Occlusion concepts part 1 / dental courses

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CONTENTSCONTENTS
 CONCEPTS OF OCCLUSIONCONCEPTS OF OCCLUSION
 DEFINITIONDEFINITION
 IDEAL OCCLUSIONIDEAL OCCLUSION
 TOOTH ALIGNMENTSTOOTH ALIGNMENTS
 TYPES OF CUSPS AND CONTACTSTYPES OF CUSPS AND CONTACTS
 CENTRIC RELATION Vs CENTRIC OCCLUSIONCENTRIC RELATION Vs CENTRIC OCCLUSION
 OCCLUSAL RELATIONSHIPSOCCLUSAL RELATIONSHIPS
 MANDIBULAR MOVEMENTSMANDIBULAR MOVEMENTS
 MANDIBULAR MOVEMENTS AND OCCLUSAL MORPHOLOGYMANDIBULAR MOVEMENTS AND OCCLUSAL MORPHOLOGY
 ENVELOPE OF MOTIONENVELOPE OF MOTION
 BIBLIOGRAPHYBIBLIOGRAPHY

CONCEPTS OF OCCLUSIONCONCEPTS OF OCCLUSION
 Edward .H. Angle (1899) :defined occlusion asEdward .H. Angle (1899) :defined occlusion as
“the normal relationship of the occlusal inclined“the normal relationship of the occlusal inclined
planes of the teeth when the jaws are closed”planes of the teeth when the jaws are closed”
 Two main concepts of occlusion:Two main concepts of occlusion:
Prosthetic conceptProsthetic concept
Orthodontic conceptsOrthodontic concepts
 Prosthetic concept: functional stability isProsthetic concept: functional stability is
enhanced with bilateral tooth contacts and lateralenhanced with bilateral tooth contacts and lateral
and protrusive excrusionsand protrusive excrusions
 Orthodontically oriented is that certainOrthodontically oriented is that certain
acceptable static cusp-fossa relationships areacceptable static cusp-fossa relationships are
emphasized.emphasized.

 From last 2-3 decades third concept of a dynamicFrom last 2-3 decades third concept of a dynamic
individual occlusion has emerged where in theindividual occlusion has emerged where in the
criteria for diagnosis of occlusion and need forcriteria for diagnosis of occlusion and need for
treatment have been based upon an evaluation oftreatment have been based upon an evaluation of
the health and function of each individualthe health and function of each individual
masticatory systemmasticatory system
 The concept of multifactorial functionalThe concept of multifactorial functional
relationship between the teeth and the otherrelationship between the teeth and the other
components of the masticatory system as well ascomponents of the masticatory system as well as
with other areas of the head and neck thatwith other areas of the head and neck that
directly or indirectly relate to the function,directly or indirectly relate to the function,
parafunction, or dysfunction of the masticatoryparafunction, or dysfunction of the masticatory
system. (M.M. Ash & S. Ramfjord)system. (M.M. Ash & S. Ramfjord)

 The term “occlusion” as used in dentistry mayThe term “occlusion” as used in dentistry may
mean the contact relationship of the teeth inmean the contact relationship of the teeth in
function and parafunction. However, the termfunction and parafunction. However, the term
refers not only to contact of the arches at therefers not only to contact of the arches at the
occlusal interface but also to all those factorsocclusal interface but also to all those factors
concerned with development and stability of theconcerned with development and stability of the
masticatory system and with the use of teeth inmasticatory system and with the use of teeth in
the oral motor behaviour. Thus modern conceptthe oral motor behaviour. Thus modern concept
of occlusion must include the idea of anof occlusion must include the idea of an
integrated system of functional units involvingintegrated system of functional units involving
teeth, joints, and muscles of the head and neckteeth, joints, and muscles of the head and neck..
(Wheeler’s)(Wheeler’s)

 Normal occlusionNormal occlusion: based on neuromuscular: based on neuromuscular
rather than a morphological evaluationrather than a morphological evaluation
 It involves occlusal contacts alignment of teeth,It involves occlusal contacts alignment of teeth,
overbite and overjet, arrangement andoverbite and overjet, arrangement and
relationship of teeth within and between therelationship of teeth within and between the
arches and relationship of the teeth to thearches and relationship of the teeth to the
osseous structuresosseous structures
 It emphasizes on the functional aspect ofIt emphasizes on the functional aspect of
occlusion and the capability of the masticatoryocclusion and the capability of the masticatory
system to adapt or compensate for somesystem to adapt or compensate for some
deviations with in the range of tolerance of thedeviations with in the range of tolerance of the
system.system.
 Neuromuscular mechanism has adaptation toNeuromuscular mechanism has adaptation to
imperfections in relationship among the variousimperfections in relationship among the various
factors aligning the masticatory systemfactors aligning the masticatory system

DefinitionsDefinitions
 OcclusionOcclusion: the relationship of the maxillary and: the relationship of the maxillary and
mandibular teeth as they are brought intomandibular teeth as they are brought into
functional contact.functional contact.
 Ideal occlusion(GOT)Ideal occlusion(GOT): (optimal occlusion) an: (optimal occlusion) an
ideal relationship of the maxillary and theideal relationship of the maxillary and the
mandibular teeth combining a functionalmandibular teeth combining a functional
occlusion with the absence of malocclusionocclusion with the absence of malocclusion
 Functional occlusion(GOT)Functional occlusion(GOT): (physiologic: (physiologic
occlusion)occlusion)
 A state and dynamic relationship of the teethA state and dynamic relationship of the teeth
combining minimum stress on thecombining minimum stress on the
temporomandibular joint, optimal function of thetemporomandibular joint, optimal function of the
orofacial complex, stability esthetics of theorofacial complex, stability esthetics of the
dentition and protection and the health ofdentition and protection and the health of
periodontiumperiodontium www.indiandentalacademy.comwww.indiandentalacademy.com

