1. Tissue of the teeth
Dr Jamal Naim
PhD in Orthodontics
Dentin

2. Compositions of dentin
organic substance
30-25% from its weight
About 90% collagen fibers
About 10% ground substance
inorganic substance
70-75% from its weight
Hydroxyapatite crystallites

3. Properties of dentin Yellowish in color Elastic
Less hard than enamel, but more than cementum
Less radio-opaque than enamel, but more than cementum
3-10 mm thick

4. Life cycle of odontoblasts
There are only 3 stages in the life cycle of odontoblasts:
Differentiating stage
Formation stage
Quiescent stage

5. Cross section (A)
Neural crest cells

7. Basement membrane
ECTODERM
MESODERM
ectomesenchymal cells

9. Bud stage
Future dental papilla

10. cap stage
Future dental papilla

11. Life cycle of odontoblasts
Differentiating stage:
Before Differentiation the inner dental epithelium is separated from the dental papilla by the thin basement membrane.
The undifferentiated peripheral cells are spindle and separated by great amount of ground substance
In the early bell stage, under the inductive influence of the inner dental epithelium, the peripheral ectomesenchymal cells differentiate into preodontoblasts.

12. Life cycle of odontoblasts
Differentiating stage
Basement membrane
preodontoblast
Undifferentiated cell

13. Late Bell stage/differentiating stage for odontoblasts

14. Life cycle of odontoblasts
They assume to a columnar shape and aligned as a single row along the basement membrane.
Several projections arise from the upper part of the cells.
The nuclei become basally oriented.
The cells grow in length to become columnar (40u)
Now the fully differentiated odontoblasts begin their work.

15. Life cycle of odontoblasts
Formative stage:
Concentration of the cell organelles, granular components and globular elements
Production of the first amount of dentin (dentin matrix)
The odontoblasts retreat from the basement membrane
Leaving a single process which become enclosed in the dentinal tubule (tomes fiber).
With successive deposition of dentin, tubule and process grow in length.

16. Life cycle of odontoblasts
Differentiating stage/
Begin of formative stage
predentin
odontoblast
Undifferentiated cell

17. Mitochondrion
RER
Formative stage
Nucleus
predentin
Formative stage

18. Formative stage

19. Life cycle of odontoblasts
Quiescent stage:
Actively secreting odontoblasts decrease slightly in size.
The odontoblastic process stop to elongate
In this stage the odontoblasts produce only secondary dentin.

20. Life cycle of odontoblasts
Quiescent stage:
Odontoblasts decrease in size and function
The dentin formation is reduced
They produce now secondary and reparative dentin

22. Dentinogenesis Matrix Formation (forming predentin) Maturation
Collagen fibers
Ground substance
Maturation
(mineralization)
Hydroxyapatite crystallites

23. Dentinogenesis Formation of predentin (dentin matrix):
The first indication of forming predentin is the development of the KORFF FIBERS.
They are bundles of fibrils among the odontoblasts
They are perpendicular to the basement membrane and attached to it.
This layer is main part of the MANTLE DENTIN

24. Basement membrane MANTLE DENTIN TOMES FIBER
fibers are perpendicular to the basement membrane
TOMES FIBER

25. Dentinogenesis
The korffs fibers fade gradually and smaller fibrils form a network in the dentin subsequent to the mantle dentin, the CIRCUMPULPAL DENTIN.
The odontoblasts form the main components of the dentin matrix, the collagen fibers and the mucopolysaccharides.

26. Basement membrane MANTLE DENTIN CIRCUMPULPAL DENTIN TOMES FIBER
fibers are parallel to the DEJ
TOMES FIBER

28. Dentinogenesis Maturation of predentin:
It occurs parallel to matrix formation
It begins at the tip of the crown
It proceeds in a rhythmic pattern to gradually complete cervically.
The first layer of predentin begins its maturation in a globular pattern (matrix vesicle), where small centers of calcification spread concentrically until they fuse together.
If somewhere those globules do not fuse together, areas of uncalcified dentin are known as interglobular dentin.

29. Dentinogenesis
The maturation goes then in linear or occasionally globular pattern.
The mineralization begins by crystal deposition in form of fine plates of hydroxyapatite on the surface of the collagen fibrils.
The long axes of the crystals are paralleling to the fibrils.

30. Maturation of dentin MANTLE DENTIN CIRCUMPULPAL DENTIN Mineralized MD
Matrix vesicle
Rupture of the MV and begin of mineralization
Maturation of dentin

31. Maturation of dentin Matrix vesicle
Begin of Crystallization
Matrix vesicle
Crystal lodgment
Rupture of the MV and begin of mineralization
Maturation of dentin