Microleakage and its effect. Includes factors affecting microleakage, the role of smear layer, cytotoxicity of dental materials, blood flow, lymphatics in pulp

1. PRESENTER:
MRINALINI

3. •Microleakage: Clinical problem
•Most dental materials: Varying
degree of microlekage
•Dentin being tubular:
permeability
I
N
T
R
O
D
U
C
T
I
O
N
Kidd EAM, 1976: Clinically undetectable passage of bacteria, fluids, molecules or ions
between a cavity wall and restorative material.

4. • Fluid shift
• A delta fibers
• Sharp, well localised
• Increased pressure due
to inflammation
• Mainly C fibers
• Long lasting, aching

5. Lin, Min, et al. "Fluid mechanics in dentinal microtubules provides mechanistic insights into the
difference between hot and cold dental pain." PloS one 6.3 (2011).

6. • Why few stimulus cause
outward movement and the
other inward movement of
fluid?
• Why is the stimulus generated
by hot test presents with long
lasting pain?

7. DENTINAL PAIN: Direct communication between oral fluids and pulp
• Restoration did not cover
the finish line
• Dentin beneath the margin
is exposed
• Cement dissolves before
complete set

8. CLINICAL SCENARIO
Purpose of this article: Examine the permeability
characteristics of dentin in order to learn pulpal
consequences of microleakage.
Pain free patient:
Prevent dentinal pain
than
microleakage
Example: Use of
GIC before
composite
Microleakage of bacteria
& their products but no
pain:GIC prevent
fluid
movement

9. PHYSICAL
FACTORS
Dentin permeability
proportional to:
Exposed tubule
diameter &
1/Dentin thickness
Full crown >> MOD

10. Preferred
material: Light
cured CaOH or
Polycarboxylate
If one removes
entire enamel: 6-12
million dentinal
tubules exposed.
Pink outline:
Functional
exposure- no
bleeding, dentin
extremely
permeable
RDT less:
Tubule diameter
increases
1
2
3
4

11. 1
2
3
REGIONAL
DIFFERENCES
More on pulp horn
than in the center
(intrinsic property)
STURDEVANT
AND
PASHLEY
Axial wall 7 times
more permeable
than pulpal floor
(RDT same)
THIN LAYER
OF ENAMEL
More effective at
reducing permeability
than most dental
material

12. Microcrystaline
debris
Embedded with
denatured
collagen
Partially
occludes
all
tubules
only 22%
permeable
Dissolves: pH
between
6.0- 6.8

13. Smear plug>>Smear layer
Maximum:
10
micrometer

14. 10-15
micrometer
space
Immediately gets
filled with oral fluids
containing microbes
fermentable carbohydrates, buffering capacity of saliva,
width of gap, age of plaque, accessibility of gap to oral
fluids
Plaque may generate
enough metabolic acids
to dissolve away smear
layer
Microleakage

15. In-vivo
microleakage
<< In-vitro
microleakage
Corrosive
products,
Calculus,
Outward
pulpal
hydrostatic
pressure,
Sclerosis
S.Mutans
inolulated on
dentin disks
in vitro
grown for
seven days
Smear
layer:
Could not
invade the
tubule due
to smear
plug
Acid
etch:
Invaded
the
tubule
1 5
2 4
3

16. Bacteria in tubule
Produce organic acid: Loss of
peritubular dentin
Release of Ca and PO4
Some Ca and PO4 rest on surface
of dentin other goes within the pulp
Equilibrium: Ions ppt out of solution to form a wide variety
of
intratubular crystal (caries crystal, at light microscopic
level sclerotic dentin)

17. Suspicion of dentinal sensitivity: Discover source using explorer or air
syringe
If subsurface marginal leakage
Soak a cotton pellet with saturated CaCl2 and paint over the
margin
Due to open communication between margin around
restoration and exposed dentin
Pain after 30-60 sec(delayed response as hypertonic solution
must osmotically move fluid through surface)
If positive response to hypertonic solution and negative to air blast: defect
is deep to the surface and restoration needs replacement

