ANATOMY AND
DEVELOPMENT OF
OCCLUSION
INDIAN DENTAL ACADEMY
Leader in continuing dental education
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DEFINITION OF OCCLUSION
SKELETAL COMPONENT
JOINTS, LIGAMENTS AND MUSCLES
DENTAL COMPONENT
Development of teeth
Anatomical ...
DEFINITION OF OCCLUSION

Dorland’s medical dictionary – act of
closure or state of being closed

In dentistry – Relationsh...
To have a good understanding of
occlusion and its development it is essential
to have a proper understanding of the
mastic...
SKELETAL
COMPONENT

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Three major skeletal components make up the
masticatory system
MAXILLA
MANDIBLE
TEMPORAL BONE

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MAXILLA
 Develops from the 1st Branchial arch at
about the 4th week of intrauterine life.
 It is by intra membranous oss...
The growth takes place by two mechanism –
sutural growth and surface apposition.
 Growth sites in the maxilla
o Maxillar...
 Superiorly it forms the floor of the nasal
cavity and the floor of each orbit
 Inferiorly it forms the palate and the
a...
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MANDIBLE
 Develops from the 1st Branchial arch at
about the 4th week of intrauterine life.
 It is derived from the Mecke...
 The growth sites in the mandible
o Mandibular condyle
o Posterior border of Ramus
o Alveolar process
o Lower border of t...
 It is a U-shaped bone which supports the
lower teeth and makes up the lower facial
skeleton.
 It is suspended below the...
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TEMPORAL BONE
 The mandibular condyle articulates at the base of the
cranium with the squamous portion of the temporal
bo...
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JOINTS, LIGAMENTS
AND MUSCLES

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The joint which plays an important role
in the masticatory system is the Temporomandibular joint.
Formed by the articulati...
The ligaments in conjunction with the joint are
1. Collateral ligament
2. Capsular ligament
3. Temporo-mandibular ligament...
The skeletal components of the
masticatory system are supported and brought
into function with the help of four pairs of
m...
Masseter

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Temporalis

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Lateral and medial
pterygoids

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The masseter, temporalis and medial
pterygoid are responsible for closure of the
mandible
The lateral pterygoid is respons...
DENTAL
COMPONENT

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The human dentition comprises of two
stages : a stage of deciduous dentition and a
stage of permanent dentition.
The decid...
Deciduous dentition
 Comprises of 20 teeth equally distributed in
the upper and lower jaws
 Based on their morphology an...
Permanent dentition
 Comprises of 32 teeth equally distributed in
the maxillary and mandibular jaws
 Based on their morp...
Development of teeth
Teeth are developed from the dental lamina
6 weeks intra uterine life – basal cells of oral
epitheliu...
Bud stage
The epithelium of the dental lamina is separate from
the underlying ectomesenchyme by a basement membrane.
From ...
The dental papilla and the tooth bud
together is surrounded by the dental sac.
The dental papilla forms the tooth pulp
and...
Cap stage
The tooth bud continues to proliferate in an
unequal growth in different parts to form the
cap stage
1) Outer an...
3. Dental papilla : The ectomesenchyme (neural
crest cells) that is enclosed by the invaginated
portion of the inner ename...
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Bell stage
As the invagination of the epithelium deepens
and its margins continue to grow, the enamel
organ assumes a bell...
3) Stellate reticulum: increase in intercellular
fluid and it expands. Star shaped cells are
seen.
4) Outer enamel epithel...
Dental papilla
The dental papilla is enclosed in the invaginated
portion of the enamel organ. Prior to enamel formation
by...
Dentinogenesis and Amelogenesis
After the differentiation of the cells of the dental
papilla and the inner enamel epitheli...
Hertwig’s Epithelial Root Sheath
 Formation of root begins after enamel and dentin
formation has reached the future C.E j...
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Anatomical
features in brief of
individual groups
of teeth
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Permanent Incisors
Human incisors have thin, blade-like crowns
which are adapted for the cutting and shearing of
food. The...
Facial: It is the most
prominent tooth in the
mouth. It has a nearly
straight incisal edge
and a gracefully curved
cervica...
Lingual: The lingual
aspect presents a
distinctive
lingual
fossa that is bordered
by mesial and distal
marginal ridges, th...
Proximal: Mesial and
distal aspects present
a
distinctive
triangular
outline.
This is true for all of
the
incisors.
The
in...
Incisal: The crown is
roughly triangular in
outline; the incisal
edge is nearly a
straight line, though
slightly
crescent
...
Contact Points: The mesial contact point is just about at the
incisal, owing to the very sharp mesial incisal angle. The d...
Facial: The maxillary lateral
incisor resembles the central
incisor, but is narrower
mesio-distally. The mesial
outline
re...
Lingual: On the lingual
surface,
the
marginal
ridges
are
usually
prominent and terminate
into
a
prominent
cingulum. There ...
Proximal: In proximal
view, the maxillary
lateral
incisor
resembles the central
except that the root
appears longer--about...
Incisal: In incisal view,
this
tooth
can
resemble either the
central or the canine
to varying degrees.
The tooth is narrow...
Contact Points: The mesial contact is at the junction of the
incisal third and the middle third. The distal contact is is
...
Facial: The mandibular
central incisor is the
smallest tooth in the
dental arch. It is a
long,
narrow,
symmetrical
tooth.
...
Lingual: The lingual
surface
has
no
definate
marginal
ridges. The surface is
concave
and
the
cingulum is minimal
in size.
...
Proximal: Both mesial
land distal surfaces
present a triangular
outline. The incisal
ridge of the crown is
aligned on the ...
Incisal: The incisal edge
is at right angles to a
line
passing
labiolingually
through the tooth
reflecting its bilateral
s...
Contact Points: The mesial and distal contacts are at the
junction of the incisal third and the middle third.
Variation: T...
Facial:
This
tooth
resembles the central
incisor,
but
is
somewhat larger in
most proportions. It is a
more rounded tooth;
...
Lingual: Except for the
lack of symmetry,
this tooth resemble
the central.

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Proximal:
Like
the
central, the crown
presents a triangular
outline. When viewed
critically, the rotation
of the incisal e...
Incisal: The incisal edge
'twisted' from the 90
degree angle with a
line
passing
labiolingually
through the tooth.

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Contact Points: The mesial and distal contacts are at the
junction of the incisal third and the middle third.

Variation: ...
Permanent Canine
Human canines are the longest and most stable of
teeth in the dental arch. Only one tooth of this class i...
Facial:
The
canine
is
approximately 1 mm narrower
than the central incisor. Its
mesial aspect resembles the
adjacent later...
Lingual: Distinct mesial
and distal marginal
ridges,
a
welldeveloped
cingulum,
and the cusp ridges
form the boundaries of
...
Proximal: The mesial
and distal aspects
present a triangular
outline.
They
resemble the incisors,
but are more robust-espe...
Incisal: The asymmetry
of this tooth is readily
apparent from this
aspect. It usually
thicker labiolingually
than
it
is
me...
Contact point: The mesial contact point is at the
junction of the incisal and middle third. Distally, the
contact is situa...
Facial: The mandibular canine is
noticeably narrower mesiodistally
than the upper, but the root may be
as long as that of ...
Lingual: The marginal
ridges and cingulum
are less prominent
than those of the
maxillary canine. The
lingual surface is
sm...
Proximal: The mesial and
distal aspects present a
triangular outline. The
cingulum as noted is
less well developed.
When t...
Incisal: The mesiodistal
dimension is clearly less
than the labiolingual
dimension. The mesial
and distal 'halves' of the
...
Contact point: The mesial contact point is at the
junction of the incisal and middle third. Distally, the
contact is situa...
Premolar
The premolar teeth are transitional teeth
located between the canine and molar teeth. There
are two premolars per...
Facial:
The
buccal
surface
is
quite
rounded and this
tooth resembles the
maxillary canine. The
buccal cusp is long;
from t...
Lingual: The lingual
cusp is smaller and
the tip of that cusp is
shifted toward the
mesial. The lingual
surface is rounded...
Proximal: The mesial aspect
of this tooth has a
distinctive concavity in
the cervical third that
extends onto the root. It...
Occlusal: There are two
well-defined
cusps
buccal and lingual. The
larger cusp is the buccal;
its cusp tip is located
midw...
Contact Points; Height of Curvature: The distal contact
area is located more buccal than is the mesial contact area.
Both ...
Facial: This tooth closely
resembles
the
maxillary
first
premolar but is a less
defined copy of its
companion to the
mesia...
Lingual: Again, this
tooth resembles the
first. The lingual
cusp, however, is
more nearly as large
as the buccal cusp.

ww...
Proximal: Mesial and
distal surfaces are
rounded. The mesial
developmental
depression
and
mesial marginal ridge
are not pr...
Occlusal: The crown
outline is rounded,
ovoid, and is less
clearly defined than
is the first.

