presentation for Dental Students

1. MUSCLES
OF
MASTICATION

2.  Introduction
 Definition
 The chewing cycle
 Development
 Muscles of mastication
 Clinical considerations

4.  The process by which food is crushed and ground by
teeth
 The first step of digestion
 Increases the surface area of food to allow more
efficient breakdown by enzymes

5. Mastication is the repetitive sequence of jaw
opening and closing with a profile in the vertical plane
called CHEWING CYCLE.
THREE PHASES:
1. OPENING PHASE
the mouth is opened
and the mandible is depressed

6. 2. CLOSING PHASE
-the mandible is
raised towards the maxilla
3. OCCLUSAL OR
INTERCUSPAL PHASE
-the mandible is
stationary and the teeth from
both upper and lower arches
approximate

7. Four Primary Muscles Of Mastication are
Masseter
Temporalis
Lateral pterygoid
Medial pterygoid

8. They develop from the mesoderm of first
brachial arch (mandibular arch)

9. COMMON CHARACTERISITICS:
1. All are inserted to the mandible
2. All are innervated by the mandibular division of
the trigeminal nerve
3. All are concerned with biting and chewing
FUNCTIONS:
1. To move the mandible
2. To secure then stabilize the mandibular positions
3. To determine the direction of mandibular
movements

10. It is a flat quadrangular
muscle, partly tendinous,
partly fleshy.
It overlies the lateral
surface of the mandibular
ramus.
MASSETER MUSCLE

11. Superficial part
ORIGIN: anterior 2/3 of the
zygomatic arch and zygomatic
process of the maxilla
INSERTION: angle of the
mandible and posterior part of
ramus
Deep part
ORIGIN: medial aspect of
the zygomatic arch
INSERTION: central and
upper part of ramus as
high as the coronoid
process.
ACTION: elevate the jaw,
with the superficial fibers
causing protraction

12. Nerve supply:
 Massetric nerve,
branch of anterior division of mandibular
nerve.
Blood supply:
 Maxillary artery,
which is a branch of external carotid artery.

13. SUPERFICIAL
 Platysma
 Risorius
 Zygomaticus major
 Parotid gland
 Parotid duct
 Branches of facial nerve

14. DEEP SURFACE
Overlies the,
 Insertion of temporalis
and ramus of the
mandible.
 In front buccinator and
the buccal nerve.
 Massetric nerve and
artery.

15. ANTERIOR
Margin projects over the
buccinator
POSTERIOR
Margin is overlapped by
the parotid gland.

16. TEMPORALIS MUSCLE
It is a large, fan-
shaped muscle at the
sides of the head.

17. ACTION: anterior
fibers elevate the
mandible, while the
posterior fibers retract
the mandible
ORIGIN: the floor of
temporal fossa and temporal
fascia
COURSE: anterior fibers run
vertically downwards while
the posterior fibers are
almost horizontal in position
INSERTION: the apex and
deep surface of the coronoid
process and along the
anterior border of the ramus

18. BLOOD SUPPLY
 Deep temporal part of maxillary artery
NERVE SUPPLY
 deep temporal branches of the anterior
trunk of mandibular nerve.

19. SUPERFICIAL
 Skin
 Auricularis anterior
 Temporal fascia
 Superficial temporal vessels
 Auriculotemporal nerve
 Temporal branch of facial nerve
 Zygomatic arch
 masseter

20. DEEP SURFACE
 Temporal fossa
 Lateral pterygoid
 Superficial head of medial
pterygoid
 Small part of buccinator
 Maxillary artery
 Deep temporal nerves
 Buccal vessels and nerve
ANTERIOR BORDER is seperated
from the zygomatic bone by a
mass of fat.

21. LATERAL (or EXTERNAL)
PTERGOID MUSCLE
It is a thick and
triangular muscle with two
heads.
It is the muscle of
mastication that occupy
primarily a horizontal
position.

22. ORIGIN: Superior portion –
infratemporal surface and the
crest of the greater wing of
sphenoid. Inferior portion –
lateral surface of lateral
pterygoid plate
INSERTION: fibers are
directed laterally and
backwards into the pterygoid
fovea on the neck of the
mandible ,articular disc and
capsule of TMJ
ACTION: depress, protrude
and move the mandible from
side to side

23. NERVE SUPPLY
 Nerve to lateral pterigoid
branch anterior division
of trigiminal nerve
BLOOD SUPPLY
 Pterygoid branch of 2nd
part of maxillary artery

24. SUPERFICIAL
1. Masseter
2. Ramus of the
mandible
3. Tendon of the
temporalis
4. Maxillary artery

26. Deep
1. Mandibular nerve
2. Middle meningeal
artery
3. Sphenomandibular
ligament
4. Deep head of the
medial pterygoid

