Dental cements /certified fixed orthodontic courses by Indian dental academy

DENTAL CEMENTS

INDIAN DENTAL ACADEMY
Leader in Continuing Dental Education
www.indiandentalacademy.com


TERMINOLOGY

Cement – Substance that hardens to act as a
base, liner, filling material, or adhesive to bind
devices and prostheses to tooth structure or to
each other.

Base – Layer of insulating, sometimes
medicated, cement, placed in the deep portion of
the preparation to protect pulpal tissue from
thermal and chemical injury.


Cavity Liner – Thin layer of cement, such as
a calcium hydroxide suspension in an aqueous or
resin carrier (after evaporation), used for
protection of the pulp;

Varnish – A solution of natural gum, synthetic
resins, or resins dissolved in a volatile solvent,
such as acetone, ether, or chloroform.


Intermediate restoration – Tooth filling or
prosthesis that is placed for a limited period, from
several days to months, and is designed to seal
teeth and maintain their position until a long-
term restoration is placed;

Luting agent – A Viscous material placed
between tooth structure and a prosthesis that
hardens through chemical reactions to firmly
attach the prosthesis to the tooth structure.

CEMENT BASES

DEFINITION:
- A base is a layer of cement placed under the
permanent restoration to encourage recovery of
the injured pulp and to protect it against
numerous types of insult [thermal, chemical or
galvanic] to which it may be subjected.


TYPES:
1. High strength bases: are used to provide thermal
protection for the pulp , as well as mechanical support for
the restoration.

2. Low strength bases: have minimum strength and low
rigidity . Their main function is to act as a barrier to
irritating and to provide therapeutic benefit to the pulp.


HIGH STRENGTH BASES LOW STRENGTH BASES

- Zinc phosphate - Calcium hydroxide

- Zinc polycarboxylate - Zinc oxide Eugenol

- Glass ionomer cement
[type III]

- Reinforced Zinc oxide Eugenol


ZINC PHOSPHATE CEMENT:
It is the oldest of the luting cements

INDICATIONS :
- Luting of restorations
- High strength bases
- Temporary restorations
- Luting of orthodontic bands and brackets


CLASSIFICATION:

Type I: Fine grained for luting.
Film thickness should be 25 um or less.

Type II: Medium grain for luting and filling.
Film thickness should not be more than
40 um.


MODE OF SUPPLY:

I. Powder and liquid system.

II. Capsules of preproportioned powder and liquid


COMPOSITION:
POWDER:

- Zinc oxide : 90.2% Principal constituent

- Magnesium oxide : 8.2% Aids in sintering

- Other oxides : 0.2% Improves smoothness of mix
[ like bismuth trioxide,
calcium hydroxide, barium
oxide]
- Silica : 1.4% Filler, aids in sintering.


LIQUID:
- Phosphoric acid : 38% Reacts with zinc oxide

- Water : 36% Controls rate of reaction

- Aluminium phosphate : 16.2% Buffers, to reduce
or zinc phosphate rate of reaction

- Aluminium : 2.5%

- Zinc : 7.1%

SETTING REACTION:

- When powder is mixed with liquid, the phosphoric
acid attacks the surface of particles , dissolving the
zinc oxide forming acid zinc phosphate.

- The aluminium of the liquid is essential for cement
formation. The aluminium complexes with the
phosphoric acid to form a zinc aluminophosphate gel .

SETTING TIME: 5 to 9 minutes.


CONTROL OF SETTING TIME:
a) Manufacturing process-
1. Sintering temperature: Higher the temperature ,more
slowly the cement sets.
2. Particle size : Finer particles react more quickly as a
greater surface area is exposed to the
liquid.
3. Water content of the liquid: excess water accelerates
the
reaction whereas less water
retards the reaction.
4. Buffering agents : slow down the reaction.

b) Factors under the control of operator:
1. Temperature: Higher temperature accelerates
the reaction.
2. Powder/liquid ratio: More liquid employed ,slower
the reaction.
3. Rate of addition of powder to liquid: The reaction is
slower if the powder is
incorporated into the liquid
slowly.
4. Mixing time: Longer the mixing time, slower is the
rate of reaction.


