Impression materials in orthodontics/endodontic courses

 INTRODUCTION
 IDEAL REQUIREMENTS OF IMPRESSION MATERIALS
 CLASSIFICATION OF IMPRESSION MATERIALS
 MATERIALS USED FOR IMPRESSIONS
 ELASTOMERIC IMPRESSION MATERIALS
POLYSULFIDE
 COMPOSITION
 CHEMISTRY & SETTING REACTION
 PROPERTIES
 ADVANTAGES & DISADVANTAGES
www.indiandentalacademy.com

CONDENSATION SILICONE
 COMPOSITION
 PROPERTIES
ADDITION SILICONE
 COMPOSITION
 PROPERTIES
POLYETHER
 COMPOSITION
 PROPERTIES


HYDROCOLLOIDS
 SOL-GEL TRANSFORMATION
 GEL STRENGTH
 DIMENSIONAL EFFECTS
ALGINATE (IRREVERSIBLE HYDROCOLLOIDS)
 COMPOSITION
 GELATION
 CONTROLLING SETTING TIME
 MANIPULATION
 MAKING THE IMPRESSION

 STRENGTH
 ACCURACY
 BIOCOMPATIBILITY
 DISINFECTION
 DIMENSIONAL STABILITY
 SHELF LIFE
 COMPLIANCE WITH GYPSUM
 COMMON CAUSES OF REMAKING THE
IMPRESSION
CONCLUSION
REFERENCES

 A dental impression is a negative record
of the tissues of the mouth. It is used to
reproduce the the form of the teeth and
surrounding tissues by the way of
cast.Constructing a model or cast is an
important step in numerous dental
procedures. Various types of casts and
models can be made from gypsum
products using an impression mold or
negative likeness of a dental structure.
The dentist designs and constructs both
removable and fIxed prostheses on a
gypsum cast. Thus the cast must be an
accurate representation of oral
structures, which requires that the

 They should be fluid enough to adapt to oral tissues.
 They 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 a reasonable amount of time(total
setting time should be less than 7 minutes).
 Set impression should not tear or distort when removed
from the mouth.
 Impression made must remain dimensionally stable at
least until the cast can be poured.
 Impression should maintain its dimensional stability after
removal of a cast so that a second or a third cast can be
made from the same impression.
 The materials should be biocompatible.
 The materials, associated processing equipment &
processing them should be cost effective.

 (1)Non toxic and non irritant
 (2) Acceptability to the patient:
(a)Setting time,
(b)Taste,
(c)Consistency
 (3) Accuracy : both
(a) Surface reproducibility
(b) Dimensional stability
 (4) Use of material :

(a) Ease of mixing
(b) (b) Working time
(c) (c) Setting time
(d) (d) Handling of the material
 (5) Compatible with model materials
 (6) Economics of material
(a) (a) Cheap
(b) (b) Long shelf life
(c) (c) Accuracy (save redoing impression)

 Historically, impression making was accomplished
with inelastic materials for both soft and hard
tissues.
 Hydrocolloid was initially introduced to make
impressions of hard tissues in place of inelastic
materials.
 After World War II, advances in polymer technology
brought to the dental profession a group of
synthetic rubbery materials called elastomers,
which are capable of making impressions of both
soft and hard tissues.

IRREVERSIB
LE
REVERSIBLE
STATE
REACTION
EXAMPLE

Exhibit little or no
elasticity.
Any significant
deformation produces
a permanent
deformation.
Used in mouth with no
undercuts or no teeth
Can be stretched and
bent to a fairly large
degree without suffering
any permanent
deformation.
USED FOR DENTULOUS
IMPRESSIONS,UNDERCUT
S
INELASTIC ELASTIC

 A colloid is a state of matter in which individual
particles of one substance, are uniformly
distributed in a dispersion medium of another
substance.
 When the dispersion medium is water it is termed a
hydrocolloid.
 Sol: The colloid is relatively fluid when the solute
particles present are dispersed throughout the
liquid.
 Gel: The particles can become attached to each
other, forming a loose network which restricts
movement of the solute molecules. The colloid
becomes viscous and jelly like.

