Muscles of mastication / dental crown & bridge courses

MUSCLESOF

MASTICATION

INDIAN DENTAL ACADEMYINDIAN DENTAL ACADEMYLeader in continuing Dental EducationLeader in continuing Dental Education

www.indiandentalacademy.com\

Contents Contents IntroductionIntroductionPrimary Muscles Of MasticationPrimary Muscles Of MasticationAccessory Muscles Of MasticationAccessory Muscles Of MasticationDevelopment Of Muscles Of MasticationDevelopment Of Muscles Of MasticationFunction Of Muscles Function Of Muscles Applied AnatomyApplied AnatomyDisorders Of Muscles Disorders Of Muscles ConclusionConclusionReferencesReferences


INTRODUCTIONINTRODUCTION

Skeletal components of body are held Skeletal components of body are held together and moved by skeletal together and moved by skeletal muscles.muscles.

The attachment of the muscle to the The attachment of the muscle to the fixed part is known as fixed part is known as originorigin and and attachment to the movable part is attachment to the movable part is insertioninsertion..


PRIMARY MUSCLES OF PRIMARY MUSCLES OF MASTICATIONMASTICATION

The muscles of mastication are of two types The muscles of mastication are of two types PrimaryPrimary AccessoryAccessory

PRIMARY MUSCLESPRIMARY MUSCLES MasseterMasseter TemporalisTemporalis Lateral PterygoidLateral Pterygoid Medial PterygoidMedial Pterygoid


MasseterMasseter

Greek word “Greek word “masetermaseter”- a ”- a chewerchewer

This is a This is a quadrilateral quadrilateral muscle which covers the muscle which covers the lateral part of ramus of lateral part of ramus of mandible. mandible.

It consists of It consists of 3 layers3 layers which blend anteriorly.which blend anteriorly.


OriginOrigin Superficial layer Superficial layer

(largest)(largest) maxillary processmaxillary process of of

zygomatic bone zygomatic bone anterior 2/3anterior 2/3rdrd of of inferior inferior

borderborder of zygomatic arch of zygomatic arch Middle layerMiddle layer

medial aspectmedial aspect of anterior of anterior 2/32/3rdrd of zygomatic arch of zygomatic arch

lower borderlower border of posterior of posterior third of zygomatic archthird of zygomatic arch

Deep layerDeep layer – – arises from the arises from the deep deep

surfacesurface of zygomatic arch. of zygomatic arch.


Insertion Insertion

Superficial layerSuperficial layer AngleAngle of mandible of mandible Lower posterior halfLower posterior half of of

lateral surface of lateral surface of mandibular ramus.mandibular ramus.

Middle layerMiddle layer central partcentral part of mandibular of mandibular

ramus.ramus.

Deep layerDeep layer upper partupper part of mandibular of mandibular

ramusramus coronoidcoronoid process. process.


MasseterMasseter Nerve supplyNerve supply

Supplied by Supplied by masseteric nervemasseteric nerve a a branch of anterior division of branch of anterior division of mandibular nervemandibular nerve

Blood supplyBlood supply Supplied by Supplied by masseteric arterymasseteric artery

branch of maxillary artery branch of maxillary artery Venous drainage through Venous drainage through

masseteric veinmasseteric vein

ActionAction The muscle The muscle elevates elevates the the

mandible to close the mouth, mandible to close the mouth, and clenches the teethand clenches the teeth


TemporalisTemporalis

It is a powerful fan shaped It is a powerful fan shaped chewing muscle which chewing muscle which fills temporal fossafills temporal fossa

OriginOrigin Temporal fossa from Temporal fossa from

infatemporal - linesinfatemporal - lines excluding excluding

zygomatic bonezygomatic bone Temporal fasciaTemporal fascia

InsertionInsertion Margins & deep surfaceMargins & deep surface of of

the coronoid processthe coronoid process Anterior borderAnterior border of ramus of of ramus of

mandiblemandible


TEMPORALISTEMPORALIS Nerve supplyNerve supply

Deep temporal branchesDeep temporal branches from from anterior division of mandibular anterior division of mandibular nervenerve

