S 5 elastomeric imp. and tech

Dr. Neha Verma
2nd year PG
Department of Conservative Dentistry and
Endodontics
ELASTOMERIC IMPRESSION MATERIALS
AND
IMPRESSION TECHNIQUES

CONTENTS
 Introduction
 Definition
 History
 Classification
 Elastomers
 General properties
 Tissue management
 Manipulation
 Impression making
 Disinfection
 Common failures with elastomers
 Summary

 An impression is an imprint or negative likeness.
 It is made by placing some soft, semi-fluid material in the mouth and
allowing the material to set.
 Depending on the material used, the set impression will be either hard or
elastic.
 The impression materials most frequently used for cast restorations are
elastic when removed from the mouth.
 From this negative form of the teeth and surrounding structures, a positive
reproduction, or cast, is made.
INTRODUCTION
Fundamentals of fixed prosthodontics Shillinburg 4th ed

 IMPRESSION MATERIAL : Any substance or combination of substances
used for making an impression or negative reproduction.
 ELASTOMER : A polymer that has a glass transition temperature that is
below its service temperature (usually room temperature); these materials
are characterized by low stiffness and extremely large elastic strains.
 ELASTOMERIC IMPRESSION MATERIAL: A group of flexible
chemical polymers that are either chemically or physically cross-linked;
generally, they can be easily stretched and rapidly recover their original
dimensions when applied stresses are released.
DEFINITION
- GPT -9

1950 : A group of synthetic rubbery materials called elastomers ( Polysulphides
and Condensation Silicones), which are capable of making impressions
of both soft and hard tissues are developed.
1960s : Polyether impression material developed in Germany
1970s : Addition silicone was introduced as a dental impression material
1988 : Latest addition and light cure elastomers
1990-2000 : New auto devices and delivery systems
HISTORY
Philips science of dental materials 12th ed

An impression for a cast restoration should meet the following requirements:
 It should be an exact duplication of the prepared tooth, including all of the
preparation and enough uncut tooth surface beyond the preparation to allow
the dentist and technician to be certain of the location and configuration of the
finish line.
 Other teeth and tissue adjacent to the prepared tooth must be accurately
reproduced to permit proper articulation of the cast and contouring of the
restoration.
 It must be free of bubbles, especially in the area of the finish line and occlusal
surfaces of the other teeth in the arch.
Fundamentals of fixed prosthodontics Shillinburg 4th ed

Representative commercially available elastomeric impression materials.

 Soft and rubber-like & known as elastomers or synthetic rubbers
 As per ADA Sp. No.19- non-aqueous elastomeric dental impression
materials
 Liquid polymers when mixed with a suitable catalyst are converted into solid
rubber at room temperature.
I. According to chemistry
 Polysulphides
 Condensation polymerizing silicone
 Addition polymerizing silicone
 Polyether
ELASTOMERS
Materials used in dentistry. Mahalaxmi- 1st ed

II ADA Classification
Based on selected elastic properties & dimensional changes(sp no.19) :
III. According to Viscosity (ISO 4823)
1) Light body or syringe consistency
2) Medium or regular body
3) Heavy body or tray consistency
4) Very heavy body or putty consistency
Type Max permanent
deformation
Max flow in
compression
Max dimensional
change in 24 hrs
I 2.5 0.5 -0.5
II 2.5 0.5 -1
III 5.5 2 -0.5

 Excellent reproduction of details
 Generally hydrophobic
 Good elastic properties
 Excellent tear strength
 High coefficient of thermal expansion
 Electroplatable : silver or copper plated
 Extended shelf-life : 2 years
 Generally higher cost
 Requires tray adhesive and mechanical interlocking.
GENERAL PROPERTIES

SUPPLIED AS
 All elastomers –two paste systems (base and catalyst)
 Putty consistency – supplied in jars
USES
Impression material for all applications including
 Fixed partial dentures
 Dentulous and edentulous impressions
 Border moulding of special trays(polyether)
 Bite registration
 As duplicating material for refractory casts

working & setting time
Curing of polyether is less sensitive to temperature
 modification of base/accelarator paste
 thinner - WT, slight ST
temperature -
Viscosity
Humidity

