This is about Dentin , BDS 1st year by SDM DENTAL COLLEGE DHARWAD

1. Dentin

3. Introduction
 Forms bulk and general form of the tooth
 Determines the shape of the crown,
◦ Cusps and ridges
◦ Number and size of roots
 Living tissue - contains within its tubules the
processes of the odontoblasts & branches of
nerves
 Physically and chemically, the dentin resembles
a bone.

4. Physical Properties
Color : Young individuals is light yellow color
darker with age.
Hardness:
• Dentin is visco elastic.
• Harder than bone but considerably softer than
Enamel
• Dentin hardness varies tooth types and
between crown and root dentin.
• Dentin is somewhat harder in its central part
than near pulp or on its periphery.

5. Thickness:
 3-10mm or more
 The buccal surfaces has maximum thickness,
followed by lingual. Thinner in proximal
surfaces
 Ratio between outer & inner dentin surfaces
=5:1

6. Chemical Properties
 35%- organic matter and water
 65%- inorganic material.
 Organic substance
◦ Collagenous fibrils embedded in the ground
substance of mucopolysaccharides
(proteoglycans and glycoproteins)
• Type I collagen is the principal type of
collagen found in the dentin.

7.  Proteoglycans:
1. Chondroitin sulphates
2. Decorin
3. Biglycan
 Glycoproteins:
1. Dentin sialoprotein (DSP)
2. Osteonectin
3. Osteopontin

8.  Phosphoprotein:
1. Dentin phosphoprotein (DPP)
2. Corboxyglucomate containing protein
(Gla-protein)
 Phospholipids
 Growth factors: TGF , FGF, IGFs and
BMPs
The protein of dentin matrix and bone is
similar but dentin sialoprotein and dentin
phosphoprotein are present only in
dentin.
ᵞ-

9. Inorganic components:
 Hydroxyapatite crystals – 3Ca3(PO4)2.
Ca(OH)2
 Crystals are plate shaped and much smaller
than the hydroxyapatite crystals in the
enamel.
 Dentin also contains small amounts of
phosphates, carbonates and sulphates
 The crystals are poor in calcium but rich in
carbon when compared to enamel.

10. ENAMEL DENTIN
HYDROXYAPATITE

11. Structure
 Dentinal tubules
 odontoblasts bodies are arranged in a layer at
the pulpal surface of dentin and one process
in one tubule
 Odontoblastic process traverses the
predentin, calcified dentin and terminates in a
branching network at the junction with
enamel or cementum.

12. Dentinal tubules
 Gentle curve in the crown
 Less so in the root, where it resembles a
gentle ‘S’ (sigmoid course) in shape.
 First convexity of this doubly curved course
is directed toward the apex of the tooth.
 These curvatures are called primary
curvatures.

14.  Tubules end perpendicular to the DEJ.
 Branches of the dentinal tubules near the
terminals are referred to as terminal branches.
 Tubules exhibit minute relatively regular
secondary curvatures that are sinusoidal in
shape.
 The dentinal tubules have lateral branches
throughout dentin which are termed as
canaliculi or microtubules (1microns)

16. Legend: A, Odontoblastic process; B, Lateral branches
of dentinal tubules

17.  D. tubules are larger diameter near pulp (3-
4 micron) than outer surface (1microns)
 Tubules are farther apart in periphery &
closely packed near pulp.
 Ratio between the number of tubules per
unit area on pulpal to surface is 4:1

18. Contents of dentinal tubules:
• Odontoblastic process
• Afferent nerve terminals
• Antigen presenting cell’s – Process
• Periodontoblastic space – Dentinal fluid

21. Odontoblastic process
 Cytoplasmic extension – odontoblasts
 Synonym – “Tomes fiber” or “Filopodia”
 Size
◦ Near pulp – 3 to 4 µm
◦ Near enamel – 1 µm
 Process occupies the center of the tubules

