Dental Impression materials / fixed orthodontics courses

IMPRESSIONIMPRESSION
MATERIALSMATERIALS
INDIAN DENTAL ACADEMY
Leader in continuing dental education
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INTRODUCTIONINTRODUCTION
Constructing a model or cast is anConstructing a model or cast is an
important step in numerous dentalimportant step in numerous dental
procedure. Various types of cast & modelsprocedure. Various types of cast & models
can be made from gypsum products usingcan be made from gypsum products using
an impression mold or negative likenessan impression mold or negative likeness
of a dental structure. A impression is aof a dental structure. A impression is a
negative replica of the tissue of the oralnegative replica of the tissue of the oral
cavity. It is used to register or reproducecavity. It is used to register or reproduce
the form and relation of the teeth &the form and relation of the teeth &
surrounding tissue.surrounding tissue.

HISTORYHISTORY
 1558 -Celline described a wax model to make impression in his1558 -Celline described a wax model to make impression in his
book MEMORIES.book MEMORIES.
 1700 - Mathaeus G. Purenam suggested that wax models can1700 - Mathaeus G. Purenam suggested that wax models can
be used in prosthetic work.be used in prosthetic work.
 1728 – Pieere Fauchord described various impression material1728 – Pieere Fauchord described various impression material
in his book LE CHIRURGEEN DENTISTE.in his book LE CHIRURGEEN DENTISTE.
 1756 – Persian Phillip Pfaff first use plaster models prepared1756 – Persian Phillip Pfaff first use plaster models prepared
from sectional wax impression of the mouth.from sectional wax impression of the mouth.
 1810 – R C Skinner describe about many materials and1810 – R C Skinner describe about many materials and
techniques in his first American book.techniques in his first American book.
 1928 – ADA developed specification No. 19 for impression1928 – ADA developed specification No. 19 for impression
materialmaterial

HISTORYHISTORY
 1930 – Znic Oxide Eugenol a ridged impression was introduced1930 – Znic Oxide Eugenol a ridged impression was introduced
 1930 – Polysulfide was first used as a commercial synthetic1930 – Polysulfide was first used as a commercial synthetic
rubber as a copolymer of Ethylene Chloride & sodium.rubber as a copolymer of Ethylene Chloride & sodium.
 1937 – Agar was introduced by Sears.1937 – Agar was introduced by Sears.
 1949 – Alginate was developed during World war II.1949 – Alginate was developed during World war II.
 1950 – Polysulfide was used in dentistry.1950 – Polysulfide was used in dentistry.
 1955 – Condensation Silicone was introduced in Germany.1955 – Condensation Silicone was introduced in Germany.
 1975 – Addition Silicone was introduced.1975 – Addition Silicone was introduced.
 1977 – Costell introduced Dual tray technique.1977 – Costell introduced Dual tray technique.
 1980 – A Visible light cure Polyether Urethane Dimethacrylate1980 – A Visible light cure Polyether Urethane Dimethacrylate
rubber impression material was introduced.rubber impression material was introduced.
 1996 – Blare & Wassed Considered a no. of solution used to1996 – Blare & Wassed Considered a no. of solution used to
disinfecting impression material.disinfecting impression material.

Based on the mode of
setting and elasticity
Rigidity
material
Elastic
material
Reversible Irreversible Hydrocolloid
Elastomeric
Impression
Material
Impression
compound
Impression
Plaster
ZOE
Impression
Material
Irreversible
Reversible
Condensation
silicone
Addition
silicones
Polyether
Polysulfide

BASED ON MANIPULATION
HAND MIXING
MACHANICAL
MIXING
KNEADING
CIRCULAR
MOTION
VIGOROUS
MIXING
IMPRESSION
COMPOUND POLYSULFIDES
ZOE
IMPRESSION
MATERIAL
ALGINATE

BASED ON THE TYPE OF
IMPRESION & AREA OF USED
DENTULOUS
ALGINATE
EDENTULOUS
PRIMARY SECONDARY PRIMARY
SECONDARY
AGAR
ELASTOMERS
ALGINATE
IMPRESSION
PLASTER
IMPRESSION
COMPOUND
ZOE
IMPRESSION
MATERIAL
ELASTOMERS

BASED ON THE TRAY USED
FOR IMPRESSION
SPECIAL
TRAY
STOCK
TRAY
TYPES OF
TRAY
BASED ON
PERFORATION
RIM
LOCKED
PERFORATED
WATER
COOLED
TRAY
PLASTIC
TRAY
PERFORATED
NON
PERFORATED
BASED
PLATE
RESIN
PLATE
ALGINATE AGAR-AGAR
ELASTOMER
IIMPRESSION
COMPOUNDPUTTY
WASH
IMPRESSION
ZOE
IMPRESSION
MATERIAL

IDEAL REQUIREMENTS OFIDEAL REQUIREMENTS OF
IMPRESSION MATERIALIMPRESSION MATERIAL
1. Pleasant taste & odor1. Pleasant taste & odor
2. Not contain any toxic & irritating ingredients2. Not contain any toxic & irritating ingredients
3. Adequate shelf life3. Adequate shelf life
4.Satisfactory consistency and texture4.Satisfactory consistency and texture
5.Easy to disinfect with out loss of accuracy5.Easy to disinfect with out loss of accuracy
6.Compatible with die and cast material6.Compatible with die and cast material
7.Dimentional stability7.Dimentional stability
8.Good elastic properties8.Good elastic properties
9.Easy manipulation9.Easy manipulation
10.Adequate setting characteristics10.Adequate setting characteristics
11.High degree of reproduction details11.High degree of reproduction details
12.Adequate strength12.Adequate strength
13.Should not release any gas13.Should not release any gas
14.Economical14.Economical
15.Should not be technique sensitive15.Should not be technique sensitive

HYDROCOLLOIDSHYDROCOLLOIDS
 Colloids are often classified as fourth state of matter, the ColloidalColloids are often classified as fourth state of matter, the Colloidal
state. In a solution of sugar in water, the sugar molecules arestate. In a solution of sugar in water, the sugar molecules are
uniformly dispersed in the water & there is no visible physicaluniformly dispersed in the water & there is no visible physical
separation between the solute & the solvent molecules. If sugarseparation between the solute & the solvent molecules. If sugar
molecules replaced with large & visible particles such as sand, themolecules replaced with large & visible particles such as sand, the
system is Suspension or if molecules are liquid such vegetable oil,system is Suspension or if molecules are liquid such vegetable oil,
then system is Emulsion.then system is Emulsion.
 True solution exist as a single phase. However, both the colloid &True solution exist as a single phase. However, both the colloid &
the suspension have to phase- The dispersed & Dispersion phase.the suspension have to phase- The dispersed & Dispersion phase.
In the colloid , the particles in the dispersed phase consist ofIn the colloid , the particles in the dispersed phase consist of
molecules held together either by primary or secondary force. Themolecules held together either by primary or secondary force. The
size of the particles range is 1 – 200nmsize of the particles range is 1 – 200nm

GelsGels
 Colloids with a liquid as the dispersion medium can existColloids with a liquid as the dispersion medium can exist
in two different forms known as Sol & Gel.in two different forms known as Sol & Gel.
 A sol has the appearance & many characteristic of aA sol has the appearance & many characteristic of a
various liquid.various liquid.
 A gel, on the contrary, is a semi solid & produced from aA gel, on the contrary, is a semi solid & produced from a
soldering process of gelation by the formation of fibrilssoldering process of gelation by the formation of fibrils
or chains called Micelles.or chains called Micelles.
 Gelation is the conversion of a sol to gel, & theGelation is the conversion of a sol to gel, & the
temperature at which this occurs is calledtemperature at which this occurs is called
Gelation Temperature.Gelation Temperature.

Gelation may be brought about in one of these wayGelation may be brought about in one of these way
 Lowering the temperature :-Lowering the temperature :- It is done by reducing the thermalIt is done by reducing the thermal
energy of molecules, allows inter molecular forces of attractionenergy of molecules, allows inter molecular forces of attraction
to operate more effectively. These forces are secondaryto operate more effectively. These forces are secondary
molecular forces. The bond between the fibrils are weak & theymolecular forces. The bond between the fibrils are weak & they
break at slightly elevated temperature. Gelation temp. is 37-break at slightly elevated temperature. Gelation temp. is 37-
50degree centigrade.50degree centigrade.
 Liquefaction temperatureLiquefaction temperature :- It is considerable higher than:- It is considerable higher than
gelation tamp. & this properties is known as Hytersis. Thisgelation tamp. & this properties is known as Hytersis. This
temp. is between 70 -100 degree centigrade.temp. is between 70 -100 degree centigrade.
 Chemical reactionChemical reaction :- Gelation may also induced by chemical:- Gelation may also induced by chemical
reaction, where in the dispersed phase of soil is allowed toreaction, where in the dispersed phase of soil is allowed to
react with a substance to give a different type of dispersedreact with a substance to give a different type of dispersed
phase. The process is not reversed by an increasedphase. The process is not reversed by an increased
temperature.temperature.

