1. Tissue of the teeth Dentin-Pulp Complex Dr Jamal Naim
PhD in Orthodontics
Dentin-Pulp Complex

2. Introduction
Dentin and pulp are related embryologically, histologically and functionally.
Dentin is a hard connective tissue and the Pulp is a soft one.
Dentin forms the bulk of the tooth.
It is covered by cementum at the root portion and by enamel at the crown portion.

3. Properties of dentin Bonelike yellowish in color
Elastic, less hard than enamel, but more than cementum
Less radio-opaque than enamel, but more than cementum
3-10 mm thick

4. Compositions of dentin
organic substance
30-25% from its weight
About 90% collagen fibers
About 10% ground substance
inorganic substance
70-75% from its weight
Hydroxyapatite crystallites

5. Life cycle of odontoblasts
There are only 3 stages in the life cycle of odontoblasts:
Differentiating stage
Formation stage
Quiescent stage

6. Life cycle of odontoblasts
Differentiating stage:
Before Differentiation, the inner dental epithelium is separated from the dental papilla by the thin basement membrane.
The undifferentiated peripheral cells are spindle and separated by great amount of ground substance

7. Life cycle of odontoblasts

8. Differentiating stage
Preameloblast
Basement membrane
Undifferentiated cell

9. Life cycle of odontoblasts
Differentiating stage:
In the late bell stage, under the inductive influence of the inner dental epithelium, the peripheral ectomesenchymal cells differentiate into preodontoblasts.

10. In the late bell stage the UMC differentiate to preodontoblasts

11. Differentiating stage
Ameloblast
Basement membrane
preodontoblast
Undifferentiated cell

12. Late Bell stage/differentiating stage for odontoblasts

13. Life cycle of odontoblasts
They assume to a columnar shape and aligned as a single row along the basement membrane.
Several projections arise from the upper part of the cells.

14. Life cycle of odontoblasts
The nuclei become basally oriented.
The cells grow in length to become columnar (40u)
Now the fully differentiated odontoblasts begin their work.

15. Life cycle of odontoblasts
Formative stage:
Concentration of the cell organelles, granular components and globular elements
Production of the dentin matrix
The odontoblasts retreat from the basement membrane

16. Life cycle of odontoblasts
Formative stage:
Leaving a single process which become enclosed in the dentinal tubule (Tomes fiber).
With successive deposition of dentin, tubule and process grow in length.

17. Life cycle of odontoblasts
Differentiating stage/
Begin of formative stage
predentin
odontoblast
Undifferentiated cell

18. Mitochondrion
RER
Formative stage
Nucleus
predentin
Formative stage

19. Formative stage
Dentin

20. Life cycle of odontoblasts
Quiescent stage:
Actively secreting odontoblasts decrease slightly in size.
The odontoblastic process stop to elongate
In this stage the odontoblasts produce only secondary dentin.

21. Life cycle of odontoblasts
Quiescent stage:
Odontoblasts decrease in size and function
The dentin formation is reduced
They produce now secondary and tertiary dentin

23. Dentinogenesis Matrix Formation (forming predentin) Maturation
Collagen fibers
Ground substance
Maturation
(mineralization)
Hydroxyapatite crystallites

24. Dentinogenesis Formation of predentin (dentin matrix):
The first indication of forming predentin is the development of the KORFF FIBERS.
They are bundles of fibrils among the odontoblasts.
They are perpendicular to the basement membrane and attached to it.
This layer is main part of the MANTLE DENTIN

25. Basement membrane MANTLE DENTIN TOMES FIBER
Korffs fibers are perpendicular to the basement membrane
TOMES FIBER

26. Dentinogenesis
The korffs fibers fade gradually and smaller fibrils form a network in the dentin subsequent to the mantle dentin, the circumpulpal dentin.
The odontoblasts form the main components of the dentin matrix:
the collagen fibers and
the mucopolysaccharides.