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Contact Points; Height of Curvature: When viewed from
the facial, the distal contact area is located more cervically
than ...
Facial: The outline is
very
nearly
symmetrical
bilaterally,
displaying a large,
pointed buccal cusp.
From it descends a
la...
Lingual: This tooth has
the smallest and most
ill-defined
lingual
cusp of any of the
premolars.
A
distinctive feature is
t...
Proximal:
The
large
buccal cusp tip is
centered over the root
tip, about at the long
axis of this tooth. The
very large bu...
Occlusal: The occlusal outline
is
diamond-shaped.
(Review
of
premolar
occlusal outlines: the upper
first is hexagonal, the...
Contact Points; Height of Curvature: When viewed from the
facial, each contact area/height of curvature is at about the
sa...
Facial: From this aspect,
the tooth somewhat
resembles the first,
but the buccal cusp is
less pronounced. The
tooth is lar...
Lingual: Two significant
variations are seen in
this view. The most
common is the threecusp form which has
two lingual cus...
Proximal: The buccal
cusp is shorter than
the first. The lingual
cusp (or cusps) are
much
better
developed than the
first ...
Occlusal: The two or three
cusp versions become
clearly evident. In the
three-cusp version, the
developmental
grooves
pres...
Contact Points; Height of Curvature: From the facial,
the mesial contact is more occlusal than the distal
contact. Why? Th...
Permanent Molar Teeth
The permanent molars occupy the most
posterior portion of the dental arch. They have the
largest occ...
Facial: The mesiobuccal
and distobuccal cusps
dominate the facial
outline. They are
separated
by
the
buccal developmental
...
Lingual: Two cusps of
unequal size dominate the
occlusal profile. The cusps
are separated by the
lingual
developmental
gro...
Proximal:
In
mesial
perspective
the
mesiolingual
cusp,
mesial marginal ridge,
and mesiobuccal cusp
comprise the occlusal
o...
Occlusal: The tooth outline is
somewhat rhomboidal with
four distinct cusps. The cusp
order according to size is:
mesiolin...
Contact Points; Height of Curvature: The mesial
contact is above, but close to, the mesial marginal ridge.
It is somewhat ...
Facial: The crown is shorter
occluso-cervically and narrower
mesiodistally when compared
to the first molar. The
distobucc...
Lingual:
The
distolingual cusp is
smaller
than
the
mesiolingual
cusp.
The Carabelli trait is
absent.

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Proximal: The crown is
shorter than the first
molar and the palatal
root
has
less
divergence. The roots
tend to remain wit...
Occlusal: The distolingual
cusp is smaller on the
second than on the first
molar. When it is much
reduced in size, the cro...
Contact Points: Height of Curvature: Both mesial and
distal contacts tend to be centered buccolingually below the
marginal...
Facial: The crown is
usually shorter in
both
axial
and
mesiodistal
dimensions.
Two
buccal
roots
are
present, but in most
c...
Lingual: In most thirds,
there is just one large
lingual cusp. In some
cases there is a poorly
developed
distolingual cusp...
Proximal: The outline of
the crown is rounded;
it is often described
as bulbous in dental
literature.
Technically,
the
mes...
Occlusal: The crown of
this tooth is the
smallest
of
the
maxillary molars. The
first molar is the
largest in the series.
T...
Contact Points; Height of Curvature: This tooth is rounded
and variable in shape. The distal surface has no contact with
a...
Facial: The lower first permanent molar has the
widest mesiodistal diameter of all of the
molar teeth. Three cusps cusps s...
Lingual: Three cusps make
up the occlusal profile in
this
view:
the
mesiolingual,
the
distolingual, and the
distal cusp wh...
Proximal: The distinctive height
of curvature seen in the
cervical third of the buccal
surface is called the cervical
ridg...
Occlusal: This tooth
presents a pentagonal
occlusal outline that
is distinctive for this
tooth. There are five
cusps. Of t...
Contact Points; Height of Curvature: The mesial contact is
centered buccolingually just below the marginal ridge. The
dist...
Facial: When compared to
the first molar, the
second molar crown is
shorter
both
mesiodistally and from
the cervix to the ...
Lingual: The crown is
shorter than that of
the first molar. The
occlusal outline is
formed
by
the
mesiolingual
and
distoli...
Proximal: The mesial
profile resembles that
of the first molar. The
distal
profile
is
formed
by
the
distobuccal
cusp,
dist...
Occlusal: There are four
well developed cusps
with developmental
grooves that meet at a
right angle to form
the distinctiv...
Contact Points; Height of Curvature: When moving distally
from first to third molar, the proximal surfaces become
progress...
Facial: The crown is
often short and has a
rounded outline.

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Lingual: Similarly, the
crown is short and
the crown is bulbous.

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Proximal: Mesially and
distally, this tooth
resembles the first and
second molars. The
crown of the third
molar, however, ...
Occlusal: Four or five
cusps may be present.
This surface can be a
good copy of the first or
second molar, or poorly
devel...
Contact Points; Height of Curvature: The rounded mesial
surface has its contact area more cervical than any other
lower mo...
DEVELOPMENT
OF
OCCLUSION
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SEQUENCE OF ERUPTION
TIME OF ERUPTION
PATH OF ERUPTION
STAGES OF DEVELOPMENT OF OCCLUSION

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SEQUENCE OF ERUPTION

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Primary dentition
Central incisor
Lateral incisor
First molar
Canine
Second molar

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Permament dentition
First molars
Central incisor
Lateral incisor
Mandibular canines
First premolars
Second premolars
Maxil...
TIME OF ERUPTION

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Maxillary

Mandibular

Deciduous
Tooth

Eruption

Root
complete

Eruption

Root
complete

A

7½

10

6

8

B

9

11

7

13...
Maxillary

Mandibular

Permanent
Tooth

Eruption

Root
complete

Eruption

Root
complete

CI

7-8

10

6-7

9

LI

8-9

11...
PATH OF ERUPTION
(Permanent dentition)

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Mandibular Permanent Incisor
 Permanent central incisors develop lingually and apically
to the primary incisors
 Permane...
Maxillary Permanent Incisor
 Eruption takes place after the mandibular lateral
has erupted
 Central incisor precedes lat...
Mandibular Permanent Canines
 During the eruption, the axis is directed
mesially and lingually
 The permanent cuspids er...
Maxillary Permanent Canines
 This is the last tooth to erupt anterior to the

molars in this arch
As they erupt, they ar...
Mandibular and Maxillary First Premolars
 It develops beneath the first primary molar and is
enclosed by its roots
 The ...
Mandibular Second Premolars
 Last tooth to erupt anterior to the first molar
 There are three possible paths
 Distal pa...
 Mesial path of eruption – Least desirable path
of eruption. This occurs owing to the blocking out
of space for the 2nd p...
Mandibular First Permanent Molar
 The first permanent teeth to erupt
 Prior to eruption, the crowns are canted mesially ...
Maxillary First Permanent Molar
 The Crowns are distally and buccally oriented in their
crypts.
 As the maxillary arch g...
Mandibular Second Permanent Molar
 Crypts positioned at base of the ascending ramus
 Space for eruption is gained by res...
Maxillary Second Permanent Molar
 Position in crypt and pathway of eruption is similar to the
1st permanent molar
 Mesio...
STAGES OF
DEVELOPMENT OF
OCCLUSION
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Stage

Age in years

Characteristics

First stage

3

Second stage

6

Eruption of 1st
permanent molar

Third stage

6–9

...
PRIMARY DENTITION

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Primary tooth buds form at 6 weeks IUL
Commence erupting at 6 months post birth and
goes upto 2 ½ years of age when the ...
Spaces in primary dentition
Primate space – mesial to maxillary canine,
distal to mandibular canine

Developmental space –...
Occlusal relationship of 2nd primary molars
 Eruption and root completion of the 2nd primary molar
marks the completion o...
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Size of the dental arch
 Size can be measured by the dental arch width
between the primary canines and between the 2 nd
p...
ERUPTION OF 1ST
PERMANENT MOLAR

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1st permanent molar is the key to the permanent
occlusion
The prediction of the occlusion of the 1st permanent
molars is k...
Some cases of Flush terminal plane go in for
CLASS III when physiologic spaces are absent
in the mandible
The active gro...
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EXCHANGE OF INCISORS

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 This commences after the eruption of the 1st molar
begins
 Total sum of the mesiodistal widths of permanent
incisors is...
EXCHANGE OF
LATERAL TEETH
(Canines and Premolars)

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 Limited by the mesial surface of the 1st molar distally
and distal surface of the lateral incisor
 Two factors permit s...
b)Order of exchange – Eruption pattern sequences usually
seen are 3-4-5, 4-3-5, 4-5-3
In the mandible it is usually 3-4-5 ...
ERUPTION OF 2ND
PERMANENT MOLARS

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 Occurs after the eruption of all the permanent teeth in
the dental arch upto the 1st permanent molar is complete
 Its e...
DETERMINANTS
OF OCCLUSAL
MORPHOLOGY
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Posterior controlling factor (Condylar guidance)
Anterior controlling factor (Anterior
guidance)
Vertical determinants
1. ...
Posterior controlling factor
(Condylar guidance)

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 As the condyle moves out of centric relation it
descends along the articular eminence
 If the articular eminence is ste...
 The CGA is steeper for the orbiting condyle in a
latero-trussive movement of the mandible as the
medial wall of the mand...
Anterior controlling factor
(Anterior guidance)