Type of HydrocolloidsType of Hydrocolloids
 sol can be changed to gel, but gel cant besol can be changed to gel, but gel cant be
reversed back to the solution. Eg. Alginatereversed back to the solution. Eg. Alginate
impression materialimpression material
 REVERSIBLE HYDROCOLLOIDS :-REVERSIBLE HYDROCOLLOIDS :-
Reversible hydrocolloids are thoseReversible hydrocolloids are those
IRREVERSIBLE HYDROCOLLOIDS :-IRREVERSIBLE HYDROCOLLOIDS :-
Irreversible hydrocolloids are those materialsIrreversible hydrocolloids are those materials
where the materials, where the change fromwhere the materials, where the change from
the sol to gel can be brought by lowering thethe sol to gel can be brought by lowering the
temp. of the sol & the gel can be convertedtemp. of the sol & the gel can be converted
back to sol condition by heating. Eg. Agar –back to sol condition by heating. Eg. Agar –
Agar.Agar.

ALGINATE IRREVERSIBLEALGINATE IRREVERSIBLE
HYDROCOLOOIDHYDROCOLOOID
 The word alginate comes from Algin & named by aThe word alginate comes from Algin & named by a
chemist of Scotland. It was identified as a linerchemist of Scotland. It was identified as a liner
polymer with numerous carboxyl acid group. It ispolymer with numerous carboxyl acid group. It is
called as irreversible hydrocolloids becausecalled as irreversible hydrocolloids because
gelation is induced by chemical reaction &gelation is induced by chemical reaction &
transformation is not possible. It is the most widelytransformation is not possible. It is the most widely
used dental materials. The principal factorsused dental materials. The principal factors
responsible for the success of this type ofresponsible for the success of this type of
impression materials are:-impression materials are:-
1.1. Easy to manipulateEasy to manipulate
2.2. Comfortable for the patients.Comfortable for the patients.
3.3. Relatively inexpensive.Relatively inexpensive.

compositioncomposition
1.1. Potassium or Sodium AlginatePotassium or Sodium Alginate :- 15%:- 15%
It is the chief active ingredientIt is the chief active ingredient
2.2. Calcium Sulfate :-Calcium Sulfate :- 16%16%
It is used as a reactor.It is used as a reactor.
3.3. Zinc Oxide & Diatomaccous EarthZinc Oxide & Diatomaccous Earth:-:-
Zinc oxide – 4% &Zinc oxide – 4% &
Diatomaccous earth – 60%Diatomaccous earth – 60%
4.4. Potassium Titanium FluoridePotassium Titanium Fluoride :- 3%:- 3%
5.5. Sodium PhosphateSodium Phosphate :- 2%:- 2%

Gelation ProcessGelation Process
 The typical sol-gel reaction is a soluble alginate with calcium sulfate & theThe typical sol-gel reaction is a soluble alginate with calcium sulfate & the
formation of an insoluble calcium alginate gel. Calcium sulfate reacts rapidlyformation of an insoluble calcium alginate gel. Calcium sulfate reacts rapidly
to produced the in soluble Ca alginate from the potassium or sodiumto produced the in soluble Ca alginate from the potassium or sodium
alginate in a aqueous solution. The production of calcium alginate is rapidalginate in a aqueous solution. The production of calcium alginate is rapid
that it does not allow sufficient working time. Thus third water soluble salt,that it does not allow sufficient working time. Thus third water soluble salt,
such as a trisodium phosphate, is added to the solution to prolong thesuch as a trisodium phosphate, is added to the solution to prolong the
working time. Thus the reaction between the calcium sulfate & the solubleworking time. Thus the reaction between the calcium sulfate & the soluble
alginate is prevented as long as there is uncreated trisodium phosphate.alginate is prevented as long as there is uncreated trisodium phosphate.
2Na3Po42Na3Po4 +n CaSo4+n CaSo4 →→nKaSo4nKaSo4 ++Ca. alginateCa. alginate
 When the supply of the trisodium phosphate is exhausted, the ca ions beingWhen the supply of the trisodium phosphate is exhausted, the ca ions being
to react with the potassium alginate to produce calcium alginate.to react with the potassium alginate to produce calcium alginate.
Kzn AlgKzn Alg ++n CaSo4n CaSo4→→ nn
KaSo4KaSo4 ++ Cal. alginateCal. alginate
 The added salt is retareder.The added salt is retareder.
 Controlling of gelation timeControlling of gelation time :-:-
1.1. A increase in the temp. of water used for mixing, shorten ythe working &A increase in the temp. of water used for mixing, shorten ythe working &
setting time.setting time.
2.2. The proportion of powder & water also effect the setting time.The proportion of powder & water also effect the setting time.

PROPERTIESPROPERTIES
 Alginate is of two typeAlginate is of two type
1.1. Type I :- Fast settingType I :- Fast setting
2.2. Type II :- N.ormal setting.Type II :- N.ormal setting.
According to ADA Specification No. 18 Properties Are:-According to ADA Specification No. 18 Properties Are:-
1.1. Mixing timeMixing time:- Creamy consistency come in 45 – 60 sec.:- Creamy consistency come in 45 – 60 sec.
2.2. Working timeWorking time :-:-
- Fast setting material :- 1.2 – 2 min- Fast setting material :- 1.2 – 2 min
- Normal set material :- 2 – 4.5 min- Normal set material :- 2 – 4.5 min
3.3. Setting or gelation timeSetting or gelation time :-:-
- optimum gelation time :- 3-4 min at room temp.- optimum gelation time :- 3-4 min at room temp.
- For fast setting material :- 1 -2 min- For fast setting material :- 1 -2 min
- For normal setting material :- 2 – 4.5min- For normal setting material :- 2 – 4.5min

4.4. Permanent deformationPermanent deformation :- ADA:- ADA
specification requires 97% recovery & where 3% is permanent deformation.specification requires 97% recovery & where 3% is permanent deformation.
Alginate have 98.8% recovery & 1.5 % permanent deformation.Alginate have 98.8% recovery & 1.5 % permanent deformation.
5.5. FlexibilityFlexibility :- ADA:- ADA
specification permits10 – 20% at the stress of 1000gm/ cm2. hard material havespecification permits10 – 20% at the stress of 1000gm/ cm2. hard material have
value of 5-8%.value of 5-8%.
6.6. StrengthStrength :-:-
The compressive strengthThe compressive strength :- 5000-8000gm/cm2:- 5000-8000gm/cm2
Tear strengthTear strength :- 350-700gm/cm2:- 350-700gm/cm2
7.7.viscoelasticityviscoelasticity :-:-
Usually an alginate impression materials does not adhere to the oral tissue asUsually an alginate impression materials does not adhere to the oral tissue as
strongly as some of the non aqueous elastomers, so it is easy to remove thestrongly as some of the non aqueous elastomers, so it is easy to remove the
alginate impression rapidly.alginate impression rapidly.
8.8. AccuracyAccuracy :-:-
Most alginate is not capable of reproducing the finer details that are absorbedMost alginate is not capable of reproducing the finer details that are absorbed
in impression with Agar & other elastomeric impression materialin impression with Agar & other elastomeric impression material

9.9. Dimensional effectsDimensional effects :- -The gel may loss:- -The gel may loss
water by evaporation from its surface & it shrinkswater by evaporation from its surface & it shrinks
- If the gel placed in the water it absorbed water & gels swells.- If the gel placed in the water it absorbed water & gels swells.
- Thermal change also contribute to dimensional change. The- Thermal change also contribute to dimensional change. The
alginate shrinks slightly due to different temp. between mouthalginate shrinks slightly due to different temp. between mouth
temp.(30temp.(30··c) & room temp(23c) & room temp(23··c).c).
10.10. BiocompatibilityBiocompatibility :-:-
No chemical or allergic reaction associated with alginate.No chemical or allergic reaction associated with alginate.
11.11. Self lifeSelf life :-:-
Alginate impression have shorter shelf life. Strong temp. &Alginate impression have shorter shelf life. Strong temp. &
moisture contamination are two factor which effect the self lifemoisture contamination are two factor which effect the self life
of alginate.of alginate.