Dispersio
n medium

DISPERSIO
N MEDIUM SOLUTE
PARTICLES/DISPER
SED PHASE
GETTING ATTACHED
TO EACH OTHER

The dispersed phase agglomerates to form chains or fibrils, also called MICELLES
FIBRILS may branch and intermesh to form a brush-heap structure
AGAR
ALGINATE
DISPERSION
MEDIUM

REVERSIBLE
IRREVERSIBLE
Reduction in temperature, reversible because sol is
formed again on heating (eg agar).
Chemical reaction which is irreversible (eg alginates).

Hydrocolloids are placed in the mouth in the
sol state when it can record sufficient detail,
then removed when it has reached the gel
state

 The stiffness and strength of the gel are
directly related to the hydrocolloid
concentration.
 The strength of reversible and irreversible
hydrocolloid gels can be increased by the
addition of certain modifiers such as fillers.

Kinetic energy of the fibrils increases,
(1) Greater interfibrillar distances and a
(2) Reduction in their cohesive interaction
GEL HEATED

FORMATION OF
FIBRILS
DISSOCIATION OF
FIBRILS
Liquefaction to SOL state

 STRENGTH not affected by normal temperature
changes, because the fibrils are formed by
chemical action and they do not revert to the
sol condition upon heating.

 SHRINKING OF GEL:
evaporation from its surface
exuding fluid onto the surface (SYNERESIS)
 SWELLING OF GEL:
it absorbs water (by IMBIBITION)

 Imbibition can cause just as much distortion as
syneresis and evaporation.
IMPRESSION
MADE &
REMOVED
FROM MOUTH
CAST POURED
Inaccurate casts and
models
syneresis,
evaporati
on
IMBIBITION

 Developed as a substitute for the agar
impression material when its supply
became scarce during World War II.
 Based on a natural substance, anhydro-
B-d-mannuronic acid or alginic
acid,extracted from certain brown
seaweed.
Easy to manipulate,
comfortable for the patient,
and relatively inexpensive
since it does not require
elaborate equipment.

GLYCERINE

 Type I – Fast Setting
 Type II – Normal Setting

 Reaction of soluble alginate with
calcium sulfate and the formation of an
insoluble calcium alginate gel

 Structurally, calcium ions replace the
sodium or potassium ions of two adjacent
molecules to produce a cross-linked
complex or polymer network .

 K2n Alg + nCaSO4  nK2SO4 + Can Alg
POTASSIUM
SULFATE
CALCIUM
ALGINATE
GEL
POT ASSIUM
ALGINATE
CALCIUM
SULFATE
RAPID PRODUCTION OF CALCIUM ALGINATE  LESS
WORKING TIME

 2Na3PO4 + 3CaSO4  Ca3(PO4)2 +
3Na2SO4
SODIUM
PHOSPHATE
CALCIUM
SULFATE
CALCIUM
PHOSPHATE
SODIUM
SULFATE
•Calcium sulfate will react SODIUM PHOSPHATE in
preference to the soluble alginate.
•Rapid reaction between calcium sulfate and the
soluble alginate is deferred as long as there is
unreacted trisodium phosphate
•PROLONG WORKING TIME.

 16 g of the powder is mixed with 38 mL
of water
Gelation will occur in about 3 to 4 min
at room temperature

FAST SET NORMAL SET
MIXING TIME 45 sec 60 sec
WORKING TIME 1.25 min 2 min
SETTING TIME 1.5 TO 3 min 3 TO 4.5 min

 Amount of retarder. (MANUFACTURING
PROCESS)
 Altering the temperature of the water.
HIGHER THE
TEMPERATUR
E
SHORTER
THE SETTING
TIME
10* RISE IN TEMP
1-MIN REDUCTION IN
SETTING TIME

a
A: higher temperature of water  faster
setting

 Hot weather  PREMATURE GELATION
Cool water
Pre cool the mixing bowl and spatula

Measured powder is sifted into premeasured water
that has already been poured into a clean rubber
bowl.
Water is added first in a rubber bowl :
Wets the bowl
Ensure complete wetting of powder particles
Avoids incorporation of air into the mix

