Types of Dentin Incremental Lines Age and functional changes Pain Sensation

3. DENTIN
Menatalla M. Elhindawy

4. Dentin
 Types of Dentin
Incremental Lines
Age and functional changes
Pain Sensation

5. Dentin
Types of Dentin
Primary Secondary Tertiary
A g e

6. Dentin
Types of Dentin
Primary
Mantle Circumpulpal
• Inter-globular
Dentin
• Hopewell
Smith zone
• Granular
layer of
Tome’s

7. Dentin
Types of Dentin “primary”
Mantle
• The 1st formed layer of dentin
• No odontoblastic process
• 5-20 µ
• Contains fewer defects.

8. Dentin
Types of Dentin “primary”
Circumpulpal
Inter-tubular Intra-tubular

9. Dentin
Types of Dentin “primary”
 Inter-tubular
• It forms the main bulk of
dentin
• Located in between the DTs
• Collagen rich dentin
• It consists of randomly
arranged network of type I
collagen fibrils in which the
apatite crystals are deposited.

10. Dentin
Types of Dentin “primary”
 Intra-tubular
• Collar of highly mineralized dentin
immediately surrounds the dentinal tubules
• Peri-tubular as it is first deposited
surrounding the DT then continued its
deposition in side the DT
• Changes the diameter of DTs
• It doesn't exist in the area of interglobular
dentin

11. Dentin
Types of Dentin “primary”

12. Dentin
Types of Dentin “primary”
 Inter-globular Dentin
• It is a mineralization defect found
immediately below mantle dentin
• Only exists in the crown
• It is caused by failure of matrix globules to
fuse into homogenous calcified mass.
• It follows an incremental “decelopmental”
pattern
• Dentinal tubules pass uninterrupted
through it
• Increased with Vit D deficiency

13. Dentin
Types of Dentin “primary”
 Hopewell-smith layer
• Only in the root
• Hyaline layer
• 8-15µ
• May serve to bond
cementum to dentin

14. Dentin
Types of Dentin “primary”
 Granular layer of Tome’s
• Only exists in the root
• Considered as a constant feature
• DTs can’t pass through it
• Recently, it was considered as
looping of the terminal portion of
DTs
• It doesn’t follow an incremental
“developmental” pattern
• Best seen in ground section

15. Dentin
Types of Dentin “secondary”
 Regular 2ry dentin
• Physiologic process that happens
with age but also may be formed
under the influence of mild stimulus
aiming to protect the pulp
• Formed through out life “after
complete root formation”
• Formed at a sower rate with fewer
DTs which change their directions
forming a line of demarcation
between 1ry and 2ry D
• Not evenly formed around the pulp,
but its formation causes pulp
recession.

16. Dentin
Types of Dentin “Tertiary”
 Tertiary dentin
• In response to sever
stimulus
• Localized

17. Dentin
Types of Dentin

18. Dentin
Incremental lines of Dentin
 Incremental lines of von Ebner
 Contour lines of Owen
 Neonatal line

19. Dentin
Incremental lines of Dentin
 Incremental lines of von Ebner
• Daily rhythm
• 4µ day in the crown and lesser in
the root
• Perpendicular on DT in an inward
and root ward direction
 Neonatal line
 Contour lines of Owen
• It is more accentuated incremental
line, resulted from disturbance in
matrix mineralization process.

20. I. Tertiary dentin
II. Dead tract
III.Sclerotic dentin
Dentin
Age & Functional Changes

21. Dentin
Age & Functional Changes
I. Tertiary Dentin
• In response to sever stimulus
• Localized to seal off the injured area.
• Twisted, sparse, lesser DTs
• Also named irregular 2ry dentin
• It may be..
oReactive, when it is formed by
reactivated resting odontoblasts
oReparative, when formed by newly
differentiated odontoblasts

22. Dentin
Age & Functional Changes
I. Tertiary Dentin
• Histologically it may be..
oAtubular dentin: Some area may not
contain tubules.
oOsteodentin: when odontoblast cells
are included in the rapidly forming
matrix, then these cells degenerate
and vacate the space that they were
occupied.

23. Dentin
Age & Functional Changes
II. Dead Tract
• In response to sever stimulation results
in degeneration odontoblastic process
• Localized
• In ground section, these empty dentinal
tubules are filled with air, they appear
black in transmitted light and white in
reflected light, this optical phenomenon is
due to difference in the refractive index.
• Dead tract is bounded by narrow zone of
sclerotic dentin.
• It may be seen in normal dentin, due to the
death of odontoblasts crowded in the
narrow pulpal horn leaving empty tubules
which may be filled with air, and these
tubules give an appearance like dead tract

24. Dentin
Age & Functional Changes
III. Sclerotic Dentin
• It is a calcification of dentinal
tubules filled with collagen &
crystals
• In response to stimulus or normal
aging process “slowly progressing
caries or tooth abrasion”
• This dentin has uniform refractive
index because dentinal tubules are
occluded by calcium salts.
• It appears translucent when viewed
by transmitted light and dark by
reflected light.

25. Dentin
Pain Sensation
I. Innervation of Dentin
II. Theories of pain transmission

26. Dentin
Pain Sensation
I. Innervation of Dentin
• Intra-tubular nerves
• Nerves extends 100-150 µ in
between the DTs to form
Raschkow’s plexus or Sub-
odontoblastic plexus
• Some nerve fibers lose their
schwann cell coating pass between
the odontoblasts cell bodies and
enter the dentinal tubules.

27. Dentin
Pain Sensation
Exposure
of DTs
Enamel loss Gingival recession

28. Dentin
Pain Sensation
I. Direct neural stimulation
• Dentin contains nerve endings, which
respond when dentin is stimulated.
• Arguments:
o Nerve endings extends only 100-150 µ and
never reach near ADJ, which is the
most sensitive region.
o The application of local anesthetic to
the surface of dentin doesn’t abolish
the sensitivity.
o Newly erupted teeth are sensitive,
although plexus of Raschkow do not
establish until a tooth had erupted.

29. Dentin
Pain Sensation
II. Transduction stimulation
• Odontoblastic process conduct
impulses to nerve endings
• This theory is supported by the
neural origin of odontoblasts
“neural crest cells”
• Arguments
oThere is no neurotransmitter
vesicles in odontoblastic
process

30. Dentin
Pain Sensation
III. Hydrodynamic theory
• It is the most popular one, which proposed
that various stimuli as heat, cold, air affect
fluid movement in DTs which stimulate nerve
endings in plexus of Rashcow.
• Supporting
o When the cavity is dried with air “cavity
desiccation” or cotton wool. A greater loss
of fluid is induced, leading to more
movements and more pain
o The increased sensitivity at ADJ due to
profuse branching of tubules in this region.
o This theory explains why local anesthetics,
applied to exposed dentin, fail to block
sensitivity.

31.  Dentin hypersensitivity
o is a symptom reported in vital teeth with areas
of dentin exposed to the oral environment due
to degradation of the enamel or cementum
Dentin
Pain Sensation Treatment

32. Occluding DTs
• Adhesive material, desensitizing agents
exhibits reduction of dentinal fluid flow rate
• Potassium salts “potassium nitrate”, it disrupts
nerve impulses transmission
• Laser, Different mechanisms of action have been
proposed for laser
o Occlusion through coagulation of the proteins
of the fluid inside the dentinal tubules
o Occlusion of tubules through partial sub-
melting
o Discharging of internal tubular nerve
• Restoration, an invasive technique that
requires cavity preparation in the affected area
and placement of restorative material
Dentin
Pain Sensation Treatment