Blood supplyBlood supply Superficial temporal arterySuperficial temporal artery branch branch

of maxillary artery of maxillary artery superficial temporal veinsuperficial temporal vein & middle & middle

temporal veintemporal vein

ActionAction Elevates Elevates the mandible the mandible posterior fibers posterior fibers retractretract the the

protruded mandibleprotruded mandible

Applied anatomyApplied anatomy Sudden reflex contraction of Sudden reflex contraction of

temporalis in times of trauma can temporalis in times of trauma can cause the cause the fracturefracture of coronoid of coronoid processprocess www.indiandentalacademy.com\

Lateral pterygoidLateral pterygoid

It is a short thick conical muscle with definite upper and lower headsIt is a short thick conical muscle with definite upper and lower heads OriginOrigin

Upper head arises from Upper head arises from infra temporal surfaceinfra temporal surface and crest of and crest of greater wing of greater wing of sphenoid bonesphenoid bone

Lower head from the Lower head from the lateral pterygoid platelateral pterygoid plate InsertionInsertion

Fibers run backwards and laterally and converge into the Fibers run backwards and laterally and converge into the pterygoid foveapterygoid fovea on anterior surface of neck of mandibleon anterior surface of neck of mandible

Into anterior margin of Into anterior margin of articular discarticular disc and and capsule capsule of TMJ of TMJwww.indiandentalacademy.com\

Lateral pterygoidLateral pterygoid Nerve supplyNerve supply

A branch from anterior division A branch from anterior division of the of the mandibular nervemandibular nerve

Blood supplyBlood supply Maxillary artery Maxillary artery Ascending palatine arteryAscending palatine artery

ActionAction DepressesDepresses the mandible to the mandible to

open mouthopen mouth Lat. & Medial pterygoid of both Lat. & Medial pterygoid of both

sides contract to sides contract to protrudeprotrude the the mandible mandible

when contract alternatively when contract alternatively produces produces chewing movementschewing movements


Medial pterygoidMedial pterygoidThis is This is quadrilateral musclequadrilateral muscle having a small having a small superficialsuperficial head head and a large and a large deepdeep head which head which forms the major part of muscleforms the major part of muscle

OriginOrigin Superficial head from Superficial head from maxillary maxillary

tuberositytuberosity Deep head from medial surface of Deep head from medial surface of

lateral pterygoid platelateral pterygoid plate and part of and part of palatine bonepalatine bone

InsertionInsertion Fibers run backwards, downwards Fibers run backwards, downwards

and laterally into the roughened and laterally into the roughened area of area of medial surface of the angle medial surface of the angle mandiblemandible


Medial pterygoidMedial pterygoid Nerve supplyNerve supply

Branch of the Branch of the main trunkmain trunk of of mandibular nervemandibular nerve

Blood supplyBlood supply By facial artery By facial artery lingual veinlingual vein

ActionAction ElevatesElevates and and protrudesprotrudes the the

mandiblemandible

Applied anatomyApplied anatomy During improper inferior During improper inferior

alveolar nerve block, the alveolar nerve block, the needle may prick & irritate the needle may prick & irritate the muscle causing spasm & muscle causing spasm & consequently trismusconsequently trismus


RelationsRelationsLateral PterygoidLateral Pterygoid

Superficial:-Superficial:- MasseterMasseter Ramus of mandibleRamus of mandible Tendon of temporalisTendon of temporalis Maxillary arteryMaxillary artery

Deep:-Deep:- Mandibular nerveMandibular nerve Middle Meningeal arteryMiddle Meningeal artery Sphenomandibular Sphenomandibular

ligamentligament Deep head of medial Deep head of medial

pterygoidpterygoid

Structures emerging at upper Structures emerging at upper border:-border:- Deep temporal nerve Deep temporal nerve Masseteric nerveMasseteric nerve

Structures emerging at lower Structures emerging at lower border:-border:- Lingual nerveLingual nerve Inferior alveolar nerveInferior alveolar nerve Middle meningeal artery Middle meningeal artery

passes upwards deep to itpasses upwards deep to it Structures passing through Structures passing through

gap between two heads:-gap between two heads:- Maxillary artery enters Maxillary artery enters

the gapthe gap Buccal branch of Buccal branch of

mandibular nerve comes mandibular nerve comes out of that gapout of that gap


RelationsRelationsMedial PterygoidMedial Pterygoid

Superficial relations:-Superficial relations:- Upper part of muscle is separated from Lateral Pterygoid by:-Upper part of muscle is separated from Lateral Pterygoid by:-

Lateral pterygoid plateLateral pterygoid plate Lingual nerveLingual nerve Inferior alveolar nerveInferior alveolar nerve