Vigorous figure of 8 motion:
Mix swiped against the sides of the rubber-
mixing bowl with intermittent rotations
(180°) of the spatula to press out air
bubbles
Smooth, creamy mixture that does not readily
drip off the spatula when it is raised from the
bowl
MATERIAL READY FOR LOADING INTO THE IMPRESSION
TRAY

Before seating the impression: Material
should have developed sufficient
body.
Mixture is placed in a suitable
tray.
Which is then placed in the
mouth
SELECTION OF TRAY:
PERFORATED TRAY
ALGINATE TRAY ADHESIVE
(POOR ADHESION)

SUFFICIENT BULK OF
IMPRESSION MATERIAL
(ATLEAST 3MM)

TIME FROM GELATION (MIN) COMPRESSIVE STRENGTH (MPa)
0
4
8
.33
.77
.81
Compressive strength in this case actually doubles during the first
4 min after gelation
DOES NOT increase appreciably after the first 4-min period
COMPRESSIVE STRENGTH OF ALGINATE GEL AS A FUNTION
OF GELATION TIME

 Alginate impression should not be removed
from the mouth for at least 3 min after gelation
has occurred.
 Dont leave in mouth for prolonged duration as
well. (6-7min  distortion)

 FOR REMOVAL: BREAK THE SEAL (suction)
OF THE IMPRESSION AND THEN REMOVE
THE IMPRESSION RAPIDLY OR WITH A
SNAP.
 Avoid torquing or twisting the impression in
an effort to remove it quickly

 Maximum gel strength is required to prevent
fracture and to ensure elastic recovery of the
impression.
 too much or too little water is used in mixing,
the final gel will be weakened, making it less
elastic.
 Insufficient spatulation results in failure of
the ingredients to dissolve sufficiently.
 Overmixing breaks up the calcium alginate gel
network as it is forming and reduces its strength

 Not capable of reproducing the finer details
that are observed in impressions with other
elastomeric impression materials
 Concentration of alginate increased to
make it more accurate.
 Nevertheless, alginate materials are sufficiently
accurate that they can be used for making
impressions for orthodontic purposes.

 No known chemical or allergic reactions are
associated with alginate hydrocolloid
impressions.
 Inhaling fine airborne particles from alginate
impression material can cause silicosis and
pulmonary hypersensitivity.

Current protocol for disinfecting alginate hydrocolloid
impressions recommended by the Center for
Disease Control
A 10 MIN SOAK IN 0.5% SODIUM HYPOCHLORITE
A 20 MIN SOAK IN 2% GLUTARALDEHYDE DILUTED 1:4.
Household Bleach (1 to 10 dilution)

 Impression Exposed to air -> syneresis
and evaporation->shrinkage.
 Impression is immersed in water -> imbibition
-> swelling of impression.
 100% relative humidity is the best storage
environment to preserve the normal water
content of the impression.
 Thermal changes

a b
A: linear contraction in air
B: expansion in water

 Sodium sulfate(formed during gelation). a
gypsum retarder at higher concentration.
Decreased surface hardness of cast.
 Overcome by:
(1) by immersing the impression in a solution
containing a gypsum accelerator, such as
2% potassium sulfate solution, prior to
pouring the impression with the gypsum-
forming product; or (2) by using products that
incorporate a gypsum hardener or
accelerator in the material.(potassium
titanium fluoride )

 Excess rinsing water on the surface of the
impression  rough stone surface.
 The surface of the impression should be shiny
but with no visible water film or
droplets at the time the impression is poured
with model or die material.

 Moisture contamination from the air.
Individual sealed pouches are preferred.
The lid should be firmly replaced on the container
Stored in a cool, dry environment.

