Mandibular movements/ dental implant courses

MANDIBULAMANDIBULA
RR
MOVEMENTSMOVEMENTS
INDIAN DENTAL ACADEMYINDIAN DENTAL ACADEMY
Leader in continuing Dental EducationLeader in continuing Dental Education
www.indiandentalacademy.comwww.indiandentalacademy.com

CONTENTSCONTENTS
 Introduction
 Anatomy of TMJ
 Musclesof Mastication
 Neurologic structures& neuromuscular functions
 Border movementsof Mandibular
 Eccentric Mandibular Movements
 Major Functionsof Masticatory System
 MethodsUsed For Recording Mandibular
Movements
 Clinical Significanceof Mandibular Movements
 Conclusion
 References

INTRODUCTIONINTRODUCTION
 Themasticatory system isacomplex and highly refined unit.
 It isthefunctional unit of thebody primarily responsiblefor
chewing speaking and swallowing.
 Thesystem ismadeof bone,joints, ligaments,teeth and
muscles. and movement isregulated by intricateneurological
control system
 During performanceof variousfunctionsthereisadelicate
balancebetween variouscomponents.
 Precisemovement of themandibleisrequired to movethe
teeth efficiently acrosseach other during function

ANATOMY OF TMJANATOMY OF TMJ
 TMJisoneof themost complex jointsin thebody.
 It iscalled asGINGLYMOARTRODIAL JOINT.
 TMJconsistsof 4 main structures:-
 Condyle
 Temporal bone(Squamouspart)
 Articular disc
 Ligaments

CONDYLE
 It istheportion of themandiblethat articulateswith
thecranium, around which movement occurs.

TEMPORALBONE
 Themandibular condylesarticulatesat thebaseof thecranium
with thesquamousportion of thetemporal bone.
 Thisportion madeup of ConcaveMandibular Fossacalled as
ARTICULAR OR GLENOID FOSSA.
 SQUAMOTYMPANIC FISSURE – Posterior to mandibular
fossa.
 Anterior to fossaconvex bony prominencecalled ARTICULAR
EMINENCE. www.indiandentalacademy.comwww.indiandentalacademy.com

TMJconsist of
 Upper articular lower articular interarticular disc
surface surface
Formed of Formed of
Articular eminence head of themandible
Anterior part of (condyle)
mandibular fossa
 TMJisclassified asaCOMPOUND JOINT.
 Functionally articular disc servesasanon ossified bone.

 ARTICULARDISCARTICULARDISC
 Composed of densefibrousconnectivetissue, most part of it isdevoid of blood
vesselsand nervesfibers.
 Extremeperiphery of thedisc isslightly innervated.
 In SAGITTAL PLANE it isdivideinto 3 regions(according to thickness).
 ANTERIOR ZONE POSTERIOR ZONE INTERMIDIATE ZONE
Posterior border isslightly thinnest areaof thedisc
thicker than anterior border
SAGITTAL PLANE
ANTERIOR(FRONTAL)
PLANE

Attachment of Articular DiscAttachment of Articular Disc:-:-
 Articular disc is attached to the capsular ligament..
 It divides the joint cavity into- SUPERIOR
 INFERIOR JOINT CAVITY
 TMJ is referred to as SYNOVIAL JOINTwww.indiandentalacademy.comwww.indiandentalacademy.com

LIGAMENTSLIGAMENTS:-:-
Musclesmoveand ligamentslimit.
Ligamentsdo not enter actively into joint function,
rather they act aspassiverestraining devicesto limit
& restrict border movements.
3 functional ligamentssupport theTMJare:-
 Collateral ligament
 Capsular ligament
 Temporomandibular ligament
2 accessory ligamentsare:-
 Sphenomandibular ligament
 Stylomandibular ligament

COLLATERAL(DISCAL) LIGAMENTS:-COLLATERAL(DISCAL) LIGAMENTS:-
They attach themedial & lateral bordersof
articular disc to thepolesof thecondyle.
Commonly called asDISCALLIGAMENTS.
2 TYPES:-

Medial discal ligament

Lateral discal ligament
They aretrueligaments
Function :

CAPSULAR LIGAMENTCAPSULAR LIGAMENT:-:-
 EntireTMJissurrounded & encompassed by the
capsular ligament.
 Attachment :-
 Superiorly
 Inferiorly
 Function :-
It resistsany medial, lateral or inferior forcesthat
tend to separateor dislocatethearticular surfaces.

TEMPOROMANDIBULAR LIGAMENTTEMPOROMANDIBULAR LIGAMENT:-:-
 Lateral aspect of thecapsular ligament isreinforced by strong,
tight fibersthat makeup thelateral or temporomandibular
ligament.
 TheTM ligament iscomposed of :-
Outer obliqueportion Inner horizontal portion

FUNCTION
 OUTER OBLIQUE
PORTION:
1) They resist extensive
dropping of he
condyle..
2) It also influencesthe
normal opening
movement.
 INNER
HORIZONTAL
PORTION
1) Limitsposterior
movement of condyle
2) It also protectslateral
pterygoid musclefrom
overlengthening or
extension

ACCESSORY LIGAMENTSACCESSORY LIGAMENTS
 Sphenomandibular Ligament
 Stylomandibular Ligament
 Function:
1) Taut - when mandibleisprotruded
2) Most relaxed – when mandibleisopened.
So, limitsexcessiveprotrusivemovement of mandible.
3) Sharesin activity of themedial pterygoid muscle

MUSCLES OF MASTICATIONMUSCLES OF MASTICATION
 Theskeletal musclesprovidefor thelocomotion necessary for
theindividual to survive.
 PRIMARY MUSCLESOF MASTICATION
 Masseter
 Temporalis
 Medial Pterygoid
 Lateral Pterygoid
 SECONDARY MUSCLESOF MASTICATION
Thesuprahyoid group of musclesbeing used assecondary
or supplementary musclesthey are
 Digastric
 Mylohyoid
 Geniohyoid www.indiandentalacademy.comwww.indiandentalacademy.com

MASSETERMASSETER:-:-
 Quadrilateral muscleand
consist of threelayers.
 Origin:
 Superficial layer:
 Middlelayer:
 Deep layer
 Insertion:
 Superficial layer
 Middleand deep fibers
passvertically downward.

