1. Presentation by:
Garima singh
1st yr PG
Dentin
1

2. • Primary dentin Vs
permanent dentin
• Infected dentin Vs affected
dentin
• Smear layer
• Dentin bonding system
• Conclusion
• References
• Introduction
• Composition of dentin
• Dentinogenesis
• Physical properties of dentin
• Histology of dentin
• Types of dentin
• Innnervation of dentin
• Age and functional changes
Contents :
2

3. • Dentin is a
mineralized, elastic, yellowish-
white, avascular tissue enclosing the
central pulp chamber.
• Dentin is characterized by multiple
closely packed dentinal tubules that
traverse its entire thickness and
contain the cytoplasmic extensions
of odontoblasts that once formed
the dentin and then maintain it.
Introduction
3

4. • Inorganic material 70%
– Consist of hydroxyapatite in form of small plates
• Organic material 20%
– It is about 90% collagen (mainly type I with small amount of
type III and type V)
– noncollagenous matrix proteins and lipids
• Water 10%
Composition of dentin
4

5. • It is a two phase sequence
– collagen matrix formation
– Mineralization
• Outlines are
– Differentiation of odontoblast
– Formation of mantle predentin
– Mineralization
Dentinogenesis
5

6. • Differentiation of odontoblast is brought about by
the expression of signaling molecule and growth
factors in cells of IEE
Odontoblast differentiation
6

7. • The first sign of dentin formation is the
appearance of distinct, large-diameter collagen
fibrils (0.1-0.2 mm in dia) called von Korff’s fibres.
• As odontoblast continue to increases in size, they
also produce smaller collagen type I fibrils that
orient themselves parallel to future DEJ.
• In this way a layer of mantle predentin appears.
Fromation of mentle predentin
7

8. • Throughout dentinogenesis, mineralization is
achieved by continuous deposition of mineral,
initially in the matrix vesicle and then at the
mineralization front.
• Factors :‽
• Proteins are :
– Dentin phosphoprotien (DPP)- key protein
– Osteonectin-inhibitory effect
– Osteopontin- promoter
– Gla protein- seeder / nucleaator
– Chondrointin sulphate-
Mineralization
8

9. • Two pattern:
1) Globular mineralization
Deposiotion of crystals in
several discrete areas of matrix
by heterogenous capture in
collagen.
2) Linear mineralization
When the rate of formation
progresses slow, the
mineralization front appears
more uniform.
Pattern of mineralization
Scanning electron micrograph of
globular dentin
9

10. • Dentin formation begins at the
bell stage of tooth development in
tissue adjacent to concave tip of
the folded inner enamel
epithilium.(it is the site where
cuspal development begins.
• Root dentin forms at a slightly
later stage of development.
• requires the proliferation of
epitilial cells ( hertwig’s epithelial
root sheath) from the cervical loop
of enamel organ around growing
pulp to initiate the differentiation
of root odontoblast.
Pattern of dentin formation
10

11. • Many genes are implicated in dentinogenesis, the
newer ones being
– MAP1B for odontoblast differentiation, and
– PHEX for dentin mineralization
Genetic regulation of dentinogenesis
Kaneko T, Arayatrakoollikit U, Yamanaka Y, Ito T, Okiji T. Immunohistochemical and gene
expression analysis of stem-cell-associated markers in rat dental pulp. Cell and tissue research.
2013 ; 351 (3): 425-432.
11

12. • Color :
Pale yellow in deciduous teeth ,Yellow in permanent
dentition.
Light passes through thin, highly mineralized
enamel and is reflected by underlying dentin.
Thicker or hypomineralized enamel does not permit
light to pass through readily.
• Thickness of dentin:
Range: 3-10mm
Ratio of thickness in primary and permanent teeth is
1:2
Physical properties of
dentin
12

13. • Hardness:
Dentin is softer than enamel but more hard than
bone or cementum.
Hardness of dentin is one fifth (1/5th ) that of
enamel; near the DEJ it is three times greater than
near the pulp.
• The compressive strength of dentin is 217-300
MPa which is much higher than enamel.
13

14. • Modulus of elasticity of dentin is 1.67x 10⁶ PSI.
• Tensile strength of dentin is approx. 40MPa
, which is less than cortical bone and approx one half
(1/2) that of enamel.
14

15. • Extend through entire thickness
of dentin from DEJ to pulp.
• ‘S’-shaped path from the outer
surface of the dentin to the
perimeter of the pulp in coronal
dentin.
• Less pronounced in root dentin
in the cervical third and in
incisal edges and cusps .
• Straight in deciduous teeth.
Histology of dentin
Dentinal tubule:
15

16. • Diameter of dentinal tubules :
– Larger in diameter near pulp - 3 to 4µm, and
smaller at the DEJ- 1µm.
• Number of Dentinal tubules :
– At the pulpal surface of dentin the number /sq mm
varies between 50,000 & 90,000.
– At DEJ : 8000- 15,000
• More tubules per unit area in the crown than in the
root.
16

