3. It should have pleasant taste,odor and aesthetic
Should not contain any toxic or irritating
ingredients
Should have good shelf life
Should be used with minimum equipments
Adequate strength so it will not break or tear
while removing
It should be dimensionally stable
it should be electroplated
It should be viscous enough to contained in the
tray and seated in the mouth
5. A. Based on its property-
rigid and elastic
B. Based on its setting-
reversible and irreversible
C. Based on its use-
use in dentulous and in
edentulous patient
6. mode of setting Rigid Elastic
Set by chemical rxn
{irreversible/
thermoset}
•Impression plaster
•ZOE
•Alginate
•Elastomers
Set by temperature
changes
{reversible/
thermoplastic}
•Impression comp
•waxes
•Agar
7.
8. It is thermoplastic impression material
It is classified as rigid, reversible impression
material which sets by physical change.
It is also called as modelling plastic.
Types-
Type 1-low fusing comp-(40-45 C)
Type 2-high fusing comp-(60-65 C)
9. This is soften by heat
loaded on tray and
pressed against the
tissue before cooled
Also used for making
single tooth impression
called tube impression
10. Initially used for
taking impression
then used as tray
so we also called
it as tray
compound
It is more viscous
when soft and
more rigid when
hard.
12. Waxes and resins-30%
Shellac -30%
Stearic acid -5%
Gutta percha -5%
Filler -25%
Colouring agent -trace
Principal ingredient
that comprises of
matrix
Improves plasticity
and workability
Increases viscosity at
temp above the
mouth temp and
increases rigidity of
compound.
13. It should solidify at or little above mouth
temp
It should not be injurious or harmful to oral
tissue
It should not contain irritating or toxic
ingredients
It should not undergo permanent
deformation or fracture while withdrawing
from mouth
Should be dimensionally stable
14. • For making primary
impression
• For individual tooth
preparation
• Border moulding type I
is used to duplicate
functional sulcus depth
• To check undercuts in
inlay preparation
15. 1} Low thermal conductivity
2}Glass transition temp -39 C(loses its hardness}
3}Fusion temp-43 C(soft to manipulate)
4}Co-efficent of linear expansion high due to
presence of resin and wax-0.3%
5}flow-
type1-3% at 37 C
80-85%at 45 C
type2-2% at 37 C
70-80% at 45 C
16. Small amt is softened over flame (not to be
boiled it because plasticizer are volatile)
If large amt like cakes are used then they are
softened by keeping in temp controlled
water bath
Comp is removed, worked with finger to
obtain uniform plasticity throughout mass
loaded in the tray and impression is taken
After impression cast should se pour
immediately
17. Overheating in water bath is not indicated as
the compound becomes brittle and grainy
because some of the low molecular wt
ingredients get leached out so the
composition might change.
18. Advantages
1)It can be reused for
same patient
2)It is correctable
3)Material can be
extended beyond the
tray border
Disadvantages
1)Because of high
viscosity difficult to
to record details
2)While taking
impression due to
pressure soft tissue
get compressed
3)Distortion due to
poor dimensional
stability.
19. Disinfectant solution for compound is 2%
alkaline glutaraldehyde solution.
The impression should immersed in this
solution for the required amt of time, rinsed
and the pour immediately.
24. Base paste (white in color).
Accelerator or reactor or catalyst paste (red in
color).
25. Base paste:
Zinc oxide(87%)
Should be finely divided and should
contain slight amount of water.
Vegetable or mineral oil(13%)
Acts as plasticizer and masks the
action of eugenol as irritants
Catalyst paste
Oil of clove or Eugenol(12%)
Reduces burning sensation.
Gum or polymerized Rosin(50%)
Speeds the reaction.
Filler(20%)
Lanolin(3%)
Canada balsam(10%)
Improves flow and mixing.
Other catalysts like zinc acetate
and glacial acetic acid
28. Particle size of ZnO powder: Small particles make the
setting time less.
