For my dental students

1. Dentinogenesis & Histology
Of Dentin
Dr/ Hesham Dameer

2. 1. Dentinogenesis
2. Physical properties of dentin
3. Chemical composition
4. Dentin structure
5. Types of dentin
6. Age changes of dentin
7. Innervation of dentin
8. Theories of pain transmission through dentin

3. Dentinogenesis is a two-phase sequence
in that:
Dentin matrix
formation (predentin)
which is the elaboration
of uncalcified organic
matrix
Mineralization,
which does not begin
until a fairly wide
band of predentin is
formed.
Collagen fibers
Ground
substance
Hydroxyapatite
crystals
1
2

4. Primary physiologic dentin formation
• Mantle dentin
• Circumpulpal dentin
Primary physiologic dentin is the dentin formed
prior to root completion, it is formed of :

5. Odontoblasts differentiation
1. Dentin is formed by odontoblast cells that
differentiate from ectomesenchymal cells ( EMC )
of dental papilla following an organizing influence
of the inner enamel epithelium.
2. Odontoblast differentiation occur in the preexisting
ground substance of the dental papilla

6. 3-EMC of DP undergo a number of cell divisions, in the
final division the mitotic spindles (B) are perpendicular to
the basement membrane supporting the inner E epithelium,
so it gives 2 daughter cells superimposed, the
odontoblasts(C) and the subodontoblastic layer (F).

7. Odontoblast differentiation. The undifferentiated ectomesenchymal cell (A) of the
dental papilla divides (B), with its mitotic spindle perpendicular to the basal
lamina (pink line). A daughter cell (C), influenced by the epithelial cells and
molecules they produce (D), differentiates into an odontoblast (F). Another
daughter cell (E), not exposed to this epithelial influence, persists as a
subodontoblast cell (G). This cell has been exposed to all the determinants
necessary for odontoblast formation except the last .

8. Differentiation of odontoblasts.
Differentiate from
the peripheral
dental papilla cells
(UMC)
At first become
short columnar cell
with many stubby (
short & thick )
processes
Preameloblasts
Basement
membrane
The cells grow in length
(40u) and closely packed
together
Ameloblasts

9. Primary Dentin formation

10. Matrix formation
Forming the bulk of the tooth
dentin . Comprises intertubular
and peritubular dentin Small-
diameter collagen fibrils
parallel to basal lamina .
*Ground substance formed
exclusively by odontoblasts
Glycoprotiens, proteoglycans
and lipids .
Formation of peritubular dentin .
*large-diameter collagen fibrils
perpendicular to basal
lamina(von Korff’s fibers) .
Source : from
Preexisting ground substance
of dental papilla
Glycoprotiens, proteoglycans
Mantle dentin Circumpulpal dentin

12. Odontoblast cells at first have many short
processes, as the odontoblast moves away
toward the center of the pulp, one of its short
processes becomes accentuated and left behind
to form the principal extension of the cell, the
odontoblast process or Tomes’ fiber

13. Odontoblastic process formation
At first more than one process As more D is laid down, the cells receed
and leave single process ( Tomes’ fiber)

15. Changes in the dental papilla associated with initiation of dentin formation. A, An acellular
zone (*) separates the undifferentiated cells of the dental papilla (preodontoblasts, pOd)
from the differentiating inner enamel epithelium (ameloblasts, Am). B to D, Preodontoblasts
develop into tall and polarized odontoblasts (Od) with the nucleus away from the matrix they
deposit at the interface with ameloblasts. The matrix first accumulates as an unmineralized
layer, predentin (PD), which gradually mineralizes to form mantle
dentin (D). Odp, Odontoblast process; SI, stratum intermedium; SR, stellate reticulum.

16. A, The odontoblast process (Odp) is the portion of the cell that extends above the cell web (cw). Numerous typical,
elongated secretory granules (sg), occasional multivesicular bodies (mvb), and microfilaments (mf) are found in the
process. The small collagen fibrils (Coll) making the bulk of predentin run perpendicularly to the processes and
therefore appear as dotlike structures in a plane passing longitudinally along odontoblasts. Bundles of larger-diameter
collagen fibrils, von Korff’s fibers, run parallel to the odontoblast processes and extend deep between the cell
bodies. B, At higher magnification, a von Korff’s fiber extending between two odontoblasts shows the typical fibrillar
Transmission EM image
Korff’s fiber between 2 odontoblasts

17. Mineralization
The hydroxyapitite crystals first
appear in matrix vesicles (in the
cytoplasm of odontoblasts) as
single crystals that grow rapidly
fuse with the cell membrane and
rupture to spread as cluster of
crystallites that fuse with
adjacent clusters to form a
continuous layer of mineralized
matrix.
Mantle dentin
( Matrix vesicles are generated by odontoblasts )

