Conservative iv script-2-cavity-liners-and-bases

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Cavity liners and bases
Why dentin is sensitive??
when you open a tooth you first cut enamel then you cut dentin,
by cutting dentin you are opening many dentinal tubules..so what
do you have to do to prevent dentin sensitivity???
for those who don’t understand the dentin sensitivity..I want you
to think when you eat ice cream or something very cold you get
that sensitivity (mmm,ouch) , that is dentin sensitivity, its very very
painful to your patients...
so in fact we have to deal with this dentin sensitivity ,there is
another tissue which is surrounding the area that you are working
with , which is the gingiva...the gingiva is very important, the
gingiva can be severely injured..
your cavity should be designed to accept a filling that is very
smooth and doesn’t create any harmful effect to the gingiva,
sometimes maybe you have a stagnation area (plaque
accumulation) and the result will be gingival inflammation and
that is not good...
therefore all of this characteristic features should be considered
when you are dealing with the tissues of the tooth, and as a
dentist all of us should know these characteristic..
therefore you should not extend the cavity margin to the
gingiva(subgingiva) unless carries has gone through to the
subgingival area...

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there is the contact point, what do u do with this contact point???
Don’t extend the caries beyond any other area that is not
necessary...
Cavity Liners and Bases
Aims of the lecture:
• The purposes of this lecture are to
• clarify the terms liners, bases and varnishes
• describe the different materials available in the clinics
• Understand the indications for the uses of each one.
• Why do some patient experience pain after a filling??
because you opened dentinal tubules, with that you have severed
many odontoblastic process, unless you do a lining that protects
the pulp or the rest of the opened dentinal tubules from toxicity
that came from the oral cavity or from dental materials...
microleakege...
the microleakege is due to shrinkage of the dental materials..you
put amalgam or composite, some of these material shrink and
when it shrink there is a gap between the filling and the margin of

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the tooth..that gap will allow oral fluids to go inside it, and this is
called microleakege and this microlekege will create some kind of
dentin sensitivity to the patient..
So postoperative dentin sensitivity might be due to :
- toxic products and stains from restorations
- Bacteria from the oral cavity
if u dont put a liner underneath the amalgam..the products of the
amalgam will cause toxicity to the pulp, or from microlekege
bacteria can leak in between the margins of the cavity and the
filling, because of the shrinkage and bacteria dentin sensitivity or
pain will happen or it may reach the pulp then there will be
pulpitis..
for this we need to know very well about:
- Liners
- cement bases
- GIC
these material used day by day in the cons clinic by the students...
first of all we will go through the Liners..
Liners
• Liners : aqueous or volatile organic suspensions or solutions
we don’t want them thick, if you get them thick they will fill the
cavity and we don’t want that because it has to be with minimal
thickness for amalgam to go inside the cavity, so I want them to

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be of minimal thickness and provide protection to the pulp from
the toxic product of the material or the bacteria that come from
the oral cavity
I want the liners to be thin films usually not exceeding a thickness
of 0.5 mm.
I want them to evaporate quickly, leaving behind a film residue
(barrier between the amalgam and the tooth), then we add our
restoration on the top of this film (thin,0.5mm)
• Liners may be classified into:
1. Solution liners or Varnishes
2. Suspension liners
1. Solution liners(varnishes): are solutions of natural gum or
synthetic resin..
Example of natural gum  Copal
Example of synthetic resin  Nitrated cellulose
and this natural gum dissolved in organic solvents such as:
- acetone
- ether
- chloroform
When solvent evaporates it leaves behind a semi permeable
membrane which can protect the dental pulp from toxic products

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of restorative materials as well as from microleakage of newly
placed amalgam.
when you see that tiny film is not enough what do you do? you
apply another layer..you have to see a thin shiny surface on the
floor and the walls of the cavity, once you see the shiny surface
then that’s is enough..
Example of varnish: Copalite
• Place a cotton pellet in the varnish, then swab the cleaned
cavity. Air dry and reapply varnish. Air dry again to see a
shiny hard surface which is ready to receive the gold or
amalgam restoration.
2. suspension liners :
- These liners contain suspensions such as calcium hydroxide
and or zinc oxide in a synthetic resin.
- They are applied to provide a barrier against irritating
compounds of most restorative materials

