Histology of dentin

Histology of Dentin

2. ©Copyright 2007, Thomas G. Hollinger, Gainesville, Fl
By Hesham Dameer

3. A vascular
Forms the bulk of each tooth crown & root .
 Cellular (contains odontoblast processes )
some capacity for repair by deposition on its
pulpal surface .
Histology of Dentin

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

5. Primary dentin the most prominent dentin in the tooth,
lies between the enamel and the pulp chamber.
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.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.

6. Tertiary dentin is a dentin that formed as a reaction to
external insult such as caries. The dentin is formed
from a pre-existing odontoblast.

Tertiary dentin formation 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.

7. Tertiary dentin

8. Circumpulpal dentin: The layer of dentin around the outer
pulpal wall.

Peritubular dentin: Dentin that creates the wall of the
dentinal tubules.
Intertubular dentin: Located between the dentinal tubules

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 .

9. peritubular / intratubular dentine
dentin that forms the wall of each tubule
more mineral than intertubular dentin
intertubular dentine
dentine between the tubules

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

11. Dentin
Cementum
Granular layer
of Tomes

12. 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.

13. 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 creation 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 .

14. Odontoblast
processes

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

16. Dentinal MatrixDentinal Matrix
Dentinal matrix
Hole for dentinal tubules

17. 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 .

18. Dentinal tubules

19. Dentinal tubules
Peritubular dentin Intertubular dentin

20. Dentinal TubulesDentinal Tubules
Coronal dentin
Root dentin

21. Brannstrom’s Theory.
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.

22. THE END
Thank
you