The document provides a detailed overview of dentin, covering its definition, properties (physical and chemical), and formation through odontoblast differentiation and histology. It discusses dentinogenesis, including matrix formation and mineralization, along with the structure and arrangement of dentinal tubules. Additionally, it highlights the differences between mantle dentin and circumpulpal dentin, including fiber types, thickness, and mineralization processes.

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