Muscles of mastication / dental implant courses by Indian dental academy

MUSCLES OF
MASTICATION
INDIAN DENTAL ACADEMY
Leader in continuing Dental Education
www.indiandentalacademy.com

CONTENTSCONTENTS
 INTRODUCTIONINTRODUCTION
 DEVELOPMENT OF MUSCLES OF MASTICATIONDEVELOPMENT OF MUSCLES OF MASTICATION
 TYPES OF MUSCLESTYPES OF MUSCLES
 ANATOMY OF MUSCLESANATOMY OF MUSCLES
 GENERAL MECHANISM OF MUSCLE CONTRACTIONGENERAL MECHANISM OF MUSCLE CONTRACTION
 MUSCLES OF MASTICATIONMUSCLES OF MASTICATION
 PATHOLOGICAL CONDITIONS AFFECTING MUSCLESPATHOLOGICAL CONDITIONS AFFECTING MUSCLES
 PROSTHODONTIC CONSIDERATIONSPROSTHODONTIC CONSIDERATIONS
 CONCLUSIONCONCLUSION
 REFERENCESREFERENCES
www.indiandentalacademy.comwww.indiandentalacademy.com

INTRODUCTIONINTRODUCTION
““ MOTION IS THE CAUSE OF ALL LIFE”MOTION IS THE CAUSE OF ALL LIFE”
LEONARDO DA VINCILEONARDO DA VINCI

MuscleMuscle:: TTISSUE CHARACTERIZED BY AGGREGATION OF CELLSISSUE CHARACTERIZED BY AGGREGATION OF CELLS
WHOSE PRIMARY ROLE IS TO PRODUCE CONTRACTION,AND ALLOWINGWHOSE PRIMARY ROLE IS TO PRODUCE CONTRACTION,AND ALLOWING
MOVEMENTS OF PARTS AND ORGANS OF THE BODY.MOVEMENTS OF PARTS AND ORGANS OF THE BODY.
IT MAY ALSO BE DEFINED AS A BANDIT MAY ALSO BE DEFINED AS A BAND
OF CONTRACTILE FIBROUS TISSUE,WHICH PRODUCE MOVEMENTS IN ANOF CONTRACTILE FIBROUS TISSUE,WHICH PRODUCE MOVEMENTS IN AN
ANIMAL BODY.ANIMAL BODY.
MasticationMastication :: RHYTHMIC OPPOSITION AND SEPARATION OF JAWSRHYTHMIC OPPOSITION AND SEPARATION OF JAWS
WITH THE INVOLVEMENT OF TEETH ,LIPS CHEEKS AND TOUNGE FORWITH THE INVOLVEMENT OF TEETH ,LIPS CHEEKS AND TOUNGE FOR
CHEWING OF FOOD IN ORDER TO PREPARE IT FOR SWALLOWING ANDCHEWING OF FOOD IN ORDER TO PREPARE IT FOR SWALLOWING AND
DIGESTION.DIGESTION.
MAIN PURPOSE OF MASTICATION IS TOMAIN PURPOSE OF MASTICATION IS TO
REDUCE THE SIZE OF FOOD PARTICLES TO A SIZE THAT IS CONVINIENTREDUCE THE SIZE OF FOOD PARTICLES TO A SIZE THAT IS CONVINIENT
FOR SWALLOWING{BOLUS FORMATION} WITH THE HELP OF SALIVA.FOR SWALLOWING{BOLUS FORMATION} WITH THE HELP OF SALIVA.

DEVEOPMENT OF MUSCLESDEVEOPMENT OF MUSCLES OFOF
MASTICATIONMASTICATION
 The muscular system develops from intra embryonicThe muscular system develops from intra embryonic
mesodermmesoderm
 Muscle tissues develop from embryonic cells calledMuscle tissues develop from embryonic cells called
myoblast.myoblast.
 Muscular component ofMuscular component of BranchialBranchial archarch form manyform many
striated muscles in the head and neck region.striated muscles in the head and neck region.
 Muscles of mastication are derived from first orMuscles of mastication are derived from first or
MANDIBULAR ARCH.MANDIBULAR ARCH.