 Balanced occlusion (GOT)Balanced occlusion (GOT): an occlusion in which: an occlusion in which
balanced and equal contacts are maintainedbalanced and equal contacts are maintained
throughout the entire arch during all excrusions ofthroughout the entire arch during all excrusions of
mandible.mandible.
 Traumatic occlusion(GOT)Traumatic occlusion(GOT): (occlusal: (occlusal
trauma,periodontal trauma) injury to periodontiumtrauma,periodontal trauma) injury to periodontium
resulting from occlusal forces in excess of theresulting from occlusal forces in excess of the
reparative capacity of the peridontal attachment.reparative capacity of the peridontal attachment.
The affected teeth usually exhibit widening of theThe affected teeth usually exhibit widening of the
pdl space, wear facets and some degree ofpdl space, wear facets and some degree of
hypermobility.hypermobility.
 Centric occlusion(GOT)Centric occlusion(GOT): it is the occlusion of: it is the occlusion of
opposing teeth when the mandible is in centricopposing teeth when the mandible is in centric
relation, this may or may not coincide with therelation, this may or may not coincide with the
maximal intercuspal position, also known asmaximal intercuspal position, also known as
maximal intercuspal position, habitual occlusion ormaximal intercuspal position, habitual occlusion or
acquired occlusionacquired occlusion

Ideal occlusionIdeal occlusion
 It is a state in which no (or minimal)It is a state in which no (or minimal)
neuromuscular adaptation is needed because noneuromuscular adaptation is needed because no
occlusal interferences are present.occlusal interferences are present.
 It indicates a complete harmonious relationship ofIt indicates a complete harmonious relationship of
the masticatory system for mastication as well asthe masticatory system for mastication as well as
for swallowing and speech.for swallowing and speech.
 Neuromuscular harmonyNeuromuscular harmony: there are certain: there are certain
requirments regarding the relationship betweenrequirments regarding the relationship between
TMJ guidance and occlusal guidance whichTMJ guidance and occlusal guidance which
assures such harmony.assures such harmony.
 Stable jaw relationship is required when teethStable jaw relationship is required when teeth
make contact in centric relationmake contact in centric relation

 Centric occlusion must be slightly infront ofCentric occlusion must be slightly infront of
centric relation and must be in the same sagittalcentric relation and must be in the same sagittal
plane as the path made by the mandible inplane as the path made by the mandible in
straight protrusive movement between centricstraight protrusive movement between centric
relation and centric occlusionrelation and centric occlusion
 Unrestricted glide with maintained occlusalUnrestricted glide with maintained occlusal
contacts between centric relation and centriccontacts between centric relation and centric
occlusionocclusion
 Various excrusions, both from CO and CR needVarious excrusions, both from CO and CR need
complete freedom for smooth gliding occlusalcomplete freedom for smooth gliding occlusal
contact movementscontact movements
 Occlusal guidance in various excrusions must beOcclusal guidance in various excrusions must be
on working side rather than on balancing side,on working side rather than on balancing side,

steepness of incisal or cuspal guidance is notsteepness of incisal or cuspal guidance is not
important for neuromuscular harmonyimportant for neuromuscular harmony
 Functional stabilityFunctional stability: stable occlusal relationship: stable occlusal relationship
refers to self-perpetuating, stable andrefers to self-perpetuating, stable and
harmonious relationship between teeth and TMJharmonious relationship between teeth and TMJ
throughout lifethroughout life
 Impact of full intercuspation closure must be inImpact of full intercuspation closure must be in
the long axis of all posterior teeth and against thethe long axis of all posterior teeth and against the
central part of meniscus of TMJcentral part of meniscus of TMJ
 Even degree of wear resistance must be present,Even degree of wear resistance must be present,
cutting efficiency of all functionally alike teethcutting efficiency of all functionally alike teeth
should be the sameshould be the same
 No displacing impact may be present on anteriorNo displacing impact may be present on anterior
teeth in centric occlusion closureteeth in centric occlusion closure

 No soft tissue contact in functional occlusionNo soft tissue contact in functional occlusion
 Acceptable interocclusal space presentAcceptable interocclusal space present
 NORMAL VERSUS IDEALNORMAL VERSUS IDEAL
OCCLUSION:OCCLUSION:
 eg: the forward slide from centric relation toeg: the forward slide from centric relation to
centric occlusion of 1-2 mm is normal since suchcentric occlusion of 1-2 mm is normal since such
a slide is found commonly without disturbance toa slide is found commonly without disturbance to
any part of the masticatory system when otherany part of the masticatory system when other
aspects of occlusion also are within the range ofaspects of occlusion also are within the range of
normal functionnormal function
 Similarly occlusion is considered normal in theSimilarly occlusion is considered normal in the

presence of occlusal interferences in lateralpresence of occlusal interferences in lateral
excrusions provided interferences are bypassedexcrusions provided interferences are bypassed
by neuromuscular adaptation and there are noby neuromuscular adaptation and there are no
clinically apparent disturbances of masticatoryclinically apparent disturbances of masticatory
function or pathological periodontal changesfunction or pathological periodontal changes
 Occlusion cant be considered ideal if even minuteOcclusion cant be considered ideal if even minute
occlusal interferences cannot be bypassed byocclusal interferences cannot be bypassed by
neuromuscular adaptationneuromuscular adaptation
 Ideal occlusion has less relation to anatomicalIdeal occlusion has less relation to anatomical
features than to functional characteristicsfeatures than to functional characteristics

