elastic impression materials

1. ne may not get a chance to make a good first
impression. But remember that the first impressio
is not the last chance to make a good impression
o
GOOD
MORNiNG

2. ELASTIC Impression
MATERIALS
ABHISHEK KAVLEKAR

5. elastic : susceptible to being stretched, compressed, or distorted and then
tending to resume the original shape
elastomeric impression material: 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.

6. Impression
materials
Rigid
Impression
plaster
Zinc Oxide
Eugenol
Impression
compound
Impression
waxes
Elastic
Hydrocolloid
Elastomers
Reversible
hydrocolloid
Irreversible
hydrocolloid
Polysulfid
es
Silicones
Polyether
s

7. 7
↓ ↓ ↓ ↓
I 1920 I 1930 I 1 940 I 1950 I 1960 I 1970 I 1980 I1990 I
2000
↑ ↑

8. A solid, liquid or gaseous substance made up of
large molecules or masses of smaller molecules
that remain in suspension in a surrounding
continous medium of diffrent matter*
A colloid that contains water as the dispersion
phase is called as
*Anusavice KJ: Philips’ Science of Dental Materials.
11th Edition

9. Organic hydrophillic colloid extracted from
SEAWEED. It chiefly contains agarose and
agaropectin.
Introduced by Alphous Poller of Vienna” in
1925.
Chemically it is a sulfuric ester of galactan
complex.

10. The agar used in dentistry is supplied in the following
forms-
1) Tray material
2) Syringe material
3) Agar for duplication

11. Component Function Composition(
%)
Agar Brush Heap structure 13 – 17
Borate Strength 0.2 – 0.5
Potassium Sulfate Gypsum hardener 1.0 – 2.0
Diatomeceous earth, Wax,
Silica, clay etc
Filler 0.5 – 1.0
Thixotropic materials Thickener 0.3 – 0.5
Water Reaction medium Balance 84%
Alkylbenzoates Perservative 0.1
Thymol Bactericidal trace

13. Gel
Liquefaction
temperature
Sol
Gelation
temperature
Gel

14. LIQUEFACTION
• 100°C
• Minimum of
10 minutes.
• Propylene
glycol
STORAGE
• 65°C
• Several days
TEMPERING
• ~45°C
• 3 to 10 min
• Never for
syringe
material

15. •Just before completion of tempering of tray material
the syringe material is taken from the storage
compartment and applied to the base of preparation
•Water soaked outer layer of the tray hydrocolloid is
removed
• Tray is seated with light pressure & held with light
force
•Gelation is accelerated by circulating cool water
(approximately 18 to 21 C) through the tray for 3 to
5 minutes.

17. Area to be recorded is flooded with warm
water
Syringe agar material – is quickly & liberally
syringed over prepared tooth
Tray agar placed over the syringed agar

18. • Greater than 96.5% (permanent deformation less than 3.5%)
after the material is compressed 20% for 1 second
• Tray types have elastic recovery of about 99%
Elastic Recovery
• The ANSI/ADA Specification 11 requirement for flexibility allows
a range of 4 to 15%
Flexibility

19. • Compressive strength is 0.8 MPa
• Tear strength is 0.8 to 0.9 N/mm.
• The ANSI/ADA Specification requirement: 0.75 N/mm
Strength

20. • If the material is held rigidly in the tray, the impression material
shrinks toward the center of its mass
• Rapid cooling may cause a concentration of stresses near the
tray where the gelation first takes place
Distortion during Gelation
• It must be sufficiently viscous so that it will not flow out of the
tray
• It must not be so great that it will not readily penetrate every
detail of the teeth and the soft tissues
Viscosity of the Sol

21. ADVANTAGES
Good elastic properties.
Good recovery from distortion.
Accurate dies can be prepared.
Palatable and well tolerated by the
patient.
Can be used for duplicating models.
As it is not hydrophobic, it gives a
good model surface.
DISADVANTAGES
Extensive and expensive
equipment.
Dimensional instability.
Pain and thermal shock.
Cannot be electroplated.
Tears easily.
Disinfection.
21

22. USES
1. Impressions for fixed prosthesis.
2. Duplicating material.
3. Tissue conditioning material.

23. •Developed as a substitute for agar during World War
II
•E.C.C. Stanford, a Scottish chemist, discovered
alginates from from brown seaweed (algae) also called
algin in the 1880s
40 yrs later, “S. William Wilding” received the patent
for alginate as impression material.
It is a linear polymer of anhydro - -D mannuronic acid”
of high molecular weight.

