elastomeric impression materials

1. ELASTOMERIC IMPRESSION MATERIALS
PRESENTED BY
DR. SHAILJA SHARDA
MDS – I
DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE
BHARATI VIDYAPEETH DEEMED TO BE UNIVERSITY

2. DEFINITION
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
chemically or physically cross-
linked; generally, they can be easily
easily stretched and rapidly
recover their original dimensions
when applied stresses are released.

3. DEVELOPMENT
1950s
1955
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.
First elastomeric impression
material - Polysulfide
Condensation
silicone

4. IDEAL REQUISITES
Sufficiently fluid to
adapt to the oral
tissues
Viscous enough to be
contained in a tray
Able to transform (set)
into a rubbery or rigid
solid in the mouth in a
reasonable time (less
than 7 min).
Resistant to distortion
or tearing when
removed from the
mouth,
Dimensionally stable
long enough to allow
one or more casts to
be poured.
Biocompatible
Cost-effective in terms
of time as well as the
expense of the
associated processing
equipment.

5. CLINICAL
APPLICATION
 1) Impression material for all applications including
- Fixed partial dentures
- Dentulous and edentulous impressions
 2) Border moulding of special trays(polyether)
 3) Bite registration
 4) As duplicating material for refractory casts

6. INTRODUCTION TO ELASTOMERIC IMPRESSION MATERIALS
Also called as Rubber Base
Impression materials.
Elastomers are rubber like
materials with long chained
polymers, slightly crosslinked
& coiled having glass
transition temperature much
lower than room
temperatures.
Accepted in dentistry to
overcome 2 main problems
associated with Hydrocolloids
:
Poor tear resistance Poor dimensional stability

7. ELASTOMERIC
IMPRESSION
MATERIALS
Elastomers are of 3 types
1) POLYSULPHIDE
2) SILICONES :
a) Addition Silicones
b) Condensation Silicones.
3) POLYETHERS :
a) Light activated polyethers.
b) Chemically activated polyethers.

8. POLYSULPHIDES
First elastomeric
impression material to
be introduced.
Alternate names: a) Thiokol impression
material (By the name
of first manufacturer)
b) Mercaptan impression
material (by chemistry)
c) Vulcanizing
impression material (by
processing terminology).
Viscosities – light,
medium, heavy.
Commercial names -
permlastic, coe-
flex, omniflex.

9. COMPOSITION
THE BASE
Polysulphide polymer (-SH, mercaptan group) Principal ingredient
Titanium oxide and zinc Fillers
Sulphate, copper carbonate or silica Strengthener
Dibutyl pthalate Plasticizer
THE ACCELERATOR
Lead dioxide Reactor, gives it characteristic brown colour
Sulphur Promoter, accelerates the reaction
Oleic acid or Stearic acid Reactor, controls setting reaction

10. PROPERTIES
BIOLOGICAL:
1) Non toxic, non
poisonous.
2) Bad odor due to
lead dioxide &
Mercaptan group.
3) Easy to disinfect
(glutaraldehyde)
RHEOLOGICAL
PROPERTIES:
1) Available in variety
of viscosities (Low,
Medium, Heavy in
increasing order of
filler content)
2) Working time = 3-
6 min
3) Setting time = 10-
20 min.

11. PROPERTIES
MECHANICAL
PROPERTIES:
1) Highly flexible of all
the elastomers.
2) Elastic recovery
improves with time
(viscoelasticity).
3) High tear strength.
4) Not dimensionally
stable. Curing shrinkage
– high and continues
after setting ; highest
permanent deformation.
5) Hardness increases by
increasing filler content.
Hydrophobic.

12. 1) LONGER WORKING
TIME.
2) HIGHEST
FLEXIBILITY.
3) HIGHEST TEAR
STRENGTH.
4) CAN BE
ELECTROPLATED
WITH SILVER.
5) LONG SHELF LIFE. 6) INEXPENSIVE AS
COMPARED TO
OTHER ELASTOMERS.
ADVANTAGES

13. DISADVANTAGES
1) Unpleasant
odour and taste.
2) Long setting
time.
3) Dimensional
change due to
loss of by-
product.
4) Cloth staining.
5) Multiple die
pouring not
accurate.

14. POLYETHER
 Polyether was introduced in Germany in 1960.
 Commercial names are, Impregum, Remitec, Polyjel etc.
 Polyether is available in 3 viscosities (Light, Regular and heavy
body)
 Dispensed as 3 paste system
 1) Base paste.
 2) Reactor/Accelerator paste.
 3) Modifier (thinner) paste.