Tooth alignmentsTooth alignments
 Intra arch tooth alignmentIntra arch tooth alignment
 Inter arch tooth alignmentInter arch tooth alignment
 Intra arch tooth alignmentIntra arch tooth alignment:: this refers to thethis refers to the
relationship of teeth to each other within therelationship of teeth to each other within the
dental archdental arch
 Plane of occlusionPlane of occlusion: is an imaginary plane: is an imaginary plane
containing the incisal edges of the mandibularcontaining the incisal edges of the mandibular
central incisors and the tip of the distobuccal cuspcentral incisors and the tip of the distobuccal cusp
of the 2of the 2ndnd
mandibular molarmandibular molar
 The plane of occlusion is not flat an curved in aThe plane of occlusion is not flat an curved in a

manner that permits maximum use of toothmanner that permits maximum use of tooth
contacts during functioncontacts during function
 Curvature of the occlusal plane is due to theCurvature of the occlusal plane is due to the
teeth that are positioned in arches at varyingteeth that are positioned in arches at varying
degreesdegrees
 When viewed laterally: In mandibular arch bothWhen viewed laterally: In mandibular arch both
anterior and posterior teeth are mesially inclinedanterior and posterior teeth are mesially inclined
 In maxillary arch different patterns of inclinationIn maxillary arch different patterns of inclination
existsexists
 Anteriors- mesially inclined and Posteriors-Anteriors- mesially inclined and Posteriors-
distally inclineddistally inclined
 When viewed in frontal plane: in maxilla all theWhen viewed in frontal plane: in maxilla all the
posterior teeth are slightly buccally inclinedposterior teeth are slightly buccally inclined
whereas in mandible all the posterior teeth arewhereas in mandible all the posterior teeth are
slightly lingually inclined.slightly lingually inclined.

 curve of speecurve of spee:: is determined by the occlusalis determined by the occlusal
surfaces of teeth following the cusp tips of thesurfaces of teeth following the cusp tips of the
anterior mandibular teeth to the buccal cusp tipsanterior mandibular teeth to the buccal cusp tips
of the posterior mandibular teeth (called asof the posterior mandibular teeth (called as
compensating curve for dentures)compensating curve for dentures)

 Curve of wilsonCurve of wilson : is: is
determined by the linedetermined by the line
drawn through thedrawn through the
buccal and lingualbuccal and lingual
cusp tips of both thecusp tips of both the
right and left posteriorright and left posterior
teeth, curved plane ofteeth, curved plane of
occlusion is obserevedocclusion is obsereved
from frontal view, thisfrom frontal view, this
is called as curve ofis called as curve of
wilsonwilson
 Convex in theConvex in the
maxillary arch,maxillary arch,
concave in theconcave in the
mandibular archmandibular arch

 Extending the curve ofExtending the curve of
spee and curve ofspee and curve of
wilson to all cusps tipswilson to all cusps tips
and incisal edgesand incisal edges
reveals thereveals the curve ofcurve of
monsonmonson
 Monson (1932): usedMonson (1932): used
bonwill triangle andbonwill triangle and
proposed a theoryproposed a theory
that a sphere existedthat a sphere existed
with a radius of 4with a radius of 4
inches with a centreinches with a centre
equidistance fromequidistance from
occlusal surfaces ofocclusal surfaces of
posterior teeth andposterior teeth and
from centre offrom centre of
condylescondyles

 Inter arch tooth alignmentInter arch tooth alignment:: this refers to thethis refers to the
relationship of the teeth in one arch to those inrelationship of the teeth in one arch to those in
the otherthe other
 When two arches come in contact as in theWhen two arches come in contact as in the
mandibular closure the occlusal relationship ofmandibular closure the occlusal relationship of
teeth is estaiblishedteeth is estaiblished
 The distance of a line that begins at the distalThe distance of a line that begins at the distal
surfaces of the 3surfaces of the 3rdrd
molar, extends mesiallymolar, extends mesially
through all of the proximal contact areas aroundthrough all of the proximal contact areas around
the entire arch and ends at the distal surface ofthe entire arch and ends at the distal surface of
the opposite 3the opposite 3rdrd
molar, this represents the archmolar, this represents the arch
lengthlength

 (Approx) maxillary arch- 128 mm(Approx) maxillary arch- 128 mm
 mandibular arch- 126 mmmandibular arch- 126 mm
 Arch width is the distance across the arch,Arch width is the distance across the arch,
mandibular arch is slightly less then that of themandibular arch is slightly less then that of the
maxillary archmaxillary arch
 In normal occlusal relationship maxillary teeth areIn normal occlusal relationship maxillary teeth are
more facially positioned ,in posterior teethmore facially positioned ,in posterior teeth
mandibular buccal cusps occlude along themandibular buccal cusps occlude along the
central fossa areas of the maxillary teeth and thecentral fossa areas of the maxillary teeth and the
maxillary lingual cusps occlude along the centralmaxillary lingual cusps occlude along the central
fossa areas of the mandibular teethfossa areas of the mandibular teeth
 The normal buccolingual relationship helpsThe normal buccolingual relationship helps
maximize the efficiency of the musculature whilemaximize the efficiency of the musculature while
minimizing any trauma to the soft tissueminimizing any trauma to the soft tissue

Normal intercuspation of maxillary and mandibular teeth:Normal intercuspation of maxillary and mandibular teeth:

