alginates rich in guluronan form strong, brittle gels, whereas those rich in mannuronan form weaker and more elastic gels.
K ti f - To counteract the inhibitory effect of hydrocolloid on setting of gypsum and improves the surface of stone model Diatomaceous earth - increases the stiffness and strength of the gel produces smooth texture ensures a firm gel surface that is not tacky increases the flexibility of set impression
Sodiumtripolyphosphate and tetrasodium pyrophosphate are the two most common salts used
. The silaceous particle, are similar to asbestos fibres that produce fibrinogenesis and carcinogenesis. So inhalation of fumes should be avoided.
40ml water for 25gm powder
1:1 , 5:1
Types of Failure
HYDROCOLLOID are lyosol basically
consists of gelatin particles
suspended in water and water is the
dispersion medium .
Solution – uniformly dispersed solute
and solvent e.g. salt in water – exist as
a single phase
Suspension – visible insoluble
particles in solute e.g. dust in water
Emulsion – visible insoluble liquid in
liquid e.g. oil in water
Solvent and Solute
single phase, which
means a homogenous
mixture, where the solute
exists as small molecules
or ions in the solvent.
system, a dispersed phase
of particles of at least
sufficient size to be seen
in a medium.
Hydrocolloids can exist in 2 different forms – SOL
Sol – has the appearance & characteristics of a
Gel – a jelly like elastic semi-solid – produced from
sol by a process called GELATION – by formation of
fibrils or chains or micelles of the dispersed phase
which become interlocked – brush heap structure
GELATION – thus, the conversion of sol to gel .
It occurs in two ways.
1. By temperature changes:
Gelation is brought about by a reversible process. E.g.
Agar. The fibrils are held together by secondary molecular
forces. So that they break at slightly elevated temperature
and become reestablished as the hydrocolloid cools to
The temperature at which these changes occurs is the
The Gel is converted to sol when it is heated to a higher
temperature which is known as Liquification
The temperature lag is known as hysterisis.
2. By chemical change
Conversion of sol to gel is brought about by chemical
reaction, the fibrils thus formed are held together by
primary bonds and are unaffected by temperature.
Hence they are called irreversible hydrocolloid e.g.
Gel can be converted to sol (liquid) by heating,
cooling a sol causes it to become a gel.
Agar (hot) cool to 43 C Agar (cold)
(Sol) heat to 100 c (gel)
1925 – Alphous Poller – Negacol.
Modified & introduced in dental
profession as Dentacol in 1928.
Agar is an organic hydrophilic colloid
(polysaccharide) extracted from certain types of
seaweed( kelp plant).
It is a sulphuric ester of a linear polymer of galactose.
USES OF AGAR:
1. Widely used at present for cast
2. For full mouth impression without deep
3. As tissue conditioner.
4. Was used for crown & bridge before the
Water - 84 % - dispersion medium
Agar - 13 - 17 % - gelling agent, dispersed
Borates - 0.2 - 0.5% - improves strength and
setting of plaster or
K sulphate - 1 - 2% - it counters the retarding
effect of borates and provide good surfaces on
Alkyl benzoates - 0.1 % - preservatives
Fillers like diatomaceous earth, clay, silica, wax, rubber,
inert powders for control of strength, viscosity and
Acculoid / Cartrilloid (Van R)
Cohere / SuperBody / SuperSyringe (Ghingi-pak)
solid gel in collapsible tubes (for impressions)
No. of cylinders in a glass jar (syringe material)
In bulk containers (for duplication)
PREPARATION OF AGAR
Cleanliness, maintenance, and care of the conditioner
and strict adherence to time and temperature are
The water pots should be clean and free of any foreign
material, eg, wax, calcium deposits, and "scum" from
the boiling water.
Conditioners stay clean.
Failure to keep the pots clean will result in temperature
The conditioner is turned on.
Thirty minutes should be allowed for the water to reach
the desired temperatures before proceeding.
The boiling pot temperature should be maintained.
The water is brought to a boil, and boiling is continued
for 10 minutes.
Tooth preparation – should be caries free , without
undercuts( if present – should be filled with cements
resins or composites)
The cervical margins should be distinct.