 Stiffness
polysulfide
Condensat
ion silicon
Addition
silicon
polyether
Addition
silicone
Condensa
tion
silicone
polyether polysulphi
de
 Relative amount of permanent deformation in compression following strain
induced during removal increases in the following order

 Ideally-should flow freely and wet the tissue as it is being injected to achieve
adaptation - then resist flow away from the intended surface areas.
 This will facilitate spreading of heavy-body material on the impression tray and
retain it in the tray. This phenomenon is called shear thinning
 Polyether – rigid – problem preparation on periodontally weak tooth - # of dies &
tearing of impression material at the sulcus
RHEOLOGICALPROPERTIES
 Polymerization shrinkage
 Loss of byproduct
 Thermal contraction from oral temperature to room temperature
 Imbibitions
 Incomplete recovery of deformation(visco elastic nature)
 Pour within 30 mins – polysulfide & condensation silicon
DIMENSIONALSTABILITY

 The amount of force needed to tear a specified test specimen divided by the
thickness of the specimen is called the tear strength.
 The ranking of tear strength from the lowest to highest of the impression materials
is as follows
silicones polyether polysulfide
TEAR STRENGTH

 Probability of allergic reactions is low
 Polysulfide has the lowestcell death count
 Polyether has the highest cell death count ,toxicity and contact dermatitisamong the
class.
 Themostlikely problem is lodgment of impression material in gingival sulcus
resulting in severe inflammation,
BIOCOMPATIBILITY

polysulfide 2 yrs
Condensation silicon stannous octoate oxidizes
Orthoethyl silicate is not stable in
presence of tin ester
Addition silicon 1-2 yrs
Poly ether > 2yrs
Cool, dry environment Tubes
always tightly sealed
Container closed
SHELF LIFE
STORAGE

First synthetic elastomeric impression material
Also known as MERCAPTAN or THIOKOL
Mode of supply
- Collapsible tubes
- One labeled Base paste and
- Other labeled Accelerator paste
Consistencies
- Light body(syringe or wash)
- Medium body (regular)
- Heavy body
POLYSULFIDE

Composition Function
Base paste •Polysulphide prepolymer
with terminal and pendanthiol
(-SH groups)-80-85%
•Plasticizer – di-n-butyl
phthalate
•Inert filler- possible chalk or
titanium dioxide- 16-18%
Polymerized and cross
linked to form rubber
 Tocontrol viscosity
Togive ‘body’ control
viscosity and modify
physical properties
Catalyst paste •PbO2 / other alternative
oxidizing agent-60-68%
•Sulphur-0.5%
•Inert oil- paraffin type/
di-n-butyl phthalate
Toreact with thiol
groups- setting
 Setting reaction
 Toform a paste with
PbO2 andsulphur
COMPOSITION

Polysulfide
prepolymer
Lead
dioxide
polysulphide water

 Working time – 4-7 mins
 Setting time – 7-10 mins
 Lowest viscosity
 excellent reproduction of details
 Dimensional stability -
 Percent contraction (at 24hrs) – 0.40%-0.45%
 Shrinkage is due to loss of polymerization byproduct such as water
 Deformation on removal
 caused by rocking the impression while removal; it should be removed with a single
swift pull
 High tear strength – 2500-7000 gm/cm2
 Biocompatibility – lowest cell death count
 Moderately hydrophilic
 Unpleasant odor and taste
 Can be electroplated with copper sulphate
PROPERTIES

ADVANTAGES DISADVANTAGES
- High tear strength
- Long working time
- Established precision
- Economic
- Extensive shelf life
- Less hydrophobic
- Dimensionally unstable-Unacceptable odor
- Untidy and stains clothing
- Long setting time
- Least elastic recovery
- Subsequent pours are less accurate.

