Elastomers

PRESENTED BY :
Dr. PRAJAKTA BALI GIR
MDS 1st YEAR
ELASTOMERS

 INTRODUCTION
 HISTORY
 CLASSIFICATION OF IMPRESSION MATERIAL
 ELASTOMERIC IMPRESSION MATERIALS
 POLYSULPHIDES
 POLYSILICONES :
1. CONDENSATION POLYSILICONES
2. ADDITION POLYSILICONES
 POLYETHERS
 PROPERTIES
CONTENTS
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 MANIPULATION OF ELASTOMERIC MATERIALS
 MIXING SYSTEMS
 IMPRESSION TECHNIQUES
 FAILURE CAUSES
 DISINFECTION
 REVIEW OF LITERATURE
 CONCLUSION
 REFERENCES
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INTRODUCTION
IMPRESSION - A negative likeness or copy in reverse of the
surface of an object; an imprint of the teeth and adjacent structures
for use in dentistry (GPT 9)
IMPRESSION MATERIAL - Any substance or combination of
substances used for making an impression or negative
reproduction. (GPT 9)
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HISTORY
YEAR / DECADE EXTENT
1730s Sealing wax and plaster casts were introduced
1820 Impression tray was made
1844 Plaster impressions were developed
1857 Modeling compound was developed
1883 E.C.C. Stanford, a British pharmacist, discovered algin, the
precursor for alginate
1925 Reversible hydrocolloid introduced by Alphons Poller, an
Austrian who patented it as “Nogacoll”
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YEAR / DECADE EXTENT
1929 Commercial production of alginate by a company named
“Kelco” in California
1931 Hydrocolloid “Denticole” was first marketed
1935 A.W. Sears promoted the use of agar as an impression
material for fixed partial dentures
1953 Polysulfide impression material was introduced
1960s Polyether impression material was introduced
1970s Condensation silicone was introduced
1980s Addition silicone material was introduced
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CLASSIFICATION OF IMPRESSION MATERIALS

9
IMPRESSION MATERIALS
NON ELASTIC ELASTIC
PLASTER
ZOE
IMPRESSION
COMPOUND
HYDROCOLLOIDS NON-AQUEOUS
AGAR
ALGINATE
POLYSULPHIDES
SILICONES
POLYETHERS
William J O'Brien Dental materials selection 3rd edition
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10
SETTING MECHANISM
DISPENSING MECHANISM
CLINICAL APPLICATIONS
PRESSURE APPLIED
AREA
MECHANICAL PROPERTIES
TRAY USED
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11
SETTING MECHANISM
1. REVERSIBLE = impression compound, dental waxes, and agar hydrocolloids
2. IRREVERSIBLE = alginate, zinc oxide eugenol, and elastomers
3. THERMAL CHANGE = Impression compound, agar-agar, impression waxes.
4. CHEMICAL CHANGE = zinc oxide eugenol impression pastes, impression
plaster, elastomers, alginates.
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12
DISPENSING MECHANISM
1. POWDER : Impression plaster, alginates
2. TWO PASTES SYSTEM : ZnOE impression pastes, polysulphides and
polysilicones
3. THREE PASTES SYSTEM : Chemically activated polyether (base, reactor,
thinner)
4. SINGLE PASTES SYSTEM : Light activated polyether
5. GELS : Agar-agar
6. SUPPLIED IN THE FORM OF CAKES, CYLINDERS, STICKS,
SHEETS AND CONES : impression compound, impression waxes
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13
CLINICAL APPLICATIONS
1. PRIMARY/PRELIMINARY IMPRESSIONS, e.g. impression compound, impression
waxes, alginates, elastomers (heavy and regular bodies)
2. SECONDARY/CORRECTIVE WASH IMPRESSIONS, e.g. impression plaster, ZnOE
impression pastes, elastomers, polysulfides, polyethers, poly silicones (light bodies), (agar-
agar)
3. BORDER MOULDING IMPRESSION, e.g. green stick compound
4. CAVITY IMPRESSIONS FOR INLAYS AND ONLAYS, e.g. elastomers
5. CROWN AND BRIDGE IMPRESSION, e.g. hydrocolloids-agar-agar, alginates
elastomers–polysilicones, polysulphides, polyethers
6. PARTIAL DENTURE IMPRESSIONS, e.g. hydrocolloids-agar-agar, alginates ,
elastomers–polysilicones, polysulphides, polyethers.
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14
PRESSURE APPLIED
1. MUCOCOMPRESSIVE :
Impression compound
2. MUCOSTATIC :
Impression plaster
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15
AREA
1. EDENTULOUS
CONDITION:
All impression materials
(impression compound,
impression waxes, impression
plaster, ZnOE impression
pastes, hydrocolloids,
elastomers)
2. DENTULOUS
CONDITION:
Hydrocolloids and elastomers
are only to be used.
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16
MECHANICAL PROPERTIES
1 . ELASTIC
IMPRESSION
MATERIALS:
These when deformed,
should recover elastically,
e.g. hydrocolloids (agar-
agar and alginates)
elastomers (polysilicones,
polysulphides and
polyethers)
2. NONELASTIC
IMPRESSION
MATERIALS:
Impression compound,
impression waxes,
impression plaster, zinc
oxide eugenol
impression pastes.
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17
TRAY USED
A . STOCK TRAYS =
1. Rim lock perforated trays
Eg. Alginate, Elastomers
2. water cooled
Eg. Agar
3. plastic trays
a. perforated- Eg.
Alginate,
Elastomers
b. Non perforated-
Eg. Impression
compound
B. SPECIAL TRAYS =
1. Base plate wax
Eg. ZOE paste,
Medium body
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ELASTOMERIC IMPRESSION
MATERIALS