TYPES OF AGAR
1. Heavy bodied – in poly tubes or flex
2. Medium bodied
3. Regular bodied
4. Light bodied – in syringes 16
•Trays should be selected and tried in the
patient's mouth before the impression material is
placed in them.
•There should be 3 mm of impression material
around the teeth occlusally and laterally.
The following steps are recommended
Heat in water at 100° C (212° F) for 8 - 10 minutes.
Store in water at 65° C (149° F) for 8-10 hours
Place in a tray at 65° C (149° F)
Temper in 46° C (115° F) water for 2 minute before taking the
impression to increase the viscosity and pressure applied
to the syringe material, also making comfortable for the
The solution is taken directly from the
storage compartment, is first ejected at the
base of the preparation and then the
remainder of the prepared tooth is covered.
In the meantime, tray material is tempered,
water soaked outer layer is soaked with a dry
guaze before placing to ensure good union
between tray and syringe material. The tray
material is positioned with passive pressure.
ADA specifications no.11 specifies that gelation
temperature must not be less than 37°C (98.6°F)
or more than 45°C (113°F).
Gelation is accomplished by circulating cool
water with a time not less than 5 minutes.
After gelation, impression is withdrawn in one
piece, parallel to line of withdrawal of prepared
Excess is trimmed and impression is stored in 2 %
potassium sulfate, controls water volume and has better
surface integrity in stone for 5 to 20 mins.
The potassium sulfate solution gives a harder surface to
the stone die material.
The potassium sulfate should not be washed out of the
impressions before the dies are poured.
The impression must be blown carefully; the impression
should not be dehydrated, but an excessive amount of
water or moisture should not be left in the impression.
Impression must be poured immediately after retrieval,
and disinfected with iodophor, bleach or glutaraldehyde.
The cast should be kept in contact with impression for at
least 30minutes, or preferably 60 minutes.
• 1 0 mins in boiling water (1 0 0 c)
• Every time material is reliquified, 3
mins should be added. this is
because it is more difficult to break
down the agar brush heap structure
after a previous use.
• 65 – 68ºC Temp. is ideal. It can be
Stored in the sol condition till
46ºC for 2-10 mins with material
loaded in the tray.
1. Gelation Temperature - after boiling for 8
minutes, the material should be fluid enough to
be extruded from the container. After tempering,
the sol should be homogeneous and should set to
a gel between 37" and 45" C when cooled.
2. Permanent deformation - The ANSI/ADA
Specification requires that the recovery from
deformation be greater than 96.5% (permanent
deformation be less than 3.5%) after the material
is compressed 20% for 1 second.
3. Flexibility - 4% to 15%. Materials with low flexibility
can be accommodated in areas of undercuts by
providing somewhat more space for the impression
material so it is subjected to a lower percentage of
compression during removal.
4. Strength –
compressive strength - 8000 g/cm2.
tear strength - 800 to 900 g/ cm.
Because agar hydrocolloid impressions are viscoelastic,
the strength properties are time dependent, and higher
compressive and tear strengths occur at higher rates of
5. Compatibilty with gypsum - Agar is more compatible
with gypsum model materials than alginates 23
6. Distortion during gelation
Contraction occurs during physical change from
sol to gel.
If the material is held rigidly in the tray , material
will shrink towards the centre of its mass , thereby
creating larger dies.
Since sol is the poor thermal conductor , rapid
cooling may cause conc. Of stress near the tray
where gelation first takes place.
Therefore water at 20 degree celcius is suitable for
Full arch impression
Sectional arch impression
Sectional arch impression techniques follows
same procedure as for full arch.
Selected tray should cover the tooth and its
adjacent two or more teeth.
1. Working model for inlay preparation.
2. Single or more teeth preparation.
LAMINATE TECHNIQUE: - [Schwartz (1951)]
It is a modified procedure using both reversible and
irreversible hydrocolloid. Tray hydrocolloid is
replaced with a mix of chilled alginate that bonds
syringe agar. Alginate sets by chemical reaction
whereas agar by temperature change.
The equipment needed for taking an agar impression
can be minimized by use of an agar-alginate, syringe-
tray combination impression.