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 The anterior teeth guide the movement of the
anterior portion of the mandible
 As the mandible protrudes, the incisal e...
Vertical determinants

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1. Effect of condylar guidance on cusp height

Steeper the articular
eminence, more is
the descent of the
condyle, resulti...
2. Effect of anterior guidance on cusp height
Increased horizontal overlap decreases
the anterior guidance angle. There is...
Increased vertical overlap increases the
anterior guidance angle. There is more vertical
movement of the mandible leading ...
3. Effect of plane of occlusion on cusp
height
 Plane of occlusion is an imaginary line touching
the incisal edges of the...
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4. Effect of curve of spee on cusp height
 Curve of spee is an antero - posterior curve
extending from the tip of the man...
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 Orientation of the curve of spee also
influences cusp height
 Radius perpendicular to horizontal reference
plane
Poster...
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5. Effect of mandibular lateral translation
movement on cusp height
 This is a bodily sideshift of the mandible where
the...
 The amount of lateral translation depends on the
tightness of the inner horizontal portion of the TM
ligament attached t...
 The time of lateral translation is of great influence on
occlusal morphology. If late, there is less influence as the
ma...
Horizontal determinants

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1. Effect of distance from the rotating condyle
Increased distance – wider angle between
laterotrussive and mediotrussive ...
2. Effect of distance from midsagittal plane
Increased distance – wider angle between
laterotrussive and mediotrussive pat...
3. Effect of distance from rotating condyle and
fossa from midsagittal plane
They generally counter act each other. The
co...
4. Effect of mandibular lateral translation movement
Increased lateral movement, increases the angle
between laterotrussiv...
5. Effect of intercondylar distance
Increase in distance, reduces the angle
between laterotrussive and mediotrussive
pathw...
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Anatomy and dev of occlusion /orthodontic courses training by indian dental academy

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Welcome to Indian Dental Academy
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Anatomy and dev of occlusion /orthodontic courses training by indian dental academy

