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1. IDEAL REQUIREMENTS TO OBTAIN AN ACCURATE IMPRESSION.
 Should be fluid enough to adapt to the oral tissues.
 Should be viscous enough to be contained in the tray that is seated in the mouth.
 While in the mouth, they should transform (set) into a rubbery or rigid solid in
less than 7 minutes.
 The set impression should not distort or tear when removed from the mouth.
 Impressions made should remain dimensionally stable until the cost can be
poured.
 Should maintain its dimensional stability after removal of a cost so that a second
or third cost can be made.
 Should be biocompatible
 The materials, associated processing equipment and processing time should be
cost effective.
Classification
I. Based on the degree of tissue compression
a. Mucostatic : Example : Impression plaster, ZOE impression paste.
b. Mucocompressive : Example : Elastomers.
- mucostatic impressions materials do not compress the tissue during
seating of impression tray -> ideal for edentulous jaw structures.
- Muco compressive – ideal for dentulous impressions.
II. By setting mechanisms
A. Chemical reaction
(irreversible)
By elasticity and use
Inelastic or rigid Elastic
Materials Use Material Use
1. Plaster of
paris
2. Zinc oxide-
eugenol
Edentulous
ridge
Interocclusal
records
Alginate
Non-equcous elastomres
- Polysulfide
- Polyether
- Condensation silicone
- Addition silicone
Teeth and soft
tissue
B. Thermally induced
physical reaction
(reversible)
Compound wax Preliminary
impression
Agar hydrocolloid Teeth and soft
tissu
III. Based on the chemical composition
1. Hydrocolloids
- Reversible -> agar – agar
- Irreversible -> alginate

2. 2. Non- squeous elastomeric impression materials
- Polysulfides
- Condensation silicone.
- Addition silicone
- Polyether
3. Impression compound
4. Impression plaster
5. Zinc / Oxide eugenol pastes
6. Impression waxes.
IV. Based on the viscosity of elastomers (ISO 4823)
Type
3 - Low viscosity (light bodies)
2 - Medium viscosity (medium bodied)
1 - High viscosity (heavy bodied)
0 - Very high viscosity (Putty)
V. Based on the physical properties categorized by ADA specification No.19 for
elastomers
- Compression set, flow, 24 hour dimensions change.
Type Maximum/ Maximum % Maximum %
Compression set flow Shrinkage
(24 hours)
I 2.5 0.5 0.5
II 2.5 0.5 1.0
III 5.5 2.0 0.5
The significance of this classification stems from the fact that impression
materials of the some chemistry may be different depending or critical physical
properties. Example polysulfide are type I or III depending on compression set. If large
deformation are anticipated on withdrawal over exaggerated undercuts, a type I material
experiences less distortion.
* HYDROCOLLOIDS
Hydrocolloid was patented in 1925, and it was introduced to the United States in the late
1920s. Credit for its first use in the United States for fabricating cast restorations is given
to J.D. Hart of Oklahoma, who began using it for the purpose in 1930.
Hydrocolloids was initially introduced to make impressions of hard tissues in place of in
elastic materials. After World War II, advances in polymer technology brought to the

3. dental profession a group of synthetic rubbery materials called ealstomers, capable of
making impressions of both soft and hard tissues.
Colloids are often classified as a fourth state of matter, “The colloidal State”.
True solutions exist as a single phase.
However, both colloid and the suspension have two phases.
• Dispersed.
• Dispersion phases.
Colloid as substances may be combinations of any States of matter, with exception of
gaseous states.
• Liquids or solids in air are called aerosols
• Gases, liquids or solids in a liquid are called forms, solids
evulsions and solid suspensions respectively.
All colloidal dispersions are termed sols.
The colloidal materials used for making impressions are either agar or align, dissolved in
water, hence the name hydrocolloids.
Sol-gel transformation – When the concentration of the dispersed phase in the
hydrocolloid is sufficient, the sol-gel.
In the gel state, the dispersed phase aggromerates, forming chains or fibrils called
micelles. The fibrils may branch and intermesh to form a brush-heap structure (Pic
McCake 134-Page )
For agar, secondary bonds (week) hold the fibrils together. These bonds break at slightly
elevated temperatures and become re-established as it walls to room temperatures. The
process is reversible.
For alginate, the fibrils are formed by chemical action because the transformation is not
reversible.
Gel strength For the reversible gel, the lower the temperature, the stronger the gel, and
vice versa. When gel is heated, resulting in greater inter fibriller distances and
reduction of their cohesions. On the other hand, strength of irreversible gel, not
affected by normal temperature changes. The strength of gels can be increased
by addition of certain modifiers such as fillers and chemicals.
Dimensions effects
• The gel may lose water by evaporation from its surface or by exudation of fluid
on its surface by a process known as synthesis.
• Whenever water or fluid is removed from the micelles of the gel by synthesis, the
gel shrinks.
• If gel is placed in water, it will absorb water by a process known as inhibition.
• The effects of synthesis, evaporation and inhibition must be limited to ensure the
proper dimensions of impressions -> pouring cost immediately can reduce
distortion.
AGAR (REVERSIBLE HYDROCOLLOIDS)

4. - Was introduced to dental progression in 1925 mainly used in the area of
removable partial denture prosthesis.
- Until early 1950’s, it was the principal and only elastic impression
material used in crown and bridge and partial denture prosthesis.
Compression
Component Function Composition
Agar Brush – heep structure 13 – 17%
Borates Strength 0.2 – 0.5%
Sulfates Gypsum hardener 1.0 – 2.0%
Wax hard Filler 0.5 – 1.0%
Thixotrosic materials Thickness 0.3 – 0.5%
Water Reaction Balance
Alkyl Benzuate Prevent growth of mold
in impression material during 0.1%
storage.
Color and Flavors Taste appearance Trace
Cylation process
- Setting of reversible hydrocolloid, called gelation
- Physical change from sol – gel induced by temperature changes
- Gel converts to sol when heated to 70 – 100oC -> liquefaction
temperature.
- When cooled sol transforms to get at 37o – 50oC -> gelation temperature.
- Temperature leg between gelation temperature and liquefaction
temperature of the gel makes it possible to use agar as dental impression
material.
• Sol - Gel
• Gel -> sol at 70 – 100o
C (Liquefaction temperature)
• Sol -> gel at 37 –50o
C (Gelation temperature)
Manipulation
Includes liquefying the gel, placing it in impression tray, tempering it to a lower
temperature, and maintaining it in its fluid state to capture the details of the oral
structures. Once in the mouth, the material is cooled below mouth temperature to ensure
gelation.
Conditioning unit for the agar hydrocolloid impression materials consists of water baths
for:
• Liquefying the material : Placed in boiling water for 10 min (at high attitudes
water (Colorado) boils at below 100oC, propylene glycol can be added to obtain a
temperature of 100oC Agar hydrocolloid frequently supplied in two forms –
syringe and tray materials (gel) because first step is to convert gel -> sol by
liquefying.