In this procedure a syringe type of agar in a cartridge
is heated in boiling water for 6 minutes and stored in
a 65'c water bath 10 minutes before use.
The tray alginate of the regular set type is mixed with
10% more water than normally recommended and it
is placed in a tray.
The agar is injected around the preparation and the mixed
alginate is promptly seated on top of the agar. The alginate
sets in about 3 mins, and the agar gels within this time as a
result of being cooled by the alginate.
During the setting of the alginate and gelling of the agar a
bond forms between them. The impression may be removed
in about 4 minutes.
Since the hydrocolloid, not the alginate, is in contact with the
prepared teeth, maximum detail will be reproduced.
bond together better than others, with tensile bond strengths
ranging from 600 to 1100gm/cm2.
Values at the high end of the range resulted in cohesive
failure of the agar, where as those at the low end produced
adhesive failure between the agar and the alginate. It is
therefore advisable to follow the manufacturer's suggestions
for appropriate combinations.
Agar provides tissues details and solidifies
when it comes in contact with alginate
prepared in water at 70°F, Preventing rapid
the elimination of water-cooled
agar is more compatible with gypsum
model materials than alginates.
the accuracy is acceptable.
Economical and simple.
Liquification and storage of agar not
Decreased setting time (3minute). 28
WET FIELD TECHNIQUE
In this, tooth surfaces are purposely left wet and
areas are actually flooded with warm water.
The syringe material is introduced quickly,
liberally and in bulk to cover occlusal / incisal
While the syringe material is still liquid, tray
material is seated, the hydraulic pressure of the
viscous tray material forces the syringe material
into areas to be restored.
This motion displaces the syringe material,
blood and debris throughout the sulcus. 29
ADVANTAGES OF AGAR
1. Helps in preparing dies accurately.
2. Good elastic property and reproduces
most undercut areas.
3. Good recovery from distortion.
4. Non hydrophobic.
5. Palatable and well tolerated.
7. Can be reused.
Does not flow properly.
Cannot be electroplated.
Due to heat , it may be painful.
Tears relatively easily.
The word Alginate comes from ‘Algin’ which is a
peculiar mucous extract yielded by certain brown
Alginates are based on anhydro-ß-d mannuronic
acid or anhydro-P-D-guluronic acid.
S. Willium Wilding 1940s introduced.
Alginate was used as a substitute for agar when it
became scarce during World War II (Japan was a
prime source of agar)
Current status – alginate more popular than agar
1. Ester salt of alginic acid (sodium or potassium
or triethanolamine alginate) – 15 % - dissolves
in water and reacts with calcium ions to form
2. Calcium sulphate – 16 % - reacts with
potassium alginate & forms insoluble calcium
3. Zinc oxide – 4 % - filler and influences physical
properties and setting time of the gel.
4. Potassium titanium fluoride/silicate or k
sulphate – 3 % - gypsum hardener
6. phosphate – 2 % - retarder and Delays gelation by
reacting with calcium sulphate in preference to
soluble alginate to form insoluble gel.
7. Glycol - small amount - To make powder dustless
8. Chemical indicators - small amount
pH changes from alkaline to neutral to indicate
different stages in manipulation
Violet – during spatulation
Pink - ready to load
White - ready for insertion into mouth
9. Wintergreen/peppermint - trace amount
10. Disinfectants ( ammonia salts and CHX) - small
1. Complete denture prosthesis & orthodontics
2. Mouth protectors
3. Study models and working casts
4. Duplicating models
Type I – Fast setting.
Type II – Normal setting.
CHEMISTRY The alginate when mixed with water becomes a
sol. Gelation occurs by a chemical reaction .
The simplest and the popular method is reacting
the soluble alginate with calcium sulphate to
produce insoluble calcium alginate gel.
Chief ingredient is one of the soluble alginates
which is a linear polymer of the sodium salt of
Calcium sulfate (Reactor) reacts with potassium
or sodium alginate in an aqueous solution.