  1. 1. ANATOMY AND DEVELOPMENT OF OCCLUSION INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.com
  2. 2. DEFINITION OF OCCLUSION SKELETAL COMPONENT JOINTS, LIGAMENTS AND MUSCLES DENTAL COMPONENT Development of teeth Anatomical features in brief of individual groups of teeth DEVELOPMENT OF OCCLUSION DETERMINANTS OF OCCLUSAL MORPHOLOGY www.indiandentalacademy.com
  3. 3. DEFINITION OF OCCLUSION Dorland’s medical dictionary – act of closure or state of being closed In dentistry – Relationship of maxillary and mandibular teeth when they are in functional contact during activity of the mandible. www.indiandentalacademy.com HOME
  4. 4. To have a good understanding of occlusion and its development it is essential to have a proper understanding of the masticatory system. The masticatory system comprises a) Skeletal component b) Joints, ligaments and muscles and c) Dental component. www.indiandentalacademy.com HOME
  5. 5. SKELETAL COMPONENT www.indiandentalacademy.com
  6. 6. Three major skeletal components make up the masticatory system MAXILLA MANDIBLE TEMPORAL BONE www.indiandentalacademy.com HOME
  7. 7. MAXILLA  Develops from the 1st Branchial arch at about the 4th week of intrauterine life.  It is by intra membranous ossification of the fronto-nasal and maxillary processes.  Two maxillae are formed in this way which are fused together in the mid-palatine suture. www.indiandentalacademy.com HOME
  8. 8. The growth takes place by two mechanism – sutural growth and surface apposition.  Growth sites in the maxilla o Maxillary tuberosity o Sutures o Alveolar border o Nasal septum o Lateral walls www.indiandentalacademy.com HOME
  9. 9.  Superiorly it forms the floor of the nasal cavity and the floor of each orbit  Inferiorly it forms the palate and the alveolar ridges which support the teeth.  As the maxillary bones are intricately fused to the skull, the maxillary teeth make up the stationary components of the masticatory system. www.indiandentalacademy.com HOME
  10. 10. www.indiandentalacademy.com HOME
  11. 11. MANDIBLE  Develops from the 1st Branchial arch at about the 4th week of intrauterine life.  It is derived from the Meckel’s cartilage.  The lower part of the body of the mandible by membranous ossification  The ramus and processes by cartilaginous ossification. HOME www.indiandentalacademy.com
  12. 12.  The growth sites in the mandible o Mandibular condyle o Posterior border of Ramus o Alveolar process o Lower border of the mandible o Suture {at the suture between the two halves of the mandible fibrous connective tissue (symphyseal cartilage) serves as a growth site} www.indiandentalacademy.com HOME
  13. 13.  It is a U-shaped bone which supports the lower teeth and makes up the lower facial skeleton.  It is suspended below the maxilla by muscles, ligaments and other soft tissues.  The condyle articulates with the cranium around which movement occurs making it the moveable component of the masticatory system. www.indiandentalacademy.com HOME
  14. 14. www.indiandentalacademy.com HOME
  15. 15. TEMPORAL BONE  The mandibular condyle articulates at the base of the cranium with the squamous portion of the temporal bone in the concave mandibular fossa called articular or glenoid fossa.  Immediately anterior to the mandibular fossa is a convex bony prominence called the articular eminence.  The posterior roof of the glenoid fossa is thin and not suitable to sustain heavy forces, however, the articular eminence consists of dense bone which can. www.indiandentalacademy.com HOME
  16. 16. www.indiandentalacademy.com HOME
  17. 17. JOINTS, LIGAMENTS AND MUSCLES www.indiandentalacademy.com HOME
  18. 18. The joint which plays an important role in the masticatory system is the Temporomandibular joint. Formed by the articulating surface of the condyles of the mandible and the articular fossa (bilaterally) of the temporal bone. www.indiandentalacademy.com HOME
  19. 19. The ligaments in conjunction with the joint are 1. Collateral ligament 2. Capsular ligament 3. Temporo-mandibular ligament 4. Spheno-mandibular ligament 5. Stylo-mandibular ligament www.indiandentalacademy.com HOME
  20. 20. The skeletal components of the masticatory system are supported and brought into function with the help of four pairs of muscles called the muscles of mastication; masseter, temporalis, medial pterygoid and lateral pterygoid muscles. www.indiandentalacademy.com HOME
  21. 21. Masseter www.indiandentalacademy.com HOME
  22. 22. Temporalis www.indiandentalacademy.com HOME
  23. 23. Lateral and medial pterygoids www.indiandentalacademy.com HOME
  24. 24. The masseter, temporalis and medial pterygoid are responsible for closure of the mandible The lateral pterygoid is responsible for opening of the mandible. Along with these muscles the digastric muscle also acts in the functioning of the masticatory system by depressing the mandible. www.indiandentalacademy.com HOME
  25. 25. DENTAL COMPONENT www.indiandentalacademy.com
  26. 26. The human dentition comprises of two stages : a stage of deciduous dentition and a stage of permanent dentition. The deciduous dentition is made up of 20 teeth and the permanent dentition is made up of 32 teeth. Each tooth comprises of 2 basic parts – the crown and the root The root is attached to the alveolar bone by numerous fibers of connective tissue called the periodontal ligament. www.indiandentalacademy.com HOME
  27. 27. Deciduous dentition  Comprises of 20 teeth equally distributed in the upper and lower jaws  Based on their morphology and function they are classified as incisors, canines and molars.  Each arch is divided into two quadrants, each comprising of 5 teeth in the grouping of 2 incisors, 1 canine and 2 molars. www.indiandentalacademy.com HOME
  28. 28. Permanent dentition  Comprises of 32 teeth equally distributed in the maxillary and mandibular jaws  Based on their morphology and function they are classified as incisors, canines, premolars and molars.  Each arch is divided into two quadrants, each comprising of 8 teeth in the grouping of 2 incisors, 1 canine, 2 premolars and 3 molars. www.indiandentalacademy.com HOME
  29. 29. Development of teeth Teeth are developed from the dental lamina 6 weeks intra uterine life – basal cells of oral epithelium proliferate to form the dental lamina. This serves as the primordium for the ectodermal portion of the tooth. www.indiandentalacademy.com HOME
  30. 30. Bud stage The epithelium of the dental lamina is separate from the underlying ectomesenchyme by a basement membrane. From this basement membrane, round or ovoid swellings called tooth buds (primordia for enamel organ) arise. The enamel organ – peripheral low columnar cells and central polygonal cells. Several cells of the tooth bud and the surrounding mesenchyme undergo mitosis leading to condensation of the ectomesenchymal cells around the tooth bud. The condensed ectomesenchyme subjacent to the HOME enamel organ is the dental papilla www.indiandentalacademy.com
  31. 31. The dental papilla and the tooth bud together is surrounded by the dental sac. The dental papilla forms the tooth pulp and dentin while the dental sac forms the cementum and the periodontal ligament. www.indiandentalacademy.com HOME
  32. 32. Cap stage The tooth bud continues to proliferate in an unequal growth in different parts to form the cap stage 1) Outer and inner enamel epithelium : outer cells are cuboidal and inner cells are tall columnar. 2) Stellate reticulum : Polygonal cells situated in the center of the enamel organ between the outer and inner enamel organ form a network. The inter-cellular spaces are filled with mucoid fluid rich in albumin. www.indiandentalacademy.com HOME
  33. 33. 3. Dental papilla : The ectomesenchyme (neural crest cells) that is enclosed by the invaginated portion of the inner enamel epithelium proliferates to form the dental papilla, which is the formative organ of the dentin and the primordium of the pulp. The peripheral cells of the dental papilla enlarge to and differentiate into odontoblasts. 4. Dental sac : The ectomesenchyme surrounding the enamel organ and the dental papilla undergoes condensation. Here a denser and more fibrous layer develops which forms the primitive dental sac. HOME www.indiandentalacademy.com
  34. 34. HOME www.indiandentalacademy.com
  35. 35. Bell stage As the invagination of the epithelium deepens and its margins continue to grow, the enamel organ assumes a bell shape. Four different types of cells are seen in this stage: 1) Inner enamel epithelium: single layer of cells that differentiate into tall columnar cells called ameloblasts. 2) Stratum intermedium: formed from squamous cells between the inner enamel epithelium and the stellate reticulum. www.indiandentalacademy.com HOME
  36. 36. 3) Stellate reticulum: increase in intercellular fluid and it expands. Star shaped cells are seen. 4) Outer enamel epithelium: cells flatten to a low cuboidal form. www.indiandentalacademy.com HOME
  37. 37. Dental papilla The dental papilla is enclosed in the invaginated portion of the enamel organ. Prior to enamel formation by the inner enamel epithelium, the peripheral cells of the mesenchymal dental papilla differentiate into odontoblasts. Dental sac Before formation of dental tissues commences the dental sac shows a circular arrangement of fibers and resembles a capsular structure. With the development of the root, the fibers of the dental sac differentiate into the periodontal ligament. www.indiandentalacademy.com HOME
  38. 38. Dentinogenesis and Amelogenesis After the differentiation of the cells of the dental papilla and the inner enamel epithelium into the odontoblasts and ameloblasts, respectively, the dentin is laid down first. After the first layer of dentin is laid, only then does amelogenesis commence. www.indiandentalacademy.com HOME
  39. 39. Hertwig’s Epithelial Root Sheath  Formation of root begins after enamel and dentin formation has reached the future C.E junction  HERS consists of the outer and inner enamel epithelium only.  The cells differentiate the radicular cells into odontoblasts and the first layer of dentin is laid down. The root sheath then loses its structural continuity.  Single rooted and multi rooted teeth are formed by tongue like projections from a horizontal diaphragm. www.indiandentalacademy.com HOME
  40. 40. HOME www.indiandentalacademy.com
  41. 41. Anatomical features in brief of individual groups of teeth www.indiandentalacademy.com
  42. 42. Permanent Incisors Human incisors have thin, blade-like crowns which are adapted for the cutting and shearing of food. There are two incisors per quadrant, four per arch. The first incisor, the central incisor, is next to the midline. The second incisor, the lateral incisor, is distal to it. Maxillary incisors by definition arise in the premaxilla; mandibular incisors are the teeth that articulate with them. www.indiandentalacademy.com HOME
  43. 43. Facial: It is the most prominent tooth in the mouth. It has a nearly straight incisal edge and a gracefully curved cervical line. The mesial aspect presents a straight outline; the distal aspect is more rounded. Mamelons are present on freshly erupted, unworn central incisors. www.indiandentalacademy.com HOME
  44. 44. Lingual: The lingual aspect presents a distinctive lingual fossa that is bordered by mesial and distal marginal ridges, the incisal edge, and the prominent cingulum at the gingival third. www.indiandentalacademy.com HOME
  45. 45. Proximal: Mesial and distal aspects present a distinctive triangular outline. This is true for all of the incisors. The incisal ridge of the crown is aligned on the long axis of the tooth along with the apex of the tooth. www.indiandentalacademy.com HOME
