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1. Muscles of Mastication
INDIAN DENTAL ACADEMY
Leader in continuing Dental Education
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2. Introduction
The muscles of mastication are
involved in the masticatory and
non masticatory movements of
the mandible .
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4.  The masseterand temporalis are
superficially located, just deep to
the subcutaneous tissue, and can be
easily palpated.
 The medial and lateral pterygoid,
however, lie more deeply and are
placed in the infratemporal fossa.
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5. MASSETER
• Quadrilateral muscle
• Covers lateral surface of mandible
coronoid process of the mandible.
• Consists of 2 portions
Origin
Superficial portion(larger)
- Lowerborderof ant. 2/3 of Zygomatic
arch
- Thick tendinous aponeurosis from the
zygomatic process of the maxilla
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6. Deep portion(smaller)
- Posterior 1/3of the
lowerborder
- Whole of the medial
surface of the
zygomatic arch
Insertion
Superficial fibres
– fibers pass downward
and backward to
insert into angle and
lowerhalf of the
lateral surface of thewww.indiandentalacademy.co
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7. Deep fibres.
- Fibers pass
downward
and forward,
to be
insertedinto
the upper
half of the
ramus and
the lateral
surface of
the coronoid
process of
the
mandible.
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8. • The deep portion of the muscle is partly
concealed, in front, by the superficial portion
• Behind , it is covered by the parotid gland.
• The fibers of the two portions are continuous at
theirinsertion.
• A portion of the parotid gland, the parotid duct,
transverse facial artery and branches of the
facial nerve lie superficially to the muscle.
Nerve supply :
Mandibularnerve via masseteric nerve that
enters its deep surface.
Arterial supply:
Masseteric branch of the maxillary artery.www.indiandentalacademy.co
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9. Action :
- Themasseter
elevates the
mandibleduring
thecentric
occlusion.
- Moves the
mandibleto the
sidein lateral
excursions,
- Retrudes the
mandiblewhen
in protrusion.
(deep fibres) www.indiandentalacademy.co
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10. Function of Masseter
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11. TemporalisTemporalis
A fan-shaped muscle covered by a fascia
sheet.
The large fan-like portion attaches to the
side of the skull and the smallertapering
portion attaches to the coronoid process
of the mandible.
It is a powerful masticatory muscle that
can easily be seen and felt during
closure of the mandible.
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13. Origin :
- Floorof temporal fossa.
- deep surface of temporal fascia.
Insertion
fibers converge as they descend, and end in a
tendon, which passes deep to the zygomatic arch
and is inserted into the.
- Medial surface, apex, anteriorand posterior
borderof coronoid process.
- anteriorborderof the ramus of the mandible
nearly as farforward as the last molartooth.
superficial tendon - anteriorborderof coronoid.
process.
deep tendon - internal oblique line.www.indiandentalacademy.co
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15. Arterial supply :
anteriorand posteriordeep temporal arteries.
Nerve supply :
anteriorand posteriordeep temporal nerves from the
mandibulardivision of the trigeminal nerve (V)
Action :
- Elevation (bilateral)
- Retrusion (bilateral)
activated during end to end and centric occlusal biting
positions, and pulls the mandible back in retrusive.
- Ipsilateral excursion (unilateral)
- Resting tonus (bilateral)
maintains the rest position of the mandible when the
person is upright www.indiandentalacademy.co
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16.  Due to the fan-shaped arrangement of the fibers of
temporalis, the pull of the muscle is a continuous
arc from the essentially vertical pull of the anterior
fibers (which elevate the mandible) to the
posteriorportion which pulls almost horizontally
and thereby retracts the mandible.
 This is necessary in closing the mouth since in the
open position the head of the mandible has moved
anteriorly against the articulartubercle.
 Note that the posteriorfibers of temporalis are the
only retractors of the mandible.
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18. Temporal fascia
 Thick aponeurotic sheet
that roofsover temporal
fossaand coversthe
temporalismuscle.
