2. Structure and Functions of the Dentin-Pulp Complex
Husain Keylani
R1 endo board

3. The transition to pulp occurs with the initiation of dentin formation.
Dentin-pulp complex ?
Embryologically, histologically and functionally; dentin and pulp should be considered the same. This entity is exemplified by the classic functions of the pulp.
The transition to pulp occurs with the initiation of dentin formation.

4. The pulp
The pulp incompressible, the total volume within the pulp chamber cannot be greatly increased.
Thus Inflammatory reaction results in an increase in pulp tissue pressure instead of volume.
(Heyeraas et al,1992)

5. Development
The Primary oral cavity or stomodeum (lined with ectoderm )is a depression between the brain and the pericardium in an embryo,
It is separated from the upper end of the foregut by (bucco-pharyngeal membrane ,27 days)
Mid-brain
bucco-pharyngeal
membrane
stomodeum
pericardium

6. Development
Most of the C.T. cells underlying the oral ectoderm are neural crest cells or ectomesenchyme in origin

7. Development
Neural crest travel down the sides of the head into the maxilla and mandible to form the tooth germ

8. Development
During sixth week ,tooth formation begin as localized proliferation of ectoderm to form two horseshoe-shaped structures called primary epithelial band or primary dental laminae which split into
vestibular & dental lamina
Oral vestibule Dental organ
&

9. Stage of development
Formation of the teeth is a continuous process has been divided in to three stages :
bud stage
Cap stage
bell stage

10. Cont. 1-The bud stage: the initial stage , dental lamina proliferate
to the adjacent ectomesenchyme

11. Cont. 2- Cap stage : the dental lamina cont. proliferate- aconcavity.
The outer cells
cuboidal and constitute the outer enamel epithelium .
The inner cells
elongated and represented the inner enamel epithelium .
Between them is network of cells termed
(the stellate reticulum)

12. Cont.
3-bell stage (18):
The last period of growth is also known as histodifferentiation
In the cervical loop where the outer and the inner enamel epithelia are joined continue to proliferate .
The tooth development enters the bell stage
During (BV) become established in the dental papilla

13. A tooth germ consists of 3 parts:
form
Origin
tooth germ
enamel
ectoderm
A-Enamel organ
dentin and pulp.
ectomesenchyme
B- Dental papilla
cementum, PDL, and alveolar bone.
C-dental sac =tooth follicle

14. Cell differentiation mechanisms
Embryonic development of any tissue is prompted by interaction with an adjacent tissue.
Complex epithelial and mesenchymal interactions occur which direct the ameloblasts and odontoblasts diff. by changes in gene expression.

15. Cont.
Epithelial- ectomesenchymal inductive interaction during normal odontogenesis lead to:
1- Cytodifferentiation of dentin and enamel forming
cells.
2-dental hard tissue formation

16. Mechanisms of interaction
A: cell-to-cell interaction
1-Direct cell-to-cell contact.
2-The transmission of molecules synthesized and secreted by one cell and then captured by surface receptors of another cells.
CAMs(cell adhesion molecule )mediate morphogenesis. through contrall cell proliferation
Cell contian membrane protein called (integrin)receptor for CAMs.
integrin
CAMs

17. Cont… B:Cell-to-ECM interaction.
Carry by substrate adhesion molecule (SAMs) the best study of the ECM are fibronectins.
G.factors are polypeptides produced by cells that initiate proliferation, migration and diff. of a variety of cells.

18. Cont… Dental basement membrane:
It exists between IDE(inner dental epithelium and the underneath dental mesenchyme
It consist of (thin basal lamina & layer of ECM)

19. Cont… Dental basement membrane:
It exists between IDE(inner dental epithelium and the underneath dental mesenchyme
It consist of (thin basal lamina & layer of ECM)
BL is compsed of type IV collagen (as areceptors) which has binding sites for other BM consituents.
(like laminin ,fibrinoctin ,proteoglycan)
Laminin is the CAM in the basement membrane

20. Cont…
Odontoblast cell surface proteoglycans act as receptors for matrix molecules .signals from matrix components influence migration and diff. of odontoblasts.