  46. 46. Incisal: The crown is roughly triangular in outline; the incisal edge is nearly a straight line, though slightly crescent shaped. www.indiandentalacademy.com HOME
  47. 47. Contact Points: The mesial contact point is just about at the incisal, owing to the very sharp mesial incisal angle. The distal contact point is located at the junction of the incisal third and the middle third. Variation: The maxillary central incisor usually develops normally. Variations include a short crown or, on occasion, and unusually long crown. This tooth is rarely absent. The Hutchinson incisor is a malformation due to congenital syphilis in utero. www.indiandentalacademy.com HOME
  48. 48. Facial: The maxillary lateral incisor resembles the central incisor, but is narrower mesio-distally. The mesial outline resembles the adjacent central incisor; the distal outline--and particularly the distal incisal angle is more rounded than the mesial incisal angle (which resembles that of the adjacent central incisor. The distal incisal angle resembling the mesial of the adjacent canine. www.indiandentalacademy.com HOME
  49. 49. Lingual: On the lingual surface, the marginal ridges are usually prominent and terminate into a prominent cingulum. There is often a deep pit where the marginal ridges converge gingivally. A developmental groove often extends across the distal of the cingulum onto the root continuing for part or all of its length. www.indiandentalacademy.com HOME
  50. 50. Proximal: In proximal view, the maxillary lateral incisor resembles the central except that the root appears longer--about 1 1/2 times longer than the crown. A line through the long axis of the tooth bisects the crown. www.indiandentalacademy.com HOME
  51. 51. Incisal: In incisal view, this tooth can resemble either the central or the canine to varying degrees. The tooth is narrower mesiodistally than the upper central incisor; however, it is nearly as thick labiolingually. www.indiandentalacademy.com HOME
  52. 52. Contact Points: The mesial contact is at the junction of the incisal third and the middle third. The distal contact is is located at the center of the middle third of the distal surface. Variation: This tooth is quite variable. Often the tooth is narrow, conical, and peg-shaped. It is absent either singly or bilaterally in 1-2% of individuals. Only the lower second premolar is more frequently missing. The lingual pit when present can be very deep and is prone to early caries in many individuals. www.indiandentalacademy.com HOME
  53. 53. Facial: The mandibular central incisor is the smallest tooth in the dental arch. It is a long, narrow, symmetrical tooth. The incisal edge is straight. Mesial and distal outlines descend apically from the sharp mesial and distal incisal angles. www.indiandentalacademy.com HOME
  54. 54. Lingual: The lingual surface has no definate marginal ridges. The surface is concave and the cingulum is minimal in size. www.indiandentalacademy.com HOME
  55. 55. Proximal: Both mesial land distal surfaces present a triangular outline. The incisal ridge of the crown is aligned on the long axis of the tooth along with the apex of the tooth. www.indiandentalacademy.com HOME
  56. 56. Incisal: The incisal edge is at right angles to a line passing labiolingually through the tooth reflecting its bilateral symmetry. www.indiandentalacademy.com HOME
  57. 57. Contact Points: The mesial and distal contacts are at the junction of the incisal third and the middle third. Variation: This tooth is consistent in development and is is rarely absent. The upper incisor region is a common site for supernumerary teeth which may occasionally occur in the midline; such a variant is called a mesodens. www.indiandentalacademy.com HOME
  58. 58. Facial: This tooth resembles the central incisor, but is somewhat larger in most proportions. It is a more rounded tooth; this is especially evident in the distal incisal angle in unworn specimens. There is a lack of the bilateral symmetry seen in the central. www.indiandentalacademy.com HOME
  59. 59. Lingual: Except for the lack of symmetry, this tooth resemble the central. www.indiandentalacademy.com HOME
  60. 60. Proximal: Like the central, the crown presents a triangular outline. When viewed critically, the rotation of the incisal edge can be seen. www.indiandentalacademy.com HOME
  61. 61. Incisal: The incisal edge 'twisted' from the 90 degree angle with a line passing labiolingually through the tooth. www.indiandentalacademy.com HOME
  62. 62. Contact Points: The mesial and distal contacts are at the junction of the incisal third and the middle third. Variation: This tooth is stable, but variations in root length and direction are occasionally seen. www.indiandentalacademy.com HOME
  63. 63. Permanent Canine Human canines are the longest and most stable of teeth in the dental arch. Only one tooth of this class is present in each quadrant. In traditional dental literature, canines are considered the cornerstones of the dental arch. They are the only teeth in the dentition with a single cusp. They are especially anchored as prehensile teeth in the group from whence they get their name, the Carnivora. Maxillary canines by definition are the teeth in the maxilla distal, but closest to the incisors. Mandibular canines are those lower teeth that articulate with the mesial aspect of the upper canine. HOME www.indiandentalacademy.com
  64. 64. Facial: The canine is approximately 1 mm narrower than the central incisor. Its mesial aspect resembles the adjacent lateral incisor; the distal aspect anticipates the first premolar proximal to it. The canine is slightly darker and more yellow in the color than the incisor teeth. The labial surface is smooth, with a well developed middle lobe (labial ridge) extending the full length of the crown cervically from the cusp tip. The distal cusp ridge is longer than the mesial cusp ridge. www.indiandentalacademy.com HOME
  65. 65. Lingual: Distinct mesial and distal marginal ridges, a welldeveloped cingulum, and the cusp ridges form the boundaries of the lingual surface. The prominent lingual ridge extends from the cusp tip to the cingulum, dividing the lingual surface into mesial and distal fossae. www.indiandentalacademy.com HOME
  66. 66. Proximal: The mesial and distal aspects present a triangular outline. They resemble the incisors, but are more robust-especially in the cingulum region. www.indiandentalacademy.com HOME
  67. 67. Incisal: The asymmetry of this tooth is readily apparent from this aspect. It usually thicker labiolingually than it is mesiodistally. The tip of the cusp is displaced labially and mesial to the central long axis of this tooth. www.indiandentalacademy.com HOME
  68. 68. Contact point: The mesial contact point is at the junction of the incisal and middle third. Distally, the contact is situated more cervically. It is at the middle of the middle third. Variation: Each of the major features of this tooth are 'variations on a theme.' In some persons, a cusp-like tubercle is found on the cingulum. Lingual pits occur only infrequently. On occasion, the root is unusually long or unusually short. www.indiandentalacademy.com HOME
  69. 69. Facial: The mandibular canine is noticeably narrower mesiodistally than the upper, but the root may be as long as that of the upper canine. In an individual person,the lower canine is often shorter than that of the upper canine. The mandibular canine is wider mesiodistally than either lower incisor. A distinctive feature is the nearly straight outline of the mesial aspect of the crown and root. When the tooth is unworn, the mesial cusp ridge appears as a sort of 'shoulder' on the tooth. The mesial cusp ridge is much shorter than the distal cusp ridge www.indiandentalacademy.com HOME
  70. 70. Lingual: The marginal ridges and cingulum are less prominent than those of the maxillary canine. The lingual surface is smooth and regular. The lingual ridge, if present, is usually rather subtle in its expression. www.indiandentalacademy.com HOME
  71. 71. Proximal: The mesial and distal aspects present a triangular outline. The cingulum as noted is less well developed. When the crown and root are viewed from the proximal, this tooth uniquely presents a crescent-like profile similar to a cashew nut. www.indiandentalacademy.com HOME
  72. 72. Incisal: The mesiodistal dimension is clearly less than the labiolingual dimension. The mesial and distal 'halves' of the tooth are more identical than the upper canine from this perspective. You will recall that the cusp tip of the maxillary canine is facial to a ling through the long axis. In the mandibular canine, the unworn incisal edge is on the line through the long axis of this www.indiandentalacademy.com tooth. HOME
  73. 73. Contact point: The mesial contact point is at the junction of the incisal and middle third. Distally, the contact is situated more cervically. It is at the middle of the middle third. Variation: On occasion, the root is bifurcated near its tip. The double root may, or may not be accompanied by deep depressions in the root. www.indiandentalacademy.com HOME
  74. 74. Premolar The premolar teeth are transitional teeth located between the canine and molar teeth. There are two premolars per quadrant and are identified as first and second premolars. They have at least two cusps. Premolar teeth by definition are permanent teeth distal to the canines preceded by deciduous molars. Utilized in the initial breakdown of food www.indiandentalacademy.com HOME
  75. 75. Facial: The buccal surface is quite rounded and this tooth resembles the maxillary canine. The buccal cusp is long; from that cusp tip, the prominent buccal ridge descends to the cervical line of the tooth. www.indiandentalacademy.com HOME
  76. 76. Lingual: The lingual cusp is smaller and the tip of that cusp is shifted toward the mesial. The lingual surface is rounded in all aspects. www.indiandentalacademy.com HOME
  77. 77. Proximal: The mesial aspect of this tooth has a distinctive concavity in the cervical third that extends onto the root. It is called variously the mesial developmental depression, mesial concavity, or the 'canine fossa'--a misleading description since it is on the premolar. The distal aspect of the maxillary first permanent molar also has a developmental depression. The mesial marginal developmental www.indiandentalacademy.com groove is a distinctive HOME
  78. 78. Occlusal: There are two well-defined cusps buccal and lingual. The larger cusp is the buccal; its cusp tip is located midway mesiodistally. The lingual cusp tip is shifted mesially. The occlusal outline presents a hexagonal appearance. On the mesial marginal ridge is a distinctive feature, the mesial marginal developmental groove. www.indiandentalacademy.com HOME
  79. 79. Contact Points; Height of Curvature: The distal contact area is located more buccal than is the mesial contact area. Both contact points are at the junction of the occlusal and middle third of the tooth. Variation: Most upper first premolars of people in our society have two roots; however, a single root is found in about 20% of teeth. Three rooted premolars are found occasionally. www.indiandentalacademy.com HOME
  80. 80. Facial: This tooth closely resembles the maxillary first premolar but is a less defined copy of its companion to the mesial. The buccal cusp is shorter, less pointed, and more rounded than the first. www.indiandentalacademy.com HOME
  81. 81. Lingual: Again, this tooth resembles the first. The lingual cusp, however, is more nearly as large as the buccal cusp. www.indiandentalacademy.com HOME