Lower part of muscle is separated from Lateral Pterygoid by:-Lower part of muscle is separated from Lateral Pterygoid by:- Mandibular ramusMandibular ramus Inferior alveolar nerveInferior alveolar nerve Lingual nerveLingual nerve Maxillary arteryMaxillary artery Sphenomandibular ligamentSphenomandibular ligament

Deep relationsDeep relations Tensor veli palatiniTensor veli palatini Superior constrictor of pharynxSuperior constrictor of pharynx StyloglossusStyloglossus Stylopharyngeus attached to styloid processStylopharyngeus attached to styloid process


ACCESSORY MUSCLES OF ACCESSORY MUSCLES OF MASTICATIONMASTICATION

DIGASTRICDIGASTRIC MYLOHYOIDMYLOHYOID GENIOHYOIDGENIOHYOID PLATYSMAPLATYSMA BUCCINATORBUCCINATOR


Digastric muscleDigastric muscle This muscle has 2 bellies anterior & posterior This muscle has 2 bellies anterior & posterior OriginOrigin

Anterior belly originates from Anterior belly originates from Digastric fossaDigastric fossa at inner side of lower at inner side of lower border of mandibleborder of mandible

InsertionInsertion Anterior belly descend to hyoid bone & join Anterior belly descend to hyoid bone & join intermediate tendonintermediate tendon which which

is connected to hyoid bone by fibrous tissue called Digastric pulleyis connected to hyoid bone by fibrous tissue called Digastric pulley

Nerve supplyNerve supply By By Mylohyoid nerveMylohyoid nerve branch of inferior alveolar nerve which is a branch branch of inferior alveolar nerve which is a branch

of mandibular nerveof mandibular nerve

Blood supplyBlood supply By By lingual artery & veinlingual artery & vein

ActionAction Depresses the mandible and mostly acts in maximal depressionDepresses the mandible and mostly acts in maximal depression


Mylohyoid muscleMylohyoid muscleThis muscle forms the floor of the mouthThis muscle forms the floor of the mouth OriginOrigin

Whole length of Whole length of Mylohyoid line to the 3Mylohyoid line to the 3rdrd molar molar of inside of of inside of mandiblemandible

InsertionInsertion Fibers pass down & some are inserted into Fibers pass down & some are inserted into median raphaemedian raphae & rest & rest

into the into the hyoid bonehyoid bone

Nerve supplyNerve supply By By Mylohyoid nervesMylohyoid nerves branch of inferior alveolar nerve branch of inferior alveolar nerve

ActionAction Elevation of the floor of mouth in the 1Elevation of the floor of mouth in the 1 stst stage of deglutition stage of deglutition Elevates hyoid bone or depresses the mandibleElevates hyoid bone or depresses the mandible


Geniohyoid muscleGeniohyoid muscleThis is a narrow muscle lying above the medial part of This is a narrow muscle lying above the medial part of

MylohyoidMylohyoid

OriginOrigin From the From the genial tuberclegenial tubercle of symphysis of symphysis

InsertionInsertion At anterior surface of body of At anterior surface of body of hyoid bonehyoid bone

Nerve supplyNerve supply Supplied by the Supplied by the hypoglossal nervehypoglossal nerve

ActionAction Depresses mandible when hyoid is fixedDepresses mandible when hyoid is fixed


PlatysmaPlatysmaThis is a large thin muscleThis is a large thin muscle OriginOrigin

Upper parts of Upper parts of pectoral and deltoid fasciaepectoral and deltoid fasciae

InsertionInsertion Anterior fibersAnterior fibers –base of mandible –base of mandible Posterior fibersPosterior fibers –skin of lower face and lip –skin of lower face and lip

Nerve supply Nerve supply cervical branch of cervical branch of Facial nerveFacial nerve

ActionAction DepressesDepresses the lower jaw and lip the lower jaw and lip


BuccinatorBuccinator Origin:-Origin:-

Upper fibers – Upper fibers – maxilla opposite molarsmaxilla opposite molars Lower fibers – Lower fibers – mandible opposite molar teethmandible opposite molar teeth Middle fibersMiddle fibers – pterygomandibular raphae – pterygomandibular raphae

Insertion :-Insertion :- Upper fibersUpper fibers – straight to upper lip – straight to upper lip Lower fibersLower fibers – straight to lower lip – straight to lower lip Middle fibersMiddle fibers – decussate before passing to the lip – decussate before passing to the lip