MANIPULATION OF ALGINATEMANIPULATION OF ALGINATE PREPARING THE MIXPREPARING THE MIX
A measured powder is shifted into preA measured powder is shifted into pre
measured water, that has beenmeasured water, that has been
placed in a clean rubber bowl. Careplaced in a clean rubber bowl. Care
should be taken to avoid whippingshould be taken to avoid whipping
air into the mix. A vigorous figure 8air into the mix. A vigorous figure 8
motion is best, with the mix beingmotion is best, with the mix being
swiped or stropped against the sideswiped or stropped against the side
of the mixing rubber bowl withof the mixing rubber bowl with
intermittent rotation ie.180 degree ofintermittent rotation ie.180 degree of
the spatula to press out air bubbles.the spatula to press out air bubbles.
A mixing time is 45sec -1 min.A mixing time is 45sec -1 min.
A variety of mechanical devices areA variety of mechanical devices are
also available for mixing impressionalso available for mixing impression
material. There benefits arematerial. There benefits are
convenience, speed & elimination ofconvenience, speed & elimination of
human error.human error.
MAKING THE IMPRESSIONMAKING THE IMPRESSION
Before setting the impression, theBefore setting the impression, the
material should have developedmaterial should have developed
sufficient body so that it doesn’tsufficient body so that it doesn’t
flow out of the try. A perforated trayflow out of the try. A perforated tray
is generally used. If plastic try oris generally used. If plastic try or
metal rim lock try is selected a thinmetal rim lock try is selected a thin
layer of adhesive should be appliedlayer of adhesive should be applied
& allowed to dry before mixing and& allowed to dry before mixing and
loading the try. The thickness of theloading the try. The thickness of the
alginate between the tray & tissuealginate between the tray & tissue
should be at least 3mm.should be at least 3mm. www.indiandentalacademy.comwww.indiandentalacademy.com

MODIFIED ALGINATEMODIFIED ALGINATE
 Alginate modified by the incorporation of Silicone. These areAlginate modified by the incorporation of Silicone. These are
supplied as two paste which are mixed together. A colorsupplied as two paste which are mixed together. A color
contrast between the pastes enable through mixing to becontrast between the pastes enable through mixing to be
achieved, although this can be difficult because the pastes areachieved, although this can be difficult because the pastes are
of widely differing viscosity in some products.of widely differing viscosity in some products.
 To setting characteristics of the modified alginate materials areTo setting characteristics of the modified alginate materials are
similar to those of conventional alginate. They show marginallysimilar to those of conventional alginate. They show marginally
better fine details, reproduction & tear resistance but have poorbetter fine details, reproduction & tear resistance but have poor
dimensional stability. They lose the water as the same rate asdimensional stability. They lose the water as the same rate as
convention do. Cast should be poured soon after recordingconvention do. Cast should be poured soon after recording
impression if accuracy is to be obtained.impression if accuracy is to be obtained.
 This materials are considered as a hybrid of Alginate & SiliconeThis materials are considered as a hybrid of Alginate & Silicone
but there properties are close to alginate.but there properties are close to alginate.

AGAR – REVERSIBLEAGAR – REVERSIBLE
HYDROCOLLOIDSHYDROCOLLOIDS
 When agar hydrocolloids heated, they liquefyWhen agar hydrocolloids heated, they liquefy
or go into the sol state & on cooling theyor go into the sol state & on cooling they
return to the gel state. Because this processreturn to the gel state. Because this process
can be repeated, a gel of this type iscan be repeated, a gel of this type is
described as Reversible hydrocolloid. Thedescribed as Reversible hydrocolloid. The
preparation of the agar hydrocolloids forpreparation of the agar hydrocolloids for
clinical use requires care full control & yieldsclinical use requires care full control & yields
accurate impression. It has been largelyaccurate impression. It has been largely
replaced by alginate hydrocolloids & rubberreplaced by alginate hydrocolloids & rubber
impression materials.impression materials.

COMPOSITIONCOMPOSITION
1.1. BoratesBorates :- 0.2 – 0.5%:- 0.2 – 0.5%
Its works as retader.Its works as retader.
2.2. waterwater :- 85.5%:- 85.5%
It is reaction medium.It is reaction medium.
3.3. AgarAgar:- 13-17%:- 13-17%
It is main active constituent of reversible hydrocolloidIt is main active constituent of reversible hydrocolloid
impression material.impression material.
4.4. SulfatesSulfates :- 1 – 2%:- 1 – 2%
AcceleratorsAccelerators
5.5. FillersFillers :- 0.5 -1%:- 0.5 -1%
Diatomaceous earth, silica, wax rubber etc used as filler.Diatomaceous earth, silica, wax rubber etc used as filler.
6.6. BactericideBactericide :-:-
Thymol & glycerin are usedThymol & glycerin are used
7.7. Color & flavorColor & flavor

GELATION PROCESSGELATION PROCESS
 The setting of the reversible hydrocolloid is called gelation. TheThe setting of the reversible hydrocolloid is called gelation. The
reaction can be expressed a sol- gel reaction. The physicalreaction can be expressed a sol- gel reaction. The physical
changes from to gel does not return to the sol at the same temp.changes from to gel does not return to the sol at the same temp.
at which it solidified. The gel must be heated at the liquefactionat which it solidified. The gel must be heated at the liquefaction
temp. ie 70 - 100temp. ie 70 - 100··c to form sol. Sol transform into a gel at 37-50c to form sol. Sol transform into a gel at 37-50··c.c.
the exact gelation temp depended on several factor, including thethe exact gelation temp depended on several factor, including the
molecular wt. the purity of the material & the ratio of agar to othermolecular wt. the purity of the material & the ratio of agar to other
ingredients.ingredients.
 The gelation is critical. If the temp. is high, the heat from sol mayThe gelation is critical. If the temp. is high, the heat from sol may
injury to the soft tissue, or if the surface of the sol transforms to ainjury to the soft tissue, or if the surface of the sol transforms to a
gel as soon as the sol may injure the oral tissues, a high surfacegel as soon as the sol may injure the oral tissues, a high surface
stress may develop. If the gelation temp. is too far below the oralstress may develop. If the gelation temp. is too far below the oral
temp. it will be difficulty or even impossible to chill the materialtemp. it will be difficulty or even impossible to chill the material
sufficiently to obtain a firm gel to adjacent to the oral tissue. Thesufficiently to obtain a firm gel to adjacent to the oral tissue. The
temp. lag between the gelation & liquefaction temp. of the geltemp. lag between the gelation & liquefaction temp. of the gel
makes it possible to use as a dental impression material.makes it possible to use as a dental impression material.

 Gelation temperatureGelation temperature :-:-
After tempering the sol should be homogenous and should set to a gel betweenAfter tempering the sol should be homogenous and should set to a gel between
37 – 50 degrees centigrade37 – 50 degrees centigrade when cooled.when cooled.
 Viscoelastic propertiesViscoelastic properties :-:-
It demonstrate the necessity of deforming the impression rapidly when itIt demonstrate the necessity of deforming the impression rapidly when it
removed from the mouth which reduce the amount of the permanentremoved from the mouth which reduce the amount of the permanent
deformation. The elastic recovery of the hydrocolloid is never complete & itdeformation. The elastic recovery of the hydrocolloid is never complete & it
does not return entirely to its original dimension after deformation. The amountdoes not return entirely to its original dimension after deformation. The amount
of permanent deformation in clinical is negligible, provided that :-of permanent deformation in clinical is negligible, provided that :-
a) The material has adequately gelled.a) The material has adequately gelled.
b) The impression has been removed rapidly.b) The impression has been removed rapidly.
c) The under cuts present in the cavity preparation are minimal.c) The under cuts present in the cavity preparation are minimal.
 Permanent deformationPermanent deformation :-:-
The ADA specification requires that the permanent deformation should be lessThe ADA specification requires that the permanent deformation should be less
than 1.5% after the material compressed 10% for 30sec. This impressionthan 1.5% after the material compressed 10% for 30sec. This impression
material readily meet this requirement with the value of about 1%.material readily meet this requirement with the value of about 1%.
 Distortion during gelationDistortion during gelation :-:-
If the material is held rigidly to the tray , then the impression material shrinksIf the material is held rigidly to the tray , then the impression material shrinks
toward the center of its mass. Rapid cooling may cause a concentration oftoward the center of its mass. Rapid cooling may cause a concentration of
stress near the tray where gelation first take place.stress near the tray where gelation first take place.

 FlexibilityFlexibility :-:-
The ADA specification requirement for flexibility allows a rangeThe ADA specification requirement for flexibility allows a range
of 4-14% & most agar materials meet this requirement.of 4-14% & most agar materials meet this requirement.
 StrengthStrength :-:-
1.1. The compressive strength of Agar impression material isThe compressive strength of Agar impression material is
8000gm/cm28000gm/cm2
2.2. The tear strength of Agar is 7000gm/cm2The tear strength of Agar is 7000gm/cm2
 FlowFlow :-:-
Agar is sufficiently fluid to allow detailed reproduction of hardAgar is sufficiently fluid to allow detailed reproduction of hard
& soft tissue.& soft tissue.
 Compatibility with gypsumCompatibility with gypsum :-:-
Not all the agar impression materials are equally compatibleNot all the agar impression materials are equally compatible
with all gypsum products. The impression should be washedwith all gypsum products. The impression should be washed
of saliva & any trace of blood, which retarded the setting ofof saliva & any trace of blood, which retarded the setting of
gypsum.gypsum.