PROPERTIES:
1. COMPRESSIVE STRENGTH:
Maximum strength is attained in the first day
103.5Mpa(15000Psi)
Factors affecting strength are:
a) Powder/ Liquid ratio: More the powder added into
liquid, greater is the strength.
b) Water content: A change in the water content of the
liquid, either loss or gain, reduces the strength.

2. TENSILE STRENGTH:
This cement is weaker in tension, thus making it
brittle. 5.5Mpa(800Psi)

4. MODULUS OF ELASTICITY: 13 Gpa

5. SOLUBILITY AND DISINTEGRATION:
Shows relatively low solubility. 0.06% wt

6. FILM THICKNESS: The smaller the particle size,
less
is the film thickness.

7. THERMAL PROPERTIES: Are good thermal
insulators and may be effective in reducing galvanic effects.

8. ADHESIVE PROPERTIES: The retention is by
mechanical interlocking of the set cement with the surface
roughness of www.indiandentalacademy.com
the cavity and restoration.

8. BIOLOGICAL PROPERTIES:
- Due to the presence of phosphoric acid , the
acidity of the cement is quite high at the time they are
inserted in the tooth.
- 3 min after start of mixing Ph is 3.5 and later
rapidly approaches neutrality in 24 to 48 hours.

Therefore damage to the pulp by acid occurs
during the first few hours after insertion.


MANIPULATION:
- A cool glass slab is used in order to delay the setting
and allow more powder to be incorporated before the
matrix formation occurs.
- The liquid should be dispensed just before mixing.
- The powder is added in small increments.
Recommended ratio is 1.4gm/ 0.5ml
- Mixing is initiated by addition of a small amount of
powder at a time into the liquid.
A large area is covered during mixing in order to
dissipate the exothermic heat.
- Spatulation is carried out with a brisk, circular motion
of the spatula.

- Each increment is mixed for 15 to 20 sec before the
next increment is added.
Mixing time : 1 min 20 sec.

- The field of operation should be kept dry during the
entire procedure.


ZINC OXIDE EUGENOL
- Zinc oxide eugenol (ZOE) is the most
widely used temporary restorative material.
- It seems to have been developed from
zinc oxy-chloride cements, which consisted of a
powder: 75% zinc oxide and 25%
pulverized glass or silica and
liquid: zinc chloride and a little borax.
- They were slow setting, and a
notable shrinkage was generally observed.

- As an approximately neutral pH of
7.0.
- Unfortunately its strength is not
sufficient enough to resist forces of
mastication, lacks resistance to wear and has
relatively high solubility in the oral cavity.


APPLICATIONS :
1. Base
2. Temporary cementation
3. Temporary restoration
4. Cavity liner
5. Endodontic sealer


Classification :
ADA specification No. 30 has listed 4 types
Type I: Temporary cementation.

Type II :Permanent cementation.

Type III :Temporary filling material and thermal
insulation.
Type IV : Cavity liners.


COMPOSITION
POWDER:

•Zinc oxide – 69.0% - Principal ingredient
•White rosin – 29.3% - To reduce brittleness of set
cement

•Zinc Stearate – 1.0% - Accelerator, Plasticizer

•Zinc Acetate – 0.7% - Accelerator, improves
strength
•Magnesium Oxide – Is added in some powders,
it acts with eugenol in a similar

LIQUID :
Eugenol – 85.0 – Reacts with zinc oxide
Olive oil – 15.0 – Plasticize

SETTING :
The setting reaction is a typical acid-base
reaction to from a chelate. The reaction is also known as
CHELATION and the product is called ZINC EUGENOLATE.

Zn0 + H2O………………..Zn(OH)2

Zn(OH)2 + 2 HE ……………ZnE2 + 2H2O

Base Acid the salt

(Eugenol) (Zinc Eugenolate)

The chelate (Zinc Eugenolate) formed is a matrix
surrounding free zinc oxide particles. The chelate thought
to form as an amorphous gel that tends to crystallize

- The water formed in the setting
reaction aids in biding the individual chelate units
together in a chain or in an octahedral structure,
or the water may be merely absorbed by the excess
Zinc Oxide.

