various impression materials used in dentistry

1. IMPRESSION MATERIALS
1
Dr.Madhu Billa
2nd year PG
SIBAR Institute Of Dental Sciences

2. KEY TERMINOLOGY

3. • Earliest dental materials were waxes used in the 18th and
19th centuries. Beeswax is reported as the material first used
in making oral impressions.
• Philip Pfaff-1756
– First described taking impression with softened wax
• Charles Stent-1857
– Introduced the first impression compound
• Sears-1937
– First used agar hydrocolloids for recording crown impressions.
Irreversible hydrocolloid are introduced in the early 1940s
HISTORY:

4. • SL Pearson-1955
– Developed synthetic rubber base impression
materials
• Polysulfide- Late 1950’S
• Condensation Silicone- Early 1960’s
• Addition Silicone-1970’s
• Polyether- Late 1970’s

5. • 1. Capable of plastic to rigid body transformation
• 2. Acceptable for a patient
- non-toxic, non-irritant, tasteless, reasonable
setting time
• 3. Good handling properties – easy to
prepare/mix, adequate working and setting
times
• 4. Accuracy and detail reproduction
• 5. Dimensionally stable
• 6. Resistant to mechanical stress
• 7. Resistant to disinfectant solutions
IDEAL REQUIREMENTS:

6. BASED ON SETTING AND ELASTICITY:
MODE OF SETTING RIGID ELASTIC
Set by chemical
reaction(irreversible)
Impression plaster, zinc
oxide eugenol.
Alginate, polysulfide,
polyether, silicone,
Set by temperature
change(reversible)
Compound, waxes Agar hydrocolloid.
6
CLASSIFICATION

7. 7
ACCORDING TO VISCOSITY OR TISSUE DISPLACEMENT
Mucostatic Impression Materials
Impression plaster
Agar
Alginate.
Light body elastomers.
Mucocompressive
Impression compound
Putty elastomers.

8. 8
ACCORDING TO THE USE OF THE MATERIAL:
Dentulous mouth:
Alginate
Agar.
Non aqueous elastomers.
Edentulous mouth:
Impression compound
Impression plaster.
Zinc oxide eugenol.
Wax.

9. Impression
Materials
Non-elastic
Elastic
Aqueous
Hydrocolloids
Non-aqueous
Elastomers
Polysulfide
Silicones
Polyether
Condensation
Addition
Agar (reversible)
Alginate (irreversible)
Plaster
Compound
ZnO - Eugenol
Waxes
O’Brien, Dental Materials & their Selection 19979

10. Zinc-oxide Eugenol Impression
Paste
• Supplied in two separate pastes dispensed in tubes
10
Components Percentage
Tube no 1 (base)
Zinc-oxide 87
Fixed vegetable or mineral oil 13
Tube no 2 (accelerator)
Oil of cloves or eugenol 12
Gum or polymerised rosin 50
Filler(silica type) 20
Lanolin 3
Resinous balsam 10
Accelerator solution(CaCl2) and color 5

11. • 1st reaction-hydrolysis of zinc oxide to its hydroxide
form
• When the 2 pastes are mixed,the phenol –OH of the
eugenol acts as a weak acid and undergoes an acid-
base reaction with zinc hydroxide
• Forms a salt- zinc eugenolate
11

12. Applications of ZOE
• Final impression of edentulous ridges
• As a wash impression with other impression
• As an interocclusal registration material
• As a temporary liner material for dentures
• As a surgical dressing
12

13. Manipulation
• Mixed on oil impervious paper or glass mixing slab
• Proper proportion of two pastes obtained by
squeezing 2 strips of paste of the same length,one
from each tube ,onto the mixing slab
• Flexible stainless steel spatula used for mixing
• 2 strips of contrasting colors combined with the first
stroke of the spatula ,mixing is continued for approx
1 min, until a uniform color achieved
13

14. Types of ZOE
• Classified as Hard paste(type I)
soft paste(type II)
• Final set for type I paste-10 min
type II paste-15min
• Setting reaction can be accelerated by adding small
amount of Zinc acetate or a drop of water in the paste
before mixing or by extending mixing time
• Retading setting time – by using cool spatula and
mixing slab
14

15. Advantages:
1. Low viscosity – no compression of soft tissues.
2. Dimensional stability (shrinkage less than 0.1 %)
3. Good surface detail reproduction
4. Low price
Disadvantages:
1. Cannot be used in deep undercuts
2. Eugenol allergy in some patients
15

