Anatomy and dev of occlusion / dental implant courses

ANATOMY
AND
DEVELOPMENT OF
OCCLUSION
INDIAN DENTAL ACADEMY
Leader in continuing Dental Education
www.indiandentalacademy.com

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

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.
HOME

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.
HOME

SKELETAL
COMPONENT

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

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.
HOME

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
HOME

 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.
HOME

HOME

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

 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}
HOME

 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.
HOME

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.
HOME

JOINTS, LIGAMENTS
AND MUSCLES
HOME

The joint which plays an important role
in the masticatory system is the Temporo-
mandibular joint.
Formed by the articulating surface of
the condyles of the mandible and the articular
fossa (bilaterally) of the temporal bone.
HOME

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
HOME

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.
HOME

Masseter
HOME

Temporalis
HOME

Lateral and medial
pterygoids
HOME

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.
HOME

DENTAL
COMPONENT

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.
HOME

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.
HOME

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.
HOME

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.
HOME

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
enamel organ is the dental papilla HOME

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.
HOME

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.
HOME

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

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.
HOME

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.
HOME

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. HOME

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.
HOME

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.
HOME

Anatomical
features in brief of
individual groups
of teeth

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.
HOME

Maxillary Central Incisor
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.
HOME

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.
HOME

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.
HOME

Incisal: The crown is
roughly triangular in
outline; the incisal edge
is nearly a straight line,
though slightly crescent
shaped.
HOME

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.
HOME

Maxillary Lateral Incisor
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.
HOME

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.
HOME

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.
HOME

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.
HOME

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.
HOME

Mandibular Central Incisor
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.
HOME

Lingual: The lingual
surface has no definate
marginal ridges. The
surface is concave and
the cingulum is minimal
in size.
HOME

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.
HOME

Incisal: The incisal edge is
at right angles to a line
passing labiolingually
through the tooth
reflecting its bilateral
symmetry.
HOME

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.
HOME

Mandibular Lateral Incisor
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.
HOME

Lingual: Except for the
lack of symmetry, this
tooth resemble the
central.
HOME

Proximal: Like the central,
the crown presents a
triangular outline. When
viewed critically, the
rotation of the incisal
edge can be seen.
HOME

Incisal: The incisal edge
'twisted' from the 90
degree angle with a line
passing labiolingually
through the tooth.
HOME

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.
HOME

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

Maxillary Canine
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.
HOME

Lingual: Distinct mesial
and distal marginal
ridges, a well-developed
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.
HOME

Proximal: The mesial and
distal aspects present a
triangular outline. They
resemble the incisors,
but are more robust--
especially in the
cingulum region.
HOME

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.
HOME

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.
HOME

Mandibular Canine
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
HOME

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.
HOME

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.
HOME

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 tooth.
HOME

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.
HOME

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
HOME

Maxillary First Premolar
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.
HOME

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.
HOME

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 groove is a
distinctive feature of this
tooth.
HOME

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.
HOME

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.
HOME

Maxillary Second Premolar
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.
HOME

Lingual: Again, this tooth
resembles the first. The
lingual cusp, however, is
more nearly as large as
the buccal cusp.
HOME

Proximal: Mesial and distal
surfaces are rounded.
The mesial
developmental
depression and mesial
marginal ridge are not
present on the second
premolar.
HOME

Occlusal: The crown
outline is rounded,
ovoid, and is less clearly
defined than is the first.
HOME

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.
HOME

Mandibular First Premolar
Facial: The outline is very
nearly symmetrical
bilaterally, displaying a
large, pointed buccal
cusp. From it descends a
large, well developed
buccal ridge.
HOME

Lingual: This tooth has the
smallest and most ill-
defined lingual cusp of
any of the premolars. A
distinctive feature is the
mesiolingual
(Remember the mesial
marginal developmental
groove in the upper first
premolar? That one is
mesial. The one on the
lower is toward the
lingual.)
HOME

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
teeth.
HOME

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
known as 'snake eyes' when
they are restored.
HOME

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.
HOME

Mandibular Second Premolar
Facial: From this aspect,
the tooth somewhat
resembles the first, but
the buccal cusp is less
pronounced. The tooth is
larger than the first.
HOME

Lingual: Two significant
variations are seen in
this view. The most
common is the three-
cusp 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.
HOME

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, well-developed
profile.
HOME

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 larger
than the upper second.)
HOME

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.
HOME

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.
HOME

Maxillary First Permanent
Molar
Facial: The mesiobuccal
and distobuccal cusps
dominate the facial
outline. They are
separated by the buccal
All three roots are
visible. The buccal roots
present a 'plier handle'
appearance with the
large lingual root
centered between them.
HOME

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.
HOME

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 onto
the distobuccal root is
occasionally described.
HOME

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 located on the mesiolingual
cusp.
HOME

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.
HOME

Maxillary Second Permanent
Molar
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.
HOME

Lingual: The distolingual
cusp is smaller than the
mesiolingual cusp. The
Carabelli trait is absent.
HOME

