The document discusses the formation and types of dentin. It begins by explaining that dentinogenesis is initiated by odontoblasts and forms the bulk of each tooth crown and root. There are several types of dentin that form at different stages: mantle dentin forms first along the enamel layer, primary dentin makes up most of the tooth, and secondary and tertiary dentins are deposited throughout life. Tertiary dentin specifically forms in response to stimuli like decay. Dentin contains tubules that house odontoblast processes and provide sensitivity; it is made up of both organic and inorganic components including collagen and hydroxyapatite.

1. By Hesham Dameer
Dr. Hesham Dameer

2. Dentinogenesis is the formation of dentin, begins
prior to the formation of enamel and is initiated by
the odontoblasts of the pulp. Dentinogenesis is
performed by odontoblasts and it begins at the late
bell stage of a developing tooth. Unlike enamel,
dentin continues to form throughout life and can be
initiated in response to stimuli, such as tooth decay
or attrition. The different stages of dentin formation
result in different types of dentin:
Mantle dentin,
Primary dentin,
Secondary dentin, and
Tertiary dentin.
By Hesham Dameer

3. 1. Formation of predentin :
The fully differentiated odontoblasts which
differentiate from cells of the dental papilla begins
secreting an organic matrix around the area directly
adjacent to the inner enamel epithelium, closest to
the area of the future cusp of a tooth. The organic
matrix contains collagen fibers with large diameters
(0.1-0.2 μm) in diameter) , these bundles are known
as Korff's fibers that form the major component of the
first formed thickness of dentin . The first formed
thickness of dentin is the mantle dentin and is a layer
usually about 5-30 μm thick .
By Hesham Dameer

4. As dentin is further deposited, the Korff's
fibers fade gradually and a smaller fibrils
constitute a network in the dentin subsequent
to the mantle dentin. The odontoblasts begin
to move toward the center of the tooth, leaving
an extension called the odontoblast process.
Thus, odontoblasts function is :
a. Formation of both the collagen fibers
and the acid mucopolysaccharides of
the dentin matrix .
b. Secretion of hydroxyapatite crystals
and mineralization of the matrix.

6. Odontoblasts secrete
vesicles containing
Ca2+ and PO4- which
induce hydroxyapatite
crystal formation
By Hesham Dameer

8. ©Copyright 2007, Thomas G. Hollinger, Gainesville, Fl
Odontoblasts
Predentin
Dentin
By Hesham Dameer

9. Dentin
Odontoblast processes

10. 2. Maturation of predentin : it occurs at a rate that
parallels matrix formation, and both formation and
maturation of predentin begin at the tip of the crown and
proceed in a rhythmic pattern to gradually complete
cervically . The first formed predentin begins its
mineralization in a globular pattern, where a small
centers of calcification spread concentrically until they
fuse with each other to form homogenously calcified
dentin .
When these globules do not fuse with each other , areas
of unclassified dentin are left and known interglobular
dentin. The dentin then calcified in a linear pattern or
occasionally by globular pattern .
Mineralization sequence of predentin appears primary by
crystal deposition in the form of fine plates of hydroxy-
apatite on the surface of the collagen fibrils and the
ground substance .
By Hesham Dameer

11. Inter-
globuler
dentin

12. Mineralized dentin
Mineralization frontOdontoblasts
Predentin
Dentin is mineralized after it is formed. This begins in small spherical
areas which become larger and fuse with one another to form a
mineralization front.

13.  A vascular
 Forms the bulk of each tooth crown & root .
 Cellular (contains odontoblast processes )
 some capacity for repair by deposition on
its pulpal surface .
By Hesham Dameer

14.  harder than bone & cementum
 softer than enamel
 →less resistant to attrition
occlusal and incisal attrition
 →less resistant to abrasion
Hard toothbrush & other abrasion
 →less resistant to acid attack
caries erosion

15. 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
Intergl
obular
dentin
Granular
layer of
tome's

16. There are many types of dentin, as follow :
Primary dentin the most prominent dentin in the
tooth, lies between the enamel and the pulp
chamber. Primary dentin include :
 Mantle dentin
The outer layer closest to enamel is known as
mantle dentin.
 Circumpulpal dentin : represent all dentin formed
before complete root formation .
By Hesham Dameer

17. Secondary dentin is formed after root formation
is complete, normally after the tooth has erupted
and is functional. It grows much slower than
primary dentin, but maintains its incremental
aspect of growth. It has a similar structure to
primary dentin, although its deposition is not
always even around the pulp chamber. the
growth of this type of dentin causes the
decrease in the size of the pulp chamber with
age; this is why cavity preparation in young
patients is risky which may lead to exposing the
pulp.

18. Tertiary dentin
Tertiary dentin is a dentin that formed as a reaction to external
insult such as caries. It is of two types, either reactionary ,
where dentin is formed from a pre-existing odontoblast or is it
reparative, where newly differentiated odontoblast-like cells
from a pulpal progenitor cell are formed due to the death of
the original odontoblasts . Tertiary dentin is only formed by an
odontoblast directly affected by stimulus, therefore the
architecture and structure depends on the intensity and
duration of the stimulus e.g. if the stimulus is a carious lesion,
there would be extensive destruction of dentin and damage to
the pulp, due to the differentiation of bacterial metabolites
and toxins. Thus tertiary dentin is deposited rapidly, with a
sparse and irregular tubular pattern and some cellular
inclusions known as osteodentin. However if the stimulus is
less active, it would be laid down less rapidly with a more
regular tubular pattern with absent of any cellular inclusions.
By Hesham Dameer

