DUPLICATING AND REFRACTORY MATERIALS USED IN REMOVABLE PARTIAL DENTURES/ dental courses

DUPLICATING ANDDUPLICATING AND
REFRACTORY MATERIALSREFRACTORY MATERIALS
USED IN REMOVABLEUSED IN REMOVABLE
PARTIAL DENTURESPARTIAL DENTURES
INDIAN DENTAL ACADEMYINDIAN DENTAL ACADEMY
Leader in continuing Dental EducationLeader in continuing Dental Education
www.indiandentalacademy.comwww.indiandentalacademy.com

ContentsContents
1.1.      DEFINITIONDEFINITION
oo          DuplicationDuplication
oo          Refractory castRefractory cast
2.2.      DUPLICATION MATERIALSDUPLICATION MATERIALS
oo          Agar agarAgar agar
oo          AlginateAlginate
oo          SiliconesSilicones
oo          Aqueous acrylamide gelAqueous acrylamide gel
oo          Polyvinyl chloridePolyvinyl chloride

3.3.      REFRACTORY MATERIALSREFRACTORY MATERIALS
oo          Phosphate bondedPhosphate bonded
oo          Ethyl silicate bondedEthyl silicate bonded
oo          Gypsum bondedGypsum bonded
4. REVIEW OF LITERATURE4. REVIEW OF LITERATURE
5.5.      SUMMARY AND CONCLUSIONSUMMARY AND CONCLUSION
6.6.      BIBLIOGRAPHYBIBLIOGRAPHY

INTRODUCTIONINTRODUCTION
In preparingIn preparing partial denturespartial dentures , a, a
duplicate should be made of the stoneduplicate should be made of the stone
cast of the patient mouth. This duplicatecast of the patient mouth. This duplicate
is required foris required for two reasonstwo reasons::
1)1) The cast on which theThe cast on which the wax patternwax pattern ofof
thethe metal frameworkmetal framework is to be formedis to be formed
must be made from themust be made from the refractoryrefractory
investmentinvestment, because it must withstand, because it must withstand
the the casting temperaturesthe the casting temperatureswww.indiandentalacademy.comwww.indiandentalacademy.com

2)2) The original cast is needed forThe original cast is needed for checkingchecking
thethe accuracyaccuracy of the metal frameworkof the metal framework
and for processing the plastic portion ofand for processing the plastic portion of
the partial denture.the partial denture.

Duplication:Duplication:
 The procedure of accurately reproducing aThe procedure of accurately reproducing a
cast.cast.
Refractory Cast:Refractory Cast:
 A cast made of materials that willA cast made of materials that will
withstandwithstand high temperatureshigh temperatures withoutwithout
disintegrating and, when used in partialdisintegrating and, when used in partial
denture casting techniques, hasdenture casting techniques, has
expansion to compensate for metalexpansion to compensate for metal

MaterialsMaterials usedused for duplication:for duplication:
 Agar agarAgar agar
 AlginateAlginate
 SiliconesSilicones
 Aqueous acrylamide gelAqueous acrylamide gel
 Polyvinyl chloridePolyvinyl chloride

Agar agar:Agar agar:
 Agar is the material of choice to make theAgar is the material of choice to make the
mold for duplication, as it is a reversiblemold for duplication, as it is a reversible
hydrocolloid and can be used many times.hydrocolloid and can be used many times.

Composition :Composition :
 The basic constituent of the hydrocolloidThe basic constituent of the hydrocolloid
impression material isimpression material is agaragar..
 Agar is an organic hydrophilic colloidAgar is an organic hydrophilic colloid
extracted from certain types ofextracted from certain types of seaweedseaweed..
 It is a sulfuric ester of a linear polymer ofIt is a sulfuric ester of a linear polymer of
galactosegalactose..

