Development of tooth

Development of Tooth
Dr. Siji Elizabeth Saji
PG 1st Year

 Introduction
 Initiation – Dental lamina
– Vestibular Lamina
– Clinical Aspects
 Proliferation – Bud stage
– Cap stage
 Histodifferentiation – Early bell stage
 Morphodifferentiation – Advanced bell stage
 Apposition
 Root formation
 Eruption
– Phases and mechanisms
 Conclusion
 References

6th week of IU life: Primary
epithelial band formation
7th week of IU life: Primary
epithelial band divides into
buccal and lingual process
Dental Lamina
Vestibular
lamina
All deciduous teeth arises from
dental lamina, later the permanent successors arise
from its lingual extension & permanent molars from its
distal extension
Orban’s Oral Histology and Embryology ; GS Kumar; 12th edition

Initiation
Proliferation
Histodifferentiation
Morphodifferentiation
Apposition
MORPHOLOGICAL STAGES PHYSIOLOGICAL STAGES
Formation of Dental
Lamina
Bud stage
Cap Stage
Early Bell Stage
Advanced Bell
Stage
Formation of
Enamel and
Dentinal Matrix

 The primitive oral cavity, or stomodeum, is lined
by stratified squamous epithelium called the
oral ectoderm
 The oral ectoderm contacts the endoderm of
the foregut to form the buccopharyngeal
membrane
Developing
forebrain
Foregut
Mesenchyme
covering
forebrain
Developing
Stomodeum
Buccopharyngeal
membrane
Pericardium

Membrane ruptures at
about 27th day of
gestation and the
primitive oral cavity
establishes a
connection with the
foregut
Most of the
connective tissue
cells underlying the
oral ectoderm are of
neural crest or
ectomesenchyme in
origin
These cells instruct the overlying
ectoderm to start the tooth
development, which begins in the
anterior portion of the future maxilla &
mandible and proceeds posteriorly

2- 3 weeks after the rupture of buccopharyngeal membrane, certain
areas of basal cells of oral ectoderm proliferate rapidly, leading to
the formation of primary epithelial band
The band invades the underlying
ectomesenchyme along each of the
horseshoeshaped future dental arches
Orban’s Oral Histology and Embryology ; GS Kumar; 12th edition; Avery JK:
Development of the tooth; Third Edition.
Cheek
Lip
Vestibule
Vestibular
lamina
Degenerating
Dental lamina
Tooth Bud

The dental lamina -
primordium for the
ectodermal portion of the
deciduous teeth
The successors -from lingual
extension of of the dental
lamina opposite to the
enamel organ of each
deciduous teeth.
The lingual extension of the
dental lamina is named the
successional lamina &
develops from the 5th month
in utero ( permanent central
incisor) to the 10th month of
age (second premolar)
Total activity of the dental
lamina extends for atleast 5
years
Orban’s Oral Histology and Embryology ; GS Kumar; 12th edition; Avery JK:
Development of the tooth; Third Edition.
OE
DL
VL
SAL
Ectomesenchyme

dental lamina may still be active in the 3rd molar region after it has disappeared
elsewhere, except for occasional epithelial remnants
dental lamina functions for briefer period before it degenerates
Fragmentation of the dental lamina progresses toward the developing enamel organ
They later break up by mesenchymal invasion, which is at first incomplete and does not
perforate the total thickness of the lamina
As the teeth continue to develop, they loose their connection with the dental lamina

Vestibule
General lamina
Oral Ectoderm
Deciduous
Permanent
General
lamina
Vestibular
lamina
Successional lamina of permanent teeth primordia
Developing Teeth
Lateral
lamina

Subsequently hollows and forms the oral
vestibule between the alveolar portion of
the jaws and the lips and cheeks
It is Vestibular Lamina also termed as lip
furrow band
Labial and buccal to the dental lamina in
each dental arch, another epithelial
thickening develops independently

Also called anodontia vera, is
a rare genetic disorder characterized by
the congenital absence of
all primary or permanent teeth
FORMS
True False Pseudo
TYPES
Complete Partial
COMPLETE
PARTIAL
Shafer’s Textbook of oral pathology;R. Rajendran, R
Sivapathasundharam; 6th edition