21. Differentiation of Odontoblasts
occurs during the bell stage.
Preameloblasts diff. at a faster rate than odontoblasts, but dentin matrix is formed before enamel matrix.
There is still mitotic activity among the relatively immature cells of the inner enamel epithelium., mitotic activity ceases and the cells elongate.

22. Cont.Differentiation of Odontoblasts
With the onset of differentiation a single layer of cell(preodontoblasts) align themselves along the basement membrane separating the inner enamel epithelium from the dental papilla.
IEE PO BM DP

23. Cont.Differentiation of Odontoblasts
These cells stop dividing and elongate into short columnar cells with basally situated nuclei
Several cytoplasmic projections from each of these cells extend toward the basal lamina.

24. Cont.Differentiation of Odontoblasts
As the odontoblasts continue to differentiate, they become progressively more elongated
And cytoplasmic processes from these cells extend through the BM toward the basal lamina, and more and more collagen fibrils appear within the ECM.

25. Cont.Differentiation of Odontoblasts
More odontoblastic diff elongation with characteristic of protein-secreting cells more collagen fibrils appear in the ECM and more defined large odontoblastic process toward BL.

26. Cont.Differentiation of Odontoblasts
The odontoblasts reach full maturity and become tall columnar cells
Production of the initial dentin matrix involves the formation, organization, and maturation of collagen fibrils and proteoglycans.
As more collagen fibrils accumulate subjacent to the basal lamina,(The lamina becomes discontinuous and eventually disappears. )

27. Cont.Differentiation of Odontoblasts
The odontoblasts reach full maturity and become tall columnar cells
Production of the initial dentin matrix involves the formation, organization, and maturation of collagen fibrils and proteoglycans.
As more collagen fibrils accumulate subjacent to the basal lamina,(The lamina becomes discontinuous and eventually disappears. )
Some of Odon. processes extend toward the ameloblasts
Some of these become interposed between the processes of ameloblasts, resulting in the formation of enamel spindles

28. Cont.Differentiation of Odontoblasts
At the onset of dentinogenesis the dental papilla becomes the dental pulp
As predentin matrix is formed, the odontoblasts commence to move toward the central pulp, depositing matrix.
Within this matrix a process from each odontoblast becomes accentuated and remains to form the primary odontoblast process.
It is around these processes that the dentinal tubules are formed.

29. Root Develop after completion of enamel formation.
Proliferateion (inner and outer enamel epithelia),
and form a structure known as the Hertwig epithelial root sheath (HERS)
(HERS) determine the size and shape of root of the tooth .

30. Root
The first layer of the dentin matrix mineralizes gap appear in the root sheath allowing mesenchymal cells from the dental sac to move into contact with the newly formed dentine .
These cells then differntiation into cementoblast and deposit cementum matrix on the root dentine.

32. Epithelial Rests of Malassez
Persistant of epithelial cells of the root sheath in the PDL after tooth development.
Some of them retain & under go division
Later produce periapical cyst.
(Trowbridge,1967)

33. Accessory Canals During root formation :
a break develops in the continuity of the sheath , producing a small gap ,dentinogenesis does not take place opposite the defect .
The result is small “accessory “ canal between the dental sac and the pulp .
If periodontal tissue lose their integrity , m/o go pulp

34. Cont.

35. DENTIN Composition of fully mature dentin : INORGANIC MATERIAL WATER
ORGANIC MALTERIAL
WATER
20%
~91%(collagen) I,V.
~9%(non-collagen)
*phosphoproteins
*proteoglycans
*Gla proteins
*acidic glycoproteins
*Gr. Factors+lipids
70%
Hydroxyapatite
10%

36. Types of the dentin
1-Developmental dentin : is forms during tooth developmet &classified as: A-orthodentin: - the tubular form of dentin