- The free eugenol content of the set
cement is probably very low.


PROPERTIES :
1. Mechanical Properties:
a) Compressive strength:

-They are relatively weak cements. The
strength depends on the intended use of the
materials.

-For example, cements intended for
temporary purposes like temporary restorations
and cementation (Type I), and cavity lining (Type
IV), will have a lower strength.

- Cements intended for
permanent cementation (Type II) and
intermediate restorations will be more
stronger.

- The compressive strength ranges
from a low of 3-4 Mpa upto 50-55Mpa.

- The smaller the particle size, the
stronger the cement. The strength can also
be increased by reinforcing with alumina –

b) Tensile strength:

Ranges from 0.32 to 5.8 Mpa.

c) Modulus of Elasticity:

Ranges from 0.22 to 5.4 Gpa.

2.THERMAL PROPERTIES:

a) Thermal conductivity:

Their thermal insulting properties are
excellent and are approximately the same as for human
dentin.

- The thermal conductivity of zinc
oxide-eugenol is in the range of insulators like cork
and asbestos. 3.98 (Cal. Sec-1 cm-2 (°C/cm)-1 x 10-4.
b) Co-efficient of thermal expansion: 35 x 10-6/°C.
- The solubility of the set cement is high,
the highest among the dental cements.
- They disintegrate in oral fluids. This break
down is due to hydrolysis of the zinc eugenolate
matrix to from zinc hydroxides and eugenol.

- Solubility is reduced by increasing
the powder/liquid ratio.

a) pH and effect on pulp: They are the least
irritating of all dental cements.

In terms of pulpal response they are classified
as mild. pH is 6.6 to 8.0

b) Bacteriostatic and obtuandant
properties: They inhibit the growth of bacteria and
have an anodyne or soothing effect on the pulp in
deep cavities, reducing pain when it is present.

Modified zinc oxide eugenol cements:

- To improve upon the working, handling
and setting characteristics, various modifications
were tried and are still being tried. Improved
properties have been achieved by two approaches:
Partial substitution of eugenol by –ethoxy-
benzoic
acid (EBA)
 Addition of fused quartz or aluminium oxide or
resin polymer to the powder component

Resin reinforced zinc oxide eugenol cements :

- The conventional zinc oxide
eugenol cements have been modified by the
addition of polymeric substances like polymethyl
methacrylate to the powder component.

- The degree of reinforcement
appears to be dependent to a great extent upon the
particle size and on uniformity of distribution of
the resinous and inorganic phases of the powder
components.

- 20% polymethly methacrylate is
usually added to zinc oxide as powder and is mixed
with eugenol along with accelerators like zinc
acetate and zinc stearate.

- Thymol or hydroxyquinoline as
antimicrobial agents are added in traces.


The constituents of powder and liquid is as follows:

POWDER WEIGHT %

Zinc oxide 80.0%

Polymethyl-methacrylate 20.0%

Zinc stearate traces
Zinc accetate traces
Thymol traces
LIQUID:
Eugenol 85 %
Olive oil www.indiandentalacademy.com
15%

- Resin improves the strength,
homogenicity and smoothness of the mix,
decreases flow, brittleness and solubility.

- Resin may physically bond to the
other components or react chemically with the
eugenol.


- Zinc stearate acts as a plasticizer and zinc
acetate improves the strength of the cement.

- Zinc stearate and zinc acetate also acts as
accelerators.

- Olive oil acts as a plasticizer and masks
the irritating effects of eugenol.


GLASS IONOMER CEMENTS


Definition (Akinmade & nicholson, 1993) :

- Water based cement where-in following
mixing, the glass powder & polyalkenoic acid
undergo an acid/base setting reaction.

- The acid attacks the surface of powder
particles, releasing calcium & aluminium ions, thus
developing a diffusion-based adhesion between
powder & liquid.

