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CONTENTS
INTRODUCTION
Pulp protection refers to protection of pulp from external irritants.
Restorative dental materials provide excellent properties for bulk of dental
restoration . But do not protect pulp or preserve its health
Considerations include :
[
Chemical
protection
[
Electrical
protection
[
Thermal
protection
[
Pulp
medication
[
Mechanical
protection
OBJECTIVES FOR PULP PROTECTION :
1) Mild and strong chemical or mechanical insults
2) If insult produces fluid flow, in or out of dentinal tubules, pressure
change is sensed by mechanoreceptors within pulp and patient experiences
sensitivity.
3) Leakage of chemical irritants from bacteria or dental materials- pulp
becomes inflamed
4) Smear layer
1. It is 25 % to 30 % porous
2. Produce dentinal tubule sealing
3. Long term diffusion can occur – so
necessitates sealing of smear layer for chemical protection
CLASSIFICATION OF PULP PROTECTIVE
AGENTS
1.
Cavity
sealers
· Cavity Varnish
· Resin bonding agents
2.
Cavity
Liners
3. Cavity base
CAVITY VARNISH
·
In
shallow cavity : For amalgam restorations , cavity varnish used
·
Help
reduce postoperative sensitivity due to micro leakage
·
Contraindicated
under :
∞
GIC –
interferes with adhesion
∞
Composite
– interferes with polymerization
Composition
|
Components
|
|
|
1.Solid
|
10% copal
resin
|
|
2.Solvent
|
90%
ether,acetone,alcohol
|
|
3.Setting reaction
|
Physical-by
solvent evaporation
|
|
Structure
|
|
|
1.Arrangement
|
Amorphous film
|
|
2.Bonding
|
Covalently
bonded organic material
|
|
3.Composition
|
Single phase
|
|
4.Defects
|
Pores &
cracks
|
|
Physical
properties
|
|
|
1.Thermal & electrical
|
Insulator
|
|
2. .Wetting
|
Poor on
hydrophilic surfaces
|
|
Chemical
properties
|
|
|
1.Solubility
|
Low
|
|
Mechanial
properties
|
|
|
1.Tensile strength(Mpa)
|
<1
|
|
2.Elongation
|
<0.1%
|
|
Biologic
properties
|
|
|
1.Toxicity
|
None,if
solvent eliminated safely
|
RESIN BONDING AGENTS
-
Dentin
bonding agents
-
For
adhesion and seal prepared tooth
-
Bonding
for amalgam restorations to reduce micro leakage
-
For
indirect restorations : Ceramic inlays, veneers, cast restorations
-
-
CAVITY LINERS
●
Liners
placed between dentin and restoration to
provide pulpal protection
●
Use
depends on extent and location of preparation and restorative material to be
used.
CALCIUM HYDROXIDE
It can be used in deep cavity
Advantages :
«
Pulpal
biocompatibility
«
Stimulate
reparative dentin
«
Antibacterial
activity
-
To
prevent loss, a base is placed over it
Disadvantages :
«
Low strength
«
high solubility
«
Loss or softening under poorly sealed
restorations
GLASS IONOMER CEMENT
Used for moderate to deep cavities
-
As liner
under amalgam, cast gold, composite restorations
Advantages :
«
Good
biocompatibility
«
Good
strength
«
Fluoride
release
«
Chemical
adhesion to tooth structure
CAVITY BASES
«
Used to
replace missing dentin or block undercuts in preparations for indirect
restorations
«
Thickness
: 1 – 2 mm
«
Provide
thermal protection and adequate strength
«
Applied
on pulpal and axial walls of cavity preparations
«
Eg. Zinc
phosphate cement, zinc polycarboxylate cement, glass ionomer cement type (III)
Zinc phosphate cement
•
Excellent
thermal insulation
Zinc polycarboxylate cement
•
Biocompatible
•
Adhesion
to tooth structure
Glass ionomer cement
•
Mild to pulp
•
Good
adhesion to tooth structure
•
Fluoride
release
•
Adequate
strength as base
•
Compatible
with all restorative materials
- Used under amalgam, composite
resin, cast gold, ceramic restorations
|
Zinc phosphate cement(modern TENACIN)
|
Polycarboxylate cement (DURELON)
|
Glass ionomer cement(KETAC-CEM)
|
|
|
Components
|
|||
|
1.Component 1
|
ZnO powder
|
ZnO powder H2O
|
F-Al-Si glass powder
|
|
2.Component 2
|
H3PO4/H2O
|
Polyacrylic acd/H2O
|
Polyacrylic acid/H2o
|
|
3.P/L ratio
|
High
|
High
|
High
|
|
4.Setting reaction
|
Acid-base reaction
|
Acid-base reaction
|
Acid-base reaction
|
|
Structure
|
|||
|
1.Arransgement
|
Crystalline matrix & fillers