 The principle ingredient by weight isThe principle ingredient by weight is waterwater
(>80%)(>80%)
 A small percentage (0.2% - 0.5%) ofA small percentage (0.2% - 0.5%) of boraxborax
is added to strengthen the gel.is added to strengthen the gel.
 To counteract the effects of water andTo counteract the effects of water and
borax,borax, potassium sulfatepotassium sulfate is addedis added
because it accelerates the setting ofbecause it accelerates the setting of
gypsum.gypsum. www.indiandentalacademy.comwww.indiandentalacademy.com

 Some products containSome products contain filler particlesfiller particles for the controlfor the control
of strength, viscosity, and rigidity. E.g., fillers usedof strength, viscosity, and rigidity. E.g., fillers used
are diatomaceous earth, clay, silica, wax, rubber andare diatomaceous earth, clay, silica, wax, rubber and
similar inert powders.similar inert powders.
 Other ingredients likeOther ingredients like thymolthymol as bactericide andas bactericide and
glyceringlycerin as plasticizer may be addedas plasticizer may be added
 PigmentsPigments andand flavorsflavors are also be added.are also be added.

Gelation process:Gelation process:
 The setting of a reversible hydrocolloid often calledThe setting of a reversible hydrocolloid often called
gelationgelation is a solidification process.is a solidification process.
SolSol GelGel
 The physical change from the sol to gel and viceThe physical change from the sol to gel and vice
versa is induced by aversa is induced by a temperaturetemperature change.change.
However the hydrocolloid gel does not return to theHowever the hydrocolloid gel does not return to the
sol at the same temperature at which it solidifies.sol at the same temperature at which it solidifies.
 The setting of a reversible hydrocolloid often calledThe setting of a reversible hydrocolloid often called
gelationgelation is a solidification process.is a solidification process.
SolSol GelGel
 The physical change from the sol to gel and viceThe physical change from the sol to gel and vice
versa is induced by aversa is induced by a temperaturetemperature change.change.
However the hydrocolloid gel does not return to theHowever the hydrocolloid gel does not return to the
sol at the same temperature at which it solidifies.sol at the same temperature at which it solidifies.www.indiandentalacademy.comwww.indiandentalacademy.com

 The gel must be heated to a higherThe gel must be heated to a higher
temperature known as thetemperature known as the liquefactionliquefaction
temperaturetemperature (70° to 100°C)(70° to 100°C) to return it toto return it to
the sol condition.the sol condition.
 When cooled from this temperatureWhen cooled from this temperature
range, the sol transforms into gel at a pointrange, the sol transforms into gel at a point
known asknown as gelation temperaturegelation temperature (37° to(37° to
50°C).50°C).

 The temperatureThe temperature laglag between the gelationbetween the gelation
temperature and the liquefactiontemperature and the liquefaction
temperature of the gel makes it possible totemperature of the gel makes it possible to
use agar as a impression material.use agar as a impression material.
 The molten colloid can beThe molten colloid can be storedstored for afor a
few days in a hydrocolloid storage unit atfew days in a hydrocolloid storage unit at
57°C – 60°C.57°C – 60°C.

AlginateAlginate
 A Chemist fromA Chemist from ScotlandScotland noticed that a certainnoticed that a certain
brown seaweed (algae) yielded a peculiarbrown seaweed (algae) yielded a peculiar
mucous extraction and named it asmucous extraction and named it as AlginAlgin..
 This natural substance was later identified as aThis natural substance was later identified as a
linear polymerlinear polymer with numerous carboxyl acidwith numerous carboxyl acid
groups and named an hydro-b-d- mannuronicgroups and named an hydro-b-d- mannuronic
acid (also calledacid (also called alginic acidalginic acid).).

The advantage of alginate over agar is:The advantage of alginate over agar is:
 ItsIts easyeasy to manipulateto manipulate
 RelativelyRelatively less duplication timeless duplication time
 RelativelyRelatively inexpensiveinexpensive because it doesbecause it does
not require elaborate equipment like agar.not require elaborate equipment like agar.

Modified alginates:Modified alginates:
 The traditional alginate is used as aThe traditional alginate is used as a twotwo
component systemcomponent system, a powder and liquid., a powder and liquid.
 However the alginate is also available in theHowever the alginate is also available in the
form of aform of a solutionsolution containing the water but nocontaining the water but no
source of calcium ions.source of calcium ions.