18. Dentinogenesis requires a good blood supply, during mantle
dentin formation blood capillaries are found in the
subodontoblastic layer. As circumpulpal dentinogenesis is
initiated these capillaries migrate between the odontoblasts.
No matrix vesicles are
generated by odontoblasts and mineralization
involves heterogeneous nucleation .
With continued crystal growth, globular masses are
formed, that continue to enlarge and fuse to form a
single calcified mass.
Circumpulpal dentin

19. Circumpulpal dentin
Mantle
dentin
Circumpulpal dentin.
The fibers are
parallel to DEJ ( right
or oblique angle to
DT)
Crowding of the
cells and
appearance of
junctional complex

20. Mantle dentin
• Thickness: 10-20 um
• Diameter of collagen
fibers: large (0.1-0.2 um)
• Direction of collagen
fibers : have right angle to
DEJ and parallel to
basement membrane in
root
• Ground substance: from
odontoblasts and the cell
free zone
• Mineralization: linear
form (contains matrix
vesicles).
Circumpulpal dentin
• Thickness: bulk of the tooth
• Diameter of collagen fibers:
small (0.05um)
• Direction of collagen fibers :
have right or oblique angle to
dentinal tubules (parallel to
dentin surface)
• Ground substance: from
odontoblasts
• Mineralization: Globular below
mantle dentin then become
mixed in the remaining
circumpulpal dentin (no M V ).
Crown Root

21. Matrix formation Mineralization

22. Pattern of mineralization
1. Globular calcification.
2. Linear calcification.
Depend on the rate of dentin formation

23. Globular mineralization
Involves the deposition of crystals in several discrete
areas of matrix ,with continuous growth globular
masses are formed that continue to enlarge and then
fuse to form single calcified mass, this pattern is best
seen in mantle dentin.
In circumpulpal dentin the mineralization front may be
globular or linear.

24. Globular mineralization

25. Globular mineralization

26. Linear mineralization
The type of mineralization depends on the rate
of dentin formation, the largest globules
occurring where dentin deposited faster.
When the rate of formation progress slowly, the
mineralization front appears more uniform
and linear.

27. Linear mineralization

28. Dentin Structure

29. Physical Properties
1. Light yellowish in color.
2. Slightly compressible and highly
elastic.
3. Harder than bone and softer than
enamel.
4. More radiolucent (in X-ray)than
enamel.
5. More radiopaque than cementum
or bone.

30. Chemical Composition
1. Organic matter (collagen fibrils and a ground
substance) 20% and water 10%
2. Inorganic materials 70% : hydroxyapatite crystals
3Ca3(PO4)2.Ca(OH)2
Organic and Inorganic substances can be separated
by decalcification or incineration.

31. Dentin Structure
1. Dentinal tubules.
2. Odontoblastic processes.
3. Peritubular dentin.
4. Intertubular dentin.
5. Predentin.

32. L.S. showing pulp, dentin, PDL, and bone . H&E stain
DP PDL
B

33. 1. Dentinal Tubules
*In the crown, DT follow a gentle curve (S-
shaped)except under the incisal edges and cusp
tips(straight)
*Start at right angle from pulpal surface, the
first convexity toward the root apex.
*In the root, their course are almost straight.

34. LGS section showing the course
of dentinal tubules

35. Dentinal Tubules
Coronal dentin
Root dentin
By Hesham Dameer

36. *The ratio between the surface areas at the
outside and inside of the dentin is 5:1.
*Accordingly, the tubules are further apart in
the peripheral layer and are closely packed near
the pulp.

37. Dentinal tubules – A: near DEJ, B: near the pulp (EM X3.000
A B

38. *DT exhibit secondary curvature over their
entire length.
*Have lateral branches (canaliculi), 1 um in
diameter, at right angle to the tubule.
*Have terminal branches – more in root dentin
than in coronal dentin.

39. Terminal branching of dentinal tubules

40. Dentinal tubules

41. Canaliculi in the dentinal tubules. SEM X 15.000

43. 2. Odontoblastic Processes (Tome’s fibers)
*Are cytoplasmic extensions of the odontoblasts
occupying the DT .
*They are thicker near the cell body, 3-
4micrometer, and taper to 1mic. further into the D.
*They divided near their terminal ends into
several terminal branches.
*They send out thin 2ry processes enclosed in
fine tubules to unite with neighboring ones.

44. Dentinal tubule(A) – Odontoblastic process(B)

45. SEM
TEM
OPD: Odontoblast processes, Arrowheads: Dentinal
tubules

46. Lateral communication between dentinal tubules.
Note terminal branches

47. Lateral communication between dentinal tubules

48. *Some terminal branches extend into the enamel
as enamel spindle.
*Others may remain short in dentinal tubules.
*Occasionally a process splits into 2 equally thick
branches.

