1. UNIVERSITATEA DE STAT DE MEDICINĂ ŞI FARMACIE “NICOLAE TESTEMIŢANU”
DEVELOPMENT OF THE
DECIDIUOUS &
PERMANENT TEETH
CATEDRA HISTOLOGIE, CITOLOGIE ŞI EMBRIOLOGIE
3. Hard tissues of the tooth:
• ENAMEL
• DENTIN
• CEMENTUM
Soft tissue of the tooth:
•DENTAL PULP
(crown pulp & root
canal)
4. Tooth development begins from the 6th week of the
intrauterine development
2 embryonic origins:
I. Ectoderm - oral epithelium - enamel
II. Ectomesenchyme (neural crests)– dentin, cement, dental pulp,
periodontal ligament
5. 2 main processes in the tooth
development
• Crown formation
• Root formation (is usually completed
approximately 2 -3 years after the tooth
erupts)
6. FUNCTIONAL STAGES OF
TOOTH DEVELOPMENT
• Initiation
• Proliferation
• Morpho-differentiation and
Histo-differentiation
• Apposition
• Root development
7. MORPHOLOGICAL STAGES
OF TOOTH DEVELOPMENT
• Bud stage
• Cap stage
• Bell stage (early & late)
• Early & late crown
• Early root formation
8. Correlation of morphological stages of
tooth development and functional features
Morphological stage Main functional activity
Dental lamina Initiation of tooth germ
Bud stage Proliferation (cell division)
Cap stage Proliferation
Beginning of histo-differentiation
Bell stage Prominent histo-differentiation
Morpho-differentiation
Early crown stage Apposition (formation of dentin &
enamel)
Late crown stage Continued apposition of dentin &
enamel including enamel
maturation
Early root stage Formation of radicular dentin &
cementum
9. BUD stage CAP stage
LATE CROWN stage
BELL stage
10. Tooth development
• The first recognizable sign of tooth
development in humans occurs during the
5-6th week of intrauterine life.
• At this time is characteristic the appearance
of vestibular & dental laminae as a result of
proliferation of oral epithelium.
12. VESTIBULAR LAMINA
• It is an ectodermal epithelial extension from the
lining of the oral cavity that proliferates into the
underlying ectomesenchyme of the maxilla and
the mandible lateral to the dental lamina. The
central cells of this lamina disintegrate to form
the sulcus which is the space between the
maxilla and the mandible on one side and the
lips and the cheeks on the other side.
13. DENTAL LAMINA
• it is derived from the ectodermal epithelial
lining of the oral cavity. These epithelial
cells form a sheet-like structure that extends
into specific areas of the ectomesenchymal
tissues within the alveolar processes of the
maxilla and mandible. These areas are parts
of the developing dental arch regions where
teeth form and eventually erupt.
17. THE INITIATION. BUD STAGE
•Epithelial cells are inductors in the tooth development
•Epithelial cells produce growth factors (TGFß1, BMP2, IGF),
that transmit the role of inductor through the basement
membrane to ectomesenchyme
18. •The progressive proliferation of the dental lamina into the
ectomesenchyme results in the formation of a DENTAL BUD
at the distal end of the dental lamina.
20. DENTAL BUD
• The dental bud looks like a round mass of
proliferating epithelial cells and it is
surrounded by condensation of
ectomesenchymal tissues which form the
dental papilla and dental sac.
23. DENTAL BUD
Dental bud - is
the future enamel
organ
Ectomesenchyme of this
region – is the future
dental papilla
Ectomesenchyme of this region
– is the future dental sac
24. Cap stage
• The dental bud differentiates into a cap-shaped
enamel organ.
• The epithelial dental organ looks like a head cap
with a round convex side and a straight or
slightly concave one.
• During the cap stage are formed the dental
papilla & dental sac.
25. PROLIFERATION. CAP stage
- enamel organ
- dental papilla
- dental sac
are differentiated at this stage
30. ENAMEL CORD
• A linear group of cells collectively termed
the enamel cord traverses the stellate
reticulum. It is a temporary structure with
no known function.
33. Dental papilla & dental sac
• The concentration of ectomesenchyme,
which is in part enveloped by the
invaginated inner enamel epithelium, is
named the dental papilla.
• The dental sac is a concentration of
ectomesenchyme that encircles the enamel
organ and the dental papilla.
37. Stratum intermedium
• The layer adjacent to the inner enamel
epithelium is the stratum intermedium,
and will become important in transporting
nutrients to the future ameloblasts.
39. • Preameloblasts initiate the differentiation
of odontoblasts which arise from cells in
the dental papilla. The odontoblasts are
called preodontoblasts before they begin
the production of dentin.
46. LATE BELL stage
Is characterized of:
-Appearance of
dentin
-Appearance of
enamel
-Transformation of
the dental papilla
into DENTAL
PULP
-Morphological
changes appear in
the dental sac
47. APPOSITION. LATE CROWN stage
• Deposition of the dentin & enamel occurs by apposition
with alternation of active & resting states
51. Outer enamel epithelium, intermedium epithelium & stellate
epithelium become thinner and together form STRATIFIED
EPITHELIUM
52. REDUCED ENAMEL EPITHELIUM
• Takes part in the crown modeling
• Induces the dentinogenesis of the crown &
root
• Assists in enamel formation & in the
formation of dentin-gum connection
• Isolates the enamel from the connective
tissue of the dental sac
• Takes part in the tooth eruption
53. REDUCED ENAMEL EPITHELIUM (A)
Consists of: stratified epithelium & resting ameloblasts
B – ameloblasts, C - capillary
54. ROOT FORMATION
• Begins after complete formation of the
tooth crown & continues after the eruption.
• Key elements, that take part in the root
formation, are:
1. Cervical loop – that is transformed into
EPITHELIAL ROOT SHEATH OF
HERTWIG , that differentiates into
EPITHELIAL DIAPHRAGM
2. Dental sac
55. CERVICAL LOOP
The layer of low columnar
cells of the inner enamel
epithelium is continuous with
the layer of cuboidal cells that
form the outer enamel
epithelium at the structure
termed the cervical loop.
58. ROOT FORMATION
• After complete formation of the crown of the
tooth, the root begins to form. An extension of
the enamel organ, called the epithelial root
sheath of Hertwig, continues to grow apically.
The epithelial root sheath induces the
differentiation of odontoblasts which form root
dentin. The apical most portion of the root
sheath turns inward toward the radicular pulp
cavity (that portion of the pulp cavity inside
the root) and is called the epithelial
diaphragm.
59. EPITHELIAL ROOT SHEATH OF HERTWIG &
EPITHELIAL DIAPHRAGM
EPITHELIAL ROOT SHEATH
OF HERTWIG
EPITHELIAL
DIAPHRAGM
63. • Hertwig's root sheath determines the
number, size and shape of roots and
is presumably the inductor of dentin
formation in the developing root.
64.
65. THE EPITHELIAL ROOT SHEATH OF
HERTWIG
• The epithelial root sheath is made up of inner
and outer enamel epithelial layers without the
other two interposing layers. Following the
induction of odontoblast and dentin formation,
the epithelial root sheath disintegrates forming
epithelial rests, small groups of epithelial cells
that can remain around the root.
66. Tooth eruption is defined as
“ The movement of a tooth from its
site of development within the
alveolar process to its functional
position in oral cavity,”
68. Factors consideration in tooth
eruption
• development of
periodontium, root, pulp,
alveolar bone
• events during eruption
– eruptive pathway: gubernacular
canal