Varying the length of the two pastes.
Longer the mixing, shorter is the setting time.
High atmospheric temp. and humidity accelerate
setting.
Setting delayed by cooling the mixing slab.
Zinc acetate or drop of water or acetic acid decreases
setting time by increasing the speed of formation of
Zn(OH)2.
29.
30. Two pastes of equal lengths.
Oil impervious paper or glass slab.
Spatula method (uniform color with no streaks
should be formed).
Pouring of the impression.
31. Sufficient flow.
Minimum tissue distortion.
Ease in beading and boxing.
Not washed out by saliva.
Adequate dimensional stability.
Adequate working time.
Can be checked in mouth repeatedly.
Does not require separating media.
Minor defects can be corrected.
32. Requires special trays.
Sticky.
Causes tissue irritation.
Temperature and humidity affect setting time.
Profuse secretion causes distortion.
Cant be used in undercut areas.
Brittle and require support.
33. As final impression material.
As corrective or wash impression.
As bite registration paste.
Used as stabilizing base plates and as temporary relining
material.
As surgical pack.
For temporary cementation.
34. Surgical paste: Used after certain periodontal surgeries
where sutures cannot be placed. The paste is placed over the
wound for retention of medicament.
Noneugenol impression and surgical paste: These
reduce the burning sensation and disagreeable taste caused
due to eugenol.
ZnO + 2RCOOH (RCOO)2Zn +H2O
Bite registration paste: These are used for recording
occlusal relationship between two occluding surfaces. These
have shorter ST to prevent distortion and more plasticizer to
prevent it from sticking.
37. INTRODUCTION
In 1925, Alphous Poller was granted a British patent for a
totally different type of impression material. Later Poller’s
Negacol was modified and introduced to the dental
profession as Dentacol in 1928
Agar hydrocolloid was the 1st successful elastic
impression material to be used in dentistry.
It is an organic hydrophilic colloid extracted from sea
weed.
Agar is a sulfuric ester of a linear polymer of galactose.
38. CLASSIFICATION
Type I - High consistency ( for use as tray material )
Type II - Medium consistency ( for use as tray or syringe
material )
Type III – Low consistency ( for use as syringe material )
39. USES
1. Widely used for cast duplication.
2. For full mouth impressions without undercuts.
3. As a tissue conditioner
4. It was used extensively for FPD impressions.
40. SUPPLIED AS
Gel in collapsible tubes.
As cartridges
In bulk containers.
41. COMPOSITION
Ingredients
Agar (13-17%)
Borates (0.2-0.5%)
Potassium sulphate (1-2%)
Wax (0.5-1%)
Thixotropic materials (0.3-
0.5%)
Alkylbenzoates (0.1%)
Coloring & flavoring agents
Water (around 84%)
Functions
- Basic constituent
- Improves the strength
- Ensures proper setting of the
cast
- It acts as a filler
- It acts as a plasticizer
- It acts as a preservative
- For patient comfort
- Acts as the dispersion medium
42. GELATION OR SETTING OF AGAR
Agar changes from the sol to the gel state & vice versa by a
physical process.
As the agar sol cools to form fibrils called micelles.
The fibrils branch & intermesh together to form a brush –
heap structure.
The fibrils form weak covalent bonds which break easily at
higher temperature in causes gel turning to sol.
The process of turning gel to sol is known as
LIQUEFACTTION (temp.. 70-100° C )
On cooling agar reverses to the gel state, the process is called
GELATION. (occurs at or near mouth temp. to avoid injury
to oral tissues)
43. Materials Required for Manipulation
Agar Hydrocolloid conditioner
Hydro colloid material
Water cooled rim lock trays
Syringe material
Duplicating mould
Rubber hose
44. The Hydrocolloid Conditioner
It includes 3 sections,
Boiling or Liquefaction section
( agar is placed in boiling water at 100° C for 10 min.)