 TASTE AND ODOR: PLEASANT TASTE AND
SMELL
 REPRODUCTION OF TISSUE DETAIL: GOOD
 ADHESION: POOR ADHESION.REQUIRE
PERFORATED TRAYS TO TAKE IMPRESSION
 ELASTIC RECOVERY: 98.5%.
 FLEXIBILITY: 8 – 15%
 STRENGTH:
COMPRESSIVE STRENGTH – 5000 TO 8000
gm/cm2

 ADVANTAGES
1. Non toxic and non irritant
2. Good surface detail
3. Ease of use and mix
4. Cheap and good shelf life
5. Setting time can be controlled with temperature
of water used
 DISADVANTAGES
1. Poor dimensional stability
2. Tear strength less

 HOWEVER IT IS ALSO AVAILABLE IN THE
FORM OF A SOL CONTAINING THE WATER
BUT NO SOURCE OF CALCIUM IONS. A
REACTOR OF PLASTER OF PARIS CAN THEN
BE ADDED TO THE SOL.
 ANOTHER FORM AVAILABLE IS THE TWO
COMPONENT SYSTEM IN THE FORM OF
TWO PASTES: ONE CONTAINS THE
ALGINATE SOL AND THE OTHER CONTAINS
THE CALCIUM REACTOR. THESE TYPE OF
MATERIALS MAY ALO CONTAIN SILICONE
AND MAY BE SUPPLIED IN BOTH TRAY AND

 Dust free alginates
 Chromatic alginates
Color change-changes color when
mixed with water, but changes back
to original color while approaching
final setting.

 Blendex™ automatic alginate mixer delivers
smooth, bubble-free, consistent mixing.

 Effect of Mixing Methods on Mechanical
Properties of Alginate Impression
Materials
Gary Frey, DDS 1
; Huan Lu, DDS, PhD 1
; and
John Powers, PhD 2
 The mechanical mixer improved elastic
recovery and compressive strength of the
alginate impression materials tested

 B.DOUBLEDAY, ORTHODONTICS PRODUCTS
UPDATE,IMPRESSION MATERIALS, BRITISH JOURNAL OF
ORTHODONTICS, MAY 1998 PG 133-140.
COMPARED 15 ALGINATES & 13 SILICONES
Result: ideal(GAC) performed the best with
Kromopan(lascod), kent dental, Xantalgin(bayer) also
scoring high.
Adults preferred mint flavor while youngsters preferred
vanilla.
Best results for cleft patient’s impression:
Perfexil(septodont), Elite H-D( Zhermack)
Addition silicones were better, condensation silicones
tended to be messier & difficult to mix.

 First introduced in the late 1950s
 They significantly reduced the two main problems
associated with the hydrocolloids, namely poor
dimensional stability and inadequate tear
resistance
 Used where a high degree of accuracy is needed
 Elastomers refer to a group of rubbery polymers,
which are either chemically or physically cross-
linked.
 They can be easily stretched & rapidly recover
their original dimensions when the applied stress
is released.

 They are mainly hydrophobic rubber based
materials.
 All of these materials come in different
viscosity's ranging from low to high
viscosity.
 The light bodied material maybe used as a
wash impression over a medium or heavy-
bodied material.

 DIMENSIONALLY STABLE
 ACCURACY
 TEAR RESISTANCE...UNDERCUTS
 GOODD REPRODUCTION OF DETAILS IN CAST
 MULTIPLE POURS CAN BE MADE
 IMPRESSION CAN BE KEPT FOR LONG &
REUSED.
 CLEFT PATIENTS

 According to ANSI/ADA Specification No.
19
 Polysulfides
 Silicones
 Polyethers
Each type is further divided into four viscosity
Classes
light-body,
medium-body or regular-body,
heavy-body,
putty

 MULIPLE MIX TECHNIQUE/DUAL VISCOSITY
Light bodied impression material is placed in a syringe, and
placed over the areas where high detail is required (e.g.
over a crown preparation). Some is then squirted over the
heavy-bodied impression material which has been loaded
into an impression tray. The impression is then taken as
normal. This technique saves time, but it can be very labour
intensive because the two need to mixed at the same time.
 SINGLE VISCOSITY
TECHNIQUE/MONOPHASE(POLYETHER, ADD SILICONE)
 TWO STAGE IMPRESSION (PUTTY WASH) (COND
SILICONE)
An impression is taken with the PUTTY material. This is then
removed from the mouth and inspected. The light bodied
material is then prepared and again placed in a syringe.
This is then squirted over PUTTY material and then
impression relocated.

