Concepts of occlusion /certified fixed orthodontic courses by Indian dental academy

CONCEPT OF OCCLUSIONS

INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com

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

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

TERMINOLOGIES USED IN OCCLUSION
Normal Occlusion :
– Normal occlusion implies a situation commonly
found in the absence of disease. It should
include not only a range of anatomically
acceptable values but also physiological
adaptability.
– It is always a range never a point.

Ideal Occlusion :
– The concept of ideal or optimal occlusion refers
both to an aesthetic and physiologic ideal. It
includes functional harmony, stability of
masticatory system & Neuromuscular harmony

Physiologic occlusion :
– The occlusion that shows no signs of occlusion related
pathosis. It may not be an ideal occlusion but it is devoid
of any pathological manifestations in the surrounding
tissues.

Traumatic occlusion :
– An occlusion judged to be causative factors in the
formation of traumatic lesions of disturbances in the
orofacial complex.

Therapeutic occlusion :
– It is a treated occlusion employed to counteract
structural interrelationship related to traumatic
occlusion.

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

The development of concept of occlusion
thus can be divided into three periods
– The fictional period, prior to 1900
– The hypothetical period from 1900 to 1930
– The factual period from 1930 to present

The transition from one period to another
was gradual with considerable overlaping
There is another trend in the development
of the concept of occlusion, the trend from
the static to the dynamic

FICTIONAL PERIOD
Pioneers like Fuller, Clark and Imrie talked
of “Antagonism”, “Meeting” or “Gliding”
of teeth.
The creation of normal standard, a basis
on which to compare departures from
normal was lacking. But this served as a
working hypothesis or subsequently
became established fact after definitive
research

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

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

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

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


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

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


Milo Hellman
Hellman showed the racial variation in so called
normal occlusion through anthropological
studies.
Hellman and others studied the prognathism of
the human dentition in relation to a cranial base
Stages of Dental development Hellman
IIA Eruption of 2nd deciduous molar
IIC Eruption of permanent incisor
IIIA Eruption of permanent 1st molar
IIIB Eruption of canines and premolar
IIIC Beginning of 2nd molar eruption
IVA Eruption of 2nd molar completed
VA (Adult) eruptionwww.indiandentalacademy.com
of 3rd molar completed

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


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

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

Occlusion is a dynamic entity show variation according
to age and sex. Most girls by the age of 12 achieve
relatively stable occlusion whereas boys achieve that a
bit later due to continuing growth pattern.
Three components of occlusion can be summed up as
1.

Occlusal position (or) tooth contact position
- Masticatory habits, tooth inclination and
malposition, shape of teeth, premature contact,
faulty restoration, tooth loss, the condition of
periodontium affect the occlusal positions

1.

Postural resting position

2.

TMJ

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


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


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

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


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

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

Classification of Occlusion
Based on Mandibular Position
Centric Occlusion
– It is the occlusion of teeth in centric relation. Centric relation has
been defined as the maxillomandibular relationship in which
condyles articulates with the thinnest avascular position of their
respective discs with the complex in the anterosuperior position
against the shape of articular eminence. This position is
independent of tooth contact

The Importance
orthodontics

of

the

centric

relation

in

– In orthodontics, diagnosis and treatment planning should be
performed by an evaluation of an malocclusion with the
mandible in centric relation (CR), i.e. the natural musculoskeletal
position of the condyle in the fossa, in order to obtain the true
maxillary - mandibular skeletal and dental relations in the three
planes of space.

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

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

Key Ridges :
Infrazygomatic crest. This zygomatic pillar ‘key
ridge’ – established during growth directly above the
centre of the roots of the first upper molars and
proceeds along the outside of the wall of the
maxillary cavity upto the zygomatic bone.