Storage section
( 65-68° C is ideal & can be stored in sol condition)
Tempering section
( 46° C for 2 min. with the material loaded in tray)
It makes the material viscous.
45. Impression trays
Rim lock trays have a feature of water circulation through
the tray
It is a beeding on the inside edge which helps to retain the
material.
It has an inlet & outlet for connecting the water tubes
Should allow a space of 3 mm.
It extend distally to cover all teeth.
46. Working & Setting time
WT ranges b/w 7-15 min.
ST is about 5 min.
47. Properties of Agar Hydrocolloids
Gelation temp.: the sol should revert to a gel at a temp. of
37° C but not more than 45°C
Liquefaction temp. : it occurs at higher temp. at 70°C.
Hysteresis : the temp. lag b/w liquefaction & gelation.
Syneresis : the gel may lose water by evaporation from its
surface or exuding of fluid.
Imbibition : if the material is immersed in water, it
absorbs water by this process.
Flow : the material is sufficiently fluid to record the fine
details.
48. Elasticity : they are highly elastic
Accuracy & dimensional change : they are highly accurate
at the time of removal, but shrink when stored in air or
100% humidity and expand when stored in water.
Gel strength : it can withstand great stresses particularly
shear stress, without flow.
thus the impression should be removed as rapidly as
possible to avoid distortion.
49. Laminate Technique
Also known as Agar-Alginate combination technique.
Syringe material is injected on the area to be recorded.
An impression tray containing chilled alginate is placed,
so it will bind to agar that is already positioned.
The alginate sets by chemical reaction and agar by the
cooling effect of the alginate.
ADVANTAGES
Less air bubbles
Water cooled trays are not required
It sets faster
50. Wet Field Technique
The areas to be recorded are flooded with warm water.
Then the syringe material is introduced quickly in bulk to
cover the occlusal or incisal areas.
While the syringe material is still liquid, the tray material
is seated.
The hydraulic pressure of the viscous tray materials forces
the fluid syringe down into the areas to be restored.
This displaces the syringe material, blood and debris
through out the sulcus.
52. Advantages
Accurate dies can be prepared.
Good elastic properties help reproduce undercut areas.
Good recovery from distortion.
Hydrophillic
It is economical compared to synthetic elastic materials.
Low cost because it can be reused.
Can be reused when used as a duplicating material..
53. Disadvantages
Requires special & expensive equipment.
Doest not flow well
Can’t be electroplated.
Patient may feel thermal discomfort.
Only 1 model can be poured.
Has to be poured immediately.
Impossible to sterlize.
56. The word alginate comes from the term
‘Algin’
It is the peculiar mucous extract yield by
certain brown seaweed(algae).
It is classified as elastic irreversible
material that sets by chemical rxn.
58. Mode of supply
It is supplied as a packed powder
In bulk or in tins
A plastic scoop is supplied for dispensing
the bulk powder and the plastic cylinder for
measuring
59.
60. COMPOSITION
Sodium or potassium
or alginate -15%
Calcium sulphate-16%
Zinc oxide - 4%
Potassium titanium
fluoride -3%
Dissolves in water
and reacts with
calcium ion
Reactor reacts with
potassium alginate
and forms insoluble
calcium alginate
Acts as filler
Gypsum hardner
62. Setting rxn
When alginate powder is mixed with water
a sol is formed which later sets to form
gel by chemical rxn
The final gel i.e insoluble calcium alginate
is produce when sodium alginate reacts
with calcium sulphate
The reaction is retarded by using retarder
sodium phosphate.
64. Gel structure
Gelation is the conversion of sol to gel.
The final gel consist of a brush heap of
calcium alginate fibril network enclosing
unreacted sodium alginate sol, excess
water, filler particles and reaction by
product .
Fibrils are held by primary bond rather
then intermolecular forces.
65. Control of gelation time
By addition of retarder
By altering the temp of water
colder water longer is the gelation
time.
warmer water shorter is the gelation
time.
