I. Definition II. Properties A. Physical B. Chemical III. Dentin formation 1. Odontoblast A. Differentiation B. Histology 2. Dentinogenesis A.Matrix formation B. Mineralization

2. DENTIN
Menatalla M. Elhindawy

4. DENTIN
Definition
Properties
• Physical
• Chemical
Dentin formation
• Odontoblast
A. Differentiation
B. Histology
• Dentinogenesis
A. Matrix formation
B. Mineralization

5. DENTIN
Definition
• Bulk of the tooth
• Mineralized
• Vital
• Shape of the crown
• Number and size of the roots

6.  Color… yellowish “ light yellow in deciduous and pale yellow in permanent, gets
darker with age.
 Hardness.. Elastic, less than enamel and harder then cementum, harder in permanent
than deciduous.
 Thickness… 3-10mm.
 Radio-opacity.. Less radio-opaque than enamel.
 Permeability … permeable, more permeable at cervical region, permeability decreases
with age.
DENTIN
Properties

7. DENTIN
Properties
Inorganic
, 70%
organic ,
20%
water ,
10%
By weight
Inorganic
, 45%
organic ,
33%
water ,
22%
By volume

8. DENTIN
Properties
 In-organic component in the form of hydroxy-apatite crystals, smaller
in size than enamel crystals.
 Organic component in the form of collagen type I “ some of type III” &
ground substance “ muco-polysaccharides, glycose-aminoglycans &
proteoglycans”

9. DENTIN
Dentin formation
• Odontoblast
A. Differentiation
B. Histology
• Dentinogenesis
A. Matrix formation
B. Mineralization

10.  Highly differentiated
 Highly polarized
 Post-mitotic cells
 Originated from neural crest cells.
 Cell body & process
DENTIN
Odontoblast

11. DENTIN
Odontoblast Differentiation
 At early bell stage, the IEE changes from short to tall columnar cells leading to gradual
obliteration of the cell free zone.
 Cells of dental papilla become in contact with IEE separated only by basal lamina,
cells of dental papilla undergo the last mitotic division “asymmetrical one” producing
2 types of cells
A. Large cells in contact with dental lamina become pre-odontoblasts
B. Smaller cells with stem cell potentials grouped in “Hoehl cell layer
 IEE release some factors that help in the organization of odontoblast cytoskeleton
assembly which is important for relocation of organelles during transformation from
pre-odontoblast to odontoblast.

12. DENTIN
Odontoblast Differentiation
 Pre-odontoblasts differentiate into columnar odontoblast, cells become polarized and
capable to secret the first layer of dentin.
 As the first layer of dentine is formed ameloblasts are differentiated and the first
formed layer of enamel is formed and the ADJ is established .
 As dentin formation precedes, odontoblasts retreats toward the pulp and
odontoblastic process is formed.

13. DENTIN
Odontoblast Differentiation

14. DENTIN
Odontoblast Differentiation

15. 3 stages
I. Secretory odontoblast
II. Transitional odontoblast
III. Aging odontoblast
DENTIN
Odontoblast Histology

16. I. Secretory odontoblast
• Will be discussed
II.Transitional odontoblast
• Narrower cell
• The nucleus is displaced from its basal
location. With condensation of chromatin.
• Decreased amount of rER.
DENTIN
Odontoblast Histology

17. III. Aging odontoblast
• Cells are small flattened
• The nucleus is closed and situated apically.
• The cell is with less cytoplasm and
decreased number of cell organells.
• Secretory granules are absent.
• Resting odontoblasts are capable to
changing into active secretory
odontoblasts.
DENTIN
Odontoblast Histology

18. DENTIN
Odontoblast Histology
I. Cell body
• 40 * 7 µ
• Can divide it into
a. Basal part
• Nucleus surrounded by clusters of
mitochondria while rER occupies
the lateral borders
b. Central part
• Few Golgi, stacks of rER,
immature secretory vesicles
c. Distal part
• Clusters of mitochondria,
secretory vesicle
• Cell junction “ gap and
desmosome-like junction