24. Component Function Wt%
Potassium alginate Soluble alginate 15
Calcium sulfate
dihydrate
Reactor 16
Zinc oxide Filler particles 4
Potassium Titanium
fluoride
Accelerator 3
Diatomaceous earth Filler Particles 60
Sodium phosphate Retarder 2

25. K2nAlg + nCaSO4 nK2SO4 + CanAlg
2Na3PO4 + 3CaSO4 Ca3(PO4)2 + 3Na2SO4
25

26. 26
*Lemon JC et al ( J Prosthet Dent: 2003 Sep;90(3):276-81.
Never change the water powder ratio

28. Frey G, Lu H, Powers J (J
Prost: 2005 Dec;14(4):221-5)
Concluded that mechanical
mixer improved elastic
recovery and compressive
strength of the alginate
impression materials and had
no effect on strain in
compression and tear energy.
A mechanical mixer facilitates
the mixing of alginate
impression materials and
improves some mechanical
properties.
Mechanical mixer

29. Select a perforated tray
Mixing and loading
Making the impression
Wait for
3mins
Remove impression rapidly
in a single jerk
Cut off the excess

30. Morris et al ( J Prosthet Dent 1983,49: 328-
330)
• Demonstrated that smoothing the surface of the
mixed alginate with a wet finger, prior to making
the impression, consistently resulted in fewer
bubbles on the surface of casts.

31. Mixing time
Setting time
Working time
1. Fast set: 45 sec.
2. Regular set: 60 sec.
1. Fast set: 1.25 to 2 min.
2. Regular set: 3 to 4.5 min.
1. Fast set: 1.5 to 3 min.
2. Regular set: 3 to 4.5 min.
31

32. Elastic
recovery
 Greater than 95% when the material is
compressed 20% for 5 seconds.
Flexibility  Range of 10 to 20% at a stress of
1000g/cm2
Strength
 Compressive strength–at least
0.35MPA
 Tear strength – 0.37 to 0.69 MPa
32

33. Factors affecting strength
Too much or too little
water used for mixing
Insufficient spatulation
Over mixing
Failure of ingredients to
dissolve sufficiently
Breaks up the calcium
alginate gel network
Results in weakened final
gel, making it less elastic

34. Accuracy
1. Increase in concentration of alginate to
make the material more accurate
2. Roughness of the impression surface is
sufficient to cause distortion
3. Sufficiently accurate to be used for making
impressions for removable partial denture
prosthesis
1. Model should be poured as soon as possible
2. Stored in 100% relative humidity in a plastic
bag or wrapped in a damp paper towel
3. Greater chance of distortion the longer the
impression is stored
Dimensional
stability
34

35. Easy to mix and manipulate
Minimum requirement of
equipment
Accuracy (if properly handled)
Low cost
Comfortable to the patient
Hygienic (as fresh material is
used for each impression)
35

36. Not accurate for crown
and bridge impressions
Cannot be electroplated
Distortion occurs easily
Poor dimensional stability
Poor tear strength
36

37. 1. Complete and removable
denture prosthesis
2. Study models and working casts
3. Duplicating models
37

38. Chilled alginate
Syringe agar
Gels by chemical reaction
Gels by means of contact with the cool
alginate
38

39. 39
ADA specification 20 -
Type I (thermo reversible)
Type II (nonreversible)
Hydrocolloids are popular and
have the same composition as
the impression materials, but
their water content is
higher, consequently agar
or alginate content is
lower

40. 1. In the form of a sol, containing the water. A reactor of
plaster of Paris is supplied separately.
2. Two paste system, one containing the alginate
sol, and second containing the calcium reactor. These
materials are said to contain silicone and have superior
tear resistance.
3. Lee YK et al in this study concluded that addition of
NaF in an alginate impression material may result in
effective release of fluoride without deteriorating the
properties of material itself*
40