19. Tertiary dentin
Tertiary dentin formation (arrows) is
regarded as an important defense
mechanism of the pulp-dentin
complex in response to either
pathological or physiological
insults. The presence of tertiary
dentin reduces dentin permeability.
By Hesham Dameer

20. Circumpulpal dentin: the layer of dentin around the outer pulpal wall.
Peritubular dentin :
dentin that creates the wall of the dentinal tubules.
› tubules are delimited by a collar of more highly calcified matrix =
peritubular dentin
› about 40% more mineralized than dentin
Intertubular dentin :
› located between the dentinal tubules
› represents the primary secretory product of the ODs
› consists of tightly interwoven fibers + apatite crystals
Interglobular dentin :
› areas of unmineralized or hypomineralized dentin
› where globular areas of mineralization have failed to fuse .
Granular layer of tome's :
The superficial layer of dentin , adjacent to cementum, shows minute black
spaces in the ground sections These are only found in the root dentin . It is
believed to be due to :
- Interference with the mineralization of the firstly formed layer of dentin .
- They may represent smaller areas of interglobular dentin than that found
in the crown .
- Looping of the terminal ends of the tubules .

21. peritubular / intratubular dentine
dentin that forms the wall of each tubule
more mineral than intertubular dentin
intertubular dentine
dentine between the tubules
By Hesham Dameer

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

23. Dentin
Cementum
Granular layer
of Tomes
By Hesham Dameer

24. Incremental lines of Von Ebner :
 They are fine lines ,that in cross section, run at right
angles to dentinal tubules . These lines correspond to
the growth pattern of dentin, and the distance
between these lines is matching with the daily rate of
deposition of dentin .
 Some incremental lines are more pronounced than the
others, they represent disturbance in mineralization
( hypocalcification) and are known lines of Owen . In
decidous teeth and first permanent molar an
incremental line is present which represent
hypocalcified dentin, known neonatal line . This line
separates between prenatal dentin formed before
birth and post natal dentin formed after birth.

25. By Hesham Dameer
The growth pattern of dentin

26.  It consists of 35% organic material and 65%
inorganic material .
 The organic material consists of collagen fibrils
and ground substance( mucopoly saccharides )
 The inorganic component consists of hydroxy
apatite crystals composed of several
thousands of unit cells . The crystals are plate
shaped and smaller than the plates of
enamel.
By Hesham Dameer

27.  Odontoblasts: An odontoblast is a biological cell of neural crest
origin that is part of the outer surface of the dental pulp, and whose
biological function is dentinogenesis, which is the formation of dentin .
 Odontoblasts are large columnar cells arranged in a well defined
layer , sending their odontoblastic process through dentin .
 It is rich in endoplasmic reticulum and Golgi apparatus, especially
during primary dentin formation, to give it a high secretory capacity
(firstly collagenous matrix to form predentine, then mineral to form
the complete dentine). Its nucleus is aligned away from the dentine,
with its Golgi and ER above it (towards the dentine) reflecting its
unidirectional secretion.
 Each odontoblast sends one odontoblastic process that run inside
the dentinal tubule, where both traverse the dentin thickness .
A long its course the process sends out several lateral branches
enclosed in the canaliculi .

28. Odontoblast
processes

29.  The functions of the odontoblast process are as follows:
 1. To aid in the secretion of tubular dentin (dentin surrounding
tubule) which further organizes and strengthens the dentine
as a whole tissue
 2. General maintenance of the dentinal tubule and dentinal
fluid (ion/protein content etc.)
 3. To secrete sclerotic dentin upon carious attack to block off
dentinal tubules, slowing the progress of the attack (air space
above blockage is known as a dead tract)
 4. To channel signals of attack to the odontoblast cell body,
initiating reactionary dentin secretion
 5. To channel hydrokinetic forces of water movement to the A
delta fiber wrapped around its base, maintaining
dentine sensitivity
By Hesham Dameer

31. Odontoblast cellsOdontoblast process
Dentin Pulp

32. Dentinal matrix
Hole for dentinal tubules

33. Dentinal tubules
 Dentinal tubules are structures that span the entire
thickness of dentin and form as a result of the
mechanism of dentin formation. From the outer
surface of the dentin to the area nearest the pulp,
these tubules follow an S-shaped path. The diameter
and density of the tubules are greatest near the pulp.
Tapering from the inner to the outermost surface, they
have a diameter of 2.5 μm near the pulp, 1.2 μm in the
middle of the dentin, and 0.9 μm at the dentino-
enamel junction. Within the tubules, there is an
odontoblast process .
By Hesham Dameer

34. Dentinal tubules

35. Dentinal tubules
Peritubular dentin Intertubular dentin

36. Dentinal TubulesDentinal Tubules
Coronal dentin
Root dentin
By Hesham Dameer

37. Dentin Sensitivity:Dentin Sensitivity:
Three theoriesThree theories
1) Nerve in dentin ( intratubular innervations
theory) – the dentin tubules contains nerve
endings that respond when it is stimulated .
2) Odontoblasts and their process serves as
receptors and are coupled to nerves in the pulp.
3) Hydrodynamic theory : Fluid movements in the
dentinal tubules – the tubular nature of dentin
permits fluid movement to occur within the tubule
when a stimulus is applied – a movement
registered by pulpal free nerve endings close to
the dentin.
Dr.Dameer

38. Brannstrom’s Theory.

39. Dr.Dameer

40. Dr. Hesham
Dameer