This document provides an overview of dental impression materials, including their definition, classification, history, mixing systems, properties, and techniques. It discusses the main types of materials - polysulfide, condensation silicone, addition silicone, and polyether. For each, it outlines their composition, advantages, disadvantages, and properties like tear strength and dimensional stability. The document also reviews factors that affect impressions like temperature, viscosity, and storage conditions. It provides recommendations to control dimensional changes and concludes with a literature review on improving the accuracy of elastomeric impression materials.

1. 1

2. Dr.Akshata Kage.

3.  Definition
 Classification
 History
 Mixing System
 Impression materials
 Properties
 Material incompatibilities
 Recent advances
 Impression techniques
 Removal of impression & preparation of
stone dies
 Review of Literature
 Conclusion
 References

4. A group of flexible chemical polymers, which are either
chemically or physically cross-linked. Generally they can
be easily stretched and rapidly recover their original
dimensions when applied stresses are released.
GPT

5. 1. ADA Specification no.19
Based on selected elastic properties & dimensional
changes after setting.

6. 2. According to consistency
ISO Standard for Dental Elastomeric Impression Materials (ISO
4823)
TYPE DESCRIPTION
0
1
2
3
Very high consistency
( Putty like)
High consistency
(Heavy bodied)
Medium consistency
(Regular body)
Low consistency
(Light body)

7. 3. According to their chemical composition

8. 1950 1955 1965 1975 1988
Polysulfi- Condensation Polyether Addition Light cured
des silicone silicone elastomers
HISTORY

9. 1. Hand Mixing 2. Static mixing 3. Mechanical mixing

10. Light/Medium body
 Equal lengths of base paste and catalyst paste on mixing pad
or glass slab
 Catalyst paste collected first with stainless steel spatula and
then spread over the base paste

11.  Mixed until a uniform mix is obtained

12. Putty systems
 Scoops supplied by the manufacturer.
 Kneaded with the fingers until uniform color.

13. If one of the components is in liquid form, such as the catalyst for
condensation silicones, a length of the base is dispensed from the
tube onto a graduated mixing pad and drops of the liquid catalyst
corresponding to the length of the base are added.

14.  This technique transforms two paste materials into a
homogeneous mixture without mechanical mixing.
 Gun used for compressing materials in a two-cylinder
cartridge, which contains the base and catalyst .

15. The mixer elements are a series of alternating right- and left-turn
180° helixes . The streams that flow in either side of the helix
will make a 180°.The rotational circulation causes a radial
mixing of the materials.

16. The mixed impression material is injected directly into the
adhesive-coated tray and onto the prepared teeth.
Advantages
 Greater uniformity in proportioning and mixing.
 Fewer voids in the mix.
 Reduces the mixing time.
 Fewer possibilities for contamination of the material.

17.  Catalyst and base are supplied in large plastic bags in a
cartridge which is inserted into the top of the mixing
machine.
 Plastic tip is placed in front of the machine.
 When button is depressed, parallel
plungers pushed against the collapsible
plastic bags thereby opening the bags
and forcing material.
 Uses a motor to drive parallel plungers.

19. Also known as Thiokol rubber or Mercaptan or rubber
base.
Available as
 Light body
 Medium body
 Heavy body

20. BASE PASTE
1. Polysulfide polymer- 80-85%
 Terminal and pendent thiol (-SH group)
 Polymerize and crosslink to form rubber
2. Filler- 12-50%
 Lithopone or Titanium dioxide, chalk, zinc sulfide, zinc
oxide, silica.
 Gives body and controls viscosity

21. 3.Plasticizer
 Dibutyl pthalate, chlorinated paraffin
 To control the viscosity
4. Accelerator- Sulfur-0.5%

22. CATALYST PASTE
1. Lead dioxide- 30%
 Catalyses the condensation reaction.
 Gives the characteristic brown colour.
 Other oxidizing agents, which can be used are Mn or Zn
dioxides, hydro peroxides, cupric hydroxide.

