Occlusion

CONCEPTS OF OCCLUSIONCONCEPTS OF OCCLUSION
DEPARTMENT OF ORTHODONTICSDEPARTMENT OF ORTHODONTICS
www.indiandentalacademy.comwww.indiandentalacademy.com

INTRODUCTIONINTRODUCTION
The goal of modern orthodontics according toThe goal of modern orthodontics according to
Profitt is “Profitt is “the creation of best possible occlusalthe creation of best possible occlusal
relationship within the framework of acceptablerelationship within the framework of acceptable
facial aesthetics and stability of resultfacial aesthetics and stability of result”.”.
OcclusionOcclusion – The relationship of maxillary and– The relationship of maxillary and
mandibular teeth when they are in functionalmandibular teeth when they are in functional
contact during activity of the mandiblecontact during activity of the mandible
- Dorland’s Medical Dictionary- Dorland’s Medical Dictionary

Dental occlusion varies among individualsDental occlusion varies among individuals
according to tooth size and shape, toothaccording to tooth size and shape, tooth
position, timing and sequence of eruption,position, timing and sequence of eruption,
dental arch size and shape and pattern ofdental arch size and shape and pattern of
craniofacial growth.craniofacial growth.
The position of the teeth within the jaws andThe position of the teeth within the jaws and
the mode of occlusion are determined bythe mode of occlusion are determined by
developmental processes that interact on thedevelopmental processes that interact on the
teeth and their associated structures duringteeth and their associated structures during
the period of formation, growth and post natalthe period of formation, growth and post natal
modificationmodification

TERMINOLOGIES USED IN OCCLUSIONTERMINOLOGIES USED IN OCCLUSION
Normal Occlusion :Normal Occlusion :
– Normal occlusion implies a situation commonlyNormal occlusion implies a situation commonly
found in the absence of disease. It shouldfound in the absence of disease. It should
include not only a range of anatomicallyinclude not only a range of anatomically
acceptable values but also physiologicalacceptable values but also physiological
adaptability.adaptability.
– It is always a range never a point.It is always a range never a point.
Ideal Occlusion :Ideal Occlusion :
– The concept of ideal or optimal occlusion refersThe concept of ideal or optimal occlusion refers
both to an aesthetic and physiologic ideal. Itboth to an aesthetic and physiologic ideal. It
includes functional harmony, stability ofincludes functional harmony, stability of
masticatory system & Neuromuscular harmonymasticatory system & Neuromuscular harmony

Physiologic occlusion :Physiologic occlusion :
– The occlusion that shows no signs of occlusion relatedThe occlusion that shows no signs of occlusion related
pathosis. It may not be an ideal occlusion but it is devoidpathosis. It may not be an ideal occlusion but it is devoid
of any pathological manifestations in the surroundingof any pathological manifestations in the surrounding
tissues.tissues.
Traumatic occlusion :Traumatic occlusion :
– An occlusion judged to be causative factors in theAn occlusion judged to be causative factors in the
formation of traumatic lesions of disturbances in theformation of traumatic lesions of disturbances in the
orofacial complex.orofacial complex.
Therapeutic occlusionTherapeutic occlusion ::
– It is a treated occlusion employed to counteractIt is a treated occlusion employed to counteract
structural interrelationship related to traumaticstructural interrelationship related to traumatic
occlusion.occlusion.

THE DEVELOPMENT OF THE CONCEPTSTHE DEVELOPMENT OF THE CONCEPTS
OF OCCLUSIONOF OCCLUSION
The development of concept of occlusion can be tracedThe development of concept of occlusion can be traced
through fiction and hypothesis to fact.through fiction and hypothesis to fact.
The fictional approach was a convenient arrangement ofThe fictional approach was a convenient arrangement of
a series of observation and thoughts more or lessa series of observation and thoughts more or less
logically arranged.logically arranged.
The hypothetical approach was based on provisionalThe hypothetical approach was based on provisional
acceptance of certain logical entities. This was to fill inacceptance of certain logical entities. This was to fill in
the gaps in empirical knowledge and thus tentativelythe gaps in empirical knowledge and thus tentatively
complete the picture.complete the picture.
Fact is a truth known by actual experience orFact is a truth known by actual experience or
observation. Both the fictional and hypothetical approachobservation. Both the fictional and hypothetical approach
are necessary preludes to the establishment of fact.are necessary preludes to the establishment of fact.

The development of concept of occlusionThe development of concept of occlusion
thus can be divided into three periodsthus can be divided into three periods
– The fictional period, prior to 1900The fictional period, prior to 1900
– The hypothetical period from 1900 to 1930The hypothetical period from 1900 to 1930
– The factual period from 1930 to presentThe factual period from 1930 to present
The transition from one period to anotherThe transition from one period to another
was gradual with considerable overlapingwas gradual with considerable overlaping
There is another trend in the developmentThere is another trend in the development
of the concept of occlusion, the trend fromof the concept of occlusion, the trend from
the static to the dynamicthe static to the dynamic