 A reactor of plaster of Paris can then be addedA reactor of plaster of Paris can then be added
to the solution.to the solution.
 There is yet another form that is available. TheThere is yet another form that is available. The
two component systemtwo component system which is in the formwhich is in the form
ofof two pastestwo pastes : one contains the alginate: one contains the alginate
solution and the other contains the calciumsolution and the other contains the calcium
reactor.reactor.

CompositionComposition::
 The chief active ingredient of the irreversibleThe chief active ingredient of the irreversible
hydrocolloid is one of thehydrocolloid is one of the soluble alginatesoluble alginate such assuch as
sodiumsodium,, potassiumpotassium oror triethanolaminetriethanolamine alginates.alginates.
 Other components like diatomaceous earth, and zincOther components like diatomaceous earth, and zinc
oxide act asoxide act as filler particlesfiller particles are added which canare added which can
increase the strength and stiffness of the alginate gel,increase the strength and stiffness of the alginate gel,
produce a smooth texture.produce a smooth texture.

 CaSOCaSO44 dihydrate or hemihydrate can bedihydrate or hemihydrate can be
used as aused as a reactorreactor..
 A fluoride, such as potassium titaniumA fluoride, such as potassium titanium
fluoride, is added as anfluoride, is added as an acceleratoraccelerator forfor
the setting of the stonethe setting of the stone
 NaPONaPO44 acts as aacts as a retarderretarder..

 The typical sol-gel reaction can be describedThe typical sol-gel reaction can be described
simply as a reaction ofsimply as a reaction of soluble alginatesoluble alginate withwith
calcium sulphatecalcium sulphate and the formation of anand the formation of an
insolubleinsoluble calcium alginate gel.calcium alginate gel.
 CaSOCaSO44 reacts rapidly to formreacts rapidly to form insolubleinsoluble calciumcalcium
alginate from the potassium or sodium alginate inalginate from the potassium or sodium alginate in
an aqueous solution.an aqueous solution.www.indiandentalacademy.comwww.indiandentalacademy.com

The production of the calcium alginate is so rapid that
it does not allow sufficient working time. Thus, a
third water soluble salt, such as trisodium phosphate,
is added to the solution to prolong the working time.

 The reaction between CaSO4
and the soluble alginate
is prevented as long as there is unreacted trisodium
phosphate.
2Na3
PO4
+ 3CaSO4
 Ca5
(PO4
)2
+ 3Na2
SO4
 When the supply of trisodium phosphate is
exhausted, the calcium ions begin to react with the
potassium alginate to produce calcium alginate.

Controlling gelation time:
 It is the time measured from the beginning of
mixing until gelation occurs.
 The optimal gelation time is between 3-4 min at
room temperature.
 Gelation time is best regulated by the amount of
retarder or by altering the temperature of the
water.

Silicones:
Two types of silicones are used as rubber
impression materials and are identified on
the basis of their chemical reactions as
 Condensation Silicone
 Addition Silicone

Condensation silicones
 They are supplied as a base and an
accelerator.
 The base contains a moderately low molecular
weight silicone called a dimethyl siloxane, which has
reactive terminal hydroxyl groups.

 FillersFillers like silica or copper carbonate are added tolike silica or copper carbonate are added to
the liquid silicone polymer to form a paste.the liquid silicone polymer to form a paste.
 AcceleratorsAccelerators like stannous octate or alkyl silicatelike stannous octate or alkyl silicate
are used.are used.

The condensation polymerization of this
material involves a reaction with trifunctional and
tetrafunctional alkyl silicates, commonly tetraethyl
orthosilicate, in the presence of stannous octate.
These reactions can take place at ambient
temperatures; thus, the materials are often called
room temperature vulcanization silicones.www.indiandentalacademy.comwww.indiandentalacademy.com

Ethyl alcohol is aEthyl alcohol is a by productby product of theof the
condensation setting reaction.condensation setting reaction.
Its subsequent evaporation probablyIts subsequent evaporation probably
accountsaccounts for condensation siliconesfor condensation silicones biggestbiggest
disadvantagedisadvantage which is poor dimensionalwhich is poor dimensional
stability.stability.