5. • Storage after boiling : Stored in sol condition at 65oC until need for injection into
cavity preparation or for filling a tray.
• tempering the tray hydrocolloid. : Since 55oc is the maximum tolerable
temperatures with storage temperature of 65oC could be too hot.
• For the oral tissues -> therefore tempered at 45oC. For 3-10 minutes. Tube of
hydrocolloid sol removed from storage, tray is filled, gauze ped placed over the
tip of tray (prevent inhibition) and placed in tempering basin.
Syringe materials is not tempered, temperature is lowered as the material extrudes out of
the syringe. (Pic of conditioning Page 31)
Making the Agar impression
First syringe material directly taken from storage compartment applied to the base
of the preparation, then remainder of the prepared tooth is covered. Tray hydrocolloid is
removed. From the tempering basin, outer layer removed and impression made. Gelation
is accelerated by circulating cool water (approx. 18-21oC) through the tray for 3-5 min.
Sol is a poor ocnductor of heat because rapid cooling may cause concentration of stress
near the tray. Hydrocolloid exhibit viscoelastic behavior therefore, it is necessary to
remove impression with a snap rather then tease it out. Time required to re-liquify is 2-4
min longer than previous time -> because more firmer -> can the re used 4 times (Pic tray
– water cooled Page 32 Rahul Tyagi)
Properties ANSI / ADA Spec. No. 11
1. Permanent deformation : ANSI / ADA specification requires recovery from
deformation to be greater than 96.5% after material is compressed 20% for 1
seconds tray type -> 99%.
2. Flexibility - ANSI / ADA specification requires 14-15% Agar impression
material meets this requirements.
3. Strength - Compressive strength – 8000 g/em2.
Tear strength – 800 – 900 g/cm
ANSI / ADA specification requires 765 g /cm of fear strength.
ALGINATE (IRREVERSIBLE HYDROCOLLOID)
Was developed as a substitute for the agar impression material when its supply
become scarce during World War II, as they were imported from Japan.
A chemist from Scollend perceived that certain brown seaweed (Elgae) succumbs
on atypical mucous extraction.
The substance is called anhydro-B-d-mannuronic acid or alginic acid (insoluble in
water)
COMPOSITION
Component Function Weight percentage
Potassium alginate Soluble alginate 15
Calcium alginate Reacter 16
Potassium titanium
Fluoride Accelerator 3

6. Zinc oxide Filler particles 4
Diatomaccous earth Filler particles 60
Sodium phosphate Retarder 2
When powder in the alginate can is fluffed to break loose the particles, fine silica
particles will become airborne from the can when lid is removed. Inhalation of these
silica particles is a possible health hazard. (silicosis and pulmonary hypersensitivity)
Because Dustless alginate Introduced -> incorporated glycerine on the alginate powder to
agglomerate the particles.
Cylation process
Soluble alginate reacts with calcium sulfate to form an insoluble calcium alginate
gel. The production of calcium alginate is so rapid that it does not allow sufficient
working time because a third water soluble salt, trisodium phosphate is added to prolong
working time -> calcium sulfate will react with this salt in preference to soluble alginate
until trisodium phosphate is exhausted.
Classification of alginate (Robert C. Craig)
I. According to concentration of sodium phosphate
• Fast set – 1.25 – 2min. )
• Regular set – 3 – 4.5 min ) working time
II. According to concentration of filler
• Soft set
• Hard set
Controlling setting time
• By the amount of retarder added (Manufacturer)
• By altering the temperature of water -> Higher the temperature,
shorter is the setting time.
• Rate of setting reaction doubled by temperature increase of 10oC
because water cooler than 18oC or warmer than 24oC not
advisable.
Manipulation
The measured powder is sifted into pre-measured water that has already been poured into
a clean rubber bowl.
A vigorous figure – 8 motion is best, with the mix being stropped against the sides of
rubber mixing bowl with intermittent rotation of the spature to press out air bubbler
Mixing time between 45 sex – 1 min -> resulting in a smooth cream mixture that does not
readily drip off the spatule when raised from the bowl.
Perforated tray normally used, in case of plastic or metal vin – lock tray, a thin layer of
alginate tray adhesive is used.

7. Alginate is very week, therefore sufficient bulk of material between tray and tissue of 3
mm is required.
Tear strength of increased when the impression is removed with a snap.
Properties
Permanent deformation : ANSI / ADA specification requires recovery from
deformation to be more than 95% when material is compressed 20% for 5 seconds.
Flexibility : ANSI / ADA specification permits a range of 5 – 10% at a stress of 1000
g /cm2 and most alginate have 14%
Strength : ANSI / ADA specification requires compressive strength -> at least 3570
g/cm2.
Alginates -> compressive strength = 5000 – 9000 g.cm2
Tear strength = 380 – 700 g / cm
Compatibility with zypsum : Free water accumulation, dilute the model material
yielding a soft chalky surface.
Dimensional stability : Alginate impression lose or inbibe water by evaporation,
syneresis or inhibition because it should be poured immediately.
Disinfection : 1% Na. Hypochlorite.
2% glutaraldehyde - 10 – 30 min.
showed 0.1% dimensional change -> insignificant when used for study models and
working cost.
Laminate technique (Alginate – Agar Method)
- The tray hydrocolloid is replaced with a mix of chilled alginate that bonds
to the syringe agar.
- The alginate gels by a chemical reaction, whereas the agent gels by means
of contact with the cool hydrocolloid.
- Maximum detail is produced.
Short comings
1. Bond between agar and alginate is not always strong.
2. Higher viscosity alginate displaces the agar during seating.
3. Dimensional accuracy of alginate limits the use to single
units.
Modified alginates
- Alginate in the form of sol, containing the water but no source of calcium
ions a reactor of plaster of paris can then be added to the sol.
- Two component system -> paste form -> one containing alginate sol and
second calcium reactor.
- Alginates modified by the incorporation of silicone polymers -> supplied
as two pastes show better fine – detail reproduction and tear resistance but
poor dimensions stability (Alginates) hybrids of alginates and silicone
elastomers but properties closely related to alginates.

