stages of dentin development

1. Development of dentin
Dated: 16/06/20

2. Development of tooth
 Ectoderm Ectomesenyhme
 Enamel Dental papilla
Dental Folloicle

3.  Dental papilla Dental follicle
 Dentin Cementum
 Pulp Alveolar bone
Periodontal ligament

5. Dentin
 It is the main bulk of tooth.
 Composition:
Inorganic: 60-65% hydroxyapatite crystals.
Organic: 35-40% collagen and non-collagenous proteins

6. Dentinogenesis
 Ondotoblast differentiation
 Formation of mantle dentin
 Vascular supply
 Control of mineralization
 Pattern of mineralization.
 Root dentin formation
 Secondary and tertiary dentin formation

7. Odontoblast formation
 The cells responsible for the formation of dentin are ondontoblasts.
 Ectomesenchyme of dental papilla under the influence of inner enamel epithelium.
 Signaling molecules and growth factors (Bone morhogenic proteins BMP, Insulin
growth factor Igf, Transforming growth factors tgf).

9. Cells of dental papilla:
Undifferentiated ectomesenchyme cells
small, centrally placed nucleus and a few oraganelles.

10.  Acellular zone:
 Initially dental papilla is separated from the inner enamel epithelium by a zone
which does not have cells but few collagen fibers.

12.  Inner enamel epithelial cells reverse their polarity, the ectomesenchymal cells
adjacent to acellular zone become enlarged in size.
 Number of cell organelles also increased.
 The acellular zone diminished and is filled by the odontoblasts.
 Odontoblast: Columnar shaped cells, polarized.

14. Formation of mantle dentin
 The first step towards the formation of dentin is the secretion of organic matrix.
 Vonkorff,s fibers:
 initially collagen III fibers are laid down.
 large fibers diameter (0.1-0.2um)
 Silver stained
 Along fibronectin
 Fan shaped spread just below the epithelium.

16.  Collagen I is the main secretory product of ondontoblast.
 Ondotoblastic process (tomes’s fiber):
 These cells secrete cytopaspic extensions.
 They have few organelles but have abundant cytoskeleton components.

18.  The ondotoblast secretes number of matrix vesicles.
 These matrix vesicles have collagen I.
 They fuses with each other and give rise to a large globule.
 Then minerals are added in these vesicles.
 thus there is always a layer of un-mineralized dentin just ahead of mineralized
dentin.

19. Pre dentin
 Located adjacent to pulp tissue.
 2-6um depending on the activity of odontoblasts.
 First form dentin and non-mineralized.

22. Vascular supply
 During the mantle dentin formation the capillaries are underneath of odontoblasts.
 Dentinogenesis become rapid during the formation of circumpulpal dentin, these
capillaries migrate among the ondontoblasts.
 For rapid diffusion fenestrations appear among endothelial cells.
 After the completion of primary dentin formation, they retreat to their previous
position.

24. Control of mineralization
 Initiated by the small crystallites with in matrix vesicles budded by the odontoblasts.
 Increased concentration of phosphate combine with calcium to form hydroxyl apatite
crystals.
 Crystals grow and matrix vesicles rupture.
 Fuse with adjacent vesicles and form mineralization matrix.
 Initially deposited on the surface of collagen fibrils and ground substance and later with
in fibrillis.

25.  The minerals are added by three mechanisms
 Leaky junctions between odontoblasts for calcium and phosphate
 L shaped calcium channel
 The presence of alkaline phosphatase and calcium adenotriphosphatase

27. Pattern of minerlization
 Globular pattern:
 the first formed predentin begins its mineralization in a globular pattern, where a
small centers of calcification spread concentrically until they fuse with each other to
form homogenously calcified dentin.

29.  Linear mineralization:
 Mineralization of pre dentin appears primary by crystal deposition in the form of
fine plates of hydroxyapatite on the surface of collagen fibrillis and the ground
substance.
 Circumpulpal dentin have both type of mineralization.

31. Formation of root dentin
 Begins when the formation of enamel and dentin reach at the future
cementoenamel junction.
 The epithelial cell of hertwig’s root sheath initiates the cells of dental papilla to
form odontoblasts for the formation of root dentin.
 The collagen fibrils of root dentin parallel to the cementodentinal junction
 Less mineralized and less number of tubules.

34. Secondary and tertiary dentinogenesis
 Secondary dentin:
 After root formation
 Slower pace
 Tertiary dentin:
 At specific sites due to injury
 Source:
 Ondotoblast at the pulp periphery
 Undiffereniated cells in the pulp

36.  https://youtu.be/B7QZx9Ir9JU