Key of Age :
Demonstrates the average drift of upper first molar
downwards and mesially. All angulation show prominent
minus angulation.
-17o : 6 – 7 years
-8o : 11 years
-5o : 17 years

Class I : Neutro Occlusion
Mesiobuccal cusps of the upper first permanent
molar occludes with the mesiobuccal groove of the lower
first permanent molar. This is called the key of occlusion
Class II : Disto Occlusion
Condition in which the mandibular first Permanent
molar is placed posterior in relation to the normal class I
condition
– Division I
– Division II

Class III : Mesio Occlusion
Condition in which the mandibular first Permanent
molar is placed anterior in relation to the normal class I
condition

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


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


BASED ON PATTERN
Cusp to embrasure / Marginal ridge
occlusion : Occlusion of one
supporting cusps into a fossa and the
occlusion of another cusp of the same
tooth into the embrasure area of two
opposing teeth. This is a tooth-to-twoteeth relation.
Cusp to fossa occlusion :
Supporting cusp occluding into fossa.
This produces an interdigitation of the
cusps and fossa of one teeth with the
fossa of only one opposing tooth. This
is tooth-to-one-tooth relation.

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

Centric relation occlusion is the morphologic position
of the mandible in centric relation when the posterior
teeth are intercusped in occlusion.
Centric relation occlusion can only be demonstrated
with axis-oriented casts mounted on an articulator.
II. Uniform contact in centric relation
The elimination of centric prematurities is necessary
to establish uniform contact in centric relation.
There are four possible effects of the fulcruming
effect of premature centric contacts as follows :
–
–
–
–

Faceting and wear
TMJ Dysfunction
Infrabony periodontal bone loss
Recession and gingival erosion

III. Cusp-Fossa Occlusion
Cusp-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 of
occlusion”.
This design lends much stability and a reciprocation of forces to the
occlusion
Cusps-fossa relations are always preferable to cusp-embrasure
occlusion, but are not always achievable.
IV. Primary Marginal Ridge Contacts
This is a sagittal plane projection. Contact on the distal incline of the
upper mesial marginal ridges against the mesial marginal ridge of the
lower buccal cusp. The distal marginal ridge of the upper lingual cusp
has a similar contact with the mesial incline of the opposing distal
marginal ridge.
If posterior teeth are lost and the vertical dimension decreases, the
upper anterior teeth will be splayed. When posterior teeth are present,
they prevent wear and possible separation of the front teeth.

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

VIII. Narrow Occlusal table
Natural teeth with little wear have narrow occlusal
tables.
If the occlusal table is kept small the forces of
closure will be kept within the perimeter of teeth and
directed in the long axis.
IX. Maximum Cusp Height and Fossa Depth
Teeth with tallest cusps offer greatest shear
efficiency.
Determinants of cusps height
– Angle of eminence
– Transtrution

– Vertical laterotrusion of the workin condyle
– Inclination of the occlusal plane

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

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

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

VERTICAL DETERMINANT
Condylar
guidance

Steeper

Taller the Posterior Cusps

Greater the Vertical
overlap

Taller the Posterior Cusps

Greater the Horizontal
overlap

Shorter the Posterior cusps

Plane of
Occlusion

More parallel the plane to
condylar guidance


Curve of
Spee

More acute


Greater


Anterior
guidance

Lateral
translation
movement

Greater the immediate side
shift
More superor the
movement of rotating
condyle



HORIZONTAL DETERMINANT
Distance from
rotating condyle
Distance from
midsagittal plane
Lateral
translation
movement
Intercondylar
distance

Greater

Wider the angle between
laterotrusive and
Mediotrusive pathways

Greater

laterotrusive and

Greater

laterotrusive and

Greater

Smaller the angle between
laterotrusive and


ORTHODONTIC TREATMENT OBJECTIVES
The orthodontic treament objectives are to provide
good facial esthetics, and an ideal, static and
functional occlusion.
The static objectives and Andrews’ Six Keys to
Normal Occlusion.
The functional objectives are obtained with the
mutually protected occlusion, which present the
following characteristics
1. The teeth should present maximum intercuspation

with the mandible in CR
2. In CR, all posterior teeth should present effective

occlusal contacts through their long axes and the
anterior teeth should present a 0.005 inch clearance

3.

During lateral functional movements of the
mandible, the cuspid should disclude all
posterior teeth, (cuspid guidance)

4.

During protrusion, the six upper anterior teeth
should articulate with the six lower anterior
teeth and first or second premolars (in first
premolars extraction cases) in order to
disclude all the posterior teeth.

5.

There should be no balancing side
intereferences. This relation of the anterior
teeth is known as anterior guidance

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

Leader in continuing dental education


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