An elastomer can be defined as a three dimensional polymer network
which has good elasticity and has a wide elastic range within an
intended working temperature range.
Dental elastomers are a group of rubbery polymers, which are either
chemically or physically crosslinked.
They can be easily stretched and they rapidly recover their original
dimensions when the applied stress is released.
ABOUT ELASTOMERS
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The viscoelastic property of these materials is easy
enough to make an accurate impression in undercut
areas with less distortion and dimensional instability.
Introduced in the 1950s, impression materials of this
group are usually called nonaqueous elastomeric
impression materials.
The long polymer chains cross-link during curing. The
molecular structure of elastomers can be imagined as a
'spaghetti and meatball' structure, with the meatballs
signifying cross-links .
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The first elastomeric impression materials were polysulfides, followed
by condensation silicones, polyethers, and addition silicones.
Condensation silicones were made available to dentists in 1955,
polyether in 1965, and addition silicones in 1975.
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CLASSIFICATION OF ELASTOMERIC

23
ELASTOMERS ADA NO :19
CHEMICAL NATURE
VISCOSITY
METHOD OF
POLYMERIZATION
METHOD OF DISPENSING
CLINICAL APPLICATIONS OR
USES
DIMENSIONAL STABILITY, FLOW
AND PERMANENT DEFORMATIONS
1
2
3
4
5
6
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1. POLYSULPHIDES
2. POLYSILICONES
• - Addition polysilicones
• - Condensation polysilicones
3. POLYETHERS
• - Light activated polyethers
• - Chemically activated polyethers
ACCORDING TO CHEMICAL
NATURE
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0 = VERY HIGH VISCOSITY MATERIAL -
putty like elastomers.
1 = HIGH VISCOSITY MATERIAL - heavy
body elastomers.
2 = MEDIUM VISCOSITY MATERIAL -
regular body elastomer.
3 = LOW VISCOSITY MATERIAL - light body
elastomer-syringe consistency.
ACCORDING TO
VISCOSITY
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1. ADDITION POLYMERIZATION
MATERIALS,
e.g. Polyether, addition polysilicones
2. CONDENSATION POLYMERIZATION
MATERIALS,
e.g. condensation polysilicones and polysulphides
ACCORDING TO METHOD
OF POLYMERISATION
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1. SINGLE PASTE SYSTEM: Light activated polyether
2. TWO PASTE SYSTEM (BASE + REACTOR PASTE): polysulphides, addition and
condensation polysilicones
3. TWO PASTE SYSTEM HAVING PSEUDOPLASTIC PROPERTY-SUPPLIED IN A
SINGLE CONSISTENCY WHICH CAN BE USED AS A TRAY AND SYRINGE
MONOPHASE MATERIAL, e.g. addition polysilicones
4. SINGLE PASTE (BASE PASTE) WITH REACTOR LIQUID, e.g. condensation
polysilicones
5. THREE PASTE SYSTEM-BASE + REACTOR + BODY MODIFIER (THINNER),
e.g. chemically activated polyether
ACCORDING TO METHOD OF DISPENSING
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ACCORDING TO CLINICALAPPLICATIONS OR USES
KIND OF
IMPRESSION
OBJECT OF IMPRESSION COMBINATIONS
Double mix single
impression
Cavity impressions for inlays and
onlays
Light + heavy body
Double mix , double
impression (reline
technique)
Cavity impressions for inlays,
onlay, etc. impressions of a crown
and impressions of a partial
denture
Putty + light body or putty +
regular body
Individual tray method
(tube impression)
Impression for a crown (single
tooth)
Regular body or light body
Single mix single
impression
impression Cavity impressions for
inlays and onlays. Impressions for
partial dentures
Regular or heavy having
pseudoplastic property or light
or regular body
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ACCORDING TO DIMENSIONAL
STABILITY, FLOW AND
PERMANENT DEFORMATIONS
TYPES MAXIMUM
PERMANENT
DEFORMATIO
N %
MAXIMUM
FLOW IN
COMPRESSION
%
MAXIMUM
DIMENTION
AL CHANGE
IN 24 HRS %
I 2.5 0.5 0.5
II 2.5 0.5 1.0
III 2.5 2.0 0.5
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CHEMISTRY AND COMPOSITION OF
ELASTOMERIC IMPRESSION MATERIAL
30