FunctionFunction
Some fibers from innerpart
of the muscle are inserted
horizontally into the capsule
and meniscus of mandibular
joint exerting a LATERAL
PULLon the meniscus
Deep segment pulls
mandible RETRUEDrelation
Massetercontracts
ELEVATES the mandible
in the direction of the
fibers

MEDIAL PTERYGOIDMEDIAL PTERYGOID
 It is a thick quadrilateral muscle
 Origin Insertion

FUNCTION OFMEDIALPTERIGOIDMUSCLE
1. Along with masseter it formsa MUSCULARMUSCULAR
SLINGSLING tthat supportsthemandibleat mandibular
angle.
2. When fiberscontract themandibleis ELEVATEDELEVATED..
3. Muscleisactivein PROTRUDINGPROTRUDING themandible..
4. Unilateral contraction will bring about
mediotrusivemovement of themandible.

TEMPORALIS
 It isalarge, fan
shaped muscle.
 Origin
 Insertion

 It can be divided into 3 distinct portions
consistsof fibers fibersrun obliquely fibersarealigned
that aredirected acrossthelateral almost horizontally
almost vertically aspect of theskull coming forward above
(forward-downwards) theear
when it contracts when it contracts it contractsand
mandibleisraised mandibleiselevated retrudesmandible
vertically and retruded {Du Brul-suggested
((elevateselevates)) that itscontraction
elevatesand slightlyelevatesand slightly
retrudesretrudes
ANTERIORPORTION MIDDLEPORTION POSTERIOR PORTION

ELEVATION OFMANDIBLEELEVATION OFMANDIBLE POSTERIORFIBERDRAWSPOSTERIORFIBERDRAWS
MANDIBLEBACKWARDSMANDIBLEBACKWARDS

 Becauseangulation of themuscle
fibersvariesthetemporalisiscapable
of coordinating closing movements
 Hence it is a significant po sitio ningHence it is a significant po sitio ning
muscle o f the mandiblemuscle o f the mandible

LATERALPTERYGOIDLATERALPTERYGOID
 2 different portions or bellies:-
 Inferior
 Superior

Function
 Superior Lateral Pterygoid:-
 During opening the
superior lateral pterygoid
remainsinactive, becomes
activeonly in conjunction
with elevator
muscles.
 It isactiveduring po wer
stro ke & when teeth are
held
together.
Closing
 Inferior Lateral Pterygoid:-
 When right & left ILPcontracts
simultaneously,
thecondylesare
pulled down
thearticular
eminences&
themandible
isprotruded.
 Unilateral contraction createsa
mediotrusivemovement of the
condyle& causesalateral
movement of themandibleto the
oppositeside.
opening
protracting
Lateral movement inwww.indiandentalacademy.comwww.indiandentalacademy.com

SIDE TO SIDE GRINDINGSIDE TO SIDE GRINDING
MOVEMENTMOVEMENT
 When lateral pterygoid
contractswith medial
pterygoid of sameside, the
condyleadvanceson that side
,whilethejaw rotatesthrough
theoppositecondyle
 when themedial and lateral
pterygoid of thetwo sides
contract alternatively to
producesideto side
movementsof mandibleeg
chewing

Medial and lateral pterygoid act togethertoMedial and lateral pterygoid act togetherto
protrude the mandibleprotrude the mandible

DIGASTRICS:-DIGASTRICS:-
 Not considered amuscleof mastication, but it doeshavean
important influenceon thefunction of themandible.
 Divided into 2 portions:-
 Posterior belly
 Anterior belly

 FunctionFunction:-:-
 When right & left digastrics
contract & thesuprahyoid &
infrahyoid musclesfix the
hyoid bone, the
mandibleis
depressed & pulled backward &
theteeth arebrought out of contact.
 When mandibleisstabilized,
thedigastric muscleswith the
suprahyoid & infrahyoid
muscles elevatethe
hyoid bone, whichwww.indiandentalacademy.comwww.indiandentalacademy.com

The combinded efforts of the Digastrics andThe combinded efforts of the Digastrics and
Lateral Pterygoids provide fornatural jawLateral Pterygoids provide fornatural jaw
opening.opening.

 Other acessory
muscles:
 Surahyoid
 Infrahyoid
muscle
 Sternocleidoma
stoid
 Posterior
cervical muscles

 Woelfel J.B., Hickey J.C., Stacy R.W. & Rinear L. (1960)Woelfel J.B., Hickey J.C., Stacy R.W. & Rinear L. (1960)
–– conducted a study on electromyographic analysis of
jaw movements. The objective of the study were-
1)To determine the range of variability of muscular activity
in jaw movements.
2)To determine the range of variability in a series of
electromyograms.
3)To provide an analysis of the role played by the external
pterygoid muscles in trained (learned) jaw movements.