SKETCH OF 20 WEEK FETUS SHOWING MUSCLES
DERIVED FROM BRANCHIAL ARCHES

MUSCLES OF MASTICATIONMUSCLES OF MASTICATION
Mastication forcesMastication forces The aev maximumThe aev maximum
sustainable biting force is 756N{170 pounds}.sustainable biting force is 756N{170 pounds}.
Molar region:Molar region: Biting force range 400-890NBiting force range 400-890N
Premolar region:Premolar region: Biting force range 222-445NBiting force range 222-445N
Cuspid regionCuspid region:: Biting force range 133-334NBiting force range 133-334N
Incisor regionIncisor region:Biting force range 89-111N:Biting force range 89-111N
{20-55 pounds}{20-55 pounds}

PRIMARY MUSCLES OFPRIMARY MUSCLES OF
MASTICATIONMASTICATION
 MASSETERMASSETER
 TEMPORALISTEMPORALIS
 MEDIAL AND LATERAL PTERYGOIDMEDIAL AND LATERAL PTERYGOID
SECONDARY MUSCLES OF MASTICATIONSECONDARY MUSCLES OF MASTICATION
The suprahyoid group of muscles being used asThe suprahyoid group of muscles being used as
secondary or supplementary muscles they aresecondary or supplementary muscles they are
 DigastricDigastric
 MylohyoidMylohyoid
 GeniohyoidGeniohyoid

THE MASSETERTHE MASSETER
QQuadrilateral and and consist of three layers.uadrilateral and and consist of three layers.
ATTACHEMENTSATTACHEMENTS
Superficial LayerSuperficial Layer :: Arises by thick aponeurosis.Arises by thick aponeurosis.
From zygomatic process of maxilla and anterior 2/3From zygomatic process of maxilla and anterior 2/3
of lower border of zygomatic arch,pass downwardof lower border of zygomatic arch,pass downward
and back wards at an angle of 45degree and insertedand back wards at an angle of 45degree and inserted
into lower part of lateral surface of ramus ofinto lower part of lateral surface of ramus of
mandiblemandible

 MIDDLE LAYERMIDDLE LAYER: Arises from: Arises from
anterior 2/3 of the deep surfaceanterior 2/3 of the deep surface
and posterior 1/3 of the lowerand posterior 1/3 of the lower
border of the zygomaticborder of the zygomatic
arch,pass vertically downwardsarch,pass vertically downwards
and and inserted into middle partand and inserted into middle part
of ramus.of ramus.
 DEEP LAYER:DEEP LAYER: Arises from deepArises from deep
surface of the zygomatic arch,surface of the zygomatic arch,
pass vertically downwards andpass vertically downwards and
inserted into the upper part of theinserted into the upper part of the
ramus and into the coronoidramus and into the coronoid
process.process.

RELATIONS OF MASSETERRELATIONS OF MASSETER
SUPERFICIASUPERFICIA
 IntegumentIntegument
 PlatysmaPlatysma
 RisoriusRisorius
 Zygomaticus majorZygomaticus major
 Parotid glandParotid gland
 Parotid ductParotid duct
 Branches of facialBranches of facial
nervenerve

DEEP SURFACEDEEP SURFACE
Overlies the,Overlies the,
 Insertion ofInsertion of
temporalis and ramustemporalis and ramus
of the mandible.of the mandible.
 In front buccinatorIn front buccinator
and the buccal nerve.and the buccal nerve.
 Massetric nerve andMassetric nerve and
artery.artery.

ANTERIORANTERIOR MarginMargin
projects over theprojects over the
buccinator and is crossedbuccinator and is crossed
below by the facial vein.below by the facial vein.
POSTERIORPOSTERIOR MarginMargin
is overlapped by theis overlapped by the
parotid gland.parotid gland.

Nerve supplyNerve supply ::
 MASSETRICMASSETRIC
NERVE, a branch ofNERVE, a branch of
anterior division ofanterior division of
mandibular nerve (whichmandibular nerve (which
is the 3rd part of V cranialis the 3rd part of V cranial
nerve- trigeminal nerve).nerve- trigeminal nerve).
Blood supplyBlood supply::
 Maxillary artery,Maxillary artery,
which is a branch ofwhich is a branch of
external carotid artery.external carotid artery.