 Superiorly attached to
superior temporal line
 Inferiorly attached to
upper border of
zygomatic arch
 Deep surfacegives
origin to afew fibresof
temporalis. www.indiandentalacademy.co
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19. Lateral pterygoid
 It is a short, thick muscle, somewhat
conical in form, which extends almost
horizontally between the infratemporal
fossa and the condyle of the mandible
and has two heads superiorand inferior.
 Only muscle of the fourmuscles of
mastication to occupy a horizontal
position.
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20. Origin : both heads
arise from sphenoid
bone.
• Upperhead (small) –
infratemporal surface
and
infratemporal crest of
greaterwing of sphe
noid bone
• Lowerhead - lateral
surface of lateral
pterygoid plate www.indiandentalacademy.co
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21. Insertion :
- Anteromedial
surface of articula
rcapsule
- Anteriorborderof
articulardisc
- Anteriorsurface of
mandibularneck
i.e. Pterygoid
fovea.
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22. Nerve supply
nerve to lateral pterygoid
Arterial supply
Pterygoid branch of the maxillary artery.
Action :
The purpose of the lateral pterygoids is to
work togetherto pull the mandible
forward ("advance" it), and to translate
the condyles (open the mouth).
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23. • Protrusion (bilateral)
Thelateral pterygoidsacting together aretheprime
protractersof themandible, moving it into a
protrusiveposition.
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24. • Depression (bilateral)
Contractions of both lateral pterygoids along
with the suprahyoid and infrahyoid muscles,
help depress oropen the mandible.
• Contralateral Excursion
(unilateral)
The lateral pterygoid can act singly to move
the mandible in lateral excursions.
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25. Medial Pterygoid
 Thick, quadrilateral muscle.
 This muscle mirrors the masseterin position
and action,togetherwith the masseterit
forms a "sling"around the ramus.
 It is rhomboidal in shape and located deep
to the ramus of the mandible and runs
almost in the same direction.
 Has small superficial head and large deep
head.
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26. Origin :
Superficial head
- Maxillary tuberosity
- Lateral surface of
pyramidal process
of palatine bone
Deep head
- Pterygoid fossa
- Medial surface of
lateral pterygoid pl
ate
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27.  Insertion :
fibers pass downward,
lateral and backward,
and are inserted, by a
strong tendinous
lamina, into
 the lowerand back
part of the medial
surface of the ramus
 angle of the
mandible, as high
as(inferiorto) the
mandibularforamen.www.indiandentalacademy.co
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28.  Arterial supply :
pterygoid branch of the maxillary
 Nerve supply :
nerve to medial pterygoid
 Action :
The medial pterygoid elevates and orientates the
mandible laterally during chewing in conjunction with
the masseter.
Elevation (bilateral)
The medial pterygoid acts with the masseterto
elevate.
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29. • Protrusion
(bilateral)
The insertion of the
muscle is posterior
to its origin so the
right and left
muscles aid in
protrusion.
• Contralateral
Excursion
(unilateral)
The insertion of this
muscle is also
lateral to its origin,
so the muscle fibers
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30. Sphenomandibularis
 Origin
- Sphenoid bone, behind
orbit
 Insertion
- temporal crest (internal
obliqueline) of the
mandible
 Most efficient asnon-
working sideelevator of
mandible
 Had previously been
thought to be"medial belly
of temporalis" www.indiandentalacademy.co
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31. Zygomandibularis
Origin:
Posterior region of theorbital part of the
zygomatic boneand thesphenoid bone
Insertion :
Anterior mandibular ramus
Function:
Believed to aid in elevating themandible
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32. Non masticatory muscles
 Depressorsof themandible
 Platysma
 Suprahyoid muscles
 Infrahyoid muscles
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33. Suprahyoid muscles
- This group of muscles is located superiorto
the hyoid bone and connects to this bone
and the skull.
- Includes the mylohyoid, geniohyoid,
stylohyoid and digastric muscles.
Infrahyoid muscles
- These muscles are often referred to as strap
muscles due to theirribbon-like appearance.
- They are located inferiorto the hyoid bone.