27. Basement membrane MANTLE DENTIN CIRCUMPULPAL DENTIN TOMES FIBER
fibers are parallel to the DEJ
TOMES FIBER

29. Dentinogenesis Maturation of predentin:
It occurs parallel to matrix formation
It begins at the tip of the crown
It proceeds in a rhythmic pattern to gradually complete cervically.
The first layer of predentin begins its maturation in a globular pattern (matrix vesicle), where small centers of calcification spread concentrically until they fuse together.

30. Dentinogenesis
If somewhere those globules do not fuse together, areas of uncalcified dentin are known as interglobular dentin.
The maturation goes then in linear or occasionally globular pattern.
The mineralization begins by crystal deposition in form of fine plates of hydroxyapatite on the surface of the collagen fibrils.
The long axes of the crystals are paralleling to the fibrils.

31. Maturation of dentin MANTLE DENTIN CIRCUMPULPAL DENTIN Mineralized MD
Matrix vesicle
Rupture of the MV and begin of mineralization
Maturation of dentin

32. Maturation of dentin Matrix vesicle
Begin of Crystallization
Matrix vesicle
Crystal lodgment
Rupture of the MV and begin of mineralization
Maturation of dentin

34. Types of dentin Primary (physiological formed) dentin
Secondary (physiological formed) dentin
Tertiary (reparative, irregular secondary) dentin

35. Enamel
Mantle dentin
Circumpulpal dentin
Tertiary (irregular secondary) dentin
regular secondary dentin

36. Primary dentin
All of dentin formed before root formation has been completed is Primary dentin.
Physiological formed primary Dentin is composed of:
Mantle dentin &
Circumpulpal dentin

37. Histological structure of dentin
Odontoblasts & their process
Dentinal tubules (canals)
Peritubular dentin
Intertubular dentin
Interglobular dentin
tome's granular layer

38. Circumpulpal dentin
Pulp
Pulp
predentin
Odontoblasts layer

39. Oral Histology, 5th edition, A R Ten Cate
Odontoblasts & their process
©Copyright 2007, Thomas G. Hollinger, Gainesville, Fl
Oral Histology, 5th edition, A R Ten Cate

40. Odontoblasts & their process
Odontoblasts are specialized in dentin forming (primary, secondary or tertiary).
arranged in a well defined layer Adjacent to the pulpal end of dentin.
Every cell has one process (tomes fiber) that traverse dentin to reach the D.E.J and the C.D.J.
Adjacent to enamel and cement the odontoblastic process ends by formation of several terminal branches.

41. Odontoblasts & their process
It is about 5000 µm long.
The process is about (4-5 µm) thick.
It becomes smaller in predentin (1-3 µm) and more smaller in mineralized dentin ( µm).
They have several smaller branches (terminal branches), that fuse with the adjacent processes terminal branches.

42. Dentin
Predentin
odontoblasts

43. Dentinal Tubules

44. DEJ
terminal branches
Odontoblastic processes

45. Dentinal tubules
They are s-shaped in the crown-dentin and more straight in the root-dentin.
They have lateral branches (canaliculi) enclosing the terminal branches.
The density of the tubules is higher at the pulpal end of dentin (64000 DT/mm2) than at the D.E.J (16000 DT/mm2).

46. Dentinal tubules
The diameter of the DT at the D.E.J. is smaller than at the pulpal end of dentin.
The density decreases also from coronal toward apical dentin.

47. S-shaped Dentinal tubules

48. Dentinal Tubules periodontoblastic space
Odontoblastic process (tomes fiber)

49. Peritubular dentin
It is the layer of dentin surrounding the dentin tubules
It is highly mineralized more homogenous than intertubular dentin
It has less than 20% of its volume an organic matrix, so it has higher x-ray opacity than intertubular dentin
Its thickness varies according to age (thicker in old dentin) and location.