 IT IS THE FIRST NON AQUEOUS ELASTOMERIC
RUBBER IMPRESSION MATERIAL.
 ALSO KNOWN AS MERCAPTAN OR THIOKOL
OR VULCANIZING IMPRESSION MATERIAL.

 A TWO PASTE SYSTEM. [BASE PASTE AND
CATALYST PASTE]
 IT IS AVAILABLE IN THREE VISCOSITIES:
 LIGHT
 MEDIUM
 HEAVY
VISCOSITY INCREASING FROM LIGHT TO HEAVY
BODY.

 Type 1: heavy body for mandibular dentulous
impressions and tissue displacive edentulous
impressions
 Type 2: medium (regular) body for routine
dentulous impressions
 Type 3: light body for dentulous impressions
(syringe material) and for some mucostatic
edentulous Impressions.

BASE PASTE
 POLYSULFIDE POLYMER . (80-85%)(forms rubber on
polymerisation)
 SUITABLE INERT FILLER (LITHOPONE AND TITANIUM
OXIDE, ZINC SULPHATE, COPPER CARBONATE) TO PROVIDE
STRENGTH & BODY. (16-18%)
 PLASTICIZER (DIBUTYL PHTHALATE)- FOR APPROPRIATE
VISCOSITY
CATALYST OR ACCELERATOR PASTE
 LEAD DIOXIDE- PRODUCE A CHARACTERISTIC DARK
BROWN COLOR. (60-68%)(causes polymeristaion & cross
linking)
 PLASTICIZER. (30-35%)
 FILLER. (PROVIDE STRENGTH & BODY)
 SULFUR REACTOR (3%) facilitates the reaction
 RETARDER-OLEIC/STEARIC ACID- (CONTROL THE RATE

IT IS THE CONDENSATION REACTION IN WHICH THE -SH GROUPS OF
POLYFUNCTIONAL MERCAPTAN ARE CROSS LINKED WITH AN OXIDIZING AGENT
SUCH AS LEAD DIOXIDE

 TWO PHENOMENONS OCCUR:
 CHAIN LENGTHENING POLYMERIZATION
FROM THE REACTION WITH THE TERMINAL SH
GROUP
 CROSS LINKING FROM THE REACTION WITH
THE PENDANT –SH GROUP.
 .

 INITIALLY, THE POLYMERIZATION REACTIONS RESULT IN
CHAIN LENGTHENING, WHICH CAUSES THE
VISCOSITY TO INCREASE.
 THE SUBSEQUENT CROSS LINKING REACTIONS TIE
THE CHAINS TOGETHER FORMING A 3 DIMENSIONAL
NETWORK THAT CONFERS ELASTIC PROPERTY OF
THE MATERIAL.
 DURING THE FINAL SET, A MATERIAL OF
ADEQUATE ELASTICITY AND STRENGTH IS
FORMED THAT CAN BE REMOVED OVER THE
UNDERCUTS QUITE READILY.
 EXOTHERMIC REACTION WITH 3-4 DEGREE RISE IN
TEMP.

WORKING TIME CAN BE INCREASED BY-
 COOLING- STORING THE MATERIAL AT LOW ROOM
TEMPERATURE, MIXING ON A CHILLED AND DRY GLASS
SLAB
 OLEIC ACID IS AN AFFECTIVE RETARDER.
WORKING TIME CAN BE DECREASED BY-
 INCREASING THE TEMPERATURE.
 ADDING A DROP OF WATER.

 THE MATERIAL UNDERGOES DIMENSIONAL
CHANGES ON SETTING. THEY EXHIBIT A
SHRINKAGE OF 0.45%.
 DIMENSIONAL CHANGES OVER TIME ARE
GREATEST IN POLYSULFIDE MATERIAL AS
COMPARED TO POLYETHER AND ADDITION
SILICONES.
 IT HAS THE HIGHEST PERMANENT DEFORMATION
AMONGST ALL THE ELASTOMERIC IMPRESSION
MATERIALS.,APPROX. 3 – 6% AND HAS AN ELASTIC
RECOVERY OF 94 – 97% APPROX.