27. Upper border
1. Deep temporal nerves
2. Masseteric nerve
Lower border
1. Lingual nerve
2. Inferior alveolar nerve
3. Middle meningeal
artery

28. Structures passing through the gap
between the two heads
1. The maxillary artery
2. The buccal branch of the mandibular
nerve
The pterygoid plexus of veins surrounds
the lateral pterygoid

29. MEDIAL (or INTERNAL)
PTERYGOID MUSCLE
It is almost a
mirror-like image of the
masseter muscle.
It is rhomboidal
and runs practically in
the same direction on
the inner surface of the
mandible

30. ORIGIN: medial
surface of lateral
pterygoid plate, the
posterior surface of the
tubercle of palatine
bone and tuberosity of
maxilla
INSERTION: pterygoid
tuberosity
ACTION: elevates and protracts the mandible. It
also moves the jaw from side to side by
contracting alternately with lateral pterygoid.

32. NERVE SUPPLY
 Nerve To The Medial Pterygoid
BLOOD SUPPLY
 Pterygoid branch of 2nd part of maxillary artery

33. SUPERFICIAL RELATIONS
 Upper part is separated from lateral pterygoid
1. Lateral pterygoid plate
2. Lingual nerve
3. Inferior alveolar nerve
 Lower part of the muscle is separated from the
ramus by
1. Same nerves
2. Maxillary artery
3. Sphenomandibular ligament

34. DEEP RELATIONS
1. Tensor palati
2. Superior constrictor of pharynx
3. Styloglossus
4. stylopharyngeus

35. The suprahyoid group of muscles being used
as secondary or supplementary muscles they
are
1. Digastric
2. Mylohyoid
3. Geniohyoid

36.  Two bellies united by tendon
 Origin – Anterior belly from
diagastric fossa of mandible.
Posterior belly from mastoid
notch of temporal bone.
 Insertion –Both meet at the
intermediate tendon and held by
the fibrous pulley.

37.  The muscle has secondary role in mastication as
a depressor muscle adding to the action of lateral
pterygoid muscle when mouth is to be opened
against resistance. Elevation of hyoid bone

38.  Flat triangular
 Origin –Mylohyoid line of mandible.
 Insertion – Middle and Anterior fibers into median
raphae. Posterior fibers body of hyoid
bone.
 The secondary role of this muscle is evident as a
depressor seen in action when mouth is to be opened
against resistance.
 It elevates the floor of mouth to help in deglutition.

39.  Short and narrow musle lies above mylohyoid
 Origin –Inferior mental spine
 Insertion – Anterior surface of body of hyoid bone.
 Geniohyoid elevates the hyoid bone and draws it
forward, thus acting as a partial antagonist to stylohyoid.
 When the hyoid bone is fixed, it depresses the mandible

41.  Depression-lateral
pterygoid.digastric,
geniohyoid and
mylohyoid
 Elevation-masseter,
temporalis, and the
medial pterygoid
 Protrusion –lateral
and medial pterygoid
 Retraction –
temporalis
 Side to side
movements- medial
and lateral pterygoid
acting alternately

42. CLINICAL
CONSIDERATIONS

43.  Caused by exotoxins of gram positive bacillus Clostridium tetani.
 Disease of the nervous system characterized by intense activity of
motor neuron and resulting in severe muscle spasm
CLINICAL FEATURES
 Pain and stiffness in the jaws and neck muscles ,with muscle
rigidity producing trismus and dysphagia
 Risus sardonicus
 Opisthotonous

44.  All patients should receive antimicrobial drugs
 Active and passive immunization.
 Surgical wound care
 Anticonvulsant if indicated

45. Bruxism : Jaw clenching, with or without forcible excursive
movements, where the intensity of the clenching dictates the
severity (or lack of) grinding .
Clenching- It can occur as a brief rhythmic strong contractions
of the jaw muscles during eccentric lateral jaw movements,
or in maximum intercuspation,
Causes
1) Associated with stressful events
2)Non stress related or hereditary

46.  Bruxism may lead to
-tooth wear
-fracture of the teeth or restoration
-uncosmetic muscle hypertrophy
 Treatment
-coronoplasty
-maxillary stabalization appliance

47.  Pain
 Muscle tenderness
 Clicking in the joint
 Limitation in the mouth opening
TREATMENT
 Reassurane
 Physiotherapy and Myotherapeutic exercises
 TENS (Transcutaneous Electronic Nerve Stimulation)
 Muscle relaxants
 surgery

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