Line ofLine of occlusionocclusion: Angle: Angle
referred to the line ofreferred to the line of
occlusion as “the line ofocclusion as “the line of
greatest normal occlusalgreatest normal occlusal
contact”contact”
 He defined it as being theHe defined it as being the
line with which, in formline with which, in form
and position according toand position according to
the type, the teeth mustthe type, the teeth must
be in harmony, if in normalbe in harmony, if in normal
occlusion.occlusion.
 Line of occlusion is aLine of occlusion is a
smooth continuoussmooth continuous
symmetric curvesymmetric curve
 Line of occlusion passesLine of occlusion passes
through the central fossathrough the central fossa
and along the cingula ofand along the cingula of
the maxillary teeth butthe maxillary teeth but
through the buccal cuspsthrough the buccal cusps
and incisal edges of theand incisal edges of the
mandibular teethmandibular teeth

Types of cuspsTypes of cusps
 Supporting or centric cuspsSupporting or centric cusps
 Guiding or non centric cuspGuiding or non centric cusp
 Supporting cusps (centric cusp):Supporting cusps (centric cusp): the buccalthe buccal
cusp of the mandibular posterior teeth and thecusp of the mandibular posterior teeth and the
lingual cusp of the maxillary teeth occludes withlingual cusp of the maxillary teeth occludes with
the opposing central fossae areas.the opposing central fossae areas.
 They are primarily responsible for maintaining theThey are primarily responsible for maintaining the
distance between the maxilla and mandibledistance between the maxilla and mandible
 This distance supports the vertical facial heightThis distance supports the vertical facial height
and is called as vertical dimension of occlusion.and is called as vertical dimension of occlusion.

 Centric cusps are broad and roundedCentric cusps are broad and rounded
 When viewed from occlusal, their tips are locatedWhen viewed from occlusal, their tips are located
approx 1/3approx 1/3rdrd
distance into the total buccolingualdistance into the total buccolingual
width of the toothwidth of the tooth
 Guiding cusp (non-centric cusp):Guiding cusp (non-centric cusp): the buccalthe buccal
cusp of the maxillary posterior teeth and thecusp of the maxillary posterior teeth and the
lingual cusp of the mandibular teethlingual cusp of the mandibular teeth
 These are relatively sharp with definite tips thatThese are relatively sharp with definite tips that
are located approx 1/6are located approx 1/6thth
the distance into the totalthe distance into the total
buccolingual width of the toothbuccolingual width of the tooth
 A small area of the non centric cusp haveA small area of the non centric cusp have
functional significance – it is located on the innerfunctional significance – it is located on the inner
inclines of the non centric cusp near the centralinclines of the non centric cusp near the central

 Fossa of the tooth and either contacts with/or isFossa of the tooth and either contacts with/or is
in close to a small portion of the outer aspect ofin close to a small portion of the outer aspect of
the opposing centric cuspthe opposing centric cusp
 This area assists in shearing of food duringThis area assists in shearing of food during
mastication hence the non centric cusps havemastication hence the non centric cusps have
also been called the shearing cuspsalso been called the shearing cusps
 They also give mandible stability so that whenThey also give mandible stability so that when
the teeth are in full occlusion, definite occlusalthe teeth are in full occlusion, definite occlusal
relationship results, also helps in guiding therelationship results, also helps in guiding the
mandible during opening and closing movementmandible during opening and closing movement

 CentricCentric
Cusps orCusps or
SupportingSupporting
cuspscusps
 Non centricNon centric
Or guidingOr guiding
cuspscusps

Centric occlusion Vs centric relationCentric occlusion Vs centric relation
 If Centric occlusion coincides with the centricIf Centric occlusion coincides with the centric
relation they appear to be the same.relation they appear to be the same.
 Centric relation is bone to bone relation whileCentric relation is bone to bone relation while
centric occlusion is tooth to tooth relation.centric occlusion is tooth to tooth relation.
 Centric occlusion does not coincide with theCentric occlusion does not coincide with the
centric relation in most of the people with naturalcentric relation in most of the people with natural
teeth.teeth.
 Centric relationCentric relation: it is the maxillo-mandibular: it is the maxillo-mandibular
relationship in which the condyles articulate withrelationship in which the condyles articulate with
the thinnest avascular portion of their respectivethe thinnest avascular portion of their respective
disks with the complex in the anterior superiordisks with the complex in the anterior superior
position against the shapes of the articularposition against the shapes of the articular
eminences, the position is independent of theeminences, the position is independent of the
tooth contact. (GPT-5)tooth contact. (GPT-5)

 Centric occlusionCentric occlusion: it: it
is the occlusion ofis the occlusion of
opposing teeth whenopposing teeth when
mandible is in centricmandible is in centric
relation. This may orrelation. This may or
may not coincide withmay not coincide with
the maximalthe maximal
intercuspal position,intercuspal position,
also known asalso known as
maximal intercuspalmaximal intercuspal
position (ICP) orposition (ICP) or
habitual occlusion.habitual occlusion.