 They concluded that:-
1) Thetemporal muscleiscapableof unilateral and fractional
responsebut doesnot show increased activity in any part during
protrusion or uncontrolled openings.
2)Theright and left digastric musclesdid not function individually. Their
greatest activity wasduring uncontrolled openingsand retrusion of the
mandible.
3)Themasseter musclehad thegreatest activity during clenching
into centric occlusion.
4)Theexternal pterygoid musclewasvery activeduring
contralateral excursions, uncontrolled openings, and protrusion
but wasinactiveduring hingeopeningsof approximately 1 cm.

NEUROLOGIC STRUCTURE &NEUROLOGIC STRUCTURE &
NEUROMUSCULAR FUNCTIONNEUROMUSCULAR FUNCTION
 Function of masticatory system iscomplex. A highly refined
neurologic control system regulates& coordinatesthe
activitiesof entiremasticatory system
 Thebasic component of neuromuscular system isthe
MOTOR UNIT (which consist of number of musclefibers
that areinnervated by motor neuron)
 MUSCLE FUNCTION:-MUSCLE FUNCTION:-
ISOTONIC CONTRACTION: contraction or an overall
shortening.
ISOMETRIC CONTRACTION:ISOMETRIC CONTRACTION: contraction without shortening
CONTROLLEDRELAXATIONCONTROLLEDRELAXATION :: stimulation of motor unit is
discontinued, fibersof motor unit relax and return to normal
length. thusaprecisemusclelengthening can occur that
allowsslow and deliberatemovement

NEUROLOGIC STRUCTURES:-
 The masticatory system consists of
following receptors to monitorthe status
of its components:-
1)1) MUSCLE SPINDLE-
 Skeletal muscleconsistsof two typesof muscle
fibers–
a) Extrafusal fibers(contractile)
b) Intrafusal fibers(minutely contractile)

 A bundleof intrafusal fibersbound by a
connectivetissuesheath iscalled muscle
spindle.
 Within each spindlethenuclei of the
intrafusal fibersarearranged in 2 distinct
fashions:-
1) Chainlike(nuclear chain type)
2) Clumped (nuclear bag type)
 Therearetwo typesof afferent nervesthat
supply theintrafusal fibers. They are:
1) Primary endingsor annulospiral endings
2) Secondary endingsor flower spray endings
 Efferent supply of intrafusal fibersisby
fusimotor nervefibers(γ efferent).

 When muscleisstretched:
 Intrafusal & extrafusal fibersarestretched
 Annulospiral & flower spray endingsareactivated
 Afferent neuronscarry information to trigeminal
mesencephalic nucleus
 TheCNSthen sendsback impulsevia2 efferent pathways:-
 Fusimotor nervefibersor α efferent motor neurons
gammaefferent (for
extrafusal fibers) (for
intrafusal fibers)

2)2) GOLGI TENDON ORGANSGOLGI TENDON ORGANS--
 Located in muscletendon between musclefibersand their attachment to
bone.
 They aremoresensitivethan musclespindlesand activein reflex regulation
in normal function.
 They primarily monitor tension, whereasthemusclespindlesprimarily
monitor musclelength.
3)3) PACINIAN CORPUSCLESPACINIAN CORPUSCLES--
 Thepacinian corpusclesarelargeoval organsmadeup of concentric
lamellaeof connectivetissue. They arewidely distributed.
 They serveprincipally for theperception of themovementsand firm
pressure.
 Thesecorpusclesarefound in thetendons,joints,periosteum,tendinous
insertions,fasciaand sub cutaneoustissue.

4)4) NOCICEPTORS-
 They aresensory receptorsthat arestimulated by
injury & transmit injury information to CNSby
way of afferent nervefibers.
 Theprimary function isto monitor the
condition,position and movement of thetissuein
themasticatory system.

REFLEX ACTIONREFLEX ACTION:-:-
 2 general reflex actionsareimportant in themasticatory system :
1) MYOTACTIC REFLEX or stretch reflex-
 Istheonly monosynaptic jaw reflex.
 Sudden stretching of skeletal muscle

Afferent nerveactivity from thespindle

Trigeminal mesencephalic nucleus

Afferent fiber synapsein trigeminal motor nucleuswith
α- efferent motor neurons

Efferent fiberscarry information to extrafusal fibers

Musclecontractionwww.indiandentalacademy.comwww.indiandentalacademy.com

 Myotactic reflex isan important determinant
of rest position of thejaw.
 It isaprincipal determinant of muscletonus
in elevator muscles.

2)2) NOCICEPTIVE REFLEX or flexor reflexNOCICEPTIVE REFLEX or flexor reflex --
 Polysynaptic reflex to noxiousstimuli & hence, considered to beprotective.
 Sudden biting on hard object

Noxiousstimuli

Afferent nervescarry impulseto trigeminal spinal tract nucleuswherethey synapse
with interneurons

Excitatory interneuron's inhibitory interneuron's
Synapsewith efferent neurons Synapsewith efferent neurons
in thetrigeminal motor nucleus in thetrigeminal motor nucleus
they innervtethejaw depressing they innervatetheelevator muscles
Muscles
Messagesent isto contract, that messagesent isto discontinue
Bringstheteeth away contraction

INFLUENCE OF HIGHER CENTERS:-INFLUENCE OF HIGHER CENTERS:-
 Although thecortex isthemain determinant of action,the
brainstem isin chargeof maintaining homeostasisand
controlling normally subconsciousfunctions.
 Within brainstem, isapool of neuronsthat control rhythmic
muscleactivity such asbreathing, walking & chewing.
 Thispool of neuronsiscalled ‘Central Pattern Generator’
(CPG)
 It isresponsiblefor precisetiming of activity between
antagonistic musclesso that specific functionscan becarried
out.