Manipulation of agar impression:Manipulation of agar impression:
The use of agar hydrocolloid involveThe use of agar hydrocolloid involve
special equipment called conditioning unitspecial equipment called conditioning unit
for agar. The hydrocolloid is usuallyfor agar. The hydrocolloid is usually
supplied In two forms: syringe and traysupplied In two forms: syringe and tray
materials. The only difference between thematerials. The only difference between the
materials is the color and the greatermaterials is the color and the greater
fluidity of the syringe material.fluidity of the syringe material.

Impression tray:Impression tray:
It is rim locked trays with water circulatingIt is rim locked trays with water circulating
device. This types of trays should allow adevice. This types of trays should allow a
space of 3mm occlusally and laterally andspace of 3mm occlusally and laterally and
extend distally to cover all the teeth. Afterextend distally to cover all the teeth. After
the tray has been properly positioned,the tray has been properly positioned,
water is circulated at 13 degrees throughwater is circulated at 13 degrees through
the tray until gelation occurs.the tray until gelation occurs.

Preparation of material:Preparation of material:
Proper equipment of liquefying andProper equipment of liquefying and
storing the agar impressionstoring the agar impression
material is essential.material is essential.
At first reverse the hydrocolloid gelAt first reverse the hydrocolloid gel
to the sol stage. Boiling water is ato the sol stage. Boiling water is a
convenient way of liquefying theconvenient way of liquefying the
material. The material must bematerial. The material must be
held at this temperature for aheld at this temperature for a
minimum of 10mins. Propyleneminimum of 10mins. Propylene
glycol can be added to the waterglycol can be added to the water
to obtain 100 degrees. After it hasto obtain 100 degrees. After it has
been liquefied, the material mustbeen liquefied, the material must
be stored in the tray. The materialbe stored in the tray. The material
can be stored for several days.can be stored for several days.
Usually, there are threeUsually, there are three
compartments in the conditioningcompartments in the conditioning
unit, making it possible to liquefy,unit, making it possible to liquefy,
store and temper the material.store and temper the material.

Conditioning and tempering:Conditioning and tempering:
Because 55 degree is the maximum tolerableBecause 55 degree is the maximum tolerable
temperature, the storage temperature of 65temperature, the storage temperature of 65
degrees would be too hot for the oral tissues,degrees would be too hot for the oral tissues,
especially given the bulk of the tray material.especially given the bulk of the tray material.
Therefore, the material that is used to fill the trayTherefore, the material that is used to fill the tray
must be cooled and tempered. Eliminating themust be cooled and tempered. Eliminating the
effect of imbibition is the purpose of placing theeffect of imbibition is the purpose of placing the
gauze pad over the tempering tray materials.gauze pad over the tempering tray materials.
When the tray material is placed into theWhen the tray material is placed into the
tempering bath, the gauze is removed and thetempering bath, the gauze is removed and the
contaminating surface layer of material clings tocontaminating surface layer of material clings to
the gauze and is removed as well.the gauze and is removed as well.

Making the impression:Making the impression:
The syringe material is taken directly from theThe syringe material is taken directly from the
storage compartment and applied to thestorage compartment and applied to the
prepared cavities. It is first applied to the base ofprepared cavities. It is first applied to the base of
the preparation and then the reminder of thethe preparation and then the reminder of the
tooth is covered. By the time the cavitytooth is covered. By the time the cavity
preparation and adjoining teeth have beenpreparation and adjoining teeth have been
covered, the tray material has been properlycovered, the tray material has been properly
tempered and is now ready to be placedtempered and is now ready to be placed
immediately in the mouth to form the bulk ofimmediately in the mouth to form the bulk of
impression. Gelation is accelerated byimpression. Gelation is accelerated by
circulating cool water, approximately, 18 – 21circulating cool water, approximately, 18 – 21
degrees through the tray for 3 – 5 minutesdegrees through the tray for 3 – 5 minutes..

Disinfection hydrocolloidDisinfection hydrocolloid
impression:impression:
.. As the hydrocolloid impression material must be pouredAs the hydrocolloid impression material must be poured
within short time after removal from the mouth. Thewithin short time after removal from the mouth. The
disinfection procedure should be relatively rapid todisinfection procedure should be relatively rapid to
prevent the dimensional change. Most manufacturersprevent the dimensional change. Most manufacturers
recommended a specific disinfectant. The agent may berecommended a specific disinfectant. The agent may be
iodophor, bleach or glutaraldehyde. The distortion isiodophor, bleach or glutaraldehyde. The distortion is
minimal if the recommended immersion time is followedminimal if the recommended immersion time is followed
and if the impression is poured properly. The irreversibleand if the impression is poured properly. The irreversible
hydrocolloid may be disinfected by 10 minute immersionhydrocolloid may be disinfected by 10 minute immersion
in/or spraying with the antimicrobial agent such as NaOClin/or spraying with the antimicrobial agent such as NaOCl
and glutaraldehyde without sufficient dimensional change.and glutaraldehyde without sufficient dimensional change.
The current protocol for disinfecting hydrocolloidThe current protocol for disinfecting hydrocolloid
impression is to use household bleach, iodophor, andimpression is to use household bleach, iodophor, and
synthetic phenols as disinfectants. After the immersion, itsynthetic phenols as disinfectants. After the immersion, it
is thoroughly rinsed . The disinfectant is sprayed liberallyis thoroughly rinsed . The disinfectant is sprayed liberally
o the exposed surface. The immersion should not beo the exposed surface. The immersion should not be
submerged or shocked in the disinfectant solution.submerged or shocked in the disinfectant solution.www.indiandentalacademy.comwww.indiandentalacademy.com

ADVANTAGES & DISADVANTAGEADVANTAGES & DISADVANTAGE
ImpressionImpression
materialsmaterials
Brand nameBrand name AdvantagesAdvantages DisadvantageDisadvantage
ReversibleReversible
hydrocolloidhydrocolloid
AgarAgar
1. Acculoid /1. Acculoid /
CartriloidsCartriloids
(Van R)(Van R)
2. Indentic2. Indentic
(cadco)(cadco)
1. Moist field ok1. Moist field ok
2. Accurate2. Accurate
replicareplica
3. Hydrophilic3. Hydrophilic
4.low cost4.low cost
5. long self life5. long self life
1. Require1. Require
specialspecial
equipmentequipment
2. thermal2. thermal
discomfortdiscomfort
3. Tears easily3. Tears easily
4. Must be4. Must be
pouredpoured
immediatelyimmediately
IrreversibleIrreversible
hydrocolloidhydrocolloid
AlginateAlginate
1. Coe Alginate1. Coe Alginate
(GC America)(GC America)
2. Integra2. Integra
(Kerr) 3. Super(Kerr) 3. Super
gel (Bosworth)gel (Bosworth)
1.1. Moist fieldMoist field
okok
2. Clean replica2. Clean replica
4. Low cost4. Low cost
5 Patient5 Patient
acceptanceacceptance
1.1. NotNot
accurate /accurate /
roughrough
reproductionreproduction
2. Tear easily2. Tear easily
3. Must poured3. Must poured
immediatelyimmediatelywww.indiandentalacademy.comwww.indiandentalacademy.com

TYPES OF FALIURESTYPES OF FALIURES
1.1.DistortionDistortion :- due to:- due to
 Delayed pouring of impressionDelayed pouring of impression
 Movement of tray during settingMovement of tray during setting
 Removal from mouth too earlyRemoval from mouth too early
2.Grainy impression2.Grainy impression :- due to:- due to
 Inadequate mixingInadequate mixing
 Prolonged mixingProlonged mixing
 Less water in mixLess water in mix
3.3. TearingTearing :- due to:- due to
 Inadequate bulkInadequate bulk
 Moisture contaminationMoisture contamination
 Removal from mouth too earlyRemoval from mouth too early
 Prolonged mixingProlonged mixing
4.4. BubblesBubbles :- due to:- due to
 Early gelation, preventing flowEarly gelation, preventing flow
 Air incorporated during mixingAir incorporated during mixing
5.5. Irregular voidsIrregular voids :- due to:- due to
 Excess moisture &debris on tissueExcess moisture &debris on tissue

INELASTIC OR RIGIEDINELASTIC OR RIGIED
IMPRESSION MATERIALIMPRESSION MATERIAL
In elastic impression materials exhibit anIn elastic impression materials exhibit an
insignificant of elastic deformation wheninsignificant of elastic deformation when
subjected to bonding or tensile strength. Theysubjected to bonding or tensile strength. They
tend to fracture without exhibiting any plastictend to fracture without exhibiting any plastic
deformation if the stress applied pressuredeformation if the stress applied pressure
exceeds there tensile, shear or compressiveexceeds there tensile, shear or compressive
strength value. These material includestrength value. These material include
Impression compound, Impression plaster &Impression compound, Impression plaster &
ZOE impression paste. Because of theseZOE impression paste. Because of these
materials inability to sustain a substantialmaterials inability to sustain a substantial
amount of elastic deformation without fracture,amount of elastic deformation without fracture,
there use in dental impression making is limited.there use in dental impression making is limited.

