The document provides an overview of elastomeric impression materials. It begins with an introduction and definitions of key terms like elastomer and elastomeric impression materials. It then discusses the history and classifications of impression materials. The document outlines the ideal requirements for impression materials and their clinical applications. It describes the properties and composition of various elastomers like polysulfide, condensation silicone, addition silicone, and polyether. It discusses recent advances in impression materials and effects of mishandling impressions. In conclusion, the document provides a comprehensive review of elastomeric impression materials.

1. PRESENTED BY,
Dr. ARUNIMA UPENDRAN
1ST YEAR
MDS
1

2.  Introduction
 Definition
 History
 Classification
 Ideal requirements
 Clinical application
 Properties
 Elastomers
 Recent advances
 Impression making with elastomers
 Effects of mishandling
 References
 conclusion
2

3.  Impression materials are used to produce the accurate replicas
of intraoral tissues.
 There are a wide variety of impression materials available each
with their own properties, advantages and disadvantages.
 Materials in common use can be classified as elastic or non-
elastic according to the ability of the set material to be
withdrawn over undercuts.
3

4. Elastomer : a polymer that has a glass
transition temperature that is below its service
temperature (usually room temperature);
these materials are characterized by low
stiffness and extremely large elastic strains
Elastomeric impression material: a group of
flexible chemical polymers that are either chemically
or physically cross-linked; generally, they can be easily
stretched and rapidly recover their original dimensions
when applied stresses are released
4

5.  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 (1950s), a group of synthetic rubbery
materials called elastomers Polysulphides and
Condensation Silicones) , which are capable of making
impressions of both soft and hard tissues are developed.
5

6.  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
6

7. 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.
7

8. 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
8

9. 9

10. Polysulphide
Silicon
rubbers
(condensati
on curing
type)
Silicon
rubbers
(addition
curing type)
polyether
10
Elastomeric impression materials are of four types
according to the chemical nature of the material:

11.  Consistency is measured by pressing 0.5 ml of mixed
material between two flat plates applying a force of
1.5N.
 Consistency is defined by average diameter of the
resulting disc of the material.
 Diameter viscosity
11

12. 12
Type Description Min Max
0 Very high
consistency
(putty like)
35
1 High
consistency
(heavy
bodied)
35
2 Medium
consistency
(medium
bodied)
31 41
3 Low
consistency
(light
bodied)
36
Consistency of test disc
diameter(mm)

13. Type Max permanent
deformation
Max flow in
compression
Max
dimensional
change
in 24 hrs
I 2.5 0.5 -0.5
II 2.5 0.5 -1
III 5.5 2 -0.5
13

14.  Workability
 Dimensional stability
 Accuracy
 Rheological properties
 Elasticity
 Tear strength
 Biocompatibility
 Shelf life
14

15. Impression
material
23ºC 37ºC 23ºC 37ºC
Polysulfide 6.0 4.3 16.0 12.5
Condensati
on silicon
3.3 2.5 11.0 8.9
Addition
silicon
3.1 1.8 8.9 5.9
Polyether 3.3 2.3 9.0 8.3
15
Mean working time (min) Mean setting time(min)

16. Material %decrease in
working time
when temp
increased
(mean)
%decrease in
setting time
when temp
increased
(mean)
Polysulfide 30 23
condensation
silicon
16 15.5
Addition silicon 38 31
Polyether 31 8.5
16

17.  temperature - working & setting time
 Curing of polyether is less sensitive to temperature
 modification of base/accelarator paste
 thinner - WT, slight ST
17
Viscosity
Humidity

18.  An impression material sustains some deformation as it
is removed from the mouth but it must rebound to its pre-
removal dimensions.
 An impression with a sufficiently high elastic limit should
not sustain permanent deformation.
 The elastic properties of these elastomeric impression
materials improve with an increase in curing time in the
mouth
 An extra time of 1 or 2 min before removal may be
beneficial.
18

19. 19
Addition
silicone
Condensa
tion
silicone
polyether
polysulphi
de
relative amount of permanent deformation in compression
following strain induced during removal increases in the following
order

20. Stiffness
20
polysulfide
Condensat
ion silicon
Addition
silicon
polyether

21.  Ideally-should flow freely and wet the tissue as it is being
injected to achieve adaptation - then resist flow away
from the intended surface areas.
 This will facilitate spreading of heavy-body material on
the impression tray and retain it in the tray. This
phenomenon is called shear thinning
 Polyether – rigid – problem preparation on periodontally
weak tooth - # of dies & tearing of impression material at
the sulcus
21