Nerve supply – Nerve supply – lower buccal branch of lower buccal branch of facial nervefacial nerve

Actions –Actions – flattens cheekflattens cheek against gums and teeth against gums and teeth prevents prevents accumulation of foodaccumulation of food in the vestibule in the vestibule


MANDIBULAR MOVEMENTS AND MANDIBULAR MOVEMENTS AND ROLE PLAYED BY MUSCLESROLE PLAYED BY MUSCLES

Elevation of mandibleElevation of mandible The The temporalistemporalis elevates the coronoid process elevates the coronoid process Masseter and medial pterygoidMasseter and medial pterygoid elevate the angle of elevate the angle of

mandiblemandible Lateral pterygoid relaxes as muscles exert upward Lateral pterygoid relaxes as muscles exert upward

tractiontraction

Depression of mandibleDepression of mandible Lateral pterygoidLateral pterygoid exerts a forward pull on neck of exerts a forward pull on neck of

mandiblemandible Sup. HeadSup. Head of lateral pterygoid pulls articular disc of lateral pterygoid pulls articular disc

down of articular tubercledown of articular tubercle AccessoryAccessory muscle help in drawing mandible down. muscle help in drawing mandible down.


Protrusion of mandibleProtrusion of mandible Lateral pterygoid and medial pterygoid Lateral pterygoid and medial pterygoid

contracts contracts

Retrusion of mandibleRetrusion of mandible Posterior fibers of Posterior fibers of TemporalisTemporalis with help of with help of

Mylohyoid, Digastric & Geniohyoid draw the Mylohyoid, Digastric & Geniohyoid draw the mandible backwardsmandible backwards

Lateral shift of mandibleLateral shift of mandible contraction of contraction of lateral pterygoidlateral pterygoid on one side on one side

and medial pterygoid on the other side. and medial pterygoid on the other side.


Actions Actions


Articular DiscArticular Disc


DEVELOPMENT OF THE DEVELOPMENT OF THE MUSCLES OF MASTICATIONMUSCLES OF MASTICATION

All the muscles of mastication develop from the All the muscles of mastication develop from the mesoderm of mesoderm of 11stst brachial arch brachial arch (mandibular arch) (mandibular arch)

Therefore, they are supplied by Therefore, they are supplied by mandibular nerve.mandibular nerve.

Accessory muscles:-Accessory muscles:- Digastric Digastric -- 11stst ARCH ARCH MylohyoidMylohyoid -- 11stst ARCH ARCH GeniohyoidGeniohyoid -- Upper cervical somitesUpper cervical somites PlatysmaPlatysma -- 22ndnd ARCH ARCH BuccinatorBuccinator -- 22ndnd ARCH ARCH


Development Development


Temporalis muscle


MasseterMasseter


Jaw reflexesJaw reflexes


Force Force


APPLIED ANATOMYAPPLIED ANATOMYThe contraction of muscles of mastication affects the The contraction of muscles of mastication affects the

displacement of fracturedisplacement of fracture

Action of these muscles minimize displacement in Action of these muscles minimize displacement in favorablefavorable fracture fracture

In case of In case of unfavorableunfavorable fracture they tend to contribute to fracture they tend to contribute to fracture displacement fracture displacement

When angle fracture is When angle fracture is horizontalhorizontal the maseter, temporalis, the maseter, temporalis, medial pterygoid cause upward and medial displacement of medial pterygoid cause upward and medial displacement of proximal segmentproximal segment

When angle When angle fracturefracture is vertical the medial and lateral is vertical the medial and lateral pterygoid results in medial displacement of proximal pterygoid results in medial displacement of proximal segmentsegment www.indiandentalacademy.com\

Fracture Fracture


Undifferentiated painUndifferentiated pain


DISORDERS OF MUSCLESDISORDERS OF MUSCLES

MYASTHENIA GRAVISMYASTHENIA GRAVIS TRISMUSTRISMUS MYOFACIAL PAIN DYSFUNCTION MYOFACIAL PAIN DYSFUNCTION

SYNDROMESYNDROME


MYASTHENIA GRAVISMYASTHENIA GRAVIS

It is a chronic disease with It is a chronic disease with progressive progressive weaknessweakness of skeletal muscles caused by of skeletal muscles caused by destruction of destruction of acetyl cholineacetyl choline receptors at receptors at neuromuscular junction.neuromuscular junction.