Impression compoundImpression compound
 Impression compound is aImpression compound is a
thermoplastic material. When itsthermoplastic material. When its
used for edentulous impression, itused for edentulous impression, it
is also called modeling plastic. Itsis also called modeling plastic. Its
classified as a rigid, reversibleclassified as a rigid, reversible
impression material which sets byimpression material which sets by
physical change. It usually comesphysical change. It usually comes
in the form cakes & sticks.in the form cakes & sticks.
 CLASSIFICATIONCLASSIFICATION
According to ADA specification no.3According to ADA specification no.3
dental impression compounds aredental impression compounds are
classified into two types :-classified into two types :-
1.1. Type I Impression compoundType I Impression compound :- It:- It
is used for making edentulousis used for making edentulous
impression. It is also used to makeimpression. It is also used to make
impression of single tooth inimpression of single tooth in
operative dentistry.operative dentistry.
2.2. Type II Tray compoundType II Tray compound :- It is a try:- It is a try
compound which is used tocompound which is used to
prepare a try for making aprepare a try for making a
impression.impression.

REQUIREMENT OF IDEALREQUIREMENT OF IDEAL
IMPRESSION COMPOUNDIMPRESSION COMPOUND
1.1. Solidified or harden at or little above mouth temp.Solidified or harden at or little above mouth temp.
2.2. Not injurious or harmful to oral tissue.Not injurious or harmful to oral tissue.
3.3. Not contain irritating or toxic ingredient.Not contain irritating or toxic ingredient.
4.4. Harden uniformly when cooled without distortion.Harden uniformly when cooled without distortion.
5.5. Reproduce fine detail.Reproduce fine detail.
6.6. Cohesive but not adhesive.Cohesive but not adhesive.
7.7. Should not undergo permanent deformation.Should not undergo permanent deformation.
8.8. Good dimensional stabilityGood dimensional stability
9.9. Smooth glossy surfaceSmooth glossy surface
10.10. After hardening should withstand trimming with sharpAfter hardening should withstand trimming with sharp
knife chippingknife chipping

COPOSITIONCOPOSITION
1.1. Thermoplastic materialThermoplastic material:- 50%:- 50%
Natural or synthetic resins & waxes areNatural or synthetic resins & waxes are
usedused
2.2. FillerFiller :- 47%:- 47%
These are talcThese are talc
3.3. LubricantLubricant :- 3%:- 3%
Stearic acid usedStearic acid used

1.1. Thermal propertiesThermal properties :-:-
It is very low. The coefficient of contraction of impressionIt is very low. The coefficient of contraction of impression
compound is from mouth temp. to room temp. is 0.3%compound is from mouth temp. to room temp. is 0.3%
2.2. FlowFlow :-:-
According to ADA specification no. 3 flow should be:-According to ADA specification no. 3 flow should be:-
Type I :- Not more than 6% at 37degreeType I :- Not more than 6% at 37degree
Not less than 80% & not more thanNot less than 80% & not more than
85% at 45degree.85% at 45degree.
Type II :- Not more than 2% at 37degreeType II :- Not more than 2% at 37degree
Not less than 70% & not more than 85% at 45degreeNot less than 70% & not more than 85% at 45degree
3.3. DistortionDistortion :-:-
The release of strains is avoidable, the safest procedure toThe release of strains is avoidable, the safest procedure to
prevent distortion is to pour the cast immediately or at least in 1prevent distortion is to pour the cast immediately or at least in 1
hrs.hrs.
4.4. Dimensionally stabilityDimensionally stability :-:-
Relaxation of the impression compound can occur in aRelaxation of the impression compound can occur in a
comparatively short period of time, especial with increase in temp.comparatively short period of time, especial with increase in temp.
5.5. ViscosityViscosity :-:-
The most viscose material. 70 time more than impression & 100The most viscose material. 70 time more than impression & 100
time more than light body elastomers.time more than light body elastomers.

DISINFECTIONDISINFECTION
 The recommended disinfectant solution for compound is 2% alkalineThe recommended disinfectant solution for compound is 2% alkaline
glutaraldehyde solution. The impression should immersed in this solution forglutaraldehyde solution. The impression should immersed in this solution for
the require amount of time, rinsed & poured immediately.the require amount of time, rinsed & poured immediately.
MANIPULATIONMANIPULATION
Small amount of compound is soften over the flame. When a direct flame isSmall amount of compound is soften over the flame. When a direct flame is
used, the compound should not allowed to boil or ignite, other wise theused, the compound should not allowed to boil or ignite, other wise the
plasticizers are volatilized.plasticizers are volatilized.
 When a large amount of compound is to be softened, it is difficult to heatWhen a large amount of compound is to be softened, it is difficult to heat
uniformly. The compound is softened in a thermostatically controlled wateruniformly. The compound is softened in a thermostatically controlled water
bath. After the compound is removed from the water, it is usually kneadedbath. After the compound is removed from the water, it is usually kneaded
with the finger to obtain uniform plasticity throughout the mass.with the finger to obtain uniform plasticity throughout the mass.
 The safest method for removing the cast from is to immerse it in warm waterThe safest method for removing the cast from is to immerse it in warm water
until the compound softens sufficiently to permit easy separation from cast.until the compound softens sufficiently to permit easy separation from cast.

ZINC OXIED EUGENOL IMPRESSIONZINC OXIED EUGENOL IMPRESSION
PASTEPASTE
 Under proper condition, the reaction betweenUnder proper condition, the reaction between
zinc oxide & eugenol yields a relatively hardzinc oxide & eugenol yields a relatively hard
mass that possesses certain medicinalmass that possesses certain medicinal
advantage, as well as mechanical propertiesadvantage, as well as mechanical properties
benefits, for some dental operation. ZOEbenefits, for some dental operation. ZOE
impression paste produces a rigid impressionimpression paste produces a rigid impression
with a high degree of accuracy & goodwith a high degree of accuracy & good
reproduction of surface detail.reproduction of surface detail.
 Types of paste:-Types of paste:-
1.1. Type I:- hardType I:- hard
2.2. Type II :- softType II :- soft

COPOSITIONCOPOSITION
Usually its come in two tube in paste formUsually its come in two tube in paste form
 Base pasteBase paste :- its in white in color:- its in white in color
1.1. Zinc oxideZinc oxide :- 87%:- 87%
2.2. Fixed vegetable or mineral oilFixed vegetable or mineral oil :- 13%:- 13%
 Accelerator pasteAccelerator paste:- it is in red color:- it is in red color
1.1. Oil of clovesOil of cloves:- 12%:- 12%
contains 70 – 85% eugenol oilcontains 70 – 85% eugenol oil
2.2. Gum or polymerized rosinGum or polymerized rosin :- 50%:- 50%
3.3. FillerFiller :- 20%:- 20%
its silica typeits silica type
4.4. LanolinLanolin :- 3%:- 3%
5.5. Resinous balsamResinous balsam:- 10%:- 10%
6.6. Accelerator solutionAccelerator solution:- 5%:- 5%

MANIPULATIONMANIPULATION
 The mixing of two paste isThe mixing of two paste is
generally accomplished on angenerally accomplished on an
oil impervious paper or glassoil impervious paper or glass
slab. The proper proportion ofslab. The proper proportion of
the two pastes is generallythe two pastes is generally
obtained by squeezing twoobtained by squeezing two
strips of paste of the samestrips of paste of the same
length, one from each tube onlength, one from each tube on
the mixing slab. A flexiblethe mixing slab. A flexible
stainless steal spatula isstainless steal spatula is
typically used for the mixingtypically used for the mixing
procedure. The two strip ofprocedure. The two strip of
contrasting color are combinedcontrasting color are combined
with the first stroke of thewith the first stroke of the
spatula & the mixing isspatula & the mixing is
continued for approx 1 min orcontinued for approx 1 min or
uniform color is obtained.uniform color is obtained.

1.1. Setting timeSetting time:-:-
Once the material in a plastic condition is carried to the mouth, only theOnce the material in a plastic condition is carried to the mouth, only the
minimum time should elapse before the impression harden.minimum time should elapse before the impression harden.
 Initial setting timeInitial setting time :-:-
Type I :- 3 – 6minType I :- 3 – 6min
type II :- 3 – 6mintype II :- 3 – 6min
 Final setting timeFinal setting time :-:-
Type I :- 10minType I :- 10min
Type II :- 15minType II :- 15min
This setting time is at 23 degreeThis setting time is at 23 degree ± 2degree & 50% humidity.± 2degree & 50% humidity.
2.2. Consistency & flowConsistency & flow :-:-
According to ADA specification no. 16 its spread –According to ADA specification no. 16 its spread –
Type IType I :- 30 – 50mm:- 30 – 50mm
Type II :- 20 45 mmType II :- 20 45 mm
3.3. Rigidity & strengthRigidity & strength :-:-
The compressive strength of ZOE paste is 7Mpa 2 hrs after mixingThe compressive strength of ZOE paste is 7Mpa 2 hrs after mixing
4.4. Dimensional stabilityDimensional stability :-:-
it is quit satisfactory. Shrinkage is less than 0.1%.it is quit satisfactory. Shrinkage is less than 0.1%.