15. COMPOSITION
BASE
Polyether polymer Cross-linked to form rubber
Colloidal silica Acts as filler
Glycol (ether) or pthalate Plasticizer
ACCELERATOR
Alkyl aromatic sulfonate Initiates cross-linking
Colloidal silica Filler
Pthalate Plasticizer

16. PROPERTIES
BIOLOGICAL:
1) Nontoxic, Non poisonous.
2) Pleasant Odor and Colour
3) Can cause irritation due to presence of aromatic sulphonic acid catalyst in
reactor paste.
4) Can cause hypersensitivity in some patients due to presence of ethylene
imine rings in base paste.
RHEOLOGICAL:
1) Available in 3 consistencies (L,R & Heavy body)
2) Flow after 1 hour is < 0.03%

17. MECHANICAL
PROPERTIES
1) Elastic recovery
=98.9%
2) Permanent
deformation is 0.8-
1.6%
3) Flexibility is low
(3%)
4) Mixing time is
45 sec to 1 minute.
5) Working time is
2 minutes; Setting
time is 6-
8 minutes.
6)hydrophilic
7) Good
dimensional
stability due to
a) Addition
polymerization
reaction.
b) Less
polymerization
shrinkage.

18. ADVANTAGES
Good pseudoplastic
properties i.e. same
mixture can be used
as tray as well as
syringe material.
Dimensionally stable.
Less polymerization
shrinkage.
No by product
formed.
Pour more accurate
casts.
Multiple cast pouring
is possible.
Cast pouring can be
delayed for few
hours, even a week.
Long shelf life.

19. Catalyst can
be sensitive to
some patients.
Electroplating
not easy.
Low tear
strength.
High stiffness.
Very expensive
when
compared with
other
elastomers.
DISADVANTAGES

20. LIGHT ACTIVATED
POLYETHER
 It was introduced in
1988.
 Available in 2
viscosities.
Light body supplied in
syringes.
Heavy body supplied
as tubes
INGREDIENT FUNCTION
Urethane
dimethacrylate
elastomer resin
Visible light curing
polyether
Champhoroquinone Photoiniator
Dimethyl amino ethyl
methacrylate
Photoaccelerator
Silicon dioxide Fillers

21. Excellent elasticity.
It has operator
control over the
polymerization.
Infinite working
time.
Short setting time.
Low volume
shrinkage on
setting.
Impression can be
stored upto 2
weeks.
PROPERTIES

22. CONDENSATION SILICONE

23. INTRODUCTION
First type of silicone
material ; also known
as conventional
silicone.
Also known as RTV
silicone (room
temperature
vulcanization
silicone)
Available as : - Two- paste system
- Base paste(larger)
and catalyst
paste (smaller tube)
- Two putty system.
Viscosities - light,
medium, putty.
Commerical names -
Sil 21, coltex

24. COMPOSITION
BASE CATALYST
• Polydimethyl siloxane - undergoes cross
linking to form rubber
• Colloidal silica – filler
• Colour pigments
• Tetra ethyl alkyl silicates
• Stannous octoate

25. SETTING REACTION
Dimethyl siloxane
+
Orthoethyl silicate
Silicone rubber
+
Ethyl alcohol

26. PROPERTIES
Biological : non-
toxic.
pleasant color
and odor.
Mechanical:
Stiffer than
plosulfide.
Dimensional
stability: poor
due to loss of by-
product.
Hydrophobic
Setting time: 6-9
mins, mixing
time: 45s

27. ADDITION SILICONE

28. INTRODUCTION
Also called polyvinyl
siloxane or vinyl poly-
siloxane impression
material, most widely
used elastomer.
They have better
properties than
condensation silicone.
Available in four
viscosities : Light
bodied, medium
bodied , heavy
bodied and putty.
Commercial names-
reprosil, provil,
president.
Supplied as- tubes
(base& catalyst),
cartridges form with
static mixing tips,
Putty jars

29. COMPOSITION
BASE ACCELERATOR
• Polymethylhydrosiloxane
• Divinylpolysiloxane
• Fillers
• Divinylpolysiloxane
• Platinum
• Fillers
• Palladium

30. SETTING REACTION
No reaction byproduct unlike condensation silicone
Residual polymethylsiloxane can undergo secondary reaction with each other or with
moisture and produce hydrogen gas
They do not affect the dimensional stability ; but can cause pinpoint voids in the
gypsum casts
Palladium is added in the catalyst paste which acts as hydrogen scavenger.

