1. The document describes the development of dentition and occlusion from the embryonic oral cavity to the permanent dentition in adults.
2. Key stages of tooth development include the dental lamina, enamel organ, bud stage, cap stage, and bell stage. The primary teeth erupt around 6-8 months and the permanent dentition begins emerging around age 6 with the first molars.
3. The mixed dentition period involves space management during the transition between primary and permanent teeth. The permanent dentition is usually complete by around 13 years of age.
3. DENTAL LAMINA...
The embryonic oral cavity is lined by stratified squamous
epithelium known as the oral ectoderm.
Around 6th
week the infero lateral border of the maxillary
arch and the supero lateral border of the mandibular arch
show localized proliferation of the oral ectoderm
resulting in the formation of the horse shoe shaped band
of tissue called the dental lamina.
The deciduous teeth are directly formed by the
proliferation of the lamina.
The permanent molars develop as a result of its distal
proliferation.
Succedanous teeth develop from a lingual extension of
the lamina.
4. ENAMEL ORGAN…
The ectoderm in certain areas of the dental lamina proliferates and
forms knob like structures that grow into the underlying mesenchyme.
Each of these knobs represent a deciduous tooth and is called the
enamel organ.
5. Based on the shape of the Enamel Organ the
development of teeth is divided into 3 stages:-
1. Bud stage.
2. Cap stage.
3. Bell stage.
6. BUD STAGE…
This is the initial stage of tooth development where the enamel organ
resembles a small bud.
The enamel organ consists of peripherally located low columnar cells
and centrally located polygonal cells.
7. CAP STAGE…
The tooth bud continues to proliferate resulting
in a cap shaped enamel organ.
The outer cells of the cap covering the
convexity are cuboidal – the outer enamel
epithelium.
The cells lining the concavity of the cap→ tall
columnar – the inner enamel epithelium.
The polygonal cells between the outer and the
inner epithelium forms a cellular network – the
stellate reticulum.
The ectomesenchymal condensation ie:-dental
papilla and dental sac are pronounced during
this stage.
8. BELL STAGE…
Due to the continued uneven growth of the
enamel organ it acquires a bell shape
A few layers of flat squamous cells between the
inner enamel epithelium and the stellate
reticulum – stratum intermedium.
As the enamel formation starts the stratum
intermedium collapses to a narrow zone
reducing the distance between the outer and the
inner epithelium.
9. LATE BELL STAGE…
Inner enamel epithelium →
ameloblasts ( tall columnar cells ) →
enamel.
Dental papilla → odontoblast
(cuboidal cells then later columnar)
→ dentin.
Outer enamel epithelium→ low
cuboidal cells → capillary network.
Dental sac → circular arrangement of
fibers → periodontal ligament.
The junction between inner enamel
epithelium and odontoblast →
dentinoenamel junction.
13. NATAL and NEONATAL TEETH...
Very rarely teeth are present at birth
called as natal teeth.
If they erupt during the 1st
30 days
then they are called as neo natal
teeth.
Mostly located in the mandibular
incisor region.
15. Chronology of Human Permanent DentitionChronology of Human Permanent Dentition
16. PRE EMERGENT ERUPTION...
Eruptive movements begin soon
after the root begins to form.
Two processes are necessary for pre
emergent eruption:-
1. There must be resorption of bone
and primary tooth roots overlying
the crown of the erupting tooth.
2. The eruptive mechanism itself then
must move the tooth in the direction
where the path has been cleared.
17. POST EMERGENT ERUPTION.
Once the tooth
erupts into the
mouth it
approaches the
occlusal level
and is subjected
to the forces of
mastication.
• The amount of tooth eruption after the teeth have come into occlusion
equals the vertical growth of ramus in a patient who is growing normally.
18. TERMS…
The stage of relatively rapid eruption from the
time a tooth first penetrates the gingiva to the
occlusal level is called the post emergent spurt.
This is followed by the phase of very slow
eruption termed the juvenile occlusal equilibrium.
When the pubertal growth ends a final phase in
tooth eruption called the adult occlusal
equilibrium is achieved.
19. If the antagonist is lost
at any age a tooth can
erupt more rapidly
demonstrating that the
eruption mechanism
remains active and
capable of producing
significant tooth
movement even late in
life.
21. In children with
cleidocranial dysplasia
not only the resorption of
primary teeth and bone
deficient but heavy
fibrous gingiva and
multiple supernumerary
teeth also impede normal
eruption.