ABOUT POLYSULPHIDES
 Polysulfide impression material was the first nonaqueous elastomeric “rubber”
impression material developed for dentistry.
 Often, polysulfide materials are called “rubber” or “rubber base” materials,
even though polyether and silicone materials are also rubber materials.
 Due to their high accuracy and relatively low cost, polysulfide rubbers are
widely used for fixed partial denture application.
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 These materials are useful for multiple impressions when extra time is
needed.
 One very important difference between types of elastomeric impression
materials is the adhesive that is used to bond the impression material to a
nonperforated tray.
 Each impression material has its own adhesive, which will not work with
other types of material .
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VULCANISATION AND CHEMICAL REACTION
 The process of heating the rubber with sulphur to produce cross-linking.
 The main component of polysulfide materials is mercaptan (-SH).
 The lead dioxide catalyzes the condensation of the terminal and pendant -SH
with -SH groups on other molecules, resulting in chain lengthening and cross-
linking.
 In the process, the material changes from a paste to a rubber .
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 The reaction is accelerated by increase in temperature and by the presence of
moisture.
 Lead dioxide is the component that gives polysulfide its characteristic brown
colour .
 Lead dioxide is toxic and has bad smell, so it has been replaced in recent
products by peroxide compounds.
 It is an exothermic reaction with 3°C–4°C rise in temperature.
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 It is a condensation reaction in which water is formed as a by product .
 Polysulfide impression materials shrink 0.3% to 0.4% during the first 24 hours,
and thus models and dies should be prepared promptly .
 mercaptan + lead dioxide = polysulfide rubber + lead oxide + water
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DISPENSING
 These are supplied as a 2 paste system in collapsible tubes, and are available in
all 4 viscosities, light, regular, heavy body and putty like consistencies.
 Note:
• L → Light body,
• R → Regular body,
• H → Heavy body,
• P → Putty consistency
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ALTERNATIVE NAMES
 Thiokol corporation material : By the name of the first-manufacturer.
 Mercaptan impression material : By chemistry (–SH groups).
 Vulcanising impression material : By processing terminology.
 Permlastic (Kerr)
 Omni-Flex (GC America)
 Coe-Flex
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COMPOSITION
BASE PASTE
Polysulphide prcpolymer with terminal
and pendant thiol (–SH) groups
Plasticizer-di-n-butyl phthalate
Inert filler – possibly chalk or titanium
dioxide
REACTOR PASTE
PbO2 (lead dioxide) (or, – Cu (OH)2 )
oxidation of (cumane hydroxide)
Sulphur
Dibutyl phthalate (plasticizer)
Inert oil (oleic acid, stearic acid, Mg stearate)
Deodorants
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MANIPULATION
 The two pastes are dispensed in equal lengths on a paper mixing pad.
 An impression material spatula is used to mix the two pastes .
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 The pastes are swirled and stropped
together until a homogeneous paste is
obtained.
 The side of the spatula blade is used to
scrape unmixed material from the paper
pad and then to mix it into the rest of the
material.
 The mixed material is loaded into the tray
and placed in the mouth as a viscous paste.
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USES
 To record dentulous impressions for preparation of crowns, bridges, inlays,
onlays, partial dentures, etc.
 To record impressions of edentulous arches in the preparation of complete
dentures.
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ADVANTAGES
 It has a longer working time
 Highest flexibility 14–17%,
 easy removal over undercuts
 Highest tear strength (2,500–7,000 gm/cm)
 Less expensive when compared to other elastomers
 Long shelf-life.
 Can be electroplated with silver.
 It is compatible with dye stones.
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DISADVANTAGES
 Disagreeable odour and taste due to presence of PbO2
 Longer setting time
 Dimensional change due to evaporation of byproducts, i.e. water (3–6%)
 It will stain clothes
 Second or multiple dye pouring is less accurate.
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POLYSILICONES
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ABOUT POLYSILICONES
 The many disadvantages of polysulfide rubber base impression material
resulted in the development of the silicone impression materials.
 Depending on the type of chemical reaction, there are two types of silicone
rubber-based impression materials, namely, condensation silicones and
addition silicones, also known as polyvinyl siloxanes.
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CONDENSATION
POLYSILICONE
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CONDENSATION SILICONE
 Condensation silicone impression materials were the next elastomeric
impression material to be developed for dentistry.
 They are based on silicone rubber, which is commonly used in other industries.
 It is also called as room temperature vulcanizing (RTV) silicones.
 Also known as conventional silicones .
 These materials are not popular at present because newer materials provide
better results.
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DISPENSING
 It is supplied in 2 forms , two paste form in collapsible tubes, i.e. base +
reactor or The base paste and reactor liquid.
 Materials are available in all 4 viscosities or consistencies.
• L → Light body,
• R → Regular body,
• H → Heavy body,
• P → Putty consistency
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COMPOSITION
LIQUID
Tri or tetra functional ethyl silicate
Organometallic compound, tin octoate
Reinforcing fillers or thickening agents
Colour pigments (organic dyes)
BASE
Moderately low molecular wt. silicone
prepolymer with hydroxyl terminated group
Reinforcing fillers: (Copper carbonate,
colloidal silica of particle size ranging from
2–10 mm) 35–75% (L, R, H, Putty
consistencies)
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SETTING REACTION
 On mixing the two components, base and reactor the reaction begins
immediately in which the terminal hydroxyl groups of prepolymer chains react
with the cross linking agent, tetra ethyl orthosilicate, under the influence of
catalyst, i.e. tin octoate.
 Each molecule of cross-linking agent can potentially react with four prepolymer
chains, causing extensive crosslinking.
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 Which produces increase in viscosity and rapid development in elastic
properties.
 It is a condensation reaction producing ethyl alcohol as by product.
 The multifunctional ethyl silicate produces a network or cross linked
structures that reduce permanent deformation and flow values .
 Moderately low molecular. wt. silicone prepolymer with OH terminal group
+ ethyl silicate → ortho silicate rubber
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MANIPULATION
 The manipulation of condensation silicones is the same as for polysulfides,
except that the silicone material may be supplied as a base paste plus a liquid
catalyst.
 When it is supplied in this form, one drop per inch of extruded base paste is
usually recommended.
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 Electroplating is an option.
 Because of the high polymerization shrinkage, the cast or die must be poured
as soon as possible.
 Higher temperatures and humidity shorten the setting time.
 Speedex (Coltene/Whaledent), Accoe (GC America)
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USES
 Used for recording dentulous impressions in preparation of crowns, bridges,
inlays, onlays and to some extent for partial dentures.
 Used to record the edentulous impressions in the preparation of complete
dentures.
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ADVANTAGES
 It has adequate working time and setting times
 Clean, pleasant odour and there is no staining
 Adequate tear strength
 Better elastic recovery properties on removal
 Available in complete range of viscosities, thus allowing flexibility in
choosing an impression material.
 Can be electroplated with silver or copper.
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DISADVANTAGES
 Lower flexibility than polysulphides
 Poor dimensional stability due to release of byproducts, ethyl alcohol
 Less accuracy if poured immediately, cast pouring is delayed by 20–30 min
for maximum elastic recovery.
 Requires a very dry field.
 material may be hazardous if not handled properly.
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 Since condensation silicones are hydrophobic in nature, air bubbles are
likely to occur in the impressions, as the material is readily repelled by water
or saliva.
 Poor to adequate shelf life (1–2 years).
 Slightly more expensive
 Putty-wash method is technique sensitive
 Liquid component of the reactor paste material may be hazardous if not
handled properly.
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ADDITION POLYSILICONE
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 Addition silicones are the most popular type of elastomeric impression
material, especially for crown and bridge impressions.
 Addition silicone impression materials are also called vinyl polysiloxanes and
polyvinylsiloxanes.
 They are expensive, however, and therefore are not used for routine study casts
ADDITION POLYSILICONE
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 Supplied as two paste systems and available in all four viscosities.
 Also available in a single consistency called single phase or monophase
material.
 It can be used both as a tray and a syringe material due to pseudoplastic
property
DISPENSING
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 Extra-low
 Low(syringe or wash)
 Medium (regular)/monophase
 High (tray)
 Putty (extra-high) consistencies
AVAILABLE IN
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COMPOSITION
BASE
Polymethyl hydrogen siloxane or
moderately low molecular weight
silicone pre-polymer with silane
terminal groups
Reinforcing fillers: (Powdered silica)
REACTOR
Polydimethyl vinyl siloxane or moderately low
molecular weight silicone prepolymer with vinyl
terminal group
Reinforcing fillers: (Powdered silica)
Chloroplatinic acid (H2PtCl6 )
Low molecular weight liquid polymer
(polydimethyl hydrogen siloxane)
Finely divided platinum or palladium
Colour pigment (different for L, R, H, P)
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 On mixing the two pastes, a platinum catalyzed addition reaction occurs
causing cross-linking between the two types of siloxane prepolymers to form
silicone rubber.
 The reaction does not have byproducts which results in a minimum
dimensional change during polymerization reaction.
 Side reactions will produce hydrogen gas .
SETTING REACTION
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 The hydrogen gas could also be formed if moisture or residual silane groups
are present
 It could also be due to the decomposition of the catalyst producing hydrogen
gas.
 The present day silicones contain a noble metal such as platinum or
palladium to act as scavenger for the hydrogen gas evolved.
 The hydrogen gas evolved can result in pin hole voids in the impression
which might affect the master cast.
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 Remedy is to pour the
impression one hour
after recording the
impression or
elimination of
impurities if present or
subjecting the
impression to vacuum
before pouring the stone
cast
Addition-silicone impressions poured in high-strength stone at 15
minutes. A, Bubbles are caused by the release of hydrogen. B, No
bubbles are apparent because palladium hydrogen absorber is
included in the impression material.
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

