Dentin along with Dentinogenesis

1. DENTINDENTIN
Dr.MaDhusuDhaN rEDDy

3. ToothTooth
Dentin
Tooth Crown
Tooth Root
Pulp

4. DentinDentinPulpPulp

5. DentinDentin
PulpPulp
Odontoblast cell layer

6. Dentin
Pulp

7.  Provides the bulk and general form of tooth.
 Determines the shape of the crown.
 Physically & chemically the dentin closely
resembles the bone.
 The main morphologic difference between bone &
dentin is that some of the osteoblasts that form
bone marrow enclosed within its matrix substance
as osteocytes, whereas the dentin contains only the
processes of the cells that form it.
 Both are considered vital tissue because they
contain because they contain living protoplasm.
DENTINDENTIN

9. • It is light yellowish in color, becoming darker with
age.
• It is elastic and subject to slight deformation.
• Harder than bone but softer than enamel.
• Lower content of mineral salts in dentin renders it
more radiolucent than enamel.

10.  Consists of 35% organic matter and water & 65%
inorganic material.
 The organic substance consists of collagenous
fibrils and a ground substance of
mucopolysaccharides (proteoglycans and glycos
aminoglycans).
 The inorganic component consists of
hydroxyapetite as in bone, cementum & enamel.
 Organic constituents can be removed from the
mineral by incineration or organic chelation.

11. • The bodies of the odontoblasts are arranged in a
layer on the pulpal surface of the dentin, and only
their cytoplasmic processes are included in the
tubules in the mineralized matrix.

12. •Each cell gives rise to one process, which traverses
the predentin & calcified dentin within one tubule.

13. •Terminates in a branching network at the junction
with enamel or cementum.
•Tubules are found throughout normal dentin & are
therefore characteristic of it.

14. • The course follows a gentle curve in the crown, less
so in the root, where it resembles S in shape.

15. • Starting at right angles from the pulpal surface,
the first convexity of this doubly curved course is
directed toward the apex of the tooth.
• Near the root tip & along the incisal edges and
cusps the tubules are almost straight.

16. •These tubules end perpendicular to the
dentinoenamel and dentinocementum junctions.

17. • The ratio between the outer and inner surfaces of
dentin is about 5:1.
• The ratio between the numbers of tubules per unit
area on the pulpal and outer surfaces of dentin is
about 4:1.

18. • There are more tubules per unit area in the crown than in
the root.
• The dentinal tubules have lateral branches throughout
dentin, which are termed canaliculi or microtubules.
• A few dentinal tubules extend through the dentinoenamel
junction into the enamel. These are termed enamel
spindles.

20. Types of DentinTypes of Dentin
Dentin
Primary physiologic
dentin
Secondary physiologic
dentin
Tertiary dentin or
reparative dentin or
reactionary dentin or
irregular secondary dentin
Mantle
dentin
Circumpulpal
dentin
Peritubular
dentin
Intertubular
dentin

21.  The dentin that immediately surrounds the dentinal
tubules.
 It is more highly mineralized than intertubular
dentin.
 It is twice as thick in outer dentin (approx. 0.75um)
than in inner dentin (0.4um).
 By its growth, it constricts the dentinal tubules to a
diameter of 1um near the dentinoenamel junction.
 Organic matrix is lost along with mineral after
decalcification.
 The calcified tubule wall has an inner organic lining
termed the lamina limitans, high in
glucosaminoglycans (GAG).

23. • Forms the main body of dentin.
• It is located between the dentinal tubules or, more
specifically, between the zones of peritubular
dentin.
• Its organic matrix is retained after decalcification.
• About one-half of its volume is organic matrix,
specifically collagen fibers. The fibrils range from
0.5 to 0.2um in diameter and exhibit crossbanding
at 64um intervals, which is typical for collagen.

25. Dentinal tubules
Peritubular dentin Intertubular dentin

26. Dentinal tubules
Peritubular dentin Intertubular dentin

27.  Is located adjacent to the pulp tissue.
 Is 2 to 6 um wide, depending on the activity of the
odontoblast.
 It is the first formed dentin and is not mineralized.
 As the collagen fibers undergo mineralization at the
predentin- dentin front, the predentin then becomes dentin
and a new layer of predentin forms circumpulpally.