16. PROPERTIES
CONSISTENCY AND FLOW
According to ADA specification No. 16, the spread is:
– Type I — 30 to 50 mm
– Type II — 20 to 45 mm
RIGIDITY AND STRENGTH
• The compressive strength of hardened ZOE is approximately 7
MPa two hours after mixing.
DETAIL REPRODUCTION
• It registers surface details quite accurately due to the good flow
DIMENSIONAL STABILITY
• A negligible shrinkage (less than 0.1%) may occur during
hardening.
BIOLOGICAL CONSIDERATIONS
• Some patients experience a burning sensation in the mouth due
to eugenol.
16

17. NONEUGENOL IMPRESSION AND SURGICAL PASTES
• The chief disadvantage of zinc oxide eugenol paste is the
burning sensation caused by eugenol. Hence noneugenol
pastes were developed.
• Noneugenol pastes consist of a base and reactor paste.
• The base paste contains ZnO, gum & lorothidol (fungicide).
• The reactor pastes contains coconut fatty acids, rosin
(thickening), chlorothymol (bacteriostatic), etc.
• Antibiotics like tetracycline may be incorporated at the
time of mixing. Eg. COE-PAK, WARDS WONDRPAK
• Light cured periodontal dressing materials and single
component pastes that set by heat and moisture in the
mouth are also available.
17

18. Impression compound
• Also called “modelling plastic”
• Thermoplastic material
• Supplied in the form of cakes(red) and sticks
(green, gray or red)
18

19. Composition
– Mixture of –waxes(principal ingredient)
thermoplastic resins
filler(increase viscosity and rigidity)
coloring agent
• Shellac, stearic acid and gutta-percha added
to improve plasticity and workability
19

20. Applications
• For making a preliminary impression in an
edentulous mouth
• For individual tooth impression
• Peripheral tracing or border moulding
• To check undercuts in inlay preparation
• To make a special tray
20

21. PROPERTIES
• it is used warm and then cooled to oral temperature,
at which it is fairly rigid.
• The setting mechanism is therefore a reversible
physical process rather than a chemical reaction.
• The thermal conductivity of dental impression
compounds is very low and therefore require heat
soaking to attain a uniform mix
21

22. FUSION TEMPERATURE
• When impression compound is heated in a hot water bath
the material starts to soften at approximately 39°C
Coefficient of Thermal Expansion (CTE)
• The CTE of compound is comparatively high due to the
presence of resins and waxes.
• The linear contraction from mouth temperature to room
temperature is 0.3%.
DIMENSIONAL STABILITY
• Since the release of strains is unavoidable, the safest way to
prevent distortion is to pour the cast immediately
DETAIL REPRODUCTION
• Surface detail reproduction is comparatively less because of
its high viscosity and low flow
22

23. Types of
Impression
compound
Type-I
(Lower fusing)
Type- II
(Higher fusing)
23

24. Advantages:
• 1. Can be reused, easy to use
2. Non-irritant and non-toxic
Disadvantages
• 1. Poor dimensional stability
• 2. Easy to distort when withdrawn from the
mouth
24

25. Impression Plaster
• Basically a gypsum product (Type-1)
• used as mucostatic impression material for
making final impressions for edentulous
patients
• Applicable to patients with displaceable soft
tissues that should be recorded in a passive
state
25

26. Composition
• CaSO4 . 0.5H2O β-hemihydrate
• Potassium sulfate – reduce expansion &
accelerates setting
• Borax – a retarder to prolong setting time
• Diatomaceous earth, quartz, lime - to make
the plaster more brittle
26

27. Indication: impression of edentulous ridges
Advantages:
Cheap and long shelf life, easy to prepare
Very good surface detail reproduction
Excellent dimensional stability
Disadvantages:
1. Very rigid – often need to be fractured when
removed from the mouth
2. Fractures if undercuts are present
3. may dry soft tissues, unpleasant to patients
27

28. Agar
• Reversible hydrocollloid
• Physical change of agar from sol to gel induced by
lowering temperature
• Gel liquefies to sol when heated to a temperature
known as liquefaction temperature(700C-1000C)
• When sol is cooled, it becomes gel at a point known
as the gelation temperature( btw 370C and 500 C)
• Thus called reversible hydrocolloid
28
AQUEOUS HYDROCOLLOIDS

