2. 1. Introduction and Chemical
Composition
Dentin is a hard bone-like tissue that is
present in the crown as well as in the
root of teeth.
In the crown, dentin is covered by
enamel and in the root it is covered by
cementum.
Unlike enamel, dentin is a vital tissue
containing the cell processes of
odontoblasts and neuron.
Mature dentin has 20% organic, 70%
inorganic and 10% water by weight .
3. The organic matrix of dentin is collagenous
It provides resiliency to the crown which is
necessary to withstand the forces of
mastication
The principle inorganic component of
dentin is hydroxyapatite crystals
The high mineral content of dentin
makes it harder than bone and
cementum but softer than enamel
4. 2. Dentinal structure and
classification
Dentin is packed with dentinal tubules that
traverse its entire thickness
Dentinal tubules contain odontoblastic
process and nerve fibres
The odontoblastic processes have numerous
side branches that exist in the lateral
branches of the dentinal tubules
5. Odontoblasts – peri-tubular and inter-tubular
dentin has been removed
Dentine tubules – odontoblastic
processes removed
7. 3. Histological Features of Dentin
Depending on its time of development Dentin is classified as:
Primary dentin
Secondary dentin
Tertiary dentin
8. Primary dentin
Primary dentin is the developmental dentin that is formed
before and during eruption
Secondary dentin
Secondary dentine develops after the root formation has
been completed
Deposition of secondary dentin is continuous but much
slower
10. Tertiary dentin
Tertiary dentin is produced in reaction to stimulus, such as
attrition , caries or restorative dental procedure
Tertiary dentin can be reactionary or reparative
Reactionary dentin is that type of tertiary dentin that is
deposited by the pre-existing odontoblasts
Reparative dentin is deposited by newly differentiated
odontoblasts. Irregular dentin formed in response to an
irritant.
14. Predentin
Predentin is the first deposited layer of un-mineralized
matrix of dentin
Mantle Dentin
The outer layer of dentine that mineralizes first is called
mantle dentin. It lies near the DEJ
Circumpulpal Dentin
The bulk of dentin underlying the mantle dentin is called
circumpulpal
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16. Inter-globular Dentin
Dentine separating the mantle dentin and circumpulpal
dentin is hypo-mineralized and is called inter-globular
dentin
Interglobular Dentin
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17. Intra-tubular Dentin
Dentin surrounding and nearest to each tubule is hyper-mineralized
and is called intra-tubular dentin or peri-tubular
dentin
If there is increased mineralization of intra-tubular
dentine the tubule gets occluded and the resulting dentine
is called sclerotic dentin or transparent dentin
If odontoblasts die as a result of injury or old age the
tubule are referred to as dead tracts
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19. Inter-tubular Dentin
The dentinal matrix that lies between the intra-tubular
dentin is inter-tubular dentin
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Inter-tubular Dentin
20. Tomes granular layer
In the roots near the cemento-dentinal junction there are
hypo-mineralized areas of dentin around the dentinal
tubule called the Tomes granular layer
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21. 4. Histological Features of Dentin
Incremental growth line
The organic matrix of dentine is deposited incrementally at a daily
rate of 4μm
At the boundary of each daily increment, minute changes in
collagen fibre orientation is observed which manifest as
incremental lines
Incremental lines run perpendicular to the dentinal tubules
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24. Incremental lines of von Ebner
In ground section the 5-day increment can be seen as
incremental or imbrications' lines of von Ebner
Counter lines Owen
Counter lines of Owen represent normal physiological
alterations in the pattern of mineralization
Neonatal line represents an exaggerated counter line of
Owen.
Neonatal lines are seen in all primary teeth and the first
permanent molars
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