This document discusses the muscles of mastication. It begins by introducing the muscles and their anatomy. The primary muscles of mastication are the masseter, temporalis, medial pterygoid, and lateral pterygoid muscles. It describes the origin, insertion, nerve supply, blood supply, and actions of each muscle. Additionally, it covers related topics like the embryology of the muscles, clinical considerations like trismus and bruxism, and the significance of the muscles in orthodontics.

1. MUSCLES OF MASTICATION
PRESENTED BY:-
DR. RAUNAK MANJEET
PG 1ST YEAR
DEPT OF ORTHO.
KDDC, MATHURA

2. CONTENTS
 INTRODUCTION
 ANATOMY OF MUSCLES
 EMBRYOLOGY/ DEVELOPMENT
 ACTIONS/ PHYSIOLOGY
 CLINICAL EVALUATION
 SIGNIFICANCE IN RELATION TO ORTHODONTICS
 EFFECT OF FUNCTIONAL APPLIANCES
 REFERENCES

3. INTRODUCTION
 Muscle refers to group of muscle fibers bound
by connective tissue.
 Muscles generates forces and movements useful in
regulation of internal environment.
 Teeth, jaws, muscles of the jaws, tongue and the
salivary glands aid in mastication.

4. MUSCLE
 An organ that by contraction produces
movements of a being; A tissue composed of
contractile cells or fibers that effect
movement of an organ or part of thebody.

6. • Units of skeletal muscle are the muscle fibers.
•Fibers are arranged in bundles of various sizes and
pattern called fasciculi.
• Connective tissue fills the spaces between muscle
fibres within a fasciculus where itis known as the
endomysium.
• Each fasciculus is also surrounded by a strong
connective tissue sheath or perimysium.
• Surrounding the whole muscle lies epimysium.

7. CLASSIFICATION OF MUSCLES
 Muscles of the body can be broadly classified based on structure,
contractile properties, control mechanisms into
a) Skeletal muscle
b) Smooth muscle
c) Cardiac muscle
Depending upon striations
a) Striated and
b) Non striated
Depending upon control
a) Voluntary and
b) Involuntary

9. MUSCLE PHYSIOLOGY
CONTRACTIONOFTHEMUSCLE
• In the mid 1950s JeanHauson and High Huxley had
arevolutionary insight into the mechanism of
musclecontraction.
• Previously scientists had imagined that muscle
contraction must be a folding process.
• Hauson and Huxley proposed, however that skeletal
muscle shortens during contraction because the thick
and thin filaments slide past one another.
• Their model is known asSliding filament
mechanism of muscle contractions

11. SLIDING FILAMENT MECHANISM
•During musclecontraction, myosin headspulls in
the thin filaments, causing them to slide .
•Themyosin crossbridges may even pull the thin
filaments of each Sarcomereso far inward that
their ends overlap in the centre of the Sarcomere.
•Asthe thin filament slide inward, the Zdiscscome
toward each other, and the Sarcomereshortens but
the lengths of thick andthin filaments do not change.
• The sliding of the filaments and shortening of
the Sarcomeres cause shortening of the whole
muscle fiber and ultimately the entire muscle.

12. MASTICATION
It is the first step of digestion, and it
increases the surface area of foods to
allow a more efficient break down by
enzymes. During the mastication process,
the food is positioned by the cheek and
tongue between the teeth for grinding.
Chewing or mastication is a process by
which food is crushed and grinded by
teeth.

14. EMBRYOLOGY/ DEVELOPMENT
• Themuscular systemdevelops from intra embryonic
mesoderm.
• Muscle tissuesdevelop from embryonic cellscalled
myoblast.
• Muscular component of Branchial arch form
manystriated musclesin the head and neck
region.

15.  Muscles of mastication are
derived from first or
MANDIBULAR ARCH.
 Develop from mesoderm
of the first brachial arch
and are supplied by a
branch of the trigeminal
nerve (CN V), the
mandibular nerve.
 But the posterior belly
of digastric muscle
develops from second
brachial arch and supplied
by the facial nerve.