29. Composition
29
Component Function Composition
Agar Brush – heap structure 13 – 17%
Borates Strength 0.2 – 0.5%
Sulfates Gypsum hardener 1.0 – 2.0%
Wax Filler 0.5 – 1.0%
Thixotropic
materials
Thickness 0.3 – 0.5%
Water Reaction 80%
Alkyl Benzoate Prevent growth of mold
in impression material
during storage.
0.1%

30. Making the Agar impression
• Process requires a 3 compartment
conditioning unit for the agar tray material
• Allows liquefaction,storage and tempering
30

31. Liquefy the hydrocolloid gel in the tube in
boiling water at 1000C for minimum 10 min
tube is then placed in a storage bath at 65°C
to retain the sol condition until needed
impression tray filled with hydrocolloid sol
from the tube taken from storage bath , gauze
pad placed over the top of the tray material
Tray placed in water filled tempering
compartment(at abt 45°C)
31

32. ADVANTAGES
1. Hydrophilic Impression material
2. Good elastic properties, Good recovery from
distortion
3. Can be re-used as a duplicating material
4. Long working time
5. High accuracy and fine detail recording
DISADVANTAGES
1. Only one model can be used
2. Extensive and expensive equipment required
3. Impossible to sterilize for reuse
4. Low dimensional stability & tear resistance

33. Uses of Agar
1. Widely used at present for cast duplication
2. For full mouth impression without deep undercuts
3. As tissue conditioner
4. Was used for crown & bridge before the advent of elastomers

34. Alginate
• Irreversible hydrocolloid
• Most widely used impression material
• Developed as a substitute for agar
34

35. Potassium or sodium alginate dissolves in water and reacts with calcium ions
Calcium sulphate dihydrate A reactor ,reacts with potassium alginate to form a
dihydrate insoluble alginate gel
Zinc oxide Filler particles, affects properties and setting time
Potassium titanium fluoride Accelerator ,counteracts the inhibiting effect of the
hydrocolloid on the setting of stone,ensures good
quality surface of the cast
Diatomaceous earth Filler particles, controls the consistency of the mix
and the flexibility of the set alginate
Trisodium phosphate Retarder,controls the settting time to produce
either regular or fast set alginates
Coloring agents
Flavoring agents
Composition
35

36. Gelation process
• Typical sol-gel reaction
• Soluble alginate reacts with calcium ions from
calcium sulphate and forms insoluble calcium
alginate
• Production of calcium alginate- rapid,doesn’t
allow sufficient working time
• Retarder trisodium phosphate added to
extend working time
36

37. – The measured powder is sifted into pre-measured water
– A vigorous figure – 8 motion, with the mix being stropped
against the sides of rubber mixing bowl
– Mixing time between 45 secs – 1 min
37

38. Advantages
• Ease of manipulation
• No need of expensive
equipments
• Relatively low cost
• Comfort to patients
• High viscosity
• Ability to displace
tissues
Disadvantages
38

39. 39

40. 40

41. Dustless alginate
• Organic glycol
• Identic dustfree alginate(Dux dental).
• Jeltrate Dustless( Dentsply Caulk).
• Integra dustfree alginate.( Kerr)
Alginot
• Multiple automix options
• Dimensional stability over 24 hours.
• Multiple pours.
• Final detailed impressions.
10/2/2016 41

42. CAVEX Color change(chromatic alg.)
• The alginate impression material with color
indications avoiding confusion about setting time.
• Color changes are visualizing the major decision
points in impression making end of mixing time
• And end of setting time ( tray can be removed from mouth) it
indicates two color changes violet to pink indicates the end of
mixing time.
• Pink to white indicates end of setting time.
• Other advantages of this material are improved dimensional
stability (upto 5 days)
• Good tear and deformation resistance
• Dust free
• Smooth surface, optimum gypsum compatibility.

43. SILICONISED ALGINATES
• Incorporation of silicone polymers. Hybrids of alginates and
silicone elastomers, Properties closely related to alginate
• Fine detail production and tear resistance ,Poor dimensional
stability
ANTISEPTIC ALGINATE IMPRESSION MATERIAL
• Introduced by Tameyuki Yamamoto, Maso Abinu.
• An antiseptic containing alginate impression material contains
0.01 to 7 parts by weight of an antiseptic such as glutaraldehyde
and chlohexidine gluconate per 100 parts by weight of a cured
product of an alginate impression material.
10/2/2016 43

44. Elastomers
Polysulfide Silicones Polyethers
44

45. Elastomers
• Formulated in several consistencies in
increasing content of filler
Extra light body
Light body
Medium or regular body
Heavy body
Putty(extra heavy)
45