CLASSIFICATION:-
I) According to Sharry:-
a) According to direction - Opening and closing movements
Protrusion and retraction
Lateral gliding movements
b) According to tooth contact - Movementswith tooth contact
Movementswithout tooth contact
c) Limitation by joint structure- Border movements
Intraborder movements
d) Functionsof masticatory system - Mastication
Deglutition
Speech
Respiration
e) CNS- Innatemovements– breathing & swallowing
Learned movements– speech and chewing

II)II) According to thetypeof movement occursin TMJ:-
a) Rotational
b) Translation
III) According to theplanesof border movements:-
a) Sagittal planeborder movement
b) Horizontal planeborder movements
c) Frontal planeborder movements

MANDIBULARMOVEMENTSMANDIBULARMOVEMENTS
 Mandibular movementsoccursascomplex seriesof 3
dimensional rotational and transitional activities. It is
determined by combined and simultaneousactivities
of both tmj’s.
 2 typesof movement occur in tmj:-
 Rotational
 Translational

ROTATIONALMOVEMENTROTATIONALMOVEMENT:-:-
Rotational movement of themandibleoccurs
in 3 different referenceplanes
1. Horizontal
2. Frontal
3. Sagittal

HORIZONTALAXIS OFROTATIONHORIZONTALAXIS OFROTATION:-:-
 An opening and closing motion-
hingemovement
 Only ‘pure’ rotational movement
in mandibular activity
 TERMINALHINGEAXIS
When the condyles are in their
most superior position in the
articular fossae and the mouth is
purely rotated open, the axis
around which movement occurs
is called the ‘Terminal Hinge
Axis’.

FRONTAL(VERTICAL) AXIS OFFRONTAL(VERTICAL) AXIS OF
ROTATIONROTATION:-:-
 Mandibular movement
around the frontal axis
occurs when one condyle
moves anteriorly out of
terminal hinge position with
the vertical axis of opposite
condyle remaining in the
terminal hingeposition.

SAGITTALAXIS OFROTATION:-SAGITTALAXIS OFROTATION:-

TRANSLATIONALMOVEMENT:-TRANSLATIONALMOVEMENT:-
 Translation can be defined as a
movement in which every point of
the moving object has
simultaneously the same velocity
and direction.
 It occurs within the superior cavity
of the joint, between the superior
surface of the articular disc and the
inferior surface of the articular
fossa.
 During normal movements of the
mandible both rotation and
translation occur simultaneously.
 This results in a very complex
movements.

SINGLE-PLANEBORDERMOVEMENTSSINGLE-PLANEBORDERMOVEMENTS:-:-
 Mandibular movementsarelimited by ligamentsand
articular surfaceof TMJ’saswell asthemorphology
and alignment of theteeth.
 When the mandible moves through the outer range of
motion, reproducible and describable limits result,
which arecalled BORDERMOVEMENTS.

SAGITTALPLANEBORDER&SAGITTALPLANEBORDER&
FUNCTIONALMOVEMENTS:-FUNCTIONALMOVEMENTS:-
They have 4 distinct movement components:-
1) Posterior opening border determined by ligaments &
the morphology of TMJ’s.
2) Anterior opening border
3) Superior contact border determined by occlusal &
incisal surfaces of teeth.
4) Functional determined by conditional responses
of neuromuscular system.

PosteriorOpening BorderPosteriorOpening Border
MovementsMovements:-:-
 Occursastwo stagehinging movements.
 1st
stage:-

 2nd
Stage:-
 Asthecondyletranslates
theaxisof rotation of the
mandibleshiftsinto the
bodiesof rami likely to be
theareaof attachment of
sphenomandibular
ligament, resulting in the
second stageof the
posterior opening border
movement.

Anterior Opening Border Movements:-Anterior Opening Border Movements:-
 With the mandible maximally opened, closure
accompanied by contraction of inferior lateral
pterygoids (which keep the condyles positioned
anteriorly) will generate the anterior border
movement.

 Becausethemaximum protrusiveposition is
determined in part by stylomandibular ligaments,
when closureoccurs, tightening of ligaments
producesaposterior movement of thecondyles.
 Theposterior movement of thecondylefrom the
maximally open position to maximally protruded
position produceseccentricity in theanterior border
movement. Therefore, it isnot apurehinge
movement.

Superior Contact BorderSuperior Contact Border
MovementsMovements:-:-
 Thismovement isdetermined bythecharacteristicsof
occluding surfacesof theteeth.through out themovement
tooth contact ispresent.
 It dependson:-
 Amount of variation between centric relation and
maximum intercuspation.
 Thesteepnessof thecuspal inclinesof theposterior teeth.
 Amount of vertical and horizontal overlap of anterior teeth
 Lingual morphology of maxillary anterior teeth.
 General interarch relationshipsof theteeth.