 First type of silicone impression material
 Also known as conventional silicone’
 The setting occurs in room temperature so called as RTV silicones (room
temperature vulcanization)
Mode of supply
 Collapsible tubes
 Base paste
 Accelerator paste / liquid
 Putty is supplied in jars
Consistencies
Low, medium, high, and very high (putty) consistencies
CONDENSATION SILICONES

COMPOSITION
Paste •α- ω hydroxyl-
terminated polydimethyl
siloxane (liquid silicon
prepolymer)
•Inert filler - silica
Undergoes cross
linking to form rubber
Gives ‘body’,
controls viscosity &
modifies physical
properties
Liquid •Alkyl silica – tetra
ethyl silicate
•Tin compound – dibutyl
tin dilaurate/ tin octoate
Cross linking agent
Reaction catalyst

Dimethyl
siloxane
Tetra ethyl
orthosilicate
Silicon
rubber
Ethyl
alcohol
Stannous octate

PROPERTIES
 Working time- 2.5 – 4 mins
 Setting time – 6-8 mins
 Tear strength – 2300-2600 N/m
 % contraction at 24 hrs- 0.38-0.60%
 Hydrophobic
 Can be electroplated with silver and copper
 Stiffer and harder than polysulfide
 The ethyl alcohol formed evaporates gradually leading to shrinkage &
instability. So a condensation silicone should be poured as soon as
possible after removal from the mouth.

-
 Clean and pleasant
 Good working time
 Easily seen margins
 High polymerization shrinkage
 Volatile alcohol byproduct
 Low tear strength
 Hydrophobic
 Pour immediately

Also knownaspolyvinyl siloxane orvinyl polysiloxane
Mode of supply
Collapsible tubes
Base paste and
Accelerator paste
Putty is supplied in jars
Consistencies
Light body (syringe or wash)
Medium body (regular)
Heavy body
Putty
ADDITION SILICONES

COMPOSITION
Base paste •Poly(methyl hydrogen Undergoes cross
siloxane) linking
• Other siloxane
prepolymers
• Fillers- colloidal silica controls viscosity
35-75%
Accelerator •Di vinyl polysiloxane
prepolymers
•Platinum salt
(chloroplatinic acid)
• Palladium
• Retarders
• Fillers
Cross linking agents
catalyst
Hydrogen absorber

Polymethy
lhydrosilo
xane
Divinylpoly
siloxane
Chloropl
atinic
acid
Silicon
rubber

PROPERTIES
 Working time – 2-4 mins
 Setting time – 4-6.5 mins
 Tear strength – 1500-4300 N/m
 Percent contraction- 0.14-0.17%
 Pseudo plastic
 Exhibits lowest permanent distortion

 Contact of polyvinyl siloxanes with latex gloves should be avoided
 Especially true when handling and placing gingival cords
 Mechanism
- Migration of particulate sulfur and sulphur chloride compounds to the
surface and are transferred to prepared teeth and adjacent soft tissues
- When mixing by hand, mechanism of inhibition is thought to be
contamination of chlorplatinic acid catalyst with free sulfur left in glove
- Residues from acrylics,methacrylates and petroleum jelly lubricants may
interfere with setting reaction of material
COMPLICATION WITH LATEX GLOVES

PREVENTION
- Use vinyl or nitrile gloves to eliminate the problem
-Preparations should be cleaned after temporary prosthesis before
making final impression
- Avoid handling retraction cords with latex gloves
• Contact of internal surface of impression with gloved hands :-
- Failure of the material adjacent to the tray to polymerize
- Separation of the tray from the impression material

 Highly accurate
 High dimensional stability
 Pleasant to use
 Short setting time
 Auto mix available
 Hydrophobic
 Expensive
 Hydrogen gas evaluation in some
materials
 Sulfur contamination by latex glove

First elastomer to be developed primarily to function as
an impression material
Mode of supply
Collapsible tubes
Base paste
Accelerator paste
Third tube containing thinner may be supplied
Consistencies
Light bodied(syringe or wash)
Medium bodied (regular)
Heavy bodied
POLYETHER

COMPOSITION
Base paste
(large tube
•Imine-terminated
prepolymer
•Inert filler- silica
•Plasticizer-
phthalate
Cross linked to
form rubber
Togive body’
control viscosity
and physical
properties
Toaid mixing
Catalyst paste
(small tube)
•Ester derivative
of aromatic
sulphonic acid
•Inert filler – silica
•Plasticizer-
phthalate
Initiate cross
linking
Toform paste

polyether
Sulfonic
ester
Cross linked rubber

PROPERTIES
 Working time – 3 mins
 Setting time – 6 mins
 Tear strength – 1800- 4800 N/m
 Percent contraction – 0.19 – 0.24%
 Least amount of distortion
 Pseudo plastic
 Biocompatibility – contact dermatitis

 Dimensional stability
 Accuracy
 Shorter setting time
 Automix available
 Set material very stiff
 Imbibition
 Short working time.
 Allergic hypersensitivity in some
cases.