FICTIONAL PERIODFICTIONAL PERIOD
Pioneers like Fuller, Clark and Imrie talkedPioneers like Fuller, Clark and Imrie talked
of “of “AntagonismAntagonism”, “”, “MeetingMeeting” or “” or “GlidingGliding””
of teeth.of teeth.
The creation of normal standard, a basisThe creation of normal standard, a basis
on which to compare departures fromon which to compare departures from
normal was lacking. But this served as anormal was lacking. But this served as a
working hypothesis or subsequentlyworking hypothesis or subsequently
became established fact after definitivebecame established fact after definitive
researchresearch

Eugene Talbot published his book “Eugene Talbot published his book “Irregularities ofIrregularities of
the teeth and their treatmentthe teeth and their treatment” in 1903. he” in 1903. he
attributes facial deformities to maternal impressionsattributes facial deformities to maternal impressions
and delineates in great detail the adolescentand delineates in great detail the adolescent
neuroses of nasal and facial bones, developmentalneuroses of nasal and facial bones, developmental
neurosis of eye, the maxillary bone, the palate, toothneurosis of eye, the maxillary bone, the palate, tooth
position and so forth.position and so forth.
The Talbot concept of normal occlusion was that itThe Talbot concept of normal occlusion was that it
was a historical event, passed in the decline of thewas a historical event, passed in the decline of the
species and normality was possible only withspecies and normality was possible only with
atavism or throwback to our primitive ancestorsatavism or throwback to our primitive ancestors

HYPOTHETICAL PERIODHYPOTHETICAL PERIOD
Edward H. Angle,Edward H. Angle,
– It was him, who channelised orthodonticIt was him, who channelised orthodontic
thinking on occlusion and brought the conceptthinking on occlusion and brought the concept
out of realm of fictionout of realm of fiction
– In 1907, Angle summarised his views asIn 1907, Angle summarised his views as
‘‘occlusion shall be defied as being theocclusion shall be defied as being the
normal relation of the occlusal inclinednormal relation of the occlusal inclined
planes of the teeth when the jaws areplanes of the teeth when the jaws are
closedclosed’’..
– Angle cites the example of a skull of Negro maleAngle cites the example of a skull of Negro male
from Broomell which he names ‘from Broomell which he names ‘Old GloryOld Glory’. In’. In
‘‘Old GloryOld Glory’ all the teeth are present and’ all the teeth are present and
arranged in a graceful curve. He emphasizesarranged in a graceful curve. He emphasizes
that all teeth are necessary for maintainingthat all teeth are necessary for maintaining
occlusion. He compares ‘occlusion. He compares ‘Old GloryOld Glory’ with the’ with the
profile of Appollo Belvedre a white maleprofile of Appollo Belvedre a white male

Angle furnished his ‘Angle furnished his ‘key to occlusionkey to occlusion’ and’ and
emphasizes the first permanent molarsemphasizes the first permanent molars
especially the upper first permanent molar andespecially the upper first permanent molar and
considers them to be most constant in takingconsiders them to be most constant in taking
normal position.normal position.
This formed the basis of Angle’s classification ofThis formed the basis of Angle’s classification of
malocclusion and this has withstood the test ofmalocclusion and this has withstood the test of
time.time.
From the hypothesis of constancy of first molarFrom the hypothesis of constancy of first molar
and the line of occlusion, Angle developed theand the line of occlusion, Angle developed the
concept that all teeth should be present if normalconcept that all teeth should be present if normal
occlusion is to be achived.occlusion is to be achived.

Mathew Cryer and Calvin CaseMathew Cryer and Calvin Case
Cryer pointed out that Angle showed the straight profile ofCryer pointed out that Angle showed the straight profile of
Apollo Belvedre and chose a skull of negro male ‘Apollo Belvedre and chose a skull of negro male ‘OldOld
GloryGlory’ to exemplify ideal occlusion. He questioned how’ to exemplify ideal occlusion. He questioned how
one could mix a prognathic denture with an orthodonticone could mix a prognathic denture with an orthodontic
profile.profile.
Case took Angle to task for considering bimaxillaryCase took Angle to task for considering bimaxillary
protrusion as normal and for not recognizing individualprotrusion as normal and for not recognizing individual
variation.variation.
Case accepts Angle’s hypothesis of constancy of firstCase accepts Angle’s hypothesis of constancy of first
molar. Case related the facile profile to each type ofmolar. Case related the facile profile to each type of

He proposed the concept of apicalHe proposed the concept of apical
base and divided dentofacial areabase and divided dentofacial area
into four segments or zones ofinto four segments or zones of
movement.movement.
He was aware of the role of nose and chin button and theirHe was aware of the role of nose and chin button and their
influence on profile.influence on profile.
Case proposed the concept of normal and ideal occlusion.Case proposed the concept of normal and ideal occlusion.
Van LoonVan Loon used plaster cast of the face and teeth inused plaster cast of the face and teeth in
anthropologic manner which Simon developed further.anthropologic manner which Simon developed further.
The idea that teeth should be present to obtain normal facialThe idea that teeth should be present to obtain normal facial
contour was loosing ground.contour was loosing ground.
In 1908 Bennett proposed that the condylar movement wasIn 1908 Bennett proposed that the condylar movement was
primarily rotatary on opening from occlusion to rest positionprimarily rotatary on opening from occlusion to rest position
and later on after passing this point became translatory.and later on after passing this point became translatory.

