DENTAL PPT

1. MUSCLES OF
MASTICATION
Dr ABHINAND K
MDC

2. INTRODUCTION
 Mastication or chewing is the first mechanical
process in the gastrointestinal tract by which the
food substances are cut into small particles and
crushed or ground into a soft bolus by using
teeth
 Muscles of mastication are paired in each side
and work together to produce the movement of
mandible.
 Masticatory muscles are developed from
mesoderm of first branchial arch.

3. MUSCLES OF MASTICATION
MAIN MUSCLES
Muscles attached to rami of
mandible
• Temporalis
• Medial pterygoid
• Lateral pterygoid
• Masseter

4. ACCESSORY MUSCLES
• mylohyoid
• Geniohyoid
• Stylohyoid
• digastric
Suprahyoid
• Sternothyroid
• Omohyoid
• Thyrohyoid
• sternohyoid
Infrahyoid
Buccinator

5. TEMPORALIS
 Fan shaped
 Fills the temporal fossa
 Anterior fibres – vertical
 Posterior fibres – almost horizontal
 Intermediate fibres – variable degree of
obliquity

6.  Origin :
 floor of temporal fossa up to inferior temporal line
 Under surface of temporal fascia
 Insertion :
fibers converge to form tendon passing down from temporal
fossa medial to anterior part of zygomatic arch and inserts
on:
 Tip, anterior and posterior borders and medial surface of
coronoid process of mandible
 Anterior border of ramus of mandible

7.  Relations:
 Superficial: skin ,temporal fascia,superfacial temporal
vessels,auriculotemporal nerve, temporal branches of
facial nerve,zygomatic arch and masseter muscle
 Posterior :contents of infratemporal fossa in lower part
 Anterior :the tendon is separated from zygomatic bone by
pad of fat
 Actions:
 elevate mandible to occlude teeth
 retract mandible after protrusion
 Nerve Supply:
Temporal branches from anterior division of mandibular nerve

8. MEDIAL PTERYGOID
 Thick quadrilateral muscle
 Small superficial head
 Large deep head

9.  Origin:
from two heads
 Superficial head: maxillary tuberosity on infra temporal
surface of maxilla,adjoining surface of pyramidal process of
palatine bone
 Deep head: medial surface of lateral pterygoid plate of
sphenoid bone
 Insertion :
fibers form a tendinous lamina
 medial surface of ramus of mandible posteroinferior to
mylohyoid groove
 inner aspect of angle of mandible

10.  Relations:
 Lateral: lateral pterygoid muscle,sphenomandibular ligament, maxillary
artery, inferior alveolar nerve and vessels, lingual nerve, part of parotid gland
 Medial: tensor veli palatini, styloglossus, stylopharyngeus and superior
constrictor muscles
 Actions:
 assist in elevation of mandible
 along with lateral pterygoid muscle it causes protrusion of
mandible
 Help in side to side movements of jaw and grinding of food
between teeth of same side
 Nerve Supply
nerve to medial pterygoid, branch of the main trunk of
mandibular nerve

11. LATERAL PTERYGOID
 Key muscle of infratemporal fossa
 Short ,conical and have upper and lower
heads

12.  Origin:
→ Upper head: lower part of infra temporal surface of the
great wing of sphenoid and adjoining infratemporal
crest
→ Lower head: larger and arises from lateral surface of
lateral pterygoid plate of sphenoid bone
 Relations:
→ Superficial: ramus of mandible,masseter,superficial
head of medial pterygoid and tendon of temporalis
muscles
→ Deep :deep head of medial pterygoid
muscle,sphenomandibular ligament,maxillary and
middle meningeal arteries,mandibular nerve
→ Superior :temporal and massetric branches of
mandibular nerve
→ Inferior :lingual and inferior alveolar nerves
→ Structures present between two heads: buccal nerve
and maxillary artery

13.  Insertion:
both heads converge to form single tendon to insert
on:
→ Pterygoid fovea in the anterior surface of neck of
mandible
→ Adjoining articular disc and capsule of TMJ
 Actions:
 Assists in depression of mandible to jaw
 Protrusion of mandible along with medial pterygoid
 Helps in side to side movements of the jaw and
grinding of food between teeth of same side
 Nerve Supply:
Branches from anterior division of mandibular nerve

14. MASSETER
 Quadrilateral shaped
 3 layers
1. Superficial
2. Deep
3. Intermediate

15.  Origin:
o lower border and inner surface of anterior two-third of
zygomatic arch
o adjoining posterior border of zygomatic bone
 Insertion:
 ramus of mandible
 Adjoining surface of Coronoid process of mandible

16.  Relations:
 Superficial: skin,platysma,parotid gland, branches of facial
nerve and transverse facial branches of superficial temporal
vessels
 Deep: ramus of mandible, temporalis muscle
 Anterior :buccal pad of fat,buccal branch of mandibular
nerve,buccinator muscle
 Posterior: it is overlapped by parotid gland
 Actions:
 Elevation of mandible to approximate the teeth
 Retraction of mandible
 Superficial fibres help in protrusion of mandible
 Nerve Supply:
Masseteric nerve ,branch of anterior division of mandibular nerve

17. NERVE SUPPLY
Trigeminal nerve
(V cranial nerve)
Mandibular
branch
Anterior trunk
Main trunk
(medial
pterygoid)

18. BLOOD SUPPLY
 Maxillary artery – larger terminal branch of
external carotid artery
 Divided into three parts by lateral pterygoid
muscle
 Second part (pterygoid part) supplies
muscles of mastication

20. CLINICAL CONDITIONS
1. TRISMUS
2. MYOFASCIAL PAIN
3. FIBROSIS OF MUSCLES
4. MUSCLE DYSFUNCTION
5. TEMPORAL TENDONITIS

21. TRISMUS
 Jaw lock
 Reduced opening of jaw
 Caused by spasm of muscles of mastication
 Interfere with eating,speech,oral hygiene and
facial appearance

22. MYOFASCIAL PAIN SYNDROME
 Pain in muscles of mastication caused by:
1. Infection
2. Abnormal muscle function
3. Hyperactivity

23. INFECTION OF MASSETER MUSCLE

24. FIBROSIS OF MUSCLES
 Limitations of mandibular movements
 May lead to severe problems involving TMJ
 Red, inflamed, weak fibrous muscles

25. REFERENCES
 ANAND’S TEXTBOOK OF HUMAN
ANATOMY
 BD CHAURASIA
 ATLAS OF HUMAN ANATOMY-FRANK
H.NETTER,MD
 INTERNET :WWW.WIKIPEDIA.COM