22.  Polymerization shrinkage
 Loss of byproduct
 Thermal contraction from oral temperature to room
temperature
 Imbibitions
 Incomplete recovery of deformation(visco elastic nature)
 Pour within 30 mins – polysulfide & condensation silicon
22

23.  The amount of force needed to tear a specified test
specimen divided by the thickness of the specimen is
called the tear strength.
 The ranking of tear strength from the lowest to highest of
the impression materials is as follows
23
silicones polyether polysulfide

24.  Probability of allergic reactions is low
 Polysulfide has the lowest cell death count
 Polyether has the highest cell death count ,toxicity and contact
dermatitis among the class.
 The most likely problem is lodgment of impression material in
gingival sulcus resulting in severe inflammation,
24

25. o Subgingival regions are very thin – material can tear
o Residual segment of impression material difficult to detect 
radio opacity of polysulfide can help
 Severe gingival inflammation.
o Examine the gingival sulcus immediately
after impression removal and also the
impression for any evidence of tearing
25

26. polysulfide 2 yrs
Condensation silicon stannous octoate oxidizes
Orthoethyl silicate is not stable in
presence of tin ester
Addition silicon 1-2 yrs
Poly ether > 2yrs
26
Cool, dry environment
Tubes always tightly sealed
Container closed

27. 27

28. 28
 First synthetic elastomeric impression material
 Also known as MERCAPTAN or THIOKOL
 Mode of supply
 Collapsible tubes
 One labeled Base paste and
 Other labeled Accelerator paste
Consistencies
 Light body(syringe or wash)
 Medium body (regular)
 Heavy body

29. Base paste •Polysulphide
prepolymer with terminal
and pendanthiol (-SH
groups)-80-85%
•Plasticizer – di-n-butyl
phthalate
•Inert filler- possible
chalk or titanium dioxide-
16-18%
Polymerized and cross
linked to form rubber
To control viscosity
To give ‘body’ control
viscosity and modify
physical properties
Catalyst paste •PbO2 / other alternative
oxidizing agent-60-68%
•Sulphur-0.5%
•Inert oil- paraffin type/
di-n-butyl phthalate
To react with thiol
groups- setting
Setting reaction
To form a paste with
PbO2 and sulphur
29

30. 30
Polysulfide
prepolymer
Lead
dioxide
polysulphide water

31.  working time – 4-7 mins
 Setting time – 7-10 mins
Colder climate- ST
A drop of water accelerates the reaction.
 Lowest viscosity
 excellent reproduction of details
 Dimensional stability -
Percent contraction (at 24hrs) – 0.40%-0.45%
Shrinkage is due to loss of polymerization byproduct
such as water
31

32.  Deformation on removal
caused by rocking the impression while removal;
it should be removed with a single swift pull
 High tear strength – 2500-7000 gm/cm2
 Biocompatibility – lowest cell death count
 Moderately hydrophilic
 Unpleasant odor and taste
 Can be electroplated with copper sulphate
32

33. ADVANTAGES DISADVANTAGES
Long working time
Good tear strength
Radiopaque
High flexibility
Lower cost
Good reproduction of surface
details
Requires custom tray
Obnoxious odor
Tendency to run down patient’s
throat
Stains clothing (pbO2) & messy to
work with
Must be poured within 1 hour
Hydrophobic so impression area
has to be dry
long setting time
33

34. 34

35. 35
 First type of silicone impression material
 Also known as conventional silicone’
 The setting occurs in room temperature so called as RTV
silicones (room temperature vulcanization)
 Mode of supply
 Collapsible tubes
 Base paste
 Accelerator paste / liquid
 Putty is supplied in jars
 low, medium, high, and very high (putty) consistencies

36. Composition Function
Paste •α- ω hydroxyl-
terminated
polydimethyl siloxane
(liquid silicon
prepolymer)
•Inert filler - silica
Undergoes cross
linking to form rubber
Gives ‘body’,
controls viscosity &
modifies physical
properties
Liquid •Alkyl silica – tetra
ethyl silicate
•Tin compound –
dibutyl tin dilaurate/ tin
octoate
Cross linking agent
Reaction catalyst
36

37. 37
Dimethyl
siloxane
Tetra ethyl
orthosilicate
Silicon
rubber
Ethyl
alcohol
Stannous octate