Addition silicones
 They are frequently called as polyvinyl siloxane.
 In contrast with the condensation silicones, the
addition reaction polymer is terminated with
vinyl groups and is cross linked with hydride groups
activated by a platinum salt catalyst.
 Both base and catalyst pastes contain a form of
the vinyl silicone.

 The base paste contains polymethylThe base paste contains polymethyl
hydrogen siloxane as well as other siloxanehydrogen siloxane as well as other siloxane
prepolymers.prepolymers.
 The catalyst paste contains divinylThe catalyst paste contains divinyl
polydimethyl siloxane and other siloxanepolydimethyl siloxane and other siloxane
prepolymers.prepolymers.

 If the catalyst paste contains the platinum salt
activator, then the base paste must contain the
hybrid silicone.
 Both pastes contain fillers, and retarders are
present in paste containing the activator.
 One of its disadvantage is its inherent
hydrophobicity.

Aqueous acrylamide gel:
The time necessary for performing the duplicating
procedure using agar which is used successfully in
dental laboratory duplicating procedures is 2 to 3
hours.
There are situations however in which a duplicating
material is needed that can produce a cast in a very
short period of time.

Aqueous acrylamide gel was produced from a
mixture of two organic monomers,
acrylamide and N, N – methylenebis
acrylamide in water.
 When these substances are catalysed by
the addition of ammonium persulfate and
b-dimethylaminoprionitrile, a transparent
gel forms by a polymerization – cross linking
reaction. www.indiandentalacademy.comwww.indiandentalacademy.com

 This material is commercially available under the
trade name of CYANOGUM 41 or AM-9
chemical group.
 Potassium alginate is added for the purpose of
preventing sticking between the acrylamide gel
and the master or refractory cast.
 It is a duplicating material that allows a mold to

Polyvinylchloride
 It is a reversible plastic gel.
 The main advantages of this material are:
 High strength properties
 High chemical stability, which permit a
large number of duplications before replacement.

Properties and requirements of
duplicating material
ANSI / ADA specification no. 20 for dental
duplicating materials includes 2 types
1.   Thermoreversible (Type I)
-  Hydrocolloidal (Class I)
-  Nonaqueous organic (Class II)
2.   Non reversible (Type II)
-  Hydrocolloidal (Class I)
-  Nonaqueous organic (Class II)

The specification sets requirements of
freedom
from foreign material and impurities and
It should be suitable for duplication of
plaster, stone or investment casts of the oral
tissues.

 Pouring temperaturePouring temperature and theand the temperaturetemperature
of gel formationof gel formation are defined for theare defined for the
thermoreversible products.thermoreversible products.
 Working and setting timesWorking and setting times are specified forare specified for
the non-reversible material.the non-reversible material.
 CompatibilityCompatibility with at least one type ofwith at least one type of
investment and the ability to reproduce detailinvestment and the ability to reproduce detail
satisfactorily are required.satisfactorily are required.www.indiandentalacademy.comwww.indiandentalacademy.com

 Type I products should be dimensionally stable
after inoculation under controlled conditions.
 Requirements for permanent deformation, strain in
compression, and resistance to tearing are
described.

 Packaging must include instructions that indicatePackaging must include instructions that indicate
thethe type of investmenttype of investment that can be used withthat can be used with
the material.the material.
 For type I products, must also include (1) methodFor type I products, must also include (1) method
ofof liquefyingliquefying (2)(2) temperingtempering oror storingstoring
temperature and (3)temperature and (3) pouringpouring temperature.temperature.

Refractory materials:
The rapid growth in use of cast removable
partial dentures , the increased use of
higher melting alloys and the use of less
expensive base metal alloys have
resulted in an increased use of phosphate
or silicabonded refractory material.

Phosphate bonded:
Composition:
 These investments consist of refractory fillers and a
binder.
 The filler is silica, in the form of Cristabalite, Quartz, or a
mixture of the two and in a concentration of approx 80%.
 The binder consists of magnesium oxide and a phosphate
that is acid in nature. www.indiandentalacademy.comwww.indiandentalacademy.com

 It is fortunate that the colloidal silica suspensions
became available in time for use with the phosphate
investments in place of water to compensate for the
greater contraction of the high fusing alloys during
solidification, as it increases the setting expansion of the
investment.