49. LGS showing enamel spindle

50. The cytoplasmic contents include:
1. Microtubules of 200-250 A0 in diameter.
2. Filament of 50-75 A0 diameter.
3. Occasional mitochondria.
4. Some dense bodies resembling lysosomes.
5. Coated vesicles.
6. Microvesicles.
Note: (absence of ribosomes and endoplasmic reticulum).

51. 3. Peritubular Dentin
*Best seen in cross sections
*It forms a ring shaped transparent zone surrounding
the odontoblastic process forms the wall of the DT.
*Peritubular D is more mineralized (9%) than the
Intertubular dentin.

52. Peritubular(A), Intertubular dentin(B) and
Odontoblast process space(C)

53. Dentinal tubules
Peritubular dentin Intertubular dentin

54. 4. Intertubular Dentin
Forms the main body of Dentin, located between the DT.
½ of its volume is organic matrix (fibrils and ground substance).
Collagen fibrils are randomly oriented around the DT .
They run parallel to D surface, at right angles to the tubules.
Hydroxyapatite crystals(1um length) are formed parallel to the
Collagen F. .

55. Near the pulp – random arrangement of calcifying collagen
fibers surrounding dentinal tubules. SEM X 15.000

56. Collagen fibers composing the walls of dentinal tubules

57. Canaliculi(white arrow) – peritubular dentin(black arrow)

58. 5. Predentin
Is the first formed dentin (not mineralized).
Located adjacent to the pulp tissue.
Width: 2-6 um.
Mineralized to become Dentin and new layer of
predentin forms circumpulpally.

59. C
A: Dentin B: Predentin

60. P
D
O
D
p
A: Dentin B: Predentin, O: Odontoblasts

61. Types of Dentin

62. 1. Primary physiologic Dentin
(Mantle and Circumpulpal)
*The first formed layer beneath enamel and
cementum is known as mantle D. Mantle dentin is
about 20 um thick.
*It contains coarse fibril bundles (Korff’s fibers)
arranged at right angles to the D surface.

63. *The remaining portion of dentin that forms the main
bulk of the tooth is known as circumpulpal dentin.
*It is more mineralized than mantle D.
*Collagen fibrils are fine and closely packed together.
*It represents all dentin formed prior to root completion

64. 2. Secondary physiologic Dentin
*Formed under normal condition and may continue
throughout life.
*Formed after root completion.
*It is separated from 1primary Dentin by dark stained
line, the Dentinal Tubules bend sharply at this line.

65. *In 2ry D the D T are comparable to those of 1ry D
both in regular arrangement & in numbers
*It is deposited more in the floor and roof of the
pulpal chamber than on the side walls.
*It is deposited also at the pulp horns, reducing their
hight.

66. SD
PD
GS showing the sharp bend between primary PD & secondary dentin SD

67. D S : showing primary & secondary dentin

68. 3. Reparative Dentin
*Noxious stimuli (Attrition, erosion, abrasion, caries or
operative procedures) may expose or cut the
odontoblast processes.
*The entire cell may severely damaged and continue to
form reparative D or degenerates and replaced by
undifferentiated pulpal cells.

69. *Reparative (tertiary) dentin seals off the area of
injury ( defense mechanism of the pulp) so, it is
localized to the site of the stimulus.
*Here the tubules are twisted and reduced in number.

70. *Reparative D is separated from
1ry or 2ry D by a deeply
stained line.
*Some D forming cells may be
included ( entrapped ) in rapidly
produced matrix forming
(osteodentin).

71. Types of Dentin

72. Pulp healing – dentin bridge with normal pulp

73. 4. Interglobular Dentin
*It is the unmineralized or hypomineralized regions located
between the unfused mineralized globules of cacification.
*It is observed in the circumpulpal dentin just below the mantle
dentin.
*The DT pass uninterrupted through the uncalcified areas of IGD.
*IGD follow the incremental pattern of the tooth.
*In ground section the IGD is lost, replaced by air and the spaces
appear black.

74. SEM showing Globular dentin

75. Decalcified H & E stained section showing A: Globular dentin
B: Predentin

76. Interglobular Dentin
Inter-
globuler
dentin
Dentinal
Tubules
Dentino
Enamel
Junction

77. Interglobular dentin in decalcified & ground sections

78. 5. Tome’s Granular Layer
*Seen in the ground section adjacent to cementum (CDJ).
*Made of minute areas of IGD.
*It does not follow the incremental pattern.
*It represents an interference with mineralization of surface layer
of root dentin before cementum formation.
*It may result from the looping and coalescing of the terminal
branches of the DT as a result of the odontoblasts turning on
themselves during early stages of root D formation (recent
evidence).