ACTIONS OF MASSETERACTIONS OF MASSETER
Actions:Actions:
Elevates the mandible to close the mouthElevates the mandible to close the mouth
and to occlude the teeth in mastication.and to occlude the teeth in mastication.
Its activity in the resting position isIts activity in the resting position is
minimal.minimal.
 It has a small effect in side-to-sideIt has a small effect in side-to-side
movement, protraction and retraction.movement, protraction and retraction.

THE TEMPORALISTHE TEMPORALIS
TEMPORAL FASCIATEMPORAL FASCIA
 Thick aponeurotic sheet that roofs over the temporalThick aponeurotic sheet that roofs over the temporal
fossa and covers the temporalis muscle.fossa and covers the temporalis muscle.
 Fan shapedFan shaped
 Arises from whole of temporal fossa.(except the partArises from whole of temporal fossa.(except the part
formed by zygomatic bone) and deep surface offormed by zygomatic bone) and deep surface of
temporal fasciatemporal fascia
 Fibers converge and descend into a tendon .Fibers converge and descend into a tendon .
 It passes through the gap between the zygomatic archIt passes through the gap between the zygomatic arch
and the side of the skulland the side of the skull
 Attached to medial surface,apex,anterior and posteriorAttached to medial surface,apex,anterior and posterior
border of coronoid process and anterior border of theborder of coronoid process and anterior border of the
ramus of the mandible as far as last molar.ramus of the mandible as far as last molar.

RELATIONS OF TEMPORALISRELATIONS OF TEMPORALIS
SUPERFICIALSUPERFICIAL
 SkinSkin
 Auricularis anteriorAuricularis anterior
 Temporal fasciaTemporal fascia
 Superficial temporal vesselsSuperficial temporal vessels
 Auriculotemporal nerveAuriculotemporal nerve
 Temporal branch of facial nerveTemporal branch of facial nerve
 Galea aponeuroticaGalea aponeurotica
 Zygomatic archZygomatic arch
 massetermasseter

 Temporal fossaTemporal fossa
 Lateral pterygoidLateral pterygoid
 Superficial head of medialSuperficial head of medial
pterygoidpterygoid
 Small part of buccinatorSmall part of buccinator
 Maxillary arteryMaxillary artery
 Deep temporal nervesDeep temporal nerves
 Buccal vessels and nerveBuccal vessels and nerve
ANTERIOR border is seperatedANTERIOR border is seperated
from the zygomatic bone by afrom the zygomatic bone by a
mass of fat.mass of fat.

BLOOD SUPPLYBLOOD SUPPLY
 Deep temporal part ofDeep temporal part of
maxillary arterymaxillary artery
NERVE SUPPLYNERVE SUPPLY
 Temporalis isTemporalis is
supplied by the deepsupplied by the deep
temporal branches oftemporal branches of
the anterior trunk ofthe anterior trunk of
mandibular nerve.mandibular nerve.

ACTIONS OF TEMPORALISACTIONS OF TEMPORALIS
 Elevates the mandible,this movement requiresElevates the mandible,this movement requires
both the upward pull of anterior fibers andboth the upward pull of anterior fibers and
backward pull of the posterior fibers.backward pull of the posterior fibers.
 Posterior fibers draw the mandible backwardsPosterior fibers draw the mandible backwards
after it has been protuded.after it has been protuded.
 It is also a contrbutor to side to side grindingIt is also a contrbutor to side to side grinding
movement.movement.

LATERAL PTERYGOIDLATERAL PTERYGOID
ATTACHMENTSATTACHMENTS
It is a short thick muscle with two parts or headIt is a short thick muscle with two parts or head
 UPPERUPPER head arise from infratemporal surface andhead arise from infratemporal surface and
infratemporal crest of greater wing of sphenoid boneinfratemporal crest of greater wing of sphenoid bone
 LOWERLOWER head arise from lateral surface of lateralhead arise from lateral surface of lateral
pterygoid plate.pterygoid plate.
 Its fibers pass backwards and laterally to be inserted intoIts fibers pass backwards and laterally to be inserted into
a depression(pterygoid fovea)on the front of the neck ofa depression(pterygoid fovea)on the front of the neck of
the mandible and into the articular capsule and disc ofthe mandible and into the articular capsule and disc of
the temporomandibular articulation.the temporomandibular articulation.