 Addition silicones are as easy to handle as condensation silicones.
 Because there is the possibility of hydrogen release on setting, finely divided
palladium is added to some products to absorb the hydrogen and prevent
bubbles from forming on stone die surfaces.
 If a product does not contain a hydrogen absorber, an hour should pass before
pouring dies, and the impression should stand overnight before epoxy dies are
poured.
MANIPULATION
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

 Automatic mixers that provide quick, bubble-free mixes are available with
several products.
 Addition silicones can be electroplated with both copper and silver.
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

 Extrude (Kerr)
 Express (3M/ESPE)
 Aquasil (Dentsply Caulk)
 Genie (Sultan Chemists)
 Virtual (Ivoclar Vivadent)
 3 M Tm Express Tm Impression Material system. (3 M)
 3 M Tm Express Tm STD Putty. (3 M)
 3 M Tm Express Tm Impression Material Refills (3 M)
 3 M Tm Imprint Tm Monophase Impression Material system (3 M)
 3 m Tm Imprint II Impression Material system (3 M)
AVAILABLE AS
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

Latex gloves have been shown to adversely affect the setting of addition
silicone impressions.
Sulfur compounds that are used in the vulcanization of latex rubber gloves can
migrate to the surface of stored gloves.
These compounds can be transferred onto the prepared teeth and adjacent soft
tissues during tooth preparation and when placing tissue retraction cord.
SOME INFORMATION
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

They can also be incorporated directly into the impression material when
mixing two putties by hand.
These compounds can poison the platinum-containing catalyst, which results in
retarded or no polymerization in the contaminated area of the impression.
 Thorough washing of the gloves with detergent and water just before mixing
sometimes minimizes this effect, and some brands of gloves interfere with the
setting more than others.
Vinyl and nitrile gloves do not have such an effect
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

Residual monomer in acrylic provisional restorations and resin composite cores
has a similar inhibiting effect on the set of addition silicone materials.
The preparation and adjacent soft tissues can also be cleaned with 2%
chlorhexidine to remove contaminants.
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

 Hydrophilic polyvinyl siloxane
 These materials have been recently introduced to overcome the high surface
tension and incompatibility with the moisture.
 Hydrophobic nature causes difficulty in pouring the cast.
 To render the surface hydrophilic, the surfactant is added to the paste.
 This surfactant reduces the contact angle which increases wettability and
simplifies the pouring of gypsum model.
MODIFICATION
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

 The hydrophobic material have contact angle of approximately 95°, where as
that of hydrophilic material have contact angle of 30°-35° and has better
wetting .
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

 Vinyl siloxane ether
 It is combination of PVS and PE impression materials and having combined
benefit of both materials
 No bitter taste of polyether
 Hydrophilic in nature
 Good elasticity and elastic recovery
 It is having high tear strength, excellent dimensional accuracy and resistance
to deformation.
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

 It is most widely used for the crown and bridge impressions
 Cavity impressions of inlays and onlays
 Impressions for partial and complete dentures.
USES
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

 Produce highly accurate impressions
 Pleasant to handle and no disagreeable taste
 Excellent elastic recovery–99.93%
 Shorter setting time
 Dimensionally more stable as there is no elimination of byproducts
 Can be electroplated with silver or copper
 Multiple dye-pour is possible
ADVANTAGES
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

 More expensive with automatic mixing devices
 Shorter working time
 It may release hydrogen gas on setting and produce pin point voids in the
impression if absorbent is not present in the material.
 Hydrophobic material causes difficulty in obtaining cast/dye, without air
bubbles.
DISADVANTAGES
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

POLYETHER
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

POLYETHER
 This material was introduced in Germany is 1960.
 This was the first elastomer to be developed as an impression material only
unlike others, which were adapted from other uses.
 It was developed in an attempt to combine the good mechanical properties of
the polysulfides with the dimensional stability of the silicones .
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

DISPENSING
 It is dispensed as 3 pastes system, base, reactor and body modifier (thinner).
 It is available in 3 viscosities, i.e. light, regular and heavy bodies.
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

SETTING REACTION
 When the base paste is mixed with catalyst paste, the cation ring opening
addition polymerization occurs, the ionized form of sulphonic acid provides
the initial source of cation and in each stage of the reaction involves opening of
an aziridine ring and production of a fresh cation.
 Reaction is addition polymerization reaction without the formation of by-
products
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

 Since each polyether molecules have 2 imine terminal groups, individual
propagation reaction may produce simple chain lengthening reaction and cross-
linking.
 As the reaction proceeds, the viscosity increases and eventually relatively rigid
cross linked rubber is produced.
 Base imine terminated polyether + reactor sulphonic acid → polyether rubber
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

