The document discusses various types of impression materials used in dentistry, including hydrocolloids (agar and alginate), polysulfide, condensation polymerized silicones, and addition polymerized silicones. It provides details on the composition, chemical reactions, properties and uses of each material. For example, it notes that alginate impressions are inexpensive and easy to use but can deteriorate over time, while silicones and polysulfides are more accurate but may shrink slightly due to the release of water or ethanol during curing.
5. Hydrocolloid
• A dispersed phase (agar or alginate
molecules)
• Dispersion phase (water)
www.indiandentalacademy.com
6. A colloidal solution is called a
colloidal sol, or just sol, while the
semi-solid (jelly) colloidal material is
called a gel
www.indiandentalacademy.com
10. C O
C C
C
O
O
H
C
OH
C
O
C C
C
O
H
C
HSO4
C
OC
C
C
OH
OH
OH
C
H
H
H C H H
H
C
H
H
H
OHC
H
H H
OH
OH
OH
H H
H H
OH
H
8 n
Agar
www.indiandentalacademy.com
11. C O
C C
C
O
O
H
C
OH
C
O
C C
C
O
H
C
HSO4
C
OC
C
C
OH
OH
OH
C
H
H
H C H H
H
C
H
H
H
OHC
H
H H
OH
OH
OH
H H
H H
OH
H
8 n
www.indiandentalacademy.com
13. Boiling
Boil at 100°C (212°F) for
10 min (12 min if
reboiled).
Storage
Store at 65°C (150°F) for
a minimum of 10 min.
Can be stored for 5 days
before it has to be
reboiled.
Tempering
Temper at 43 - 46°C (110 -
115°F) for 5 -10 min before
placing impression in the
mouth. www.indiandentalacademy.com
14. Agar
• Agar (13-17 weight-%)
• Borates (0.2-0.5 weight-%)
• Sulfates (1.0-2.0 weight-%)
• Filler, often diatomaceous earth (0.5-5.0
weight-%)
• Thixotropic materials (0.3-0.5 weight-%)
• Water (remaining amount)
www.indiandentalacademy.com
16. C O
C C
C
O
O
H
C
OH OH
OH
O
n
H H
H
C
Anhydro-β-d-mannuronic acid
www.indiandentalacademy.com
17. C O
C C
C
O
O
H
C
OH OH
OK
O
n
H H
H
C
Potassium alginate
Soluble salts of anhydro-beta-d-
mannuronic acid are used in dental
alginate impression materialswww.indiandentalacademy.com
18. Sodium, potassium and triethanol
amine alginates are used in dental
alginate impression materials
www.indiandentalacademy.com
19. C O
C C
C
O
O
H
C
OH OH
OK
O
C O
C C
C
OH
C
OH
OK
O
C O
C C
C
OH
C
OH OH
O
C H H
H
C H H
H
C H H
H
OK
OH
www.indiandentalacademy.com
20. C O
C C
C
O
O
H
C
OH OH
OK
O
C O
C C
C
OH
C
OH
OK
O
C O
C C
C
OH
C
OH OH
O
C H H
H
C H H
H
C H H
H
O-
OH
O
O
O
H
O
O
OH
O
O
OH
O
H H
H
H H
H
H H
H
O-
C
C C
C
C
C
C
C
C
C C
C
CC
C C
C
C
OK OK
OH OH
OH OH
OHOH
Ca++
By adding a divalent ion, such as Ca2+
,
alginate chains can be linked together
www.indiandentalacademy.com
21. C O
C C
C
O
O
H
C
OH OH
OK
O
C O
C C
C
OH
C
OH
OK
O
C O
C C
C
OH
C
OH OH
O
C H H
H
C H H
H
C H H
H
O-
OH
O
O
O
H
O
O
OH
O
O
OH
O
H H
H
H H
H
H H
H
O-
C
C C
C
C
C
C
C
C
C C
C
CC
C C
C
C
OK OK
OH OH
OH OH
OHOH
Retardation: 3 Ca++ 2 PO4
---
Ca3(PO4)2+www.indiandentalacademy.com
25. How to Improve Gypsum
Surface Contacting
Hydrocolloid Impressions
• Rinse impression
• Use impression material containing an
accelerator for gypsum
• Rinse impression in a solution
containing an accelerator for gypsum
• Rinse the impression in a gypsum slurry
www.indiandentalacademy.com
27. Alginate – Reasons for Its
Popularity
• Easy to manipulate
• Comfortable to the patient
• Relatively inexpensive
• Does not require elaborate equipment
www.indiandentalacademy.com
28. Function of the Filler
• Increases strength
• Increases stiffness
• Produces a smooth texture
• Insures a firm gel surface that is not
tacky
www.indiandentalacademy.com
30. Most alginates require mixing times
of 45 to 60 s (always check the
instructions)