17. • The dentin that immediately surrounds the dentinal
tubules is termed peritubular dentin.
• This dentin forms the walls of the tubules.
• It is highly mineralized (about 9% more) than
intertubular dentin.
– The formation of
intratubular dentin is a
slow continuing process
causing reduction in size
of lumen.
Peritubular dentin/ intratubular dentin:
17

18. • The main body of dentin is
composed of intertubular
dentin.
• It is located between the
dental tubules more
specifically, between the
zones of peritubular
dentin.
• About one half of its
volume is organic
matrix, specifically
collagen fibers which are
randomly oriented around
the dentinal tubules.
Inter-tubular dentin:
18

19. • It is term used to describe areas
of unmineralized or hypo
mineralized dentin where
globular zones of mineralization
(calcospherites) have failed to
fuse into a homogenous mass
within mature dentin.
• These areas are prevelent
especially in person which has
had a deficiency in vit D or
exposure to high level of fluoride
at the time of dentin formation.
Inter globular dentin:
19

20. • When root dentin is viewed under
transmitted light in ground
section , a granular- appearing
area, the granular layer of Tomes,
can be seen just below the surface
of the dentin where the root is
covered by cementum.
• Caused by a coalescing and
looping of the terminal branches
of the dentinal tubules. These
areas remain unmineralized.
Granular layer of TOMES:
20

21. • Incremental lines of von Ebner appear as fine lines or
striationsion.
• A that reflect rhythmic dentin deposition are more
distinctly visualized in this demineralized section.
• B is devoid of such lines. This is a characteristic of
mantle dentin.
• C that reflects the spherule-
like mineralization pattern of
dentin.
Incremental/Imbrication Lines of von
Ebner
21

22. Dentinoenamel junction:
• Unique bond between two very
dissimilar materials.
• It is scalloped or pitted or wavy
in outline, with the crest of the
waves penetrating towards the
enamel.
• Function- prevention of
delamination.
Dentinal junction
Shimizu D, Macho A. functional significance of microstructral detail of the primate dentino-
enamel junction: A possible example of exaptation. J Hum Evol. 2007;52 :103-111.
22

23. Dentino-cemental
junction:
• There is a smooth line junction
between the dentin and
cementum in permanent teeth.
• The cemento-dentinal junction
in deciduous teeth is
sometimes scalloped.
23

24. • In human teeth three types of dentin can be
recognized–
– Primary dentin
– Secondary dentin
– Tertiary dentin
Types of dentin
24

25. Primary Dentin-
• Formed prior to the eruption of the teeth and root
completion.
• Major bulk of dentin.
• It is composed of Mantle dentin and Circumpulpal
dentin.
• Completed 2-3 years after tooth eruption for
permanent teeth and 18 months for deciduous teeth.
25

26. Mantle Dentin-
• The first-formed dentin in the crown underlying the
DEJ.
• Large collagen fibrils perpendicular to DEJ (0.1-
0.2µm in diameter) : argyrophilic or silver-stained
and called von Korffs fibers.
• 4% less mineralized than circumpulpal dentin.
Circumpulpal Dentin-
• Forms bulk of the tooth.
• Formed prior to root completion.
• Smaller collagen fibrils (0.05µm in diameter); more
closely packed together.
26

27. Secondary dentin-
• Formed after completion of root formation.
• Continuing, but much slower deposition of dentin.
• Narrow band of dentin bordering the pulp.
• Contains fewer tubules than primary dentin.
27

28. • Greater deposition of secondary dentin on the roof
and floor of the pulp chamber leads to an asymmetric
reduction in size and shape of the chamber and the
pulp horns.
• The tubules of secondary dentin undergo sclerosis
more readily than primary dentin.
• This process tends to reduce the overall permeability
of the dentin and thereby to protect the pulp.
28

29. Tertiary dentin-
• Tertiary dentin is also known as Reactive,
Reparative or Irregular secondary dentin.
• It is the dentin that is formed in response to
abnormal stimuli such as attrition, abrasion,
erosion, trauma, moderate dentinal caries and
restorative materials.
29

30. • Usually appears as a localized dentin deposit on the
wall of the pulp cavity immediately subjacent to the
area on the tooth that has received the injury (dentin
deposits underneath the affected tubules).
• Types of tertiary dentin:
Reactionary dentin
Reparative dentin
30

31. Reactionary dentin:
• When the original odontoblasts that made secondary
dentin are responsible for focal tertiary dentin
formation.
• Rate of formation of dentin is increased.
• Tubules remain continuous with the secondary
dentin.
31

32. Reparative dentin:
• If the provoking stimulus causes destruction of the
original odontoblasts, the newly differentiated
odontoblast -like cells secrete less tubular, more
irregular dentin called Reparative dentin.
• Here, tubules are usually not continuous with those
of secondary dentin.
32