23. 2. Inert Oil- 17%
 Paraffinic type.
 Form a paste with lead dioxide and sulphur.
3. Sulphur- 1-4%
 Involved in the setting reaction
4. Oleic acid or stearic acid
 Retarder

25. ADVANTAGES
• High tear strength
• High flexibility for easy
removal around
undercuts
• Long working time
• Economic
• Extensive shelf life
• Has good flow before
setting
DISADVANTAGES
• Dimensionally unstable
• Unacceptable odour
• Stains clothing
• Long setting time
• Least elastic recovery
• Must be poured
immediately
• Potential for significant
distortion

27. Available in
 Low viscosity
 Medium viscosity
 Very high ( Putty) viscosity

28. BASE PASTE
1. Hydroxyl-terminated polydimethyl siloxane
 Liquid silicone
 Undergoes cross-linking to form rubber.
2. Inert filler
 Silica, copper carbonate
 Controls the viscosity and modifies the physical properties.
 Paste contains 30-40 % where as putty will contain 75% of the
filler.

29. CATALYST PASTE
1.Alkyl silicate
 Tri or tetraethyl ortho silicate
 Cross linking agent
2.Tin compound
 stannous octoate
 Catalyst

30. Polydimethyl + orthoethyl stannous Silicone + ethyl
Siloxane silicate octoate rubber alcohol

31. ADVANTAGES
• Pleasant color and odor
• Excellent reproduction
of surface details
DISADVANTAGES
• High polymerisation
shrinkage
• Less dimensional stable
• Volatile alcohol byproduct
• Stiffer and harder
• Low tear strength
• Hydrophobic

33. Available as
 Light
 Medium
 Heavy
 Putty

34. BASE PASTE
1.Polymethyl hydrogen siloxane or other siloxane
prepolymers
 Undergo polymerization to form rubber
2. Inert filler
 Silica, metal oxides etc.
 Give body, control the viscosity and modify the physical
properties of the material

35. CATALYST PASTE
1. Di vinyl polydimethyl siloxane or other siloxane
prepolymers.
2. Platinum salt/chloroplatinic acid.
 Reaction catalyst.
3. Palladium – hydrogen absorber
4. Inert fillers
 Silica, metal oxides etc

37. ADVANTAGES
• Excellent dimensional
stability
• Low curing shrinkage
• Low permanent
deformation
• Pleasant color and odor
• Good tear strength
DISADVANTAGES
• Expensive
• Hydrophobic
• Sulfur contamination by
latex gloves

39. Available as
 Light
 Medium
 High viscosity

40. BASE PASTE
1. Polyether polymer
 Imine terminated prepolymer.
 Cross-link to form rubber.
2. Inert Filler
 Colloidal silica
3.Plasticizer
 Glycolether, phthalate
4. Coloring agents

41. CATALYST PASTE
1. Aromatic sulfonate ester
 It initiatiator
2. Inert filler
 Colloidal silica
3.Plasticizer
 Phthalate or glycol ether
4. Coloring agents

43. -
ADVANTAGES
• Adequate tear strength.
• Less hydrophobic- better
wetting.
• Less distortion on
removal.
• Good dimensional
stability.
• Good reproduction of
detail and easily poured
in stone
DISADVANTAGES
• Imbibition
• Hypersensitivity in some
patients.
• Extremely stiff
• Stiffness requires blocking
undercuts.
• Slightly more expensive.

44. Materials Method Recommended
disinfectant
Polysulfi
de
Immersion no more than
30 min exposure time
Glutaraldehyde
Chlorine
compounds
Iodophors
Phenolics
Silicone
Polyether Immersion with caution,
for 10 min
Chlorine
compounds or
iodophors 44

45.  Disinfectant should be sprayed on impression until
saturated.
 Then wrapped in a disinfectant soaked paper towel and
placed in a sealed plastic bag for 10 min.
 After removal of paper towel impression should be rinsed,
dried and poured immediately with cast material.
45

47. Wettability

49.  A review of modern impression materials. Aust Dent J
23:178, 1978.

50. Effects of temperature
 Increase in temperature - decreases both working and
setting time by accelerating the curing rate.
 Decrease in temperature – increases working time, can be
accomplished by refrigerating the materials or mixing on a
chilled dry glass slab.
Effect of viscosity
 Increase in viscosity - decreases working time and setting
time.
Altering base / catalyst ratio can alter the working and setting
time - but adversely affects the mechanical properties.