38.  Working time- 2.5 – 4 mins
 Setting time – 6-8 mins
 Tear strength – 2300-2600 N/m
 % contraction at 24 hrs- 0.38-0.60% Polymerization
and evaporation of the alcohol
 Hydrophobic
 Can be electroplated with silver and copper
 Stiffer and harder than polysulfide
38

39. ADVANTAGE DISADVANTAGES
Clean and pleasant
Good working time
Easily seen margins
High polymerization shrinkage
Volatile alcohol byproduct
Low tear strength
Hydrophobic
Pour immediately
39

40. 40

41.  Also known as polyvinyl siloxane or vinyl polysiloxane
 Mode of supply
 Collapsible tubes
 Base paste and
 Accelerator paste
 Putty is supplied in jars
 Consistencies
 Light body (syringe or wash)
 Medium body (regular)
 Heavy body
 Putty
41

42. Composition Function
Base paste •Poly(methyl hydrogen
siloxane)
• Other siloxane
prepolymers
• Fillers- colloidal silica
35-75%
Undergoes cross
linking
controls viscosity
Accelerator •Di vinyl polysiloxane
prepolymers
•Platinum salt
(chloroplatinic acid)
• Palladium
• Retarders
• Fillers
Cross linking agents
catalyst
Hydrogen absorber
42

43. 43
Polymethy
lhydrosilo
xane
Divinylpoly
siloxane
Chloropl
atinic
acid
Silicon
rubber

44.  Working time – 2-4 mins
 Setting time – 4-6.5 mins
 Tear strength – 1500-4300 N/m
 Percent contraction- 0.14-0.17%
 Pseudo plastic
 Exhibits lowest permanent distortion
44

45.  Sulphur contamination- inhibits setting
 Vinyl gloves also – sulphur containing stabilizer used
in the manufacturing process
 Even touching the tooth with the gloves before
seating impression – inhibits setting
• Inhibition of polymerization reaction- distortion
• Contact of internal surface of impression with gloved
hands :-
- Failure of the material adjacent to the tray to
polymerize
- Separation of the tray from the
impression material
45

46. 46
 Aluminum sulfate and ferric sulfate → gingival retraction
cord → retardation
 Residues from acrylics, methacrylates and petroleum
jelly lubricants may interfere with setting reaction of
material

47.  Danuta Nowakowska , et al conducted a study on
Polymerization time compatibility index of polyvinyl
siloxane impression materials with conventional and
experimental gingival margin displacement agents
 They concluded that all of the evaluated displacement
agents at laboratory and intraoral temperatures induced
changes in the polymerization time of PVS. Therefore,
chemical displacement agents should not come into
direct contact with PVS impression materials.
47
(J Prosthet Dent 2014;112:168-175)

48. ADVANTAGES DISADVANTAGES
 Highly accurate
 High dimensional stability
 Pleasant to use
 Short setting time
 Auto mix available
 If hydrophilic, good
compatibility with gypsum
 Hydrophobic
 Expensive
 Hydrogen gas evaluation in
some materials
 Hydrophilic formulations
imbibe moisture
 Sulfur contamination by latex
glove
48

49. 49

50.  First elastomer to be developed primarily to function as
an impression material
 Mode of supply
 Collapsible tubes
 Base paste
 Accelerator paste
 Third tube containing thinner may be supplied
 Consistencies
 Light bodied(syringe or wash)
 Medium bodied (regular)
 Heavy bodied
50

51. 51
Base paste
(large tube)
•Imine-terminated
prepolymer
•Inert filler- silica
•Plasticizer-
phthalate
Cross linked to
form rubber
To give body’
control viscosity
and physical
properties
To aid mixing
Catalyst paste
(small tube)
•Ester derivative
of aromatic
sulphonic acid
•Inert filler – silica
•Plasticizer-
phthalate
Initiate cross
linking
To form paste
composition

52. 52
polyether
Sulfonic
ester
Cross linked rubber

53.  Working time – 3 mins
 Setting time – 6 mins
 Tear strength – 1800- 4800 N/m
 Percent contraction – 0.19 – 0.24%
 least amount of distortion
 Pseudo plastic
 Biocompatibility – contact dermatitis
53

54. ADVANTAGES DISADVANTAGES
 Dimensional stability
 Accuracy
 Shorter setting time
 Automix available
 Set material very stiff
 Imbibition
 Short working time.
 Allergic hypersensitivity in
some cases.
54