18. MUSCLES OF MASTICATION
PRIMARY
TEMPORALIS
MASSETER
MEDIAL PTERYGOID
LATERALPTERYGOID
ACCESSORY
INFRAHYOID
STRENOHYOID
THYROHYOID
OMOHYOID
SUPRAHYOID
DIGASTRIC
STYLOHYOID
MYLOHYOID
GENIOHYOID

19. MUSCLES OF MASTICATION

20. • They are functionally classified as:
 Jawelevator
1. Masseter
2. Medialpterigoid
3. Temporalis
 Jawdepresser
1. Lateralpterigoid
2. AnteriorDigastric
3. Geniohyoid
4. mylohyoid

21. PRIMARY MUSCLES

22. MASSETER
Quadrilateral ,thick covers
lateral surface of ramus of
mandible & it consists of
three layers :
Superficial Layer
Middle Layer
Deep Layer

24. Superficial Layer
 It is largest layer.
 Origin : It arises from the anterior 2/3rd
of the inferior border of zygomatic arch &
zygomatic process of maxilla.
 Insertion: fibers of superficial layer pass downwards &
backwards to insert into angle & lateral surface of
the mandibular ramus.

25. Middle Layer
 Origin : It arises from the medial aspect of the
anterior two thirds & from the lower border of the
posterior third of the zygomatic arch.
 Insertion : fibers of middle layer inserts into the
central
part of the mandibular ramus.

26. Deep Layer
 Origin : It arises from deep surface of the zygomatic
arch.
 Insertion : Fibers of the deep layer inserts into the
upper part of the mandibular ramus & into it’s
coronoid process.

28. NERVE SUPPLY
 Massetric branch of
mandibular
nerve supplies to the
masseter
muscle.

29. BLOOD SUPPLY
 Maxillary artery , which is a
branch of
external carotid artery.

30. ACTION OF MASSETER
 Elevates the mandible to close the mouth to bite .
 Brings molars together for crushing & grinding
“ Chewer muscle” .
 Superficial muscles can cause protusion .
 Small effect in side to side movement , retraction &
minimal activity in resting position.

31. Palpation
 The patient is asked to clench their teeth & using
both hands , the practitioner palpates the masseter
muscle on both the sides extraorally, making sure
that the patient continues to clench during the
procedure.
 Palpate the origin of the masseter
bilaterally along the zygomatic arch &
continue to palpate down the body of
mandible where the masseter is attached.

33. TEMPORALIS
 Largest of all muscles of
mastication.
 Fan shaped muscle.
 Fills the temporal fossa.

34. ORIGIN
 Temporal fossa, excluding zygomatic bone.
 Temporal fascia :
thick, aponeurotic sheet that roofs over the temporal fossa &
covers the temporalis muscle.
Superiorly, the fascia is single layered & is attached to
superior temporal line.
Inferiorly, it splits into two layers, which are attached to
inner & outer surfaces of upper border of zygomatic arch.
small gap between two layers contains superficial temporal
artery & zygomatico temporal nerve .

35.  Deep Surface gives origin to some
fibers of temporalis muscles.
Fibres
1 Superiorly runs
vertically
2 Middle runs
obliquely
3 Posteriorly runs
horizontally
All pass through gap deep to
zygomatic arch.
1
2 2 1
3

36. INSERTION
• deep surface of coronoid.
 Anterior border of ramus of
mandible.

38. NERVE SUPPLY
 Anterior & posterior
deep temporal branches
from the anterior
division of mandibular
nerve.

39. BLOOD SUPPLY
 The muscle receives its
blood supply from
the deep temporal
arteries which
anastomose with
the middle temporal
arteries.

40. ACTIONS OF TEMPORALIS
 Elevates the mandible .
 Side to side gliding movements.
 Retraction of protruded mandible.

41. Patient is asked to protude the teeth
a.The upper region-above the zygomatic arch and anterior to the
TMJ .
b.the middle region- above TMJ and superior to zygomatic
arch.
c,.The lower region-above and behind the ear
palpation
a b C

43. MEDIAL PTERYGOID
 It is also called pterygoidus
internus or internal pterygoid
muscle.
 It is a quadrilateral muscle.
 It has a small superficial head,
large deep head.