8. Disinfection
- Current protocol for disinfecting hydrocolloid impression recommended
by center for disease control is the use household bleach (1:10 dilution)
iodophors or synthetic phenols as disinfectants
- Can be sprayed on exposed surface and then wrapped in disinfectant
soaked paper – towel and placed in sealed plastic bag for 10 min.
- Alternative method is immersion, but should not exceed 10 min.
Shelf life
- two major factors
1. Storage temperature
2. Moisture contamination from ambient air.
- Sealed pouches and can available
- Best if used before 1 year.
- Store in cool, dry environment.
Effects of Mishandling (Table 9-11) Annusavice Page 249)
NONAQUCOUS ELASTOMERIC IMPRESSION MATERIALS
- ANSI / ADA specification No.19.
- An elastomeric material consists of large molecules with week interaction
among them. They are tied together at certain points to form a three
dimensional net work.
- The chains of these materials uncoil on stretching and upon removal of the
stress they bounce back or snop back to their relaxed entangled state.
- Setting occurs through a combination of chain lengthening
polymerization and chemical cross linking by either a condensation
reaction or addition reaction.
I. Chemically four kinds of elastomers
a. Polysulfide
b. Condensation polymerizing silicone
c. Addition polymerizing silicone
d. Polyether
II. The current ANSI/ADA specification No. 19 recognizes three types based on selected
and the dimensional change of the set materials rather than on chemistry.
- type I
- Type II
- Type III
III. Each type is further divided into four viscosity classes.
0 = very high consistency (putty like)
1 = High Consistency (Heavy bodied)
2 = Medium consistency (medium bodied)
3 = Low consistency (light bodied)

9. Polysulfides (Synonyms : Rubber base, morception, Thiokol rubber)
Component Function
Base Paste 1. Polysulfide This is further polymerized and
Prepolymer with cross linked to form rubber
Terminal and
Pendent thiol
(-SH) groups.
2. Dibutyl pthelate Platicizer to control viscosity
3. Inert filler To provide the required
(lithopone or Strength
titanium dioxide)
4. Sulfur (0.5%) To accelerate the reaction
(Reactor paste)
Note : (Introduced in the early to middle 1950s).
Catalyst paste Lead dioxide (Brown) on To react with thiol groups
alternative oxidizing causing setting
agents hydrated copper
Oxide (Greens)
Oleic or stearic acid Reterder to control the rate
of setting reactions
Some amount of
Plasticizer and fillers
Setting reaction
The terminal and pendant perception group of each molecule is oxidized by the
addition of oxidizing agent present in the reaction paste, which in turn causes both
lengthening of polymer chain by oxidation of terminal merception groups and cross
linking by oxidation of pendant metception groups.
Reaction is of condensation type since water is produced as a by produced –
dimensional changes.
Polymerization is exothermic and is affected by moisture and temperature ->
decreases working time.
Unpleasant subjects odor and long setting time in the mouth.
Lead dioxide -> sticky and stains clothing permanently alternatives -> copper
hydroxide organic hydroperoxides (Evaporate after cure).
Available in three consistencies

10. - Low
- Medium
- High
Packaged as two pastes base (whitie) catalyst (Brown)
Advantages Disadvantages
- Extensive shelf life - Odor lipid patient
- Less hydrophobic - Must be poured in stone instantaneously
- Established precision - Unitidy and stains clothing
- High tear strength cheep to use - Potential for distortion
- Customary tray mandatory
- Subsequent pours are less accurate.
CONDENSATION SILICONE (SYNONYMS, SILICONE, POLYSILOXANE)
ORGANAIZATION OF SILICONE)
Composition
Components Function
Base paste Hydroxyl – terminated undergoes cross linking
Polydimethyl to form rubber
Siloxne
Propolymer
Colloidal
Silica Filler
Catalyst
Poly Vinyl Silicone
Prepolymer
Colloidal silica filler
Chloroplatinic Cat-alyer
Acid
Setting reaction
The polymerization reaction if of addition type, the cross linking is taking place
between the vinyl terminal group of accelerator paste and the siloxone group of base
paste and chloroplatinic acid activates the reaction.
No by product formed If proper balance between base and reactor is not maintained,
hydrogen gas is produced .Hence platinum or palladium gas is produced
manufacturer to act as a scavenger for the released hydrogen gas.
As inherently hydrophobic -> nonionic surfactant added that migrates towards the
surface of the impression material and has its hydrophilic segment oriented towards the
surface -> allows impression material to readily wet soft tissue and enhance the ability of
gypsum to optimum maximum detail. Sulfur contamination from natural latex groves
inhibits the setting of addition silicones.

11. Available in 4 consistencies – Light body
Medium body
Heavy body
Putting
Advantages Disadvantages
- Excellent dimensional - Hydrophobic
accuracy
- Long term dimensional - Expensive
Stability - Hydrogen gas evaluation in some
Materials
- Pleasant to use - Poor wetting
- Short setting time - Hydrophilic formulations
- Auto mix available inhibe moisture.
- If hydrophilic, good compatibility
with gypsum - Sulfur contamination by latex glove
Note : Incorporated surfactant makes electroplating more difficult and also makes
impression material more sensitive to the retardant action of sulfur.
Newer Formulations
1. Hydrophilic – addition of surfactant
2. Hydrogen absorbs – Palladium
3. Monophase – Sheer thinning
4. Made shiffer – Bite registration
POLYETHER (Synonymic epimine)
First developed in Germany in Mid 1960’s primarily to function as on impression.
Composition
Base Paste -> Immune terminated Becomes cross lined
Prepolymer to form rubber
Inert filler – Silica Filler – to control viscosity
Plasticizer -> To aid mixing
Pthelate
Catalyst paste
Alkyl – cromotic Initiates cross linking
Sulfonate
Silica Filler
Base Catalyst -> 8:1
Pthalets Plastilizer