37. Cont. Types of the dentin
B-mantle dentin
-is the first formed dentin and is situated immediately
subjacent to the enamel or cementum.
-( 150μm, less mineralized and softer).
(Herr P et al,1986)

38. Cont. Types of the dentin
C-Circumpulpal dentin :
- it constitutes the major part
of developmental dentin.
- oriented at right angles to
the long axis of the dentinal
tubules.
-500nm in diameter

39. Cont. Types of the dentin
2-Secondary dentin:
-Regular dentin which forms phisiologically after the root is fully developed.
A-Primary physiological dentin
B-Secondary physiological dentin

40. Cont. Types of the dentin
3-Tertiary dentin:
-Irregular dentin forms in response to abnormal stimuli
Reparative D filling
Reactionary D irritant

41. Predentin
*Is unmineralized organic matrix of dentin between the odontoblast layer and the mineralized dentin
type I , II collagens.
Noncollagenous elements
(proteoglycans, Phosphophoryn)
growth factors
(Roberts-Clark D,2000)
Dentin
Predentin
Odontoblasts
Pulp cells

42. Mineralization Mineralization A B E C D
Caph.accomu. In vesicle (prd) grow
Rupsure  release mix
 the mix adjoin to form advance crystl  merge to  form small globules 
The globule expand  and fuse with other untill become mineraized
Cont. in growing and increase mineral content. A B E C D
Mineralization

43. Cont.Mineralization Mineralization front Mineralized dentin Predentin
Odontoblasts

44. Dentinal tubules
Dentinal tubules occupy from 1% (superficial dentin) to 30% (deep dentin) of the volume of intact dentin.
(Garberoglio,Brannstrom 1976)
It slightly tapered , wider portion toward the pulp.(no pretubular d)

45. Garberoglio R, Brännström M: 1976.
Number of Tubules (1000/mm2)
Tubule Diameter (μm)
DISTANCE FROM PULP (mm)
MEAN
RANGE
Pulpal wall 45
30-52
2.5 43
22-59
1.9 38
16-47
1.6 35
21-47
1.2 30
12-47
1.1 23
11-36
0.9 20
7-40
0.8 19
10-25
. Mean Number and Diameter per Square Millimeter of Dentinal Tubules at Various Distances from the Pulp in Human Teeth

46. Cont.Dentinal tubules Coronal dentin S shape DEJ- pulp.
b/c (crowding of odontoblasts)
It converge ? the surface of the pulp chamber has a much smaller area than the surface of dentin along the DEJ.
This results in a progressive increase in dentin permeability

47. Cont.Dentinal tubules
Near the DEJ the dentinal tubules ramify into one or more terminal branches.

48. Peritubular and intertubular dentin
Peritubular Dentin: is dentin lining the tubule , whereas that between the tubules is known as intertubular dentin
minir+hard
< collagn
Presumably, precursors of the dentin matrix that is deposited around each odontoblast process are synthesized by the odontoblast, transported in secretory vesicles out into the process, and released by reverse pinocytosis. A corresponding reduction in the diameter of the process occurs with the formation of peritubular dentin.

49. Dentinal Sclerosis
Partial or complete obturation of dentinal tubules. as result of aging or develop in response to stimuli such as attrition or caries
It helps the pulp from irritation

50. Cont.Dentinal Sclerosis
It is either:  Physiologic: acceleration of peritubular dentin formation in the apical third of the root.  Pathologic: Dentinal tubules are blocked by hydroxyapatite and whitlockite crystals (carious dentin, attrited dentin)

51. Cont.Dentinal Sclerosis
If dentin is damaged the odontoblastic processes die leaving empty dentinal tubules which form areas of
dead tracts (A).
Dead tracts become filled with mineral and are called
blind tracts (B).
The dentin of blind tracts is known as
sclerotic dentin.