www.indiandentalacademy.com
31. Factors Influencing Gelation
Time
• Product
• Type
• Age
• How powder has been stored
• Water/powder ratio
• Temperature
www.indiandentalacademy.com
33. Tools Needed for Mixing and
Making an Alginate Impression
• Rubber cup
• Spatula (right shape)
• Scoop for powder
• Cup for measuring water
• Impression tray
• Wet paper towel and a plastic bag
www.indiandentalacademy.com
39. A deviation of only 15% from the
recommended liquid/powder ratio will
markedly affect the consistency of the mix
and the setting time of the alginate
impression material
www.indiandentalacademy.com
40. Potential Problems
• Too densely packed powder
• Trapped air inside the scoop
www.indiandentalacademy.com
63. Polysulfide Impression
Material
• Base (white paste)
– Polysulfide rubber
(80-85%)
– Titanium dioxide,
zinc oxide, copper
carbonate or silica
(15-20%)
• Accelerator (brown
paste)
– Lead dioxide (60-
68%)
– Dibutyl or dioctyl
phthalate (30-35%)
– Sulfur (3%)
– Other substances
such as magnesium
stearate and
deodorants (2%)
Pour within 30-60 minuteswww.indiandentalacademy.com
74. Silicone Impression Material
(condensation polymerized)
• Base (paste)
– Dimethyl siloxane
– Copper carbonate or
silica (35-75%)
• Accelerator (liquid or
paste)
– Stannous octate
– Alkyl silicate
– Filler (in case of
paste)
Should be poured as soon as possible
www.indiandentalacademy.com
77. HO Si O Si OH
CH3 CH3
CH3CH3
n
Hydroxy terminated poly(dimethylsiloxane)
www.indiandentalacademy.com
78. Si OH
CH3
CH3
Si OH
CH3
CH3
HO Si
CH3
CH3
HO Si
CH3
CH3
5
Si
OC2H
OC2H5
H5C2O
H5C2O
Alkyl silicate
www.indiandentalacademy.com
79. Si
O
O O
O
Si
Si Si
Si
CH3
O O
OO
CH3
CH3
CH3
CH3
CH3
CH3
CH3
HOC2H5H5C2OH
H5C2OH HOC 52H
www.indiandentalacademy.com
80. Polysulfide releases water
Hydroxyl terminated poly(dimethylsiloxane
releases ethanol
Which material can we expect to shrink more?
Condensation Polymerized Non-
Aqueous Elastomeric Impression
Materials
www.indiandentalacademy.com
83. Silicone Impression Material
(addition polymerized)
• Base (paste)
– Low molecular
weight polymethyl
hydrogen siloxane
• Accelerator (liquid or
paste)
– Divinyl polymethyl
siloxane
– Colloidal platinum or
palladium particles
– Coloring agent
– Surfactant
A-silicones are difficult to pour and can release hydrogen gas.
Latex can inhibit the polymerization process.www.indiandentalacademy.com
84. O Si CH CH2
CH3
CH3
O Si CH CH2
CH3
Poly(vinyl siloxane)
CH3
Si
O
Si
O
Si
O
O
CH3
CH3
H3C
H
H
H
+
+
Polymethyl hydrogen siloxaneDivinyl polymethyl siloxane
www.indiandentalacademy.com
85. O Si CH CH2
CH3
CH3
O Si CH CH2
CH3
CH3
Si
O
Si
O
Si
O
O
CH3
CH3
H3C
H
H
H
www.indiandentalacademy.com
86. O Si CH2
CH3
CH3
O Si CH2
CH3
Poly(vinyl siloxane) after setting
CH3
Si
O
Si
O
Si
O
O
CH3
CH3
H3C H
CH2
CH2
www.indiandentalacademy.com
89. Polyether Impression Material
• Base
– Polyether with ethylene
imine rings
– Silica
– Glycol ether phthalate
• Catalyst paste
– 2,5-dichlorobenzene
sulfonate
– Thickening agent
Often supplied with a thinner that contains octyl phthalate
and about 5% methyl cellulose as a thickening agent.
Rigid material. Easy to pour. Can cause allergic reactions.
www.indiandentalacademy.com
98. Biological Considerations
The catalyst system of some polyether
impression materials are known to
cause hypersensitivity reactions
www.indiandentalacademy.com
114. Impression is first made with the putty and a
spacer. After the putty has set and the
spacer has been removed, light body
material is injected around the tooth and into
the previously made putty impression.
www.indiandentalacademy.com