33. • Nerve fibers were shown to accompany 30-70%
odontoblastic process, and these are reffered to as
intratubular nerves.
• Nerve and their terminal are found in close
association with odontoblast process withih
tubules
• It is believed that most of these are terminal
processes of mylinated nere fibers of dental pulp.
Innervation of dentin:
33

34. • 3 basic theories of pain conduction through
dentin are:
• Direct neural stimulation: by which the nerve in
dentin get stimulated.
• Transduction theory: which presumes that the
odontoblast process is primary structure excited
by the stimulus and that impulse is transmittes to
the nerve endings in inner dentin.
Theories of pain transmission
through dentin
34

35. • Hydrodynamic theory: various
stimuli affect fluid movement in
dentinal tubule.
• This fluid movement , either
inward/ outward stimulates pain
mechanism in tubules by
mechanical distribution of nerves
closely associated with the
odontoblast and its process.
• Thus these endings may act as
mechanoreceptors as they are
affeced by mechanical
displacement of tubular fluid.
•
35

36. • Dead tracts and blind tract:
• When dentin is damaged,
odontoblastic processes die or
retract leaving empty dentinal
tubules. These areas with empty
dentinal tubules are called dead
tracts.
• With time these tracts can
become completely filled with
mineral. This region is called
blind tracts.
Age and functional changes:
36

37. • Longitudinal ground section of
permanent teeth dentin showed
DT following an ‚S‛-shaped
curve, where as in primary DT
follow a straight curve.
• Density of innervation is less in
primary teeth as compare to the
permanent teeth.
Primary dentin and permanent
dentin
Chowdhary N ,Subba Reddy VV. Dentin comparison in primary and permanent molars under transmitted
and polarised light microscopy: An in vitro study. J Indian Soc Pedod Prev Dent. 2010; vol 28(3) : 167-172
37

38. • Primary tooth showing incremental lines at an
angle to the dentinal tubules, whereas permanent
tooth showing incremental lines at right angles to
the dentinal tubules
38

39. • Infected dentin: Superficial layer which is
soft and leathery in consistency and dark
brown in color.
– It has a high concentration of bacteria and
collagen is irreversibly denatured .
– It is not remineralizable and must be removed
• Affected dentin: Deeper layer which is
hard in consistency and light brown in
color.
– It does not contain bacteria and is reversibly
denatured. Therefore this layer preserved
Infected dentin & affected dentin
39

40. • Whenever dentin has been cut or abraded, a thin
altered layer is created on the surface.
• Composed of denatured collagen, hydroxyapatite
and other cutting debris.
• Serves as a bandage over the cut dentinal surface
because it occludes many of dentinal tubules with
debris called smear plugs.
• Clinical significance :
Smear layer
40

41. • The fundamental principle of adhesion to tooth
substrate is based upon an exchange process by
which inorganic tooth material is exchanged for
synthetic resin.
• This process involves 2 phases
1. Etching of tooth surface,
2. Hybridization phase
• Clinical relevance of etching time on dentin
demineralization:
Dentin bonding system
41
Perdigấo J, Lopes M. The effect of etching time on dentin demineralization.
Quintessence int.2001 ; 32:19-26.

42. 42
Clinical implications:
• Dental caries
• Dentin hypersentivity
• Dentinogenesis imperfecta
• Dentin dysplasia

43. • Dentin is a living tissue. It is covered by enamel in
crown portion and by cementum in root portion.
• It will become sensitive if covering of either
enamel or cementum will lost due to any reason.
• So, all efforts should be made during restorative
procedures to preserve as much healthy dentinal
tissue as possible.
Conclusion
43

44. • Chowdhary N ,Subba Reddy VV. Dentin comparison in primary
and permanent molars under transmitted and polarised light
microscopy: An in vitro study. J Indian Soc Pedod Prev Dent. 2010;
vol 28(3) : 167-172
• Kaneko T, Arayatrakoollikit U, Yamanaka Y, Ito T, Okiji T.
Immunohistochemical and gene expression analysis of stem-cell-
associated markers in rat dental pulp. Cell and tissue research.
2013 ; 351 (3): 425-432.
• Shimizu D, Macho A. functional significance of microstructral
detail of the primate dentino-enamel junction: A possible example
of exaptation. J Hum Evol. 2007;52 :103-111.
• http://docbds.blogspot.in/2012/05/removing-of-any-remaining-
infected.html
References
44

45. • Gallagher R, Balooch M, Balooch G, Wilson R, Marshall S,
Marshall G. Coupled nanomechanical and Raman
microspectroscopic investigation od human third molar
dentinoenamel junction. J Dent Biomech. 2010;1:1-4.
• Perdigấo J, Lopes M. The effect of etching time on dentin
demineralization. Quintessence int.2001 ; 32:19-26.
• Nanci A. Tencate’s Oral histology. 8th ed. 2013
• Kumar GS. Orban’s oral histology and embryology. 12th ed. India:
Elsevier, 2009
45

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