COMPOSITION
BASE
Imine terminated polyether of
moderately low molecular weight
Colloidal silica
Glycol ether phthalate
REACTOR
Ester derivative of aromatic sulphonic
acid
Colloidal silica
Glycol ether phthalate , Octyl phthalate
(thinner)
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

AVAILABLE AS
 Impression f (ESPE)
 Impregum Penta (ESPE)
 Permadyue Garant 2:1 (ESPE)
 Permadyne Heavy body (ESPE)
 Permadyne Light Body (ESPE)
 Permadyue Penta H (ESPE)
 Permadyne Penta L (ESPE)
 Impregum F,
 Permadyne (3M ESPE),
 Polyjel
 (Dentsply/Caulk)
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

MANIPULATION
 The manipulation of polyethers is similar to that of polysulfides and silicones.
 Equal lengths of base and catalyst paste are mixed vigorously and rapidly (30
to 45 seconds), because the working time is short.
 They are easy to mix.
 The impressions can be readily silverplated to produce accurate dies.
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

 Precautions should be taken to mix the material thoroughly and to avoid
contact of the catalyst with the skin or mucosa because tissue reactions have
been observed.
 A handheld gun-type mixer that provides quick, bubble-free mixes is available
for Permadyne Garant (3M ESPE).
 Also, an automatic mixing device (Pentamix, 3M ESPE) is available for use
with a polyether packaged in polybags (Impregum Penta).
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

USES
 In the preparation of crowns and bridges
 In cavity preparations for inlays and onlays
 In construction of partial and complete dentures.
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

ADVANTAGES
 Have pseudoplastic properties, that is, same mix can be used as a tray and
syringe material.
 Addition of thinner to the base and reactor pastes increases flow properties.
 These are dimensionally stable as there are no liberation of byproducts and less
polymerization shrinkage.
 Produce more accurate casts and permits multiple dye pours.
 Shorter setting time.
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

 Have less hydrophobic, hence better wetting and good casts are obtained.
 Long shelf-life-no objectional odour and less distortion on removal from
mouth.
 Cast pouring can be delayed for few hours even a week.
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

DISADVANTAGES
 Very expensive when compared with other elastomers
 High stiffness
 Low tear strength
 Electroplating is not easy
 Not available in complete ranges of viscosities
 Catalyst can be sensitive to the patients.
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

LIGHT ACTIVATED
POLYETHER
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

 DISPENSING :
 Available in 2 viscosities,
 light body supplied in disposable syringes and
 heavy body, packed in collapsible tubes.
LIGHT ACTIVATED POLYETHER (INTRODUCED
IN 1988)
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

 Visible light curing polyether urethane dimethacrylate elastomer resin
 Visible light cure photoinitiators camphoroquinone and photoaccelerators-
dimethyl aminoethyl methacrylate.
 Silicon dioxide-as fillers (It has refractive index close to that of the resin in
order to provide the translucency necessary for depth of cure)
COMPOSITION
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

 Excellent elasticity
 Command setting, infinite working time and short setting times.
 Very low volume shrinkage on setting
 The impression can be stored up to two weeks.
PROPERTIES
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

 Mixing is not required.
 Light body material is syringed into cavity preparation.
 The special transparent tray is loaded with heavy body material and in the
patients mouth.
MANIPULATION
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

 After the tray is seated in the mouth, both materials are cured simultaneously
using a visible light curing unit.
 The curing time is approximately 3 minutes.
 The light source is tungsten halogen bulb with a filter λ = 460–480 nm.
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

 Command setting, property, i.e. infinite working time and short setting time
 Excellent mechanical and clinical properties
 No mixing is required, hence no trapping of air or voids and
 less wastage.
ADVANTAGES
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

 Requires a special tray that is transparent to the visible light, to cure the
material.
DISADVANTAGES
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

PROPERTIES
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

HANDLING PROPERTIES
PROPERTIES POLYSULPHIDE CONDENSATION
SILICONE
ADDITION
SILICONE
POLYETHER
PREPARATION 2 pastes 2 pastes or paste
liquid
2 pastes 2 pastes
HANDLING simple simple simple simple
EASE OF USE fair fair good good
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

SILICONE
ADDITION
SILICONE
POLYETHER
PATIENT
REACTION
Unpleasant ,
stains
Pleasant ,
clean
clean Unpleasant ,
clean
EASE OF
REMOVAL
Easy Moderate Moderate Moderate to
difficult
SETTING TIME 8–12 6–8 3–7 4.5
WORKING TIME 5–7 3. 2–4.5 2.5
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

SILICONE
ADDITION
SILICONE
POLYETHER
STABILITY 1 h Immediate
pour
1 w 1 w kept dry
WETTABILITY
AND EASE OF
POURING
Excellent Fair Fair to good Good
DIE MATERIAL stone stone stone stone
ELECTROPLATIN
G
yes yes yes yes
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

SILICONE
ADDITION
SILICONE
POLYETHER
DISINFECTION fair excellent excellent fair
COST low moderate High to very
high
high
ELASTIC
RECOVERY %
94.5 -96.9 98.2 -99.6 99 -99.9 98.3 -99
FLEXIBILITY % 8.5 - 20 3.5 -7.8 1.3 -5.6 1.9 -3.3
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

SILICONE
ADDITION
SILICONE
POLYETHER
FLOW % 0.4 -1.9 < 0.10 <0.05 <0.05
SHRINKAGE, 24
HOURS %
0.4 – 0.5 0.2 -1.0 0.01 – 0.2 0.2 – 0.3
TEAR STRENGTH
g/cm
2240 - 7410 2280 - 4370 1640 - 5260 1700 - 4800
O’Brien Dental Materials & their Selection 4th edition
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