12. Setting reaction
The polyethers curve through cross linking of a difunctional epimine terminated
prepolymer catalyzed by on alkyl benzenes sulfonate catalyst. The reaction involves ring
opening without formation of volatile by products.
- Modified to greatly reduce the stiffness -> identified by additon of F
following brand name.
- Stable if stored dry, otherwise absorbs moisture and undergo significant
dimensional change.
- Available in 3 consistence -> light body
Medium body
Heavy body.
Advantages Disadvantages
Dimensions stability - Set material very stiff
Accuracy - Inhibition
Shorter setting time - Short working time.
Automix available - Allergic hyper sensitivity in some
Cases.
POLYETHER URETHANE DIMETHACRYLATE
This material appeared on the market briefly in late 1980’s, discontinued because
of problems with surface polymerization.
Composed of - Polyether urethane dimethacrylate resin.
- Diketone initiator
- Amine accelerator
- 40 – 60% silica filler
- Used in a clear tray, photo initiated by 400 – 500 mm blur light.
- Most useful traits – unlimited working time coupled with short setting
times.
MANIPULATION
Paste form -> equal lengths of base and reactor paste taken over the mixing pad, a stiff
stainless steel spatula is used for mixing, reactor paste is first spread over the base paste,
mixing continued until a smooth, homogenous, streak free mix is obtained.
When reactor supplied in liquid form -> number of drops per unit length are
recommended by manufacturer.
Two putty system -> kneaded between the finger, in case of liquid reactor initial
mixing with spatula is accomplished.
* Automatic dispensing and Mixing devices.
- Used for light and medicine viscosity meteride of addition silicone,
condensation silicone and polyethers, not polysulfides (Sticky).

13. - Material is supplied is prepackaged cartridges with a disposable mixing
tip.
- The cartridge inserted in a gun like device, and base and catalysis are
extruded into the spiral mixing tip, where mixing occurs as they progress
to the end of the tube.
Advantages
1. Greater uniformity in proportioning and in mixing.
2. Less air incorporated into the mix.
3. Mixing time reduced.
4. Less chance of mix getting contaminated
5. Less wastage of material.
Dynamic mechanical mixer
The device uses a motor to drive parallel plungers that force the materials into a
mixing tip, and the spiral inside the mixing tip rotates as the material are extruded
through the tip -> higher viscosity material can be mixed. Example pentamix, ESPE
America.
Properties
Viscoelastic Properties
Viscoelesticity describes the dependence of an impression materials response to the
speed of removal.
Visco elastic behavior is intermediate between that of an elastic solid and a viscous
liquid.
Elastic solid -> Spring, which deforms instantly to a certain extent when one applies a
specific load -> deformation reversed completely or removal of the load.
Viscous liquid -> oil dashpot, which does not respond instantly but deforms as the load is
applied over time -> deformation is permanent.
Maxwell – Voigt model – Fig 9-3, Page 21, American
A -> Stress Free state
B -> As force is applied, S1 responds instantaneously with definite amount of
deformation, D1, D2 and S2 no deformation, D2 prevents S2 deformation because of dash
pot inertia.
C -> As force applied over time, both deshpots are activated and continue to deform as
10 mg as force applied, S2 deforms a long with D2
D -> As force is released, S1 recovers instantly others remain unchanged.
E -> As time posses, S2 over comes inertia of D2 and recovers along with D2 D1 remains
unchanged.
Clinical importance
The amount of permanent deformation is attributed to either deshpot is dictated by
the duration of tension or compression exerted on the materials therefore a teasing or
rocking method should not be used to remove the impression -> snap removal.

14. WORKING AND SETTING TIMES
Working time measured at room temperature setting time measured at mouth
temperature.
The end of working time might be defined as the time when a blunt needle of a certain
diameter and weight fails to penetrate a volume of impression material to a specified
depth.
Setting time is defined as the transitional time at which plastic properties which permit
molding and impression taking at lost and elastic properties permitting removal of the
impression material are acquired or when a blunt instrument fails to permanently indent
the set impression materials.
Effects of temperature.
Increase -> decreases both working and setting time by accelerating the curing rate.
Decrease -> Increase working time, can be accomplished by refrigerating the materials or
mixing on a chilled dry glass slab.
Effect of viscosity
Increase -> decrease working time and setting time.
Altering base / catalyst ratio can alter the working and setting time -> but adversely
affects the mechanical properties.
Impression materials
Mean working time (min) Mean setting time (min)
23o
C 37o
C 23o
C 37o
C
Polysulfide 6.0 4.3 16.0 12.5
Condensation silicone 3.3 2.5 11.0 8.9
Addition silicone 3.1 1.8 8.9 5.9
Polyetter 3.3 2.3 9.0 8.3
Clinical importance
• Duel arch technique for single crown preparation
Quick set material – short working time.
• Fill arch impression with multiple prepared teeth.
Longer working time.
Dimensional stability
- Five major sources of dimensional changes.
1. Polymerization shrinkage.
2. Loss of by product (water or alchohol) during condensation reaction.
3. Thermal contraction from oral temperature to room temperature.
4. Inhibition when exposed to water, disinfectant or high humidity environment
over a period of time.
5. Incomplete recovery of deformation because of viscoelastic behavior.
- Addition silicone -> most stable -> costs produced between 24 hours and 1
week as accurate as a cast made in first hour.

15. - Polyether -> can absorb water from the atmosphere -> poured within 1
hour for maximum accuracy.
- Condensation silicone and polysulfides -> loss of by product -> poured
within 30 minutes.
ACCURACY
- ANSI/ADA specification No.19 -> impression materials must be able to
reproduce fine detail of 25 μm or less.
- Lower the viscosity better it records fine detail, putty can record only upto
75 μm.
- Corresponding specification for gypsum die materials is 50μm
- Most accurate -> addition silicone reversible hydrocolloid.
Elastic Recovery
Impression materials needs to be able to flow readily into undercut areas in the mouth, set
in that position, and to be able to “rebound” back to its original shape, when the set
impression is removed from the mouth -> elastic recovery.
PVS impression material – 99% elastic recovery condensation silicone.
Polyetter
Polysulfide
Elastic recovery can be maximized by blocking the undercuts.
RHEOLOGIC PROPERTIES (FLOW AND FLEXIBILITY)
Viscosity of material is most important factor in controlling the flow.
Light body materials flow readily into minute details, while the tray or heavy body
material provide more rigidity to the impression and help force the lower viscosity
material into the gingival sulcus.
Early versions of light body tended to flow off the prepared tooth with time, now the
newer pus and polyettersare thioxtrophic and stay where they are syringed but flow
readily when the heavier body tray materials are placed over them.
Monophesic material -> shear thinning effect when “false body” permits the material to
stay in the tray without segging or dripping, and yet the same material can be used in a
syringe.
A material that exhibits this property of becoming more fluid when shear rate is increased
(Shaking, spatulating or injecting through a syringe) is described thioxtrophic.
Stiffness -> polyetter (Decreasing order) addition silicone, condensation silicone,
polysulfide.
Polyetler -> most rigid -> 1. Problem when dealing with long, thin preparations of
periodontally involved teeth 2. Also can result in fracture of dies.
Advantageous -> duel etch impressions -> where double bite trays are flexible ->
thixotrophic materials best used.
Tear strength
Important property when dealing with impression materials used in interproximal and sub
gingival areas. Ranking from lowest to highest