Production of Calcium alginate is delayed by the
addition of soluble salts acting as retarder like
sodium or potassium phosphate, oxalate or
2Na3PO4 + 3CaS04 Ca3(PO4) + 3Na2SO4
When supply of sodium phosphate is exhausted,
calcium ions begin to react with potassium
alginate to produce calcium alginate.
K2Alg + CaSO4 + H2O K2SO4 + Ca Alginate.
ADA no 18 describes two types of alginates
Type I (fast setting) - 1 to 2 min
Type II (normal setting) - 2 to 4.5 minutes
Fluff or aerate the powder by inverting the
container with the lead on several times –
ensures uniform distribution.
A clean flexible plastic bowl, a clean wide bladed
stiff metal / plastic spatula.
Tray selection : perforated metal rim lock tray or
plastic tray with retentive holes.
An excess of saliva around the teeth should be
removed -may cause bubbles in the
interproximal areas and on the occlusal surfaces
of the teeth. 40
•Powder is added to liquid to wet the powder
with water and to reduce entrapment of air.
•One scoop of pre-dispensed powder products
is used with the amount of water specified by
manufacturer (16g of powder to 38 ml of
•Once the powder is moistened, rapid
spatulation by swiping, or stropping against
the side of the bowl.
•A vigorous figure of 8 motion
can also be used.
Mix by hand spatulation / mechanical
spatulation with or without vacuum vigorously
for smooth creamy mix with minimum voids
(mixing time 45sec- 1 min) .
Air bubbles can be minimized by careful
application of the impression material to tooth
and into vestibular area with finger pressure
before placement of filled tray.
Filled tray is held passively and motionlessly and
material is left for 2 -3 minutes, till it becomes firm
because of adequate maturation of chemical set.
The thickness of the gel between tray and the tissues
should be 3 mm .
Working time 1 – 2 min
Tray should separated immediately suddenly with a jerk -
to avoid rocking and possible deformation of impression.
Excess material is trimmed .
The impression is washed in cold water to remove saliva
stored in an environment of 100% humidity or covered
with a damp napkin to prevent drying.
Impression should be poured within 10 mins for accuracy.
Cast should be separated from alginate impression as
soon as the stone has reached the optimal stage of rigidity
i.e. after 45 - 60 minute.
If allowed to remain for longer time, alginate
dehydrates and damaging changes take place in the
surface of stone.
The mixing time also affects strength of the gel
structure. The strength of gel can be reduced as
much as 50% if mix is not complete.
Under mixing can lead to grainy mix which leads
to reduced tissue detail reproduction.
Prolonged mixing results in weakened gel
structure as fibrils once formed will be broken
up. This will also lead to reduced working time 48
A mixing time of 45 seconds to 1 minute is
sufficient .Mixing should result in a smooth creamy
mix that does not drip off the spatula, when it’s
raised from the bowl.
A variety of mechanical devices are available for
spatulating the alginate impression material. The
required quantity of powder and water are
dispensed in a bowl. Spatulation is
carried out until a smooth creamy mix
of alginate is obtained. This results in a
superior mix than obtained manually.
Alginate is supplied as a powder i.e. packaged in bulk
in a sealed screw top plastic container or hermetically
sealed metal can. A plastic scoop and cylinder is
Preweighed packets constructed of plastic or metal
foil. it increase storage life and decrease moisture
Automatic mixing systems have been developed for
paste/paste alginates. These systems consist of a
mixing unit that mixes
- an aqueous base paste – sodium alginate polyacrylic
- an organic initiator paste - calcium sulphate-
hemihydrate and sodium
Alginate impression material deteriorates rapidly at
elevated temperatures by depolymerisation of the
alginate constituent. Materials stored for one
month at 65 degree Celsius are unstable for use as
they do not set at all or set too rapidly for any
practical use. Even at 54 degree Celsius there’s
evidence of deterioration.
The ADA specification number 18 for alginate
impressions specify that storage within original
container for 1 week at 60 degree Celsius in a
relative humidity of 100% the compressive strength
of the gel should not be less than 0.255Mpa.
POURING THE CAST
The pouring of the cast should start from one end of
arch. Afterwards it is placed in a humidator while stone
hardens. Stone cast or die should be kept in contact
with the impression preferably for 60 minutes or for a
minimum of 30 minutes.