41.  These alginates change color during
manipulation to give a clear indication of mixing
time, loading into mouth & setting of the material
 They contain acid/base indicators that are
responsible for change in color at different
critical points due to changes in pH that occur
during setting
 Three phases of chromatic alginates are –
RED PHASE: MIXING TIME
ORANGE PHASE: WORKING TIME
YELLOW PHASE: TIME IN THE MOUTH
41
Chromatic

42. Impression is rinsed
Disinfectant sprayed liberally
Wrapped in disinfectant soaked
paper towel
Placed in a sealed plastic bag for
10 minutes
Wrapped impression is
removed, rinsed and poured
Household bleach
Iodophor
Synthetic phenols
42

43. •Shorter storage time of hydrocolloid impressions
before pouring is desirable.
•Agar Impressions can be stored up to 1 hour in
100% humidity or in storage media like 2%
potassium sulfate*
•If irreversible hydrocolloid impression pouring is to
be delayed up to three hrs, then it should be
wrapped with a wet towel and poured within 3 hrs, as
this did not appear to affect their accuracy
significantly.**
*J Prosthet Dent 2001:86(3); 244-50.
**Saudi Dental Journal 2002,:14(3).

44. C o m m o n f a i l u r e s
a n d
c a u s e s .

45. Agar
Inadequate
boiling
Storage
temperature
too low
Storage time
too long
Alginate
Improper
mixing
Prolonged
mixing
Excessive
gelation
Water
powder ratio
too low
Grainy material
Agar
Water-
soaked tray
surface
material not
removed
Premature
gelation of
either
Alginate
Not
applicable
Separation of tray and syringe
materials
45

46. Tearing
Agar
Inadequate bulk
Premature removal
from mouth
Syringe material
partially gelled when
tray was seated
Alginate
Inadequate bulk
Moisture
contamination
Premature removal
from mouth
Prolonged mixing
46

47. Agar
Inadequate cleansing
Excess water
Improper manipulation of
stone
Air drying the impression
before pouring
Alginate
Inadequate cleansing
Excess water left on the
impression
Premature removal
Model left in impression too
long
Improper manipulation of
stone
47
Rough or chalky
stone model

48. Agar
Impression not poured
immediately
Movement of tray during
gelation
Premature removal from
mouth
Improper removal from
mouth
Use of ice water during
initial stages of gelation
Alginate
Impression not poured
immediately
Movement of tray during
gelation
Premature removal from
mouth
Improper removal from
mouth
Separation of alginate
from the tray 48
Distortion

49. Agar
Gelation of
syringe
material-
preventing flow
Alginate
Undue gelation
preventing flow
Air incorporated
during mixing
Agar
Material too
cold
Alginate
Moisture or
debris on
tissue
49
Irregularly shaped
voids
External bubbles

50. 50
Chemically, there are
3 kinds of elastomers
1)Polysulfides
2)Silicone
a. Addition
b. condensation
3) Polyethers

51. Current ADA specification 19 recognizes 3 types of elastomeric materials
This classification is based on selected elastic properties & dimensional change
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 -1.0
III 5.5 2.0 -0.5
51
Type Decription
consistency
Consistency test disc
Diameter(mm)
min max
0 Very high(putty) - 35
1 High(heavy bodied) - 35
2 Medium(medium bodied) 31 41
3 Low(light bodied) 36 -
According to ISO 4823 the method of classification according to
consistency is as following-

52. 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
1950

53. Polysulfide polymer - 80 to 85%
Fillers - 16 to 18%
Titanium dioxide, lithopone, zinc sulfate,
copper carbonate or silica
Dibutyl phthalate-plasticizer
Sulfur (0.5%) – accelerator
Lead dioxide; 60 to 68%
Oleic/stearic acid
Retarder
Deodorants
BASE
PASTE
REACTOR
PASTE

54. Chain lengthening by oxidation of
terminal –SH groups
Cross linking by oxidation of pendant
–SH groups
Polysulfide
polymer
Lead
dioxide
Polysulfide
water
∆ 3 to 4 C
54