16. Hydrocolloids > Silicones > polyether > polysulfide.
Cager and Alginate (Addition and Condensation)
Influenced by (1) consistency -> increased viscosity increases tear strength.
(2) Manner of removal -> rapid rate of force during removal increases tear strength.
HYDROPHILICITY
- Hydrocolloids -> hydrophilic
- Polyetter -> hydrophilic but require dry preparation for making
impression.
- PVS and condensation silicones -> hydrophobic
- Newer materials -> classified as hydrophilic
 Including non-ionic surfactants.
 Grafting the surfactant to silicone polymer.
- Improves wet ability and reduces contact angle -> 95 to 53o.
- Hydrophilic materials -> 35o contact angle.
- Technically classified as hydrophilic -> PVS material easier to pour die
materials, but do not make it possible to make acceptable impression in a
wet environment.
Biocompatibility
- Cell cyto toxicity -> polysulfide results in lowest cell death event and set
polyetter highest.
- Elastomer – induced biocompatibility problem occurs when a segment is
lodged in patients gingival sulcus -> gingival inflammation.
- Radiopacity of polysulfides advantageous here.
- Contact dermatitis from polyether catalyst to dental assistant has been
reported, but no cyto toxic effects has been reported.
Shelf life.
- Showed in a dry, cool environment.
- Tubes should be kept tightly closed, reseal the alginate container after
dispensing the powder.
- Arbitrarily suggested that no more than 6 months supply should be kept on
hand at any time.
Economic factors
- Reversible hydrocolloid less expensive than elastomers, but equipments
associated with it compensated for the cost.
- Polyether and PVS most expensive.
- Reduce cost by using auto-mix devices, dual and technique when
indicated.
Effects of mishandling elastomers (Tab 9.5 Page 230 Anusavice Tab 9.6)
DUPLICATING MATERIALS (ANSI/ADA Specification No. 20)
Both types of hydrocolloid are used in the dental laboratory to duplicate dental casts or
models used in the construction of prosthetic appliances and orthodontic products.

17. Reversible (Agar) Hydrocolloid most commonly used because it can be used many times.
Has same composition as impression material, water content is higher.
Classified into two types according to ANSI/ADM specification No.20. –
Thermoreversible – Type I Non reversible – Type II
Silicones and polythers can be used but costly.
INELASTIC IMPRESSION MATERIALS
- Impression plaster
- Impression compound.
- Zinc oxide eugenol paste.
Impression plaster
- Composition similar to dental plaster, consists of β-calcium sulphate
hemihydrate which when mixed with water reacts to form calcium
sulphate dehydrate.
- Mucostatic -> for edentulous flabby ridge.
- Differences from dental plaster.
• Rapid setting.
• Smaller setting expansion.
• Lower strength.
- Rarely used because of their inability to sustain elastic deformation
without fracture.
Impression compound (ANSI/ADA specification No.3) composition.
Waxes, thermoplastic resins, filler and coloring agent, shellac, stearic acid and
gutta percha are added to improve plasticity and workability.
Classified into : Type I – low fusing
Type II – high fusing
Low fusing -> impression materials -> sheet or stick form -> used for making
impressions of edentulous ridges using stock trays. Sticks are used for border moulding
or for recording impressions of single crowns using the upper ring technique.
Compound may be softened over a flame or by immersion in warm water bath.
Dimensional stability
Allow thorough cooling before removal and pour within 1 hr
ZINC OXIDE EUGENOL IMPRESSION PASTES
(ANSI / ADA SPECIFICATION No.16)
Composition
Base Percentage Function
Zinc Oxide 87 Reactive ingredient
Fixed vegetable or mineral oil 13 Plasticizer, off sets action of
eugenol as an irritant.
Paste
Oil of cloves or eugenol 12 Oil of cloves contain 70% - 85%,
eugenol less irritating

18. Gum or polymerized rosin 50 To accelerate setting
Filler 20
Lanolin 3
Resinous balsam 10 To increase flow and improve
mixing properties.
Acceler solution (CaCl2) and color 5
Classified as
Type I – hard paste -> 10 min setting time
Type II – soft paste -> 15 min.
Setting time
Shortened -> adding small amount of acceleration
Drop of water
Prolonged -> cool mixing slab
-> plasticizer – inert oil or wax.
Thick consistency -> compress the tissue
Thin consistency -> little or no compression.
Dimensional stability
Less than 0.1% shrinkage can be preserved indignity
Non-eugenol pastes
- Orthoethoxybenzoic acid (EBA) -> valuable substitute for eugenol.
- Bactericidal agens and other medicaments can be incorporated without
interfering with the reaction.
Surgical pastes
- After gingivectomy, ZOE paste may be placed over the wound to aid in
the retention of a medicament and to promote healing.
- Softer and slower in their setting reaction.
Bite registration pastes.
- Occlusal relationships recorded include impression plaster, compound
wax, resin and rectal oxide paste.
- ZOE paste as recording material in construction of complete dentures and
fixed or RPD.
- ZOE interocclusal record more stable than one made in wax.
TRAYS
All impression materials shrink upon setting.
Reversible hydrocolloid -> shrinkage occurs as a thermoplastic event.
Elastomeric impression -> polymerization shrinkage materials.
To obtain accurate impression a relatively uniform amount of bulk in the impression is
imperative, so that there is uniform shrinkage throughout the body of the impression.
Water based impression materials, such as reversible or irreversible hydrocolloid provide
maximum accuracy with a cross sectional thickness of 4-6 mm-> best achieved with
stock trays.