44.  It arisesfromlateral pterygoid plate (deep head),
and from the maxillary tuberosity(superficial
head).
 Insertion isseenon the Medial surface of angle
of the Mandible.
ORIGIN & INSERTION

46. • Runs downwards,backwards
and laterally.
FIBERS

47. NERVE SUPPLY
• Branch of the main
trunk of the
mandibular nerve i.e.
nerve to medial
pterygoid.

48. BLOOD SUPPLY
• Pterygoid branch of 2nd
part of maxillary artery.

49. FUNCTIONS
• Elevates themandible.
• Closes the jaw.
 Helps in sideto sidemovement.

50. Elevation PROTRUSION LATERAL EXCRUSION

51. Palpation of medial pterigoid

53. o gently palpate them on the medial aspect of the
jaw,simultaneously from both inside and outside the
mouth.

54. LATERALPTERYGOID

55. LATERAL PTERYGOID
Also known aspterygoideus
externus
or external pterygoid
muscle.
 Short, conical muscle.
 Has two heads :upper ,
lower
lower

56. • of greater wing of
Origin
A.Upper head – from infratemporal fossa and crest of
greater wing of sphenoid
• B.Lower head – lateral pterygoid plate
• INSERTION
• Fibers run backwards and laterally and converge for insertion
Into anterior side of condyle & pterygoid fovea.
a b

58. BLOOD SUPPLY
Pterygoid branch of 2nd part of
maxillary artery.

59. NERVE SUPPLY
Nerve to lateral pteygoid branch of
anterior division of trigeminal nerve.

60. ACTION OF LATERAL PTERYGOID
• Assists in opening the mouth with suprahyoid muscles.
• Right lateral pterygoid and right medial pterygoid
turnsthe chin to left side as a part of grinding movement.
• When the lateral & medial pterygoids of two sides act
together they protrude the mandible so that the lower
incisors project in front of the other.
• The upper (superior) head being involved in chewing.

61. The combinded efforts of the Digastrics and
Lateral Pterygoids provide for natural jaw opening

62. SIDE TO SIDE GRINDING MOVEMENT

63. Medial and lateral pterygoid act
together to protrude the
mandible

64. Palpation of Lateral pterygoid

65. SUPRAHYOID
MUSCLES

66. MYLOHYOID MUSCLE
• This muscle with the fellow of the opposite side and forms the floor
of the mouth.
Origin:
from the mylohyoid line on inner surface of mandible
Insertion:
• Posterior fibers run downwards and medially to insert into the front
of the body of hyoid just above its lowerborder.
• Rest of the fibers insert into amedian fibrous raphe stretching
between the symphysis menti and body of the hyoid.
Nerve supply: mylohyoid nerve

67. •Elevates hyoid bone, supports
and raises floor of mouth
which aids in
early stage of swallowing,
•depress the mandible.
ACTIONS
•Elevates hyoid bone, supports and raises
floor of mouth which aids in
early stage of swallowing,
•depress the mandible.

68. DIAGASTRIC MUSCLE
• The digastric muscle has an anterior and a posterior belly united in the middle
by a common tendon.
ANTERIOR BELLY-
Origin -from the digastric fossa in the lower border of the
mandible nearthe symphysis menti.
• Insertion –into the common tendon.
• Nerve supply –mylohyoid nerve
POSTERIORBELLY–
• Origin –from the mastoid notch of temporal bone.
Insertion –into the common tendon which lies just above the
hyoid
• Nerve supply –a branch from facial nerve.

69. • Elevates floor of the mouth and hyoid bone during
deglutition.
• Depresses the mandible
Actions

70. GENIOHYOID
Origin:
From inferior genial tubercle (in the midline of inner
Surface.
Insertion: is into the hyoid bone.
Action: depresses the mandible.
Blood supply: is through lingual artery.
Nerve supply: is by hypoglossal nerve

71. GENIOHYOID MUSCLE

72. • Origin-It arises from the
posterior and lateral surface of the
styloid process of the temporal bone.
It is inserted into the bone. body of the
hyoid
Action :draws the hyoid, bone upward
backward and elongates the floor of the
mouth
STYLOHYOID
stylohyoid

73. IMPORTANT FACTS ABOUT MASTICATION
• There are about 15 chews in a series from the time
of food entry until swallowing
• Average jaw opening during chewing is between
16-20mm
• Average lateral displacement on chewing is
between 3 and 5mm
• Men chew faster and have a shorter occlusal phase
than women, it also depends on the type of food.