 Centric relationCentric relation
 Centric occlusionCentric occlusion

Centric contactsCentric contacts
 Areas of occlusalAreas of occlusal
contact that acontact that a
supporting cusp makesupporting cusp make
with opposing teeth inwith opposing teeth in
centric occlusion arecentric occlusion are
centric contactscentric contacts
 Centric contactsCentric contacts
contribute to occlusalcontribute to occlusal
stabilitystability

 Posterior centric contacts consists of facial rangePosterior centric contacts consists of facial range
of contact and lingual range of contact.of contact and lingual range of contact.
 Facial range: mandibular cusp tips contact theFacial range: mandibular cusp tips contact the
central fossa and mesial marginal ridges of thecentral fossa and mesial marginal ridges of the
opposing maxillary teethopposing maxillary teeth
 Lingual range: maxillary cusp tips contact theLingual range: maxillary cusp tips contact the
central fossa and distal marginal ridges of thecentral fossa and distal marginal ridges of the
 Anterior centric contacts have only 1 range ofAnterior centric contacts have only 1 range of
contact and are in line with the facial range ofcontact and are in line with the facial range of
posterior centric contactsposterior centric contacts
 Centric contacts often occur on the inclines of theCentric contacts often occur on the inclines of the
posterior teeth, these contacts that occur onposterior teeth, these contacts that occur on
inclines are called as poded centric contacts.inclines are called as poded centric contacts.

 Occluding surfaces areOccluding surfaces are
further divided into:further divided into:
 Surface contactSurface contact
 cusp and fossa contactcusp and fossa contact
 Ridge and embrassureRidge and embrassure
contact (cusp andcontact (cusp and
embrassure contact)embrassure contact)
 Ridge and grooveRidge and groove
contactcontact

 Idealized cusp-fossa relationship:Idealized cusp-fossa relationship:

Eccentric contactsEccentric contacts
 The term eccentric has been used to describe anyThe term eccentric has been used to describe any
movement of the mandible in the ICP that resultsmovement of the mandible in the ICP that results
in tooth contactin tooth contact
 Two types a) functional occlusionTwo types a) functional occlusion
b) non-functional occlusionb) non-functional occlusion
 Functional occlusionFunctional occlusion (working side occlusion):(working side occlusion):
refers to tooth contacts that occur in the segmentrefers to tooth contacts that occur in the segment
of the arch towards which the mandible movesof the arch towards which the mandible moves
 Lateral functional occlusion: it includes toothLateral functional occlusion: it includes tooth
contacts that occur on canines and posteriorcontacts that occur on canines and posterior
teeth on the side towards which the mandibleteeth on the side towards which the mandible
movesmoves..

 Lateral functional occlusionLateral functional occlusion
can be of two types:can be of two types:
 i) canine guidedi) canine guided
occlusionocclusion:: during theduring the
lateral mandibularlateral mandibular
movement, the opposingmovement, the opposing
upper and lower canines ofupper and lower canines of
the working side contactthe working side contact
thereby causing disclusionthereby causing disclusion
of all posterior teeth on theof all posterior teeth on the
working and balancingworking and balancing
sidessides
 In canine guided occlusionIn canine guided occlusion
the mandibular cusp tipthe mandibular cusp tip
tracks from the centrictracks from the centric
contact point at the mesialcontact point at the mesial
marginal ridge towards themarginal ridge towards the
cusp tip of the maxillarycusp tip of the maxillary
canine.canine.

 ii) grouped lateralii) grouped lateral
occlusionocclusion:: in additionin addition
to canine guidanceto canine guidance
certain other posteriorcertain other posterior
teeth on the workingteeth on the working
side also contactside also contact
during the lateralduring the lateral
movement of themovement of the
mandible, called asmandible, called as
grouped lateralgrouped lateral
occlusionocclusion

 Protrusive functional occlusionProtrusive functional occlusion: it includes: it includes
eccentric contacts that occur when the mandibleeccentric contacts that occur when the mandible
moves forward. Ideally the six mandibularmoves forward. Ideally the six mandibular
anterior teeth contact along the lingual inclines ofanterior teeth contact along the lingual inclines of
the maxillary anterior teeth while the posteriorsthe maxillary anterior teeth while the posteriors
disocclude.disocclude.
 Non-functional occlusionNon-functional occlusion: they are the tooth: they are the tooth
contacts that occur in the segment away fromcontacts that occur in the segment away from
which the mandible moves, eg: if the mandible iswhich the mandible moves, eg: if the mandible is
moved to the left side contacts occur on the rightmoved to the left side contacts occur on the right
side of the archside of the arch

Occlusal relationshipsOcclusal relationships
 Occlusal relationship of posterior teethOcclusal relationship of posterior teeth::
 The mesiobuccal cusp of the mandibular firstThe mesiobuccal cusp of the mandibular first
molar occludes in the embrassure area betweenmolar occludes in the embrassure area between
the maxillary second premolar and first molarthe maxillary second premolar and first molar
 The mesiobuccal cusp of the maxillary first molarThe mesiobuccal cusp of the maxillary first molar
is aligned directly over the buccal groove of theis aligned directly over the buccal groove of the
mandibular first molarmandibular first molar
 In this relationship each mandibular toothIn this relationship each mandibular tooth
occludes with its counterpart and the adjacentoccludes with its counterpart and the adjacent
mesial tooth.mesial tooth.

 Occlusal relationship of the anterior teethOcclusal relationship of the anterior teeth::
 Maxillary anterior teeth are normally positionedMaxillary anterior teeth are normally positioned
labial to the mandibular anterior teethlabial to the mandibular anterior teeth
 In normal relationship incisal edges of theIn normal relationship incisal edges of the
mandibular incisors are contacting the lingualmandibular incisors are contacting the lingual
surfaces of the maxillary incisorssurfaces of the maxillary incisors
 Contacts occur in the lingual fossa of theContacts occur in the lingual fossa of the
maxillary incisors approx 4mm gingival to themaxillary incisors approx 4mm gingival to the
incisal edgesincisal edges
 When viewed frontally 3-5mm of the mandibularWhen viewed frontally 3-5mm of the mandibular
anterior teeth is hidden by maxillary teeth.anterior teeth is hidden by maxillary teeth.