This is This is autoimmune conditionautoimmune condition.. Muscles of mastication are involved before Muscles of mastication are involved before

any other muscle group.any other muscle group. Difficulty in mastication ,deglutition and Difficulty in mastication ,deglutition and

dropping of jaw is seen.dropping of jaw is seen.


TRISMUSTRISMUSStiffness of muscles of masticationStiffness of muscles of mastication EtiologyEtiology

Local infectionLocal infection –pericoronitis, dentoalveolar abscess –pericoronitis, dentoalveolar abscess Direct Direct traumatrauma to muscles of mastication to muscles of mastication PressurePressure is on Medial Pterygoid and Masseter leading is on Medial Pterygoid and Masseter leading

to irritation and consequent spasmto irritation and consequent spasm

TETANUS TETANUS Infection is caused by Infection is caused by clostridium tetanusclostridium tetanus which which

releases powerful endotoxin thus destroying the releases powerful endotoxin thus destroying the spinal inhibition, thus causing uncontrolled muscle spinal inhibition, thus causing uncontrolled muscle spasmspasm

In muscles of mastication it causes In muscles of mastication it causes lock jawlock jaw


ParalysisParalysis

To test the To test the motor functionmotor function of the fifth of the fifth nerve we ask the patient to nerve we ask the patient to clench his clench his teethteeth.. The The TemporalTemporal and the and the MasseterMasseter muscle muscle

should stand out with should stand out with equal prominenceequal prominence on on each side.each side.

If paralysis on If paralysis on one sideone side then then Muscles wont become prominent on that side Muscles wont become prominent on that side If asked to open mouth jaw will If asked to open mouth jaw will deviate deviate

towards the paralysed side.towards the paralysed side.


MYOFACIAL PAIN MYOFACIAL PAIN DYSFUNCTION SYNDROMEDYSFUNCTION SYNDROME

Spasm of musclesSpasm of muscles of mastication occurs due to of mastication occurs due to OveruseOveruse TraumaTrauma StressStress StrainStrain

Signs and symptomsSigns and symptoms Unilateral dull Unilateral dull painpain in ear in ear TendernessTenderness of one or more muscles of of one or more muscles of

mastication on palpationmastication on palpation LimitationLimitation or deviation of mandibular opening or deviation of mandibular opening ClickingClicking or popping at TMJ or popping at TMJ


Muscles and MalocclusionMuscles and Malocclusion

According to According to Moss theoryMoss theory, as growth of , as growth of jaws depends on the activity of muscles, jaws depends on the activity of muscles, excessive muscle activity can excessive muscle activity can restrict restrict growth.growth.

Even no use of muscle can lead to its Even no use of muscle can lead to its dystrophydystrophy and no development of jaws. and no development of jaws.


Functions Functions

SpeechSpeech

Swallowing and deglutitionSwallowing and deglutition

MasticationMastication

Postural rest position of mandiblePostural rest position of mandible


CONCLUSIONCONCLUSION

Muscles of mastication help in chewing, Muscles of mastication help in chewing, elevating protruding, retruding and elevating protruding, retruding and lateral shifting of lateral shifting of mandibular movementsmandibular movements..

It also helps in speech, thus it is important It also helps in speech, thus it is important for a for a normal physical healthnormal physical health which leads to which leads to a secure psychological influence a secure psychological influence


BibliographyBibliography B.D.Chaurasia’s Human Anatomy Vol 3 3rd Edt. Pg. 181-

191 G.J.Romanes-cunnigham’s Manual Of Practical Anatomy

15th Ed. Vol 3 Pg 139-143. Peter L Williams Et Al- Gray’s Anatomy 38th Edt. Pg 1726-

1732 Richard S Snell-clinical Anatomy For Medical Student 5th

Ed. Pg 737-740 Ming J Lee- Grants Atlas Of Anatomy 10th Edition Pg 678-

680 Mc Minn Hutchings- Color Atlas Of Anatomy 3rd Ed. Pg 50-

51 John W Rohan, Chihiro, Elke Lutjer- Color Atlas Of

Anatomy 9th Edition Loe,mcgrager’s Synopsis Of Surgical Anatomy 12th Ed.Pg

373


Muscles of mastication / dental crown & bridge courses

Education

Transcript of Muscles of mastication / dental crown & bridge courses