Dentin

1. Dentin
Dr. Syed Sadatullah
Assistant Professor

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 .
Dr.Syed Sadatullah

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
The knoop hardness for dentin is approximately 68
Dr.Syed Sadatullah

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

Dr.Syed Sadatullah

5. Dr.Syed Sadatullah
Odontoblasts – peri-tubular and inter-
tubular dentin has been removed
Dentine tubules – odontoblastic
processes removed

6. Dr.Syed Sadatullah
Odontoblastic process

7. 3. Histological Features of Dentin
Depending on its time of development Dentin is classified
as:
Primary dentin
Secondary dentin
Tertiary dentin
Dr.Syed Sadatullah

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
It has a tubular structure which is almost continuous
with the primary dentin
Dr.Syed Sadatullah

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
Dr.Syed Sadatullah

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
Neonatal Line in Enamel and Dentin
Lines of Owen