Results from continued proliferation of primary dental lamina
to form 3rd tooth germ
POSITION
Upper
distomolars
Mesiodens
Premolars
Lower
distomolars
Canines
 Supplemental(where the tooth has a
normal shape for the teeth in that series);
 Tuberculate (also called "barrel shaped")
 Conical (also called "peg shaped");
 Compound odontome (multiple small
tooth-like forms);
 Complex odontome (a disorganized mass of dental tissue)
SHAPE
MESIODENS

BUD STAGE
This is the initial stage of tooth formation
where enamel organ resembles a small bud
The surrounding mesenchymal cells
proliferate, which results in their
condensation in two areas
The area of condensation immediately
below the enamel organ is the dental papilla
Dental sac :The ectomesenchymal condensation
that surrounds the tooth bud & the dental papilla
peripherally - low
columnar cells
centrally -
polygonal cells
Orban’s Oral Histology and Embryology ; GS Kumar; 12th edition; Avery
JK: Development of the tooth; Third Edition.
Oral Ectoderm
Tooth
Bud
Dental
Papilla

 Dental papilla & dental sac-
not well defined
more defined - in cap & bell
stages
BUD STAGE
Oral Ectoderm
Dental
Papilla
Tooth
Bud

Enamel Organ + Dental Papilla + Dental Sac
Enamel organ gives Enamel
Dental Papilla gives Dentin and Pulp
Dental Sac gives Periodontal ligament
(PDL)
Alveolar Bone
Cementum
Tooth Germ

 tooth bud –proliferates -unequal growth in different parts of the
tooth bud the cap stage which is characterized by a
shallow invagination on the deep surface of the bud
CAP STAGE
Outer enamel epithelium
Stellate
reticulum
Inner enamel
epithelium
Enamel
organ
Oral
mucosa
Dental
follicle
Dental
papilla
Dental
lamina

 Outer Enamel Epithelium
Peripheral cells/convexity of
cap
Cuboidal cells
 Inner Enamel Epithelium
concavity of cap
cuboidal cells
Basement membrane separates
O.E.E from Dental Sac
I.E.E from Dental papilla
CAP STAGE
Capillary
Inner
enamel
epithelium
Dental
Papilla
Stellate
reticulum

 Polygonal cells between the outer and the inner enamel epithelium,
begin to separate due to water being drawn into the enamel organ from
the surrounding dental papilla
 As a result the polygonal cells ---- star shaped but maintain contact with
each other by their cytoplasmic process
 As the star shaped cells form a cellular network, they are called the
stellate reticulum
CAP STAGE

 The cells in the center of the enamel organ are densely
packed and form the enamel knot
 This knot projects toward the underlying dental papilla
 At the same time a vertical extension of the enamel knot,
called the enamel cord occurs
CAP STAGE

 The function of enamel knot & cord -reservoir of the dividing cells
for the growing enamel organ
 The enamel knot act as a signaling centers as many important
growth factors are expressed by the cells of the enamel knot & thus
play an important role in determining the shape of the tooth
 The ectomesenchymal condensation i.e the dental papilla & the
dental sac are pronounced
CAP STAGE
Inner enamel
epithelium
Enamel organ
Enamel cord
Dental papilla
Enamel knot

 1. True generalized microdontia :
■ All teeth smaller than normal
 2. Relative generalized microdontia :
■ Normal or slightly smaller than normal teeth
■ Normal sized teeth may appear small when
present in
widely spaced jaw larger than normal
(macrognathia)
 3. Focal or localized microdontia :
■ Common condition
■ Most affected – maxillary lateral incisor & 3rd
molar
■ Most common form – Peg shaped lateral

 – Applied only when teeth are physically larger than usual and
should NOT include normal-sized teeth crowded within a small
jaw (relative macrodontia)
 – Additionally, this term should NOT be used to describe teeth
altered by fusion or gemination

 Continued uneven growth of the enamel organ - acquires a bell shape
 crown shape is determined
 due to pressure exerted by the growing dental papilla cells on the inner enamel
epithelium
 This pressure however was shown to be opposed equally by the pressure
exerted by fluid present in the stellate reticulum
 The folding of enamel organ to cause different crown shapes is shown to be due
to different rates of mitosis & difference in cell differentiation time
BELL STAGE
Stellate reticulum
Ameloblasts
Capillary
Inner enamel epithelium
Dental papilla
Stratum intermedium

BELL STAGE
Single layered cells 4-5 µm
Tall columnar cells (AMELOBLASTS)
Junctional complexes -Connect laterally
Desmosomes –connect St. intermedium
I.E.E cells exerts pressure on underlying
mesenchymal cells in dental papilla
which differentiate into odontoblasts.
differentiate
Orban’s Oral Histology and Embryology ; GS Kumar;
12th edition; Avery JK: Development of the tooth;
Third Edition.