55. Long working time
Good tear strength
Radiopaque
Good reproduction of surface detail
High flexibility
Lower cost
Need to use custom made trays
Bad odor
Tendency to run down patient’s
throat
Stains clothing & messy to work
with
Must be poured within 1 hour
Hydrophobic so impression area
has to be dry
DISADVANTAGES
55

56. Mode of supply
 Collapsible tubes
Base paste and
Accelerator paste / liquid
 Putty is supplied in jars
Consistencies
 Light body (syringe or wash)
 Putty
Also known as conventional silicones
19
55

57. Polydimethyl siloxane
Fillers; 16 to 18%
Calcium carbonate or silica
Tetra-ethyl
Orthosilicate- reactor
Stannous octoate - catalyst
BASE
PASTE
REACTOR
PASTE

58. Tetra-ethyl
orthosilicate
Dimethyl
siloxane
Silicone
rubber
Ethyl
alcohol
Stannous
octate
∆ 1°C
Cross linkage between Orthoethyl silicate and the terminal hydroxyl group of Dimethylsiloxane
to form a 3 Dimensional network 58

59. Clean, pleasant materials
Highly elastic
Putty-wash system
improves accuracy
Inaccuracy due to
shrinkage
Must be poured within 1
hour
Hydrophobic so impression
area has to be dry
59

60. 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
Also known as polyvinyl siloxane or vinyl polysiloxane
1975
60

61. • Base paste
Poly methyl hydrogen siloxane
Other siloxane prepolymers
Fillers- Divinyl poly siloxane
• Reactor paste
Platinum salt: Catalyst
(chloroplatinic acid)
Palladium: Scavenger

62. Vinyl
siloxane
Silane
(hydride
groups)
Silicon
e
rubber
Platinum salt
The base polymer is terminated with vinyl groups and is cross linked with hydride
groups 62

63. Highly accurate
High dimensional stability
Recovery from deformation on
removal is excellent
May be used with stock or
custom trays
Can be poured after 1 week
Multiple pours are possible
Expensive – twice the cost of
Polysulfides
More rigid than condensation &
difficult to remove around undercuts
Moderate tear strength, making
removal from sub-gingival areas risky
Sulfur in latex gloves and rubber dam
inhibit polymerization
Pouring of the stone should be
delayed by 1-2 hrs, liberation of H2 gas
DISADVANTAGES
63

64. 1960s
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
First elastomer to be developed primarily
to function as an impression material
64

65. • Base paste
Poly ether polymer
Fillers; colloidal silica
Glycoether or phthalate;
plasticizer
• Reactor paste
Alkyl – aromatic sulfonate ester;
cross linking agent
Fillers and plasticizers
Octyl phalate and 5% methyl
cellulose-thinning agents

66. The main chain is a copolymer
of ethylene oxide and tetrahydrofuran.
Cross linking is brought about by the
aromatic sulfonate ester via the imine end
Groups. 66
Polyether
Sulfonate
ester
Cross linked
rubber

67. Pleasant mixing and ease of
handling
More accurate than polysulfide
and condensation silicone
Good surface detail reproduction
Easily poured in stone
If kept dry, will be dimensionally
stable for up to 1 week
High cost
High stiffness
Bitter taste
Storage of impressions is
critical
cannot be left in disinfectants
for long
67

68. 68

69. Silicones
Polysulfides
Butyl rubber
Styrene/acrylonitrile
Dissolved in volatile
solvent such as
chloroform or ketone
Hydrated silica forms
ethyl silicate – bonds with
the tray
Polydimethyl siloxane –
bonds with the rubber 69

70. 1)Multiple mix technique
2)Single viscosity technique
3)Putty wash technique
70

71. Heavy and light body
mixed simultaneously
light body loaded in syringe
Tray adhesive applied
Light body injected into
prepared teeth
Heavy body loaded in the
tray
Final impression

72. 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.