- These muscles anchorthe hyoid bone and
depress the hyoid and larynx during
swallowing and speaking.www.indiandentalacademy.co
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34. SUPRAHYOID MUSCLES
Muscle Origin Insertion Action
DIGASTRIC
ANTERIOR
digastric
fossa of
mandible
Intermediate
tendon at hyoid
depresses
the mandible
and raises the
hyoid bone,
steadies the
hyoid bone
during
swallowing
and speaking.
POSTERIOR
DIAGASTRIC
mastoid
notch of
temporal
bone.
Intermediate
tendon at hyoid
STYLOHYOID
Styloid
process
Hyoid elevates and
retracts the
hyoid bone,
elongating the
floorof thewww.indiandentalacademy.co
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35. GENIOHYOID
LOWER
GENIAL
TUBERCLE
HYOID
Raises hyoid
and larynx;
fixes hyoid.
MYLOHYOID
Mylohyoid
line of
mandible
Raphe and
body of
hyoid bone.
Elevates
the hyoid
bone, floor
of the mouth
and the
tongue
during
swallowing
and
speaking

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36. INFRAHYOID MUSCLES
Omohyoid
superior
borderof
scapula
inferior
borderof
hyoid
bone.
depresses,
retracts and
steadies the
hyoid during
swallowing
and speaking
STERNO-HYOID Manubrium
sterni
Body of
hyoid
steady the
hyoid during
movements of
the tongue,
larynx and
pharynx
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37.  STERNO –THYROID
Origin - Sternum
Insertion - Side of thyroid cartilage
Action - depresses the hyoid bone and
larynx afterit has been elevated by muscles
during swallowing and vocal movements.
 THYROHYOID
Origin - oblique line of thyroid cartilage.
Insertion - Cornu and body of hyoid
Action - responsible forpreventing food from
entering the larynx during swallowing (it
pulls the larynx and hyoid bone together)..
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38. Platysma
 Subcutaneous sheet of striated muscle, located
in the superficial fascia.
 Origin-fascia and skin overthe pectoralis
majorand deltoid muscles.
 Insertion - inferiorborderof the mandible and
skin of the lowerface
 Actions –
- tenses the skin of the neck.
-It draws the corners of the mouth inferiorly and
assists in depressing the mandible.
-one of the muscles of facial expression that we
use to express sadness, horror, or frightwww.indiandentalacademy.co
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39. Mandibular Division Of Trigeminal
Nerve (Cn-v).
 All the muscles of mastication are supplied
by branches of the mandibularportion of the
trigeminal.
 This nerve carries the motorroot of CN-V.
Afterpassing through the foramen ovale, its
short trunk branches immediately into
sensory and motornerves.
 The Sensory Nerves include:
-InferiorAlveolar
-Lingual,
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40. - Auriculotemporal
- Buccal
 The motornerves
include
- Anteriorand
posteriordeep
temporal
- Nerve to the
medial pterygoid
muscle
- Masseteric
- Nerve to the
lateral pterygoid
muscle
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41. Maxillary artery
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42. Pterygoid venous plexus
This large venous plexus lies partly between
the lateral pterygoid and temporalis muscles
and the two pterygoid muscles.www.indiandentalacademy.co
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43. Development
 The muscles of mastication arise from the
mesoderm of the mandibulararch. The
mandibulardivision of the trigeminal
nerve enters this premuscle mass before
it splits into the Temporal, Masseterand
Pterygoideus.
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44. Review of actions of the muscles
of mastication
 DEPRESSION OF MANDIBLE
Gliding and hinge movements. Lateral
pterygoid aided by Suprahyoid and
Platysma.
 ELEVATION OF MANDIBLE
Masseter, medial pterygoids and anterior
fibers of temporalis.
 PROTRUSION OF MANDIBLE:
Lateral and medial pterygoids on both sides.
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45. RETRUSION OF MANDIBLE:
Post (horiz.) fibers of temporalis.
LATERAL MOVEMENT:
Medial and lat pterygoids on one side only
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46. Clinical considerations
 The muscles of mastication are involved in the
masticatory movements of the mandible and
also the non masticatory .
 In complete denture prosthodontics the non
masticatory movements and contacting of
teeth during these movements are of more
concern.
 As a group they are very powerful.