 RHEOLOGICAL PROPERTIES :
 All elastomeric impression materials exhibit shear-thinning
characteristics before setting.
 A pseudoplastic material displays decreasing viscosity with increasing
shear stress, and recovers its viscosity immediately upon a decrease in
shear stress.
 ELASTICITY AND VISCOELASTICITY:
 An impression material sustains some deformation as it is removed from
the mouth but it must rebound to its preremoval dimensions.
 The simplest model that demonstrates the viscoelastic behavior is a
Maxwell-Voigt model
SOME INFO
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

 keeping the time of applied force on the impression to a minimum will
result in the least amount of permanent deformation.
 This explains why removal of the impression should be done in a snap,
if possible, and a teasing or rocking method should be avoided
 TEAR STRENGTH:
 Low-viscosity impression materials are used in interproximal and
subgingival areas during impression making.
 The subgingival regions of the impression are often very thin and can
tear during impression removal, leaving a portion embedded within the
gingival sulcus
SOME INFO
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

 A tear-strength test measures the resistance of an elastomeric material to
fracture when subjected to a tensile force acting perpendicular to a
surface flaw.
 A quick snap in removing the impression usually increases the tear
strength, as the action increases the resistance of the material to
deformation
 DIMENSIONAL STABILITY:
 There are six major sources of dimensional change:
 (1) polymerization shrinkage,
 (2) loss of a condensation reaction by-product (water or alcohol)
SOME INFO
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

 (3) thermal contraction from oral temperature to room temperature,
 (4) absorption of water or disinfectant over a period of time,
 (5) incomplete recovery of deformation because of viscoelastic behavior,
and
 (6) incomplete recovery because of plastic deformation.
SOME INFO
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

Working time
• longest to shortest
• agar > polysulfide > silicones > alginate = polyether
Setting time
• shortest to longest
• alginate < polyether < agar < silicones < polysulfide
COMPARISON OF PROPERTIES
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

Stiffness
• most to least
• polyether > addition silicone > condensation silicone > polysulfide
= hydrocolloids
Tear strength
• greatest to least
• polysulfide > addition silicone > polyether > condensation silicone
>> hydrocolloids
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

Cost
• lowest to highest
• alginate < agar = polysulfide <condensation silicone < addition
silicone < polyether
Dimensional stability
• best to worst
• addition silicone > polyether > polysulfide > condensation silicone
> hydrocolloid
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

Wettability
• best to worst
• hydrocolloids > polyether > hydrophilic addition silicone > polysulfide >
hydrophobic addition silicone = condensation silicone
Castability
• best to worst
• hydrocolloids > hydrophilic addition silicone > polyether > polysulfide >
hydrophobic addition silicone = condensation silicone
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

MANIPULATION
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

 The steps to be followed while manipulating the elastomeric impression
materials are:
1. Selection of the materials
2. Preparation of custom/special trays
3. Proportioning and mixing
4. Impression techniques
5. Application of wetting agents (surface tension reducing agents) on the
impression (as it is hydrophobic)
6. Pouring of stone dies.
MANIPULATION
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

 The selection of the rubber impression material should be based on the clinical
usage of the material and the properties required.
SELECTION OF MATERIAL
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

 A special tray with spacer has to be
prepared with acrylic resins by
using the primary/preliminary cast
of the patients mouth.
 For putty elastomers perforated
stock trays or disposable trays can
be used.
PREPARATION OF CUSTOM/SPECIAL TRAYS
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

 Elastomers are not adhesive to the trays.
 Adhesion can be obtained by application of adhesives to the trays.
 For polysulphides, butyl rubber or styrene dissolved in chloroform or ketone
can be used.
 For polysilicones–polydimethyl siloxane and ethyl silicate can be used to
create a physical bond with the impression trays
ADHESION TO THE TRAY
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

 Three types of systems are available to mix the catalyst and base thoroughly
before taking the impression:
 Hand mixing
 Static auto mixing
 Dynamic mechanical mixing
MIXING
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

HAND MIXING
• The user should dispense the same lengths of materials onto a mixing pad or
glass slab .
• The catalyst paste is first collected on a stainless steel spatula and then spread
over the base paste.
• The mixture is then spread over the mixing pad.
• The mass is then scraped up with the spatula blade and spread uniformly back
and forth on the mixing pad.
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

• This process is continued until the mixed paste is uniform in color, with no
streaks of the base or catalyst appearing in the mixture.
• If one of the components is in liquid form, such as the catalyst for condensation
silicones, a length of the base is dispensed from the tube onto a graduated
mixing pad and drops of the liquid catalyst corresponding to the length of the
base are added.
• The two-putty systems available for condensation and addition silicone are
dispensed by volume using an equal number of scoops of each material
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

• The best mixing technique is to knead the material with one’s fingers until a
uniform color is obtained.
• When the catalyst is a liquid, as in the case of condensation silicones, this
kneading procedure with the fingers is applicable.
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

124
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

STATIC AUTO MIXING
• The base and catalyst are in separate cylinders of the plastic cartridge.
• The cartridge is placed in a mixing gun containing two plungers that are
advanced by a ratchet mechanism to extrude equal quantities of base and
catalyst.
• The base and catalyst are forced through the static-mixing tip containing a
stationary plastic internal spiral; the two components are folded over each other
many times as they are pushed through the spiral, resulting in a uniform mix at
the tip end
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

• Because one cylinder may be filled slightly more that the other, the first part of
the mix from a new cartridge should be discarded.
• The mixed material can be extruded directly into an injection syringe or into
the impression tray.
• Intraoral delivery tips can be placed on the end of the static mixing tip, and the
mixed material can be injected into and around the cavity preparation.
• The tip can be removed, and additional mixed material can be extruded into the
impression tray.
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

• The automixing systems have been shown to result in mixes with many fewer
voids than hand mixes.
• Although for each mix the material left in the mixing tip is wasted, the average
loss is only 1 to 2 mL, depending on the manufacturer’s tip
• whereas three to four times this much is wasted in a hand mix as a result of
overestimating the amount needed.
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

• Initially, automixing was used for low consistencies, but new designs of guns
and mixing tips allow all consistencies except putty to be used with this
system.
• Addition silicones, condensation silicon and polyethers are available with this
means of mixing.
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