46. Polysulfides
• First synthetic elastomeric impression
material introduced in 1950
• 2 paste system
• Available in low, medium and high
consistencies
• Made up of a base and accelerator/reactor
• Brands- COE-FLEX,PERMALASTIC,NEOPLEX etc
46

47. Composition
The Base
Polysulfide polymer(-SH,mercaptan gp) Principal ingredient
Titanium oxide and Zinc Fillers
Sulphate ,copper carbonate or silica Strengthener
Dibutyl phthalate Plasticizer (confers viscosity to base)
The Accelerator
Lead dioxide Reactor
Sulfur Promoter, accelerates the reaction
Oleic acid or Stearic acid Retarder, controls setting reaction
47

48. • Working time: 5-7 min( longest among elastomers)
• Setting time: 8-12 min
• Pouring the cast: impression must be poured within 30
min to 1 hr
• Each paste supplied in a dispensing tube with approx
sized bore diameters at the tip
• Equal lengths of paste extruded from each tube to
provide the correct ratio of polymer to cross-linking
agent
• Reaction starts at the beginning of mixing and reaches
its maximum rate soon after spatulation is complete
48

49. • Good flexibility
• High tear strength
• Hydrophobic
• Messy, stains clothes and has an offensive
odor
• Uses—impression for crown and bridge
edentulous impressions
49

50. Advantages Disadvantages
- High tear strength - Dimensionally unstable
- Long working time - Unacceptable odor
- Established precision - Untidy and stains clothing
- Economic - Long setting time
- Extensive shelf life - Least elastic recovery
- Less hydrophobic - Subsequent pours are less 50

51. Condensation silicone
• Supplied as two-paste system or base-paste
and a low viscosity liquid catalyst or a two-
putty system
• Putty used as tray material in conjunction with
a low-viscosity silicone
• Referred to as the Putty-wash technique
• Brands- Speedex
51

52. Composition
The Base paste
hydroxyl-terminated polydimethyl
siloxane
High molecular weight polymer
Silica or calcium carbonate Fillers
The Liquid Accelerator
Tin octoate Metal organic ester
Orthoalkyl silicate
Oil-based diluents
Thickening agents Increase viscosity 52

53. • Working time: 3 min
• Setting time: 6-8 min
• Impression must be poured as soon as
possible within first 30 min
53

54. • Curing involves a reaction of tri- and tetra-
functional alkyl silicates in the presence of
stannous octoate as a catalyst
• Condensation polymerisation of hydroxy –
terminated polydimethyl siloxane occurs with
tetraethyl orthosilicate in the presence of
stannous octoate(catalyst)
• This reaction results in the release of ethanol
molecules
• By-product: Ethyl alcohol
54

55. Properties:
• Pleasant odor and color.
• Excellent reproduction of surface details and highly elastic.
• Lesser dimensional stability
- high curing shrinkage (0.4 - 0.6%)
- permanent deformation due to shrinkage caused by the
evaporation of ethyl alcohol is also high (1-3%).
• Hydrophobic - needs a dry field..
• Biologically inert.
• Ethyl alcohol bye product on subsequent evapouration causing
contraction.
• Compatible with all gypsum products.

56. Addition silicone
• Commonly referred to as Polyvinyl
siloxanes(PVS)
• Supplied as low, medium, high and very high
consistencies
• Brand name- Aquasil
56

57. Composition
The Base
Polymethylhydrosiloxane Low molecular weight polymer
Fillers
The Accelerator
Divinyl polymethyl siloxane
Other siloxane pre-polymers
Platinum salt Catalyst
Reatrder Controls working and setting times
57

58. • Working time: 2-4.5 min
• Setting time: 3-7 min
• Cast can be poured upto 1 week after making
the impression
58

59. • Reaction activated by a platinum salt catalyst
(chloroplatinic acid) without the release of by-
products
• In presence of impurites or moisture,
secondary reaction takes place between the
residual hydrides and moisture leading to
evolution of hydrogen gas
59

60. Advantages
• Most elastic of currently available materials
• Virtually negligible distortion upon removal
from undercuts
• Exceptional accuracy in reproducing anatomic
details
• Dimensional stability allows pouring long after
impression making
• Excellent occlusal record registration material
60

61. Disadvantages
• Inherent hydrophobic nature
• Non-ionic surfactant wetting agent added to
silicone paste rendering the surface of the
impression more hydrophillic and called
hydrophilized addition silicone
• Sulfur contamination from natural latex gloves
inhibits the setting of addition silicone
• Touching the tooth with latex gloves before
seating the impression can inhibit the setting of
critical surface next to tooth
61