19. Elastomeric impressions, most accurate when used with a cross sectional thickness of 2
mm -> best achieved with custom tray.
STOCK TRAYS
- Stock plastic trays
- Stock metal trays : perforated
 Non-perforated
 Rim lock trays
 Denticular
- Clear trays Edentulous
Stock plastic trays (Pic. BDJ. Article)
- Can be used for impression of one or two single units.
- Trays do not have sufficient rigidity
- Low cost
- Contra indicated with fixed bridge work because its flexibility adversely
affects inter preparation, cross arch and anteroposterior dimensions
Stock metal trays (Pictures)
- Coated steel or stainless steel trays combine the convenience of stock
plastic trays with the rigidity of custom trays.
- Perforated or rim lock trays indicated for putty wash impressions for
mechanical retention in addition to tray adhesive (adhesion of putty to its
impression adhesives is not as reliable as with other viscosities).
Custom trays
- Custom tray improves the accuracy of an elastomeric impression by
limiting the volume of the material, thus reducing two sources of error:
• Stresses during removal.
• Thermal contraction
- Custom trays, constructed on the diagnostic cast using one layer of bae
plate wax as a spaces
- Trays can be fabricated because (Picture page 364 – 68) Roseinsteil
- Pollymethylmethecrylate
- Photo-cure bisacryl materials (Triad)
- PVS putty materials
- Thermoplastic trays
- PMM trays should be fabricated at least 24 hours in advance to in sure stability.
- Tray should extend 3-5 cm for gingival margin, wax spaces covered with tin foil.
- Thermoplastic trays with elastomers not recommended as the plasticizers in elastomers
attack and soften the compound.
- Occlusal stops – critical for proper orientation of tray in the mouth.
- Three stops ideal, with atleast one posterior to prepared teeth.
- Should be placed on non-functioning cusps so that distortion will not interfere with
inter cuspal relationship.

20. - 45 degree slope helps to center the tray.
STOCK TRAY VERSUS CUSTOM TRAY
- The difference in cross sectional thickness of material in a stock tray is
only about 1.5 – 2mm thicker than that in a custom tray.
- Numerous articles have compared accuracy of impression made with a
custom tray with the accuracy of impressions made with stock tray.
- Gorden et al, has reported that the inter preparation distance in cast made
from polysulfide, poly vinyl siloxane and polyether impression was 45-
100 um, greater when stock trays were used instead of custom acrylic
resin or thermoplastic trays.
- However, Bomberg et al found no significant difference in the marginal fit
of single – tooth restorations on case made from poly vinyl siloxane
impressions in stock and custom trays.
DUAL ARCH TRAYS
Trays are available in both anterior and posterior designs and consist of an outer rim that
is spanned by a mesh fabric. Both plastic and metal design are produced.
Any elastic impression material can be used, but more rigid- bodied materials are
preferred, also developed to be used with reversible hydrocolloid impression materials.
Duel arch tray may be used to make impressions for single unit crowns where as well
established inter cuspal position is present and lateral contacts are not a factor (anterior
guided occlusion).
If bucco-lingual width of the elevator ridge is wider then the width of the tray, the plastic
outer rims will be wedged apart when the patient closed into the impression material –
resulting is distorted impression -> tray can be modified by cutting the mesh and
spreading the tray.
Tray adhesive
Adhesion of impression material to the tray is achieved through the use of specific
chemical tray adhesives.
Tray adhesives are usually liquid rubber (eg. Butyl rubber) dissolved in a volatile solvent
such as chloroform or ketone -> note that these adhesives should not be inter changed.
Roughening the surface of custom trays increases the adhesion.
PVS putty does not adhere well to its adhesive therefore mechanism retention in the tray
(perforation / rim lock) mandatory.
Pointed in a thin layer on the internal of the tray and the tray borders atleast 7-15 minutes
before making the impression.
Gingival displacement
Indirect restorations – including cast gold inlays, onlays, partial veneer restorations and
complete crowns – metal ceramic and all ceramic, and bonded ceramic inlays and onlays
are routinely used to restore defective teeth.
These restorations frequently have cervical margins that are intentionally placed in the
gingival sulcus for esthetic or functional reasons.

21. The procedure used to facilitate effective impression making with intra crevicular
margins procedure is the irreversibly displace the gingival tissue in a lateral direction, so
that a bulk of low-viscosity impression material can be introduced into the widened
sulcus and capture the marginal detail.
A critical sulcular width of 0.2 mm is required for maximum accuracy of the impression,
and to improve the tear strength of the material so that it can be removed from the mouth
intact with no tearing.
According to Bensen Bomberg (1986) gingival tissue can be displaced laterally or
vertically lateral retrection. It displaced the tissues so that an adequate bulk of
impression material can be interfaced with the prepared tooth (gingival displacement)
Vertical retraction : Exposes the uncut portion of the tooth apical to the finish bone.
One of the prime requisites to successful tissue management is the begin the restorative
procedure only after the gingival tissues are deemed healthy
This is not always possible in the clinical setting, but nonetheless it should be a constant
goal.
Classification of techniques
- Mechanical
- Chemical
- Surgical
- Combination of the three
Biologic width – defined as the dimension of the soft tissue, which is attached to the
portion of the tooth coronal to crest of the alveolar bone (Gargiulo et al 1961).
Biologic width = Junctional + Connective tissue
2.04 mm 0.97 mm 1.07 mm
Tissue displacement must be done gently but with sufficient firmness to place the cord
just apical to the margin.
Over packing -> cause tearing of gingival attachment, leading to irreversible gingival
recession.
Violation of biologic width
Biologic width forms a “Biologic seal” around the neck of the tooth.
Prevents micro organisms an their by products from migrating to the
underlying tissue.
Violation of biologic width
Leads to migration of micro organisms and toxins.
Inflammatory reaction
Loss of attachment