Lischer and Paul SimonLischer and Paul Simon
They bordened the concept of occlusion by relatingThey bordened the concept of occlusion by relating
the teeth to the rest of the face and cranium. Theythe teeth to the rest of the face and cranium. They
related teeth in occlusal contact to cranial andrelated teeth in occlusal contact to cranial and
facial planes outside the denture proper.facial planes outside the denture proper.
Though the concept of orbital plane as basis forThough the concept of orbital plane as basis for
determining antero-posterior position of dentitiondetermining antero-posterior position of dentition
did not stand up. It introduced the idea of facialdid not stand up. It introduced the idea of facial
ramification of malocclusion outside the dentalramification of malocclusion outside the dental
area.area.

Milo HellmanMilo Hellman
Hellman showed the racial variation in so calledHellman showed the racial variation in so called
normal occlusion through anthropologicalnormal occlusion through anthropological
studies.studies.
Hellman and others studied the prognathism ofHellman and others studied the prognathism of
the human dentition in relation to a cranial basethe human dentition in relation to a cranial base
Stages of Dental development HellmanStages of Dental development Hellman
IIA Eruption of 2IIA Eruption of 2ndnd
deciduous molardeciduous molar
IIC Eruption of permanent incisorIIC Eruption of permanent incisor
IIIA Eruption of permanent 1IIIA Eruption of permanent 1stst
molarmolar
IIIB Eruption of canines and premolarIIIB Eruption of canines and premolar
IIIC Beginning of 2IIIC Beginning of 2ndnd
molar eruptionmolar eruption
IVA Eruption of 2IVA Eruption of 2ndnd
molar completedmolar completed
VA (Adult) eruption of 3VA (Adult) eruption of 3rdrd
molar completedmolar completedwww.indiandentalacademy.comwww.indiandentalacademy.com

Dimensional change in the
phase on the same time
scale. Facial depth increases
most, height less rapidly and
width the least

FACTUAL PERIODFACTUAL PERIOD
In 1930 Holly Broadbent and Hans Planer introduced anIn 1930 Holly Broadbent and Hans Planer introduced an
accurate techniue of roentogenographic cephaolmetry.accurate techniue of roentogenographic cephaolmetry.
Investigators were able to follow longitudinally the orofacialInvestigators were able to follow longitudinally the orofacial
developmental pattern and the intricacies of tooth formation,developmental pattern and the intricacies of tooth formation,
eruption and adjustment.eruption and adjustment.
Planer laid emphasis on efficiency of masticating mechanism.Planer laid emphasis on efficiency of masticating mechanism.
He explained physiological rest position and verticalHe explained physiological rest position and vertical
dimensiondimension
A third element of occlusion, the TMJ has been receivingA third element of occlusion, the TMJ has been receiving
more attention. There is an intimate relationship between themore attention. There is an intimate relationship between the
interdigitation of the teeth, the status of controlling,interdigitation of the teeth, the status of controlling,
musculature and the integrity of the TMJ.musculature and the integrity of the TMJ.

DYNAMIC OCCLUSIONDYNAMIC OCCLUSION
Recognition of the role played by muscles physiology and theRecognition of the role played by muscles physiology and the
TMJ has firmly entrenched the dynamic functional concept.TMJ has firmly entrenched the dynamic functional concept.
The 13 muscle attachment to the mandible in addition toThe 13 muscle attachment to the mandible in addition to
articular capsule and tendon provide a high degree of stabilityarticular capsule and tendon provide a high degree of stability
of position that occlusal equilibration and full mouthof position that occlusal equilibration and full mouth
reconstruction can’t change permanentlyreconstruction can’t change permanently
The teeth are in occlusal contact only 2 to 6% of the time.The teeth are in occlusal contact only 2 to 6% of the time.
Therefore 94% of the time, they are apart. The largestTherefore 94% of the time, they are apart. The largest
segment of time is in postural rest position determined bysegment of time is in postural rest position determined by
musculature.musculature.
Postural rest position is a good place to start in anPostural rest position is a good place to start in an
assessment of vertical status and harmony of orofacialassessment of vertical status and harmony of orofacial
features.features.

Occlusion is a dynamic entity show variation accordingOcclusion is a dynamic entity show variation according
to age and sex. Most girls by the age of 12 achieveto age and sex. Most girls by the age of 12 achieve
relatively stable occlusion whereas boys achieve that arelatively stable occlusion whereas boys achieve that a
bit later due to continuing growth pattern.bit later due to continuing growth pattern.
Three components of occlusion can be summed up asThree components of occlusion can be summed up as
1.1. Occlusal position (or) tooth contact positionOcclusal position (or) tooth contact position
- Masticatory habits, tooth inclination and- Masticatory habits, tooth inclination and
malposition, shape of teeth, premature contact,malposition, shape of teeth, premature contact,
faulty restoration, tooth loss, the condition offaulty restoration, tooth loss, the condition of
periodontium affect the occlusal positionsperiodontium affect the occlusal positions
1.1. Postural resting positionPostural resting position
2.2. TMJTMJ