 In CENTRIC RELATION
-tooth contactsarenormally found on
oneor moreopposing pair of posterior
teeth.
-When muscular forceisapplied to the
mandible,
asuper anterior movement or
or shift will
occur until the
intercuspal position isreached.
-Theslidefrom CR to maximum
intercuspation, may havealateral
component.
-from early 1950’sto morerecently the
distancebetween MI and centric
relation haschanged from 1.25 mm by
Posselt,1.0mm by Schuyler, 0.8 to
0.5mm by Ramfjord,to 0.2mm by
Dawson and Ramfjord

 When themandibleisprotruded,
from maximum
intercuspation ….
 Thiscontinuesuntil the
maxillary
and mandibular
anterior teeth arein edge
to edgerelationship, at which
a
horizontal pathway isfollowed.
Horizontal movement www.indiandentalacademy.comwww.indiandentalacademy.com

Functional MovementsFunctional Movements:-:-
 Functional movement occursduring functional
activity of themandible. They usually takeplace
within theborder movements& therefore, considered
asfreemovements.
 Most functional movementsrequiremaximum
intercuspation & thereforetypically begin at & below
theintercuspal position.

 When mandible is at rest, it
is found to be located
approximately 2 to 4mm
below the intercuspal
position. This is called the
Clinical Rest Position.
 Postural position – Since,
clinical rest position is not a
true resting position, the
position in which mandible

 Chewing Stroke:- If it isexamined in sagittal plane, the
movement will beseen to begin at theintercuspal position &
drop downward & slightly forward to position of desired
opening. It then returnsin astraighter pathway, slightly
posterior to theopening movement.

 POSTURAL EFFECT ON FUNCTIONALPOSTURAL EFFECT ON FUNCTIONAL
MOVEMENT:MOVEMENT:
1. Head in erect and upright position
2. Head isdirected 45° upward (asassumed during drinking)
3. Head isdirected 30° (asassumed during eating) – ALERTFEEDING
POSITION

HORIZONTALPLANEBORDER&HORIZONTALPLANEBORDER&
FUNCTIONALMOVEMENTSFUNCTIONALMOVEMENTS:-:-
 When mandibular movementsareviewed in thehorizontal
plane, arhomboid-shaped pattern can beseen that hasa
functional component, & 4 distinct movement components:-
1) Left lateral border
2) Continued left lateral border
with protrusion
3) Right lateral border
4) Continued right lateral border
with protrusion

LEFT LATERAL BORDER MOVEMENTS:-
 With thecondylesin thecentric relation position, contraction of theright
inferior lateral pterygoid movetheright condyle- anteriorly and medially.
 If left inferior pterygoid staysrelaxed, with theleft condylestill in theCR &
result will beleft lateral border movement.
 Left condyle- working or rotatory
Right condyle- non-working or
orbiting

CONTINUEDLEFTLATERALBORDER
MOVEMENTS WITHPROTRUSION:-
 With themandiblein theleft lateral border position, contraction of the
left inferior lateral pterygoid along with continued contraction of right
inferior lateral pterygoid will causetheleft condyleto moveanteriorly to
theright.

RIGHT LATERAL BORDER MOVEMENTS:-RIGHT LATERAL BORDER MOVEMENTS:-
 Left condyle- orbiting
Right condyle- rotatory

CONTINUED RIGHT LATERAL BORDERCONTINUED RIGHT LATERAL BORDER
MOVEMENTSWITH PROTRUSION:-MOVEMENTSWITH PROTRUSION:-

FUNCTIONALFUNCTIONAL
MOVEMENTSMOVEMENTS:-:-
 As in the sagittal plane, functional
movement in the horizontal plane
most often occur near the
intercuspal position.
 During chewing the range of jaw
movements begins some distance
from maximum intercuspal
position; but as the food is broken
down into smaller particles, jaw
action moves closer and closer to
intercuspal position.

FRONTAL(VERTICAL) BORDER&
FUNCTIONALMOVEMENTS:-
 A shield-shaped pattern can beseen that hasafunctional
component, & four distinct movement components:-
1. Left lateral superior border.
2. Left lateral opening border.
3. Right lateral superior border.
4. Right lateral opening border.

Left Lateral Superior Border
Movements:-
 With themandiblein maximum intercuspation, lateral movement ismade
to theleft. It disclosesainferiorly concavepath being generated .
Thenatureof thispath
It dependsupon morphology and interarch relationshipsof maxillary and
mandibular teeth.
Themaximum lateral extent of thismovement isdetermined by ligamentsof the
rotating joint.

Left Lateral Opening Border
Movements:-
 From themaximum left lateral superior border position, an opening
movement of themandibleproducesalaterally convex path. Asmaximum
opening

Right Lateral Superior Border Movements:-

 Right Lateral Opening BorderRight Lateral Opening Border
Movements:-Movements:-

Functional MovementsFunctional Movements:-:-

ENVELOPEOFMOTION:-
 Given by POSSELT
 By combining mandibular border
movementsin all 3 planes, a3D
envelopeof motion isproduced.
 Thisrepresentsmaximum rangeof movement
of themandible.
 Thesuperior surfaceof theenvelop is
determined by tooth contactswhereasthe
other bordersareprimarily determined by
ligamentsand joint anatomy that limitsor
restrict movement

ECCENTRIC MANDIBULARECCENTRIC MANDIBULAR
MOVEMENTSMOVEMENTS
 Eccentric mandibular movement can be
divided into protrusiveand lateral movements
which consistsmainly of condylar translations.

 a)Sagittal ProtrusiveCondylar Path:-
Mandibletranslatesin forward and downward direction during protrusive
movement.
Theright and left musclesdo not makesimultaneousmovements. so pure
protrusivemovementsdo not exist in clinical situation
(Hobo,Mochizuki,1982)
1) PROTRUSIVEMOVEMENT:-