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E.G.--> DYCAL - you all have to know this name, when you read
Dycal you have to know that it is a suspension liner
Dycal(brand name)= Calcium hydroxide(scientific name)
Dycal:
- Radiopaque Calcium Hydroxide Composition is a rigid, self-
setting material useful in pulp-capping, and as a protective
base/liner under dental filling materials.
- Shown to protect the pulp and promote the formation of
secondary dentin
How it promote the formation of secondary dentin? This is a very
imp. Question in the VIVA exam..and the answer is :
The alkalinity of dycal is HIGH (11) and because of this alkalinity
the number of bacteria is LOW, so the formation of secondary
dentin proceeds.
Advantages of Dycal:
 Easy to place, with ability to flow where needed while it
stays in place when necessary
 It is alkaline and has antibacterial activity

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• It neutralizes the acid from restorative materials
Disadvantages Of Dycal :
• Low tensile strength
• Exhibit plastic deformation
• Undergo hydrolytic breakdown and dissolve under acidic
conditions.
• Bacteria may decompose it. Hence it may disappear under
restorations when there is microleakage.
Dycal is a very very important..in exam ,life ,viva… VERY VERY
IMPORTANT, you should ALL know what is DYCAL
- It comes as Single – paste system Dycal or visible light-cured
Dycal.
- It utilizes the polymerization of dimethacrylate by means of
light.
Now we said that the liners should be THIN, now we need
thickness in the bases
So let us move to the Cement Bases.
CEMENT BASES
any cement contains two elements :
- Base : main or supporting ingredient in material.
- Catalyst : substance that initiates a chemical reaction

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It May be placed in thick layers on the pulpal floors of deep
cavities to provide thermal, chemical and electrical insulation for
the dental pulp…
- thermal, I eat something hot or cold, I need something to
protect my pulp from the thermal irritation…
- chemical there is chemical reaction between two different
compounds in the oral cavity
BUT what about the electrical irritation ?? Where is the electrical
insult going to come from on the pulp?
from the GALVANISM .
So cement bases servers as protective (protect the pulp),
therapeutic (ZOE as a pein relief) or structural function (GI may
substitute dentin).
What is the material that resembles the dentin most? It’s the
Glass Ionomer
Which of the following materials is a substitute to dentin? Its Glass
Ionomer (VERY IMP.)
___________________________________
examples of bases :
Zinc phosphate cement :
Its not popular (because of its acidic feature) but its widely used
notice what happens when you mix the powder with the liquid :

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- A pH of 1.6 is found after 2 minutes of mixing..this is the
problem (1.6) if you put this base on dentin what is going to
happen? There will be immediately demineralization..
and if the protective layer of dentin is very thin over the pulp what
will happen?? Demineralization and the acid will go to the pulp
and the result will be Pulpitis, so you created a problem to the
patient…that’s why zinc phosphate is NOT popular among
dentists..
In the first 2 min. of mixing the ph is 1.6 then :
- pH below 4 within the first hour
- then it becomes normal pH 6 – 7 after 24 hours
this is a very rich lecture, and you expect many questions in the
exam from this lecture
• Uses and characteristics :
– Cementing agent for crowns and FPDs.
– Temporary restorations.
– Insulating base.
– Produces heat when mixed.
1. Phosphate, e.g. zinc phosphate
Disadvantage :
• It is soluble in oral fluids

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• It has no antibacterial properties
• It is very soluble in organic acids
2. Phenolate, e.g. zinc oxide eugenol cement
This is widely used in the dental clinics
• Zinc oxide powder + eugenol ..what is the eugenol? ‫زيت‬
‫القرنفل‬
• It provides good marginal seal
• It has antibacterial effects
• It has anodyne (tranquilizer) effect (due to eugenol)
Disadvantages :
• Low compressive strength
• Too long setting time (in the past we used to mix it a day
before use)
• It stains the composite restoration (this is a very bad
disadvantage) never put it underneath the composite
because its stains the composite
Because of this disadvantages Fortified cement is marketed by :
- adding silica, alumina or resin to the powder (it becomes
IRM) or,
- adding Orthoethoxybenzoic acid (EBA) to the liquid.
Reinforced zinc oxide-eugenol cements: contains natural or
synthetic resin to increase the compressive strength.