FACTORS & FORCES THAT DETERMINEFACTORS & FORCES THAT DETERMINE
TOOTH POSITIONTOOTH POSITION
The alignment of the dentition in the dental arches occur as a result ofThe alignment of the dentition in the dental arches occur as a result of
complex multidirectional forces acting on the teeth during and after eruption.complex multidirectional forces acting on the teeth during and after eruption.
Labial to the teeth are tip and cheeks which provide relatively light butLabial to the teeth are tip and cheeks which provide relatively light but
constant lingually directed forces. On the opposite side of the dental arch isconstant lingually directed forces. On the opposite side of the dental arch is
the tongue which provides labially directed forces. Hence the labiolingualthe tongue which provides labially directed forces. Hence the labiolingual
and buccolingual forces are equal. This is call neutral position.and buccolingual forces are equal. This is call neutral position.
Proimal contact between adjacent teeth helps maintain the teeth in normalProimal contact between adjacent teeth helps maintain the teeth in normal
alignmentalignment
Occlusal contact is another important factor that helps to stabilize toothOcclusal contact is another important factor that helps to stabilize tooth
alignment.alignment.

Intra Arch Tooth AlignmentIntra Arch Tooth Alignment
Relationship of teeth to each other within the dentalRelationship of teeth to each other within the dental
arch.arch.
Plane of occlusionPlane of occlusion
A plane comprising buccal and lingual cusp tip ofA plane comprising buccal and lingual cusp tip of
mandibular posterior teeth of both sides as well asmandibular posterior teeth of both sides as well as
the incisal tip of mandibular anteriors the curvaturethe incisal tip of mandibular anteriors the curvature
of the occlusal plane is because the teeth areof the occlusal plane is because the teeth are
positioned in arches at varying degrees of inclinationpositioned in arches at varying degrees of inclination

According to Wilson the mandibular arch appearsAccording to Wilson the mandibular arch appears
concave and that of maxillary arch convexconcave and that of maxillary arch convex
According to Bonwill, the maxillary and mandibularAccording to Bonwill, the maxillary and mandibular
arches adapt themselves input to an equilateral trianglearches adapt themselves input to an equilateral triangle
of similar sides.of similar sides.
According to Vonspee, cusp and the incisal ridges ofAccording to Vonspee, cusp and the incisal ridges of
teeth display a curved alignments when the arches areteeth display a curved alignments when the arches are
observed from a point opposite to 1observed from a point opposite to 1stst
molarmolar
Monson connected the curvatures in the saggital planeMonson connected the curvatures in the saggital plane
with compensatory curvatures in the vertical plane andwith compensatory curvatures in the vertical plane and
suggested that the mandible arch adopts itself to thesuggested that the mandible arch adopts itself to the
curved segment of a sphere of similar radiuscurved segment of a sphere of similar radius

Curve of SpeeCurve of Spee
An imaginary anteroposterior line from the cusp tips of theAn imaginary anteroposterior line from the cusp tips of the
canine extending to the buccal cusps of the posterior teethcanine extending to the buccal cusps of the posterior teeth
– An excessively concave curve of Spee and mandibularAn excessively concave curve of Spee and mandibular
core line restrict the occlusal surface available for maxillarycore line restrict the occlusal surface available for maxillary
teeth.teeth.
– A flat to slightly concave curve of Spee and mandibularA flat to slightly concave curve of Spee and mandibular
core line bare the proper occlusal surface for optimalcore line bare the proper occlusal surface for optimal
– A convex curve of Spee and mandibular core line bareA convex curve of Spee and mandibular core line bare
excessive portions of the occlusal surface.excessive portions of the occlusal surface.

Curve of WilsonCurve of Wilson
It is a mesiodistal curve that contacts the buccalIt is a mesiodistal curve that contacts the buccal
and lingual cusps tips of the mandibularand lingual cusps tips of the mandibular
posterior teeth.posterior teeth.
It helps in two waysIt helps in two ways
– Teeth aligned parallel to direction of medialTeeth aligned parallel to direction of medial
pterygoid for optimum resistance topterygoid for optimum resistance to
masticatory forces.masticatory forces.
– The elevated buccal cusps prevent food fromThe elevated buccal cusps prevent food from
going past the occlusal table.going past the occlusal table.
Curve of MonsonCurve of Monson
It is obtained by extension of the cruve of speeIt is obtained by extension of the cruve of spee
and curve of Wilson to all cusps and incisaland curve of Wilson to all cusps and incisal
edgesedges

Interarch Tooth AlignmentInterarch Tooth Alignment
Relationship of teeth in one arch to other. TheRelationship of teeth in one arch to other. The
length and width of maxillary arch is higher whenlength and width of maxillary arch is higher when
compared to mandibular arch.compared to mandibular arch.
Supporting cusps (or) centric cuspsSupporting cusps (or) centric cusps
Buccal cusps of the mandibular posterior teethBuccal cusps of the mandibular posterior teeth
and lingual cusp of the maxillary posterior areand lingual cusp of the maxillary posterior are
the centric or supporting cuspsthe centric or supporting cusps
Non centric cuspsNon centric cusps
The buccal cusp of maxillary posterior teeth andThe buccal cusp of maxillary posterior teeth and
lingual cusp of the mandibular posterior teeth.lingual cusp of the mandibular posterior teeth.