74. All elastomers are compatible with
gypsum products
Excellent dimensional stability of
addition silicone and polyether
makes it possible to construct 2 or
3 casts
Hydrophobic addition silicone –
problem ????
74

75. • Surfactants are added to reduce the contact angle;
dilute solution of soap
• Most commonly used – non-ionic surfactants
oligoether or
polyether substructure
Hydrophilic part
Silicone compatible
Hydrophobic part
PVS
Diffusion – controlled transfer of
surfactant molecules from PVS to
aqueous phase
Reduction in surface tension
Greater wettability
75
water

76. Hydrophilized vinyl
polysiloxane

77. properties

78. Impression
material
Mean working time Mean setting time
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
Polyether 3.3 2.3 9.0 8.3
23°C 37°C 23°C 37°C
78

79. Temperature
Humidity
Viscosity
Factors affecting working-
setting time

80. 1)Polymerization shrinkage
2)Loss of by – product
3)Thermal contraction from oral temperature to
room temperature
4)Imbibition
5)Incomplete recovery of deformation

81. Addition
silicones
-0.17%
Polyether
-0.24%
Polysulfides
-0.40%
Condensation
silicones
-0.60%

82. Addition
silicones
Polyether
PolysulfidesCondensation
silicones

83. Addition
silicones
-0.17%
Polyether
-0.24%
Polysulfides
-0.40%
Condensation
silicones
-0.60%

84. Addition
silicones
Polyether
PolysulfidesCondensation
silicones

85. Addition
silicones
0.01-.03%
Polyether
0.03%
Polysulfides
0.5-2%
Condensation
silicones
0.05-0.1%

86. 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,

87. Clinical consideration :
o Subgingival regions are very thin – material
can tear
o Residual segment of impression material
difficult
to detect radio opacity of polysulfide can
help
o Severe gingival inflammation.
o Examine the gingival sulcus immediately
after impression removal and also the 87

88. 2 years
stannous
octoate oxidizes
Orthoethyl silicate is not stable in presence
of tin ester
1 to 2 years
Excellent shelf life; more than 2 years
Cool, dry environment
Tubes always tightly
sealed
Container closed
88

89. MATERIAL DISINFECTANTS
Polysulfide
Silicones
(by immersion-not
more than 30
min/spray)
2% Glutaraldehyde
Chlorine compounds
Iodophors
Phenolics
Polyether Chlorine compounds
Iodophors
Use disinfectant with short
immersion time(less than 10 min)
to avoid distortion(Polyether is
hydrophilic)
89

90. • 1)Impression making
• 2)Bite registration
– The material is fast setting.
– There is no resistance to biting forces.
– There is no odor or taste for the patient.
– It gains dimensional stability over time.
– It is convenient to use.
• 3)Duplication
Polyvinyl siloxane and polyether duplicating materials are superior in
accuracy than agar reversible hydrocolloid duplicating materials. *
*Accuracy and reproducibility of reversible hydrocolloids versus
elastomers duplicating materials Bahannan, S et al. The Saudi
Dental Journal 1995:7( 1)

91. Common
failures

92. ROUGH OR UNEVEN SURFACE
ON IMPRESSION
1. Incomplete polymerization cause
by premature removal.
2. improper ratio or mixing of
components
3. presence of oil or other organisms
on the teeth
4. Too rapid polymerization from high
humidity or temperature
5. Excessively high accelerator/base
ratio

93. BUBBLES
1. Too rapid polymerization
, preventing flow
2. Air incorporated during
mixing
IRREGULAR
SHAPED
VOIDS
1. Moisture or debris on
surface of teeth

94. ROUGH OR CHALKY STONE CAST
1. Inadequate cleaning of impression
2. Excess water or wetting agent left on surface of the impression
3. Premature removal of cast
4. Improper manipulation of stone
5. Failure to delay pour of addition silicone at least 20min

95. 1. Lack of adhesion of rubber to the tray
caused by not applying enough coats of
adhesive
2. filling tray with material too soon after
applying adhesive or using wrong
adhesives
3. Lack of mechanical retention for those
materials where adhesive is ineffective
4. Development of elastic properties in the
material before tray is seated
5. Excessive bulk of material
DISTORTION
95

96. 6. Insufficient relief for the reline
material
7. Continued pressure against
impression material that has been
developed elastic properties
8. Movement of tray during
polymerization
9. Premature removal from the mouth
10.Delay pouring of the polysulfide or
condensation silicone impression