Even the mixing bowl and spatula can be
cooled to prolong the gelation time.
66. MANIPULATION
For mixing, we need
a clean flexible plastic bowl.
a clean wide bladed stiff metal spatula.
METHOD
Tumbling the container is done for the uniform
distribution of constituent before mixing.
Top is opened carefully so that to prevent very
fine particles to being distribute around the
room.
67. •The recommended w:p ratio is
38ml:16gm.
•Scoop supplied by the manufacturer is
taken the powder is level and sprinkle on
water
•Mixing is done rapidly with stirring motion
to wet the powder with water
•After that rapid spatulation is done against
the side of the bowl
•A vigrous figure of 8 motion is used with
the mix being a wiped or stropped against
the side of the rubber mixing bowl and
prevent entraption of air bubbles.
68. Mechanical device are also available
for spatulation
Its advantages are:
1)speed
2)covenience
3)elimination of human variable
The mix should be smooth creamy with minimum
voids and dose not drip off the spatula when raised
from the bowl
69. Over mixing
•Reduction in final strength
as the gel fibrils are
destroyed as they form
•Reduction in working time Under mixing
•Inadequate wetting, lack of
homogeneity and reduced
strength
•The mix become grainy and
poor recording of details
MIXING TIME
Fast set alginate-45 sec
Normal set alginate-60sec
WORKING TIME
Fast set alginate-1min
Normal set alginate-2 min
70. IMPRESSION MAKING
Loading the tray-
the alginate is mixed and loaded on a perforated tray so
that it can mechanically interlocked
the adhesive such as sticky wax or methyl cellulose can be
applied to the tray
the thickness of the gel between the tray and tissue
should be 3 mm
Seating the tray-
before making the impression the saliva should be wiped of
to prevent the material flowing along the throat and causing
nausea to the patient.
the impression is seated on the posterior portion first then
the anterior portion is seated.
Since the material sets from the tissue to the peripheral any
movement during this time can cause distortion
71. After removing the impression from the mouth
it should be washed to remove saliva
Covered with damp napkin to prevent
syneresis
Cast should be poured as soon as possible;
preferably within 15 mins after making
impression.
72. Impression disinfection
The irreversible hydrocolloid may be
disinfected by 10 min immersion in or
spraying of antimicrobial agent e.g
sodium hypochlorite, glutaraldehyde
without significant dimensional changes.
73. PROPERTIES
1)Setting time-
for fast setting material-1 to 2 min
for normal setting material- 2 to 4.5min
2) flexibility-
14% at the stress of 1000g/cm sq
3)Elasticity-
it is elastic but less as compared to agar
4)Reproduction of details-
suface detail reproduction is less as compared to agar
5)strength-
compressive sterngth-5000 to8000 g/cm sq
tear strength vary from 350-700 g/cm sq
74. 6)Dimensional stability-
alginate impression loses water by evaporation and
shrinks on standing air. if its placed in water it swells. so
kept in 100% humidity for least dimensional change
7)Shelf life-
it has short self life. material is stored in cool and dry
environment.
8)Biological properties-
silica particles present in dust which rises after fluffing
alginate powder is health hazardous so there are also dust
free alginate.
75. APPLICATION
1) Used for making
impression when
there are
undercuts
2) For making
impression for
orthodontic and
study models
3) For duplicating
models
76. RECENT ADVANCE
Dust free alginate-
to avoid inhalation problem of
alginate dust some material have been
introduce in the dustless version in which
the powder is coated with glycol.
Some products contain a chemical
disinfectant in the alginate powder for
infection control.
77. ADVANTAGE
It is easy to mix and
manipulate
Minimum
requirement of
equipment
Flexibility of the set
impression
Accuracy if properly
handled
Low cost
It is hygienic as fresh
material to be used
for each impression
DISADVANTAGES
It is not possible to make
the metal die which have
high resistance to
abrasion
It is not accurate enough
for crown and bride in
impression
It cannot be used alone
for compressing the tissue
It cannot be corrected
Distortion may occur if
the material is not held
stationary in relation to
the tissue through out he
setting period
79. TYPES
Acc to chemistry:
1. Polysulfide.
2. Polysilicones-
a. Condensation silicones
b. Addition silicones.