 Carbon is often added to the powder to produce clear
castings and facilitate the divesting of the casting from the
mold.
 But the latest evidence indicates that palladium does react
with carbon at temperature above 1504°C. Thus if the
temperature exceeds this temperature during casting, a
carbon free investment should be used. www.indiandentalacademy.comwww.indiandentalacademy.com

Setting reactions
 Magnesium ammonium phosphate formed is
polymeric. Although the stoichiometric quantities are equal
molecules of magnesia and monoammonium phosphate, an
excess of magnesia is usually present, and some of it is
never fully reacted.
 What is thus formed is a predominantly colloidal
multimolecular aggregate around excess MgO and fillers.
On heating, the binder of the set investment undergoes
thermal reactions.

Setting and thermal expansion:
 Theoretically, the reaction should entail a shrinkage, but
in practice there is a slight expansion by using a colloidal
silica solution instead of water.
 The early thermal shrinkage of phosphate investments is
associated with the decomposition of the binder, magnesium
ammonium phosphate, and is accompanied by evolution of
ammonia.
 Some of the shrinkage is masked because of the
expansion of the refractory filler especially in the case of
cristobalite

Working and setting time:
 Phosphate investments are affected by temperature.
 The setting reaction itself gives off heat, and this
further accelerates the rate of setting.
 Increase in mixing time and mixing efficiency results
in faster set.
 Increase in w:p ratio, increases the working time.

Ethylsilicate-bonded:Ethylsilicate-bonded:
losing popularitylosing popularity -- complicated and timecomplicated and time
consuming proceduresconsuming procedures involved.involved.
BBinder is a silica get that reverts to silica oninder is a silica get that reverts to silica on
heating. Several methods may be used toheating. Several methods may be used to
produce the silica or silicic acid gel binders.produce the silica or silicic acid gel binders.

 Another system for binder formation isAnother system for binder formation is basedbased
onon ethyl silicateethyl silicate. A colloidal silicic acid is. A colloidal silicic acid is
formed by hydrolyzing ethyl silicate in theformed by hydrolyzing ethyl silicate in the
presence of hydrochloric acid, ethyl alcohol andpresence of hydrochloric acid, ethyl alcohol and
water.water.

 A polymerized form of ethyl silicate is used a
colloidal solution of polysilicic acid is formed. This
solution is mixed with quartz or cristabolite to which is
added a small amount of finely powdered MgO to
render the mixture alkaline.

 AA coherent gel of poly silicic acidcoherent gel of poly silicic acid thenthen
forms, accompanied by aforms, accompanied by a setting shrinkagesetting shrinkage ..
 This soft gel is dried at a temperature belowThis soft gel is dried at a temperature below
168°C. During the drying process, the gel168°C. During the drying process, the gel losesloses
alcoholalcohol and water to form a concentrated, hardand water to form a concentrated, hard
gel.gel.

This contraction is known asThis contraction is known as “green shrinkage”“green shrinkage”
and it occurs in addition to the setting shrinkage.and it occurs in addition to the setting shrinkage.
Investments of this type are designed to reduce theInvestments of this type are designed to reduce the
layer of silica gel around the particles.layer of silica gel around the particles.
This type of investment can beThis type of investment can be heatedheated to 1090°Cto 1090°C
to 1180°C and isto 1180°C and is compatible with the highercompatible with the higher
fusing alloysfusing alloys..

Gypsum bonded:
 When casting gold alloys gypsum bonded
investment material can be used. Most materials
now contain alpha-hemihydrate because of
their greater strength.
 This gypsum product serves as a binder to hold
the other ingredients together and to provide rigidity.