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.
HOME

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.
HOME

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.
HOME

Maxillary Third Permanent
Molar
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.
HOME

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.
HOME

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.
HOME

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 heart-shaped. The
mesial lingual cusp is the
largest, the mesial buccal
is second in size, and the
distal buccal cusp is the
smallest.
HOME

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.
HOME

Mandibular First Permanent
Molar
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 curved
than the mesial root.
HOME

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
cusps
HOME

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 aspect: the
distobuccal cusp, the distal cusp,
and the distolingual cusp. HOME

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 dental
anthropology.
HOME

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.
HOME

Mandibular Second Molar
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 well-
developed 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
toward the cervix.
HOME

Lingual: The crown is
shorter than that of the
first molar. The occlusal
outline is formed by the
mesiolingual and
distolingal cusps.
HOME

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.
HOME

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.
HOME

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.
HOME

Mandibular Third Molar
Facial: The crown is often
short and has a rounded
outline.
HOME

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

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.
HOME

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.
HOME

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.
HOME

DEVELOPMENT
OF
OCCLUSION

SEQUENCE OF ERUPTION
TIME OF ERUPTION
PATH OF ERUPTION
STAGES OF DEVELOPMENT OF OCCLUSION
HOME

SEQUENCE OF ERUPTION
HOME

Primary dentition
Central incisor
Lateral incisor
First molar
Canine
Second molar
HOME

Permament dentition
First molars
Central incisor
Lateral incisor
Mandibular canines
First premolars
Second premolars
Maxillary canines
Second molars
Third molars
HOME

TIME OF ERUPTION
HOME

Deciduous
Tooth
Maxillary Mandibular
Eruption Root
complete
Eruption Root
complete
A 7 ½ 10 6 8
B 9 11 7 13
C 18 19 16 20
D 14 16 12 16
E 24 29 20 27
HOME

Permanent
Tooth
Maxillary Mandibular
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 18-25www.indiandentalacademy.com

PATH OF ERUPTION
(Permanent dentition)
HOME

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

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
HOME

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
HOME

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
HOME

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
HOME

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 2nd
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 1st
permanent molar at the time of exfoliation of the
2nd
primary molar. HOME

 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.
HOME

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
HOME

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
HOME

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
HOME

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
HOME

STAGES OF
DEVELOPMENT OF
OCCLUSION
HOME

Stage Age in years Characteristics
First stage 3
Second stage 6
Third stage 6 – 9
Fourth stage 9 – 12
Fifth stage 12
Primary dentition
Eruption of 1st
permanent molar
Exchange of incisors
Exchange of lateral
teeth
Eruption of 2nd
molar
HOME

PRIMARY DENTITION
HOME

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
HOME

Spaces in primary dentition
Primate space – mesial to maxillary canine,
distal to mandibular canine
Developmental space – between the incisors
HOME

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
HOME

Size of the dental arch
 Size can be measured by the dental arch width
between the primary canines and between the 2nd
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
HOME

ERUPTION OF 1ST
PERMANENT MOLAR
HOME

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-to-
cusp 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
directed eruptive forces of permanent molars HOME

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)
HOME

EXCHANGE OF INCISORS
HOME

 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
HOME

EXCHANGE OF
LATERAL TEETH
(Canines and Premolars)
HOME

 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
HOME

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
HOME

ERUPTION OF 2ND
PERMANENT MOLARS
HOME

 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.
HOME

DETERMINANTS
OF OCCLUSAL
MORPHOLOGY

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
HOME

Posterior controlling factor
(Condylar guidance)
HOME

 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
HOME

 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
HOME

Anterior controlling factor
(Anterior guidance)
HOME

 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
HOME

Vertical determinants
HOME

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
HOME

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
HOME

Increased vertical overlap increases the
anterior guidance angle. There is more vertical
movement of the mandible leading to steeper
posterior cusps
HOME

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.
HOME

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.
HOME

 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
HOME

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
HOME

 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
Latero inferior movement – longer posterior cusps HOME

 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.
HOME

Horizontal determinants
HOME

1.Effect of distance from the rotating condyle
Increased distance – wider angle between
laterotrussive and mediotrussive pathways, flatter
centric cusps
HOME

2. Effect of distance from midsagittal plane
Increased distance – wider angle between
laterotrussive and mediotrussive pathways, flatter
centric cusps
HOME

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
HOME

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)
HOME

5. Effect of intercondylar distance
Increase in distance, reduces the angle
between laterotrussive and mediotrussive
pathways
HOME

Anatomy and dev of occlusion / dental implant courses

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Viewers also liked

Viewers also liked (9)

Similar to Anatomy and dev of occlusion / dental implant courses

Similar to Anatomy and dev of occlusion / dental implant courses (20)

More from Indian dental academy

More from Indian dental academy (20)

Recently uploaded

Recently uploaded (20)

Anatomy and dev of occlusion / dental implant courses