55. 55

56. 56
Recent advances

57. • In early 1988, a visible light cured impression was
introduced(Genesis L.D. caulk).
• Two viscosities - Light and heavy bodied
• Composition :-
 Polyether urethane dimethacrylate
 Photoinitiators (camphoroquinone)
 Photoaccelerators (Diethyl amino
ethyl methacrylate)
 Silicone dioxide (Filler)
57

58.  Properties :-
 Long working time and short setting time
 Blue light is used for curing with transparent
impression trays
 Tear strength-6000-7500 gm/cm2 (Highest among
elastomers)
 Dimensional stability, flow, detail reproduction,
permanent deformation, wettability, compatibility with
cast and die materials and electroforming is similar
to addition silicone
58

59.  Manipulation :-
 Light body is syringed into the sulcus and over the
preparation
 Heavy body is loaded onto a clear tray and seated
over the light body
 Both are simultaneously cured with a visible light
curing unit having an 8mm or larger diameter probe
 Curing time is approximately 3 mins
59

60. ADVANTAGES DISADVANTAGES
 Controlled working time
 Excellent properties
 Ease of cold disinfection
without loss of quality.
 The impression material is
also compatible with gypsum
and silver or copper
metallizing baths
 Need special transparent
trays
 Difficult to cure in remote
area
60

61. • Surfactants are added to reduce the contact angle; dilute
solution of soap
• Most commonly used – non-ionic surfactants
Oligoether or polyether substructure
Hydrophilic part
silicon compatible hydrophobic part
61

62.  Diffusion – controlled transfer of surfactant molecules
from PVS to aqueous phase
Reduction in surface tension
Greater wettability
62

63.  used for making intraoral or extraoral occlusal bite
registrations for fixed or removable restoration and
implants.
 Fast intraoral set time of 20 secs – 1 min
 Doesnot slump or drip
 Supplied as cartridges to be used
With a caulking gun
 Commercial name;
Exabyte – Gc
Jet bite – Coltene whaledent
63

64.  This latest technique consists of a double barrel caulking
gun with mixing tip. The tip contains spirals on the inside.
Forcing of the base & accelerator results in its mixing.
 e.g. Volume mixer (Kerr), Pentamix(3M ESPE)
64
Advantages :-
More uniform mix
Less air bubbles
Reduced working time

65.  Hybrid polyether / polysiloxane material that has both
hydrophilicity and dimensional accuracy, before,during
and after set.
65

66.  Specialised addition silicone
 Used for checking errors in the internal surface of crowns
and fpd
 Available as two paste system
 Areas of premature contacts are revealed as bare areas,
which are marked and removed
 Commercial name
Fit Checker - GC
66

67. 1. Preparing a tray
2. Managing tissue
3. Preparing the material
4. Making an impression
5. Removing the impression
6. Preparing stone casts and dies
67

68. 68

69. 1.Paint on adhesives
Eg Coltene, Kerr Universal VPS.
2. Spray adhesives
Eg Sili spray
69

70.  Polysulfide
 Butyl rubber
 Styrene / acrylonitrile
Dissolved in volatile solvent such as
chloroform or ketone
 Silicones
 Polydimethyl siloxane / similar reactant like silicon & ethyl
silicate
 Hydrated silica forms of ethyl silicate – bonds with the
tray
 Chemical bond between tray material and Polydimethyl
siloxane.
70

71.  A. Peregrina et al, conducted a study on the effect of
different adhesives on vinyl polysiloxane bond strength to
two tray materials .
 Conclusion : The use of GC paint-on universal adhesive
provided significantly higher adhesive values than those
obtained with the adhesives supplied by the
manufacturers of the impression materials tested, with
the exception of the Kerr impression and adhesive
material combination where no significant differences
were found
71
(J Prosthet Dent 2005;94:209-13.)

72.  Gingival retraction cord
 double-cord technique is used when the margin is very
close to the gingival attachment.
 Retraction cords - impregnated with a hemostatic agent
(epinephrine)
 An electrosurgical unit
 Or a soft tissue laser
72

73.  Hand mixing
 Static mixing
 Dynamic mechanical mixing
73

74. 74

75. 75

76. 76

77.  Multiple mix technique
 Mono phase technique
 Putty wash technique
77

78. 78

79. 79
Only one mix is made- Part of it is placed in the tray
Another portion is placed in syringe for injection
Medium viscosity of addition and polyether can be used.