3.Polyether.
Acc to viscosity:
1. Light body or syringe consistency
2. Medium or regular body
80. 3. Heavy body or light consistency.
4. Very heavy or putty consistency.
Acc to wettability:
1. Hydrophilic
2. Hydrophobic.
81. USES
Used in FPD for impression of prepared teeth.
Impression for dentulous mouth for RPD.
Impression for edentulous Mouth for CD.
For bite registration.
Polyether used for border molding of edentulous custom trays.
Silicone duplicating material for refractory casts.
82. SUPPLIED AS
Collapsible tubes
Putty consistency supplied in jars
Light and regular body material supplied in cartridges.
83. PROPERTIES
Excellent reproduction of surface details.
Generally hydrophobic (except polyether).
Nearly complete elastic recovery.
Tear strength is excellent.
Dimensional inaccuracies may occur due to curing shrinkage,
loss of byproducts of reaction, thermal contraction, removal
before complete setting.
84. MANIPULATION
Single mix technique.
Multiple mix technique.
Reline technique:
- Two stage putty wash technique
- One stage putty wash technique.
85.
86. This is the first elastomeric impression material
introduced in 1950.
Also known as Mercaptan or Thiokol.
POLYSULFIDES
89. SETTING REACTION
Mercaptan + Lead dioxide
Polysulfide + Water
It is an exothermic reaction and loss of water causes
shrinkage.
90. PROPERTIES
Unpleasant color and odor.
Materials are extremely viscous and sticky.
MT 45secs ST 12-16mins.
Excellent reproduction of surface details.
Dimensional stability (highest permanent deformation and
elastic recovery improves with time).
High tear strength.
Low hardness and good flexibility.
Hydrophobic.
92. TYPES
The silicone impression materials are of two
types based on the type of polymerization
reaction:
Condensation silicones
Addition silicones.
Both silicones are available in different colors
like pastel pink, purple, blue, green, orange,
etc.
94. SUPPLIED AS:
Paste: Supplied as two pastes in unequal sized
collapsible tubes. Base paste in a large tube and
catalyst paste in a small tube.
Putty: Supplied in a single large plastic jar. Catalyst
as paste or liquid form.
They come in variety of colors. Base and catalyst in
contrasting colors to aid in mixing.
96. COMPOSITION
Polydimethyl siloxane
Colloidal silica or
microsized metal oxide
filler.
Color pigments.
Orthoethyl silicate
Cross linking agent.
Stannous octoate
Catalyst.
Base Catalyst
97. SETTING REACTION.
Dimethyl siloxane + Orthoethyl silicate
Stannous Octoate
Silicone rubber + Ethyl alcohol.
The ethyl alcohol formed as a by product evaporates
from the set rubber leading to shrinkage.
98. PROPERTIES
Pleasant color and odour.
ST 6-9mins MT 45secs.
Excellent reproduction of surface details.
Dimensional stability is less.
Tear strength lower than polysulfides.
Stiffer and harder than polysulfides.
Hydrophobic.
Self life less than polysulfides.
100. SUPPLIED AS:
Tubes: Base and catalyst paste in equal sized
tubes.
Cartridge form.
Putty jars: Two equal sized plastic jars containing
base and catalyst.
101. Available in four viscosities:
Light bodied.
Medium bodied.
Heavy bodied.
Putty.
102. COMPOSITION
Poly(methyl hydrogen
siloxane).
Other siloxane
prepolymers.
Fillers.
Divinyl polysiloxane.
Other siloxane
prepolymers.
Platinum salts-catalyst.
Palladium or hydrogen
absorber.
Retarders.
Fillers.