Theorbitsproduced by thecenter of theright and left
condyleduring protrusivemovement isreferred to as–
PROTRUSIVECONDYLARPATH
It formsan anglewith horizontal referenceplane
known asSagittalinclinatio n o f pro trusive co ndylar
path.
 Rangesfrom 5º- 55º. (with FH planeashorizontal ref.)
Mean 30.4º.
(Hobo,Mochizuki,1982)
 33º when campersplaneisused(Gysi,kohler,1929)

b)b) Sagittal ProtrusiveIncisal Path:-Sagittal ProtrusiveIncisal Path:-
Theorbit of incisal point from maximum intercuspation to edge-to-edge
occlusion –PROTRUSIVE INCISAL PATH
Themean length of thepath is5 mm
Angleformed by protrusiveincisal path and horizontal referenceplane–
“SAGITTAL INCLINATIONOF PROTRUSIVE INCISAL PATH” (incisal
guidanceangle)
 rangebetween 50-70 degrees. (Gysi,Kohler,1929)
Usuallysagittalinclinationof
protrusiveincisalpathis steeper
thansagittalinclinationof
protrusivecondylarpath.
(Hobo,1978)

2)LATERALMOVEMENT:-2)LATERALMOVEMENT:-
 Lateral movements are complex activities in
most humans
 Lateral movement from occlusal position and
back again are assymetric.The right and left
condyle carry out different movements.
 Thus lateral movements:
 Sagittal plane
 Horizontal plane

LATERALMOVEMENTS IN SAGITTALPLANELATERALMOVEMENTS IN SAGITTALPLANE
Sagittal Lateral CondylarPath:-
 When lateral movement isexecuted theworking condylerotates
& movesoutward, whilethenon working condyletranslates
forward, medially downward orbiting around therotating
working condyle.
 When theorbit of nonworking
condyleistraced in thesagittal
planeit isknown asSagittal
lateralco ndylar path.
 Lateral condylar path islonger
& moresteep than theprotrusive
condylar path.

 FISCHERANGLE:- Theangleformed between thesagittal
protrusivecondylar path & sagittal lateral condylar path
(approx 5º).
 Theangleformed by thesagittal lateral condylar path &
horizontal referenceplaneisknown as“SagittalInclinatio n
Of LateralCo ndylar Path”
 Anglebetween sagittal lateral condylar path and FH plane
isapprox 45-50° (Lundeen,Wirth,1973))

Lateral movement in horizontal
plane
 Working sidelateral movement
 Nonworking sidelateral movement

Working sidelateral movement
 Sir Normal Godfery Bennett(1908) studied working condylar path and called it
BENNETT MOVEMENT, now referred to asLATEROTRUSION.
 Bennett showed that working condylemovesoutwardsand nonworking condyle
movesinwards.
 Although Bennett hasdescribed about themovement which becamepopularly known
asBennett movement ,theoriginal discovery of thismovement should go to
BALKWILL,who described thesamesideshift in 1866.
 Bennettmovementrefersto theCONDYLARMOVEMENTon theworking side, were
theworking condylerotatesand movesslightly outwards.
Thisoutward direction of bennett path (laterotrusion) may becombined with an
 Upward (laterosurtrusion)
 Downward (laterudetrusion)
 Forward (lateroprotrusion), or
 Backward (lateroretrusion) component
 Bennettsideshiftisthe bodily sideshift of the MANDIBLEon theworking sidein the
horizontal plane. (MandibularLateralTranslation)

 When themandibleismoved laterally to theworking
side,it rotateson thevertical axispassing through the
center of theworking condyle.
 Besidesrotation around thevertical axistheworking
condylemust movelaterally (Bennett movement) to
accommodatethemedial movement of theorbiting
nonworking condyle.
 Thereforethesideshift of theworking condyleisThereforethesideshift of theworking condyleis
dependent and isconsequent to themedial movementdependent and isconsequent to themedial movement
of theorbiting condylar pathof theorbiting condylar path

Nonworking sidelateral movement
 During lateral movement the working condyle rotates
and moves outwards and the nonworking condyle moves
medially and advances in a forward and downward
direction.When this path of nonworking condyle is traced
on horizontal plane it is known as the HORIZONTALHORIZONTAL
LATERAL CONDYLAR PATHLATERAL CONDYLAR PATH
 It has 2 components:
 Immediate mandibular lateral translation
 Progressive mandibular lateral translation

 Immediate mandibular lateral translationImmediate mandibular lateral translation
Occurswhen thenonworking condylemovesfrom thecentric relation straight
inward or medially,
 to adistanceof approx 1.0mm (Lundeen,Wirth,1973)
 0-2.6mm (mean-0.42mm) (Hobo,Mochizuki,1982),asrecorded using a
electronic mandibular recording device
Beyond thisthecondylemovesforward, downward & inward
 Progressivemandibular lateral translationProgressivemandibular lateral translation
 It is the translatory portion of the lateral movement that occur at a rate
proportional to forward movement of non working condyle.(GPT 1987)
 the value of progressive mandibular lateral translation is 7.5°
(Lundeen,Wirth,1973)
 Angleformedbythehorizontalcondylarpathandsagittalplanevaries
between2º -44º (mean16º)andis calledas BENNETTANGLE

Bennett movement has 3 components:-
 Amount
 Timing
 Direction
 AMOUNT
 The amount of medial movement of the orbiting condyle governs the
magnitudeof lateral shift of themandible(Bennett shift)
 IMMEDIATE SIDE SHIFT is the bodily shift of the condyle in
horizontal plane. this is regulated by the shape of the glenoid
fossa,looseness of the capsular ligaments and contraction of the lateral
pterygoids.
 amean movement of 1.0 mm (Lundeen,Wirth,1973)
 Beyond this the condyle moves forward, downward & inward, this is
known as‘ PROGRESSIVE SIDE SHIFT.’
 Combined amount of (ISS+PSS) is the Bennett angle, with a mean
valueof 16°

2) TIMING:-
 Therateor amount of descent of contralateral
condyle& therotation & lateral shift of ipsilateral
condyle.
 Immediatesideshift –
isthe1st
movement themandiblemakeswhen
initiating lateral excursions.
 Progressivesideshift:-
Beyond theimmediatesideshift thecondylesmove
forward, downward and inward.