Cleidocranial
dysplasia
25. DEVELOPMENT OF OCCLUSION
AND DENTAL ARCHES…
The human dentition is in a dynamic state
constantly changing throughout life.
A knowledge of these changes assists the
clinician in determining whether or not a
specific occlusion will be:
sustained , worsen ,or self correct over
time.
26. THE DEVELOPMENT OF OCCLUSION
OCCURS OVER 3 DISTINCT STAGES.
1. The deciduous dentition begins soon after birth
and is completed with the eruption of all
deciduous teeth.
2. The eruption of the first permanent molar ushers
in the mixed dentition .
3. Loss of the last deciduous tooth denotes the
transition to the permanent dentition.
29. GUM PADS…
The alveolar processes at the time of
birth.
Dental groove:-separates the
labiobuccal and the lingual portion.
Transverse groove:-divides the gum
pad into ten segments representing
each deciduous tooth.
Gingival groove:-separates the
gumpad from the palate and the
floor of the mouth.
Lateral sulci:-present between the
canine and the 1st
molar.
30. INFANTILE OPEN BITE…
When the upper and the
lower gum pad are
approximated there is a
complete overjet all around.
This infantile open bite is
considered to be normal .
It helps in sucking.
32. ERUPTION AGE and
SEQUENCE…
The mandibular central incisors are
the first to erupt around 6-8 months
of age.
A variation of 3 months from the
mean age is accepted to be normal.
The sequence of eruption is :-
A – B – D – C – E.
The primary dentition is usually
established y the age of 3 years.
34. SPACING…
Spacing usually exists between the
deciduous teeth for the normal
development of permanent teeth.
These spaces are called as
developmental or physiological
spaces.
Spacing invariably is seen mesial to
the maxillary canine and distal to
the mandibular canine.
These spaces are called as
primate, simian or anthropoid
spaces.
35. DEEP BITE.
The deep bite is accentuated by the fact that the deciduous incisors
are more upright then their permanent counterparts.
This is later reduced due to:-
1. Eruption of deciduous molars.
2. Attrition of incisors.
3. Forward movement of mandible due to growth.
.
40. ERUPTION AGE and SEQUENCE..
The mixed dentition period
begins at around 6 yrs of
age with the eruption of the
1st
permanent molar.
This period can be divided
into the following 3
phases:-
1. 1st
transitional period.
2. Inter transitional period.
3. 2nd
transitional period.
42. EMERGENCE of 1st
PERMANENT MOLAR
The mandibular 1st
molar is the first
permanent tooth to erupt at around 6yrs
of age.
The location and relation of the 1st
permanent molar depends on the distal
relationship between the upper and
lower 2nd
deciduous molars.
43. Flush terminal plane →
class Ι
(early and late mesial shift.)
Mesial step → class Ι.
Differential growth of
mandible in forward
direction persists →
class ΙΙΙ.
Distal step → class ΙΙ.
44. EARLY and LATE
MESIAL SHIFT…
Early shift occurs during the early
mixed dentition period .
The eruptive forces of the 1st
permanent
molar is sufficient to push the
deciduous 1st
and 2nd
molars forward to
close the primate spaces and establish
classΙ molar relationship.
In the cases when the primate spaces
are absent the permanent 1st
molar drift
mesially utilizing the leeway space.
This occurs in the late mixed dentition
period and is called the late shift.
→
→
45. INCISOR LIABILITY…
During the 1st
transitional period the deciduous incisors are replaced
by the permanent ones.
The permanent incisors are considerably larger then the deciduous
teeth they replace.
This difference between the amount of space needed and the
amount of space available is called as incisal liability.
The incisor liability is about 7mm in the maxillary arch and 5mm in
the mandibular arch.
This is overcome by 3 factors :-
1. Inter-dental spaces.
2. Inter-canine width.
3. Incisor inclination.
46. INTER-DENTAL SPACES…
The physiologic spaces seen in the primary dentition are utilized to
partly account for the incisal liability.
The permanent incisors are much more easily accommodated in
normal alignment in cases exhibiting adequate inter-dental spaces.
47. INTER–CANINE WIDTH…
During the transition from the primary incisors permanent
incisors an increase in inter-canine width of both maxillary
and mandibular arch is observed.
Child. Adult.
48. INCISOR INCLINATION…
The primary incisors are more upright
than their permanent counterparts.
Since the permanent incisors are more
labially inclined they tend to increase
the dental arch perimeter.