INDICATIONS:
- For eroded areas like erosion, abrasion and class V
restorations.
- Anterior esthetic material for class III cavities.
- As luting agent
- As liners and bases
- For core build-up
- To a limited extend pit and fissure sealants.


Uses of GIC

EROSION / ABRASION LESIONS

CLASS V CARIOUS LESIONS

CLASS III CARIES

MNIMAL CAVITY PREPARATIONS

Pits and fissures Primary Teeth restorations

Bracket Bonding

Luting of crowns

Core Build-up

CONTRAINDICATIONS:
 Class IV carious lesions of fractured incisors.

 Lesions involving large areas of labial enamel
where esthetics is of major importance

 Class II carious lesions where conventional cavities
are prepared; replacement of existing amalgam
restorations.
 Lost cusp areas.

CLASSIFICATION:
According to skinners:
Type I – Luting
Type II- Restorative
Type III- Liner and base
According to Sturdevent:

1. Traditional or conventional
2. Metal modified GIC
a. Cermets
b. Miracle mix
3. Light cured GIC
4. Hybrid (Resin modified GIC)
5. Polyacid modified resin composite or Compomer

According to clinical use as:
Type I- Luting
TYPE II- Restorative
Type III- Liner/ Base
Type IV- Pit & Fissure Sealant
Type V- Luting for Orthodontic Purpose
Type VI- Core build up material
Type VII- High fluoride releasing GIC
Type VIII- ART
Type IX- Geriatric & Paediatric GIC

COMPOSITION OF CALCIUM FLUROALUMINOSILICATE

GLASS POWDER:
COMPONENT WEIGHT%

SiO2 [quartz] 29
Al2O3 [alumina] 16.6
CaF2[fluorite] 34.2
Na3AlF6[cryolite] 5
AlF3 5.3
AlPO4 9.9

POWDER:

- The composition of the glass is an acid soluble

calcium aluminosilicate glass.

- Formed by fusing silica[Sio2], alumina [Al2O3],

calcium fluoride / fluorite(CaF2), at 11000C to 15000C

temperature.

- The glass is crushed, milled and then ground to a

fine powder {20u – 50u)


LIQUID :
- POLYACRYLIC ACID(45%)
Polyacrylic : Itaconic  2:1
- ITACONIC ACID
- MALEIC ACID
- TRICARBOXYLIC ACID
- TARTARIC ACID(5-15%)
- POLYPHOSPHATES
- METAL OXIDES
- WATER


LIQUID:

- The liquid was an aqueous solution of polyacrylic

acid in a concentration of about 50%.

- The liquid was quite viscous and tended to gel over

time.

Hence, acrylic acid was copolymerised with other acids

such as iticonic ,maleic,and tricarboxylic acid.


SETTING REACTION :

The setting reaction of glass Ionomer
cements involves three overlapping stages.

Stage1: Dissolution

Stage2: Precipitation of salt, gelation and hardening

Stage3: Hydration of salts.

ADHESION:

- Glass ionomer cements have the important property

of adhering to untreated enamel and dentin.

- It reacts with the smear layer on cut dentin and also

bonds to other reactive polar substrates such as the base

metals.


ADHESION OF GIC:

- Polyalkenoic acid attacks the dentine and
enamel and displaces phosphate and calcium (or
strontium) ions.
- These migrate into the cement and develop
an ion enriched layer firmly attached to the tooth
structure.
- Dentinal tubules will remain sealed and
microleakage can only occur into the cement.

Comparative properties of glass ionomer cement
Property TYPE- I TYPE- II TYPE- III
P:L ratio 1.5:1 3:1 3:1
Working time 3.5 2.0 2.0
Setting time 7.0 5.0 4.0
Compressive 120 150-200 120
strength(Mpa)
Tensile 9-12 15-20 6-10
sterngth(Mpa)
Flexural strength 12-15 18-20 13-16
Surface hardness 160 200 120
Film thikness(uM) 20 - -
Coeff.thermal - -6 -6
expansion 13x10 8x10
Solubility 0.1 0.1 0.1

PROPERTIES:
PHYSICAL PROPERTIES –
EFFECT ON PULP AND CELLS:

- The glass Ionomer causes greater inflammatory
response than zinc-oxide eugenol cement but less than zinc
phosphate cement and the silicates

- Freshly mixed materials is very acidic between (0.9
and 1.6) which causes mild inflammatory response of pulpal
tissues but it resolves within 30 days and there is no
enhancement of reparative or secondary dentin formation.