 Only the MASSETERinfluences the contourof
the distobuccal cornerof the buccal flange.
 The magnitude of its force is felt in the molar
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47.  The denture should be contoured to accommodate the
contraction of the masseteras it force the buccinator
onto the retromolarpad,otherwise it will lead to
anteriordisplacement of the denture.
 The temporal muscle does not participate in biting
force when mandible is in protrusion and can be used
as a test to determine if patient is closing in centric
relation.
 The muscles that protrude the mandible and move it
side to side are strongerthan the retractors.
 The precise control and coordination existing
between the muscles enables them to apply powerful
force to piece of food and yet bring teeth into
occlusion without jarring,by the neuromuscular
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48.  Premature contact of the teeth causes discomfort
and damage to the underlying muscles and hence
dentures should not be fitted with increased
vertical dimension,and is a common cause of
denture failure.
 When vertical dimension is reduced,the muscles
lose theirpower,as they develop maximum
powerwithin a short range of vertical dimension.
 In protrusion when posteriorteeth are present
the forward pull of the muscle fibres of the
pterygoids are balanced but the gradual
relaxation of the posteriorfibres of the temporalis
and masseterand anteriorteeth and vice versa.www.indiandentalacademy.co
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49.  When posteriorteeth are lost,mastication is
performed on anteriorteeth,orlong period of
edentulism abnormal habits of chewing are
developed with loss of the delicate balance between
the groups of muscles and the protrusive muscles
become dominant,and leads to difficulty in recording
anteroposteriorocclusal relationship.
 When the masticatory muscles try to bring the teeth
into occlusion and there are interfering inclines within
the closing and opening paths of mandibular
movement, the muscles of mastication may become
furtherirritated resulting in muscle tenderness and
muscle pain. Muscles that are irritated can affect the
"quality" of mandibularmovement, function andwww.indiandentalacademy.co
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50.  The freeway space is the space between the
occlusal surfaces of the teeth when the
mandible is at rest and the muscles in a
state of minimum contraction.
 When recording jaw relations the centric
relation is recorded with aid of posterior
fibres of temporalis.
 The function of the muscles is not only the
mastication but also the mandibular
movements which is of importance to the
prosthodontist.
 The mandible attached to the TMJis
capable of various movements aided by thewww.indiandentalacademy.co
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51. -opening mvt
-closing mvt
-shearing mvt
-lateral and chewing mvts.
 Bruxism-the grinding of teeth for
nonfunctional purposes in response to an
increased tonus of the muscles of mastication.
It usually happens during sleep
 Clenching- forceful clamping of jaws in static
relationship
 Trismus –
Arthritis of the TMJcould affect the tone of the
lateral pterygoid muscle, the patient cannot
open the mouth. www.indiandentalacademy.co
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52. Summary
 Themasticatory system isextremely
complex,primarily madeof bonesmuscles
ligamentsand teeth.
 Precisemovement of themandibleby the
musculatureisrequired to movetheteeth
efficiently acrosseach other during function.
 Theknowledgeof theanatomy ,physiology and
mechanicsof thismovement arebasic to
understanding thismovement.
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53. references
 William’s :Grays anatomy
 Chaurasia :human anatomy vol3.head and neck ,2nd
edition 1992,varghese
 Grants;method of anatomy
 Zarb&Bolender:Boucher’s ;prosthodontic treatment or
edentulous patients,9th
edition,CBS
 Heartwell :syllabus of complete dentures,1992,4th
edition,Varghese
 Jeffery P.Okeson:Management of TMJdisorders and
occlusion,4th
edition,1998Mosby
 Ramfjord/Ash:Occlusion,3rd
edition,WBSaunders
 www.drjimboyd.com
 Federal services board review 2000 website
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54. Anatomy.uams.edu
www.med.mich.edu
Geocities.com/medinotes
Pubmed :Dunn GF,Anatomical observation
of a craniomandibularmuscle originating
from the skull base: the
sphenomandibularis.Cranio. 1996
Apr;14(2):97-103; discussion 104-5.
http://www.drjimboyd.com/book/spheno.ht
m.
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