUSION
• The surgical anatomy of the maxilla and mandible provide the foundation required to safely
insert dental implants.
• The anatomy is also a requisite to the understanding of complications that may inadvertently
occur during surgery such as injury to blood vessels and nerves
• This information also provides the operator the confidence needed to deal with these
complications.

25. REFERENCES
• Bd Chaurasia’s Human Anatomy 2nd edition
• Carranza’s clinical periodontology 10th edition
• Contemporary implant dentistry, Carl E Misch, 3rd edition