 The labial inclinationThe labial inclination
of the maxillaryof the maxillary
anterior teeth and theanterior teeth and the
manner in whichmanner in which
occlude with them doocclude with them do
not favour resistancenot favour resistance
to heavy occlusalto heavy occlusal
forcesforces
 The purpose of theThe purpose of the
anterior teeth is toanterior teeth is to
guide the mandibleguide the mandible
through various lateralthrough various lateral
movementsmovements

 The horizontalThe horizontal
overlap by which theoverlap by which the
maxillary anteriorsmaxillary anteriors
overlap theoverlap the
mandibular anteriors,mandibular anteriors,
known as theknown as the
horizontal overlap orhorizontal overlap or
overjetoverjet
 It is the distanceIt is the distance
between the labialbetween the labial
surface of thesurface of the
mandibular incisorsmandibular incisors
and the labial aspectand the labial aspect
of the incisal edge ofof the incisal edge of
the maxillary incisors,the maxillary incisors,
usually parallel to theusually parallel to the
occlusal planeocclusal plane

 The anterior guidance examined in the verticalThe anterior guidance examined in the vertical
plane is known as vertical overlap orplane is known as vertical overlap or overbite.overbite.
 The degree of vertical overlap of the mandibularThe degree of vertical overlap of the mandibular
incisors by their maxillary antagonists, usuallyincisors by their maxillary antagonists, usually
measured perpendicular to the occlusal plane. Itmeasured perpendicular to the occlusal plane. It
is reported either in mm or as a percentage ofis reported either in mm or as a percentage of
the total crown length of the mandibular incisorsthe total crown length of the mandibular incisors
that is overlapped by the maxillary incisors.that is overlapped by the maxillary incisors.

Mandibular movementsMandibular movements
 Eccentric movement: protrusive, laterotrusiveEccentric movement: protrusive, laterotrusive
and retrusiveand retrusive
 Protrusive mandibular movementProtrusive mandibular movement: occurs: occurs
when the mandible moves forward from the ICPwhen the mandible moves forward from the ICP
 In normal occlusion protrusive contacts occur onIn normal occlusion protrusive contacts occur on
the anterior teeth between the incisal edges andthe anterior teeth between the incisal edges and
the labial edges of the mandibular incisors andthe labial edges of the mandibular incisors and
against the lingual fossa areas and incisal edgesagainst the lingual fossa areas and incisal edges
of the maxillary incisorsof the maxillary incisors
 These are considered as the guiding inclines ofThese are considered as the guiding inclines of
the anterior teeththe anterior teeth

 On posterior teeth itOn posterior teeth it
causes mandibular centriccauses mandibular centric
cusp to pass anteriorlycusp to pass anteriorly
across the occlusalacross the occlusal
surfaces of the maxillarysurfaces of the maxillary
teethteeth
 Contacts occur betweenContacts occur between
the distal inclines of thethe distal inclines of the
maxillary lingual cusp andmaxillary lingual cusp and
mesial inclines of themesial inclines of the
opposing fossa andopposing fossa and
marginal ridges, can alsomarginal ridges, can also
occur between the mesialoccur between the mesial
inclines of the mandibularinclines of the mandibular
buccal cusps and distalbuccal cusps and distal
inclines of the opposinginclines of the opposing
cusp and marginal ridgescusp and marginal ridges

 Laterotrusive mandibular movementLaterotrusive mandibular movement: right: right
and left mandibular posterior teeth move acrossand left mandibular posterior teeth move across
their opposing teeth in different directionstheir opposing teeth in different directions
 eg: when the mandible moves laterally to theeg: when the mandible moves laterally to the
left, the left mandibular posterior teeth will moveleft, the left mandibular posterior teeth will move
laterally across their opposing teeth and the rightlaterally across their opposing teeth and the right
teeth will move mediallyteeth will move medially
 Contacts occur in 2 incline areasContacts occur in 2 incline areas
 One contact in between the inner inclines of theOne contact in between the inner inclines of the
maxillary buccal cusp and outer inclines ofmaxillary buccal cusp and outer inclines of
mandibular buccal cuspmandibular buccal cusp
 The other contact is between the outer inclines ofThe other contact is between the outer inclines of
the maxillary lingual cusp and inner inclines ofthe maxillary lingual cusp and inner inclines of
the mandibular lingual cuspsthe mandibular lingual cusps
 These contacts are termed as laterotrusiveThese contacts are termed as laterotrusive
working contactsworking contacts

 In same left lateral movement the rightIn same left lateral movement the right
mandibular teeth are passing in medial directionmandibular teeth are passing in medial direction
across their opposing teethacross their opposing teeth
 Potential sites of contacts are between innerPotential sites of contacts are between inner
inclines of maxillary lingual cusps and innerinclines of maxillary lingual cusps and inner
inclines of the mandibular buccal cuspsinclines of the mandibular buccal cusps
 These are termed as mediotrusive contacts orThese are termed as mediotrusive contacts or
non-working contactsnon-working contacts
 In anterior teeth canines contact and thereforeIn anterior teeth canines contact and therefore
have laterotrusive contacts, occurs between thehave laterotrusive contacts, occurs between the
labial surfaces and incisal edges of mandibularlabial surfaces and incisal edges of mandibular
canines and lingual fossa and incisal edges ofcanines and lingual fossa and incisal edges of
maxillary caninesmaxillary canines