DYNAMIC MECHANICAL MIXING
• The catalyst and base are supplied in large plastic bags housed in a cartridge,
which is inserted into the top of the mixing machine.
• A new, plastic mixing tip is placed on the front of the machine, and when the
button is depressed, parallel plungers push against the collapsible plastic bags,
thereby opening the bags and forcing material into the dynamic mixing tip.
• This mixing tip differs from auto mixing in that the internal spiral is motor
driven so it rotates
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

• Thus mixing is accomplished by this rotation plus forward motion of the
material through the spiral.
• In this manner, thorough mixing can be ensured and higher viscosity material
can be mixed with ease.
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

 Elastomeric impression materials are typically supplied in several viscosities
to accommodate different techniques for impression making.
 Following are the techniques :
• Multiple-Mix Technique
• Monophase Technique
• Putty-Wash Technique
IMPRESSION TECHNIQUES
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

 Double mix single impression technique or syringe tray method.
 Tray used is a special tray and consistencies used are heavy body as a
tray material and light body as a syringe material.
 This technique can be used with polysulphides, polysilicones,
polyethers.
 This method is referred as multiple mix technique because two separate
mixtures are required with two separate mixing pads and spatula
MULTIPLE MIX TECHNIQUE
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

133
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

 STEPS :
 The light body material is first mixed and injected into the impression
area.
 Meanwhile the heavy body material is mixed and loaded on the tray
and seated over the light body material.
 The light and heavy body materials set together to give a single
impression in which light body material recording all the finer details
and supported by the heavy body material.
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

 When both the materials set together, the impression is removed with a
steady force to minimise permanent deformation and to maximize tear
strength.
 The impression is cleaned with running tap water, disinfected and the
excess water is shaken off and the gentle stream of air is blown to
remove the residual moisture.
 Cast/dye is prepared by pouring type IV dye stone material or type V
dye stones.
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

 ADVANTAGES :
 Less impression material is needed than for the stock trays.
 Trays are used for single patient, so sterilization is not needed.
 Uniform thickness of impression material minimizes distortion
resulting from thermal and curing shrinkages.
 Produce dimensionally accurate and stable impression.
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

 DISADVANTAGES :
 Construction of special trays is time consuming
 The monomer may be sensitive to some patients
 These techniques are mainly used for tooth cavity impression for
inlays, onlays, crowns, bridges, etc.
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

 Single mix single impression technique.
 A special tray is used, with rubber adhesive coating.
 Materials used are of single consistency having pseudoplastic property
(regular or light body materials can be used both as a tray and syringe
material).
 This technique is used with addition polysilicones and poly ethers as
they have pesudoplastic properties (monophase materials).
MONOPHASE TECHNIQUE
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

 The material is mixed and one part of it is loaded into the tray and other
part into the syringe.
 The material is extruded from the syringe onto the prepared tooth
surface.
 Keeping the tip within the material, the syringe is slowly moved all
over the prepared area so that the material covers the entire prepared
and some of the nonprepared surfaces.
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

 The tray is then placed into the mouth to record the impression. The
impression tray generally used for this technique is custom-made resin
tray with uniform spacing of 2–4 mm
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

 Reline technique: Double mix double impression technique, or Putty
wash technique
 Tray used is adhesive treated perforated stock tray Consistencies
required are:
 Putty material for primary impression
 Light body for secondary impression or corrective wash
impression.
PUTTY WASH TECHNIQUE
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

 This technique is widely used with condensation and addition
polysilicones.
 It is a two stage method in which the primary impression is taken with
putty material and secondary impression is recorded with light body
materials
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

143
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

144
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

 STEPS:
Primary impression :
• Putty material is placed in a perforated stock trays and the impression is
taken before (cavity preparation or crown cutting).
• Space for the wash material is provided by either cutting away some of
the putty material from original impression or by using a spacer
between the putty and the teeth when recording the primary impression.
• When the putty material has set, impression is removed and washed.
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

 STEPS:
Secondary/corrective wash impression :
• After the cavity preparation, the light body material is mixed and
injected into the cavity preparation.
• The tray is reinserted (to act as a custom tray for light with primary
impression body) and held gently until the wash material sets.
• The impression is removed with a steady force, washed, disinfected,
dried and dye is poured.
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

 ADVANTAGES :
 Rapid curing of putty elastomer, that is, the primary impression need to
be held in the mouth only for few minutes.
 Properly used putty wash technique can produce impression with
accuracy comparable to that of the multiple mix procedure.
 Stock trays can be used which eliminate time and expense of
fabricating custom trays.
 Metal stock trays are rigid and not susceptible to distortion.
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

 DISADVANTAGES :
 It is technique sensitive.
 Inadequate relief space for wash material.
 Metal trays must be sterilized.
 Putty is quite expensive.
 More impression material is required.
 This technique is widely used in recording impression for crowns and
bridges and prepared cavities for inlays and onlays.
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

COMMON CAUSES FOR FAILURES
OF ELASTOMERIC IMPRESSION
MATERIALS
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

• Incomplete polymerization
due to premature removal, and
improper mixing
• Too high accelerator/base
paste ratio
• Too rapid polymerization, by
high temperature or humidity.
ROUGH OR UNEVEN SURFACE
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

• Rapid polymerization
preventing flow
• Incorporation of air during
mixing Inadequate flow.
BUBBLES
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

• Poor adhesion to the tray and detachment of impression.
• Special tray, gets distorted, if the resin has not completely polymerized
• Delay in seating of tray causes the mix start polymerizing before seating.
• Too thick and non uniform impression material.
• Too much pressure applied continuously even after setting commence.
• Movement of tray during polymerization.
• Premature and improper removal of the tray from the mouth.
DISTORTION
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

• Inadequate cleaning of impression
• Excess water or wetting agent left over the impression
• Too high W/P ratio and improper mixing of the dental stone mix.
• Premature removal of the stone cast
ROUGH OR CHALKY SURFACE
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

• Delay in pouring the cast for
polysulphide or condensation
polysilicones.
• Too early pouring the cast (before
20–30 min after taking impressions)
in case of additional polysilicones
and polyethers.
DISTORTION
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