- Although the glass ionomers are acidic they are less
irritant than silicates

- The acid used in glass Ionomer cement i.e. the
polyacrylic acid is weaker than phosphoric acid.

- The polyacid chains are large and immobile being
further restricted by their affinity for calcium ions in the
tooth on which the material is applied.


Fluoride Release:

- Fluoride ions released from the restorative
materials become incorporated in hydroxyapatite
crystals of adjacent tooth structure to from structure
such as fluorapatite that is more resistant to acid
mediated decalcification.

- The fluoride originates from that used in
preparing the alumino silicate glass, which can contain
upto 23% fluoride


ASTHETICS:

- The glass ionomer cement is an aesthetic filling

material because it has a degree of translucency which arises

because it’s filler is a glass.

- The colour of glass ionomer remains unaffected

by oral fluids as compared to composites which tend to

stain. Translucency increases as they age and is reflected by a

decrease in opacity.

DIMENSIONAL STABILITY:

A correctly manipulated and protected glass

ionomer material shows a volumetric setting contraction

of approximately 3% which develops slowly through the

setting process.


Thermal Properties:
The thermal diffusivity value of glass

Ionomer cement ions is close to that for dentin. Hence

the material has an adequate thermal insulating

effect on the pulp and helps to protect it from thermal

trauma.


DISPENSING AND MIXING

Glass ionomers are available commercially in two forms:

-

Powder and liquid supplied separately, or hand

mixing.

Encapsulated, or mechanical mixing.


DISPENSING
STANDARDIZE POWDER IN SPOON

DISPENSE LIQUID TO AVOID AIR BUBBLES


MIXING
MIXING POWDER AND LIQUID USING PLASTIC SPATULA

FOLDING TECHNIQUE FOR MIXING


FINISHING & POLISHING
- No finishing for 24 hours.
- If essential, sharp blade to reduce gross
contour
- After 24 hours, fine diamond with air/ water
spray for gross contour.
- Rubber polishing points for refining
- Polishing discs for glossy finish
- sealing with resin sealant or vaseline.

RECENT ADVANCES IN GLASS IONOMER CEMENTS

• METAL – MODIFIED GLASS IONOMERS
- MIRACLE MIX
- CERMET

• RESIN MODIFIED GLASS IONOMERS

• POLY ACID- MODIFIED COMPOSITE RESINS /
COMPOMERS


METAL – MODIFIED GLASS IONOMER CEMENTS

- Glass ionomer cements lack toughness and hence,

cannot withstand high-stress concentrations.

- GIC have been modified by the inclusion of metal

filler particles in an attempt to improve toughness

Two methods of modifications have been employed.


SILVER ALLOY ADMIX or MIRACLE MIX

- Sced and wilson (1980) found that amalgam

alloys could be incorporated into glass ionomer cements

and that these served to increase the flexure strength.

- Spherical silver amalgam alloy powder is mixed

with Type II glass ionomer powder in the ratio 7:1.


- These systems have been used clinically by

Simmons(1983). However, their esthetics are poor –they

tend to impart a gray to blackish colour to the cement

and they do not take burnish.


CERMET – IONOMER CEMENTS:

- In an attempt to improve the abrasion resistance and

strength of GIC, McLean and Gasser(1985) developed the

“cermet”-ionomer.

- These cements, unlike simple mixtures of alloy particles

or metal fibres, contain glass-metal powders sintered to high

density that can be made to react with polyacids to form a

cement.

RESIN – MODIFIED GLASS IONOMER CEMENT:

-Low early strength and moisture sensitivity of the

traditional glass ionomer was the result of slow acid-base

reactions.