22. Apical migration of marginal attachment
Periodontal pocket -> bone loss
- Location of prepared cervical margin is 0.5 mm from the healthy free
gingival margin or 2-3mm from the crest of the alveolar bone and must
follow the natural scalloped form of the attachment and alveolar housing.
Techniques for gingival displacement.
Majority clinicians use a combination of mechanical – chemical displacement, using
retraction cords along with specific hemostatic made cements.
3 main variations of mechanical chemical method
a. Single cord technique
b. Double cord technique
c. Infusion method of gingival displacement.
Retraction cords are supplied in three basic designs, twisted cord, knitted cord and
braided cord.
The key to effective displacement is to use a cord of sufficient diameter to provide
adequate displacement is largest cord that can be automatically placed in the sulcus.
Hemostatic medicaments ;
Aluminium potassium sulfate
Aluminium sulfate
Aluminium chloride
Epinephrine
- Use of epinephrine as a gingival displacement medicament has the potential to cause
systemic side effects if used in appropriately not used for routine gingival displacement
cord packing instruments -> roseinsteil figure 14.3 page 358.
Single cord technique (Picture)
Indicated when making impressions of one or three prepared teeth with healthy gingival
tissues
The largest diameter braided or knitted cord that fits in the sulcus is selected.
Socked in the medicament of choice
Excess is blotted from the socket cord with sterile cotton sponge.
The cord is packed into the sulcus in a counter clockwise direction -> starting from the
inter proximal area.
The instrument should be angled toward the tooth so the cord is pushed directly into the
area.
Should also be angulated towards the cord already packed, to avoid it being displaced.
The cord needs 8-10 minutes to effect adequate lateral displacement.
The cords should then be soaked in water to allow it to be easily removed from the
sulcus.

23. Double cord technique (Picture)
- This technique is used
• When making impressions of multiple prepared teeth.
• When tissue heath is compromised and it is impossible to delay the procedure.
- With the double cord technique
- A small diameter cord with no medicament is first placed in the depth of the sulcus.
- A larger – diameter cord with the medicament is placed above the small diameter cord.
- After waiting for 8-10 minutes, the larger diameter cord is socked in water and
removed.
- The small – diameter cord is left in the sulcus during impression making.
The infusion technique
• Haemorrhage is controlled using a specifically designed dentoinfusor with a ferric
sulfate medicament (15% or 20%) ->20% preferred because it is less acidic and
does not remove smear layer of dentin from prepared tooth.
• Infusion is used with a burnishing motion in the sulcus and is carried
circumferentially 360o around the sulcus.
• When hemostasis is verified, a knitted retention cord is soaked in the febric
sulfate solution and packed into the sulcus -> left in place for 1-3 min and then
removed.
• Effective ancillary technique for control of haemorrhage when using single cord
technique.
Every other tooth technique
Placing retraction cord simultaneously around all prepared teeth (especially
anterior) may result in strangulation of gingival papillae and eventual loss of papillae ->
resulting in unesthetic black triangles in the gingival embressures.
Single or double cord technique canbe used, retraction cord placed around the
alternate prepared tooth -> impression mode -> then gingival accomplished on remaining
teeth and record impression made -> finally a pick up impression allows fabrication of a
master cast with diet for all the prepared teeth.
NEWER MATERIALS
Merocel : Synthetic material that is chemically extracted from a bio-compatible polymer
(hdyroxylate polyvinyl acetate) that creates a net like strip. -> capable of straumatic
gingival retraction.
Used in strips of 2mm thick that expand with absorption of selected oral fluids ->
gingival retraction.

24. Expa- 3 year is a paste used for gingival retraction that opens the sulcus. It is supplied
in a syringe, that is designed to be injected into the unretracted sulcus which then
becomes rigid and creates space between the tooth and the tissue.
Takes about 2 min 30 seconds to achieve sulcular exposure.
It contains haemostatic astringent -> kaolin, aluminium chloride.
Size, exerts moderate and calculated pressure on gingival margin, 0.1 N/mm2,
attachment safe guarded.
Retroc : Gingival retraction putty is a condensation silicone formula with potassium
aluminium sulfate.
Surgical methods
- Rotary curettage
- Electro surgery
Rotary curettage (Pic. 16-23, Page 268, Shillingburg)
Is a “Troughing” technique, the purpose of which is to produce limited removal of
epithelial tissue in the sulculs while a change finish line is being created in tooth
structure. (Described by Ansterdam 1954).
The technique is also called “Gingettage” used with the sub gingival placement of
restoration margins should always be done on healthy, inflammation free tissue to avoid
the tissue shrinkage that occurs when diseased tissue heals.
(Note : Periodontal curettage -> debride diseased tissue from the sulcus to allow re-
epithelization and healing).
Electro surgery :Picture Page 269, 270, Shillinburg, …)
D. Arsonval 1891 – responsible for the development
Electro surgery has been described for the removal of irritated tissue that the has
proliferated over preparation finish lines.
For enlargement of the gingival sulcus and control of haemorrhage to facilitates
impression making
Current flows from a small cutting electrode that produces a high current density and a
rapid temperature vise at its point of contact with the tissue. The cells directly adjacent to
the electrode are destroyed by this temperature increased.
Commonly used electrodes.
- Coagulating
- Biomandibular loop -> crown lengthening
- Round loop -> gingivectomy
- Round loop -> gingivectomy
- Small, straight -> gingival sulcus enlargement
- Small loop
- Contra indications -> cardiac pacemakers
 not be used in presence of flammable agents
 In the presence of nitrous – oxide – oxygen analgesia

25. TECHNIQUES OF IMPRESSIONS MAKING
Double mix technique (Multiple mix technique) The light body material is injected
from the filled syringe within and around the tooth preparation. The tray filled with heavy
body material in inserted in the mouth and seated over the syringe material. The tray
material will fore the syringe material to adapt to the prepared tissues The two materials
bond together on setting, most community used with custom tray.
Advantages
• Over comes the polymerization shrinkage of the light body materials.
• Margins duplicated in light body -> finer details are reproduced.
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 technique (Single viscosity technique, monophase technique)
Medium viscosity of polyether and addition silicones are often used in a stock tray while
making impression with this technique.
Only one mix is made, part of the material placed in the tray and another portion placed
in the syringe for injection in the cavity preparation or on prepared teeth.
Success of this technique depends on the pseudoplastic behavior of these two materials.
Viscosity of a monophase material is a compromise between a low viscosity material that
can flow well and record surface detail with the need for a higher viscosity to prevent
slumping and placement in an impression stock tray.
Advantages
• Reduced mixing -> reduce wastage of the materials
• Less time consumptions
• Avoids the time involved in fabrication of custom tray.
Disadvantages
* Relatively high viscosity and reduced flow of the monophase materials,
makes their injection onto the preparation more difficult to control ->
increased incidence of surface voids (Strephen M. Dunne et al 1998).
PUTTY – WASH TECHNIQUE
Developed is over come the polymerization shrinkage associated with
condensation silicons.
1. Putty wash simultaneously technique (One stage)
light body materials syringed on to the preparation while the putty material loaded
in a stock tray is simultaneously inserted into the mouth and sealed over the light body
materials.
Advantages Reduced chair side time saving of impression materials.
Disadvantages
• Absolute lock of control the bulk of wash materials (Chee and Dunovan 1992).