74. • CLINICAL
CONSIDERATIONS

75. TETANUS(LOCK JAW)
• Caused by exotoxins of gram positive bacillusClostridium
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

76. • Avg interincisal opening -13.7mm(5 to 23mm)
• ETIOLOGY
1) Trauma to musclesor blood vessels in infratemporal fossa
associated with dental injections of localanesthetics.
2) Haemmorhage.
3) LAcontaminatedwith alcoholor coldsterilizing
solutions produceirritation ofmuscles.
4) Lowgradeinfectionafterinjection

77. TREATMENT
• All patients should receive antimicrobial drugs
• Active and passive immunization.
• Surgical wound care
• Anticonvulsant if indicated

79. BRUXISM
Bruxism : Jaw clenching, with or without forcible excursive
movements,
where the intensity of the clenching dictates the severity
(or lackof) grinding.
Causes
1) Associated with stressful
events 2)Non stress related or
hereditary

80. • Bruxism maylead to
-tooth wear
-fracture of the teeth or
restoratrion
-uncosmetic muscle hypertrophy
• Treatment
-coronoplasty
-maxillary stabalization appliance

83. MYOFACIAL PAIN DYSFUNCTION SYNDROME
• Pain
• Muscle tenderness
• Clicking in the joint
• Limitation in the mouth opening
TREATMENT
• Physiotherapy and Myotherapeutic
exercises
• Transcutaneous Electronic Nerve
Stimulation
• Muscle relaxants
• surgery

86. BUCCINATOR MECHANISM
It is a continuous thick muscle band that encircles the dentition & is
anchored at
the pharengeal tubercle.
Components-
Orbicularis oris
Buccintor
Pterygomandibular raphe
Superior constrictor of pharynx

89. SIGNIFICANCE IN RELATION TO ORTHODONTICS
•The facial muscles can affect jaw growth in two ways ;
The formation of bone at the point of
muscle attachments depends on the
activity of muscles.
The musculature is an important part of
the total soft tissue matrix whose growth
normally carries the jaw downwards &
forwards.

90. If loss of part of the musculature occurs in utero due to any
birth injury it results in underdevelopement of that part of
the face.
In the cerebral palsy ...... Decreased muscle tonocity which
leads to increase in ant. Facial height , distortion of facial
proportion & mandibular height, excessive eruption of post.
Teeth & open bite.

91. Effect of MYOFUNCTIONAL APPLIANCE.
• It improves tonocity of the oro- facial musculature.
• If there is disturbance in the equillibrium of the muscle forces , it may be
corrected by myofunctional appliances.
•Appliances like vestibular screens , lip bumper & frankel appliances can bring
the change by either applying or reliving the forces of the circum oral
musculature.
•Vestibular screen
•The vestibular screen can be usee either to apply the forces or to relive the force
from the teeth thereby allowing them to move due to forces exerted by tounge .
Can be used to perform muscle exercises to help in correction of hypotonic lip &
cheek muscle.

93. Lip bumper is a modified vestibular screen used for muscular force application or
elimination of force , mostly used in mandibular arch.

94. Frankel appliance
This appliance functions by increasing the transverse , sagital & vertical intra oral space
With the help of buccal shields & lip pads & the buccal pads . Helps in elimination of
the forces by peri oral musculature.

95. REFERENCES
• GRABER 3RD EDITION
• PROFITT CONTEMPORARY
ORTHODONTICS
• B.D.Chaurasias, Human anatomy
• Shafer,Hine,Textbook of oral pathology
• Human anatomy A K Dutta
• Grays Anatomy
• Journal Refernces

96. THANK YOU