A proper dental stone mixed with an accelerator is
painted over the entire anatomic surface of the
impression. A base is added only after the first
application of stone sets. This method protects against
volume change of the irreversible hydrocolloid
impression material and distortion of the unsupported
portions of the impression.
Easy to manipulate
Comfortable for patient
Viscosity and setting time can be altered.
Hydrophilic nature allows small presence of water on the
without causing major inaccuracies in the impression.
Distortion begins immediately after removal from the
Surface details and accuracies are poor.
Retention of alginate to non-perforated trays is
PROPERTIES1. Taste & odor: variety of colors and flavors.
2. Flexibility : 14% at a stress of 1000 gm/cm2.
3. Elastic recovery : 97.3%
Permanent deformation is less if set impression is
removed from mouth quickly.
The ANSI/ADA Specification requires that the
recovery from deformation be more than 95% (or a
permanent deformation of less than 5%) when the
material is compressed 20% for 5 seconds at the
time it would normally be removed from the mouth.
4. Reproduction of tissue details : lower than agar.
ADA Sp. Requires material to reproduce a line that
is 0.075 mm width.
5. Strength :
Compressive strengths – 5000-8000 gm/cm2
Tear strength - 350-700 gm/cm2
6. Dimensional stability: poor
7. Storage : cool, dry, tightly closed lid.
45 sec 75 sec 1-2.0
60 sec 120 sec 2-4.5
CONTROL OF SETTING TIME
Lengthening the setting time is better accomplished by reducing
the temperature of the water used with the mix than by reducing
the proportion of powder.
Reducing the ratio of powder to water reduces the strength and
accuracy of the alginate.
The setting reaction is a typical chemical reaction, and the rate can
be approximately doubled by a temperature increase of 10" C.
using water cooler than 18" C or warmer than 24" C is not advisable.
The clinical setting time is detected by a loss of surface tackiness.
CONTROL OF GELATION TIME
The gelation time is measured from the beginning of
the mixing until gelation occurs. It must allow
sufficient time for the dentist to mix the material, load
the tray and place it in the patient’s mouth.
Once gelation starts the impression must not be
disturbed because growing fibres will be fractured
and impression would be sufficiently weakened.
Optimal gelation time - 3 – 4 mins at temperature of
ADA specification no:18 for alginate have described
two types of alginate based on gelation time.
Type I (fast setting) : 1 – 2 minutes
Type II (normal setting) : gelation time 2.5 - 4
Gelation time is best regulated by the amount
of retarder added during manufacturing.In
another way the clinician can safely
influence gelation time by altering the
temperature of water used to mix the
Increase in temperature
leads to a decrease in
gelation time and vice
versa. However using
water cooler than 180C
and warmer than 54 c
is not recommended. 60
Gypsum casts is not compatible with both type of
hydrocolloid impression. To ensure maximum surface
hardness, methods employed are :
1. Immersing the impression in a solution containing an
accelerator for setting of gypsum products before
pouring impression with gypsum. This acts by two
(a) accelerates setting of gypsum.
(b) Reacts with gel to produce a surface layer that
reduces or prevents syneresis and eliminates the
retarding action of the gel.
Potassium sulphate, Zinc sulphate, manganese
sulphate, potash alum etc are chemicals usually used in
hardening solutions. Most effective is 2% K2SO4
2. Incorporating a plastic hardener or accelerator in
the material by the manufacturer. Potassium
titanium fluoride is most commonly used
In general a hardening solution is not required
unless specified by the manufacturer as most of the
commercially available alginates contain a hardener
1. In the form of a sol, containing the water. A reactor of
plaster of Paris is supplied separately.
2. Paste system, one containing the alginate sol, the
second the calcium reactor. These materials are said
to contain silicone and have superior tear resistance.
it is an extremely cost-effective, reliable
High quality material that delivers accuracy and
Available in a faster set time to increase patient
comfort and reduce chair time without
compromising performance or working time.