- Hence to overcome these two inherent drawbacks, some

polymerizable resin functional groups have been added to GIC

to impart additional curing process and allow the bulk of the

POLYACID – MODIFIED COMPOSITE RESINS

“COMPOMERS”

A new variety of the usual composite resins

comprising resins and inorganic filler particles is the

polyacid-modified composite resin or “compomer” which

was introduced in the early 1990s.


The compomer - combination of “comp” form composite and

“omer” from glass ionomer was introduced as a type of glass

ionomer, with claims that it offered some fluoride release as

well as improved physical properties and clinical

characteristics.


Zinc polycarboxylate:
INDICATIONS:
1. Primarily for luting permanent restorations.

2. As bases and liners.

3. Used in orthodontics for cementation of bands.

MODE OF SUPPLY:
1. Powder and liquid in bottles.
2. Powder mixed with water (water settable
cements)

COMPOSITION:
POWDER
- Zinc oxide Basic ingredient
- Magnesium oxide Principle modifier and
also aids in sintering.
- Other oxides like Small amounts
Bismuth and aluminium

- Stannous fluoride Increases strength ,
modifies setting time and
imparts anticariogenic
properties.

LIQUID:
- Liqueous solution of polyacrylic acid
OR
- Copolymer of acrylic acid with other unsaturated
carboxylic acids i .e; iticoni c, maleic, tricarboxylic
acid.

SETTING REACTION:
- When the powder and liquids are mixed, the
surface of powder particles are attacked by the acid,
releasing zinc magnesium and tin ions.
- These ions bond to the polymer chain via cross –
linked salts. www.indiandentalacademy.com

SETTING TIME: 7 to 9 minutes.

PROPERTIES:

1. MECHANICAL PROPERTIES:

- Compressive strength: 5.5 Mpa (80000Psi)
- Tensile strength : 6.2 Mpa (900 Psi)

- More soluble than zinc phosphate 0.06%

3. BIOCOMPATIBILITY:
- Pulpal response is mild. pH of liquid is 1.0 to 1.7 & the freshly mixed
cement is 3.0 to 4.0.www.indiandentalacademy.com5.0 to 6.0
After 24 hrs pH of cement is

4. ADHESION:
- Cement bond chemically with tooth structure.
The bond strength to enamel is 3.4 to 13.1Mpa & that of
dentin is 2.07Mpa.

5. THERMAL PROPERTIES:
- They are good thermal insulators.


MANIPULATION:

- Proportioning 1.5 parts of powder to 1 part of liquid by wt.

- The powder and liquid are taken on glass slab.

- The powder is incorporated into the liquid in large quantities (90%)
MIXING TIME : 30 to 40 sec.

- The cement should be used while the surface is still glossy.

- When placed in the cavity do not remove the excess, as it passes
through the rubbery stage it tends to get lifted from the cavity .

Remove the excess cement only when it has hardened


CALCIUM HYDROXIDE
CEMENT


DEFINITION:
- Calcium hydroxide cements are relatively weak
cements commonly employed as direct or indirect pulp
capping agents.

- Due to their alkaline nature they also serve as a
protective barrier against irritants from certain
restorations.


INDICATIONS:
- For direct and indirect pulp capping.
- As low strength bases beneath silicate and
composite restorations for pulp protection.
- Root canal sealer.
- In wheeping canals for exudation control.

CONTRAINDICATIONS:
- It cannot be used in a teeth with a degenerating
pulp tissues as this can lead to calcific type of
degeneration.

MODE OF SUPPLY:

1. Two paste system containing base and catalyst
pastes in collpsible tubes .

2. In powder form.

3. Light cured system


BASE PASTE

- Glycol salicylate 40% Reacts with calcium
hydroxide & zinc
oxide
- Calcium sulphate

- Titanium dioxide Inert fillers,
pigments

- Calcium tungstate Provides radio-
opacity www.indiandentalacademy.com

CATALYST PASTE

- Calcium hydroxide 50% Principal reactive
ingredients.
- Zinc oxide 10%

- Zinc stearate 0.5% Accelerator

- Ethylene toluene

- Sulfonamide 39.5% Oily compound,
acts as carrier

MANIPULATION:

Traditionally, it is formulated by
dispersing calcium hydroxide in aqueous or resin
carrier solutions to facilitate application to the
walls of cavity preperation.