49. INTER TRANSITIONAL PERIOD..
In this period between the
permanent incisors and the
1st
permanent molars are the
deciduous molars and
canines.
This phase is relatively
stable and no change
occurs.
51. LEEWAY SPACE
of NANCE…
The second transitional period is
characterized by the replacement of
deciduous molars and canines by the
permanent premolars and cuspids
respectively.
The combined mesio distal width of the
permanent canines and premolars is less
than that of the deciduous canines and
molars.
This excess space is called leeway space
of Nance.
1.8mm – maxillary arch.
3.4mm – mandibular arch.
52. UGLY DUCKILNG STAGE…
A transient or self correcting
malocclusion is seen in the maxillary
incisor region between 8-10 yrs at the
time of eruption of the permanent
canines.
This situation is described by
Broadbent as ugly duckling stage as
children tend to look ugly during this
phase of development.
53. As the developing
permanent canines erupt
they displace the roots of
the lateral incisors
mesially.
This results in
transmitting the force on
roots of the centrals
which also get displaced
mesially.
Hence a distal divergence
of the two centrals causes
midline spacing.
54. After the eruption of canines the pressure is
transferred from the root to the coronal area of the
incisors and the malocclusion is corrected.
→
56. FEATURES…
The permanent dentition forms within
the jaws soon after birth except for the
formation of the cusps of the 1st
permanent molar which form before
birth.
The permanent incisors develop lingual
or palatal to the deciduous incisors and
move labially as they erupt.
The premolars develop below the
diverging roots of deciduous molars.
57. ERUPTION SEQUENCE…
In maxillary arch:-
6-1-2-4-3-5-7
or
6-1-2-3-4-5-7.
In mandibular arch:-
6-1-2-3-4-5-7
or
6-1-2-4-3-5-7.
59. DEFINITION…
ANGLE defined occlusion as the normal relation of the occlusal
inclined plane of the teeth when the jaws are closed.
The term occlusion has both static and dynamic aspects.
60. STATIC OCCLUSION…
Static refers to the
form , alignment of
teeth within and
between the arches
and the relationship of
teeth to their
supporting structures.
61. DYNAMIC OCCLUSION…
Dynamic refers to the function
of the stomatognathic system
as a whole comprising teeth
supporting structures,
temperomandibular joint ,
neuromuscular and nutritive
system.
62. IDEAL OCCLUSION…
It is a pre conceived
theoretical concept
of occlusal
structures and
relationships that
include idealized
principles and
characteristics that
an occlusion should
have.
63. BALANCED OCCLUSION…
An occlusion in which
balanced and equal contacts are
maintained throughout the
entire arch during all
excursions of the mandible.
64. TRAUMATIC OCCLUSION…
Traumatic occlusion is an
abnormal occlusal stress that is
capable of producing or has
produced injury to the
periodontium.
Anterior cross bite which produces
a traumatic bite resulting in
gingival recession of the involved
tooth. →
65. TYPES OF CUSP…
Centric holding cusps:- (stamp cusps)
The facial cusp of mandibular and
palatal cusps of maxillary posterior
teeth.
They occlude in the central fossae and
marginal ridges of opposing teeth.
Non supporting cusps:- (shearing or
guiding cusps.)
The maxillary buccal and the
mandibular lingual cusps .
They contact and guide the mandible
during excursions.
66. ARRANGEMENT OF
TEETH…
Human dentition exhibits 2 types of
teeth arrangement when the upper and
the lower teeth occlude:-
Cusp fossa occlusion:-
The stamp cusp of one tooth occludes
in a single fossa of a single opponent.
Tooth to tooth occlusion.
Cusp embrasure occlusion:-
Each tooth occludes with two
opposing teeth.
Tooth to two teeth occlusion.
68. CURVE OF SPEE..
CURVE OF WILSON..
Curve of Spee:-
It refers to the antero posterior curvature of
the occlusal surfaces beginning at the tip of
the lower cuspid and following the cusp tips
of the bicuspids and molars continuing as
an arc through the condyle.
Curve of Wilson:-
This is a curve that contacts the buccal and
lingual cusp tips of the mandibular teeth.
The curve of Wilson is medio lateral on
each side of the arch.
69. CURVE OF MONSON.
It is the curve of occlusion in which each cusp and incisal edges
touch or conform to a segment of a sphere in diameter with its centre
in the region of glabella.
70. CENTRIC RELATION and OCCLUSION
Centric relation is the relation of the
mandible to the maxilla when the
mandibular condyles are in the most
superior and retruded position in
their glenoid fossa with the articular
disk properly interposed.