26. • Posibility of margins duplicated in putty medicine.
• Tendency of bubbles to be formed and occluded in the set impression.
• By mixing putty, syringe material simultaneously, setting distortion of putty
included in over all distortion of impression. Chee and Donovan 1992)
2. Putty wash relief channel technique
- Pre-operative putty impression is made intra orally.
- In the area where the teeth are to be prepared impression material is
removed or channels prepared using putty cutter instrument.
- The impression is then washed on relined with low viscosity material.
Advantages
• Impression can be captured with the wash materials.
Disadvantages
• To confine the wash material to area of relieved impression.
• If entire area is washed -> creates hydraulic displacement of
putty impression resulting in smaller dies. (Bonovan TE 2004)
3. Putty wash 2mm spacer technique
- 2 mm thickness wax spacer is prepared on a diagnostic cast, occlusal steps
are provided on non-functional cusps.
- A putty is made with a stock tray resulting in a putty custom tray with
2mm space for the wash materials.
Advantages
• wash stage cervical 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 a materials.
Copper band technique
- This technique is used to sehvage on impression of multiple preparations
when there are only vague margins on one or two preparations that are not
adequately replicated in the impression.
- Copper tube is prepared that extends 1 mm beyond the finish line.
- Top one – third of copper tube filled with impression compound end
sealed on the preparation.
- Remove 2 mm of compound from the impressed occlusal surface for the
rubber base materials.
Disadvantages
Can cause damage to the attachment apparatus
• Time consuming

27. DUAL ARCH IMPRESSION TECHNIQUE (TRIPLE TRAY TECHNIQUE
CLOSED MOUTH TECHNIQUE)
- This technique captures the prepared teeth, the opposing arch and the
occlusal articulation in maximum intercuspation (MIP) simultaneously.
Indications
• Used with a maximum of two prepared teeth.
• Unprepared stops anterior and posterior to the prepared teeth
should be present.
• Used only with patients that have existing anterior guidance.
• Must be able to close completely in maximum intercuspation
position with the impression tray in place.
Contra Indications
• Presence of third molars.
• Rapidly ascending ramus
• Excess soft tissue distal to the molars
- Rigid metal trays, (Qued trays) as well as rigid PVS or polyether material
should be used.
- Flexible trays (Plastic) should be avoided -> often bucco-lingual width of
the arch is wider than the trays. The resilient tray flexes outward when the
impression is made and rebounds when the impression is removed from
the mouth, thus permanently distorting the impression.
Advantages
• Accurate recording of the MIP.
• Eliminated any mandibular flexure that might be associated with
opening.
Disadvantages
• Complicated laboratory procedure.
Segmental impression technique
To make impressions of multiple prepared teeth due to inherent limits in working time
end difficulties maintaining moisture control.
Arch to be impressed is broken down into segments of two prepared teeth.
Custom tray prepared for each segment with 1mm of wax relief, trays should extend 3
mm post the gingival margin, as there are no occlusal stops and gingival tissue must
prevent over seating of the trays.
Low viscosity material is loaded into the syringe as well as the segmental tray, and then
are impression made. Procedure repeated with each segment.
Finally on over impression is made using a stock tray.
Uses
When moisture control is difficult in specific patients.
When making simultaneously impressions of implants and prepared teeth.

28. Tooth / Implant impressions
Implant copings can reduce access to the prepared teeth and impede the extrusion
of impression material to the margins of the prepared teeth. In such cases, a combination
of custom impression trays to impress the prepared teeth and then place the implant
impression copings and make an over impressions of the arch.
Indirect dowel, cores
Indirect technique of obtaining dowel patterns is indicated when multiple dowel
cores are required or when redicular attachments are to be used.
A 25 gauge local anaesthetic needles is used as a vent to allow cir to escape as the
impression materials is injected into the canal space.
Needle is gradually removed while the low viscosity materials is injected into the
canal.
An appropriately sized plastic impression dowel coated with adhesive is inserted
into the canal.
Procedure is repeated with multiple dowels and finally an over impression is
made.
Pin-retained restorations (Picture Rosei…)
Elastomers are strong enough to reproduce a pinable without tearing. However to ovoid
bubbles, they must be introduced corgully cement tube.
Cement tube : fill the tube and squeeze a small amount of material into each pinhole
make sure no air is trapped by inserting and removing an explorer into the materials.
Centulo : Spiral the material into the pinholes – rotating slowly while moving the
lentulo along the side of the pin-hole.
With reversible hydrocolloid -> special nylon bristles are used to register the pin hole
(should extend 2 mm above the opening of pin hole).
DISINFECTION OF IMPRESSIONS
The dental impression is one of the ways by which pathogens can leave the
operatory and spread their risk abroad.
The impression must be rendered harmless before being passed on to other people
who will work with it or with the gypsum cast made from it, outside the dental operatory.
Chemical disinfectants used for this purpose :
- Chlorine compounds.
- Synthetic phenolic compounds
- Glutaraldehydes
- Iodophors
- Phenolic/ alchoholic combinations
Table 9.4, Page 226 (Annusavica)
Polyethers are susceptible to dimensional changes if immersed for a long time (> 10 min)
-> hydrophilic nature.
Disinfectant can be sprayed on the impression, wrapped in a disinfectant soaked paper
towel and placed in sealed plastic bag for 10 min.

29. Long immersion time may cause the surfactant in hydrophilic PVS to reach out and
vender the impression less hydrophilic. Ultra violet treatment was effective against
candida organisms, and there was not adverse effect on either dimensional change or
surface roughness of impression materials.
Disadvantages with this method, cannot kill micro organisms that are shadowed from the
emission, UV light with should be designed in such a way that the impression, rotates on
the taste and unit surrounded by miwon (Hiroshi Ishiode 1991, JPD)
Concepts for transporting impressions to ……. Laboratory.
1. Send it well cleaned (Rinsed) and undisinfected in a biohazerd – labeled, heat
sealed plastic bag.
OR
2. Debride, clean (rinse) and adequately disinfect it, place it in a sealed transport bag
labeled with the precautions taken.