19. DENTIN
Odontoblast Histology
II. Odontoblastic process
• Extends from pulp to ADJ
• Tapers from 3-4 µ at the pulpal surface to 1
µ at ADJ
• The process contains only microtubules,
microfilaments & mitochondria
• Branched along its course “lateral and
terminal”
• Contained within Dentinal Tubules

20. DENTIN
Odontoblast Histology

21. DENTIN
Odontoblast Histology
Near pulp Mid- dentin ADJ

22. DENTIN
Odontoblast Histology
III. Dentinal tubules
1. Course
A. Primary course ..
 In the crown.. S shaped “Sigmoid”
with the fist convexity toward the
root in the middle and cervical
13s & straight under cup tip or
incisal edge.
 In in root straight
B. Secondary course..
“Sinusoidal” shaped

23. DENTIN
Odontoblast Histology

24. DENTIN
Odontoblast Histology
III. Dentinal tubules
2. Ratio unite are “pulpADJ”
 5:1
 DT are closely packed near the pulp
and further apart near the ADJ
3. Diameter “pulpADJ”
 4:1
 At the pulpal side 3-4 µ to reach the
ADJ as 1µ
4. Number unite area
 crown>root

25. DENTIN
Odontoblast Histology
III. Dentinal tubules
5. Branches
 Terminal
 Lateral
Note … DTs may cross the ADJ
and become “Enamel spindle”

26. DENTIN
 Definition
 Properties
• Physical
• Chemical
Dentin formation
• Odontoblast
A. Differentiation
B. Histology
• Dentinogenesis
A. Matrix formation
B. Mineralization

27. DENTIN
Dentinogenesis

28. DENTIN
Dentinogenesis
MATRIX
FORMATION
Mantle Dentin
Circumpulpal
Dentin
Mineralization

29. I. Mantle Dentin MATRIX
formation
 5 - 20 µ in thickness.
 Collagen fibers are
• Von Kroff’s collagen type
III fibers
• Thick 0.1 -0.2 µ
• Directed perpendicular
to ADJ
 Ground substance
• Preexisting from the cell
fee zone.
DENTIN
Matrix Formation
Mantle D.

30. II. Circumpulpal Dentin MATRIX
formation
 It represents the entire thickness of
D.
 Collagen fibers are
• Type I fibers
• Thin 0.05 µ
• Directed parallel to ADJ &
perpendicular to DT
 Ground substance
• Newly formed by odontoblasts
DENTIN
Matrix Formation
Mantle D.
Ciucumpulpal
D.

31. Pre-dentin
Constant feature of dentin.
Un-mineralized zone between
odontoblasts & mineralized D
 2-6 µ in thickness.
Formation and mineralization
begins at the tip of cusps or
incisal ridge and proceed
cervically.
DENTIN
Mineralization

32. DENTIN
Mineralization
 Mineralization occurs by globular, or calcospheric calcification and it
involves the deposition of the crystals in certain areas.
 Initially mineralization starts by deposition of very fine plates of
hydroxyapatite on the surface of collagen fibrils and the ground
substance, later crystals are deposited within the fibrils themselves.
 Crystals are arranged parallel to the collagen fibers long axis.

33. Globular “calcospheric”
calcification
 Matrix vesicles
 First mineral crystals
 Continued crystal growth
 Globular masses which enlarge
to form single calcified mass
DENTIN
Mineralization
Less mineralized & fewer
defects
Globular “calcospheric” calcification
Or
Linear calcification
Mantle Dentin circumpulpal Dentin

34. DENTIN
Mantle Dentin Circumpulpal Dentin
Thickness 5- 20µ Bulk of the tooth
Diameter of
collagen fibers
Large (0.1-0.2 µ) Small (0.05µ)
Direction of
collagen fibers
Perpendicular to ADJ and parallel to the
dentinal tubules
Parallel to ADJ and perpendicular to the
dentinal tubules
Ground substance
Pre- existing from dental papilla cell free
zone and the odontoblasts.
Formed by the odontoblasts only
Mineralization Globular Globular or linear