 RHEOLOGY: ONE OF THE LEAST STIFF
MATERIALS. THE FLEXIBILITY [7%] ALLOWS THE
SET MAETRIAL TO BE RELEASED FROM UNDERCUT
AREAS WITH MINIMUM STRESS.
 TEAR STRENGTH: THEY HAVE HIGHEST TEAR
RESISTANCE. 3000 – 7000 g/cm.
 BIOCOMPATIBILITY: GOOD BIOCOMPATIBILITY.
 DISINFECTION OF IMPRESSION MATERIAL:
A 10 MIN IMMERSION IN A 10 % SOLUTION OF
SODIUM HYPOCHLORITE.
 SHELF LIFE: THE SHELF LIFE IS GOOD (2YRS).
 UNPLEASANT TASTE AND ODOUR.

CAST:
EXCELLENT REPRODUCTION OF SURFACE
DETAILS. CAN REPRODUCE A GROOVE 0.020
mm IN WIDTH.
IT CAN BE ELECTROPLATED.

SILICONE ELASTOMERSSILICONE ELASTOMERS
 Polymers of silicone and oxygen atoms → polysiloxanePolymers of silicone and oxygen atoms → polysiloxane

SUPPLIED AS:
 TWO PASTE SYSTEM OF UNEQUAL SIZES. BASE PASTE IN LARGER
TUBE.
 PUTTY WHICH IS SUPPLIED IN A JAR.
 THREE CONSISTENCIES:
 LIGHT, MEDIUM AND PUTTY.
COMPOSITION
BASE:
 POLY DIMETHYL SILOXANE.
 COLLOIDAL SILICA OR MICROSIZED METAL OXIDE FILLER PARTICLES
SIZED 2-8µm ARE ADDED [ TO FORM A PASTE]. (35-79%)

ACCELERATOR:
 ORTHOETHYL SILICATE [CROSS LINKING AGENT]
 STANNOUS OCTOATE [CATALYST]

POLYDIMETHYL
SILOXANE.
(SILICONE POLYMER)
ORTHOETHYL
SILICATE
(ALKYL SILICATE)
TERMINAL GROUP
CONDENSATION REACTION
SILICONE ETHYL

 SETTING TIME: IS 6-8 MIN.WORKING TIME IS 2.5 – 4 MIN. AND
MIXING TIME IS 45 SEC.
 ELASTICITY: THEY ARE NOT VERY STIFF. EXHIBIT MINIMAL
PERMANENT DEFORMATION AND RECOVER IMMEDIATELY WHEN
STRAINED. FLEXIBILITY – 0.05- 1%.
 PERMANENT DEFORMATION AND ELASTIC RECOVERY:
PERMANENT DEFORMATION IS 1-3%. ELASTIC RECOVERY IS 97-99%.
(MORE THAN POLYSULFIDES)
 DIMENSIONAL STABILITY: IT IS LESS BECAUSE OF THE CURING
SHRINKAGE OF 0.4% - 0.6% AND SHRINKAGE DUE TO EVAPORATION
OF ETHYL ALCOHOL. CASTS SHOULD BE POURED IMMEDIATELY.
 RHEOLOGY: THESE MATERIALS RESPOND ELASTICALLY WHEN
STRAINED RAPIDLY,HENCE IMPRESSIONS MUST BE REMOVED
RAPIDLY.
 TEAR STRENGTH: IT HAS A LOW TEAR RESISTANCE OF 3000 g/cm.
APPLYING A FORCE RAPIDLY ENSURES A HIGHER TEAR RESTSIANCE.

 IT IS HYDROPHOBIC.
 CAN BE COPPER OR SILVER PLATED.
 BIOCOMPATIBILITY: IT IS ONE OF THE MOST
BIOLOGICALLY INERT MATERIAL.
 SHELF LIFE: LESS BECAUSE OF VOLATILE
NATURE OF THE ORTHO ETHLY SILICATES.
 DISINFECTION.