 A few layers of squamous cells between
the inner enamel epithelium & the
stellate reticulum
 Cells attached by desmosomes & gap
junctions
 essential for enamel formation
BELL STAGE
Third Edition.

 expands further due to continued accumulation of intra-cellular
fluid
 star shaped cells -large processes anastomose- adjacent cells
 As the enamel formation starts, the Stellate reticulum collapses
to a narrow zone thereby reducing the distance between the
outer & inner enamel epithelium
BELL STAGE
Orban’s Oral Histology and Embryology ; GS Kumar; 12th
edition; Avery JK: Development of the tooth; Third Edition.

 cells -flatten to form low
cuboidal cells
 The outer enamel epithelium
is thrown into folds -rich in
capillary network- provides a
source of nutrition for the
enamel organ
 Before the inner enamel
epithelium begins to produce
enamel. Peripheral cells of the
dental papilla differentiate into odontoblasts
 These cuboidal cells later
assumes a columnar form &
produce dentin
BELL STAGE
Orban’s Oral Histology and Embryology ; GS Kumar; 12th
edition; Avery JK: Development of the tooth; Third Edition.
Stellate
reticulum
Stratum
intermedium
Ameloblasts
Inner
enamel
epithelium
Odontoblasts
Outer enamel
epithelium

 (Hereditary Opalescent Dentin) -- genetic disorder of tooth
development.
 Discolored teeth (most often a blue-gray or yellow-brown color)
and translucent. Teeth weaker than normal, prone to rapid
wear, breakage, and loss.
 These problems can affect both primary teeth and permanent
teeth.
 Inherited in an autosomal dominant pattern.

ADVANCED
BELL STAGE
 commencement of
mineralization & root
formation
 Boundary between the IEE &
odontoblasts DEJ
 Along the future
DEJ Formation of dentin
in the region of future cusps &
proceeds pulpally & apically
 After the first layer of dentin
is formed, the ameloblasts lay
down enamel over the dentin
in the future incisal & cuspal
areas
Third Edition.
Stellate reticulum
Enamel
Dentin
Ameloblasts
Odontoblasts
Pulp
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 The enamel formation
coronally & cervically
DEJ towards surface
 The cervical portion of
enamel organ gives
rise to Hertwig
Epithelial Root Sheath
(HERS)
 This HERS outlines the
future root & thus
responsible for the
size, shape,length &
number of roots
Third Edition.
Enamel
Dentin
Stratum
intermedium
Ameloblasts
Epithelial root
sheath
Preodontoblasts
Pulp
proliferation
zone
Epithelial
Diaphragm
Stellate reticulum
Odontoblasts

 Arises through union of two
normally separated tooth germs, and
depending upon the stage of
development of the teeth at the time of
union, it may be either complete or
incomplete.
 Can also be the union of a normal tooth
bud to supernumerary tooth germ.
In these cases, the
number of teeth is fewer
if the anomalous tooth is
counted as one tooth.

 Gemination arises when
two teeth develop from
one tooth bud and, as a
result, the patient has
an extra tooth

 Deposition of the matrix of the hard enamel structures
 Appositional growth of the enamel & dentin is a layer like
deposition of an extracellular matrix.
This type of growth additive
 Appositional growth is characterised by regular & rhythmic
deposition of the extracellular matrix, which is of itself
incapable of further growth

 Defect of the teeth in which
the tooth enamel is hard but
thin and deficient in amount

 abnormal formation of the enamel or
external layer of teeth.
 malfunction of the
proteins in the enamel:
 Appearance-
Teeth with abnormal color:
yellow, brown or grey. The teeth have a
higher risk for dental cavities and are
hypersensitive to temperature changes. This
disorder can afflict many number of teeth.
ameloblastin enamelin tuftelin
amelogenin

Localized to single tooth
Commonly affected tooth: Maxillary lateral
incisors
 Bilateral involvement is often seen &
sometimes defect can involve multiple teeth
involving the supernumeraries
Defect of tooth in which a
focal area on the tooth surface is folded or
invaginated pulpally to a variable extent
Clinical
•In case of pulp involvement with or without apical
pathology, endodontic treatment should be
attempted.
•more severe form extraction should be done