50. Peritubular dentin (Neumann sheath)

51. Intertubular dentin It is the sum of dentin between the dentin tubules
It is less mineralized and less homogeneous than PTD
It has more than 50% of its volume an organic matrix, so it has less x-ray opacity than peritubular dentin
The collagen fibrils surround the tubule and form a network between them

52. Peritubular dentin (Neumann sheath)
Intertubular dentin
Peritubular dentin (Neumann sheath)
Odontoblastic process (tomes fiber)

53. Mantle dentin
Circumpulpal dentin

54. Mantle dentin
It is the first formed layer of dentin and is about 30 µm thick.
It is less mineralized than circumpulpal dentin
The difference between it and CPD in ground sections is the direction of the collagen (korff´s) fibrils. They are rectangular to the dentino-enamel or cemento-enamel junction
It hasn’t growth lines (von Ebner lines) like CPD

55. Mantle dentin
In ground section D.E.J. and C.D.J appears as scalloped line. There is more irregularity in the cusp and crown area.
Cement
Enamel
Dentin
Dentin
D.E.J. and C.D.J

56. Incremental lines of von Ebner
Like the lines of Retzius in enamel, the incremental lines of von Ebner show the growth pattern and the daily deposition of dentin.
They are hypomineralized lines of dentin and corresponds the rest of odontoblasts.
The distance between them varies from 3-20 µm.
They run in rectangular direction to the dentin tubules

57. Contourline of Owen
If any thing (disease, fever etc.) disturbs the dentin development, the lines of von Ebner are wider and less mineralized. They are called then contourlines of Owen.
The best known contour lines of Owen is the neonatal line.
It corresponds the first weeks of a baby life, because of the change of nutrition.

58. Owen contourlines

59. neonatal line

60. Interglobular dentin
The mineralization of dentin runs in globular pattern
If the globules doesn’t fuse completely together, the hypomineralized dentin among them is known interglobular dentin.
Those areas follow the course of the von Ebner lines.
The tubules in those areas hasn’t peritubular dentin

61. Tome's granular layer
Black spaces in the ground section adjacent to the CDJ, so only in the root mantle dentin
They are also hypomineralized areas of dentin, but smaller the interglobular dentin
They doesn’t follow the lines of von Ebner.

62. Tome's granular layer cementum Granular layer of Tomes
Dentin (with tubules)
©Copyright 2007, Thomas G. Hollinger, Gainesville, Fl

63. Granular Layer of Tomes
dentin
enamel
cementum

64. Areas of hypo-mineralized dentin Areas of hypo-mineralized dentin
Interglobular dentin
Tome's granular layer
Size: large
Size: small
Areas of hypo-mineralized dentin
Areas of hypo-mineralized dentin
In crown and root dentin
Only in mantle root dentin
Follows incremental lines
Doesn’t follow incremental lines

65. Age and functional changes
Physiologic regular secondary dentin
Pathologic irregular secondary dentin
Transparent (sclerotic) dentin

66. Physiologic regular secondary dentin
Primary D
Secondary D

67. Physiologic regular secondary dentin
This is the type of dentin formed under Physiologic conditions after complete root formation.
It is deposited continuously as long as the pulp is vital.
It is formed at a lower rate and is separated by a darkly stained line from primary dentin
It has less number of tubules.
It occurs in the entire pulpal surface.
Higher deposition at the roof and floor of the pulp chamber.

68. Physiologic regular secondary dentin
Reparative D
CPD
CPD

69. Physiologic regular secondary dentin
The size of the pulp cavity decreases and obliteration of the pulp horns
The course of the dentin canals is more irregular

70. Pathologic irregular secondary dentin
It is also known as tertiary or reparative dentin
This type of dentin is formed as a protection for the pulp against severe stimulus (pathological conditions or irritations), such as
Attrition
Caries
Preparations
It is formed at a localized area (e.g. pulp horn)
Some UMC in the subodontoblastic layer differentiate to new odontoblast to form dentin.

71. Pathologic irregular secondary dentin
The number of the tubules is reduced.
Tertiary dentin has frequently twisted tubules
Some areas doesn’t contain tubules
Reparative dentin is separated from other types by a darkly stained line.