51. Addition
silicone
-0.17%
Polyether
-0.24%
Polysulfide
-0.40%
Condensation
silicone
-0.60%

52. Five major CAUSES of dimensional changes.
 Polymerization shrinkage.
 Loss of by product (water or alcohol) during condensation
reaction.
 Thermal contraction from oral temperature to room
temperature.
 Imbibition when exposed to water, disinfectant or high
humidity environment over a period of time.
 Incomplete recovery of deformation because of
viscoelastic behaviour.

53. Polysulfide
0.17%
Condensation
silicone
0.25%
Addition
silicone
0.40%
Polyether
0.60%

54. Polyether
3%
Addition
silicone
4%
Condensation
silicone
5%
Polysulfide
7%

55.  Tear strength measure the resistance to fracture of an
elastomeric material subjected to a tensile force acting
perpendicular to a surface.
 Depends on chemical composition, consistency and
manner of removal of material from mouth.

56. Polyether
1800-4800 N/m
Polysulfide
2500-7000 N/m
Addition silicone
1500-4300 N/m
Condensation
Silicone
2300-2800 N/m

57.  Ability of a material to return to its original dimension
without significant distortion upon removal from the
mouth.
 For all impression material greater the depth of undercut,
the greater its permanent distortion.

58. Polysulfide
97.9%
Polyether
98.5%
Condensation
silicone
99.5%
Addition
Silicone
99.8%

59.  Cell cytotoxicity - Polysulfide results in lowest cell death
count and set polyether highest.
 Hyper sensitivity to polyethers has been reported due to
the presence of alkylbenzene suplhonate in the catalyst.

61.  Metal salts in many astringents & retraction cords
(adrenaline & ferric sulfate) inhibit setting of PVS &
polyether
61

62.  Polymerization of PVS can be inhibited by
direct contact with latex gloves or
indirectly by hands that had previously
been wearing gloves.
62

64.  Enhanced with the incorporation of nonionic surfactants.
 Contains a hydrophilic part and a silicone-compatible
hydrophobic part.
 These surfactants act through a diffusion transfer of
surfactant molecules from the polyvinyl siloxane into the
aqueous phase.
 The surface tension of the liquid is changed, and
wettability increases.

65.  Hybrid polymer of polyether and siloxane
(addition silicone) group
 With Polyether group, a hydrophilic material is
produced
 With siloxane , a dimensionally stable material is
produced
 Good wetting property
 Low tear strength

66.  It is a polyether urethane dimethacrylate photoinitiated
elastomeric impression material
 Long working time, short setting time, dimensional
stability, accuracy, high tear strength
 Good wettability
 Two viscosities: Light and heavy

67. Can be steam autoclaved at 134°C
without adverse effects to the
dimensional stability & tear strength.
To be used with autoclavable
impression trays
and a special tray adhesive.

69.  Medium viscosity polyether and addition silicones used in
a custom tray.
 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

70. Advantages
 Reduced wastage of the material.
 Less time consumption.
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.

72. Advantages
 Over comes the polymerization shrinkage of the light
body material
 Margins duplicated in light body.
Disadvantages
 An assistant required for mixing the material - tray/syringe
simultaneously.
 Margins duplicated in putty in case of excess pressure.

73. TWO STAGE PUTTY-WASH TECHNIQUE

74.  Developed for condensation silicone to minimize effect of
polymerization shrinkage.
 Care to be taken to provide enough vents for wash
material to escape through the putty material.

75. 2 mm thick wax is adapted on a diagnostic cast, occlusal
stops are provided on non-functional cusps.
A putty impression is made with a stock tray resulting in a
putty custom tray with 2mm space for the wash material
Putty custom tray is then washed with light body material.

77. Advantages
 Wash stage carried out after the putty has set and
contracted.
 Controlled wash bulk compensates for this contraction
with minimal dimensional change.
Disadvantages
 Extra chair side time.
 Extra material.

78.  Used as means for carrying impression and also
for gingival retraction.
 Copper band is selected and placed over the tooth
and the buccal surface and the gingival contours
are marked.

80. Impression material is loaded into into the copper band
and seated on the tooth and impression is made with
the tray material.