97. Introduced in early 1988 by Genesis & LD Caulk
1. Polyether urethane dimethacrylate – elastomer resin
2. Chloroquinone – photoinitiator
3. Silicon dioxide – filler 0
Light body – syringe
Heavy body – tubes
97

98. Manipulation
1. Loaded tray is seated in the mouth
2. 8mm or larger diameter optical probe is placed in the
mouth below the tray
3. Blue light is activated for 3 minutes
4. Impressions can be poured immediately or stored up to 2
weeks
1. Long working time and short setting time.
2. Blue light is used for curing with transparent impression
trays.
3. Tear strength – 6000 to 7500 gm/cm2 (Highest among
elastomers)
4. Other properties are similar to addition silicones
Properties

99. 1. Special transparent trays
2. Difficult to cure in remote
area
DisadvantagesAdvantages
1. Controlled working time
2. Excellent properties
3. Ease of cold disinfection
without loss of quality.
4. The impression material is
also compatible with
gypsum and silver or
copper metallizing baths
99

100. It combines the benefits
of polyether and vinyl
polysiloxane impression
materials. The pleasant
tasting hybrid impression
material purportedly has
hydrophilic properties, high
tear strength, excellent
dimensional accuracy and
resistance to deformation.
It is available in two setting
times (fast and regular) and
four viscosities (putty, heavy
body, monophase and light
body)

101.  Soft elastomers
 Composed of powder that contains poly(ethyl methacryalte)
and liquid that contains an aromatic ester – ethyl alcohol
mixture (up to 30%)
 Within few days they become stiffer as a result of loss of
alcohol so need to be replaced every 3 days
1. Tissue conditioners for irritated mucosa
2. Temporary soft liners
3. Functional impression materials
101

102. 1. Hydrophilic; accurate impression in presence of saliva
2. Dimensional stability is fair
3. Low rigidity , Low tear strength
4. Adhere to themselves and are excellent for border molding and
correctable impression technique
5. Do not distort from water absorption, but they distort easily
when exposed to alcohol based disinfectants
6. Properties which make s the material effective are-
Viscous behaviour-allow adaptation to irritated denture bearing
mucosa for several days
Viscoelasticity which cushions the cyclic forces of mastication and
bruxism

103. •Tissue conditioners should not be cleaned by
scrubbing with a hard brush in order to prevent
tearing of the material. The use of soft brush
under running water is recommended.
•The greatest virtue of tissue conditioners is their
versatility and ease of use.
•The biggest flaw is that they are also misused

104. 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 and
irreversible hydrocolloids – more sensitive with
respect to handling considerations , mix-and-pour
techniques, which may affect accuracy. 104

105. 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.

106. • Anusavice KJ: Philips’ Science of Dental
Materials. 11th Edition. Elsevier:S Louis;2003
• William J. O’Brien: Dental Materials Properties
and Selection
• Craig RG,Restorative Dental Materials.9th
Edition. Mosby:St Louis;1993
• Impression materials: A comparative review of
impression materials most commonly used in
restorative dentistry DCNA 2007;51(3):629-642
• McCabe JF, Walls AW:Applied Dental
Materials.9th Edition.Blackwell
Publishing:Singapore;2008
• Kowdi MS, Patil SG.Prep manual for
undergraduates: Dental materials.

107. • Schleier PE, et al The effect of storage time on the
accuracy and dimensional stability of reversible
hydrocolloid materials. J Prosthet Dent 2001
;86(3):244-50.
• Jamani KD The effect of pouring time and storage
condition on the accuracy of irreversible hydrocolloid
impression. Saudi Dental Journal 2002:14(3).
• Woody et al Hydocolloids: A comparative study.J Am
Dent Assoc 1977,94:501-504
• Lemon JC et al Facial moulage:The effevt of a
retarder on compressive strength and working and
setting times of irreversibe hydrocolliid impression
material. J Prosthet Dent: 2003 ;90(3):276-81.

108. • Lee YK et al in this Effect of fluoride addition on the
properties of dental alginate impression materials study J.
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109. Thank you

110. ELASTIC Impression
MATERIALS
ABHISHEK KAVLEKAR