Classification of OcclusionClassification of Occlusion
Based on Mandibular PositionBased on Mandibular Position
Centric OcclusionCentric Occlusion
– It is the occlusion of teeth in centric relation. Centric relation hasIt is the occlusion of teeth in centric relation. Centric relation has
been defined as the maxillomandibular relationship in whichbeen defined as the maxillomandibular relationship in which
condyles articulates with the thinnest avascular position of theircondyles articulates with the thinnest avascular position of their
respective discs with the complex in the anterosuperior positionrespective discs with the complex in the anterosuperior position
against the shape of articular eminence. This position isagainst the shape of articular eminence. This position is
independent of tooth contactindependent of tooth contact
The Importance of the centric relation inThe Importance of the centric relation in
orthodonticsorthodontics
– In orthodontics, diagnosis and treatment planning should beIn orthodontics, diagnosis and treatment planning should be
performed by an evaluation of an malocclusion with theperformed by an evaluation of an malocclusion with the
mandible in centric relation (CR), i.e. the natural musculoskeletalmandible in centric relation (CR), i.e. the natural musculoskeletal
position of the condyle in the fossa, in order to obtain the trueposition of the condyle in the fossa, in order to obtain the true
maxillary - mandibular skeletal and dental relations in the threemaxillary - mandibular skeletal and dental relations in the three
planes of space.planes of space.

– If this is overlooked an incorrect diagnosis and treatmentIf this is overlooked an incorrect diagnosis and treatment
plan of the actual malocclusion, along with its unfavourableplan of the actual malocclusion, along with its unfavourable
consequences, may result.consequences, may result.
– During every appointment a patient has to be monitored inDuring every appointment a patient has to be monitored in
CR so that the mechanotherapy is guided to accomplishCR so that the mechanotherapy is guided to accomplish
the final ideal static and functional occlusion with thethe final ideal static and functional occlusion with the
mandible in position.mandible in position.
– If this disregarded several prematurity that may later causeIf this disregarded several prematurity that may later cause
traumatic occlusion or craniomandibular disorders maytraumatic occlusion or craniomandibular disorders may
result.result.
Eccentric occlusionEccentric occlusion
– It is defined as the occlusion, other than centric occlusion.It is defined as the occlusion, other than centric occlusion.
It includesIt includes
Lateral occlusionLateral occlusion
Protruded occlusionProtruded occlusion
Retrusive occlusionRetrusive occlusionwww.indiandentalacademy.comwww.indiandentalacademy.com

Based on relationship of first permanent molarBased on relationship of first permanent molar
The angulation of upper first permanent molar –The angulation of upper first permanent molar –
the key to functional occlusion.the key to functional occlusion.
– They are biggest teeth and their anchorage isThey are biggest teeth and their anchorage is
strongeststrongest
– Their local position in the occlusal arch supports theTheir local position in the occlusal arch supports the
main masticatory functionmain masticatory function
– They influence the vertical dimension of upper andThey influence the vertical dimension of upper and
lower jaw, the occlusal height and esthetic proportionslower jaw, the occlusal height and esthetic proportions
– They are the first erupting teeth of permanentThey are the first erupting teeth of permanent
dentitiondentition
– The anamolies in dental positing are mostly due toThe anamolies in dental positing are mostly due to
more prominent disloacted positions of the crown ofmore prominent disloacted positions of the crown of
upper permanent molar to normal.upper permanent molar to normal.

Key Ridges :Key Ridges :
Infrazygomatic crest. This zygomatic pillar ‘keyInfrazygomatic crest. This zygomatic pillar ‘key
ridge’ – established during growth directly above theridge’ – established during growth directly above the
centre of the roots of the first upper molars andcentre of the roots of the first upper molars and
proceeds along the outside of the wall of theproceeds along the outside of the wall of the
maxillary cavity upto the zygomatic bone.maxillary cavity upto the zygomatic bone.
Key of Age :Key of Age :
Demonstrates the average drift of upper first molarDemonstrates the average drift of upper first molar
downwards and mesially. All angulation show prominentdownwards and mesially. All angulation show prominent
minus angulation.minus angulation.
-17-17oo
: 6 – 7 years: 6 – 7 years
-8-8oo
: 11 years: 11 years
-5-5oo
: 17 years: 17 years

Class I : Neutro OcclusionClass I : Neutro Occlusion
Mesiobuccal cusps of the upper first permanentMesiobuccal cusps of the upper first permanent
molar occludes with the mesiobuccal groove of the lowermolar occludes with the mesiobuccal groove of the lower
first permanent molar. This is called the key of occlusionfirst permanent molar. This is called the key of occlusion
Class II : Disto OcclusionClass II : Disto Occlusion
Condition in which the mandibular first PermanentCondition in which the mandibular first Permanent
molar is placed posterior in relation to the normal class Imolar is placed posterior in relation to the normal class I
conditioncondition
– Division IDivision I
– Division IIDivision II
Class III : Mesio OcclusionClass III : Mesio Occlusion
Condition in which the mandibular first PermanentCondition in which the mandibular first Permanent
molar is placed anterior in relation to the normal class Imolar is placed anterior in relation to the normal class I
conditioncondition www.indiandentalacademy.comwww.indiandentalacademy.com