  82. 82. Proximal: Mesial and distal surfaces are rounded. The mesial developmental depression and mesial marginal ridge are not present on the second premolar. www.indiandentalacademy.com HOME
  83. 83. Occlusal: The crown outline is rounded, ovoid, and is less clearly defined than is the first. www.indiandentalacademy.com HOME
  84. 84. Contact Points; Height of Curvature: When viewed from the facial, the distal contact area is located more cervically than is the mesial contact area. Variation: The occlusal anatomy is more variable in the second than in the first. There is wide variability is root size, curvature, and form. www.indiandentalacademy.com HOME
  85. 85. Facial: The outline is very nearly symmetrical bilaterally, displaying a large, pointed buccal cusp. From it descends a large, well developed buccal ridge. www.indiandentalacademy.com HOME
  86. 86. Lingual: This tooth has the smallest and most ill-defined lingual cusp of any of the premolars. A distinctive feature is the mesiolingual developmental groove. (Remember the mesial marginal developmental groove in the upper first premolar? That one is mesial. The one on the lower is toward the lingual.) www.indiandentalacademy.com HOME
  87. 87. Proximal: The large buccal cusp tip is centered over the root tip, about at the long axis of this tooth. The very large buccal cusp and much reduced lingual cusp are very evident. You should keep in mind that the mesial marginal ridge is more cervical than the distal contact ridge; each anticipate the shape of their respective adjacent www.indiandentalacademy.com teeth. HOME
  88. 88. Occlusal: The occlusal outline is diamond-shaped. (Review of premolar occlusal outlines: the upper first is hexagonal, the upper second is ovoid, the lower first is diamond, and the lower second is square.) The large buccal cusp dominates the occlusal surface. Marginal ridges are well developed and the mesiolingual developmental groove is consistently present. There are mesial and distal fossae with pits, affectionately www.indiandentalacademy.com known as 'snake eyes' when HOME
  89. 89. Contact Points; Height of Curvature: When viewed from the facial, each contact area/height of curvature is at about the same height. Variation: This is a variable tooth in both crown and root. It may, in some persons, more nearly resemble the lower second premolar. www.indiandentalacademy.com HOME
  90. 90. Facial: From this aspect, the tooth somewhat resembles the first, but the buccal cusp is less pronounced. The tooth is larger than the first. www.indiandentalacademy.com HOME
  91. 91. Lingual: Two significant variations are seen in this view. The most common is the threecusp form which has two lingual cusps. The mesial of those is the larger of the two. The other form is the two-cusp for with a single lingual cusp. In that variant, the lingual cusp tip is shifted to the mesial. www.indiandentalacademy.com HOME
  92. 92. Proximal: The buccal cusp is shorter than the first. The lingual cusp (or cusps) are much better developed than the first and give the lingual a full, welldeveloped profile. www.indiandentalacademy.com HOME
  93. 93. Occlusal: The two or three cusp versions become clearly evident. In the three-cusp version, the developmental grooves present a distinctive 'Y' shape and have a central pit. In the two cusp version, a single developmental groove crosses the transverse ridge from mesial to distal. (Review: the lower second premolar is larger than the first, while the upper first premolar is just slightly www.indiandentalacademy.com HOME
  94. 94. Contact Points; Height of Curvature: From the facial, the mesial contact is more occlusal than the distal contact. Why? The distal marginal ridge is lower than the mesial marginal ridge. Variation: There may be one or two lingual cusps. This tooth is sometimes missing; only the third molars and upper lateral incisors are missing more frequently than this tooth. www.indiandentalacademy.com HOME
  95. 95. Permanent Molar Teeth The permanent molars occupy the most posterior portion of the dental arch. They have the largest occlusal surfaces of any of the teeth and have from three to five major cusps. Molar teeth by definition are cheek teeth that are NOT preceded by primary teeth. Permanent molars are accessional teeth without primary predecessors. In contrast to the molars, permanent incisors, canines, and premolars are succedaneous (successional teeth). These teeth are important in chewing and maintaining the vertical dimension. www.indiandentalacademy.com HOME
  96. 96. Facial: The mesiobuccal and distobuccal cusps dominate the facial outline. They are separated by the buccal developmental groove. All three roots are visible. The buccal roots present a 'plier handle' appearance with the large lingual root centered between them. www.indiandentalacademy.com HOME
  97. 97. Lingual: Two cusps of unequal size dominate the occlusal profile. The cusps are separated by the lingual developmental groove which is continuous with the distolingual (or distal oblique) groove. The larger mesiolingual cusp often displays the Carabelli trait. It is a variable feature. It appears most often as a cusp of variable size, but is occasionally expressed merely as a pit. www.indiandentalacademy.com HOME
  98. 98. Proximal: In mesial perspective the mesiolingual cusp, mesial marginal ridge, and mesiobuccal cusp comprise the occlusal outline. When present, the Carabelli trait is seen in this view. In its distal aspect, the two distal cusps are clearly seen; however, the distal marginal ridge is somewhat shorter than the mesial one. A small concavity on the distal surface that continues www.indiandentalacademy.com onto the distobuccal root HOME
  99. 99. Occlusal: The tooth outline is somewhat rhomboidal with four distinct cusps. The cusp order according to size is: mesiolingual, mesiobuccal, distobuccal, and distolingual. The tips of the mesiolingual, mesiobuccal, and distobuccal cusps form the trigon, reflecting the evolutionary origins of the maxillary molar. The distolingual cusp is called the talon (heel) and is a more recent acquisition in evolutionary history. A frequent feature of maxillary molars is the Carabelli trait www.indiandentalacademy.com located on the mesiolingual HOME
  100. 100. Contact Points; Height of Curvature: The mesial contact is above, but close to, the mesial marginal ridge. It is somewhat buccal to the center of the crown mesiodistally. The distal contact is similarly above the distal marginal ridge but is centered buccolingually. Variation: Deviation from the accepted normal is infrequent. The Carabelli trait is a variable feature. It is of special interest to the dental anthropologist in tracing human evolutionary history. www.indiandentalacademy.com HOME
  101. 101. Facial: The crown is shorter occluso-cervically and narrower mesiodistally when compared to the first molar. The distobuccal cusp is visibly smaller than the mesiobuccal cusp. The two buccal roots are more nearly parallel. The roots are more parallel; the apex of the mesial root is on line with the with the buccal developmental groove. Mesial and distal roots tend to be about the same length. www.indiandentalacademy.com HOME
  102. 102. Lingual: The distolingual cusp is smaller than the mesiolingual cusp. The Carabelli trait is absent. www.indiandentalacademy.com HOME
  103. 103. Proximal: The crown is shorter than the first molar and the palatal root has less divergence. The roots tend to remain within the crown profile. www.indiandentalacademy.com HOME
  104. 104. Occlusal: The distolingual cusp is smaller on the second than on the first molar. When it is much reduced in size, the crown outline is described as 'heart-shaped.' The Carabelli trait is usually absent. The order of cusp size, largest to smallest, is the same as the first but is more exaggerated: mesiolingual, mesiobuccal, distobuccal, and distolingual. www.indiandentalacademy.com HOME
  105. 105. Contact Points: Height of Curvature: Both mesial and distal contacts tend to be centered buccolingually below the marginal ridges. Since the molars become shorter, moving from first to this molar, the contacts tend to appear more toward the center of the proximal surfaces. Variation: The distolingual cusp is the most variable feature of this tooth. When it is large, the occlusal is somewhat rhomboidal; when reduced in size the crown is described as triangular or 'heart-shaped.' At times, the root may be fused. www.indiandentalacademy.com HOME
  106. 106. Facial: The crown is usually shorter in both axial and mesiodistal dimensions. Two buccal roots are present, but in most cases they are fused. The mesial buccal cusp is larger than the distal buccal cusp. www.indiandentalacademy.com HOME
  107. 107. Lingual: In most thirds, there is just one large lingual cusp. In some cases there is a poorly developed distolingual cusp and a lingual groove. The lingual root is often fused to the to buccal cusps. www.indiandentalacademy.com HOME
  108. 108. Proximal: The outline of the crown is rounded; it is often described as bulbous in dental literature. Technically, the mesial surface is the only 'proximal' surface. The distal surface does not contact another tooth. www.indiandentalacademy.com HOME
  109. 109. Occlusal: The crown of this tooth is the smallest of the maxillary molars. The first molar is the largest in the series. The outline of the occlusal surface can be described as heartshaped. The mesial lingual cusp is the largest, the mesial buccal is second in size, and the distal buccal cusp is the smallest. www.indiandentalacademy.com HOME
  110. 110. Contact Points; Height of Curvature: This tooth is rounded and variable in shape. The distal surface has no contact with any other tooth. Variation: They are the most variable teeth in the dentition. Impaction occurs frequently. Some resemble the adjacent second molar; others may have many cusps, small 'cusplets', and many grooves. www.indiandentalacademy.com HOME
  111. 111. Facial: The lower first permanent molar has the widest mesiodistal diameter of all of the molar teeth. Three cusps cusps separated by developmental grooves make up the occlusal outline seen in this view. Moving from mesial to distal, these features form the occlusal outline as follows: mesiobuccal cusp, mesiobuccal developmental groove, distobuccal cusp, distobuccal developmental groove, and the distal cusp. The mesiobuccal cusp is usually the widest of the cusps and is generally considered the largest of the five cusps. The distal cusp is smaller than any of the buccal cusps and it contributes little to the buccal surface. The two roots of this tooth are clearly seen. The distal root is usually less www.indiandentalacademy.com curved than the mesial root. HOME
  112. 112. Lingual: Three cusps make up the occlusal profile in this view: the mesiolingual, the distolingual, and the distal cusp which is somewhat lower in profile. The mesiobuccal cusp is usually the widest and highest of the three. A short lingual developmental groove separates the two lingual www.indiandentalacademy.com cusps HOME
  113. 113. Proximal: The distinctive height of curvature seen in the cervical third of the buccal surface is called the cervical ridge. The mesial surface may be flat or concave in its cervical third . It is highly convex in its middle and occlusal thirds. The occlusal profile is marked by the mesiobuccal cusp, mesiolingual cusp, and the mesial marginal ridge that connects them. The mesial root is the broadest buccolingually of any of the lower molar roots. The distal surface of the crown is narrower buccolingually than the mesial surface. Three cusps are seen from the distal www.indiandentalacademy.com HOME