DISINFECTIONDISINFECTION
The recommended disinfectant solution forThe recommended disinfectant solution for
ZOE impression paste is 2% alkalineZOE impression paste is 2% alkaline
glutaraldehyde solution. The impressionglutaraldehyde solution. The impression
should immersed in this solution forshould immersed in this solution for
required amount of time, rinsed & pouredrequired amount of time, rinsed & poured
immediately.immediately.

NON EUGENOL PASTENON EUGENOL PASTE
One of the chief disadvantage of ZOE paste isOne of the chief disadvantage of ZOE paste is
the possible burning sensation caused by thethe possible burning sensation caused by the
eugenol that leaches out & contact the softeugenol that leaches out & contact the soft
tissue. Zinc oxide can react with varioustissue. Zinc oxide can react with various
carboxylic acid & form ZOE like structure.carboxylic acid & form ZOE like structure.
Orthoethoxy benzoic acid, commonlyOrthoethoxy benzoic acid, commonly
abbreviated EBA, is the valuable substitute forabbreviated EBA, is the valuable substitute for
eugenol in this regard. The reaction is welleugenol in this regard. The reaction is well
understood & its not greatly affected by temp. orunderstood & its not greatly affected by temp. or
humidity. Bactericidal agents & otherhumidity. Bactericidal agents & other
medicaments can be incorporated withoutmedicaments can be incorporated without
interfering the reaction.interfering the reaction.

BITE REGISTRATION PASTEBITE REGISTRATION PASTE
The materials used for recording theThe materials used for recording the
occlusal relationship between natural &occlusal relationship between natural &
artificial teeth including impression plaster,artificial teeth including impression plaster,
compound, wax- ZOE paste, often usedcompound, wax- ZOE paste, often used
as recording materials in the constructionas recording materials in the construction
of complete dentures, & fixed or removalof complete dentures, & fixed or removal
partial denture. The ZOE paste offerspartial denture. The ZOE paste offers
almost no resistance to closing of thealmost no resistance to closing of the
mandible. Thus allowing a more accuratemandible. Thus allowing a more accurate
interocclusion recording to be formed.interocclusion recording to be formed.

ELASTOMERIC IMPRESSIONELASTOMERIC IMPRESSION
MATERIALMATERIAL
 Elastomers refer to a group of rubbery polymers, which are either chemically orElastomers refer to a group of rubbery polymers, which are either chemically or
physically cross linked. They can be easily stretched & rapidly recover theirphysically cross linked. They can be easily stretched & rapidly recover their
original dimensions when the applied stress is removed. Chemically there are fouroriginal dimensions when the applied stress is removed. Chemically there are four
types of elastomers used as Impression material-types of elastomers used as Impression material-
1.1. PolysulfidePolysulfide
2.2. Condensation polymerizing siliconesCondensation polymerizing silicones
3.3. Addition polymerizing siliconesAddition polymerizing silicones
4.4. PolyetherPolyether
 The current ADA specification no. 19 recognizes three types of elatomericThe current ADA specification no. 19 recognizes three types of elatomeric
impression materials. Classification is based on selected elastic properties & theimpression materials. Classification is based on selected elastic properties & the
dimensional change of the set materials rather than there chemistry. Each type isdimensional change of the set materials rather than there chemistry. Each type is
further divided into four viscosity classes :-further divided into four viscosity classes :-
1.1. Light bodyLight body
2.2. Medium or regular bodyMedium or regular body
3.3. Heavy bodyHeavy body
4.4. puttyputty

Properties of ElastomericProperties of Elastomeric
Impression MaterialImpression Material
1.1. Excellent reproduction ability of surface detailExcellent reproduction ability of surface detail
2.2. HydrophobicHydrophobic
3.3. Elastic properties is good but elastic recovery is not complete.Elastic properties is good but elastic recovery is not complete.
4.4. Coefficient of thermal expansion is high.Coefficient of thermal expansion is high.
5.5. Dimensional changes occurs due to:-Dimensional changes occurs due to:-
 Curing shrinkageCuring shrinkage
 Absorb water & loses soluble plasticizers causes change.Absorb water & loses soluble plasticizers causes change.
 Due to thermal contraction.Due to thermal contraction.
 Incomplete elastic recovery.Incomplete elastic recovery.
 When filler content is increased, the polymer content is less &When filler content is increased, the polymer content is less &
shrinkage is less.shrinkage is less.
 Uniform thickness of material gives more accurate impression asUniform thickness of material gives more accurate impression as
the shrinkage is uniform.the shrinkage is uniform.
 Good adhesion to the tray with the help of adhesives.Good adhesion to the tray with the help of adhesives.

POLYSULFIED IMPRESSIONPOLYSULFIED IMPRESSION
 This was the first elastomeric impressionThis was the first elastomeric impression
material to be introduced. It is also know asmaterial to be introduced. It is also know as
MERCAPTAN or THIOKOL.MERCAPTAN or THIOKOL.
 MODE OF SUPPLYMODE OF SUPPLY
it is supplied in collapsible tube as base &it is supplied in collapsible tube as base &
accelerator in paste form. Base in white coloraccelerator in paste form. Base in white color
& accelerator is in gray color. It is available in& accelerator is in gray color. It is available in
three viscosities:-three viscosities:-
1.1. Light bodiedLight bodied
2.2. Medium bodiedMedium bodied
3.3. Heavy bodiedHeavy bodied

 BASE PASTEBASE PASTE
1.1. Liquid polysulfide polymerLiquid polysulfide polymer:-80:-80
-85%-85%
2.2. Inert fillerInert filler :- 16 – 18%:- 16 – 18%
TitaniumTitanium
dioxide, zinc sulfate, copperdioxide, zinc sulfate, copper
carbonate use as a fillercarbonate use as a filler
3. Plasticize3. Plasticize
 ACCELERATOR orACCELERATOR or
CATALYST PASTECATALYST PASTE
1.1. Lead dioxideLead dioxide:- 60 – 68%:- 60 – 68%
2.2. SulfurSulfur :- 3%:- 3%
3.3. Inert oilInert oil:- 30 -35%:- 30 -35%
Normally itNormally it
is Paraffinic type or di-n-is Paraffinic type or di-n-
butyl phthalate.butyl phthalate.

CHEMISTRYCHEMISTRY
 The main component of polysulfide material is aThe main component of polysulfide material is a
multifunctional mercaptan or polysulfide polymer. Thismultifunctional mercaptan or polysulfide polymer. This
liner polymer contains approximately 1 mole percent ofliner polymer contains approximately 1 mole percent of
pendent- Thiol group(-SH gp). A oxidizing agent such aspendent- Thiol group(-SH gp). A oxidizing agent such as
lead dioxide is used to initiate polymerization throughlead dioxide is used to initiate polymerization through
chain lengthening between terminal – SH gp. & crosschain lengthening between terminal – SH gp. & cross
linked between the pendant – SH gp. Lead dioxide is thelinked between the pendant – SH gp. Lead dioxide is the
component that gives polysulfide. The reaction starts atcomponent that gives polysulfide. The reaction starts at
the beginning of mixing & reaches its maximum ratethe beginning of mixing & reaches its maximum rate
soon after the spatulation is completed. During the finalsoon after the spatulation is completed. During the final
set, a material of adequate elasticity & strength isset, a material of adequate elasticity & strength is
formed. Moisture & temp. have a significant effect on theformed. Moisture & temp. have a significant effect on the
course of the reaction.course of the reaction.