DISINFECTION
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

• After removal from the patient’s mouth, all impressions should be disinfected
since they are contaminated by the oral/body fluids.
• Depending on the material’s tendency to absorb moisture, the impression is
either sprayed with the disinfectant and stored in a plastic bag or immersed in
the disinfectant solution.
• Recommended disinfectant solutions for elastomers except polyethers are
glutaraldehyde 2%, chlorine compounds (1:10 dilution of sodium
hypochlorite), complex phenolic, and phenolic glutaraldehyde compounds.
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

• disinfection of polyether impressions by immersion is not recommended except
for very short (2 to 3minutes) times in chlorine compound disinfectants.
• Also, the surface quality of high-strength stone dies poured against the
impressions is acceptable.
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

• ADDITION OF SURFACTANT :
• The use of a more hydrophobic impression material may lead to a high frequency of voids
in the cast. It is possible to spray a surfactant on these hydrophobic impressions prior to
pouring with gypsum mixtures. A nonionic surfactant such as the one based on a block
copolymer of siloxane and ether groups may be added to the bulk of the material during
the manufacturing process. The siloxane group is hydrophobic, and this property facilitates
dispersion of the surfactant in the bulk of PVS. The ether group is hydrophilic and is
oriented toward the surface when the surfactant migrates by diffusion to the surface region.
This type of PVS is called a hydrophilized PVS.
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

• Addition polysilicones and polyethers are used for bite registration for checking
the occlusal relationships in the fabrication procedures of dentures (refer bite
waxes and ZnOE pastes).
• Addition polysilicones having similar compositions of light bodies are supplied
in automixing cartridges.
• This has the advantages of adequate flow, negligible resistance, short, suitable
setting time, stiffness, good elastic recovery and dimensional stabilities.
• These are the requirements of bite registration materials.
BITE REGISTRATION ELASTOMERS

REVIEW OF LITERATURE
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

• The purpose was to evaluate the dimensional stability and the detail reproduction
of five current elastomeric impression materials in vitro.
• The materials examined were: 3 different polyether impression materials, a vinyl
polysiloxane impression material, and a vinyl polyether silicone impression
material. All impression materials were of a medium viscosity.
Aivatzidou K, Kamalakidis SN, Emmanouil I, Michalakis K, Pissiotis AL.
Comparative Study of Dimensional Stability and Detail Reproduction of
Reformulated and Nonreformulated Elastomeric Impression Materials. Journal of
Prosthodontics : Official Journal of the American College of Prosthodontists. 2020

• One stainless steel die was fabricated according to the ANSI/ADA specification
no.19 criteria.
• Twenty impressions of this die were made for each material.
• Dimensional accuracy and surface detail were evaluated 24 hours after making
the impressions using a measuring microscope.
• The data were analyzed using Welch's analysis of variance, Games‐Howell
Post‐Hoc, and the Pearson's chi‐square tests (α = 0.05).
• Result observed was that the highest dimensional change was recorded for the
vinyl polysiloxane impression material, with a mean percent value of –0.09 ±
0.02% (p < 0.001).

• The lowest dimensional change was recorded for the Monophase polyether
material with a mean percent value of –0.03 ± 0.01% (p < 0.038).
• The best surface detail reproduction results were obtained using the Monophase
polyether material (90% acceptable impressions), with no significant differences
(χ² [4] = 3.86, p = 0.483) observed between the Monophase and the rest
impression materials.
• Conclusion drawn was that all impression materials demonstrated acceptable
surface detail reproduction with no significant differences between them.

• The aim of the study was to assess the disinfection potential of radiofrequency
glow discharge (RGD) by microbiological studies.
• material and methods used were , disinfection potential of RGD on addition
silicone (Reprosil, Dentsply, Milford DE, USA) was assessed.
Mathew S, Alani MM, Nair KN, et al. Radiofrequency Glow Discharge as a Mode
of Disinfection for Elastomeric Impression Materials. The Journal of
Contemporary Dental Practice. 2017 Feb;18(2):131-136..

• Total sample size was 20.
• Samples were divided into two groups of 10 each.
• Group I - control group and group II -RGD-treated group.
• Main groups were subdivided into subgroups A and B.
• Data collected were analyzed.
• Results stated that the RGD-treated samples were found to be culture sterile
which meant that there were no signs of growth of any organisms, thus proving
the disinfection potential of RGD.

• The study concluded that the RGD is a very rapid and handy device, which can
disinfect saliva contaminated elastomeric impression material surfaces.

CONCLUSION
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

 A good impression is an exact replica of each prepared tooth and should include
adequate amount of the unprepared surfaces adjacent to the margin.
 Elastomeric Impression technique and material should be selected on the basis
of biologic factor dictated by the anatomy and the physiology of the mouth.
 Even though there are innumerable techniques and procedure for impression
making ,it is the responsibility of the dentist to select the best possible procedure
based on sound knowledge , for achieving the best possible result for the patient.
CONCLUSION
DEPARTMENT
OF
PROSTHODONTICS,
CROWN
AND
BRIDGE.
DDCH,
UDAIPUR

• Anusavice, K., Phillips, R., Shen, C. And rawls, H., N.D. Phillips' science of dental materials
12th edition.
• Bhat sv . science of dental materials : clinical applications 2nd edition. 2013
• Mahalaxmi S . materials used in dentistry . 1st edition. 2013
• John F. Mccabe, angus W.G. Walls. Applied dental materials . 9th edition. 2017
• Gladwin M, bagby M. Clinical aspects of dental materials: theory, practice, and cases. 4th ed.
2013.
• William J O'Brien .Dental materials selection .3rd edition
• John m. Powers, john C. Wataha .Dental materials: properties and manipulation, 9th edition
• Aivatzidou K, Kamalakidis SN, Emmanouil I, Michalakis K, Pissiotis AL. Comparative Study
of Dimensional Stability and Detail Reproduction of Reformulated and Nonreformulated
Elastomeric Impression Materials. Journal of Prosthodontics : Official Journal of the
American College of Prosthodontists. 2020
• Mathew S, Alani MM, Nair KN, et al. Radiofrequency Glow Discharge as a Mode of
Disinfection for Elastomeric Impression Materials. The Journal of Contemporary Dental
Practice. 2017 Feb;18(2):131-136..

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