3)3) DIRECTION:-DIRECTION:-
 Thedirection of Bennett movement dependsprimarily
on thedirection taken by therotating condyleduring the
bodily movement. Thedirection of theshift of the
rotating condyleduring Bennett movement isdetermined
by theTM joint undergoing rotation.

 Lundeen T.F. & MendozaF.(1984) – conducted astudy on
comparison of Bennett shift measured at thehingeaxis&
arbitrary hingeaxisposition. In their study they used flag
system & afacebow system. They modified thefacebow by
substitution of aHingeAxisLocator. Theend of HingeAxis
Locator wasmodified with aplastic fitting to facilitatethe
attachment of measuring pointer.
 They concluded that therewasno significant differencein the
Bennett shift measurementsmadeat thehingeaxis& the
arbitrary hingeaxispositionswhen measured in 0.25mm
increments. TheaverageimmediateBennett shift was1.05mm
on theleft side& 1.12mm on theright sidewhen firm
guidancewasused.

LATERALINCISALPATH:-
Theorbit produced by incisal point during lateral
movementisreferred to asthelateral incisal path.
When thepath istraced on ahorizontal planeit is
called theGOTHIC ARCH tracing.
Theangleproduced by right and left horizontal
incisal path iscalled thegothic arch angle.
Mean value- 120°

 Lundeen.H.C, Shryock.E.F, Gibbs.C.H-Lundeen.H.C, Shryock.E.F, Gibbs.C.H-
 in thisstudy mandibular border movementswereanalyzed to determinethe
averagemovement pathway. Thesecond part of thestudy involved molar
cusp movement analysisutilizing border movement pathway with variation
in anterior guidance.
 From thestudy they concluded that
- aBennett movement of 2.5 to 3.5mm caused adramatic flattening of lateral
movement pathwaysof themolar cusp asseen in frontal plane.
-viewed in thehorizontal plane,excessiveBennett movement contributed to
thegreatest potential of collision of molar cuspsduring lateral movements.
thisphenomenon wasmorepronounced on thenonworking side.
- when Bennett movement was0.75mm and lessthetracing in thefrontal
planeshowed that 40° anterior guidancebecamethedominant influence
over molar cusp lateral movement pathway.

 PRACTICAL SIGNIFICANCE:PRACTICAL SIGNIFICANCE:
1. Patients with excessive Bennett movement and little or no anterior
guidance present the greatest challenge in occlusal rehabilitation
procedures because the cusp movement pathways of there posterior
teeth are very shallow.
The elimination of eccentric cusp interference can be very difficult. in this
study it was shown that increase in anterior guidance to 40° produced
only a slight change in the lateral pathways in presence of a 3.5mm
Bennett movement. The completely adjustable articulator would be most
helpful for such patients.
2. Patients with very little Bennett movenent,0.75mm or less ,have molar
cusp movement pathways that reflect the steepness of the anterior
guidance and the non working condylar pathways. The potential for
eccentric cusp interference is markedly reduced due to the steep
immediate cusp separation seen close to the intercuspal position
3. A condylar movement screening device that would quickly and simply
determine a patients approx bennett movement and the inclination of the
nonworking condylar pathway would provide useful diagnosis and
treatment information.www.indiandentalacademy.comwww.indiandentalacademy.com

MAJOR FUNCTIONSOF
MASTICATORY SYSTEM
 MASTICATION:-
 It istheact of chewing food. It representstheinitial stagesof
digestion…
 CHEWING STROKE:
 Mastication ismadeup of rhythmic & well controlled separation &
closureof themaxillary & mandibular teeth.
 Thisactivity isunder control of CPG,located in thebrainstem.
 In frontal plane, it hasa‘tear shaped’ pattern.

 It can bedivided into
 a) Opening Phase
 b) Closing Phase–
i) Crushing Phase
ii) Grinding Phase.
 When themandibleistraced in
thefrontal planefollowing
sequenceoccurs-

 If themovement of amandibular incisor isfollowed in the SAGITTALSAGITTAL
PLANEPLANE during atypical chewing stroke, it will beseen that during the
opening phasethemandiblemovesslightly anteriorly.
Working side Nonworking side

TOOTH CONTACT DURING MASTICATION:TOOTH CONTACT DURING MASTICATION:
 When food isinitially introduced in themouth,fewer contacts
occur.
 Asbolousisbroken down frequency of contactsincrease.
 2 typesof contacts:
-gliding contacts
-singlecontacts