62. PROPERTIES
• Pleasant odor and color
• Excellent reproduction of surface details
• Mixing time of 45 secs ,setting time of 5-9 mins.
• Best dimensional stability
- low curing shrinkage (0.17 %)
- lowest permanent deformation (0.05 – 0.3 %)
• Stone pouring delayed by 1-2 hours
• Hydrogen gas bye product result in pinpoint holes in cast when
poured immediately
• Extremely hydrophobic, some manufacturers add a surfactant
(detergent) to make it more hydrophilic
• Good shelf life of 1-2 yrs
• Good tear strength (3000gm / cm2)

63. Polyether
• Supplied as two-paste system in low, medium
and high consistencies
• 2 types:
1. based on ring-opening polymerization of
aziridine group
2. based on an acid-catalyzed condensation
polymerization of polyether prepolymer with
alkoxysilane terminal groups
• Brands- IMPREGUM
63

64. 64
Composition:
Base Paste
Poly ether polymer
Colloidal silica (filler)
Glycol ether or phthalate (plasticizer)
Accelerator paste
Aromatic sulfonate ester (cross-linking agent)
Colloidal silica (filler)
Phthalate or glycol ether (plasticizer)

65. PROPERTIES
1. Pleasant odor and taste
2. Mixing time is 30 secs, setting time of 8 mins
3. Dimensional stability is very good.
Curing shrinkage is low (0.24%)
The permanent deformation is also low (1-2%).
4. Very stiff (flexibility of 3%), needs extra space,
around 4 mm is given.
5. Hydrophilic (moisture control not critical)
6. Shelf life extends upto 2 years

66. 66

67. Properties of Elastomeric impression materials

68. RECOMMENDED DISINFECTANTS
MATERIAL DISINFECTANTS
Polysulfide Glutaraldehyde, Cl compounds,
Iodophors & Phenolics for 2min
Silicones Glutaraldehyde, Cl compounds,
Iodophors
Polyether Cl compounds or Iodophors-2min
Alginate Cl compounds or Iodophors-2min
ZOE Glutaraldehyde or Iodophors
Impression compound Cl compounds or Iodophors

69. Modifications in polysulphides
Lead dioxide replaced by:
 Organic reactor like Cumene hydroperoxide or t-Butyl
hydroperoxide:
 Inorganic hydroxides such as Hydrated Copper Oxides: Hydrated
copper oxide produces a green mix.

70. Modifications in addition silicone
1. Addition silicone with Palladium - Hydrogen absorber.
Adv: Impressions can be poured immediately.
2. Fast Setting Addition Silicone: Aquasil Ultra Fast Set
3. Hydrophilized Addition Silicone
Adv: Reduced contact angle with water Improved
wettability.
Have intrinsic surfactants

71. Modifications in polyether
1. Soft Polyether: Penta soft, Impregum soft.
 Supplied as heavy and light body.
 Soft Technology makes it less rigid for easier removal from the
mouth.
2. Fast Setting Polyether: Impregum quick set
Penta soft Quick Set
3. Visible light cure material

72. Visible light cured polyether
impression material
• Consists of visible light cured polyether urethane
dimethacrylate resin to which photoinitiator and
photoaccelerator are added
• Filler- Si dioxide which has a refractive index close to
that of resin in order to provide translucency for
maximum depth of cure.
• Long working time, short setting time.
• Tear strength – 6000 to 7500 gm/cm2.
• Other properties similar to addition silicone.
72

73. Comparison of physical properties of light-curing
andself-curing dental impression materials
- Heish et al., JPD 1994
• This study evaluated the physical properties and accuracy of light-
curing impression material and to compare it with those of self-
curing impression materials currently used.
• Physical properties such as strain in compression, dimensional
stability, and tear strength were measured.
• it was found that the strain in compression of the polyether
urethane dimethacrylate was higher than that of the condensation
silicones, but lower than that of the addition silicones
• The dimensional stability showed that all of
the impression materials, except the polyether urethane
dimethacrylate, had a negative dimensional change 24 hours after
mixing. The polyether urethane dimethacrylate had extraordinary
tear resistance compared to the other impression materials 73