31. PROPERTIES
Biological: avoid
skin contact, can
cause allergic
reaction.
Plesant odor
& color.
Mechanical:
Best dimensional
stability.
Hydrophobic, added
surfactant makes it
hydrophilic.
Setting time: 5-9
mins, mixing time:
45s

33. MAKING
IMPRESSIONS

34. Preparing
a tray
01
Managing
tissue
02
Preparing
the
material
03
Making an
impression
04
Removing
the
impression
05
Preparing
stone casts
and dies
06
STEPS IN MAKING IMPRESSION :

35. IMPRESSION TRAYS
Stock tray or custom tray
can be used to record
impression
Custom tray allows
uniform distribution of
material between the
tray and the object that
improves accuracy
Addition silicone doesn’t
need custom tray,
disposable stock tray
can be used
Prior to making an
impression uniform
thickness of tray
adhesive is applied on
the tray and allowed to
dry

36. MIXING
SYSTEMS
3 types of systems are available to
mix catalyst and base thoroughly.
1. Hand mixing system.
2. Static mixing system.
3. Dynamic mechanical mixing
system.

37. 1. Impression pastes
are dispensed from
collapsible tubes.
2. Equal lengths of
catalyst and base
paste are dispensed
on a paper pad.
3. Initial mixing is
accomplished with
a circular motion.
4. Final mixing is
done with broad
strokes of spatula.
5. Final mix should
be smooth.
6. Mixing is readily
accomplished in 45
seconds.
All 4 types of
elastomers are
available for mixing
in this fashion.
HAND MIXING SYSTEM

38. 2. STATIC MIXING
This technique transforms two fluid material into a homogenous mix
Mixing is done with a help of a gun with two-cylinder cartridge, and a mixing tip
Porosities due to mixing with air can be avoided as no mechanical mixing is involved
It provides greater uniformity in proportioning and mixing, yields fewer voids in the mix and
reduces the mixing time
Lesser possibilities of contamination of the material
Mixed material is directly injected into adhesive coated tray or onto the prepared teeth

40. 3. DYNAMIC
MECHANICAL
MIXING
The device uses a motor to drive parallel
plungers, forcing the materials into a mixing
top and out into an impression tray or syringe
Thorough mixing of the higher viscosity
materials can be achieved by minimal effort
Both polyether and addition silicone
impression materials of various viscosities are
available with this dispensing system

42. MAKING AN IMPRESSION
MULTIPLE MIX TECHNIQUE
• Light body and heavy body are used in this technique
; mixed by different person. But with the mechanical
devices it can be done by single person
• Lighter material is injected from the static mixing gun
within and around the tooth preparation. Filled tray is
then inserted in the mouth and seated over the
syringe material
• If partially set material is seated, it will be
compressed elastically and cause spring back of the

43. 1. Often taken with medium viscosity material.
2. When forced through impression syringe, the viscosity
decreases but when used with tray the viscosity is
unaffected.
3. Addition silicones and Poly ethers are well suited for
this technique.
SINGLE VISCOSITY
TECHNIQUE (Monophase):

44. PUTTY WASH TECHNIQUE
Originally developed for condensation
silicone to minimize the dimensional
changes
Preliminary impression made with thick
putty material ; will serve as intra oral
custom made tray
Space for the light body is then provided
by this polyethylene sheet as a spacer or
by cutting away some of the putty
Then thin consistency wash material is
placed into the putty impression and on to
the preparation, then the tray is seated

46. REMOVAL OF THE IMPRESSION
Viscoelastic property
of the elastomers have
to be considered
01
It is necessary to use a
quick snap to
minimise plastic
deformation of the
impression
02
Should not be
removed until the
curing has progressed
sufficiently to provide
adequate elasticity to
prevent distortion
03

47. DISINFECTION
Rubber impression materials
: 10 mins in 2%
Glutaraldehyde, 3 mins
in Chlorine compounds;
other disinfectants-
iodophors and phenolics can
be used.
Disinfection time should be
short to prevent any loss of
surface quality or accuracy
Long immersion may cause
the surfactant in the
hydrophilic polyvinyl
siloxane to leach out.

48. RECENT ADVANCES

49. VINYL POLYETHER SILOXANE
• Combination of polyether and polyvinylsiloxane
• This new elastomer boasts of immediate hydrophilicity, at the same time
combining favourable characteristics of both polyether and vinyl poly-
siloxane.
• Optimized elastomeric properties: dimensionally accurate recovery and
easy removal from the mouth.

51. REFERENCE
 Impression materials, Phillips' science of Dental
Materials
 Elastomeric Impression materials, Basic Dental
Materials, John J. Manappallil
 Vinyl polysiloxane ether : a breakthrough in elastomeric
impression materials, Dr. Mohan Shetty, Dr. Ganesh R.
Bhandari, Dr. Deepak Mehta
 Comparative evaluation of dimensional accuracy of
addition silicone and condensation silicone impression
materials - An invitro study, Dr. Pramod Joshi, Dr, Bhat
GS, Dr. Shenoy V

52. THANK YOU!