Most affected tooth: Premolars
 The pulp of the tooth may extend
into the dens evaginatus.
Teeth where the outer surface appears
to form an extra bump or cusp.
Clinical
• There is a risk of the dens evaginatus chipping off in
normal function Hence this condition requires monitoring
as the tooth can lose its blood and nerve supply as a result
and may need root canal treatment

 Most affected:
permanent maxillary lateral incisor(55%)
permanent maxillary central incisor(33%)
 Rarely: primary teeth
Clinical
• Whenever the lingual pits are present restorative
treatments should be done to prevent caries
• When talon cusp interferes with normal occlusion
preventive care should be taken by performing
endodontic treatment

Tencate’s Oral Histology; Antonio Nanci; SE Asia Edition

Avery JK: Development of the tooth; Third Edition

 The development of roots begin after enamel
& dentin formation has reached the future
CEJ
 The enamel forms HERS, which models the
shape of the root
 HERS consists of outer & inner enamel
epithelium only
 As the first layer of the dentin has been laid
down, the epithelial root sheath loses its
structural continuity and is close relation to
the surface of the root
Third Edition.

Its remnants persists as an epithelial
network of strands or clumps near the
external surface of the root
These epithelial remnants are found in
the periodontal ligament of erupted
teeth and are called as rests of
mallasez

 Prior to the beginning of root formation,
the root sheath forms the epithelial diaphragm
 The O.E.E & I.E.E bend at the future CEJ
into a horizontal plane, narrowing the wide cervical opening
 Proliferation : epithelial diaphragm cells + cells of connective
tissues of pulp adjacent to the diaphragm
 The free end of diaphragm does not grow
into the connective tissue but the epithelium proliferates
coronal to the epithelial diaphragm
Enamel organ
Enamel
Pulp
Proliferation
zone
Epithelial
diapragm
Dentin

 CT of the dental sac around the root sheath
Proliferates & invades the continuous double
epithelial layer dividing into network of epithelial strands
 The rapid sequence of proliferation &
destruction of HERS shows that it cannot be seen as
a continuous layer on the surface of developing root
 Last stages: the proliferation of the
epithelium in the diaphragm lags behind
that of the pulpal connective tissue
 Wide apical foramen is reduced first
to the width of the diaphragmatic opening
later :further narrowed
by opposition of dentin & cementum to the apex of the root
Root sheath
Epithelial rests
Epithelial
rests

 Differential growth of the epithelial diaphragm in the
multirooted teeth causes the division of root trunk into 2 or
3 roots
 During the general growth of enamel organ, expansion of its
cervical opening occurs in such a way that long tongue like
extensions of the horizontal diaphragm develop
 Before division of the root trunk occurs, free ends of the
horizontal epithelial flaps grow towards each other & fuse
 The single cervical opening is divided into 2 or 3 openings

 • On the pulpal surface of
the dividing epithelial
bridges, dentin formation
starts
• On the periphery of each
opening, root development
follows in the same way as
described for single rooted
teeth

 2nd molar is frequently involved.
 Clinically radiographic diagnosis is mandatory before attempting tooth
extraction.
 Deciduous dentition can result in crowding, abnormal spacing, and
delayed or ectopic eruption of the underlying permanent teeth
Two fully formed teeth, adhered along the
root surface by cementum.
The space restriction during
development, local trauma,
excessive occlusal force or local
infection after development may be
the suspected causative factors
Concrescence. Union by
cementum
of adjacent
Molars and it’s Radiograph
Shafer’s Textbook of oral pathology;R. Rajendran, R Sivapathasundharam; 6th edition
Jyoti S. Khedgikar, Shirish B. Khedgikar Concrescence of a Maxillary First and Second Molar: A Case
Report, Journal of Medical and Dental Science Research Volume 2 Issue 1 (2015)

an abnormal angulation or a sharp bend or curve
anywhere along the root portion of a tooth
Due to trauma
that displaces the
calcified portion
of the tooth germ
which alters the
angulation of the
tooth during root
formation

The development of an increased number
of roots on a tooth compared with that
classically described in dental anatomy