79. Ground LS showing Tome’s granular layer

80. Dentin
Cementum
Granular layer
of Tomes
By Hesham Dameer

81. 6. Transparent (Sclerotic) Dentin
*Stimuli may lead to deposition of Ca salts (apatite
crystals) in or around degenerating odontoblastic process
(defense mechanism of Dentin).
It Can be observed:
1. In roots of elderly teeth.
2. Around the dentinal part of type B enamel lamellae.

82. Ground LS showing Enamel caries and sclerotic dentin
(dye-filled dentinal tubules)

83. 3. Under slowly progressing caries.
4. It is harder than normal dentin.
5. Seen only in ground sections.
6. Appears light in transmitted and dark in reflected
light.

84. 7. Dead Tracts
*Seen in ground sections of normal dentin.
*Odontoblastic processes disintegrate ( due to caries, attrition,
cavity prep., etc…) and empty tubules filled with air appear.
*Appear black in transmitted light and white in reflected
light.
*Reparative D seals these tubules at their pulpal end.
*These areas demonstrate decreased sensitivity.

85. Dead tract
Ground LS showing Reparative dentin

86. Age and Functional Changes
1. Vitality of dentin.
2. Attrition.
3. Permeability.
4. Secondary dentin.
5. Reparative dentin.
6. Dead tract.
7. Sclerotic dentin.

87. Incremental Lines of dentin
1. Daily Incremental lines
2. Incremental lines of Von Ebner.
3. Contour lines of Owen ( hypocalcified
bands).
4. Neonatal line.

88. 2.Incremental lines of von Ebner
*Run at right angles to DT
*Reflect the daily rhythmic deposition of
dentin matrix(4-8 Um)
1.Daily Incremental lines
* 5-day rhythmic pattern of dentin
deposition (20 Um interval)

89. Incremental lines of Von Ebner

90. 3.Contour lines of Owen
 Contour lines are accentuated incremental lines result from
disturbances in mineralization process ( periods of illness or
inadequate nutrition)
 Soft x-ray analysis showed these lines as hypocalcified bands.
4. Neonatal line
1. In deciduous teeth and in the first permanent molar, accentuated
incremental line separates between prenatal and post natal
dentin.
2. It reflects the abrupt change in environment that occurs at birth.
3. It may be a zone of hypocalcification.

91. Contour line of Owen(arrowed)

92. Vitality of D:
*Dentin is a vital tissue since the odontoblasts and their
processes are an integral part of it.
*Vitality is the capacity of the tissue to react to
physiologic and pathologic stimuli
*Pathologic effects of caries, abrasion, attrition or
operative procedures cause changes in D

93. Innervation of Dentin
*Dentin is sensitive to any kind of stimuli.
*Silver impregnation is not specific to demonstrate nerve
fibers.
*DT contain numerous nerve endings in the predentin and
inner dentin (100-150 um) in close association with the
odontoblastic processes within the tubules.

94. *Nerve endings are numerous in the pulp horns.
*Nerve endings are packed with small vesicles containing
neurotransmitter substances. Most of these endings are
terminal processes of the myelinated nerve fibers.
*The primary afferent somatosensory nerves of the dentin
and pulp project to main sensory nucleus of the
midbrain.

95. Theories of pain transmission
through Dentin

96. A: Direct conduction Theory
B: Transduction Theory
C: Hydrodynamic Theory
A B C

98. 1. Direct Conduction Theory:
*In which stimuli in some manner as yet unknown,
directly reach the nerve endings in the inner dentin
in the tubules.
*There is little scientific support of this theory.

99. 2. Transduction Theory:
*In which the membrane of the odontoblastic process is
the primary structure excited by the stimulus and that
the impulse is conducted or transmitted to the nerve
endings in the predentin, odontoblast zone, and pulp.
*This is not a popular theory since there are no
neurotransmitter vesicles in the odontoblastic process to
facilitate the synapse.

100. 3. Hydrodynamic Theory
*In which various stimuli such as heat, cold, air blast
desiccation, mechanical or osmotic pressure affect fluid
movement in the DT
*This fluid movement, either inward or outward, stimulates
the pain mechanism in the tubules by mechanical
disturbance of the nerves endings closely associated with
the odontoblast and its process.
*Thus these endings may act as mechanoreceptors as they
are affected by mechanical displacement of the tubular
fluid.

101. • Ten Cate’s AR (Oral Histology ,development ,
structure and function ) 8th edition, Antonio
nanci. Elsevier Health Sciences, 2008.
• Orban’s Oral Histology and Embryology, 13th
edition, G S Kumar. Elsevier India, 2011.