This document discusses the structure and properties of dentin. It is composed of 70% hydroxyapatite crystals, 20% collagen, and 10% water. Dentin is lighter yellow in young individuals and darker with age. It is approximately 3-3.5mm thick on coronal surfaces and increases with secondary and tertiary dentin formation. Dentin is one-fifth the hardness of enamel and its hardness increases with age. It contains dentinal tubules that originate from odontoblasts and provide pathways for stimulation of the dental pulp. There are three types of dentin - primary, secondary, and tertiary - which differ in their location, rate of formation, orientation of tubules, and permeability.

1. REPUBLIC OF YEMEN
UNIVERSITY OF ADEN
FACULTY OF DENTISTRY
CONSERVATIVE DEPARTMENT
DONE BY:
Nehal Fathi Hanif (A-30)
Nasima Ahmed Habtoor (A-23)
Marwa Abdullah Bin Shehna (A-12)
Islam Abubaker Aidros (A-26)
Maryam Aidros Abdullah (A-25)
Ahmed Mohammed Abdul Rahman (A-31)

2.  It’s a calcified C.T that form the
main bulk of tooth.
 It’s a vital structure. It consist of
cells (odontoblast) and a calcified
intercellular substance.
 The odontoblast are not present
inside dentin body (like in bone),
but dentin cell present in surface
of dentin in it’s pulpal surface.
 While dentin itself contain
cytoplasmic process of
odontoblast called odontoblastic
process

3. - 70% inorganic hydroxyapatite
crystals.
- 20% the organic components
primarily of collagen type one.
- 10% water.

4. Inorganic material 70%
composition
Organic material 20% Water 10%

5. - Light yellowish in young
individuals while it becomes
darker with age.

6. THICKNESS
- Is around 3 - 3.5 mm on the
coronal surface.
- The thickness of secondary
and tertiary dentin increases.

8. - Is one-fifth that of enamel.
- DEJ is 3 times more than that near
the pulp.
- Hardness of dentin also increases
with advancing age due to
mineralization.
- The flexibility of dentin provides
support or cushion to the brittle
enamel.

9. 1/5th of
enamel
hardness
Compressive
hardness is 266
Mpa
Hardness
increases with age
Tensite
strength 40-60
Mpa

10. - Provide strength to the tooth.
- Offers protection of pulp.
- Provides flexibility to the tooth.
- Affects the color of enamel.
- Defensive in action (initiating pulpal
defence mechanism.

11. DENTINAL TUBULES
- Are fine tubules that
surrounding the
odontoblastic
process.
- They are straight in
root , cusps and
incisal edges.
- In the rest of tooth
forms (S) shape.

13. - PULP : is 2 - 3 μm
- The numbers : 45.000 – 65.000 /mm²
- DEJ : is 0.5 - 0.9 μm
- The numbers : 15.000 - 20.000 /mm²

14. - It’s a layer of unmineralized dentin matrix
of variable (10-30 μm).
- It’s consist of Collagen, Glycoprotein and
proteoglycan.
- It’s similar to a bone layer and stainless
than mineralized dentine.
-This layer has protection function.

15. - It forms the wall of D.T and highly
mineralized than rest of dentin by 40%

16. - It’s form the main body of dentin.
- Determine the elasticity of dental
matrix.
- Consist of large collagen fibers.

18. PRIMARY DENTIN

23. III. Tertiary dentin:
 Other names are reparative , reactive or irregular secondary
dentin
 Localized area of dentin formed opposite to reaction to
stimulus as, trauma, caries, attrition, abrasion and restorative
procedures.
 Formed by odontoblast cell directly affected by stimulus but
if the odontoblast are severed or dead it will replaced by
underlying U.M.C
 Histologically, D.T are few in number, irregular arrangement
(twisted)
 Dentin formation can be rapid as odontoblast are included in
reparative dentin (osteodentin) or not contain D.T. as in
atrubular Dentin.
 It separated from other dentin types by deeply stain line.

25. Caused :by a mild stimulus as slowly progressing
caries, mild attrition or abrasion or as normal age
change.

26. Mechanism: mild stimulus will lead to mild injury
which lead to fatty degeneration and calcification
of entire D.T in affected area or in old aged dentin
due to continued deposition of calcium ions which
lead to complete closure of D.T this will prevent
stimulus from extend toward pulp make pulp less
sensitive.

27. Histologically: in G.S appear as transparent in
transmitted light and black under reflected light.
Both dead tract and sclerotic dentin are age
change occur in primary dentin.

29. - Caused by sever stimuli as rapid progressing
caries. Where is no time to form reparative
dentin. Or in area of narrow pulp horn due to
crowding of odontoblast.

30. - Odontoblastic process and
cell undergo total destruction & D.T
appear empty filled with air, so
appear black under transmitted light
and light in reflected light.

31. - As odontoblast cell die UMC form odontoblast
like cell and neibhouring cell deposited
reparative dentin at pulpal end to seal and
close the opened D.T

33.  Care should be taken during tooth preparation, and
should be done under constant air water spry to avoid
the heat formation that will damage dental pulp.
 The dentin should be protected by liner or bases or
bonding agents. There is a layer on enamel of dentin
for bonding of restorative materials to tooth structure
called smear layer, it’s made up of small particles of
mineralized collagen matrix , this layer should be
remove and that done by etching, that cause removal
of smear layer and etching of intertubular and
peritubular dentin for micromechanical bonding.
 The restorative should be well adapted to prepared
walls to prevent microleakage and damage underlying
dentin/pulp.

34. Primary Secondary Tertiary
Definition
Form before root
complete
Form after root
complete
Form as response to
stimuli such caries,
trauma
Cells type
Usually primary
odontoblasts
Primary odontoblasts
Secondary
odontoplasts
Or undifferentiated
mesenchymal cells of
pulp
Location In all area of dentin
Not uniform and found
over root and floor of
pulp
In area that external
stimulus
Orientation of
tubules
Regular Irregular Atubular
Rate of
formation
Rapid Slow
Rapid between 1.5μm
to 3.5μm / day
depending on the
stimuli
Permeability More Less least