The carrier evaporates and leaves a thin
layer of calcium hydroxide on the cavity walls.

It can be carried in various ways:

- The powder can be mixed with distilled water or
sterile saline to form a thick paste.

- It can also be suspended in chloroform or plasma
and can be applied with the help syringe.

- It may be applied in pure powder form also.

SETTING TIME: 2.5 TO 5.5 minutes.

Factors affecting the setting time:
- The setting of cement can be accelerated by
moisture and heat.
Conversely, the setting time will be retarded by
dryness and cold.


PROPERTIES:
1. MECHANICAL PROPERTIES-
a) Compressive strength: It has a low compressive strength ,
however it increases with time after setting.
The strength after 24 hrs ranges from 10 to 27 Mpa.

b) Tensile strength: has low tensile strength – 1.0 Mpa

c) Modulus of elasticity: 0.37Gpa.

2. THERMAL PROPERTIES:
If used in sufficiently thick layers they provide some thermal
insulation.
Thickness should not exceed 0.5 mm


Solubility is high in water – 0.4 to 7.8%
Solubility is more when exposed to phosphoric acid and
ether.
So care should be taken during acid etching and
during application of varnish in present of this cement.

a) Effect on pulp:
It is alkaline in nature due to presence of free
calcium hydroxide in set cement.
Ph 9.2- 11.7
b) Helps in formation of secondary dentin.

CAVITY VARNISH
DEFINITION:

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.


APPLICATIONS:
1.It reduces the microleakage around the margins of
newly placed amalgam restorations, thereby reducing
post operative sensitivity.

2. It reduces passage of irritants into the dentinal tubules
from the overlying restoration or base.Eg: silicate,zinc
phosphate etc..

3 In case of amalgam restorations it prevent the
penetration of corrosion products into the dentinal
tubules, thus www.indiandentalacademy.comdiscoloration.
minimizing the tooth

4. May be used as a surface coating over certain
restorations to prevent them from dehydration or
contact with oral fluids;
eg; Silicate and GIC.

5. May be applied on the surface of metallic
restorations as a temporary protection in case of
galvanic shock.

6. In cases where electrosurgery is to be done
adjacent to metallic restorations, varnish applied over
the metallic restorations serves as a temporary
electrical insulator.

COMPOSITION:
- Natural gum : Copal , rosin or synthetic resin.

- Organic solvent : alcohol , acetone or ether.

- Medicinal agents : Chlorbutanol , thymol or eugenol

Some varnishes contains fluorides.


CONTRAINDICATIONS:
a) Composite resins – The solvent in varnish may
react with or soften the resin.

b) Glass ionomer – Varnish eliminate the potential for
adhesion and the biocompatibility of the cement.

c) When therapeutic action is expected from the
overlying cement. Eg: Zinc oxide eugenol and calcium
hydroxide.


PROPERTIES:

- Varnishes neither possess a mechanical strength nor
provide thermal insulation , because of the thin film
thickness. Film thickness ranges between 2 to 40
microns.

- The solubility of dental varnishes is low , they are
virtually insoluble in distilled water.


MANIPULATION:
- The varnish may be applied by using a brush , wire
loop on a small pledget of cotton.

- Several thin layers are applied. Each layer is allowed
to dry before applying the next one.

- When the first layer dries , small pinholes
develop.These voids are filled in by the succeding
varnish applications.

The main objective is to attain a uniform and
continuous coating.

PRECAUTIONS:
- Varnish solutions should be tightly closed to
prevent loss of solvent by evaporation.

- Should be applied in a thin consistency. Viscous
varnish does not wet the cavity walls properly.

- Excess varnish should not be left on the margins of
the restorations as it prevents proper finishing of the
margins of the restorations.

- Varnish should be confined to the dentin.

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Dental cements /certified fixed orthodontic courses by Indian dental academy

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