1. UNIVERSITATEA DE STAT DE MEDICINĂ ŞI FARMACIE “NICOLAE
TESTEMIŢANU”
Teeth and supporting tissues.
Development and structure of the
teeth.
CATEDRA HISTOLOGIE, CITOLOGIE ŞI EMBRIOLOGIE
TATIANA GLOBA

2. TOOTH STRUCTURE
CROWN
(enamel layer
over dentin)
(anatomical &
clinical)
NECK (acellular
cementum +
dentin )
ROOT (cellular and
acellular calcified
cementum over
dentin)

3. Clinical Crown
Anatomical Crown

4. Tissues of the teeth can
be divided into 2 groups:
hard and soft tissues.
Hard tissues of the tooth:
• ENAMEL
• DENTIN
• CEMENTUM
Soft tissue of the tooth:
• DENTAL PULP
(crown pulp & root
canal)

5. Enamel
• is a cell free
extracellular tissue.
• is the translucent
outer layer of the
tooth.
• is the hardest
substance in the
human body.
Consists of:
- 96% inorganic salts
- 4% organic
substances-
glycoproteins
enamelin.

6. Enamel
• Is an extracellular product of enamel organ
cells.
• Is produced by the AMELOBLASTS.
• Consists of RODS or PRISMS (the morpho-
functional unit of enamel).

7. Dentin
• forms the bulk of the tooth.
• It supports enamel and
acts as the skeleton of the
tooth.
• It is the second hardest
tissue in the human body.
Consists of:
- 72% inorganic salts (Ca
phosphate, Mg phosphate)
- 28% organic substances
(collagen type I,
proteoglycans and
glycoproteins).

8. Dentin
• Is produced by the ODONTOBLASTS (these
cells have cylindrical cell body and a long
cytoplasmatic extension, the odontoblastic
process).
• Dentin is a living tissue, it has the ability for
constant growth and repair that reacts to
physiologic (functional) and pathologic (disease)
stimuli.
• The dentin is perforated by dentinal tubules.
Each tubule is filled with an elongated cellular
process of an odontoblast, and nerve endings.

9. Cementum
• is the third mineralized
tissue of the tooth and is as
hard as bone is, but has no
Haversian systems.
• Covers the root of the
tooth in a thin layer.
• Is avascular tissue.
Consists of:
- 50% inorganic salts
- 50 % organic substances
(collagen, proteoglycans).

10. Cementum
• Cells of the cementum are:
– Cementocytes that are located in lacunae
– Cementoblasts that are located on the outer surface of the cementum,
adjacent to the periodontal ligament
• Cementum is capable of formation, destruction and repair and
remodels continually throughout life. It is nourished from
vessels within the periodontal ligament.
• Functions:
– It protects the dentin (occludes the dentinal tubules)
– It provides attachment of the periodontal fibers
– It reverses tooth resorption
• There are 2 types of cementum:
I. Cellular – contains cementocytes and cementoblasts
II. Acelular – has no cells.

11. Soft tissue of the
tooth:
Pulp - consists of loose
connective tissue,
contains blood vessels &
nerve fibers, cellular
content: odontoblasts,
fibroblasts, fibrocytes,
macrophages,
lymphocytes, mast cells,
plasma cells & other.
Root canal - canal in
the root of the tooth
where the nerves and
blood vessels travel
through.

12. Blood vessels -
carry nutrients to
the tooth.
Nerves - relay
signals such as
pain to and
from brain

13. Periodontal
Ligament
• Provides for
attachment, support,
bone remodeling
(during movement of
a tooth), nutrition of
adjacent structures,
proprioreception and
tooth eruption.

