Development of tooth Part 2

1. Dr. Arun Panwar
25/02/2020

2. • Introduction
• Dental lamina
• Vestibular lamina
• Development of tooth
• Developmental stages
• Clinical considerations
• Conclusion
• References
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3. • Development of tooth is a complex process, in which reciprocal and
sequential interaction between the oral epithelium and mesenchymal
cells, regulate cell activities like proliferation, condensation, adhesion,
migration, differentiation and secretion, which leads to the formation
of a functional tooth organ.
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4. • Teeth are derived from oral ectoderm and neural crest
ectomesenchyme.
• Each developing tooth grows as an anatomically distinct
unit.
• The fundamental developmental process remains the
same for all teeth.
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5. • After the formation of the neural tube a group of cells
separates from the neural ectoderm called as neural
crest cells.
• These cells have the capacity to migrate and differentiate
extensively with in the developing embryo.
• Failure of neural crest cells to migrate normally to
appropriate places during the craniofacial development
leads to defects like, absence of teeth and under
developed jaw bones.
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6. • The primitive oral cavity or
stomodeum- lined by –
stratified squamous epithelium
called the oral ectoderm
(primitive oral epithelium)
• Most of the connective tissue
cells – neural crest cells.
• They induce the overlying
ectoderm to start tooth
development.
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7. • When the embryo is 6 weeks old- certain
areas of basal cells proliferate more rapidly
than adjacent areas
primary epithelial band.
• At 7th week-divides into:
• Inner (lingual) process- dental lamina
• Outer (buccal process)- vestibular lamina
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8. • It serves as a primordium for the ectodermal portion of the deciduous
teeth.
• During the development of jaws the permanent molars arise directly from
the distal extension of the dental lamina.
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9. • Labial and buccal to the dental lamina in each
dental arch, another epithelial thickening develops
independently
• It is Vestibular Lamina also termed as lip furrow
band
• Subsequently hollows and form the oral vestibule
between the alveolar portion of the jaws and the
lips and cheeks.
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11. • Anodontia
• Rare genetic disorder
characterized by the congenital
absence of primary or permanent
teeth
• Types:
• True anodontia
• False/ induced anodontia
- Occurs as result of extraction
of all teeth
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Morphologic stages Physiologic stages
Dental lamina
Bud stage
Cap stage
Early Bell stage
Advanced Bell stage
Formation of enamel and dentin
matrix
Initiation
Proliferation
Histodifferentiation
Morphodifferentiation
Apposition

13. • At certain points along the dental
lamina each representing the location
of one of the 10 mandibular & 10
maxillary teeth, ectodermal cells
multiply rapidly & little knobs that
grow into the underlying
mesenchyme
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14. • Each of these little down
growths from the dental lamina
represents the beginning of the
enamel organ of the tooth bud of
a deciduous tooth
• First to appear are those of
anterior mandibular region
• As the cell proliferation occurs
each enamel organ takes a shape
of- bud – cap – bell .
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15. • The tooth germ consists of :
• The ectodermal component- the enamel organ
• The ectomesenchymal components- the dental papilla & the
dental follicle
• The enamel organ- enamel
• The dental papilla- the dentin and the pulp
• The dental follicle - the cementum, periodontal ligament & the
alveolar bone
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16. • This is the initial stage of tooth
formation where enamel organ
resembles a small bud.
• the enamel organ -consists of
peripherally located low
columnar cells & centrally
located polygonal cells
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17. • 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
 The ectomesenchymal condensation
that surrounds the tooth bud & the
dental papilla is the dental sac
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18. • As the tooth bud continues to
proliferate, it does not expand
uniformly into a large sphere.
• Instead unequal growth in different
parts of the tooth bud leads to the cap
stage.
• It is characterized by a shallow
invagination on the deep surface of the
bud.
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19. Outer & inner enamel epithelium
• The peripheral cells of the cap stage are
cuboidal , cover the convexity of the cap & are
called the outer enamel epithelium.
• The cells in the concavity of the cap become
tall columnar cells & represent the inner
enamel epithelium.
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20. Stellate reticulum
• Polygonal cells located 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 become 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.
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22. Gemination
• Anomaly arising from an attempt
at division of a single tooth germ
by an invagination .
• Resulting into two incomplete
teeth
• Usually one with 2 completely or
incompletely separated crown
with single root & root canal
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23. Fusion
• Arise through union of 2 normally separated
tooth germs
• If contact early- 2 teeth completed united to
form single large tooth
• Contact after calcification- crown formation
complete & union by rots only
• Ex- any normal teeth
- 1 normal+ supernumerary ( mesiodens,
distomolar)
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24. Supernumerary teeth
• Duplication of teeth in normal series and
occurs at the end of the tooth series
• Most common –
permanent maxillary lateral incisors,
Premolars & molars
Odontome
Types –
Complex composite: disorganised mass of
dental tissue
Compound composite: malformation bearing
superficial anatomical similarity to normal tooth
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25. • 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
• The folding of enamel organ to cause different crown shapes is shown to
be due to different rates of mitosis & differentiation..
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26. Inner enamel epithelium
• A single layer of cells that differentiate prior to
amelogenesis into tall columnar cells called
ameloblasts
• These elongated cells are attached to one another
by junctional complexes laterally & to cells in
the stratum intermedium by desmosomes.
• These cells exert a strong influence on the
underlying mesenchymal cells of the dental
papilla, which later differentiate into
odontoblasts.
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27. Stratum intermedium
• A few layers of squamous cells form
the stratum intermedium , between the
inner enamel epithelium & the stellate
reticulum
• These cells are closely attached by
desmosomes & gap junctions.
• This layer seems to be essential to
enamel formation
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28. Stellate reticulum
• These cells expands further due to
continued accumulation of intra-cellular
fluid.
• These star shaped cells, have large
processes which anastomose with those
of 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
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29. Outer enamel epithelium
• The cells - flatten to form low
cuboidal cells
• The outer enamel epithelium is
thrown into folds which are rich in
capillary network- this provides a
source of nutrition for the enamel
organ
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Dental papilla:
• 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

30. • The commencement of
mineralization & root
formation
• The boundary between the
inner enamel epithelium &
odontoblasts outline the future
dentino enamel junction(DEJ)
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31. • Formation of dentin occurs first
as a layer along the future
dentino-enamel junction 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.
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32. • Begins after enamel & dentin formation
has reached the future CEJ
• The enamel organ plays an important
role - by forming HERS, which models
the shape, size, length & number of the
roots
• HERS consists of outer & inner enamel
epithelium only
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33. • 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
• Its remnants persists as - an epithelial
network of strands or clumps near the
external surface of the root.
• These are found in the periodontal
ligament of erupted teeth and are
called as rests of Malassez
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34. • Prior to the beginning of root formation, the root sheath forms the
epithelial diaphragm
• The outer & the inner enamel epithelium bend at the future CEJ into a
horizontal plane, narrowing the wide cervical opening
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35. Epithelial diaphragm
• The proliferation of the cells of the
epithelial diaphragm is accompanied by
the proliferation of the cells of the
connective tissues of the 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
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37. • Since development of tooth forms the base of dentistry, a
thorough understanding is required by the dentist
regarding the stages of tooth development and the
anomalies related to it.
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39. • Orban’s oral histology & embryology . GS kumar 12
edition.
• Shafer’s Textbook of Oral Pathology – R.Rajendran,
B.Sivapathasundharam, 5th edition.
• Tencate’s oral histology –development, structure &
function.
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