  114. 114. Occlusal: This tooth presents a pentagonal occlusal outline that is distinctive for this tooth. There are five cusps. Of them, the mesiobuccal cusp is the largest, the distal cusp is the smallest. The two buccal grooves and the single lingual groove form the "Y5" pattern distinctive for this tooth. The five cusp and "Y5" pattern is important in www.indiandentalacademy.com dental anthropology. HOME
  115. 115. Contact Points; Height of Curvature: The mesial contact is centered buccolingually just below the marginal ridge. The distal contact is centered over the distal root, but is buccal to the center point of the distal marginal ridge. Variation: Most lower first molars have five cusps. Occasionally the distal cusp is missing. More rarely, in large molars, the distal cusp is joined by a sixth cusp, the 'cusp six' or tuberculum sextum. Two mesial roots are seen on occasion; this Sinodont feature is occasionally seen clinically, particularly in persons of North American Indian heritage. www.indiandentalacademy.com HOME
  116. 116. Facial: When compared to the first molar, the second molar crown is shorter both mesiodistally and from the cervix to the occlusal surface. The two welldeveloped buccal cusps form the occlusal outline. There is no distal cusp as on the first molar. A buccal developmental groove appears between the buccal cusps and passes midway down the buccal surface www.indiandentalacademy.com toward the HOME
  117. 117. Lingual: The crown is shorter than that of the first molar. The occlusal outline is formed by the mesiolingual and distolingal cusps. www.indiandentalacademy.com HOME
  118. 118. Proximal: The mesial profile resembles that of the first molar. The distal profile is formed by the distobuccal cusp, distal marginal ridge, and the distolingual cusp. Unlike the first molar, there is no distal fifth cusp. www.indiandentalacademy.com HOME
  119. 119. Occlusal: There are four well developed cusps with developmental grooves that meet at a right angle to form the distinctive "+4" pattern characteristic of this tooth. www.indiandentalacademy.com HOME
  120. 120. Contact Points; Height of Curvature: When moving distally from first to third molar, the proximal surfaces become progressively more rounded. The net effect is to displace the contact area cervically and away from the crest of the marginal ridges. Variation: Morphologically this is a stable tooth. Five-cusp versions are seen on occasion, however root variability is greater than in the first molar. www.indiandentalacademy.com HOME
  121. 121. Facial: The crown is often short and has a rounded outline. www.indiandentalacademy.com HOME
  122. 122. Lingual: Similarly, the crown is short and the crown is bulbous. www.indiandentalacademy.com HOME
  123. 123. Proximal: Mesially and distally, this tooth resembles the first and second molars. The crown of the third molar, however, is shorter than either of the other molars. Technically, only the mesial surface is a 'proximal' surface. www.indiandentalacademy.com HOME
  124. 124. Occlusal: Four or five cusps may be present. This surface can be a good copy of the first or second molar, or poorly developed with many accessory grooves. The occlusal outline is often ovoid and the occlusal surface is constricted. Occasionally, the surface has so many grooves that it is described as crenulated--a condition seen in the great apes. www.indiandentalacademy.com HOME
  125. 125. Contact Points; Height of Curvature: The rounded mesial surface has its contact area more cervical than any other lower molar. There is no tooth distal to the third molar. Variation: This is an extremely variable tooth and on occasion it is missing. While the most common anomaly of upper third molars is that they are undersized, lower third molars can be undersized or oversized. Lower third molars fail to erupt in many persons. www.indiandentalacademy.com HOME
  126. 126. DEVELOPMENT OF OCCLUSION www.indiandentalacademy.com
  127. 127. SEQUENCE OF ERUPTION TIME OF ERUPTION PATH OF ERUPTION STAGES OF DEVELOPMENT OF OCCLUSION www.indiandentalacademy.com HOME
  128. 128. SEQUENCE OF ERUPTION www.indiandentalacademy.com HOME
  129. 129. Primary dentition Central incisor Lateral incisor First molar Canine Second molar www.indiandentalacademy.com HOME
  130. 130. Permament dentition First molars Central incisor Lateral incisor Mandibular canines First premolars Second premolars Maxillary canines Second molars Third molars www.indiandentalacademy.com HOME
  131. 131. TIME OF ERUPTION www.indiandentalacademy.com HOME
  132. 132. Maxillary Mandibular Deciduous Tooth Eruption Root complete Eruption Root complete A 7½ 10 6 8 B 9 11 7 13 C 18 19 16 20 D 14 16 12 16 E 24 29 20 27 www.indiandentalacademy.com HOME
  133. 133. Maxillary Mandibular Permanent Tooth Eruption Root complete Eruption Root complete CI 7-8 10 6-7 9 LI 8-9 11 7-8 10 C 11-12 13-15 9-10 12-14 1ST PM 10-12 12-13 10-12 12-13 2ND PM 10-12 12-14 11-12 13-14 1ST M 6-7 9-10 6-7 9-10 2ND M 12-13 14-16 11-13 14-15 3RD M 17-21 18-25 17-21 18-25 www.indiandentalacademy.com
  134. 134. PATH OF ERUPTION (Permanent dentition) www.indiandentalacademy.com HOME
  135. 135. Mandibular Permanent Incisor  Permanent central incisors develop lingually and apically to the primary incisors  Permanent lateral incisors occupy a position lingual to the central incisors. The developing lateral incisor may be seen in close proximity to the lingual cortical plate of the mandibular symphysis  Crowns of both central and lateral are lingually inclined The incisal path of eruption of the teeth is oblique and usually directed labially relative to primary incisors  As the permanent incisors erupt they resorb the lingual aspect of the primary incisor roots  On completion of eruption they occupy a more labial inclination HOME www.indiandentalacademy.com
  136. 136. Maxillary Permanent Incisor  Eruption takes place after the mandibular lateral has erupted  Central incisor precedes lateral incisor The path of eruption is more labial and oblique than that of mandibular permanent incisors (resulting in a more labial positioning of maxillary incisors)  There is a distal tilting of the crowns of the central incisors on eruption causing a mild midline diastema. This gets closed with the eruption of the lateral incisors www.indiandentalacademy.com HOME
  137. 137. Mandibular Permanent Canines  During the eruption, the axis is directed mesially and lingually  The permanent cuspids erupt along the distal aspect of the roots of the permanent lateral incisors  Upon eruption, their final positioning, relative to their predecessors, is labial with a mesial inclination www.indiandentalacademy.com HOME
  138. 138. Maxillary Permanent Canines  This is the last tooth to erupt anterior to the molars in this arch As they erupt, they are directed towards the distal aspect of the maxillary permanent lateral incisor roots and erupt in the dental arch  Their final position in the arch is labial in their relation with the lateral incisors and 1st premolar www.indiandentalacademy.com HOME
  139. 139. Mandibular and Maxillary First Premolars  It develops beneath the first primary molar and is enclosed by its roots  The path of eruption is directly towards the occlusal plane  Resorbs the roots of the first primary molar to weaken its support and pushes it out to occupy its position in the arch www.indiandentalacademy.com HOME
  140. 140. Mandibular Second Premolars  Last tooth to erupt anterior to the first molar  There are three possible paths  Distal path of eruption – This is considered the best as there is no loss of space. As the 2 nd premolar erupts distally, it resorbs the distal root of the 2nd primary molar and glides along the mesial surface of the 1st permanent molar. This is considered the normal path of eruption.  Occlusal path of eruption – Here there is a loss of space owing to the mesial shifting of the 1 st permanent molar at the time of exfoliation of the 2nd primary molar. www.indiandentalacademy.com HOME
  141. 141.  Mesial path of eruption – Least desirable path of eruption. This occurs owing to the blocking out of space for the 2nd premolar due to an increased time lapse between the exfoliation of the 2nd primary molar and the eruption of the 2nd bicuspid. Mandibular Second Premolars Identical to the first premolar in its path of eruption. Mostly follows an occlusal path of eruption. www.indiandentalacademy.com HOME
  142. 142. Mandibular First Permanent Molar  The first permanent teeth to erupt  Prior to eruption, the crowns are canted mesially and lingually, with their bony crypts positioned at the angle formed by the junction of the body of the mandible and the anterior border of the ramus  Movement of the tooth occlusally, along with the resorption of the anterior border of the ascending ramus, facilitates the eruption of the tooth  During the course of eruption, the molar undergoes a rotation, re-orienting the crown with the occlusal plane  Ultimately they are positioned with a slight mesial tilt and a slight lingual inclination in the transverse axis  Flush terminal plane later changes to Class I relationship www.indiandentalacademy.com HOME
  143. 143. Maxillary First Permanent Molar  The Crowns are distally and buccally oriented in their crypts.  As the maxillary arch gets lengthened due to appositional growth at the tuberosities, the maxillary 1St permanent molar rotates mesially and the crowns are uprighted so that they move vertically towards the occlusal plane  On completion of eruption, they are inclined mesially on their long axis and buccally in their transverse axis www.indiandentalacademy.com HOME
  144. 144. Mandibular Second Permanent Molar  Crypts positioned at base of the ascending ramus  Space for eruption is gained by resorption of the anterior border of the ramus  In the crypts, the crowns are pointed mesially, almost at right angles to the occlusal plane  The crown rotates in a distal direction and erupts against the mandibular 1st permanent molar in and occlusal direction www.indiandentalacademy.com HOME
  145. 145. Maxillary Second Permanent Molar  Position in crypt and pathway of eruption is similar to the 1st permanent molar  Mesiobuccal inclination of the tooth in its final occlusal position www.indiandentalacademy.com HOME
  146. 146. STAGES OF DEVELOPMENT OF OCCLUSION www.indiandentalacademy.com HOME
  147. 147. Stage Age in years Characteristics First stage 3 Second stage 6 Eruption of 1st permanent molar Third stage 6–9 Exchange of incisors Fourth stage 9 – 12 Exchange of lateral teeth Fifth stage 12 Eruption of 2nd molar Primary dentition www.indiandentalacademy.com HOME
  148. 148. PRIMARY DENTITION www.indiandentalacademy.com HOME
  149. 149. Primary tooth buds form at 6 weeks IUL Commence erupting at 6 months post birth and goes upto 2 ½ years of age when the 2nd primary molar occludes At the age of 3 the primary dentition is established From 3 – 5 years no activity From 5 – 6 years, the size of the dental arch begins to change due to eruptive forces from the first permanent molar www.indiandentalacademy.com HOME
  150. 150. Spaces in primary dentition Primate space – mesial to maxillary canine, distal to mandibular canine Developmental space – between the incisors www.indiandentalacademy.com HOME
  151. 151. Occlusal relationship of 2nd primary molars  Eruption and root completion of the 2nd primary molar marks the completion of the primary dentition development  The relationship of the distal surfaces of the maxillary and mandibular primary molars is one of the most important factors to influence the future occlusion of the permanent dentition  Terminal plane – Mesiodistal relation of the max. and mand. 2nd primary molars when in centric occlusion Three types: a) Flush terminal plane b) Mesial step c) Distal step www.indiandentalacademy.com HOME