|
Amorphous matrix,crystalline
fillers
|
Amorphous matrix,crystalline
fillers
|
|
2.Bonding
|
Ionic
|
Covalent,ionic
|
Covalent,ionic
|
|
3.Composition
|
Multiphase
|
Multiphase
|
Multiphase
|
|
4.Defects
|
Pores & cracks
|
||
|
Physical properties
|
|||
|
1.Thermal & electrical
|
Insulator
|
Insulator
|
Insulator
|
|
Chemical properties
|
|||
|
2.Solubility
|
0.10 (low)
|
Low
|
0.10(low0
|
|
Mechanical properties
|
|||
|
1.Compressive strength(Mpa)
|
77
|
100
|
120
|
|
2.Diametral tensile strength
(Mpa)
|
-
|
17
|
-
|
|
Biologic properties
|
|||
|
1.Safety
|
Acceptable
|
acceptable
|
Acceptable
|
METHOD OF PULPAL PROTECTION
|
Materials
|
Shallow excavation
(RDT>2mm)
|
Moderate excavation
(RDT 0.5-2mm)
|
Deep excavation (RDT<0.5mm)
|
|
Amalgam
|
no/no/sealer
|
No/base/sealer
|
CH/base/sealer
|
|
Composite
|
No/no/DBS
|
No/no/DBS
|
CH/No/BDBS
|
|
Gold inlays and onlays
|
No/No/cement
|
No/Base/cement
|
CH/Base/Cement
|
|
Ceramic, PR,FRP
|
No/No/DBS,CC
|
No/No/DBS,CC
|
CH/No/DBS,CC
|
PULP CAPPING
INDIRECT PULP CAPPING
«
Retention
of soft dentin near pulp and medication of remaining dentin with calcium
hydroxide
«
Reinforced
GIC / reinforced zinc oxide eugenol over calcium hydroxide liner
Criteria :
«
No
history of spontaneous pulpal pain
«
Normal
response to vitality tests
«
No
periapical involvement
Procedure
«
Administer
LA. Isolate tooth with rubber dam
«
Remove
all undermined enamel – high speed handpiece with air water spray
«
Excavate
carious dentin
«
Apply
calcium hydroxide liner over demineralised dentin
«
Place
reinforced GIC or reinforced Zinc oxide eugenol over liner
«
Place
permanent restoration after 6 to 8 weeks after evaluating patient’s response
DIRECT PULP CAPPING
«
To seal
exposed pulp with material that promotes reparative dentin formation
«
Calcium
hydroxide is choice for direct pulp
capping
Criteria :
«
Asymptomatic
tooth – no spontaneous pain, no abnormal response to thermal stimuli
«
Size of
exposure less than 0.5mm diameter
«
Hemorrhage
– easy to control
«
Area of
exposure must be uncontaminated by saliva or gingival fluids
Procedure :
«
Administer
LA . Isolate tooth with rubber dam
«
Control
hemorrhage with cotton pellet
«
Place
calcium hydroxide over exposed pulp
«
Place
base/ liner
«
Place
reinforced GIC/ reinforced zinc oxide eugenol
«
Place
permanent restoration after 6 to 8 weeks
Substitutes for liners
DENTIN BONDING SYSTEMS
Involve unfilled, liquid acrylic monomer
mixture placed onto an acid etched and
primed dentin surface
«
Hydrophilic
monomers (2-HEMA)
«
Dissolve
hydroxyapatite crystals
«
Forms
interpenetrating network around dentin collagen
«
Hybrid
zone : 0.1 – 5 µm deep
«
Micromechanical
bonding is formed
Two component system :
8 Etching with priming or
8 Bonding or etching or
8 Priming
with bonding – self etching primers
One component system :
8 Latest dentin bonding system
8 Combination of all three stages into single
component
AMALGAM BONDING SYSTEMS
M
To seal
underlying tooth structure and bond amalgam to enamel and dentin
M
4-
methyloxy ethyl trimellitic anhydride (4-META) is used
M
No
chemical bonding
M
Thick
layers (10 – 50µm)
M
Forces
fluid components of amalgam into unset bonding layer
M
Produce
micromechanical laminations
Advantage:
Ø
Dentin
sealing
Ø
Improved
resistance form
CONCLUSION
8 Survival of liners and bases has never been
well understood
8 During restoration removal , difficult to
completely remove restoration and assess liners and bases
8 Solution liners provide only chemical
protection for days or weeks,thin and brittle
8 Bonding agents may survive years
8 Traditional calcium hydroxide liners
dissolve, lose 10% to 30% volume over 10 or more years
8 Long term changes in both cement liners and
bases – not well characterized
8 Under these circumstances it is judicious to
remove most liners and bases during rerestoration procedure.
REFERENCES
Sturdevant’s
- Art and science of operative dentistry
Remya raghu
- Clinical operative dentistry
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