EXA'lence™ VPES Impression Material
(GC America )
• EXA'lence is the new generation of Vinyl Polyether Silicone (VPES) Impression
Material.
• Intrinsically hydrophilic with optimal flow and high tear strength,

• For the elastomeric impression materials, the crevice needs to be opened to
0.2-0.3 mm to allow accurate detailed reproduction.
• This can be achieved by surgical widening or mechanical displacement with or
without chemical adjuncts.
1) Surgical
2) Mechanical displacement
3) Chemo- mechanical
SURGICALWIDENING
• Electro surgery unit
• Rotary instrument
• Laser
Tissue managementTISSUE MANAGEMENT

Ectrosurgical tip for
gingival troughing.
 Specific probe
 Frequency : 3-4MHz
 Short metal projection: design helps to prevent
contact with the adjacent teeth as a result of the
insulation, and the short tip limits the depth of its
use in the crevice
 The heat generation helps to cauterize the cut
tissue and reduces bleeding
 Care must be taken to keep the tip moving whilst
activated (0.7 m/sec ) in order to prevent an
excessive temperature rise at least 5 sec should be
allowed before working in the same area again.
ELECTRO SURGERY UNIT
Stewardson DA. Trends in indirect dentistry: 5. Impression materials and techniques. Dental update. 2005 Sep
2;32(7):374-93.

ROTARY GINGIVAL CURETTAGE
( GINGITAGE OR GENGITAGE)
• Removal of the crevicular lining with a high-speed diamond
(tapered fissure) bur directed around the tooth within the
gingival crevice, at the same time as the preparation margin is
prepared.
• Least cost
• In interproximal areas: there is a high probability of
contacting the adjacent tooth surfaces and permanently
marking them. encourage caries, and cause sensitivity.
SOFT LASERS : can vaporize superficial tissues and widen the gingival crevice surgically
for impression taking. Overheating of the tissues with electrosurgery or laser can cause pulp
death and alveolar bone necrosis.
These methods should be avoided :
Gingivae are thin and friable, as significant recession may then be likely.
Tabassum S, Adnan S, Khan FR. Gingival retraction methods: a systematic review. Journal of Prosthodontics. 2017
Dec;26(8):637-43.

Cords are
• Twisted
• Knitted or braided.
• Twisted cords have a tendency to unravel so the latter two types of cord are
preferable. Ultrapak, a braided cord, is available in a range of sizes :
(smallest to largest diameter: 000, 00, 0, 1, 2, 3).

CORD PACKING INSTRUMENT
 The instrument can also be dual-ended, with working edges at different orientations to facilitate the
insertion of the cord encircling the tooth, without having to change hand positions or instruments. This
design also prevents hindrance in the field of vision.
 Working end should be thin enough to pack the cord into the sulcus
efficiently, but not sharp enough to initiate bleeding from the sulcus
wall or cause any perforation
 The smooth roundended instrument is mostly used for packing twisted cord
 The serrated type is used for the braided variety, prevents the slippage of the cord
during placement,
 Disadvantage : fraying of the cord if not used cautiously
Dec;26(8):637-43.

CORD PACKING TECHNIQUE
 It is recommended that the packing of the retraction cord be initiated from
the inter-proximal area.
 This can be done with the help of a periodontal probe and gentle pressure as the inter-
proximal gingival is thin and delicate, with minimal depth of gingival sulcus.
 There are two broadly used techniques for packing retraction cord in the gingival sulcus
depending on the :
- Clinical situation
- Health of the gingival tissues
- Depth of the gingival sulcus
- Pacement of the margin of the preparation on the tooth structure
A survey by Sorensen et al has shown that 98% of prosthodontists use cords
out of which 48% use a dual cord technique and 44% use a single cord technique.
Dec;26(8):637-43.