BASED ON THE ORGANISATIONBASED ON THE ORGANISATION
Canine guided (or) protected occlusionCanine guided (or) protected occlusion – during– during
lateral movements only working side canine comes intolateral movements only working side canine comes into
contact with the other. This result in disclusion of allcontact with the other. This result in disclusion of all
posterior teethposterior teeth
– The canine has a good crown root ratio capable ofThe canine has a good crown root ratio capable of
tolerating high occlusal forcestolerating high occlusal forces
– The canine root has a greater surface area thenThe canine root has a greater surface area then
adjacent teeth. Providing greater proprioception.adjacent teeth. Providing greater proprioception.
– The shape of the palatal surface of the upper canineThe shape of the palatal surface of the upper canine
is concave and is suitable for guiding lateralis concave and is suitable for guiding lateral
movement.movement.

Mutually ProtectedMutually Protected : Posterior teeth prevent: Posterior teeth prevent
excessive contact of the anterior teeth inexcessive contact of the anterior teeth in
maximum intercuspation anterior teethmaximum intercuspation anterior teeth
disengage the posterior teeth in all mandibulardisengage the posterior teeth in all mandibular
excursive movements.excursive movements.
Group FunctionGroup Function : During the lateral movement: During the lateral movement
the buccal cusp of the posterior teeth on thethe buccal cusp of the posterior teeth on the
working side are in contactworking side are in contact

BASED ON PATTERNBASED ON PATTERN
Cusp to embrasure / Marginal ridgeCusp to embrasure / Marginal ridge
occlusionocclusion : Occlusion of one: Occlusion of one
supporting cusps into a fossa and thesupporting cusps into a fossa and the
occlusion of another cusp of the sameocclusion of another cusp of the same
tooth into the embrasure area of twotooth into the embrasure area of two
opposing teeth. This is a tooth-to-two-opposing teeth. This is a tooth-to-two-
teeth relation.teeth relation.
Cusp to fossaCusp to fossa occlusionocclusion ::
Supporting cusp occluding into fossa.Supporting cusp occluding into fossa.
This produces an interdigitation of theThis produces an interdigitation of the
cusps and fossa of one teeth with thecusps and fossa of one teeth with the
fossa of only one opposing tooth. Thisfossa of only one opposing tooth. This
is tooth-to-one-tooth relation.is tooth-to-one-tooth relation.

ANDREWS SIX KEY TO NORMAL OCCLUSIONANDREWS SIX KEY TO NORMAL OCCLUSION
Key I : Molar relationshipKey I : Molar relationship
Key II : Crown angulationKey II : Crown angulation
Key III : Crown inclinationKey III : Crown inclination
Key IV : Absence of RotationKey IV : Absence of Rotation
Key V : Tight ContactKey V : Tight Contact
Key VI : Curve of SpeeKey VI : Curve of Spee
Ten characteristics of an organic occlusionTen characteristics of an organic occlusion
Many of the following ten characteristics have beenMany of the following ten characteristics have been
repeatedly observed in well – preserved, unwornrepeatedly observed in well – preserved, unworn
dentitions.dentitions.
I. Centric Relation OcclusionI. Centric Relation Occlusion
Centric relation is the rearmost and midmost hingedCentric relation is the rearmost and midmost hinged
position of the mandible.position of the mandible.

Centric relation occlusion is the morphologic positionCentric relation occlusion is the morphologic position
of the mandible in centric relation when the posteriorof the mandible in centric relation when the posterior
teeth are intercusped in occlusion.teeth are intercusped in occlusion.
Centric relation occlusion can only be demonstratedCentric relation occlusion can only be demonstrated
with axis-oriented casts mounted on an articulator.with axis-oriented casts mounted on an articulator.
II. Uniform contact in centric relationII. Uniform contact in centric relation
The elimination of centric prematurities is necessaryThe elimination of centric prematurities is necessary
to establish uniform contact in centric relation.to establish uniform contact in centric relation.
There are four possible effects of the fulcrumingThere are four possible effects of the fulcruming
effect of premature centric contacts as follows :effect of premature centric contacts as follows :
– Faceting and wearFaceting and wear
– TMJ DysfunctionTMJ Dysfunction
– Infrabony periodontal bone lossInfrabony periodontal bone loss
– Recession and gingival erosionRecession and gingival erosionwww.indiandentalacademy.comwww.indiandentalacademy.com