18. Smear layer: Somewhat resilient (wet sand)
Under weight: Compresses and recoils when unloaded
Gap between material and tooth
Branstrom et al: 0.2% EDTA(Tubulic acid)- remove smear layer without
disturbing smear plug
Prevention of microleakage: Varnish
Powell and Daines: Use of copalite(least solubility)
4% /week

19. Use of soluble oxalate
Sandoval et al: better than
copalite
Acidic, replace original
smear layer with calcium
oxalate

20. CYTOTOXICITY OF DENTAL MATERIALS
• Etched dentin: Increased wetness due to dentinal fluid leakage
• Decrease in ability of hydrophobic resin to wet surface leading
to poor adhesion
• Use of hydrophilic resin like HEMA (35-50%): Increase in
bond strength
• However, there are evidences of increase in permeability as
well

21. • Dentin restricts penetration of H+ ion
• Lee et al, Antonioli, Chan, Jensen: Brief exposure of
dentin to acid lead to little penetration of H+ ion across
0.4mm thin dentin
• Reason: Excessive buffer capacity of dentin
Brannstorm: No. of bacteria
proportional to degree of pulpal
response
Studies: ZOE, Silicate prevents
bacterial penetration failed to elicit
pulpal inflammation

22. PERMEATION/BLOOD FLOW BALANCE
• Balance : rate of entry of injurious substances into the
pulp from the dentin and their rate of clearance or
removal by pulpal blood flow
• Normal, healthy pulp: rapidly clear or remove substances
as they diffuse into the pulp from a buccal surface.

24. • Kim et al, 1984.: infiltration of LA solution containing epinephrine
causes profound decreases in pulpal blood flow for many minutes.
• Uninterrupted diffusion of bacterial irritants and from restorative
material
• Conc. of these materials reach high enough to cause direct
cytotoxicity or trigger inflammatory reactions: compromise pulpal
blood flow when the vasoconstrictor effect is gone.

25. Traumatic occlusion and rapid
orthodontic tooth
movement, especially intrusive
movement: nonpharmacologic
procedures that can reduce
pulpal circulation.
Rate of permeation of
bacterial products & their
clearance: upset by exposing
more dentin surface for
permeation

26. The relative rates of different processes is crucial in
determining whether the pulp survives or succumbs.
Bacterial endotoxin penetration : cause circumferential
inflammation
Leakage of plasma proteins from the microcirculation into
the dentinal tubules reducing the rate of toxin permeability
However, same microleakage of plasma proteins and fluid
from the vasculature to extra vascular space increases pulpal
tissue pressure which, in turn, reduces pulpal blood flow

27. Pashley:
• Definition of smear layer(1985) and its role in reduction of
permeability
• The importance of surface area, thickness, proximity to the
pulp chamber and the presence or absence of the smear
layer and time as determinants of dentine permeability.
• Ethylene diamine tetracetic acid was found to be most
potent conditioner for removing the smear layer and
opening up the orifices of the dentinal tubules (Pashey
1984)
• Role of liner for preservation of smear layer.
• Role of pulpal circulation in removal of noxious substance

28. Year Authors Material (teeth)
Method
lymphatic vessels:
PRESENT/ABSENT,
1894 Carreas Dog: deposition of
different chemical
compounds on
the pulp and theri
identification in urine
Absent
1897 Koerner Human: nterstitial
injection of gerota
mass to the pulp
Absent
1922 Magnus Human: Light
microscopy
Present
1957 Balogh and Boros Human: Light
microscopy
Present in Root pulp
only
1970 Eifinger Human Light microscopy:
Absent, Electon:
Present
1977 Bernick and Frank Human: Light
microscopy
Present
LYMPHATICS IN DENTAL PULP

29. Year Authors Material (teeth)
Method
lymphatic vessels:
PRESENT/ABSENT,
2000 Qi et al Human:Electron
microscopy
Present
2003 Oehmke Human: Light and
Electron microscopy
Present only in apical
third
2003 Pimenta Human: Light
microscopy
Present(Lymphangio
genesis)
2010 Gerli et al light and
transmission
electron mi
croscopy, western
blotting IHC
Absent, May appear
following
inflammation
2012 Szeląg et al Human: Light
microscopy, IHC
Absent

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