 Used when there is little or no haemorrhage from the gingival sulcus, and the preparation
margins on the tooth are either gingival or slightly subgingival.
SINGLE CORD TECHNIQUE
DOUBLE CORD TECHNIQUE
 Smaller diameter cord soaked with haemostatic agent : some lateral
tissue displacement but primarily controlling haemorrhage.
 The second larger diameter cord is then packed into the sulcus,
causing lateral tissue displacement
 The first deeper placed cord stays in place when the impression is
made, after removal of the top, larger diameter cord.
 Care must be taken not to cause drying of the retraction cords, as
they would then adhere to the gingival tissue and cause haemorrhage
when removed
Dec;26(8):637-43.

Phatale et al - epithelial attachment sustains injuries at a force of 1 N/mm2, while it
ruptures at 2.5 N/mm2, which is almost the same force required to place the
retraction cord.
CORD POSITIONING FORCE
CORD RETRACTION TIME
• The recommended time according to several studies ranges from 1–30 min
• If the cord is placed for 2 min , the sulcus width is reduced to 0.1 mm within 20 sec of
cord removal.
• On the other hand, if the retraction cord is placed for a longer time, this could result
in damage to the gingival tissue and recession.
• Gingival retraction cords are placed under the margin around the tooth for at least 5
min before making impressions.

• The single cord technique, the retraction cord is left in place for at least 4 minutes as, 4 minutes is
needed to adequately open the gingival sulcus and that longer times are not significantly better.10
• The single cord technique may be used when there is excellent gingival health (3mm pocket or
less).
• The largest diameter cord that can be inserted gently into the sulcus should be used.
• Excessive forces could cause trauma leading to gingival recession. In a deep sulcus, the tissue can
collapse over the single cord thus preventing proper tissue reflection.
• If there is gingival inflammation, removal of the single cord can elicit gingival hemorrhage.
• In the double-cord technique, After a minimum of 4 minutes, it is removed while the first small
diameter cord is left in place during the impression to prevent sulcular seepage and hemorrhage,
and for continued gingival displacement during the impression procedure.
https://iits.dentistry.utoronto.ca/impression-technique-for-indirect-
restorations Laura tam

Dislodging of placed cord with
simple vertical packing technique
Rotating the packing instrument ,helps the
previously placed cord be in place
Using two instruments walk around the tooth, to hold seated cord in place
2;32(7):374-93.

Disadvantages of use of retraction cord:
 Time consuming
 Traumatic
 Gingival recession after healing
 Bleeding after removal
 As an alternative to the retraction cords, different cordless systems are
developed.
 They usually contain pastes and gels in a form suitable for injection in the sulcus.
 They are considered to be less traumatic and with less histological damage than
cord systems

1) VASOCONSTRICTORS
a) Epinephrine
b) Nor–epinephrine
2) BIOLOGIC FLUID COAGULANTS
a) 15.5–20% Ferric sulfate
b) 100% Alum
c) 15−25% AlCl3
d) 10% Aluminium potassium sulfate
e) 15−25% Tannic acid
3) SURFACE LAYER TISSUE COAGULANTS
a) 8% ZnCl2
b) Silver nitrate
CHEMICALADJUNCTS
Dec;26(8):637-43.

Shaykhah Othman AlOthman, et al. “A Review on Hemostatic Gingival Retraction Agents and their Effect on
Prosthodontic Treatment Procedures”. EC Dental Science 18.7 (2019): 1484-1490.

Shaykhah Othman AlOthman, et al. “A Review on Hemostatic Gingival Retraction Agents and their Effect on
Prosthodontic Treatment Procedures”. EC Dental Science 18.7 (2019): 1484-1490.
Epinephrine syndrome” (tachycardia, rapid respiration, elevated blood pressure,
anxiety, and postoperative depression)