80. 80

81.  Giuseppe Varvara et al, conducted an invitro study on
Evaluation of defects in surface detail for monophase, 2-
phase, and 3-phase impression techniques
 They concluded that the 3-phase, 2-step impression
injection technique provides improved defect-free
reproduction of detail, showing fewer defects than other
impression techniques.
(J Prosthet Dent 2015;113:108-113)
81

82.  All elastomeric impression materials are viscoelastic, and
it is necessary to use a quick snap to minimize plastic
deformation
82

83.  Debubblizers, a dilute solution of soap - wettability of
the silicone impression material for the stone slurry
 Excellent dimensional stability of addition silicone and
polyether impression - construct two or three casts or
dies
83

84. • Immersion
• Gluteraldehyde , chlorine compounds,
iodophors, phenolics
• Disinfectants requiring more than 30
mins are not recommended
Polysulphide
Silicones
• Immersion with caution
• Chlorine compounds , iodophors
• Short term exposure – avoid distortion
Polyether
84

85.  Young S. Kang , et al conducted a study on Effects
of chlorine-based and quaternary ammonium-based
disinfectants on the wettability of a polyvinyl siloxane
impression material
 They concluded that
1. A QAB disinfectant product is more effective at
removing surfactant than a CLB disinfectant product.
Therefore, a CLB disinfectant provides more time
and control.
2. A wetting agent can reverse the hydrophobicity of
a disinfected PVS impression material if the duration
of cold disinfection is less than 6 hours.
85
(J Prosthet Dent 2017;117:266-270)

86. 86
Property Polysulphide
s
Condensation
silicones
Addition
silicones
Polyethers
Viscosity 3
viscosities (no
putty)
4
viscosities
including
putty
4 viscosities
including putty
single
viscosity(regul
ar) + diluent +
putty
Tear
resistance
Adequate Adequate Adequate Adequate
Elasticity Visco elastic
material
Very good Very good Adequate
Accuracy Good with
special trays
Acceptable
with stock
trays
Good with
stock trays
Good with
special trays
Dimensional
stability
Adequate Poured as
quickly as
possible
Very good Very good in
low humidity
Comparison of properties of elastomers

87. 1. Rough / uneven surface
 Premature removal
 Improper mixing ratio
 Too rapid polymerisation
 Excessive high accelerator / base
ratio – condensation silicon
87

88. 2. Bubbles
 Too rapid polymerisation preventing
flow
 Air incorporation
88

89. 3.Irregularly shaped voids
 Moisture / debris
89

90. 4.Rough / chalky stone cast
 Inadequate cleaning
 Excess water left on surface
 Excess wetting agent
 Premature removal
 Improper manipulation
 Failure to delay pour
90

91. 5.Distortion
 Resin tray not aged sufficiently
 Lack of adhesion
 Lack of mechanical retention
 Premature development of elastic
properties
 Excessive bulk
 Insufficient relief
 Continued pressure
 Movement of tray
 Premature/improper removal from mouth
 Delayed pouring
91

92. 6. Faulty electroplating
 Dimensional change in the elastomer – continued
polymerisation during electroplating
 Electrodeposited metal tend to contract during deposition
 Flat surface tend to become curved and sharp angles
rounded
 Improper adherence of the electroformed metal to
impression material – greater distortion
92

93.  Philips science of dental materials 12th edition
 Craig’s restorative dental materials 13th edition
 Mc Cabe and walls’ applied dental materials 9th edition
 William J O'Brien Dental materials selection 3rd edition
 Effects of chlorine-based and quaternary ammonium-
based disinfectants on the wettability of a polyvinyl
siloxane impression material (J Prosthet Dent
2017;117:266-270)
 Evaluation of defects in surface detail for monophase, 2-
phase, and 3-phase impression techniques (J Prosthet
Dent 2015;113:108-113)
 The dimensional stability of a vinyl polyether silicone
impression material over a prolonged storage period (J
Prosthet Dent 2013;109:172-178)
93

94.  Elastomers since their introduction have revolutionised the art of
impression making hence allowing the operator to provide
acuurate fitting restorations
 Addition silicones and polyethers account for major portion of
the current practice.
 Condensation silicones, Polysulfides – more sensitive with
respect to handling considerations , mix-and-pour techniques,
which may affect accuracy.
94

95.  The understanding of basic knowledge of the impression
materials and their behavior during handling are
important for their use in the oral environment and clinical
success.
 The selection of the material best suited for a particular
clinical situation and technique rests with the operator.
95

96. 96