The axial or occlusal movement of the tooth
from its developmental position within the jaw
to its functional position in the occlusal plane
Types
Pre-
eruptive
Eruptive
Post-
eruptive

PRE-ERUPTIVE
• Made by deciduous
and permanent
tooth germs
intraosseously
before Eruption
• This phase occurs
in concordance
with jaw growth for
compensation
ERUPTIVE
• Tooth moves from
its position within
the bone to its
functional position
in occlusion
• However, since jaw
growth is still
occurring,
movement in planes
other than axial
movement
supersedes eruptive
phase
• As deciduos tooth
erupts, apically
situated permanent
tooth is enclosed by
bone except
gubernacular cord
& canal
POST-ERUPTIVE
• Maintains the
position of the
erupted tooth while
the jaw continues
to Grow
• Also compensates
for occlusal and
proximal wear
• Axial movement
• Ceases when jaw
growth is complete.
Gubernacular canal: small canal filled with connective tissue
and contains epithelial remnants of dental lamina.
Gubernacular cord: connective tissue mass inside canal

– Proliferating root impinges on a fixed base,
thus converting an apically directed force of
the tooth into occlusal movement
– Fallacies :
 Rootless teeth do erupt (most obvious in cases of dentin
dysplasia type I & following irradiation)
 Teeth do NOT erupt after completion of root formation
 Some teeth erupt a distance > total length of the root
Therefore, root formation is accommodated during tooth
eruption & is a consequence, NOT a cause of eruption process
Marks and Schroeder; Tooth eruption: theories and facts. Anat Rec 1996;
June; 245(2):374-93 79

 (Bosshardt et al., 1989) has shown that roots
grow faster in primary than in permanent teeth
 growth is greatest early in root formation
 dentin formation rate varies in different regions of a tooth
 the space for an erupting tooth by bone resorption
 Movement into that space 1. reciprocating collaboration of
root growth
2. adjacent bone formation
Root growth = rate of formation of = interradicular
the eruption pathway (EP) bone apposition
root growth > EP formation
root growth < EP formation
No Bone
Formation
Basal Bone
Resorption
Basal Bone
Formation
June; 245(2):374-93 79

 Formation of bone apical to developing teeth has long been
proposed as one mechanism for eruption
 The alveolar process forms during tooth development & is
deficient in sites where primary or permanent teeth fail to develop
 alveolar bone growth, tooth development, and eruption are
interdependent
 active eruption begins only after crown formation is complete
June; 245(2):374-93 79

 Present in pulpal tissues as well as PDL
 The pressure exerted by the blood vessels at the apex of the tooth help
in tooth eruption
 Local volume changes cause limited tooth movement.
 Fallacies :
Question marks remain if the pressure exerted is enough to help in
eruption
Teeth erupt even when vascular supply is cut
Orban’s Oral Histology and Embryology ; GS Kumar; 12th edition; Marks
and Schroeder; Tooth eruption: theories and facts. Anat Rec 1996; June;
245(2):374-93 79

Contractile
elements –
collagen in
fibroblasts
Constrictio
n
Force
initiation
by
Fibroblas
ts
Transmitted to
extracellular
compartments
by fibronexus
and collagen
bundles by root
formation
ERUPTION
Fallacies :
Examples of
PDL being
present but
tooth not
erupting and
vice versa
have been
reported
Orban’s Oral Histology and Embryology ; GS Kumar; 12th edition ; Marks
and Schroeder; Tooth eruption: theories and facts. Anat Rec 1996; June;
245(2):374-93 79

SUMMARY OF TOOTH DEVELOPMENT
Tencate’s Oral Histology; Antonio Nanci; SE Asia Edition

 As a dentist it is imperative we know about the normal
developmental stages and morphology so as to
differentiate it from abnormal
 Learning about the timeline of tooth development will
help us in avoiding unnecessary panic to the patient
guardian in cases where we suspect early exfoliation
and/or delayed eruption

 Orban’s Oral Histology and Embryology ; GS
Kumar; 12th edition
 Shafer’s Textbook of oral pathology;R.
Rajendran, R Sivapathasundharam; 6th edition
 Tencate’s Oral Histology; Antonio Nanci; SE Asia
Edition
 Marks and Schroeder; Tooth eruption: theories
and facts. Anat Rec 1996; June; 245(2):374-93 79
 Avery JK: Development of the tooth; Third
Edition

Development of tooth

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