 Hand mixing
 Static mixing
 Dynamic mechanical mixing
MANIPULATION

STATIC MIXING
 When the trigger is pulled, the plunger is driven forward so
that the base and catalyst pastes are forced from the
cartridge into the mixing tip .
 The pastes pass through the bore and exit the nozzle as a
uniform mixed paste. Four different sizes of mixing tips are
shown; the more viscous the material, the larger is the
mixing tip that should be used. Syringe tips can be fit to the
nozzle to deliver the mixed paste directly to the prepared
teeth
 The base and catalyst are first injected into the respective barrel.
A plunger then forces the material through a smaller static
mixing tip. It can deliver the light body material directly onto
the abutment

 The motor-driving mechanism forces the material into the mixing tip and makes the impeller (insert)
inside the tip rotate. The function of the impeller is only to mix the material.
 Both polyether and addition silicone impression materials of various viscosities are available with
this dispensing system.
DYNAMIC MECHANICAL MIXING

Impression Techniques
There are various techniques for making fixed partial denture (FPD)
impressions, those are:
I. Putty-wash impression
II. Dual-phase impression
III. Mono-phase impression
IV. Hydrocolloid laminate technique
V. Copper-band impression technique
VI. Impression using vacuum-adapted splints
VII. Impression using preformed crown shells
VIII. Dual-arch impression technique
IX. Functional check bite impression
X. Matrix impression system
XI. Cast impression coping technique
XII. Digital impressions

IMPRESSION TECHNIQUES
 MULTIPLE- MIX TECHNIQUE
 PUTTY WASH TECHNIQUE
 MONOPHASE TECHNIQUE
 TRIPLE TRAY TECHNIQUE
 According to the tray used  According to mixing technique
 CUSTOM TRAY
IMPRESSIONS
 STOCK TRAY
IMPRESSIONS
2;32(7):374-93.

 Impression trays classified as :
A) Stock trays.
B) Custom trays
 Stock trays : used to take primary impressions and come in a range of sizes
and shapes, and can be plastic or metal
Available in various forms :
 Perforated
 nonperforated
 The flexibility of the stock tray may result in distortion impression.
 It also tends to result in pulling away of the impression material from the tray
during removal.
According to the TRAY used

CUSTOM TRAYS
 Customized trays made of acrylic, specifically conforming to the arch form of individual
patients.
 Dimensional changes that occur during polymerization of the elastomers are directly
proportional to the thickness of the material. Custom made trays provide uniform and
minimal thickness of the material. Stock trays result in uneven distribution and thickness
of the material resulting in more dimensional changes.
 The rigidity of the custom tray and uniform thickness of the material allow very minimal
distortion of the impression during removal.
 Uniform thickness of the impression material helps in conserving the volume of the
material required and thus reducing the cost of the impression.
 Much less discomfort to the patient as compared to the bulky stock tray with more
material.

 Reduce the quantity of material required to make impressions
 Dimensional changes attributed to the materials are minimized.
 Allows a uniform distribution of impression material between the tray and the object,
which also improves accuracy.
 Especially true for polysulfide impression material.
 The use of custom trays for polyether and addition silicone impressions is not critical,
since these materials are stiffer and have less polymerization shrinkage than the
polysulfide material.
Note :
 Less material in a custom tray reduces the compressibility of the impression, which can
make removal of the impression tray more difficult.
 When severe undercuts are present, the use of a custom tray should be avoided.

Replicating Materials—Impression and Casting. (2012). Craig’s Restorative Dental Materials, 277–325.
 The double-impression technique is suitable for use with a stock impression
tray, because the preliminary impression serves as a custom tray.
 With the monophase and simultaneous dual-viscosity technique, a slight
improvement in accuracy results when a custom-made tray is used because it
provides a uniform thickness of impression material.

 Multiple mix technique
 A syringe material (light body) and a tray material (heavy body) are used in
this technique.
 Usually, the two groups of materials are mixed simultaneously, each by a
different person.
 Low-consistency material is injected with a syringe into critical areas & the
high-consistency material is mixed & placed in an impression tray.
 After injecting the low viscosity material, the tray containing the higher
viscosity material is placed in the mouth.
 Since both the materials are mixed together, they join, bond & set together.
 After the materials have set, the tray & the impression are removed.
SIMULTANEOUS DUAL VISCOSITY TECHNIQUE
Replicating Materials—Impression and Casting. (2012). Craig’s Restorative Dental Materials, 277–325.