SWALLOWING (DEGLUTITION):-SWALLOWING (DEGLUTITION):-
 It isaseriesof co-coordinated muscular contractionsthat movesa
bolusof food from theoral cavity through theesophagusto the
stomach.
 It consistsof voluntary, involuntary and reflex muscular activity.
 Stabilization of themandibleisan important part of swallowing.
 Themandiblemust befixed so contraction of suprahyoid &
infrahyoid musclescan control proper movement of thehyoid bone
needed for swallowing.
a) Somatic swallow –
b) Visceral swallow –
 It isbelieved that when themandibleisbraced it isbrought into most
retruded position.
 But according to Okeson thequality of intercuspal position will
determinetheposition of themandibleduring swallowing and not a
retruded relationship with thefossa.www.indiandentalacademy.comwww.indiandentalacademy.com

Parafunctional movementsParafunctional movements
 May bedescribed assustained activitiesthat occur beyond the
normal mastication and speech.
 It ismanifested by long periodsof musclecontraction and
hyperactivity
 Excessiveocclusal pressureand prolonged tooth contact
occur,which isinconsistent with normal chewing cycle.
Two most common formsof parafunctional activitiesare
bruxism
clenching

METHODSUSED FORMETHODSUSED FOR
RECORDING MANDIBULARRECORDING MANDIBULAR
MOVEMENTSMOVEMENTS
 Graphic method record –
 It traces mandibular movements in one
plane.
 An arrow point tracing.
 Indicates horizontal relation of mandible to
maxilla.
 Can be either intra-oral or extra-oral.
 Intra-oral is small, so difficult to find true
apex.

 STEREOGRAPHICS:-
 (Swenson. 1966; Mensor. 1973)
 PANTOGRAPHS:-
 REPLICATOR:-
 By Messerman 1964).
 KINESIOGRAPH:-
 Jankelson et al(1975).

CLINICAL SIGNIFICANCE
 A prosthodontist hasto aim to reproduceaccurate
mandibular movementswhich allow usto facricate
restorationsand prosthesesin harmony with the
patientsnatural function. Knowledgeof the
mandibular movementsessential, it helpsthedentist
in:
- Selecting and programming of articulators
- Treating TMJdisturbances.
- Arranging artificial teeth.
- Development of occlusal scheme.

Conceptsof occlusion differ depending upon whether restoration arefixed
or removable.thedentist must havetheknowledgeof theeffect of guiding
factorsof themandible
CONDYLARGUIDANCE
Isoneof thetwo end controlling factorsnot under thecontrol of the
dentist.
It isdetermined by theshapeof thearticular eminence, anatomy of the
medial wall of mandibular fossa,and configuration of mandibular condyle
 Effects o f co ndylar guidance o n cusp height
a) Thelesser thecondylar guidanceangle, theshorter thecusps
must be.
b) Thegreater thecondylar guidanceangle, thelonger thecusps
may be

ANTERIORGUIDANCE
The anterior determinants are the vertical and horizontal overlaps
and lingual concavities on maxillary anterior teeth.
These can be altered by restorative and orthodontic treatment.
 Effects of anterior guidance on cusp height
The greater the horizontal overlap of the maxillary anterior
teeth, the shorter the cusps of the posterior teeth must be.
The lesser the horizontal overlap the longer the cusps of the
posterior teeth may be
The lesser the vertical overlap, the shorter the cusps of the
posterior teeth must be.
The greater the vertical overlap, the longer the posterior cusps
may be.

 Bennett’s Movement:-
Movement responsiblefor lateral chewing stroke.
    - Movement during which the greater lateral force is
exerted.
    - It is extremely important that articulating surfaces
areisstrict harmony with thissideshift.

Effect o n cusp height:
      - Greater the side shift of the mandible shorter the
cuspsmust be.
   - The lesser the side shift of the mandible longer
thecuspsmay be.

SummarySummary

ConclusionConclusion
““nature has blessed us with a marvelously
dynamic masticatory system, allowing us to
function and therefore exist””
Onehasaimed to reproduceaccuratemandibular movements,
which allow usto fabricaterestorationsand prosthesesin
harmony with thepatient’snatural function.

REFERENCESREFERENCES
AgAgur A.M.R. & Dalley A.F. – ‘Grant’sAtlasof Anatomy’
11th
Edition, 2005
Colaizzi F.A., Micheal C.G., Javid N.S.& GibbsC.H.- ‘Condylar &
incisal border movements: A comparativestudy of completedenture
wearers& natural dentition subjects’JPD1988; 59(4),453-459.
Hobo,IchidaE. & GarciaL.T. – ‘Osseointegration & Occlusal
Rehabilitation’
Lundeen H.C.,Shryick,E.F & GibbsC.H.-An evaluation of mandibular
border movements:their charectar and significance’.JPD1978;40(4),442-4
Lundeen H.C. & GibbsC.H. – ‘Advancesin Occlusion’ 1982
Lundeen T.F. & MendozaF. – ‘Comparison of Bennett shift measured at
thehingeaxis& an arbitrary hingeaxisposition’JPD1984; 51(3), 407-
410.

Okeson J.P. – ‘Management of temporomandibular disorders&
occlusion’ 5th
edi. 2003
Sharry J.J. – ‘Completedentureprosthodontics’ 1962
Salomon J.A., Waysenson B.D. & Warshaw B.D. – ‘Computer-monitored
radionuclidetracking of three-dimensional mandibular movements. Part II:
Experimental setup & preliminary results- Posselt Diagram’
JPD1979;41(4), 463-469.
Thompson H. – ‘Occlusion’ 2nd
edi. 1990
Woelfel J.B., Hickey J.C., Stacy R.W. & Rinear L. – ‘Electromyographic
analysisof jaw movements’ JPD1960;10(4),688-697.

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