KNOWN AS POLY VINYL SILOXANE
IMPRESSION MATERIALS.
SUPPLIED AS:
 PASTE SYSTEM- BASE AND CATALYST PASTES IN
EQUAL SIZED TUBES.DIFFERENT VISCOSITIES
COME IN DIFFERENT COLORS.
 PUTTY JARS- TWO JARS,EUQAL SIZED
CONTAINING BASE AND ACCELERATOR.
AVAILABLE IN FOUR VISCOSITIES-
LIGHT, MEDIUM, HEAVY BODIED AND PUTTY.

 BASE-
 POLY METHYL HYDROGEN SILOXANE.
 OTHER SILOXANE PREPOLYMERS.
 FILLRES.
 CATALYST-
 DIVINYL POLYSILOXANE
 OTHER SILOXANE PREPOLYMERS.
 PLATINUM SALT[CATALYST]
 RETARDERS AND FILLERS.

VINYL MOLECULES
no byproductno byproduct
nono
polymerizationpolymerization
contractioncontraction POLYVINYL SILOXANE

•ELASTICITY
MOST IDEALLY ELASTIC OF THE CURRENTLY AVAILABLE MATERIALS.
•ELASTIC RECOVERY AND PERMANENT DEFORMATION: PERMANENT DEFORMATION
IS 0.05 – 0.5%. IT HAS AN ELASTIC RECOVERY OF 99.5%.
•DIMENSIONAL STABILITY: MOST DIMENSIONALLY STABLE MATERIAL. CURING
SHRINKAGE VALUE OF 0.17%.
•RHEOLOGY: IT IS ONE OF THE MOST PSEUDOPLASTIC MATERIAL.
•TEAR STRENGTH: IT IS MORE OR LESS SIMILAR TO CONDENSATION SILICONES WITH A
VALUE OF 4300 g/cm.
BIOCOMPATIBILITY.
DISINFECTION.
SHELF LIFE: UPTO 2 YRS.
IT CAN BE ELECTROPLATED.

 INTRODUCED IN GERMANY IN LATE 1960.
 THESE SYSTEMS OFFER THE POSSIBLE
COMBINATION OF MECHANICAL PROPERTIES
BETTER THAN THOSE OF POLYSULFIDES
WITH LESS DIMENSIONAL CHANGE THAN
THOSE OF CONDENSATION SILICONE

 PASTE SYSTEM: BASE AND ACCELERATOR IN
COLLAPSIBLE TUBES.
 THINNER
 AVAILABLE AS THREE VISCOSITIES:
LIGHT,MEDIUM AND HEAVY BODIED.

 BASE PASTE
 POLYETHER POLYMER.
 COLLOIDAL SILICA [FILLER].
 GLYCOETHER OR PTHALATE [PLASTISIZER]
 ACCELERATOR PASTE
 ALKYL-AROMATIC SULFONATE ESTER.
 COLLOIDAL SILICA AND GLYCOETHER.

•ELASTICITY: STIFFEST IMPRESSION MATERIALS[FLEXIBILITY OF 3%]. EXTREMELY
DIFFICULT TO REMOVE FROM UNDERCUT AREAS. HOWEVER REGULAR OR MEDIUM BODY
MATERIAL ARE LESS STIFF.
•ELASTIC RECOVERY AND PERMANENT DEFORMATION: IT HAS A PERMANENT
DEFORMATION OF 1.5 – 2%. IT HAS A RECOVERY OF 99%.
•DIMENSIONAL STABILITY: DIMENSIONAL CHANGES ARE SMALL.. CURING
SHRINKAGE VALUE OF 0.2%.
•RHEOLOGY: THE PSEUDOPLASTIC CHARACTERISTIC ALLOWED THE ORIGINAL SINGLE-
VISCOSITY MATERIAL TO BE USED AS BOTH SYRINGE AND TRAY MATERIALS.
•TEAR STRENGTH: IT IS MORE PRONE TO TEARING THAN POLYSULFIDE. [3000g/cm]
BIOCOMPATIBILITY: CONTACT DERMATITIS FROM THE POLYETHER HAS BEEN
REPORTED. MAJOR CONCERN IS WITH THE IMPRESSION MATERIAL BEING LEFT IN THE
SULCUS. THE IRRITATION CAN RANGE FROM MINOR TO SEVERE.