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3. IRM is a commercial example.
Uses and Characteristics of IRM:
– Temporary restoration up to 1 year
– Base or a temporary cement
– Not used under composite restorations (because of
eugenol)
EBA (ethoxybenzoic acid) cements: contains alumina and
polymeric reinforcing agent
Stailine is a commercial example.
So again as a quick summary :
- If we add the reinforcement to the powder  IRM
- If we add the reinforcmnet to liquid (EBA)  Stailine
-
4. Glass Ionomer Cement
Its another base that we can use it as a substitute to the dentin
• Powder = finely ground calcium aluminosilicate glass
• Liquid = polyacrylic-itaconic acid or other poly-carboxylate
acid copolymers

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So polyacrylic acid is mix with aluminosilicate glass to produce
Glass Ionomer Cement
Glass ionomer is a good restoration material in certain cases but is
mostly use as a base
Glass ionomer :
• Poor esthetics - rough surface
• Prolonged setting reaction
• Poor wear resistance
• Handling difficulties
Modifications to the GI :
• Refined formulation
– addition of tartaric acid
– more reactive acids
• Improved packaging
• Addition of resin
• We need it to be radiopaque so we add silver to have the
radiopacity
The advantages of GI :
The main advantage of GI is releasing Fluoride and you can charge
it with fluoride as you charge the battery again and again, when
fluoride is depleted from the GI you brush your teeth with

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fluoridated toothpaste, so your tooth will be fluoridated again
because of the toothpaste..
• So again the advantages are :
1. Inherent (chemical) adhesion to tooth structure
2. Fluoride release
3. Coefficient of thermal expansion (CTE) similar to tooth
structure
4. Biocompatible
5. It has high compressive strength
6. It is able to leach fluoride
7. It has good marginal seal. Why? because It bonds chemically
to enamel and dentine
Uses and Characteristics.
• Cementing crowns and FPDs.
• Temporary filling.
• Base material.
• resist recurrent decay.
Why its resistant to recurrent decay? Because of fluoride
release
Disadvantages :
1. Sensitive to moisture and desiccation

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2. Low fracture toughness
3. Low flexure strength
4. Low wear resistance
5. Relatively poor esthetics
Indications for the using of GI :
• Class 5
• Root caries
• Pediatric dentistry:
- resin-modified version
• Tunnel preparations
• Atraumatic restorative treatment (ART)
I want to go to the properties :
Composite is better than GI in case of strength .

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Compomers is close to the composite and if you go to the other
side you will see that RMGI is close to the GI…
STRENGTH : 1. Composite..2. compomers..3..RMGI..4..GI
POLISHABILITY : Same as the strength, but you cannot polish the
GI, even if you polish it, it doesn’t sustain a good polish surface.
FLUORIDE RELEASE : It’s the opposite of the above..
So if you go to the composite its almost NONE
If you go to the compomers its moderate
If you go to the RMGI its higher
And the highest is the GI
so I want you to differentiate between GI, RMGI, compomers and
composites in the term of flexural Strength, compressive strength
and fluoride release… (in the table above)
Clinical Applications :
1. Cavity extending 0.5 mm in dentin: just beneath the
enamel
• Coat the cavity with two layers of resin varnish using brush.
• No insulating cement base is required.
• DON’T deepen a cavity by removing dentine in order to place
an insulating base.(no need, just stop where the caries end)
2. What if its more than 0.5 mm in dentin ? Cavity
penetrating further:

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• Place modified zinc oxide eugenol or GIC over the pulpal floor
or axial wall.
• Apply varnish before zinc phosphate but after GIC.
3. Very deep cavities 0.5mm from pulp, that means very
close to the pulp and you can see the shade of the
pulp..here you should STOP, so that you don’t expose
the pulp..then :
• line with calcium hydroxide cement
• Place cement base GIC
• apply varnish
• Place filling
The doctor stopped here and he left 3 slides and here they are :
Vitrebond :
• Is resin modified glass ionomer RMGI
• 3M ESPE
• Vitrebond is light-cure glass ionomer liner/base.
• It is recommend for use as a liner or base under composite,
amalgam, metal and ceramic restorations.
• Vitrebond Liner/Base is not indicated for direct pulp capping.
• If a pulp exposure occurs, cover the exposure with a calcium
hydroxide material. Place the Vitrebond liner/base over the
calcium hydroxide and surrounding dentin to seal and
protect the exposure.

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Composite Resin Restorations :
• If the cavity is deep, line it with calcium hydroxide or
Vitrebond
• Shallow cavities: no need for lining or use dentine bonding
agent instead
• Recurrent caries: use light activated glass ionomer cement.
END OF THE LECTURE
Done By : Musap AL-rawi
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