 TheThe strengthstrength of the material is dependent onof the material is dependent on
the amount ofthe amount of binderbinder present. The materialpresent. The material
may containmay contain 25% to 45%25% to 45% of gypsum.of gypsum.
 In addition to silica certainIn addition to silica certain modifyingmodifying
agents, coloring matter and reducingagents, coloring matter and reducing
agents,agents, such as carbon and powderedsuch as carbon and powdered
copper are present.copper are present.

Some of the modifiers such as boric acid and sodium
chloride
- not only regulate the setting expansion and
the setting time but
- they also prevent most of the shrinkage of
gypsum when it is heated above 300°C.

 But all forms of gypsumBut all forms of gypsum dehydratedehydrate betweenbetween
200-400°C. A slight200-400°C. A slight expansionexpansion occursoccurs
between 400°C – 700°C and then a largebetween 400°C – 700°C and then a large
contractioncontraction occurs.occurs.
 This latter shrinkage is most likely causedThis latter shrinkage is most likely caused
by decomposition ofby decomposition of sulfur gasessulfur gases, such as, such as
sulfur dioxidesulfur dioxide www.indiandentalacademy.comwww.indiandentalacademy.com

ThisThis decompositiondecomposition not only causesnot only causes
shrinkageshrinkage but alsobut also contaminatescontaminates thethe
castings with the sulfides of the non-noblecastings with the sulfides of the non-noble
alloying elements, such as silver and copper.alloying elements, such as silver and copper.
Thus it is imperative that gypsum bondedThus it is imperative that gypsum bonded
materialmaterial notnot be heated above 700°Cbe heated above 700°C ..

 SilicaSilica is added to provide ais added to provide a refractoryrefractory
during the heating of the material and toduring the heating of the material and to
regulate the thermal expansionregulate the thermal expansion ..
 If proper forms of silica like quartz orIf proper forms of silica like quartz or
crystabolite are used in the material, thecrystabolite are used in the material, the
contraction during the heating can becontraction during the heating can be
eliminated and changed to aneliminated and changed to an expansionexpansion..

 F.A Peyton and R. G. Craig (1962)F.A Peyton and R. G. Craig (1962)
conducted a study to test theconducted a study to test the compatibility ofcompatibility of
duplicating compounds and castingduplicating compounds and casting
investmentsinvestments. This study was designed to establish. This study was designed to establish
the surface hardness, surface roughness and thermalthe surface hardness, surface roughness and thermal
expansion of different investment material pouredexpansion of different investment material poured
against different duplicating media.against different duplicating media.
REVIEW OF LITERATURE

 Measurements of surface detail showed thatMeasurements of surface detail showed that
Gypsum bonded investmentGypsum bonded investment werewere
incompatibleincompatible with all the duplicating materials.with all the duplicating materials.
 Phosphate bonded investmentsPhosphate bonded investments werewere
compatible withcompatible with plasticplastic duplicating compound.duplicating compound.
 Silicate bonded investmentSilicate bonded investment werewere
compatible withcompatible with agaragar duplicating compound.duplicating compound.

 PBIPBI werewere harderharder when produced againstwhen produced against
plastic duplicating media.plastic duplicating media.
 GBIGBI showedshowed variablevariable results andresults and
 SBISBI werewere weakweak and cannot be testedand cannot be tested

E. R. Dootz, R. G. Craig, F. A. Peyton (1965)E. R. Dootz, R. G. Craig, F. A. Peyton (1965)
Conducted a study to see theConducted a study to see the
influence ofinfluence of investments and duplicatinginvestments and duplicating
proceduresprocedures on theon the accuracyaccuracy of partial dentureof partial denture
castings. This study was designed to see the effectcastings. This study was designed to see the effect
of changing duplicating materials, soaking refractoryof changing duplicating materials, soaking refractory
cast in water, applying the paint-on layer and outercast in water, applying the paint-on layer and outer
layer of investment on casting accuracy.layer of investment on casting accuracy.

 The results revealed that the totalThe results revealed that the total
compensating expansion through thecompensating expansion through the basebase
of the refractory cast may not be equal toof the refractory cast may not be equal to
the expansion through thethe expansion through the tissue surfacetissue surface
of the cast.of the cast.
 The compensating expansion wasThe compensating expansion was
increased by soaking the refractory castincreased by soaking the refractory cast
inin waterwater and by applying aand by applying a paint-on layerpaint-on layer..