RELATIONS OF LATERALRELATIONS OF LATERAL
PTERYGOIDPTERYGOID
 Ramus of the mandibleRamus of the mandible
 Maxillary arteryMaxillary artery
 Tendon of temporalis and the masseter,Tendon of temporalis and the masseter,
 Upper part of the medial pterygoidUpper part of the medial pterygoid
 Sphenomandibular ligamentSphenomandibular ligament
 Middle meningeal arteryMiddle meningeal artery
 Mandibular nerveMandibular nerve
UPPER BORDERUPPER BORDER
 Upper border is in relation with temporal and messetricUpper border is in relation with temporal and messetric
branches of the mandibular nervebranches of the mandibular nerve
LOWER BORDERLOWER BORDER
 In relation with lingual and inferior alveolar nerveIn relation with lingual and inferior alveolar nerve

 The lateralThe lateral
pterygoid is suppliedpterygoid is supplied
by a branch ofby a branch of
anterior division of theanterior division of the
mandibular nervemandibular nerve

PterygoidPterygoid
branch of 2ndbranch of 2nd
part of maxillarypart of maxillary
arteryartery

ACTIONS OF LATERALACTIONS OF LATERAL
PTERYGOIDPTERYGOID
 Assists in opening the mouth with suprahyoidAssists in opening the mouth with suprahyoid
muscle.muscle.
 Slow elongation while closing the mouth withSlow elongation while closing the mouth with
masseter and temporalismasseter and temporalis
 Acting with medial pterygoid of same sideActing with medial pterygoid of same side
advances the condyle ,while the jaw rotatesadvances the condyle ,while the jaw rotates
through the opposite condyle(when the medialthrough the opposite condyle(when the medial
and lateral pterygoid of the two sides contractand lateral pterygoid of the two sides contract
alternatively to produce side to side movementsalternatively to produce side to side movements
of mandible eg chewing).of mandible eg chewing).

 When the medial and lateral pterygoids of twoWhen the medial and lateral pterygoids of two
sides act together they protrude the mandible sosides act together they protrude the mandible so
that the lower incisors project in front of thethat the lower incisors project in front of the
other.other.
 Some authorities have ascribed different actionsSome authorities have ascribed different actions
to the two parts of pterygoid muscle.to the two parts of pterygoid muscle.
 The upper (superior)head being involved inThe upper (superior)head being involved in
chewingchewing
 The inferior in protrusion,electromyographicThe inferior in protrusion,electromyographic
records in rhesus monkey favors this view.records in rhesus monkey favors this view.

MEDIAL PTERYGOIDMEDIAL PTERYGOID
 It is a thick quadrilateral muscleIt is a thick quadrilateral muscle
 Attached to medial surface of lateral pterygoid plate andAttached to medial surface of lateral pterygoid plate and
grooved surface of pyramidal process of the palatinegrooved surface of pyramidal process of the palatine
bone.bone.
 A more superficial slip from the lateral surface ofA more superficial slip from the lateral surface of
pyramidal process of the palatine bone and tuberosity ofpyramidal process of the palatine bone and tuberosity of
maxillamaxilla
 Its fibers pass downwards laterally and backwardsIts fibers pass downwards laterally and backwards
 Attached by a strong tendinous lamina ,to the postero-Attached by a strong tendinous lamina ,to the postero-
inferior part of the medial surfaces of the ramus and theinferior part of the medial surfaces of the ramus and the
angle of the mandibleangle of the mandible
 It is attached as high as mandibular foramen and as farIt is attached as high as mandibular foramen and as far
forward as the mylohyoid grooveforward as the mylohyoid groovewww.indiandentalacademy.comwww.indiandentalacademy.com

RELATIONS OF MEDIALRELATIONS OF MEDIAL
PTERYGOIDPTERYGOID
 Upper part of muscle is separated from theUpper part of muscle is separated from the
lateral pterygoid muscle bylateral pterygoid muscle by
a) lateral pterygoid platea) lateral pterygoid plate
b) lingual nerveb) lingual nerve
c) inferior alveolar nervec) inferior alveolar nerve
 Inferiorly the muscle is separated from ramus ofInferiorly the muscle is separated from ramus of
mandible by same nerves,the maxillary arterymandible by same nerves,the maxillary artery
and sphenomandibular ligament.and sphenomandibular ligament.