1.1. Setting timeSetting time:-:-
16 min at 23 degree16 min at 23 degree
12.5 min at 37 degree12.5 min at 37 degree
6 min at 23 degree6 min at 23 degree
4.3 min at 37 degree4.3 min at 37 degree
3.3. Taste & odorTaste & odor :-:-
Taste less with sulphours odor.Taste less with sulphours odor.
4.4. Excellent quality of reproduction of surface details.Excellent quality of reproduction of surface details.
5.5. Dimensional stabilityDimensional stability:-:-
The curing shrinkage is high. It is 0.45%The curing shrinkage is high. It is 0.45%
The material has highest permanent deformationThe material has highest permanent deformation
among the elastomers & it is 3 – 5%among the elastomers & it is 3 – 5%

6.6. Tear strengthTear strength :-:-
it is high. It is 2500 – 7000M/nit is high. It is 2500 – 7000M/n
7.7. Good flexibility of 7%Good flexibility of 7%
8.8. HydrophobicHydrophobic
9.9. Shelf life is 2 years.Shelf life is 2 years.
the use of lead compound in polysulfide material hasthe use of lead compound in polysulfide material has
been questioned because of the know toxic effect ofbeen questioned because of the know toxic effect of
lead. It is unlikely that the lead contained in thislead. It is unlikely that the lead contained in this
material is able to exert a harmful effect as the materialmaterial is able to exert a harmful effect as the material
is in the patient mouth for only a few min.is in the patient mouth for only a few min.
11.11. Coefficient of thermal expansionCoefficient of thermal expansion :-:-
is 270is 270 x 10-6 degree centigrade -1x 10-6 degree centigrade -1
12.12. Stress relaxation at 2 min after setting time is 45%Stress relaxation at 2 min after setting time is 45%

SILICONE RUBBER IMPRESIONSILICONE RUBBER IMPRESION
MATERIALMATERIAL
 These materials were developed to overThese materials were developed to over
come some of disadvantages ofcome some of disadvantages of
Polysulfide.Polysulfide.
 These are of two type:-These are of two type:-
1.1. Condensation siliconeCondensation silicone
2.2. Addition siliconeAddition silicone

CONDENSATION SILICONECONDENSATION SILICONE
 This was the earlier of the two silicone impressionThis was the earlier of the two silicone impression
material. It is also known as convention silicone.material. It is also known as convention silicone.
 Mode of supply :-Mode of supply :-
This material is available as base & catalyst in paste form.This material is available as base & catalyst in paste form.
Catalyst can also be supplied in liquid form. It isCatalyst can also be supplied in liquid form. It is
available in three viscosities –available in three viscosities –
1. Light bodies1. Light bodies
2. Medium bodies2. Medium bodies
3. Putty3. Putty
 Commercial name :- Sil21 & ColtexCommercial name :- Sil21 & Coltex

 BASEBASE
1.1. Hydroxyl terminated polydimethylHydroxyl terminated polydimethyl
siloxanesiloxane :-:-
2.2. Inert fillerInert filler :-:-
Silica is use as a fillerSilica is use as a filler
 ACCELERATOR OR CATALYST PASTEACCELERATOR OR CATALYST PASTE
1.1. Ortho ethyl silicateOrtho ethyl silicate
2.2. Stannous octoateStannous octoate

CHEMISTRYCHEMISTRY
 It is a condensation reaction. PolymerizationIt is a condensation reaction. Polymerization
occurs as a result of cross linkage between theoccurs as a result of cross linkage between the
orthoethyl silicate & the terminal hydroxy grouporthoethyl silicate & the terminal hydroxy group
of the dimethyl silicone, to form a threeof the dimethyl silicone, to form a three
dimensional network. Stannous octoate act as adimensional network. Stannous octoate act as a
catalyst.catalyst.
 The ethyl alcohol formed as a by productThe ethyl alcohol formed as a by product
evaporate gradually from the set rubber leadingevaporate gradually from the set rubber leading
to shrinkage.to shrinkage.

1.1. Working timeWorking time:-:-
it is 3.3 min at 23 degreeit is 3.3 min at 23 degree
it is 2.5 min at 37degreeit is 2.5 min at 37degree
2.2. Setting timeSetting time :-:-
it is 11 min at 23degreeit is 11 min at 23degree
3.3. Odour less, taste less with wide variety of colorOdour less, taste less with wide variety of color
4.4. Excellent quality of reproduction of surfaceExcellent quality of reproduction of surface
details.details.
It is less due to high curing shrinkage. CuringIt is less due to high curing shrinkage. Curing
shrinkage is 0.4 – 0.6% Permanentshrinkage is 0.4 – 0.6% Permanent
deformation is high with 1 – 3%deformation is high with 1 – 3%www.indiandentalacademy.comwww.indiandentalacademy.com

2300 – 2600N/m2300 – 2600N/m
7. More stiffer & harder than the polysulfide7. More stiffer & harder than the polysulfide
8. Hydrophobic8. Hydrophobic
Essentially considered nontoxic, despite the fact thatEssentially considered nontoxic, despite the fact that
they contain a heavy metal catalyst. The materials arethey contain a heavy metal catalyst. The materials are
hydrophobic & are in the patient mouth for only a fewhydrophobic & are in the patient mouth for only a few
min.min.
190190x10-6 degree centigrade -1x10-6 degree centigrade -1
11. Loss of weight of this material at 24 hrs is 0.9%11. Loss of weight of this material at 24 hrs is 0.9%
12. shelf life is 12 month.12. shelf life is 12 month.

ADDITIONADDITION SILICONESILICONE
 It has a better propertiesIt has a better properties
than condensation silicones.than condensation silicones.
It is also know as POLYIt is also know as POLY
VINYL SILOXANE.VINYL SILOXANE.
Addition silicone materialsAddition silicone materials
are available as Base &are available as Base &
Catalyst in paste form. It isCatalyst in paste form. It is
available in four viscosities:-available in four viscosities:-
4.4. PuttyPutty
 Commercial names:-Commercial names:-
1.1. ReprosilReprosil
2.2. ProvilProvil
3.3. presidentpresident

 BASEBASE
1.1. Poly methyl hydrogen siloxanePoly methyl hydrogen siloxane
2.2. Other siloxane prepolymersOther siloxane prepolymers
3.3. FillersFillers
 CATALYSTCATALYST
1.1. Divinyl polysiloxaneDivinyl polysiloxane
2.2. Other siloxane prepolymersOther siloxane prepolymers
3.3. Platinum saltPlatinum salt
4.4. Palladium or hydrogen absorberPalladium or hydrogen absorber
5.5. RetarderRetarder
6.6. FilleFille

CHEMIETRYCHEMIETRY
 It is an addition reaction. In this case theIt is an addition reaction. In this case the
base polymer is terminated with Vinylbase polymer is terminated with Vinyl
group & is cross linked with silane. Thisgroup & is cross linked with silane. This
reaction is activated by the platinum salt.reaction is activated by the platinum salt.
 There is no by product as long as there isThere is no by product as long as there is
proper balance between the Vinyl siloxaneproper balance between the Vinyl siloxane
& the silane siloxane. If proper balance is& the silane siloxane. If proper balance is
not there hydrogen is produced causingnot there hydrogen is produced causing
air bubbles in the stone modelsair bubbles in the stone models..

it is 1.8min at 37degreeit is 1.8min at 37degree
it is 5.9min at 37degreeit is 5.9min at 37degree
3.3. Reproduce excellent surface detailsReproduce excellent surface details
Best in all elastomers. Low curingBest in all elastomers. Low curing
shrinkage with 0.17% & lowest permanentshrinkage with 0.17% & lowest permanent
deformation of 0.05 – 0.3%deformation of 0.05 – 0.3%
It is 1500 – 4300 N/mIt is 1500 – 4300 N/m

6. Hydrophobic6. Hydrophobic
7. Low flexibility & is harder than polysulfide.7. Low flexibility & is harder than polysulfide.
190190x10-6 degree-1x10-6 degree-1
9. Weight loss of material at 24hrs is 0.05%9. Weight loss of material at 24hrs is 0.05%
10. Shelf life is 1 – 2 year10. Shelf life is 1 – 2 year
No allergic response to this material.No allergic response to this material.

POLYETHER IMPRESSIONPOLYETHER IMPRESSION
MATERIALMATERIAL
 This was introduced in Germany in late 1960’s. it hasThis was introduced in Germany in late 1960’s. it has
good mechanical properties & dimensional stability.good mechanical properties & dimensional stability.
It is available as a base & accelerator in paste. It isIt is available as a base & accelerator in paste. It is
available in three viscosities :-available in three viscosities :-
 COMMERSIAL NAMECOMMERSIAL NAME
1.1. ImpregumImpregum
2.2. RamitecRamitec


BASEBASE
1.1. Polyether polymerPolyether polymer :-:-
Colloidal silica is usedColloidal silica is used
3.3. plasticizerplasticizer :-:-
Phthalate or GlycoletherPhthalate or Glycolether
usedused
 ACCELERATOR orACCELERATOR or
CATALYST PASTECATALYST PASTE
1.1. Aromatic sulfonate esterAromatic sulfonate ester
Silica is usedSilica is used
3.3. PlasticizerPlasticizer :-:-
Pathalate or GlycoeatherPathalate or Glycoeather

CHEMISTRYCHEMISTRY
 It is cured by the reaction between aziridineIt is cured by the reaction between aziridine
rings which are at the end of branched polyetherrings which are at the end of branched polyether
molecule. The main chain is a copolymer ofmolecule. The main chain is a copolymer of
ethylene oxide & tetrahydrofuran. Cross linkingethylene oxide & tetrahydrofuran. Cross linking
is brought about the aromatic sulfonate ester viais brought about the aromatic sulfonate ester via
imine end group. The reaction is exothermic.imine end group. The reaction is exothermic.
POLYEATHERPOLYEATHER++ SULFONIC ESTERSULFONIC ESTER →→
CROSS LINKED RUBBERCROSS LINKED RUBBER

it is 9 min at 23 degreeit is 9 min at 23 degree
3.3. Bitter taste with no smell.Bitter taste with no smell.
It is very good. Curing shrinkage is low withIt is very good. Curing shrinkage is low with
0.24%. The permanent deformation is low with0.24%. The permanent deformation is low with
1 – 2%1 – 2%
5.5. It is extremely stiff & flexibility is 3%.It is extremely stiff & flexibility is 3%.