 Peter R. Likeman, David R. Radford,Peter R. Likeman, David R. Radford,
Andrzej S. Juszczyk(1996)Andrzej S. Juszczyk(1996)
Conducted a study to investigate theConducted a study to investigate the
surfacesurface of investments poured againstof investments poured against
different duplicating mediadifferent duplicating media . In this study. In this study
they used two PBI material and comparedthey used two PBI material and compared
their surface characteristics with duplicatingtheir surface characteristics with duplicating
gel and poly (vinyl siloxane) duplicatinggel and poly (vinyl siloxane) duplicating
mediummedium

 The hardness of samples poured inThe hardness of samples poured in
poly(vinyl siloxane)poly(vinyl siloxane) was greater than that ofwas greater than that of
same investment poured in duplicating gelsame investment poured in duplicating gel
 Microscopic examination revealed greaterMicroscopic examination revealed greater
surface irregularitysurface irregularity of samples poured inof samples poured in
duplicating gelduplicating gel than in poly(vinyl siloxane).than in poly(vinyl siloxane).

Robert W.Rudd and Kenneth E.RuddRobert W.Rudd and Kenneth E.Rudd in theirin their
review article (2001) stated that problems encounteredreview article (2001) stated that problems encountered
during duplicating due toduring duplicating due to
 Using contaminated materialUsing contaminated material
 Failing to seal the definative cast to bottem ofFailing to seal the definative cast to bottem of
the flaskthe flask
 Pouring over heated materialPouring over heated material
 Delaying the pouring the stone or investment.Delaying the pouring the stone or investment.

Summary and Conclusions
In this seminar the commonly used
duplicating and refractory materials were described.
Agar agar and phosphate bonded materials are
used extensively as duplicating and refractory
materials respectively because of their advantages
over the other materials.
Knowledge of these materials is a pre-requisite
for obtaining acceptable refractory casts.

ReferencesReferences
 Craig R.G. and Powers J.M.Craig R.G. and Powers J.M. ;; Restorative DentalRestorative Dental
MaterialsMaterials, 11, 11thth
edition, Mosby publishers,edition, Mosby publishers, 20022002
 Dootz E.R., Craig R.G., PeytonDootz E.R., Craig R.G., Peyton F.A.F.A. :: The influence ofThe influence of
investments and duplicating procedures on the accuracy ofinvestments and duplicating procedures on the accuracy of
partial denture castings.partial denture castings.
J. Prosthet. Dent.J. Prosthet. Dent. 19651965; 15: 679-690.; 15: 679-690.
 Dootz E.R., Craig R.G. and Peyton F.A.Dootz E.R., Craig R.G. and Peyton F.A. ;; AqueousAqueous
accrylamide gel duplicating materialaccrylamide gel duplicating material
J. Prosthet. Dent.J. Prosthet. Dent. 19671967;17: 571-577;17: 571-577www.indiandentalacademy.comwww.indiandentalacademy.com

 Kenneth J.AnusaviceKenneth J.Anusavice ;; Phillip’s Science of DentalPhillip’s Science of Dental
MaterialsMaterials, 11, 11thth
edition, W.B. Saunders publishers,edition, W.B. Saunders publishers,
20032003
 McCracken’sMcCracken’s ;; Removable Partial ProsthodonticsRemovable Partial Prosthodontics,,
1111thth
edition,Mosby publishers,edition,Mosby publishers, 20052005
 Peyton F.A., CraigPeyton F.A., Craig R.G.R.G. : Compatibility of: Compatibility of
duplicating compound and casting investments.duplicating compound and casting investments.

 Peter R. Likeman, David R. Radford, Andrzej S.Peter R. Likeman, David R. Radford, Andrzej S.
JuszczykJuszczyk : The surface of investment poured against: The surface of investment poured against
different duplicating media.different duplicating media.
 Phillips R.W.Phillips R.W. :: Skinner’s Science of DentalSkinner’s Science of Dental
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