Base Catalyst
104. PROPERTIES
Pleasant odor and color.
May cause allergic reaction so direct skin contact to
be avoided.
Excellent reproduction of surface details.
ST 5-9mins MT 45secs.
Has best dimensional stability among elastomers.
Has good tear strength.
Hydrophobic.
Lower flexibility and harder than polysulfides.
Self life ranges from 1-2yrs.
105.
106. 106 POLYETHER
Good mechanical properties.
Good Dimensional Stability.
Base and accelerator in collapsible tubes.
Accelerator tube is smaller.
Available in 3 viscosities-
• Light Bodied
• Medium Bodied
• Heavy Bodied
AVAILABLE AS-
108. 108
It is cured by the reaction b/w aziridine rings which
are at the end of branched polyether molecule.
The main chain is a co-polymer of ethylene oxide and
tetrahydrofuran.
Cross linking is brought about by the aromatic
sulfonate ester via the imine end groups.
The reaction is exothermic (4 to 5 C)
Polyether + Sulfonic ester Crosslinked rubber
109. 109
1. Pleasant odor and taste.
2. Sulfonic ester can cause skin reactions.
3. Setting time – 6 to 8 mins.
4. Mixing time – 30 sec
5. Dimensional stability is very good.
6. It is extremely stiff (flexibility 3%)
7. Tear strength is good (3000 gm/cm).
8. It is hydrophilic.
9. It can be electroplated with silver or copper.
10. Shelf life is excellent (more than 2 years).
110. 110
• With addition silicon – equal scoop of base and
accelerator.
• With condensation silicon - required no. of scoops of
base and recommended amount of liquid or paste
accelerator is taken.
• In both cases mixing is done by kneading b/w the
fingers.
• Unlike addition silicon the quantity of catalyst paste is
very little. The 2 pastes therefore are of unequal length
and diameter.
PUTTY
PASTE
111. CONTD…
• The required amount thinner may be added
to the base and accelerator depending on
the viscosity needed.
• The quantity of accelerator needed is very
little.
• The ratio is usually displayed on a mixing
pad. Mixing time 30 sec.
111
FOR POLYETHER
112. 1. Impression can be made in custom or stock trays
2. Elastomer do not adhere well to the tray
3. An adhesive should be applied to the tray and
allowed to dry before making impressions.
4. Perforatd stock trays are used because perforations
helps to retain the putty in the tray.
5. Spacing is given b/w 2-4 mm.
6. Bulk of impression should be made with heavier
consistency
112
113. METHODS OF MAKING
IMPRESSIONS
113
SINGLE MIX TECHNIQUE
Tray used – Resin custom tray with 2-4 mm spacing
Viscosity used – regular
MULTIPLE MIX TECHNIQUE
Tray used - – Resin custom tray with 2-4 mm spacing
Viscosity used – (a) Heavy bodied
(b) Light bodied
114. CONTD…
RELINE TECHNIQUE
( 2 STAGE PUTTY-WASH TECHNIQUE)
Tray used – Perforated stock tray
Viscosity used – (a) Putty
(b) Light Body
RELINE TECHNIQUE
( 1 STAGE PUTTY-WASH TECHNIQUE)
Tray used – Perforated stock tray
Viscosity used – (a) Putty
(b) Light Body
114
115. AUTOMATIC DISPENSING AND
MIXING DEVICES
10/26/2015
115
• Double barrel caulking gun with mixing tip is
used.
• The tip contain spirals, forcing the base and
accelerator through these spirals result in
mixing.
117. 117
REMOVAL OF THE
IMPRESSION
The impression is dislodged from the mouth as quickly as
possible for the following reasons –
• Elastic recovery is better.
• Tear strength is higher.
118. INFECTION CONTROL
Rubber impression materials are disinfected by
immerging them in 2% glutaraldehyde for 10
mins or in chlorine di-oxide solution for 3 mins.
In case of polyether a spray of chlorine di-oxide is
preffered.
118