The improved thixotropic consistency reduces
slumping and displacement from the impression
Indications: Preliminary impressions, provisional
crown and bridge impressions, study models,
registration/opposing dentition impressions,
impressions for orthodontic models, sports guards,64
4. SILGINAT(Kettenbach LP)
It is a medium viscosity addition-curing elastomeric
polyvinyl silioxane impression material with alginate-like
consistency, specially developed for taking impressions of
the opposing jaw, temporary crowns/bridges and fabricating
The use of an A-silicone for opposing jaw impressions as well
as for precision impressions and bite registration leads to an
optimal standardized interaction.
Silginat is stable, has a low tear resistance and is easy to
Quantity - Cartridge (38 mL)
Working Time - 76 - 90 seconds
Complete Set Time - 2 min 30 secs
Viscosity - Medium Body
Set Times Available - Regular Set 65
5. SILGINAT FOIL BAG ALGINATE
Quantity Foil Bag - (362 mL)
Working Time - 90 seconds
Dispensing Plug & Press Dispensing System
Complete Set Time - 3 minutes
Viscosity - Medium Body
Set Times Available - Regular Set
6. STATUSBLUE(dmg america)
StatusBlue is an efficient, clean and stable alginate alternative.
A-silicone formula makes it quick and easy to take situation
impressions for temporaries, model-cast dentures, orthodontic
models, and opposing jaw models.
100% dust-free and cold disinfected, allowing for clean and safe
impression taking and delayed pouring, or re-pouring of
Quantity - StatusBlue for Automix Guns Canister 7 (+1 FREE)
50ml Cartridges 16 Automix Tips
Working Time - 1:15
Dispensing - Gun
Complete Set Time - 1:45
Viscosity - Type Medium Bodied ( < 35mm)
Set Times Available - 1:45
7. FREEALGIN MAXI
( Zhermack , inc)
A-silicone, alginate alternative, fast setting, medium
viscosity for all alginate indications. Packaged for all
automatic mixing machines.
1:1 mixing ratio.
Quantity - 6 X 380 mL Cartridge
base and catalyst
2 bayonet ring
Dispensing - Automatic Mixing
Scent/ Flavor - Mangustan Flavour
8.POSITION™ PENTA™ QUICK VPS
Accurate, dimensionally stable preliminary
impressions that take less time.
The material offers a fast working
and setting time, and is ideal for all
typical alginate impression indications.
Multiple pour capabilities save time and money, no
need to pour immediately, and no cleaning of bowls
it is dispensed at the touch of a button through 3M
ESPE’s fully automated Pentamix™ 3 Automatic Mixing69
Quantity - Kit includes: 1 base paste – 300ml; 1 catalyst
– 60ml; 1 Penta™ cartridge, lavender; 6 Directed Flow
Impression Trays (1 each size S, M, L, Upper and
Working Time - 1 min 10 sec (including mixing)
Dispensing - Automatic Mixer
Complete Set Time - 2 min 40 sec
Viscosity - Medium Bodied
Set Times Available - 3 min (Position Penta) and
2 min 40 sec (Position Penta Quick)
Introduced by Tameyuki Yamamoto,
patented in 1990.
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
The antiseptic may be encapsulated in a
microcapsule or clathrated in a cyclodextrin. 71
10. CAVEX COLOR CHANGE
Material with color indications
avoiding confusion about setting time.
Color changes visualizes the major
decision points in impression making
initially - white
end of mixing time - violet
end of setting time – pink to white
Other advantages of this material are
improved dimensional stability (upto 5 days)
Good tear and deformation resistance
Smooth surface, optimum gypsum compatibility.
11.LOW DUST ALGINATE
IMPRESSION MATERIAL Introduced by Schunichi in 1997.
This composition comprises an alginate a gelation
regulator and a filler as major components which
further comprises sepiolite and a
tetraflouroethylene resin having a true specific
gravity from 2-3.
The material generates less dust, has a mean
particle size of 1-40microns.
Excellent stone surface
Packed in 1 lb poly- aluminium pouches to increase
shelf life and reduce storage space.
2 scoops impression per pound.
Available in 2 forms – identic dustfree and
Material changes colour signaling
when to carry out each stage of the
Purple – spatulate
Pink – load tray
white – insert for impression
The color change is because of the indicator
Total elapsed time from start to
finish is just over 1 minute.