ADVANTAGES
• Over comes the polymerization shrinkage of the lightbody material
• Margins duplicated in light body
• Safest method is to make a new impression when bubbles or similar defects
are detected in critical areas.
DISADVANTAGES
• Use of custom tray
• An assistant required for mixing the material - tray/syringe simultaneously
• Margins duplicated in heavy body in case of excess pressure

SINGLE MIX OR SINGLE VISCOSITY OR
MONOPHASE TECHNIQUE
 Impressions often made with a medium viscosity impression material.
 Addition silicone & polyether are well suited for this technique because both have a
capacity for shear thinning.
 When the medium viscosity material is forced through an impression syringe, viscosity is
reduced, whereas the viscosity of the same material residing in the tray is unaffected. The
success of this technique depends on the pseudoplastic (shear thinning) properties of the
materials

ADVANTAGES
• Reduced wastage of the material
• Less time consumption
• Increased flow compared to heavy tray material.
DISADVANTAGES
• Relatively high viscosity and reduced flow of the monophase materials into
intracoronal features

PUTTY WASH TECHNIQUE
 SINGLE STAGE PUTTY WASH
TECHNIQUE
 TWO - STAGE PUTTY WASH
TECHNIQUE

 Two steps impression procedure whereby a preliminary impression is taken in high or
putty consistency material before the tooth preparation is made.
 Space is provided for a low consistency material by a variety of techniques, & after
tooth preparation, a low consistency material is syringed in to the area & the
preliminary impression reinserted.
 The low & high consistency materials bond, & after the low consistency material sets,
the impression is removed. This procedure is sometimes called a WASH TECHNIQUE
as very thin layer of low viscosity impression material which is used to record fine
details.
 The Putty consistency materials & this technique were developed for condensation
silicones to minimize the effects of dimensional change during polymerization. This
technique was extended to addition silicones after their introduction even though their
polymerization shrinkage is significantly lower.

SINGLE STAGE PUTTY WASH TECHNIQUE
 Twin phase or twin mix or single stage
 First the putty and over that the light body, is syringed onto prepared tooth surface and
the tray is seated in the mouth.
 Both materials sets at the same time inside the mouth (single stage).
Ricketts, D. (2011). Impression materials and techniqueas. Advanced Operative Dentistry, 163–176.
Putty in stock tray being seated over wash
before it starts to set.
Light bodied wash being syringed around
upper anterior tooth preparations

ADVANTAGES
• Reduced chair side time
DISADVANTAGES
• Putty displaces the light body due to its high viscosity resulting in failure to
record accurate details of the prepared teeth.
• Possibility of margins duplicated in putty medium
• Tendency of bubbles to be formed and occluded in the set impression

TWO - STAGE PUTTY WASH TECHNIQUE
 Double impression technique
 Condensation silicones and addition silicones are used
 A preliminary impression of the arch is made with stock tray
using heavy body/putty.
 This is allowed to set before the light body impression.
 The light body material is syringed into the primary impression tray and also
onto the prepared tooth surfaces and again seated in the same position to make
the final impression.
2;32(7):374-93.

When the impression is removed the putty recoils and the distorted
impression will result in a smaller die of a full coverage crown preparation

2;32(7):374-93.
Pre-operative putty impression is made intra
orally
 In the area where the tooth is to be prepared,
impression material is removed or channels
prepared using putty cutter instrument for
reseating
 Putty should be generously cut back in the depths of sulci ( palate upper arch)
and buccal and lingual sulci to provide escape channels for the wash
 The impression is then relined with lowviscosity material

 Space for the light body can be provided by removing some of
the putty from the preliminary impression or by keeping a thin
polythene sheet as a spacer in between the putty and the
prepared teeth while making preliminary impression
2;32(7):374-93.

ADVANTAGES
 Impression can be captured with the wash materials
 Superior margins and avoid drag formation
 Wash stage carried out after the putty has set and contracted
 Controlled wash bulk compensates for this contraction with minimal
dimensional change
DISADVANTAGES
 Extra chair side time
 Extra material
2;32(7):374-93.