  152. 152. www.indiandentalacademy.com HOME
  153. 153. www.indiandentalacademy.com HOME
  154. 154. www.indiandentalacademy.com HOME
  155. 155. Size of the dental arch  Size can be measured by the dental arch width between the primary canines and between the 2 nd primary molars  Length can be measured from the most labial surface of the primary Central incisor to the canine and to the 2nd primary molars A.Inter canine width B.Inter molar width C.Anterior arch length D.Total arch length www.indiandentalacademy.com HOME
  156. 156. ERUPTION OF 1ST PERMANENT MOLAR www.indiandentalacademy.com HOME
  157. 157. 1st permanent molar is the key to the permanent occlusion The prediction of the occlusion of the 1st permanent molars is known at the primary dentition stage a) Flush terminal plane – If there are dental spaces existing in the primary dental arch, the 1st molar will erupt into CLASS I. If not, it becomes a cusp-tocusp occlusion b) Mesial step – Erupts directly into CLASS I occlusion c) Distal step – Directly and definitely into CLASS II occlusion The physiologic spaces get closed due to mesially www.indiandentalacademy.com directed eruptive forces of permanent molars HOME
  158. 158. Some cases of Flush terminal plane go in for CLASS III when physiologic spaces are absent in the mandible The active growth of the mandible also regulates the occlusion (forward and downward growth of mandible) www.indiandentalacademy.com HOME
  159. 159. www.indiandentalacademy.com HOME
  160. 160. EXCHANGE OF INCISORS www.indiandentalacademy.com HOME
  161. 161.  This commences after the eruption of the 1st molar begins  Total sum of the mesiodistal widths of permanent incisors is greater than that of primary incisors bye about 7mm in maxilla and 5mm in mandible  Moorress (1965) observed some degree of crowding of anteriors during their eruption, which is transient  Regulating factors for arrangement of permanent incisors are: a) Interdental spaces between primary incisors b) Increase of intercanine width c) Increase of anterior length in dental arch d) Change of tooth axis of incisors e) Ugly duckling stage www.indiandentalacademy.com HOME
  162. 162. EXCHANGE OF LATERAL TEETH (Canines and Premolars) www.indiandentalacademy.com HOME
  163. 163.  Limited by the mesial surface of the 1st molar distally and distal surface of the lateral incisor  Two factors permit smooth eruptive pathways a) Leeway space – The combined width of the permanent lateral teeth is less than that of the primary lateral teeth by about 1mm in the maxilla and 3mm in the mandible www.indiandentalacademy.com HOME
  164. 164. b)Order of exchange – Eruption pattern sequences usually seen are 3-4-5, 4-3-5, 4-5-3 In the mandible it is usually 3-4-5 and as the permanent canine is larger than the primary canine, crowding is very common immediately after the exchange of canines. If the pattern isn’t changed the crowding gets alleviated after the exfoliation of the 2nd primary molar. If the sequence changes to 4-3-5 or 4-5-3, there isn’t efficient utilization of the Leeway space and teeth get crowded www.indiandentalacademy.com HOME
  165. 165. ERUPTION OF 2ND PERMANENT MOLARS www.indiandentalacademy.com HOME
  166. 166.  Occurs after the eruption of all the permanent teeth in the dental arch upto the 1st permanent molar is complete  Its eruptive pathway is guided by the destal surface of the 1st permanent molar  The dental arch length may be less than in primary dentition owing to closure of Leeway space and this can cause crowding of the 2nd molar. However, this gets compensated by the growth of the mandible in a forward downward direction. www.indiandentalacademy.com HOME
  167. 167. DETERMINANTS OF OCCLUSAL MORPHOLOGY www.indiandentalacademy.com
  168. 168. Posterior controlling factor (Condylar guidance) Anterior controlling factor (Anterior guidance) Vertical determinants 1. Effect of condylar guidance on cusp height 2. Effect of anterior guidance on cusp height 3. Effect of plane of occlusion on cusp height 4. Effect of curve of spee on cusp height 5. Effect of mandibular lateral translation movement on cusp height Horizontal determinants 1. Effect of distance from the rotating condyle 2. Effect of distance from midsagittal plane 3. Effect of distance from rotating condyle and fossa from midsagittal plane 4. Effect of mandibular lateral translation movement 5. Effect of intercondylar distance www.indiandentalacademy.com HOME
  169. 169. Posterior controlling factor (Condylar guidance) www.indiandentalacademy.com HOME
  170. 170.  As the condyle moves out of centric relation it descends along the articular eminence  If the articular eminence is steep, the condyle describes a steep vertically inclined path and if flatter, the path is less vertically inclined  The angle at which the condyle moves away from a horizontal reference plane is referred to as the condylar guidance angle www.indiandentalacademy.com HOME
  171. 171.  The CGA is steeper for the orbiting condyle in a latero-trussive movement of the mandible as the medial wall of the mandibular fossa is steeper than the articular eminence in front  The two TMJ’s provide the guidance for the posterior portion of the mandible and are largely responsible for determining the character of mandibular movement posteriorly. Thus they become the posterior controlling factor  It is a fixed factor www.indiandentalacademy.com HOME
  172. 172. Anterior controlling factor (Anterior guidance) www.indiandentalacademy.com HOME
  173. 173.  The anterior teeth guide the movement of the anterior portion of the mandible  As the mandible protrudes, the incisal edge of the mandibular anterior teeth occlude with the lingual surfaces of the maxillary anterior teeth The steepness of the lingual surface determines the amount of vertical movement of the mandible  It is a variable factor www.indiandentalacademy.com HOME
  174. 174. Vertical determinants www.indiandentalacademy.com HOME
  175. 175. 1. Effect of condylar guidance on cusp height Steeper the articular eminence, more is the descent of the condyle, resulting in greater vertical movement. Thus allowing for steeper posterior cusps www.indiandentalacademy.com HOME
  176. 176. 2. Effect of anterior guidance on cusp height Increased horizontal overlap decreases the anterior guidance angle. There is less vertical movement of the mandible leading to flatter posterior cusps www.indiandentalacademy.com HOME
  177. 177. Increased vertical overlap increases the anterior guidance angle. There is more vertical movement of the mandible leading to steeper posterior cusps www.indiandentalacademy.com HOME
  178. 178. 3. Effect of plane of occlusion on cusp height  Plane of occlusion is an imaginary line touching the incisal edges of the maxillary anterior teeth and the cusps of the maxillary posterior teeth  Depending on the angulation of the plane of occlusion in relations to the horizontal plane, the degree of movement of the tooth varies. If less degree of movement is seen – flatter cusps; and if more degree of movement is seen – taller cusps. www.indiandentalacademy.com HOME
  179. 179. www.indiandentalacademy.com HOME
  180. 180. 4. Effect of curve of spee on cusp height  Curve of spee is an antero - posterior curve extending from the tip of the mandibular canine along the buccal cusp tips of the mandibular posterior teeth  Its degree of curvature influences the height of the posterior cusps. Flatter the curve of spee, greater is the angle away from the maxillary posteriors – taller cusp. More acute curve of spee, smaller the angle of mandibular posterior tooth movement – flatter cusps. www.indiandentalacademy.com HOME
  181. 181. www.indiandentalacademy.com HOME
  182. 182.  Orientation of the curve of spee also influences cusp height  Radius perpendicular to horizontal reference plane Posterior teeth located distal to the radius need shorter cusps and those mesial to the radius need taller teeth Rotated posteriorly : Shorter cusps Rotated anteriorly : Taller cusps www.indiandentalacademy.com HOME
  183. 183. www.indiandentalacademy.com HOME
  184. 184. 5. Effect of mandibular lateral translation movement on cusp height  This is a bodily sideshift of the mandible where the orbiting condyle moves downwards, forwards and inwards. The degree of inward movement of the orbiting condyle is determined by two factors (1) Morphology of medial wall of mandibular fossa (2) Inner horiz. Portion of TM ligament, which attaches to the lateral pole of the rotating condyle  The lateral translation has three attributes: amount, direction and timing www.indiandentalacademy.com HOME
  185. 185.  The amount of lateral translation depends on the tightness of the inner horizontal portion of the TM ligament attached to the lateral  pole of the rotating condyle. Looser the ligament, greater is the amount of lateral translation, posterior cusps should be shorter to permit lateral translation without contact  The direction of shift of the rotating condyle is determined by morphology and ligamentous attachment of the rotating TMJ. Movement occurs within a 60˚ cone permitting superior, inferior, anterior and posterior movements in addition to the lateral translation. The vertical movement of the rotating condyle during a lateral translation helps determine cusp height. Latero-superior movement – shorter posterior cusps www.indiandentalacademy.com Latero inferior movement – longer posterior cusps HOME
  186. 186.  The time of lateral translation is of great influence on occlusal morphology. If late, there is less influence as the maxillary and mandibular cusps are beyond functional range. If early, a shift is seen even before the condyle begins to translate (immediate side shift). If it occurs along with an eccentric movement, the movement is called progressive side shift. The more immediate the side shift, the shorter are the posterior teeth cusps to avoid interference. www.indiandentalacademy.com HOME
  187. 187. Horizontal determinants www.indiandentalacademy.com HOME
  188. 188. 1. Effect of distance from the rotating condyle Increased distance – wider angle between laterotrussive and mediotrussive pathways, flatter centric cusps www.indiandentalacademy.com HOME
  189. 189. 2. Effect of distance from midsagittal plane Increased distance – wider angle between laterotrussive and mediotrussive pathways, flatter centric cusps www.indiandentalacademy.com HOME
  190. 190. 3. Effect of distance from rotating condyle and fossa from midsagittal plane They generally counter act each other. The combination of the two positional relationships is what determines the exact pathways of the centric cusp tips. Curvature of dental arch causes the two components to counter act each other and negate their effect www.indiandentalacademy.com HOME
  191. 191. 4. Effect of mandibular lateral translation movement Increased lateral movement, increases the angle between laterotrussive and mediotrussive pathways The direction of rotation of the rotating condyle also plays a role Lateral and anterior direction – Increased angle (flatter cusp) Lateral and posterior direction – decreased angle (sharper cusp) www.indiandentalacademy.com HOME
  192. 192. 5. Effect of intercondylar distance Increase in distance, reduces the angle between laterotrussive and mediotrussive pathways www.indiandentalacademy.com HOME
  193. 193. www.indiandentalacademy.com Leader in continuing dental education www.indiandentalacademy.com

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