Centric occlusion is that position of
the mandibular condyle when the
teeth are in maximum intercuspation.
71. CENTRIC CONTACTS.
They are areas of teeth that
contact the opposing teeth.
Posterior centric contacts
Anterior centric contacts.
72. ECCENTRIC OCCLUSION…
Eccentric occlusion refers to contact of teeth that occurs during
movement of mandible.
Eccentric occlusion can be of 2 types:-
1 - Functional occlusion.
Lateral function:- 1- Canine guided occlusion.
2- Grouped lateral occlusion.
Protrusive functional occlusion.
2 - Non functional occlusion.
73. FUNCTIONAL OCCLUSION.
Also called as the
Working side occlusion.
It refers to the tooth
contact that occur in the
segment of the arch
towards which the
mandible moves.
74. LATERAL FUNCTION OCCLUSION
It includes contacts that occur on canines and posterior teeth on
the side towards which the mandible moves.
It is divided into two parts:-
1. Canine guided occlusion.
2. Grouped lateral occlusion.
75. CANINE GUIDED and
GROUPED LATERAL OCCLUSION…
CANINE GUIDED OCCLUSION.
During lateral mandibular movements the opposing upper and lower
canines of the working side contact thereby causing disclusion of all
posterior teeth on the working and balancing side.
GROUPED LATERAL OCCLUSION.
In addition to canine guidance when certain other posterior teeth on
the working side also contact during lateral movement it is called as
Grouped lateral occlusion.
76. PROTUSIVE FUNCTIONALOCCLUSION..
It includes eccentric contacts that occur when the mandible moves
forward.
The mandibular anterior teeth contact along the lingual inclines of
the maxillary anterior teeth.
77. NON FUNCTIONAL OCCLUSION..
The tooth contacts that occur in the segment
away from which the mandible moves.
For eg:-if the mandible is moved to the left
side contacts occur on the right side.
79. KEY 1
MOLAR INTERARCH RELATIONSHIP…
The mesiobuccal cusp of the upper 1st
molar should occlude
in the groove between the mesial and medial buccal cusp of
the lower 1st
molar.
80. KEY 2
MESIO DISTAL CROWN ANGULATION...
A line that passes along the long axis of the crown through the
most prominent part of the center of the labial or the buccal surface
is called the long axis of the clinical crown.
The gingival part of the long axis must be distal to the occlusal part
of the axis.
81. KEY 3
LABIO LINGUAL CROWN
INCLINATION.
If the gingival area of the crown
is more lingually placed than the
occlusal area:-positive crown
inclination.
If the gingival area is more
labially or buccally placed:-
negative crown inclination.
Maxillary incisors:- +ve
inclination.
Mandibular incisors:- -ve
inclination.
Posteriors:- -ve inclination.
82. KEY 4
ABSENCE OF ANY ROTATION…
Normal occlusion is characterized
by absence of any rotation. →
Rotated posterior teeth occupy
more space while rotated incisors
occupy less space.
Incisor rotation
83. KEY 5
TIGHT CONTACTS…
To consider an occlusion normal there should be tight contacts
between adjacent teeth.
Spaced dentition. Tight contacts
84. KEY 6
CURVE OF SPEE…
A normal occlusion plane according to Andrews
should be flat wit the curve of Spee not exceeding
1.5mm
86. CROWDING..
In modern population there is a
strong tendency for crowding
of the mandibular incisors to
develop in the late teens or
early twenties.
3 major theories to explain this
are:-
1. Lack of normal attrition in
modern diet.
2. Pressure from the 3rd
molars.
3. Late mandibular growth.
Mandibular crowding.
87. LACK of NORMAL ATTRITION in the DIET.
Shortening of arc length and mesial
migration are a natural phenomenon.
Hence crowding will not develop if the
amount of tooth structure is lost during the
final stages of growth.
Therefore as compared to the primitive
population who had a coarse diet the
modern diet is soft.
Hence less attrition and more chances of
crowding.
88. PRESSURE FROM THE 3rd
MOLARS.
In most of the cases 3rd
molars are
impacted because the jaw length does
not increase enough to accommodate
them via backward remodeling of the
ramus.
89. LATE MANDIBULAR GROWTH…
Late incisor crowding
develops as the entire
mandibular dentition moves
distally relative to the
mandible in late mandibular
growth.
The mandibular incisors tend
to be displaced lingually.