28.  They are the cytoplasmic extensions of the
odontoblasts.
 The odontoblasts reside in the peripheral pulp at
the pulp- predentin border and their processes
extend into the dentinal tubules.
 The processes are largest in diameter near the
pulp and taper further into dentin.
 The odontoblast cell bodies are approximately
7um in diameter and 40um in length.

29. Odontoblasts and processOdontoblasts and process
Odontoblast cellsOdontoblast process
Dentin Pulp

30. Relationship
Between
Odontoblastic
Process And
Dentinal Tubule

31. • Mantle dentin is the first formed dentin in the
crown underlying the dentinoenamel junction.
• It is the outer or most peripheral part of the
primary dentin & is about 20um thick.
• The fibrils found in this zone are perpendicular to
the dentinoenamel junction.
• Circumpulpal dentin forms the remaining primary
dentin or bulk of the tooth.
• Represents all of the dentin formed prior to root
completion.
• The fibrils are much smaller in diameter & are
more closely packed together.
• Slightly more mineral content than mantle dentin.

33.  A narrow band of dentin bordering the pulp and
representing the dentin formed after root
completion.
 Contains fewer tubules than primary dentin.
 There is usually a bend in the tubules where
primary and secondary dentin interface.

35.  The incremental lines of von ebner, or imbrication
lines, appear as fine lines or striations in dentin.
 They run at right angles to the dentinal tubules.
 These lines reflect the daily rhythmic, recurrent
deposition of dentin matrix as well as hesitation in
the daily formative process.
 The course of the lines indicates the growth
pattern of the dentin.
 Some of the incremental lines are accentuated
because of disturbances in the matrix and
mineralization process. Such lines are known as
contour lines of owen.

39.  These lines represent hypocalcified bands.
 In the deciduous teeth and in the first permanent
molars, the prenatal and postnatal dentin is
separated by an accentuated contour line. This is
termed the neonatal line.
 This line reflects the abrupt change in environment
that occurs at birth.
 The dentin matrix formed prior to birth is usually
of better quality than that formed after birth.

41. • Sometimes mineralization of dentin begins in
small globular areas that fail to fuse into a
homogenous mass. This results in zones of
hypomineralization between the globules. These
zones are called interglobular dentin.
• Forms in crowns of teeth in the circumpulpal
dentin just below the mantle dentin.
• Follows an incremental pattern.
• The dentinal tubules pass uninterruptedly, thus
demonstrating a defect of mineralization & not of
matrix formation.

44.  There is a zone adjacent to the cementum that
appears granular. This is known as ‘Tomes
granular layer’.
 Slightly increases in amount from the
cementoenamel junction to the root apex.
 Caused by coalescing and looping of the terminal
portions of the dentinal tubules.

47. Odontoblasts differentiation Early dentin formation

48. 1- Differentiation of odontoblasts.
Differentiate from
the peripheral dental
papilla cells (UMC)
At first become short
columnar cell with
many stubby
processes
Preameloblasts
Basement
membrane
The cells grow in length (40u)
and closely packed together
Ameloblasts

49. Odontoblasts differentiation

51. Odontoblast become a protein forming and secreting cell.
 R E R , Mitochondria and Golgi bodies
 Ribonucleic acid and alkaline phosphatase
Inner epithelium
side
Large open faced
Nucleus
R E R
Mitochondria
Golgi bodies Predentin

52. At first more than one process
As more Dentin is laid down, the
cells recede and leave single process
( Tomes’ fiber)

53. The odontoblasts decrease in size and form dentin in a slowly diminishing
rate until stimulated to form reparative dentin.