 Retrusive mandibularRetrusive mandibular
movementmovement: occurs when: occurs when
the mandible movesthe mandible moves
posteriorly from the ICPposteriorly from the ICP
 This movement is quiteThis movement is quite
small and restricted by thesmall and restricted by the
ligamentous structureligamentous structure
 Mandibular buccal cuspsMandibular buccal cusps
move distally across themove distally across the
opposing maxillary cuspsopposing maxillary cusps
 Contacts occur betweenContacts occur between
the distal inclines of thethe distal inclines of the
mandibular buccal cuspsmandibular buccal cusps
and the mesial inclines ofand the mesial inclines of
the opposing fossa andthe opposing fossa and
marginal ridgesmarginal ridges
 In maxillary arch occursIn maxillary arch occurs
between the mesialbetween the mesial
inclines of the opposinginclines of the opposing
central fossa and marginalcentral fossa and marginal
ridgesridges

MANDIBULAR MOVEMENTS INMANDIBULAR MOVEMENTS IN
DIFFERENT PLANEDIFFERENT PLANE

 MANDIBULAR MOVEMENTS IN SAGITTALMANDIBULAR MOVEMENTS IN SAGITTAL
PLANEPLANE::
 Possselt showed that mandibular movementsPossselt showed that mandibular movements
take place within the framework of thetake place within the framework of the
reproducible border movements.reproducible border movements.
 If the mandible is held back and up either by theIf the mandible is held back and up either by the
patient or the operator a hinge movement can bepatient or the operator a hinge movement can be
traced for the lower incisors from centric relationtraced for the lower incisors from centric relation
(distance of 3/4(distance of 3/4thth
– 1 inch)– 1 inch)
 This movement is called the terminal hingeThis movement is called the terminal hinge
movement of the mandible, maintains amovement of the mandible, maintains a
stationary rotation axis (point C) through the twostationary rotation axis (point C) through the two
tempromandibular joints.tempromandibular joints.

 Also known as centricAlso known as centric
relation or retrudedrelation or retruded
contact position orcontact position or
ligamentous positionligamentous position
 If an attempt is made toIf an attempt is made to
open the jaw in theopen the jaw in the
retrusive path, theretrusive path, the
movement changes themovement changes the
axis of rotation at D (D-axis of rotation at D (D-
slightly behind theslightly behind the
mandibular foramen)mandibular foramen)
 The condyles moves downThe condyles moves down
to E but still the movementto E but still the movement
revolves around therevolves around the
intercondylar axisintercondylar axis
 Closure with the jaw in aClosure with the jaw in a
forward or protrusiveforward or protrusive
position follows the path Eposition follows the path E
to F while the condyle isto F while the condyle is
placed on the articularplaced on the articular
tuberculum.tuberculum.

 A short movement path that can be recordedA short movement path that can be recorded
between CR & CO when the teeth are broughtbetween CR & CO when the teeth are brought
into contact in centric relation and if the patientinto contact in centric relation and if the patient
squeezes his or her jaw together in centricsqueezes his or her jaw together in centric
occlusion. This movement is called slide in centricocclusion. This movement is called slide in centric
or eccentric slideor eccentric slide
 The slide is often a combination of forward andThe slide is often a combination of forward and
lateral movement.lateral movement.

 SIGNIFICANCE OF CENTRICSIGNIFICANCE OF CENTRIC::
 Word centric was originally used to indicate whatWord centric was originally used to indicate what
was believed to be stationary rotation centre orwas believed to be stationary rotation centre or
axis of mandibular movementsaxis of mandibular movements
 The term centric is used to designate an optimumThe term centric is used to designate an optimum
functional relationship or contact positionfunctional relationship or contact position
between the mandible and maxillabetween the mandible and maxilla

 MANDIBULAR MOVEMENTS IN HORIZONTALMANDIBULAR MOVEMENTS IN HORIZONTAL
PLANE :PLANE :
 Mandibular movements occur perpendicular toMandibular movements occur perpendicular to
horizontal planehorizontal plane
 The border movements for the incisor point canThe border movements for the incisor point can
be traced by gothic arch or gysi tracing in thebe traced by gothic arch or gysi tracing in the
horizontal planehorizontal plane
 As the mandible moves in retrusive, lateralAs the mandible moves in retrusive, lateral
excursive movements; rotation occurs around theexcursive movements; rotation occurs around the
axis on the working side condyle, On the workingaxis on the working side condyle, On the working
side the rotating condyle may move laterally.side the rotating condyle may move laterally.

 The opposing or the balancing condyle movesThe opposing or the balancing condyle moves
down, forward and inward and makes an angledown, forward and inward and makes an angle
with the median plane when projectedwith the median plane when projected
perpendicularly on the horizontal planeperpendicularly on the horizontal plane
 The lateral shift of the mandible calledThe lateral shift of the mandible called bennettbennett
movementmovement is measured by the distance of theis measured by the distance of the
condyle on working side.condyle on working side.
 This angle is called theThis angle is called the bennett anglebennett angle
 The lateral movement may have a retrusive orThe lateral movement may have a retrusive or
protrusive component or move straight laterallyprotrusive component or move straight laterally
 The movement may end at any point in 60The movement may end at any point in 60
degree triangledegree triangle

 MANDIBULAR MOVEMENTS IN FRONTALMANDIBULAR MOVEMENTS IN FRONTAL
PLANE:PLANE:
 The movements recorded in frontal plane varyThe movements recorded in frontal plane vary
greatly with the type of the occlusal contactgreatly with the type of the occlusal contact
relationshiprelationship
 A shield shaped pattern is seen when mandibularA shield shaped pattern is seen when mandibular
movements are viewed in frontal planemovements are viewed in frontal plane
 Lateral masticatory functions and bruxism haveLateral masticatory functions and bruxism have
patterns that are recorded in frontal planepatterns that are recorded in frontal plane