TRIPLE TRAY TECHNIQUE
 Dual-arch impression or Closed bite (Wilson & Werrin 1983)
 Novel technique, where a single impression records the maxillary, mandibular, and
intercuspal positions.
 uses higher viscosity elastomeric impression material with low viscosity wash
material.
INDICATIONS -
 One or two units bounded by intact and opposed teeth
 Stable, reproducible and obvious intercuspal position
 Co-operative patient able to close directly into intercuspal position on request
 Tray does not contact axial tooth surfaces, or the adjacent tissues on closure
2;32(7):374-93.

ADVANTAGES
• Saves clinical time and material.
• Quicker because both arches are recorded at the same time,
• Laboratory investigations show that dies have comparable accuracy compared to those
obtained from full-arch impressions
• Less impression material is required as only one part of the arch is recorded.
DISADVANTAGES
• Special trays are used
• Tray distortion may occur if touches palate of patients
• Impressions are shallow, and makes them difficult to pour, and mounting can be
problematic without specific cast relators.

 When multiple post and core restorations are planned in the same arch, the laboratory-fabricated
custom-cast post may be the most time- and cost-efficient method.
 The teeth are prepared for the posts, and the final crown preparations are completed so that all
crown margins are on tooth structure.
 It is important that the crown preparation be completed before the impression for the post and core
is made so that the axial contours of the core can be fabricated correctly.
 An impression is made with an elastomeric impression material used with an injection technique,
which allows the impression material to flow into the total length of the prepared canal space.
 A 25-gauge needle is placed into the canal before the impression is made. The syringe material is
then injected into the canal until it begins to flow out the top of the orifice.
 While the syringe material is being injected, the needle is slowly removed from the canal.
 The needle serves as an escape channel for the trapped air and allows the elastomeric impression
material to reproduce the entire length of the canal space.
 Alternatively, the syringe material may be placed directly into the canal with a needle tube, which
is attached to the syringe.

 The tip of the needle tube must be long enough to extend to the entire length of the prepared
canal space. The elastomeric material is injected as the needle tube is slowly removed from
the canal.
 A final technique that can be used to ensure that impression material flows into the entire
length of the prepared canal is the use of a lentulo spiral The syringe impression material is
initially injected into the canal until it flows out of the orifice.
 The lentulo spiral is then introduced into the canal and rotated at low rpm to force the
impression material apically.
 The lentulo spiral should be slowly and gently advanced until the apical aspect of the
prepared canal is felt and then slowly removed while it continues to rotate.
 No reinforcement of the impression material in the canal space is required with the newer
impression materials.
 The impression is poured, and the custom posts are fabricated in the laboratory. At subsequent
appointment, the posts are cemented and the final impression for the restorations is made
without further tooth preparation.

(a) Use of 25-gauge needles to allow air to escape from canals during the
impression making to ensure a complete impression of the canal spaces.
(b) Final impression of canal spaces for laboratory fabrication of custom-cast
posts.

Matrix Impression System
The matrix impression system uses three impression materials:
1. A suitable elastomeric semi-rigid material required to form the matrix
2. A high viscosity elastomeric impression material, which will preferably bond to
matrix-forming material, and
3. A stock tray with a medium viscosity elastomeric impression material to pickup the
matrix impression and the remaining arch not covered by the matrix

Polysulfide
and
silicone
Immersion Glutaraldehydes,
chlorine compounds,
iodophors, phenolics
Disinfectants
requiring
more than 30-
min exposure
times are not
recommended
.
Polyether Immerse with
caution
Use disinfectant
only for a short
exposure time (<10
min)
Chlorine
compounds or
iodophors
ADA recommends
any of the
disinfectant
classes; however,
short-term
exposures are
essential to avoid
distortion.
Materials Method Recommended Comments
disinfectant
DISINFECTION

Rough or chalky stone cast
Bubbles
Irregularly shaped voids
Distortion
Rough or uneven impression surface
Common failures with elastomers

 Elastomers since their introduction have revolutionised the art of impression
making hence allowing the operator to provide acuurate fitting restorations
 Addition silicones and polyethers account for major portion of the current
practice.
 Condensation silicones, Polysulfides – more sensitive with respect to
handling considerations , mix-and-pour techniques, which may affect
accuracy.
SUMMARY

S 5 elastomeric imp. and tech

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