54. Dr.Madhusudhan reddy 09/08/17 54

55. 1 Matrix formation
(Predentin)
Collagen Ground
fibers substance
2 Mineralization
Hydroxyapatite
crystals

57.  A- Mantle dentin
 The first formed dentin
layer in crown
 And root
Fibers are perpendicular to D EJ
Fibers are parallel to
basement membrane

58. 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

59. 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
Crown Root

60. Budding of
matrix vesicles Rupture of matrix
vesicles
Mineralization of the
mantle dentin
Has
membrane
rich in
alkaline
phosphatase
Calcium and
phosphate ions
undergo
crystallization
Matrix
vesicle

61. M V in
matrix
Crystal
lization
Lodgment
of crystals
Rupture
1- Linear at the
mantle dentin area
2- Globular in
circumpulpal dentin
just below mantle
dentin
3- Combination in
the remaining
circumpulpal
dentin of the crown
and root

62. 1-Regular secondary dentin
(Mild stimulus)
 Occurs on the entire pulpal
surface. In multirooted teeth
it is thicker on the roof and
floor of pulp chamber.
 The size of the pulp cavity
decrease and obliteration of
the pulp horns
 The dentinal tubules change
their direction to a more wavy
course
 The number of dentinal
tubules are fewer
 Line of demarcation (dark).

63.  Severe stimulus
 The dentin is formed at a
localized area.
 The dentinal tubules are less
in number and irregular in
arrangement.
 UMC from the
subodontoblastic layer will
differentiate and replace the
degenerated odontoblasts to
form reparative dentin
Irregular D T

64. Atubular dentin ( area
without dentinal tubules)
Osteodentin (entrapped cells).
Vasodentin
(entrapped b.v.)

65.  Regular
 Cause:
Mild stimuli (slow attrition
and slowly progressing
caries)
Site of formation:
Occurs on the entire pulpal
surface of the tooth ( thicker
on the roof and floor of the
pulp chamber in multirooted
teeth).
Dentinal tubules:
- Change their direction and
have more wavy course
- They decrease in number per
unit area.
Line of demarcation
Present and stained dark.
 Irregular
Severe stimulus (abrasion,
erosion, severe attrition and
deep caries)
Formed at the area
corresponding to the pulpal
end of the exposed dentin.
- Have irregular or twisted
course
- They decrease in number
and some areas may have no
tubules
(a tubular dentin).
May or may not present

66.  Clinically:
 The decrease of the
pulp chamber height
and obliteration of the
pulp horns make the
liability of pulp
exposure during cavity
preparation much less
likely to occur
 The localized area of
dentin formation
increase the time
taken by caries to
reach the pulp
(barrier)

67. Mild stimulus leads to changes in
the dentin already present.
1- Odontoblast and
its process undergo
fatty degeneration.
2- Then there will be
calcification of dentinal
tubules. First become
narrow by widening of
the peritubular dentin. 3- Then the DT become
obliterated.
The affected area have occluded dentinal tubules, so the dentin
have uniform refractive index. So this area of dentin appear
translucent by transmitted light.

68. Trasparent D

69.  Severe stimulation to
dentin leads to destruction
of the odontoblastic
process and odontoblasts.
This leads to embty and
wide dentinal tubules.
 These areas apear black
with transmitted light.
 Under the dead tracts from
the pulpal surface ,
reparative dentine will be
formed.
 The dead tract serounded
by sclerotic dentin.

70. • Direct conduction theory in which stimuli directly
effect the nerve endings in the tubules.
• Transduction theory in which the membrane of
the odontoblast process conducts an impulse to
the nerve endings in the predentin, odontoblast
zone, and pulp.
• Fluid or hydrodynamic theory in which stimuli
cause an inward or outward movement of fluid in
the tubule, which in turn produces movement of
the odontoblast and its processes.

72. • The rapid penetration & spread of caries in the dentin is
the result of the tubule system in the dentin.
• The dentinal tubules form a passage for invading
bacteria that may thus reach the pulp through a thick
dentinal layer.
• Air driven cutting instruments cause dislodgement of
the odontoblasts from the periphery of the pulp & their
aspiration within the dentinal tubule.
• Sensitivity of dentin.

73. • Infected dentine is the outer layer and is softened
and contaminated with bacteria. It is irreversibly
denatured and not remineralized
• Affected dentine has a demineralized phase, but
not yet invaded by bacteria. It can be
remineralized.
• In clinical restorative treatment of dentine during
cavity preparation it is infected dentine which is
completely removed. The affected dentine, which
may be remineralized after the completion of
restorative treatment, is not removed and is
preserved.

74. Thank you