Dentin is the mineralized tissue that forms most of the tooth. It is softer than enamel but harder than bone and cementum. Dentin consists of mineralized collagen and closely packed dentinal tubules that contain odontoblastic processes. Dentin is formed by odontoblasts, which deposit an organic matrix that then mineralizes. There are different types of dentin formed at various stages, including primary, secondary, and tertiary dentin formed in response to stimuli. The properties and microstructure of dentin can provide information in forensic dentistry applications.

1. DENTIN

2. Introduction
• Dentin is the mineralised tissue
that forms the bulk of the tooth
• It is present in the crown and in
the root portion of the tooth.
• It is covered by enamel in the
crown portion and cementum in
the root portion.
• It consists of mineralized
collagen matrix consisting of
closely packed dentinal tubules
which extends the entire
thickness of the dentin.

3. Physical
properties of
dentin
• Dentin is pale yellow contributes the color of
the tooth
• Dentin is harder than the bone and cementum
but softer than the enamel.
• Even though the dentin is rigid ,it is an elastic in
nature ,which permits slight deformation.
• The tubular structure of dentin makes it
permeable ;this permeability , however
decreases with increasing age.

4. Chemical
properties of
dentin
• 70% of inorganic material and 20% of
organic material and 10% water
• Inorganic portion –calcium hydroxy apetite
crystal
• Organic portion – collagen fibres mainly type
I collagen.
• Ground substance- non collagenous matrix
protein.

5. Histology of dentin
1. DENTINAL TUBULES
Odontoblast forms the dentin
matrix and move towards the
pulp.
shape of dentinal
tubules

6. • The thickness of dentin ranges from 3 to 10 mm.
• Buccal and lingual surfaces are bigger than the mesial and
distal surfaces.
• The tubules are closely packed towards pulp and widely
packed dentinoenamel junction.
• Dentinal tubules contains terminal branches and lateral
branches

7. Lateral and
terminal
branches of
dentinal
tubules

8. Predentin
• Predentin is the newly laid ,yet
to be mineralized dentin matrix.
• It is the innermost layer of the
dentin clos to the pulp.
• Width is 6 to 10micrometer.
• It becomes a part of mineralized
dentin when it starts undergoing
mineralization.

9. Peritubular dentin
• The dentin that present immediately
next to the dentinal tubules is the
peritubular dentin.
• The minerals are deposited in the
inner wall of tubule for the formation
of peritubular dentin so it is called as
INTRATUBULAR DENTIN.
• The thickness of peritubular dentin is
0.75micrometer in outer dentin and
0.4micrometer.
• The thick organic matter rich in
glycosaminoglycans called lamina
lamitants is seen in peri tubular dentin

10. Intertubular
dentin
• The dentin situated between the dentinal tubules is the intertubular
dentin which forms the major bulk of the dentin
• It is made up of type I collagen fibres.

11. Odontoblastic
process
• Odontoblastic process are the
cytoplasmic extensions of the
odontoblast which extend into
the dentinal tubules
• The process has a diameter of 3-
4 micrometer when it enters the
dentinal tubules and tapers to
1micrometer as it extends
further into the tubule.

12. Odontoblastic process

13. Primary dentin
• MANTLE DENTIN
Mantle dentin is a first formed dentin in
the crown.
It is less mineralised
It is composed of larger collagen fibre
It shows branching of dentinal tubules.

14. Circumpulpal
dentin
• Circumpulpal dentin constitutes
the remaining primary dentin
• When compared to mantle
dentin , circumpulpal dentin is
more mineralised and has
collagen fibres

15. Interglobular dentin
• During the mineralisation of dentin matrix the
minerals are deposited as globules
• In most areas these globules fuse to form a
uniformly calcified tissue .
• When some of the globules fails to fuse into a
homogenous mass hypomineralised area will form,
called as interglobular dentin.

16. Age and functional changes
• Secondary dentin
• Transluscent dentin
• Tertiary dentin
• Sclerotic dentin
• Dead tracts

17. Secondary Dentin
• Dentin formed after root completion
• Borders the pulp
• Formed by continuous , slow deposition of
dentin by odontoblasts
• Fewer dentinal tubules
• Function : Continuous deposition leads to
smaller pulp chamber and narrow root
canals in old patients
• Protects the pulp from exposure

18. Translucent dentin
• As a result of physiologic ageing, dentinal
tubules become completely occluded with
apatite crystals
• Common in the root
• Same refractive index as intertubular dentin
• Occluded dentinal tubules appear translucent
in ground section
• Formation starts apically, proceeds cervically
with age.
• Function: Used in Forensic dentistry for age
estimation

19. Tertiary dentin
• Dentin formed in response to various stimuli like attrition, caries or
restorative dental procedure
• Types
• Reactionary dentin
• Reparative dentin/Osteodentin

20. Reactionary dentin
• Formed by existing odontoblasts
which have survived severe
damage cause to them by
stimulus.
• Irregular appearance with fewer
tubules

21. Reparative dentin
• Formed by newly differentiated
odontoblast-like cells that replace
the original odontoblasts that
have been destroyed by stimulus
• Newly differentiated odontoblast
like cells arise from deeper regions
of the pulp
• Irregular with fewer , more
twisted tubules
• Newly differentiated odontoblast
like cells get entrapped in the
matrix they form to produce
osteodentin.

22. Possible origin of newly differentiated
odontoblast like cells
• Dormant odontoblast cells formed as a result of epithelial-
mesenchymal interaction during tooth development
• Odontoblast like cells that arise from stem cell population,without
epithelial-mesenchymal interaction, under the influence of cytokines
and growth factors

23. Sclerotic dentin
• Filling up of dentinal tubules with calcified
material in response to caries, attrition, erosion
• Defensive reaction
• Keeps the pulp vital for a longer time
• Fine meshwork of apatite crystals
• Transparent
• Appears light in transmitted light and dark in
reflected light.
• Mineral concentration is higher, crystal size is
smaller
• Harder

24. Dead tracts
• Empty dentinal tubules due to
retraction of odontoblastic
process or death of odontoblast.
• Occurs as a result of caries,
attrition, erosion
• In ground sections, appear dark
in transmitted light and white in
reflected light
• Commonly seen in narrow pulp
horns
• Common in older teeth

25. DENTIN SENSITIVITY
• DIRECT NEURAL STIMULATION THEORY
• FLUID OR HYDRODYNAMIC THEORY
• TRANSDUCTION THEORY

26. DENTINOGENESIS
• Dentin formation begins when the tooth germs has reached the
bell stage of development.