74. Rheological properties
• Viscosity and flow behaviour depends upon
- ease of mixing
-air entrapment during mixing
-tendency of trapped air to escape before the
impression is made
• All elastomers exhibit shear-thinning before
setting 74
PROPERTIES OF ELASTOMERIC
IMPRESSION MATERIALS

75. 2 categories of shear thinning phenomena—
• Pseudoplasticity
• Thixotropy
Pseudoplastic material- displays decreasing
viscosity with increasing shear stress and
recovers its viscosity immediately upon a
decrease in shear stress
Thixotropic material- doesn’t flow until sufficient
surface energy in the form of an impact force or
vibration force is applied to overcome the yield
stress of material
75

76. TEAR STRENGTH
– Important property - in
inter proximal and sub
gingival areas.
– Influenced by
• Consistency -
increased viscosity
increases tear strength
• Manner of removal -
rapid rate of force
during removal
increases tear strength
(Snap removal)
Polyether
Silicone
Hydrocolloids
Poly
sulfide

77. Elastic Recovery
– Elastic recovery -
“rebound” back to its
original shape, when the
set impression is
removed from the mouth
– Elastic recovery can be
maximized by blocking
the undercuts.
Polysulfide
Polyether
Condensation
silicone
PVS

78. FLEXIBILITY
Polysulfide
Poly
ether
Condensation
silicone
PVS
Clinical considerations :
Impression of multiple
periodontally compromised
teeth
Difficult to remove from
undercuts (Exceeds the tear
strength of material) -
Tearing

79. HYDROPHILICITY
PVS and Condensation silicones –hydrophobic
• Contains hydrophobic aliphatic hydrocarbon
groups surrounding the siloxane bond
 Polyether - hydrophilic
Contain functional groups that attract and interact
with water molecules through hydrogen bonding
Use of extrinsic /topical surfactant
• Dilute solution of soap.
• To lower the surface tension (decreases contact angle)

80. Hypersensitivity potential  polyether
Contact dermatitis
Point of consideration :
Residual segment of impression material  severe gingival
inflammation.
Polysulfide – lowest cell death count
Polyether –highest cell toxicity scores
.
BIOCOMPATIBILITY

81. Direct inhibition
• Direct contact with latex gloves
• Impression are made with rubber dam in place
Indirect inhibition
•Indirect contact of tooth and periodontal tissues during tooth preparation
and gingival displacement procedures. Contaminated surface will be
slippery and sticky to touch
Clinical consideration :
Use of non latex gloves – Vinyl gloves ,Polyethene gloves
Avoid touching the tooth preparation and gingival areas
Avoid handling retraction cord with gloved hands.
CONTAMINATION
Unpolymerized material remain
adherent to prepare teeth surface

82. Dimensional stability
6 major sources of dimensional change
1. Polymerisation shrinkage
2. Loss of condensation reaction by-product
3. Thermal contraction from oral temp to room
temp
4. Absorption of water or disinfectant over a
period of time
5. Incomplete recovery of deformation because
of plastic deformation
6. Incomplete recovery of deformation because
of viscoelastic behaviour
82

83. CONCLUSION
It is important that the dentist fully
appreciates the various features of these
materials, what it is that makes them so useful
for dental applications, and what their
limitations are. Only then will the dentist be
able to select the most appropriate material
for a particular application.

84. References
• Kenneth J. Anusavice: Philips’Science of Dental Materials Eleventh
Edition
• William J. O’Brien: Dental Materials Properties and Selection
• E. C. Combe: Notes on Dental Materials Fifth Edition
• John F. McCabe: Applied Dental Materials Seventh Edition
• V. K. Subbarao: Notes on Dental Materials Fourth Edition
• Clair D. Reitz, DDS and Nereyda P. Clark, DMD The setting of vinyl
polysiloxane and condensation silicone putties when mixed with gloved
hands. JADA Vol. 116:371-5, 1988
• Winston W.L. Chee, T.E. Donovan, R.L. Kahn. Indirect inhibition of
polymerization of a polyvinyl siloxane impression material: a case report,
Quint. Int. Vol. 22:133-5, 1991
• D. H. Pratten, M. Novetsky. Detail reproduction of soft tissues: A
comparison of impression materials. JPD Vol. 65:188-191, 1991
• John F. Lontz: State-of-the-Art Materials Used for Maxillofacial Prosthetic
Reconstruction DCNA- Vol. 34, No. 2, April 1990
• Terry E. Donovan, Winston W. L. Chee:A review of contemporary
impression materials and techniques DCNA- Vol. 48, No. 2, April 2004

85. 85
ThankYou…..