19/2/2015
PULP PROTECTION –Liners & Bases
Dr. Gaurav Garg
Lecturer,M.D.S
College of Dentistry, Zulfi, M.U.
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Intended Learning Objectives
By the end of the lecture,
the student should be able to :
Recognize the importance of pulp protection
Classify different types of pulp protecting materials
Discuss about cavity varnish, cavity liners ,bases
regarding definition,& composition, types,indications &
contraindications and disadvantages
To recognize the importance of pulp medication and pulp
capping in case of exposure of pulp
Analyze the criteria to select the procedure and
appropriate liners, bases for different restorative materials
Introduction:
Dental pulp is subjected to various types of injuries
before, during,& after restoration of carious tooth.
Irritants are caries, cavity preparation procedures,
restorative materials used, leakage & recurrent
caries
Need for Pulp Protection
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Pulp needs protection against various irritants as following
– Thermal protection against temperature
changes
– Electrical protection against galvanic currents
– Mechanical protection during various
restorative procedures
– Chemical protection from potentially irritable
components of restorative material
– Protection from microleakage at interface
between tooth and the restoration
Need of pulp protection from various irritants
Objectives of pulp protection:
 To prevent further irritation of Pulp-Dentin organ
and improve the defensive and reparative
capabilities of P-D organ
 To serve as a barrier against thermal changes,
chemical irritants from within the restorative
material and against leakage of bacterial by
products
Basic functions of pulp
protecting materials
– Insulate the pulp
– Protect the pulp in case of deep carious
lesion
– Act as barriers to microleakage and
chemical irritants from restoration
– Prevent bacteria and its toxins from
affecting the pulp
Ideal requirements of pulp
protecting agents
• Biologically compatible with p-d organ
• Chemically compatible with both p-d organ and the
restoration
• Should be capable of forming a non-permeable layer on cut
dentin with thickness not affecting the bulk of restoration or
its mechanical properties
• The material should not discolor either the restoration or the
tooth
•Should set/harden quick enough to allow subsequent
insertion of restorative material
•Low solubility in saliva
•Should withstand the condensation forces involved in
the placement of overlying restoration
•Stabilize and further decrease dentin permeability
•Easy to use and manipulate during mixing and
insertion.
Classification of pulp
protecting materials
1. Cavity Sealers
i) Cavity varnish
ii) Adhesive sealer
2. Cavity liners.
3. Sub-Bases.
4. Cement Bases.
CAVITY VARNISH
Definition:
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Cavity varnish is a solution of one or more resins
which when applied onto the cavity walls , evaporates
leaving a thin resin film, that serves as a barrier
between the restoration and the dentinal tubules
Composition:
Natural gum such as copal, rosin, or synthetic resin (10%)
dissolved in an organic solvent such as alcohol, acetone or
ether (90%)
The copal rosin is dissolved in the ether, when the ether
evaporates, a thin film of resin is left on the surface of
the cavity.
Uses :
1. As a barrier against Chemical irritants
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By preventing the penetration of acid from
the restorative material.
By preventing the penetration of Corrosion
products from amalgam restoration.
2. It minimizes the Marginal Leakage
around the restoration
3. As a barrier against biological irritants
(bacteria)
Disadvantages
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Not an effective Thermal Insulator even with
2-3 coatings.
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Very Sticky in nature.
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Water soluble.
Indications for cavity varnish:
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Below amalgam restoration – apply varnish to all the
cavity walls, pulpal floor & to the margins.
Below Zinc Phosphate Cement- apply varnish to the
pulpal floor, to prevent the acid penetration.
Contra-Indications:
1.Composite Resin:
Cavity varnish is contra indicated under
composite resin restoration because
 The solvent in the varnish will react with resin
& soften the resin
 Adhesive property is lost.
2. Glass Ionomer Cement:
Varnish interferes with chemical adhesion
property of the GIC
METHOD OF APPLICATION:
Applied by using a disposable brush tips or a small pledget
of cotton.
 It should be applied in2-3 coats
Thickness:
The film thickness is 5-10 microns
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DENTIN (ADHESIVE) SEALER
Recently dentin bonding agents have been used
to seal dentin tubules in place of cavity varnish.
Indications for use
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Treat or prevent hypersensitivity.
Used instead of a varnish.
Seal the dentinal tubules.
Ideal for use under all indirect restorations.
CAVITY LINERS
Definition:
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Cavity liners are agents which are used as
protective coatings on the freshly cut cavities &
in addition they have therapeutic action on
pulp.
Also called Suspension Liner
Composition
The basic components of the cavity liners are :
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Therapeutic agent ( CaOH , ZOE, F) – which is
dispersed or suspended in:
Resin solution , which acts as a carrier, the
solvent evaporates leaving a layer of Calcium
hydroxide or ZOE , on the cavity surface.
USE OF LINERS
•To protect pulp from chemical irritants by sealing
ability
It is used to provide a barrier against the passage of irritants
from cements or other restorative material and to reduce
the sensitivity of freshly cut dentin.