1800 – 4800N/m1800 – 4800N/m
the Sulfonic eater component may causethe Sulfonic eater component may cause
skin allergy.skin allergy.
300300x10degree-1x10degree-1
10. Shelf life is 20 -24months.10. Shelf life is 20 -24months.

LIGHT ACTIVATED IMPRESSIONLIGHT ACTIVATED IMPRESSION
MATERIALMATERIAL
 With the increase used of light activated restorativeWith the increase used of light activated restorative
materials, light activated impression materials werematerials, light activated impression materials were
developed during the late1980’s. The advantages ofdeveloped during the late1980’s. The advantages of
such a material is there unlimited working time,such a material is there unlimited working time,
eliminating one of the primary challenge in clinicaleliminating one of the primary challenge in clinical
impression making for complex multi – abutment fixedimpression making for complex multi – abutment fixed
partial dentures. Its used chemistry is similar that usedpartial dentures. Its used chemistry is similar that used
by light cured composite.by light cured composite.
 Available in two viscosities :-Available in two viscosities :-
1.1. Lighted bodiedLighted bodied

1.1. Polyether urethanePolyether urethane
dimethacrylatedimethacrylate
2.2. Photo initiatorPhoto initiator
3.3. Photo acceleratorPhoto accelerator
4.4. Silica dioxide filler:- 40 – 60%Silica dioxide filler:- 40 – 60%

1.1. This material have a very long workingThis material have a very long working
time but short setting time. Blue light istime but short setting time. Blue light is
used for curing.used for curing.
6000 – 7500 gm/cm6000 – 7500 gm/cm
3.3. The dimensional stability, flow, detailThe dimensional stability, flow, detail
reproduction, permanent deformation,reproduction, permanent deformation,
compatibility with cast is similar tocompatibility with cast is similar to
addition silicone.addition silicone.

MANIPULATION OFMANIPULATION OF
ELASTOMERIC MATERIALELASTOMERIC MATERIAL
 SPATULATIONSPATULATION :-:-
Impression materials dispend in tubes requireImpression materials dispend in tubes require
spatulation on disposable pads. Dispending on thespatulation on disposable pads. Dispending on the
specific material, one or both paste may adherespecific material, one or both paste may adhere
tenaciously to the spatula. Wiping the spatula clean &tenaciously to the spatula. Wiping the spatula clean &
continuing to mix will minimizing the presence of streakscontinuing to mix will minimizing the presence of streaks
of unmixed base or catalyst.of unmixed base or catalyst.
 AUTOMIXING TECHNIQUEAUTOMIXING TECHNIQUE :-:-
Most silicone & polyether impression materialMost silicone & polyether impression material
are available in auto mix cartridge. Auto mix has beenare available in auto mix cartridge. Auto mix has been
shown to result in few voids. Direct syringe tips that fitsshown to result in few voids. Direct syringe tips that fits
into the auto mixing tube are available. Access isinto the auto mixing tube are available. Access is
occasionally a problem.occasionally a problem.
 MIXING MACHINESMIXING MACHINES :-:-
With in the last few years, a mixing machinesWith in the last few years, a mixing machines
was introduced for use with polyether impressionwas introduced for use with polyether impression
materials. Among its advantages is reduction of voids inmaterials. Among its advantages is reduction of voids in
the resulting mix & tray. Rather than rely on smallthe resulting mix & tray. Rather than rely on small
cartridge, larger bulk package of impression pate arecartridge, larger bulk package of impression pate are
available.available.

DISINFECTION OFDISINFECTION OF
ELASTOMERIC MATERIALSELASTOMERIC MATERIALS
1.1. POLYSULFIED IMPRESSION MATERIALPOLYSULFIED IMPRESSION MATERIAL :-:-
Glutaraldehydes, chlorine compounds,Glutaraldehydes, chlorine compounds,
iodophor, phenolics are the recommended disinfectant.iodophor, phenolics are the recommended disinfectant.
Impression should be immersed in this disinfectant forImpression should be immersed in this disinfectant for
30 sec.30 sec.
2.2. POLYETHER IMPRESSION MATERIALSPOLYETHER IMPRESSION MATERIALS :-:-
Chlorine compounds or iodophors areChlorine compounds or iodophors are
the recommended disinfectant. Immerse thethe recommended disinfectant. Immerse the
impression in to disinfectant, not more than for 10 min.impression in to disinfectant, not more than for 10 min.
3.3. SILICONE IMPRESSION MATERIALSILICONE IMPRESSION MATERIAL :-:-
Glutaraldehydes, chlorine compounds, iodophors,Glutaraldehydes, chlorine compounds, iodophors,
phenolic are the recommended disinfectant forphenolic are the recommended disinfectant for
Addition & Condensation silicon impression material.Addition & Condensation silicon impression material.
Impression should be immersed in the disinfectant forImpression should be immersed in the disinfectant for
30 min.30 min.

COMMON FAILURE THET OCCUR WITH USECOMMON FAILURE THET OCCUR WITH USE
OF ELASTOMERIC IMPRESSION MATERIALOF ELASTOMERIC IMPRESSION MATERIAL
1.1. Rough or uneven surface on impressionRough or uneven surface on impression:- it occur due to:- it occur due to
 Incomplete polymerizationIncomplete polymerization
 Improper ratioImproper ratio
 Presence of oil or other organic material on teethPresence of oil or other organic material on teeth
 Rapid polymerizationRapid polymerization
2.2. BubblesBubbles :- it occur due to:- it occur due to
 Too rapid polymerizationToo rapid polymerization
 Air incorporated during mixingAir incorporated during mixing
3.3. Irregular shaped voidsIrregular shaped voids :- it occur due to:- it occur due to
 Presence of moisture or debris on the surface of teethPresence of moisture or debris on the surface of teeth
4.4. Rough & chalkyRough & chalky:- it is due to:- it is due to
 Inadequate cleaning of impressionInadequate cleaning of impression
 Excess water left on surface of the impressionExcess water left on surface of the impression
 Excess wetting agent on impressionExcess wetting agent on impression
 Premature removal of castPremature removal of cast
5.5. DistortionDistortion :- it is due to:- it is due to
 Lack of adhesion on trayLack of adhesion on tray
 Lack of mechanical retention for material where is in effectedLack of mechanical retention for material where is in effected
 ExcessiveExcessive
bulk of materialbulk of material
 Movement of tray during polymerizationMovement of tray during polymerization
 Premature or improper removal of impressionPremature or improper removal of impressionwww.indiandentalacademy.comwww.indiandentalacademy.com

ADVANTAGES & DISADVANTAGESADVANTAGES & DISADVANTAGES
MATERIALSMATERIALS ADVANTAGESADVANTAGES DISADVANTAGESDISADVANTAGES
1. Polysulfide1. Polysulfide 1.Long working time1.Long working time
2.High tear resistance2.High tear resistance
3.Margins easily seen3.Margins easily seen
4.Comparativey4.Comparativey
5.Modest cost5.Modest cost
1.Poor patient1.Poor patient
acceptanceacceptance
2.Long setting time2.Long setting time
3.Require custom tray3.Require custom tray
4.Hydrophobic4.Hydrophobic
5.Pour with in hr.5.Pour with in hr.
2. Condensation2. Condensation
siliconesilicone
1.Short setting time1.Short setting time
2. Easy to use2. Easy to use
1.1. HighHigh
polymerizationpolymerization
shrinkageshrinkage
2.2. Low tear strengthLow tear strength
3.3. Low dimensionalLow dimensional
stabilitystability
4.4. More difficult toMore difficult to
pourpourwww.indiandentalacademy.comwww.indiandentalacademy.com

ADVATAGES & DISADVANTAGESADVATAGES & DISADVANTAGES
MATERIALSMATERIALS ADVANTAGESADVANTAGES DISADVANTAGESDISADVANTAGES
AdditionAddition
siliconesilicone
1.Excellent1.Excellent
dimensionaldimensional
2.Short setting time2.Short setting time
3.Auto mixing3.Auto mixing
cartridgecartridge
4.Easly seen margin4.Easly seen margin
1.Hydrophobic1.Hydrophobic
2.No flow if sulcus is2.No flow if sulcus is
moistmoist
3.Low strength3.Low strength
4.Difficult to pour4.Difficult to pour
5. High cost5. High cost
PolyetherPolyether 1.Auto mix1.Auto mix
dissensionsdissensions
2. Easily seen margin2. Easily seen margin
3.Good stability3.Good stability
4.High tear strength4.High tear strength
1.Stiff, high modulus1.Stiff, high modulus
2.Bitter taste2.Bitter taste
3.Absorb water3.Absorb water
4.High cost4.High cost

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