72. Pathologic irregular secondary dentin
Tertiary dentin

73. Types of reparative dentin
Osteodentin: The odontoblasts (cells) are included in the formed dentin

74. Types of reparative dentin
Atubular dentin: areas without tubules

75. Types of reparative dentin
Vasodentin: entrapped blood vessels

76. Types of secondary dentin
irregular
Cause: severe stimuli, severe attrition, erosion, deep caries,
Site of formation: located (eg pulp horn)
Tubules: wavy and twisted course, decrease in number or atubular
Regular
Cause: mild stimuli (slow attrition, slowly progressing caries)
Site of formation: entire pulpal surface (thicker on pulp roof and floor)
Tubules: wavy course, decrease in number

77. Types of secondary dentin
Regular
Line of demarcation: stain dark
Clinically:
The increase of the dentin thickness and the closure of the pulp horns make it much less possible to expose the pulp chamber during preparation.
Irregular
Line of demarcation: stain dark
Clinically:
Functions as a barrier for against caries.

78. Transparent (Sclerotic) dentin
Sclerotic dentin can be seen as physiological change (elderly dentin) or pathological change (caries, attrition, deep fillings, ) in primary or secondary dentin.
Partial or complete obliteration of the dentin tubules, at first thickining of peritubular dentin, then complete obliteration of the tubules with intertubular d.
Higher mineralized, harder and denser than normal dentin
Appears light in transmitted light and dark in reflected light.

79. Transparent (Sclerotic) dentin
Young dentin
Adult dentin
Sclerotic dentin

80. Transparent (Sclerotic) dentin

81. Dead tracts
Severe stimulation to dentin leads to destruction or disintegration of the odontoblastic process and odontoblasts.
The dentin tubules are empty and filled with air.
Most often in areas of narrow pulp horns due to odontoblastic crowding. In ground section they appear black.
Often surrounds with sclerotic dentin.

82. Dead tracts

83. Dead tracts

84. Dead tracts

85. Vitality and sensitivity of dentin
Vitality of dentin is its ability to react following physiological or pathological stimuli.
Forming secondary or tertiary dentin, feeling pain are signs of being vital.
Several theories have been cited to explain the mechanism involved in dentinal sensitivity & vitality:
The transducer theory,
the conduction theory,
the modulation theory
the Brännström's hydrodynamic theory.

86. The transducer theory
The transducer theory contend that the odontoblast and its process are capable to mediate neural impulse in the same way as nerve cells.
Contra:
But investigations have proved that no pain is experienced in exposed dentin by application of substance known to bare nerve endings.
The measurement of membrane potential of the odontoblasts shows clearly that this potential is very low to contribute in the pain excitation.

87. The transducer theory

88. The conduction theory
The conduction theory (intratubular innervation theory) contend that dentin is richly innervated and those nerves mediate the impulse to the brain.
Some new studies show that predentin and the first layer of circumpulpal dentin (0.2mm) is innervated with nerve fiber from the raschkows plexus.
The fibers run parallel ro the tomes fiber in the dentin tubules.
The density of those fiber is much higher in the coronal dentin than cervical dentin. Root dentin doesn’t include such fibers.

89. The conduction theory

90. The conduction theory
Some authors contend that those fibers end at the DEJ, but can not be seen in histological slides.
Contra:
It is uncapable to explain the higher sensitivity at the cemento-enamel junction than that felt at other areas.

91. The conduction theory

92. The hydrodynamic theory
The “hydrodynamic theory”, developed in the 1960’s is the widely accepted physiopathological theory of Dentin Sensitivity.
Temperature, physical osmotic changes or electrical and chemical stimuli and dehydration are the most pain-inducing stimuli.
According to this theory, those stimuli increase centrifugal fluid flow within the dentinal tubules, giving rise to a pressure change throughout the entire dentine.

93. The hydrodynamic theory
The movement stimulates intradentinal nerve receptors sensitive to pressure (BARORECEPTORS), which leads to the transmission of the stimuli .
This simulation generates pain.

94. The hydrodynamic theory
Berman describes this reaction as:
“The coefficient of thermal expansion of the tubule fluid is about ten times that of the tubule wall.  Therefore, heat applied to dentin will result in expansion of the fluid and cold will result in contraction of the fluid, both creating an excitation of the 'mechano-receptor'.”

95. Vitality and sensitivity of dentin