Dentin is the hard, bone-like tissue found in teeth beneath the enamel and cementum. It contains dentinal tubules that hold odontoblastic processes and nerves. Dentin is classified as primary, secondary, or tertiary depending on the stage of development. Primary dentin forms before and during eruption, secondary dentin develops after root formation is complete, and tertiary dentin is deposited in response to stimuli like attrition or dental procedures. Dentin has a high mineral content but is softer than enamel. It provides strength and resilience to teeth during chewing.

1. Dentin
Dr. Muznah Sultan
Lecturer DIDC, DUHS

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

6. Odontoblastic process

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

9. Dr.Syed Sadatullah
Types of Dentin

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.

11. Dr.Syed Sadatullah
Secondary and Tertiary Dentin

12. Dr.Syed Sadatullah
Types of Dentin
Predentin
Mantle Dentin
Circumpulpal Dentin
Inter-globular Dentin
Sclerotic Dentin
Intra-tubular Dentin
Inter-tubular Dentin
Tomes Granular layer

13. Dr.Syed Sadatullah
Odontoblast process in dentin tubule

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
Dr.Syed Sadatullah

15. Dr.Syed Sadatullah
Mantle Dentin – Inter-globular Dentin – Circumpulpal Dentin

16. Inter-globular Dentin
Dentine separating the mantle dentin and circumpulpal
dentin is hypo-mineralized and is called inter-globular
dentin
Interglobular Dentin
Dr.Syed Sadatullah

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
Dr.Syed Sadatullah

18. Dr.Syed Sadatullah
Intra-tubular Dentin

19. Inter-tubular Dentin
The dentinal matrix that lies between the intra-tubular
dentin is inter-tubular dentin
Dr.Syed Sadatullah
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
Dr.Syed Sadatullah

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
Dr.Syed Sadatullah

22. Dr.Syed Sadatullah
Incremental lines

23. Dr.Syed Sadatullah
Incremental lines

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
Dr.Syed Sadatullah

25. Dr.Syed Sadatullah
Lines of Owen
Neonatal Line in Enamel and Dentin

26. Thank You!!
Dr.Syed Sadatullah Ibn Sina National Medical College