52. Interglobular Dentin
Refer to organic matrix that remains unmineralized.
This occurs most often in the circumpulpal dentin just below the mantle dentin.
Vit D-resistant rickets, hypophosphatasia
Inter-globuler dentin

53. Dentinal Fluid volume :
1% of superficial dentin , about 22% of the total of deep dentin.

54. Pressure gradient exists between pulp
Cont.Dentinal Fluid
Outward movement of fluid is blocked peripherally by enamel or cementum.
In case of d.tubules exposureoutward movements to the exposed area is in the form of tiny droplets.
(Itthagarum,2000)
Pressure gradient exists between pulp
(14 cm H2O =10.3 mm Hg) and O. cavity that accounts for the slow outward flow of fluid.

55. Dehydrating ?the dentin can accelerate outward
Cont.Dentinal Fluid
Odontoblast
process
Dehydrating ?the dentin
can accelerate outward
Rapid flow stimulates pulpal
nociceptors that innervate DT
=dentin sensitivity= dentinal permeability
(the hydrodynamic mechanism of dentin sensitivity)
Ingress of
irritants
Dentin
Outward
fluid
movement
Predentin
Desmosome
Odontoblast
Dental pulp
(14 cm H2O / 10.3 mm Hg)

56. Dentin permeability
Dentinal tubules are the major channels for fluid diffusion across dentin .
Fluid permeation is proportion to tubule diameter and number
The permeation of the radicular dentin <coronal dentin .
Fogel HM et al,1988
deep cavity vs shallow

57. Cont.Dentin permeability
The functional or physiologic diameter of the tubules is only about 5% to 10% of the anatomic diameter.
bc(od process+collagen fiber )
(Michelich et al,1978)
It is small enough to remove bacteria from dentinal fluid permitting sterile fluid to enter the pulp chamber
(Michelich et al,1980)

58. Cont.Dentin permeability
The smear layer is capable of physically preventing
bacteria from penetrating dentin.
(Michelich et al,1980)
In nonvital teeth  bacterial invasion of dentinal
tubules occurred more rapidly. ( Due to no permeability)
(Nagaoka et al,1995)
But in vital pulps.  increa .permeab +antibodies in dentinal fluid.
(Hahn et al,1997)
Dentin sclerosis beneath a carious lesion reduce the permeation
by obstruction the tubules
(Pashley,1990);(Tagami et al,1992)

59. smear layer The cutting during cavity preparation or root canal theory
Cont.Dentin permeability
by acid etching or EDTA
smear layer
The cutting during cavity preparation or root canal theory
incidence of pulpal inflammation may be increased
increases the permeability of the dentin

60. MECHANICAL PROPERTIES OF ROOT DENTIN
Endodontically treated teeth showed only a 14%
reduction in dentin toughness compared with vital dentin
(Carter et al,1983)
Endodontic therapy was shown not to change the
Vickers hardness of human root dentin.
(Lewinstein et al,1981)

61. MECHANICAL PROPERTIES OF ROOT DENTIN
Much of the increased incidence of tooth fractures of endodontically treated teeth can be attributed to:
1 -The loss of tooth structure access opening
(Howe et al,1990)
2-Physical weakening of roots by post spaces.
(Isidor et al,1996)

62. MECHANICAL PROPERTIES OF ROOT DENTIN
Age,dehydration and fatigue crack growth in dentin:
old pts has a much shorter fatigue
life than dentin from young teeth
-it increase incidence of root fractures
of RCT actually reflect reduction
in the fracture toughness of old dentin.
(Arola D,2004)

63. MECHANICAL PROPERTIES OF ROOT DENTIN
Other factors
Collagenolytic activity and gelatinolytic activity have measured in mineralized dentin powder .
(Pashley et al,2004).
These enzymes may slowly attack the collagenous matrix of dentin, thereby weakening it over many decades.

64. MECHANICAL PROPERTIES OF ROOT DENTIN
Other factors
Mineralized dentin surrounding post spaces that had been under function for more than 10 years , the functional stresses may cause microcracking of dentin
( Ferrari M et al,2004)