 Branch of theBranch of the
main trunk of themain trunk of the
mandibular nerve.mandibular nerve.
 Pterygoid branchPterygoid branch
of 2nd part ofof 2nd part of
maxillary arterymaxillary artery

Actions of medial pterygoidActions of medial pterygoid
 Assits in elevating the mandibleAssits in elevating the mandible
 Acting with the lateral pterygoid they protrude itActing with the lateral pterygoid they protrude it
•Acting with lateral pterygoid of sameActing with lateral pterygoid of same
side advances the condyle ,while the jawside advances the condyle ,while the jaw
rotates through the oppositerotates through the opposite
condyle(when the medial and lateralcondyle(when the medial and lateral
pterygoid of the two sides contractpterygoid of the two sides contract
alternatively to produce side to sidealternatively to produce side to side
movements of mandible eg chewing)movements of mandible eg chewing)

Secondary muscles taking part inSecondary muscles taking part in
the masticationthe mastication
The 4 primary muscles of mastication are inThe 4 primary muscles of mastication are in
turn supported or supplemented by fewturn supported or supplemented by few
secondary muscles known assecondary muscles known as
SUPRAHYOID GROUP of muscles theySUPRAHYOID GROUP of muscles they
areare
DIGASTRICDIGASTRIC
MYLOHYOIDMYLOHYOID
GENIOHYOIDGENIOHYOID
STYLOHYOID is other suprahyoid muscle,STYLOHYOID is other suprahyoid muscle,
which does not take part in masticationwhich does not take part in masticationwww.indiandentalacademy.comwww.indiandentalacademy.com

DIGASTRICDIGASTRIC
•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
agains resistance. Elevation of hyoid bone
MYLOHYOID
•The secondary role of this muscle is evidnent as a
depressor seen in action when mouth is to be
opened against resistance.
•It elevates the floor of mouth to help in deglutition.

GENIOHYOIDGENIOHYOID
•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

Normal function versusNormal function versus
parafunctionparafunction
The image to the left is demonstrating
normal reciprocal functioning of the Lateral
Pterygoids and
Masseters/Med.Pteygoids/Temporalis'.
The Lateral Pterygoids advance the
condyles, thereby opening the mouth
(depressing the mandible), with the
assistance of the Digastric
The oblique orientation of the Masseters
and Medial Pterygoids create a sling. The
non-working side Medial Pterygoid contacts
simultaneously with the opposide side
working Masseter.
It is this oblique orientation of the
Med.Pterygoids and Masseters that create
the functional "shift" of the mandible, not an
unilateral contraction of a Lateral Pterygoid
.www.indiandentalacademy.comwww.indiandentalacademy.com

 In the event theIn the event the
Temporalis' do not ceaseTemporalis' do not cease
their active contractions,their active contractions,
scenarios of varyingscenarios of varying
degrees of parafunctiondegrees of parafunction
result, as the Lateralresult, as the Lateral
Pterygoids encounterPterygoids encounter
resistance to theirresistance to their
attempts at condylarattempts at condylar
advancement, therebyadvancement, thereby
increasing their intensityincreasing their intensity
of contraction and strainof contraction and strain
on their origins andon their origins and
insertions: the pterygoidinsertions: the pterygoid
plates of the sphenoidplates of the sphenoid
bone, and the condylarbone, and the condylar
neck and disc. neck and disc.

The maximum clenching intensity occurs inThe maximum clenching intensity occurs in
the musculoskeletally stable positionthe musculoskeletally stable position
 The mandibular positionThe mandibular position
of the temporalis' mostof the temporalis' most
intense contraction is notintense contraction is not
when the teeth arewhen the teeth are
together, but when theytogether, but when they
are a particular distanceare a particular distance
apart, and separated byapart, and separated by
an object (such as aan object (such as a
splint, or food).splint, or food).

Muscles of mastication / dental implant courses by Indian dental academy

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Viewers also liked

Viewers also liked (17)

Similar to Muscles of mastication / dental implant courses by Indian dental academy

Similar to Muscles of mastication / dental implant courses by Indian dental academy (20)

More from Indian dental academy

More from Indian dental academy (20)

Recently uploaded

Recently uploaded (20)

Muscles of mastication / dental implant courses by Indian dental academy

Editor's Notes