22.  The odontoblast cell bodies are 7µm in dia &
40µm in length.
 Odontoblstic process is composed of
microtubules of 20µm in dia. & small filaments
5 to 7.5µm in dia.
 The microtubules & intermediate filaments run
longitudinally throughout the tubules.
 Occasionally mitochondria, dense bodies
resembling lysosomes, microvesicles & coated
visicles may open to extracellular space also seen

24. Extension of odontoblastic
process:
 3 theories:
◦ Process grows in length as dentin thickens-
E. spindles
◦ Process – predetermined length then
retracts
◦ Process – Degrade at terminal end

26. Periodontoblastic space:
 Periodontoblastic space is reported to be
present between odontoblastic process and
peritubular dentin. This space contains the
dentinal fluid.
 The normal flow of fluid is outwards from
the pulp.
 The dentinal fluid has a higher potassium
than sodium.
 Dentinal fluid – Responsible for dentin
sensitivity

28. Types of dentin:
 Based on structure
 Based on origin
 Based on Mineralisation
◦ Low – Predentin
◦ Moderate – Intertubular
◦ High – Peritubular

29. Peritubular dentin:
 Surrounds the dentinal tubules and termed
the peritubular dentin.
 More highly mineralized than the dentin
present between the tubules.(intertubular
dentin).
 Peritubular dentin differs from intertubular
dentin by its matrix composition

30.  Dentin that immediately surrounds the
d.tubules – forms the wall of d. tubules
 Since the deposition of minerals occurs in
inner wall of tubules rather than outer wall-
“intratubular dentin” better word
 More mineralized (9%) than intertubular dentin
 Thick in outer dentin(0.75µm) than in the inner
dentin(0.4µm). Constricts the dentinal tubules
to a diameter of 1µm near the dentinoenamel
junction.

31. • Calcified tubule inner wall has Organic lining
termed the “lamina limitans” or “sheath of
neumann” made of organic material – GAG’s
or it is a Plasma membrane of odontoblasts

33. Intertubular dentin
 Main body of dentin
 Located between the dentinal tubules or
zones of peritubular dentin
 Organic matrix - collagen fibres which are
randomly oriented around the dentinal
tubules
 Fibrils are 0.5-0.2 µm in dia. Exhibit cross
banding at 64 µm.
 Hydroxypatite crystals which average 0.1µm
in length along the fibres with their long axes
oriented parallel to the collagen fibres.

34. Predentin
 Located adjacent to the pulp tissue. 2 to 6µm
wide
 Not mineralised.
 Pale staining than the mineralized dentin
owing to differences in the composition of
the matrix.
 Undergo mineralization & predentin becomes
dentin & a new layer of predentin forms
circumpulpally

36. 36
Legend: A, Odontoblasts; B, Predentin; C,
Calcification front; D, Calcified dentin

37. Legend: A,
Odontoblasts; B,
Predentin; C, Pulp
cavity; D, Dentinal
tubules

38. Primary Dentin
 Dentin formed before root completion
 Two types
◦ Mantle – outer most
◦ Circumpulpal - bulk of primary

39. Legend: A,
Primary curve of
dentinal tubule;
B, DEJ; C,
Mantle dentin; D,
Circumpulpal
dentin

40. Primary – “Mantle dentin”
 First formed dentin in the crown
underlying the dentinoenamel junction-
20µm thick
 Softer and thus provides cushioning effect
to the tooth.
 Organic- Fibrils formed in this zone are
perpendicular to the dentinoenamel
junction.
 Larger collagen fibrils argyrophilic (silver
stained) – von korff ‘s (type III collagen)

41. Vs circumpulpal dentin
 Collagen fibers perpendicular
 Mantle dentin is less mineralised.
 Fewer defects than circumpulpal dentin.
 Matrix vesicles are involved in the
mineralization of mantle dentin.

42.  Circumpulpal dentin forms the remaining
primary dentin or the bulk of the tooth.
 Collagen fibrils in the circumpulpal dentin are
much smaller in diameter (0.05µm).
 Crystals closely packed together, slightly
more mineralized than mantle dentin
Primary – “Circumpulpal dentin”

43. Mantle dentin
Circumpulpal dentin