81. Advantages
 The gingival tissue retraction is maximal and superior to
indirect retraction methods.
 The band impression made under pressure will have no air
bubbles or voids
Disadvantages
 Can cause damage to the attachment apparatus
 Time consuming

82.  First break the physical adhesion between the tissue
and the impression.
 All elastomeric impression materials are viscoelastic,
and it is necessary to use a quick snap to minimize
plastic deformation of the impression during the removal
process.
 Teasing or rocking movement should not be used.

83.  The hydrophobic characteristics of silicone impression
materials make them suitable for pouring of epoxy resin
to produce dies but makes pouring with gypsum
products challenging.
 Surfactant sprays, improve the surface wettability of the
silicone impression material for the stone slurry.

84.  Pouring of a stone cast in a polyether does not require
surfactant.
 The excellent dimensional stability of addition silicone
impression materials makes it possible to construct two or
three casts or dies from these materials.

86. F.S. Goncalves, D.A.V. Popoff, C.D.L Castro, G.C. Silva, and A.N. Moreira
review the literature concerning the dimensional stability of dental
elastomeric impression materials and to propose clinical
recommendations for the control of variables that influence the
accuracy of these materials.
Conclusion
This review supports the following recommendations to control the
dimensional stability of elastomeric impression materials

87.  Impressions should be stored in an environment with temperatures
of 21 ± 2º C
 There was no consensus regarding the optimal storage medium for
elastomers, except for the polyether, which should be stored in an
environment with a relative humidity of less than 50%.
 Polysulfide and condensation silicone impressions should be poured
up to 30 minutes.
 Polyether impressions can be poured between 30 minutes and 24
hours.
 PVS impressions can be poured between 30 minutes and 4 weeks.
Eur. J. Prosthodont. Rest. Dent(2017):Vol.19;1-4

88. Pratheek Shetty, Shobha Rodrigues
The accuracy of elastomeric impression materials on
repeated pours is reviewed in this article.
conclusion
 addition silicones and polyethers to a certain extent were
least affected with delay in pouring the impression.

89. since condensation silicones and polysulphide materials are
not dimensionally stable, the time interval between pours
should not be greater than 30 min and repouring would result
in significant loss of accuracy.
The Journal of Indian Prosthodontic Society | June 2006 | Vol 6 | Issue 2

90. Accuracy of three polyvinyl siloxane putty-wash impression
techniques.
Nissan J, Laufer BZ, Brosh T, Assif D.
This study assessed the accuracy of 3 putty-wash impression techniques
using the same impression material (polyvinyl siloxane) in a laboratory
mode
The 3 putty-wash impression techniques used were
(1) 1-step impression technique
(2) 2-step with 2-mm relief
(3) 2-step technique with a polyethylene

91. Rina singh, Jagit singh, Sonia Nanda
To determine the effect of different retraction cord aluminium
chloride (5%), ferric sulphate (13.3%) and epinephrine (0.1%)
medicaments on surface detail reproduction of polyvinyl
siloxane impression materials(Dentsply and 3M ESPE)
J Clin Exp Dent. 2013 Jul; 5(3): e138–e143.
Surface detail reproduction of the polyvinyl siloxane impression
materials is adversely affected by the retraction cord medicaments.

92. Impressions are very critical to the success of dental
restorations. An understanding of their chemical nature,
physical property and limitation of each material is
necessary for their successful use in clinical dentistry.

93.  CRAIG’S restorative dental materials, 12th edition
 PHILLIP’S science of dental materials, 11th edition
 Markus Balkenhol, Paul Ferger, Bernd Wostmann -In vitro
study dimensional accuracy of 2- stage putty wash
impression : influence of impression tray & viscosity.
ijp,2007, 20, 573-575
 Markus Balkenhol, Sylvia Haunschild, Christina Erbemm and
Bernd WöstmannIn vitro study dimensional accuracy of 2-
stage putty wash impression : influence of impression tray &
viscosity J Prosthet Dent 2010;103:288-294

94.  Heeje Lee, Joseph , J.L. Hochstedler and Carlo Ercoli-
purpose to examine the clinical factors affecting implant
impression accuracy J Prosthet Dent 2008;100:285-291
 Thomas Stober, Glen H. Johnson and Marc Schmitter - Study
to assess the accuracy of disinfected vinyl siloxne ether
impressions & compare the accuracy to vinyl polysiloxane &
polyether impression system J Prosthet Dent 2010;103:228
239