•To stimulate formation of reparative dentin
Application of cavity liner
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Is same as that of applying varnish
NOTE: It is mandatory to remove the liners
from margins /walls of the cavity , as
calcium hydroxide dissolves in the oral
fluids & is not effective against microleakage.
The thickness of the liner is 0.5mm.
Types of cavity liners
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Calcium Hydroxide based.
ZOE based.
GIC Liners.
Flowable composites
Calcium hydroxide has been used as
liner in deep preparations because of its
following features:
Limitations of Calcium hydroxide liners
Low strength
High solubility
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when it is exposed to the oral environment (e.g.
due to leakage) it dissolves. This limits its use over
only small areas requiring pulp protection.
ZOE liners
ZOE liners are contra-indicated below composite
resin restoration, as it interferes with
polymerization.
Glass ionomer liners
The modified GIC in the form of Resin
modified ( RMGIC) is commonly used
because of its
Advantages :
- Chemical adhesion.
- Good mechanical strength.
- Fluoride Release.
- Well controlled setting time.
- Rapid achievement of strength.
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Flowable composites as liners
– Flowable composites are the composites
with a lower amount of filler.
– This reduced filler content allows more
fluid consistency, less strength and less
stiffness than fully filled composites
Advantages of flowable composite
liners
– Adaptation to preparation walls
because of their flow
– Easy to place since the materials
are injected directly into the
preparation
– Esthetic
– Consistency
SUB-BASES
Therapeutic materials placed in deep portion
of the cavity preparation.
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They have specific pharmacological action.
They should be covered with supporting
base as they have low strength.
 Calcium
Hydroxide is most
commonly used as Sub-Base.
Properties:
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It has very low mechanical properties.
It has low compressive Strength, hence can not with
stand condensation forces.
It stimulates the formation of reparative dentin,
because of its alkaline Ph (11.7)
USES OF CALCIUM HYDROXIDE
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It can be used as cavity liner or sub – base or low
strength base .
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Material of choice for pulp capping.
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In extremely deep areas as an anti bacterial agent.
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It can be used with composite resin as it does not
interfere with the polymerization.
CEMENT BASES
Definition:
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Layer of cement that is placed under the permanent
restoration to protect the pulp against numerous types
of irritation is called Base.
The irritation could be thermal, mechanical & Chemical
irritation.
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Base is a replacement for protective dentin,
which is been destroyed during caries process
or during cavity preparation or both.
The thickness of Base is typically 0.5 -1mm.
CLASSIFICATION
HIGH STRENGTH BASES
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Zinc Phosphate Cement.
Zinc oxide Eugenol (ModifiedTYPE III)
Zinc poly carboxylate cement.
Glass ionomer cement.
Resin modified GIC (highest
strength- 150-200 Mpa)
LOW STRENGTH BASES
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CALCIUM HYDROXIDE(SELF CURE)
CALCIUM HYDROXIDE(LIGHT CURE)
ZINC OXIDE EUGENOL(TYPE IV)
Uses of base:
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As a chemical insulator.
As a Thermal insulator (minimum thickness0.75).
As a Mechanical support for the restoration by
distributing stresses to the underlying dentin.
The cements used as base should have sufficient
strength to withstand the forces of condensation so
that the base is not fractured during insertion of the
restoration.
CLINICAL CONSIDERATIONS
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The clinical judgment for the use of specific PULP
PROTECTION material depends on following factors:
FACTORS
--Remaining dentin Thickness (RDT)
- Design of the cavity.
- Adhesive property of the material.
- Proximity of the pulp to the cavity
floor
- Type of restorative material used.
Restorative Shallow cavity
material
( RDT=2mm or
more)
Moderately
Deep cavity
( RDT=0.52mm)
Deep cavity
(RDT=0.5mm or less)
Amalgam
Only sealer (varnish)
Base+ Sealer
Liner/sub base + base +
sealer
Composite
Nothing (restore
directly)
Resin modified
GIC base
Calcium hydroxide
liner/sub base+ Resin
modified GIC base
 For composites Cavity varnish, ZOE formulated liners & ZOE
base materials are contra-indicated as it interferes with
polymerization.
 GIC is the preferred base material for composite (best resin
modified GIC)
 Varnish/sealer should be applied on all walls & floors of
the cavity
 Bases/Sub-bases/Liners should be applied only on Pulpal
floor & Axial wall (in case of class II cavity)
 Never apply base/sub-base/liner on other walls and
Gingival floor (in case of class II cavity)
References & Suggested
reading
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Sturdevant's art & science of operative dentistry-2006Theodore M. Roberson, Harald O. Heymann, Edward J. Swift, Jr.
Principles of operative dentistry (2005)- A.J.E. Qualtrough, J.D.
Satterthwaite, L.A. Morrow and P.A. Brunton.
Fundamentals of Operative Dentistry- 2nd Edition- Summitt &
Robbins