 SHELF LIFE: IS MORE THAN TWO YEARS
WHEN STORED IN A COOL DRY ENVIRONMENT.
 HOWEVER, CHILLED POLYETHER IMPRESSION
MATERIAL BECOMES RIGID AND CANNOT BE
MIXED.

ADVANTAGES
 Accuracy
 Good on undercuts
 Ease of use
DISADVANTAGES
 May cause allergic reaction due to the sulphonic acid
ester
 Poor tear strength
 Rapid setting time (ie short working time)
 Stiff set material (sometimes hard to remove from
mouth)

Dimensional stability (from best to worst)
 addition silicones>polyethers>polysulfides>condensation
silicones>hydrocolloids
Setting Time (from longest to shortest)
 polysulfides>silicones>polyethers
Tear Strength (from greatest to least)
 polysulfides>addition silicones>condensation
silicones>polyethers
Stiffness (from most to least)
 polyethers>addition silicones>polysulfides>condensation
silicones
Wettability (from best to worst)
 polyethers>addition silicones>polysulfides>condensation
silicones

 AN AUTOMATIC MIXING AND DISPENSING
DEVICE.
 USING THIS DEVICE, THOROUGH MIXING OF HIGHER
VISCOSITY MATERIALS CAN BE ACHIEVED WITH LITTLE
EFFORT.
 THE DEVICE USES A MOTOR TO DRIVE
PARALLEL PLUNGERS THAT FORCE THE
MATERIAL INTO THE MIXING TIP, AND THE
SPIRAL INSIDE THE MIXING TIP ROTATES AS
THE MATERIAL IS EXTRUDED THROUGH THE TIP

 IT CONSISTS OF A DOUBLE BARREL CAULKING
GUN WITH A STATIC MIXING TIP.
 THE TIP CONTAINS SPIRALS ON THE INSIDE.
 FORCING THE BASE AND ACCELERATOR
THROUGH THESE SPIRALS RESULTS IN MIXING.

 GREATER UNIFORMITY IN PROPORTIONING
AND MIXING.
 LESS AIR IS INCORPORATED INTO THE MIX.
 MIXING TIME IS REDUCED.
 FEWER POSSIBILITIES OF CONTAMINATION

Polyether precision impression material that is
accurate and hydrophilic, resulting in
outstanding detail even in a moist environment

Polyether precision impression material medium
viscosity and is intended for use in the
monophase technique.

 A dental impression is a negative
record of the tissues of the mouth,used
to reproduce the the form of the teeth
and surrounding tissues by the way of
cast.
 Constructing a model or cast is an
important step in numerous dental
procedures.
 A sound understanding of the
impression materials is required to
achieve good impressions made in the
orthodontic clinic.

 ANUSAVICE(2003) PHILLIPS’ SCIENCE OF DENTAL MATERIALS, 11TH
EDITION, PG- 205-253.
 B.DOUBLEDAY, ORTHODONTICS PRODUCTS UPDATE,IMPRESSION
MATERIALS, BRITISH JOURNAL OF ORTHODONTICS, MAY 1998 PG
133-140.
 Trends in sterilization and disinfection procedures in orthodontic
offices
 Source: AJO-DO on CD-ROM (Copyright © 1998 AJO-DO), Volume
1990 Oct (292 - 299): Trends in sterilization and disinfection
procedures – Cash
 SHANON T. KIRCHHOFF, DDS, ROBERT K. SEKIJIMA, DDS, MARK I.
MASUNAGA, DDS, CYRUS M. ALIZADEH, Source: JCO on CD-ROM
(Copyright © 1998 JCO, Inc.), Volume 1987 May(326 - 336):
Sterilization in Orthodontics .
 CRAIG’S , RESTORATIVE DENTAL MATERIALS , 12TH
EDITION, PG 269-
275

Impression materials in orthodontics/endodontic courses

More Related Content

What's hot

Viewers also liked

Similar to Impression materials in orthodontics/endodontic courses

More from Indian dental academy

Recently uploaded

Impression materials in orthodontics/endodontic courses