III. Cusp-Fossa OcclusionIII. Cusp-Fossa Occlusion
Cusp-to-fossa is a paired relationship between one upper and one lowerCusp-to-fossa is a paired relationship between one upper and one lower
tooth whereby the teeth, in occlusion, act as a single column-the “unit oftooth whereby the teeth, in occlusion, act as a single column-the “unit of
occlusion”.occlusion”.
This design lends much stability and a reciprocation of forces to theThis design lends much stability and a reciprocation of forces to the
occlusionocclusion
Cusps-fossa relations are always preferable to cusp-embrasureCusps-fossa relations are always preferable to cusp-embrasure
occlusion, but are not always achievable.occlusion, but are not always achievable.
IV. Primary Marginal Ridge ContactsIV. Primary Marginal Ridge Contacts
This is a sagittal plane projection. Contact on the distal incline of theThis is a sagittal plane projection. Contact on the distal incline of the
upper mesial marginal ridges against the mesial marginal ridge of theupper mesial marginal ridges against the mesial marginal ridge of the
lower buccal cusp. The distal marginal ridge of the upper lingual cusplower buccal cusp. The distal marginal ridge of the upper lingual cusp
has a similar contact with the mesial incline of the opposing distalhas a similar contact with the mesial incline of the opposing distal
marginal ridge.marginal ridge.
If posterior teeth are lost and the vertical dimension decreases, theIf posterior teeth are lost and the vertical dimension decreases, the
upper anterior teeth will be splayed. When posterior teeth are present,upper anterior teeth will be splayed. When posterior teeth are present,
they prevent wear and possible separation of the front teeth.they prevent wear and possible separation of the front teeth.

V. TripodismV. Tripodism
Every cusp has four ridges : Three out of these four ridgesEvery cusp has four ridges : Three out of these four ridges
can contact an opposing cusp in cusp-fossa occlusion.can contact an opposing cusp in cusp-fossa occlusion.
The cusp tips will be preserved.The cusp tips will be preserved.
The ridges will wear evenly and this prevents the formationThe ridges will wear evenly and this prevents the formation
of non-uniform contacts.of non-uniform contacts.
VI. Cross – Tooth StabilityVI. Cross – Tooth Stability
This is a coronal plane projection of tooth contacts.This is a coronal plane projection of tooth contacts.
Posterior cusps in an organic occlusion are shearers of foodPosterior cusps in an organic occlusion are shearers of food
because they pass close to each other but never close edgebecause they pass close to each other but never close edge
– to edge.– to edge.
VII. Forces in the Long AxisVII. Forces in the Long Axis
Teeth should stand perpendicular to the occlusal plane withTeeth should stand perpendicular to the occlusal plane with
their long axis parallel to the long axis of their antagonisttheir long axis parallel to the long axis of their antagonist
Destructive off – axial forces are minimized, which wouldDestructive off – axial forces are minimized, which would
wear the stamp cusps and cause the teeth to tip,wear the stamp cusps and cause the teeth to tip,

VIII. Narrow Occlusal tableVIII. Narrow Occlusal table
Natural teeth with little wear have narrow occlusalNatural teeth with little wear have narrow occlusal
tables.tables.
If the occlusal table is kept small the forces ofIf the occlusal table is kept small the forces of
closure will be kept within the perimeter of teeth andclosure will be kept within the perimeter of teeth and
directed in the long axis.directed in the long axis.
IX. Maximum Cusp Height and Fossa DepthIX. Maximum Cusp Height and Fossa Depth
Teeth with tallest cusps offer greatest shearTeeth with tallest cusps offer greatest shear
efficiency.efficiency.
Determinants of cusps heightDeterminants of cusps height
– Angle of eminenceAngle of eminence
– TranstrutionTranstrution
– Vertical laterotrusion of the workin condyleVertical laterotrusion of the workin condyle
– Inclination of the occlusal planeInclination of the occlusal plane

X. DisclusionX. Disclusion
The disclusive characteristic of an organicThe disclusive characteristic of an organic
occlusion allows each part of the dentition toocclusion allows each part of the dentition to
perform that function for which it is best suitedperform that function for which it is best suited
Each incisor should be free to contact itsEach incisor should be free to contact its
antimere at an edge-to-edge relationship withoutantimere at an edge-to-edge relationship without
any other tooth in the mouth contacting.any other tooth in the mouth contacting.
When the posterior teeth come into contact inWhen the posterior teeth come into contact in
centric relation occlusion, the function iscentric relation occlusion, the function is
complete and a 0.001” space should separatecomplete and a 0.001” space should separate
the anterior teeth.the anterior teeth.

POSTERIOR GUIDANCEPOSTERIOR GUIDANCE
The shape and angle of the slope of the articularThe shape and angle of the slope of the articular
eminence of the glenoid fossa are the single mosteminence of the glenoid fossa are the single most
important factors in determining the shape and form ofimportant factors in determining the shape and form of
the plane of occlusion.the plane of occlusion.
These shapes have been known in dentistry as theThese shapes have been known in dentistry as the
curve of Spee, curve of Wilson and curve of Monson.curve of Spee, curve of Wilson and curve of Monson.
The range of angulation of articular eminence at theThe range of angulation of articular eminence at the
midpoint inclined plane is from 17midpoint inclined plane is from 17oo
to 77to 77o.o.
The path of the condylar movement in the TMJ is calledThe path of the condylar movement in the TMJ is called
the posterior guidance.the posterior guidance.
Mandibular movements are guided byMandibular movements are guided by
– Shape of TMJShape of TMJ
– Contact of anterior toothContact of anterior tooth
– Masticatory muscleMasticatory muscle