Impression can be kept over 100
hours without distortion or
shrinkage by simply rinsing and
enclosing in a plastic bag.
13. ALGINMAX (FUNG INT.)
High precision chromatic dental alginate.
Excellent dimensional stability allows casting of
the impressions even after 5 days (if impressions
are correctly stored in sealed containers).
Dust free alginate and lead and cadmium free.
Excellent gypsum compatibility and
Very high compressive strength and recovery
Flavour – vanilla mint
Color – pale blue
Setting time – 3 min
Shelf life – 3 years
Specifically designed for use with
any automatic delivery and mixing
system, Kettosil incorporates all of
the advantages of polyvinyl siloxane for accurate, fast
and easy impressions in any indication where an alginate
would normally be used .
Excellent Dimensional Stability.
Extremely low linear dimensional change value of 0.20%
comparable to polyvinyl siloxanes.
fullest possible recovery after removal from mouth, low
shrinkage during setting
Kettosil impressions can be poured 30 minutes
after removal from the mouth and up to 21 days
after impression taking.
Highly thixotropic properties for smooth,
controlled flow under pressure while minimizing
material slump and patient gagging.
Supplies bubble-free reproduction of surface
detail and critical areas such as gingival crevices
and occlusal grooves.
Reproduces every oral detail in stone study or
opposing models. Perfectly defined margins.
High Recovery From Deformation of 99.2% .
No Wasted Material
Activated cartridges of Kettosil can be sealed by
leaving unused material in the filler tip.
For the next impression, simply remove the
previous tip, then dispense as per routine.
Total working time of 1 minute 20 seconds.
maintains accuracy, saves time and maximizes
Can record fine
With the tray
Manipulation Special equipments No Special
Addition accept addition Does not accept
Electroplating Can not be it can be
Dipped in 2%
needs perforated stock tray
Dipped in 2% K2SO4
TYPES OF FAILURES
DISTORTION -Delayed pouring of impression.
-Movement of the tray during
- Early removal from mouth.
- Improper removal from mouth.
- Inadequate mixing
- Prolonged mixing
- Less water in mix
TEARING - Inadequate bulk
- Moisture contamination
- Too early removal from mouth
- Prolonged mixing
BUBBLES - Early gelation
- Air incorporation
VOIDS - Excess moisture or
debris on tissues
- Improper cleaning
- Premature removal of
- Improper manipulation of
Alginate (Irreversible hydrocolloid):
All the instrument i.e. rubber bowl, spatula are
sterilized or disinfected by spraying with 0.5%
NaOCl or 2% glutaraldehyde.
Spray technique -
Rinse under tap water to clean saliva or organic
Trim excess alginate from non-critical areas to
decrease amount of Microbial contamination.
Spray the entire impression surface and the
reverse side of the tray as well. It can be kept in
a plastic bag or humidor for the recommended
exposure time. .84
When it reached the lab, it is again cleaned with
water and stone cast is poured.
For immersion technique, disinfectant with
short exposure time is selected to minimize
distortion and deterioration of cast.
Aluminium sulfate treatment of alginate
After disinfection, the impression is sprayed
with aluminium sulfate and kept for 90 seconds
in a humidor.
Casts produced have better details and surface
smoothness than impression disinfected but
Success of alginate hydrocolloid impression
material since its emergence as an alternative to
reversible hydrocolloid was mainly due to its ease
of manipulation , comfort to the patient and less
But the facts like its dimensional instability, its
incompatibility with gypsum and availability of
better alternatives like elastomers which produce
better surface detail has replaced it but still it is
the impression material of choice in the field of
REFERENCES Philip’s science of dental materials (11thEdition)-
Restorative Dental Materials (11thEdition)- Craig
RG, Powers JM
Fundamentals of Fixed Prosthodontics (3rdEdition)
– Shillngberg Jr HT et al
Contemporary fixed prosthodontics – Rosensteil
Textbook of Operative Dentistry – Sikri VK
Basic dental materials – 1st edition – manapallil JJ
Operative Dentistry Modern Theory and Practice
(Indian ed. 1) - Marzouk MA, Simonton AL, Gross RD