14. Bone - alveolar
bone forms the
tooth socket and
provides it with
support.

15. 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

16. FUNCTIONAL STAGES OF
TOOTH DEVELOPMENT
• Initiation
• Proliferation
• Morpho-differentiation and
Histo-differentiation
• Apposition
• Root development

17. MORPHOLOGICAL STAGES
OF TOOTH DEVELOPMENT
• Bud stage
• Cap stage
• Bell stage (early & late)
• Early & late crown
• Early root formation

18. 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

19. BUD stage CAP stage
LATE CROWN stage
BELL stage

20. PRIMITIVE EPITHELIAL BAND
1
2
Is subdivided into: 1. VESTIBULAR LAMINA
2. DENTAL LAMINA

21. Teeth are organs which develop primarily through inductive
interactions between dental epithelium and surrounding
ectomesenchyme.
Bud stage - oral epithelium proliferates and a plate of epithelium
grows into the underlying ectomesenchyme and form the dental
lamina. Shortly after appearance dental lamina increases its
mitotic activity and form epithelial structures,called tooth buds.

22. 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

23. Cap stage
• During the cap stage, an unequal growth (mitotic
activity) of epithelial cells grows down to form a
concavity around the mesenchyme. The tooth bud
differentiates into a cap-shaped enamel organ
extending from the dental lamina.
• Enamel organ is composed of 3 layers:
– The convex OUTER ENAMEL EPITHELIUM
– The concave INNER ENAMEL EPITHELIUM
– STELLATE RETICULUM
• During the cap stage are formed the dental papilla &
dental sac

24. ENAMEL ORGAN
1
2
Enamel organ consists of: 3
1. Outer enamel epithelium
2. Stellate reticulum
3. Inner enamel epithelium

25. • DENTAL PAPILLA: is a concentration of ectomesenchyme,
which is in part enveloped by the invaginated inner enamel
epithelium. Mesenchymal cells within the dental papilla are
responsible for formation of tooth pulp. The dental papilla
contains cells that develop into ODONTOBLASTS, which are
dentin-forming cells.
• DENTAL SACK: is a concentration of ectomesenchyme that
encircles the enamel organ and the dental papilla. The dental
sack gives rise to three important entities: cementoblasts,
osteoblasts, and fibroblasts. Cementoblasts form the
cementum of a tooth. Osteoblasts give rise to the alveolar bone
around the roots of teeth. Fibroblasts develop the
periodontal ligaments which connect teeth to the alveolar
bone through cementum.

26. CAP stage
7 – dental papilla
8 – dental sac

27. HISTO-DIFFERENTIATION & MORPHO-
DIFFERNTIATION. BELL stage

28. Bell stage
• is known for the histodifferentiation and morphodifferentiation
that takes place.
• The caracteristics of the stage:
– Cellular differentiation
– Morphological specialization, both with alternative,
inductive and receptive role.
• We recognized two different processes during this stage:
– Dentinogenesis (cells at the periphery of the dental papilla
differentiate into odontoblasts and begin to elaborate
predentin and dentin) – which precedes and follows what
comes next, that is
– Amelogenesis (cells of the inner enamel epithelium
differentiate into ameloblasts which begin to elaborate
enamel)
• The dentin and enamel adjoin each other and the junction
between them is called the dentino-enamel junction.

29. INNER ENAMEL EPITHELIUM
PREAMELOBLASTS ODONTOBLASTS
Initiate the differentiation
of

30. ENAMEL ORGAN (bell
stage)
Consists of 4 epithelia:
1. Outer enamel epithelium
2. Stellate epithelium
3. Stratum intermedium
4. Inner enamel epithelium
1.
2.
3.
4.

31. ENAMEL ORGAN
2.
3.
1.
4.

32. 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

33. APPOSITION. LATE CROWN stage
• Deposition of the dentin & enamel occurs by apposition
with alternation of active & resting states

34. PREDENTIN ENAMEL
DENTIN

35. Histogenesis of tooth tissues

36. 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

37. 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.

38. 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,”
Stage of tooth eruption
• Pre-eruptive
• Eruptive (intraosseous & extraosseous)
• Post-eruptive