The inclination of the anterior guidance should beThe inclination of the anterior guidance should be
equal to the inclination of posterior guidance. If theequal to the inclination of posterior guidance. If the
incisal guidance is flatter than the condylar path, itincisal guidance is flatter than the condylar path, it
may cause severe neuromuscular problems.may cause severe neuromuscular problems.
If the inclination of the incisal path is flatter than that ofIf the inclination of the incisal path is flatter than that of
the condylar path, the upper and lower posterior teeththe condylar path, the upper and lower posterior teeth
will contact and interfere with the incisive action of thewill contact and interfere with the incisive action of the
anterior teeth.anterior teeth.
Anterior GuidanceAnterior Guidance
It is defined as “It is defined as “the influence of the contactingthe influence of the contacting
surface of anterior teeth – limiting mandibularsurface of anterior teeth – limiting mandibular
movementsmovements”. There must be proper anterior guidance”. There must be proper anterior guidance
of the incisal teeth for disclusion of the posterior teethof the incisal teeth for disclusion of the posterior teeth
and harmonious movement of the mandible.and harmonious movement of the mandible.

VERTICAL DETERMINANTVERTICAL DETERMINANT
CondylarCondylar
guidanceguidance
SteeperSteeper Taller the Posterior CuspsTaller the Posterior Cusps
AnteriorAnterior
guidanceguidance
Greater the VerticalGreater the Vertical
overlapoverlap
Taller the Posterior CuspsTaller the Posterior Cusps
Greater the HorizontalGreater the Horizontal
overlapoverlap
Shorter the Posterior cuspsShorter the Posterior cusps
Plane ofPlane of
OcclusionOcclusion
More parallel the plane toMore parallel the plane to
condylar guidancecondylar guidance
Curve ofCurve of
SpeeSpee
More acuteMore acute Shorter the Posterior cuspsShorter the Posterior cusps
LateralLateral
translationtranslation
movementmovement
GreaterGreater Shorter the Posterior cuspsShorter the Posterior cusps
Greater the immediate sideGreater the immediate side
shiftshift
More superor theMore superor the
movement of rotatingmovement of rotating
condylecondyle

HORIZONTAL DETERMINANTHORIZONTAL DETERMINANT
Distance fromDistance from
rotating condylerotating condyle
GreaterGreater
Wider the angle betweenWider the angle between
laterotrusive andlaterotrusive and
Mediotrusive pathwaysMediotrusive pathways
Distance fromDistance from
midsagittal planemidsagittal plane
GreaterGreater
LateralLateral
translationtranslation
movementmovement
GreaterGreater
IntercondylarIntercondylar
distancedistance
GreaterGreater
Smaller the angle betweenSmaller the angle between

ORTHODONTIC TREATMENT OBJECTIVESORTHODONTIC TREATMENT OBJECTIVES
The orthodontic treament objectives are to provideThe orthodontic treament objectives are to provide
good facial esthetics, and an ideal, static andgood facial esthetics, and an ideal, static and
functional occlusion.functional occlusion.
The static objectives and Andrews’ Six Keys toThe static objectives and Andrews’ Six Keys to
Normal Occlusion.Normal Occlusion.
The functional objectives are obtained with theThe functional objectives are obtained with the
mutually protected occlusion, which present themutually protected occlusion, which present the
following characteristicsfollowing characteristics
1.1. The teeth should present maximum intercuspationThe teeth should present maximum intercuspation
with the mandible in CRwith the mandible in CR
2.2. In CR, all posterior teeth should present effectiveIn CR, all posterior teeth should present effective
occlusal contacts through their long axes and theocclusal contacts through their long axes and the
anterior teeth should present a 0.005 inch clearanceanterior teeth should present a 0.005 inch clearance

3.3. During lateral functional movements of theDuring lateral functional movements of the
mandible, the cuspid should disclude allmandible, the cuspid should disclude all
posterior teeth, (cuspid guidance)posterior teeth, (cuspid guidance)
4.4. During protrusion, the six upper anterior teethDuring protrusion, the six upper anterior teeth
should articulate with the six lower anteriorshould articulate with the six lower anterior
teeth and first or second premolars (in firstteeth and first or second premolars (in first
premolars extraction cases) in order topremolars extraction cases) in order to
disclude all the posterior teeth.disclude all the posterior teeth.
5.5. There should be no balancing sideThere should be no balancing side
intereferences. This relation of the anteriorintereferences. This relation of the anterior
teeth is known as anterior guidanceteeth is known as anterior guidance

CONCLUSIONCONCLUSION
The concept of occlusion has been undergoing seaThe concept of occlusion has been undergoing sea
changes in the course of last century, starting from thechanges in the course of last century, starting from the
days of fiction and passing through the hypothesisdays of fiction and passing through the hypothesis
proposed by Angle and others, we have reached aproposed by Angle and others, we have reached a
factual period of reasoning and proven concepts. Withfactual period of reasoning and proven concepts. With
the introduction of the TMJ as component of occlusionthe introduction of the TMJ as component of occlusion
the idea of dynamic occlusion and functional harmonythe idea of dynamic occlusion and functional harmony
have been emphasized.have been emphasized.
Occlusion, especially in orthodontics during growth, is aOcclusion, especially in orthodontics during growth, is a
process, a process of growing and shifting interactiveprocess, a process of growing and shifting interactive
systems. Orthodontics can be considered as thesystems. Orthodontics can be considered as the
navigation of those systemsnavigation of those systems

Occlusion

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