 In a protrusiveIn a protrusive
movement observedmovement observed
in the frontal plane,in the frontal plane,
both the condylarboth the condylar
process moveprocess move
downwards as theydownwards as they
slide along theslide along the
tubercular eminencestubercular eminences
 Most common inMost common in
person withperson with
unrestricted freedomunrestricted freedom
of occlusal contactof occlusal contact
movement is amovement is a
smooth uncrossedsmooth uncrossed
path of movementpath of movement
that returns verythat returns very
closely to the sameclosely to the same
closed postion forclosed postion for
every chewing stroke.every chewing stroke.

Mandibular movements and occlusalMandibular movements and occlusal
morphologymorphology
 The intercondylar distance influences the positionThe intercondylar distance influences the position
and direction of the groove placementand direction of the groove placement
 The greater the intercondylar distance more distalThe greater the intercondylar distance more distal
must be the placement of the ridges andmust be the placement of the ridges and
balancing grooves on the mandibular teeth andbalancing grooves on the mandibular teeth and
more mesial on the maxillary teeth, also greatermore mesial on the maxillary teeth, also greater
must be the lingual concavity of the maxillarymust be the lingual concavity of the maxillary
teethteeth
 In bennett movement: greater the movementIn bennett movement: greater the movement
more mesial must be the directional placement ofmore mesial must be the directional placement of
the ridges and grooves on the mandibular teeththe ridges and grooves on the mandibular teeth
and more distal on the maxillary teethand more distal on the maxillary teeth

 In vertical plane: when the condyle movesIn vertical plane: when the condyle moves
laterally & superiorly the lingual concavity of thelaterally & superiorly the lingual concavity of the
maxillary anterior teeth must be greatermaxillary anterior teeth must be greater
 When the condyle moves laterally and inferiorlyWhen the condyle moves laterally and inferiorly
the heights of the cusp relative to the fossa depththe heights of the cusp relative to the fossa depth
can be made greatercan be made greater
 In straight protrusive movement, the degree ofIn straight protrusive movement, the degree of
the horizontal and vertical overlap and thethe horizontal and vertical overlap and the
inclination of the maxillary teeth are related toinclination of the maxillary teeth are related to
requirement of cusp height for posterior teethrequirement of cusp height for posterior teeth
 The greater the horizontal overlap of theThe greater the horizontal overlap of the
maxillary anterior teeth the shorter the cuspsmaxillary anterior teeth the shorter the cusps
need to be to prevent posterior contactneed to be to prevent posterior contact
 In vertical overlap the smaller the overlap theIn vertical overlap the smaller the overlap the
shorter the cusp of posterior teeth must be madeshorter the cusp of posterior teeth must be made

Envelope of motionEnvelope of motion
 By combining the mandibular border movementsBy combining the mandibular border movements
in the three planes a three- dimensional envelopein the three planes a three- dimensional envelope
of motion can be produced that represents theof motion can be produced that represents the
maximum range of movement of the mandiblemaximum range of movement of the mandible
 The superior surface of the envelope isThe superior surface of the envelope is
determined by the tooth contacts whereas thedetermined by the tooth contacts whereas the
borders are primarily determined by ligaments nborders are primarily determined by ligaments n
joint anatomy.joint anatomy.
 During a simple lateral movement, motion occursDuring a simple lateral movement, motion occurs
around each axis and simultaneously each axisaround each axis and simultaneously each axis
tilts to accommodate the movement occuringtilts to accommodate the movement occuring
around the each axisaround the each axis

 The total envelope of the mandibular movement:The total envelope of the mandibular movement:
 Mandibular incisors track along the lingualMandibular incisors track along the lingual
concavity of the maxillary anterior teethconcavity of the maxillary anterior teeth
 Edge to edge positionEdge to edge position
 Incisors move superiorly until posterior toothIncisors move superiorly until posterior tooth
contact recurscontact recurs
 Protrusive pathProtrusive path
 Most protrusive mandibular position.Most protrusive mandibular position.

BibliographyBibliography
 Major M. Ash; wheeler’s dental anatomy, physiology andMajor M. Ash; wheeler’s dental anatomy, physiology and
occlusion; 7occlusion; 7thth
edition;417-420, 460-475,edition;417-420, 460-475,
 Major M. Ash, Sigurd Ramfjord; Occlusion; 4Major M. Ash, Sigurd Ramfjord; Occlusion; 4thth
edition; 3-8,edition; 3-8,
128-142, 164-168128-142, 164-168
 Jeffery P. Okeson; management of tempromandibularJeffery P. Okeson; management of tempromandibular
disorders and occlusion; 5disorders and occlusion; 5thth
edition; 67-90, 94-107edition; 67-90, 94-107
 T.M.Graber; orthodontics principles and practice; 3T.M.Graber; orthodontics principles and practice; 3rdrd
edition; 181-184edition; 181-184
 John daskalogiannakis; The glossary of orthodontic terms;John daskalogiannakis; The glossary of orthodontic terms;
88thth
editionedition
 The glossary of prosthodontic terms; 1The glossary of prosthodontic terms; 1stst
editionedition
 T.M.Graber & Brainerd F. swain; Orthodontics currentT.M.Graber & Brainerd F. swain; Orthodontics current
principles and techniques; 1principles and techniques; 1stst
edition; 5-6edition; 5-6

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