Impression materials and techniques in fpd /orthodontic courses by Indian dental academy

IMPRESSION MATERIALS &
TECHNIQUES IN FIXED
PARTIAL DENTURES
INDIAN DENTAL ACADEMY
Leader in continuing Dental Education
www.indiandentalacademy.com

CONTENTS
• Introduction
• Definition
• Ideal impression material
• Review of literature
• Elastic impression materials
- Reversible hydrocolloids
- Polysulfide polymers
- Condensation silicones
- Polyether
- Addition silicones
- Polyether urethane dimethylacrylate
• Impression techniques
• Disinfection
• Conclusion
• References www.indiandentalacademy.com

INTRODUCTION
• Function of the impression made of prepared teeth is
to provide an accurate negative reproduction of the
teeth & surrounding structures which can serve as a
mould to obtain a cast, on which a planned
restoration is fabricated.
• Accurate & stable impression materials are required
which can exactly reproduce the prepared tooth
structure.

DEFINITION
In dentistry, an impression is a negative
likeness or a replica of the teeth &
surrounding structures that is necessary to
obtain a cast.

IDEAL IMPRESSION MATERIAL
The fabrication of casting requires an impression
material that produces an accurate negative likeness
of the oral tissues.
The properties of an ideal impression are:
1. Complete plasticity before cure
2. Sufficient fluidity to record fine detail
3. The ability to wet the oral tissues
4. Dimensional accuracy
5. Dimensional Stability
6. Complete Elasticity after cure
7. Optional Stiffness

Other requirements of the impression that
influence clinical acceptability.
The ideal material should:-
1. Have an infinite shelf life.
2. Need least armamentarium.
3. Be nontoxic & nonirritating.
4. Have acceptable odor, taste & color.
5. Have suitable working & setting times.
6. Have strength to resist tearing.
7. Be compatible with model & die materials.
8. Be inexpensive.
9. Be easy to dispense, proportion & mix.
10. Be easy to clean up.
11. Facilitate visualization of finish line.
12. Permit multiple die pours.
13. Facilitate the clinical identification of beginning & end
of cure. www.indiandentalacademy.com

REVIEW OF LITERATURE
• Linke B.A., Nicholls J.I., Faucher R.R. (1985)-
conducted a study on the distortion analysis of stone
casts made from impression materials. Six different
impression materials were tested. They concluded:-
1. The impression materials all produced casts with an
arch perimeter larger than the standard reference
model.
2. Reversible hydrocolloid impression material
produced significantly less interabutment distortion
than the other impression materials.
3. The silicone-irreversible hydrocolloid produced less
interabutment distortion than the irreversible
hydrocolloid.

4. Adding the light body silicone- irreversible
hydrocolloid& the modified reversible hydrocolloid
did not significantly decrease the overall distortion
commonly noted for regular-body silicone-
irriversible hydrocolloid, respectively.
5. Significant differences exist among the impression
materials, however, relative to the impression
materials that are currently being used successfully,
the combinations of irreversible hydrocolloid with
silicone & modified reversible hydrocolloid with
irreversible hydrocolloid were clinically acceptable.

• Pratten D.H., Craig R.G.(1989)- conducted a study
to compare the wettability of a new hydrophilic
addition silicone with that of other impression
materials. Specimen from various viscosities of
polyether, polysulfide, hydrophobic addition silicone,
& hydrophilic addition silicone were formed against a
smooth surface. They concluded that the differences
between pairs of contact angle means were found to
be statistically significant except for the polyether-
hydrophilic addition silicone pair & that the wettability
of the hydrophilic addition silicone impression
material was found to be not significantly different
from that of a polyether impression material.

• Drennon D.G., Johnson G.H., Powell G.L.(1989)-
conducted a study to find the accuracy & efficiency of
disinfection by spray atomization on elastomeric
impressions. 5 disinfectants were used on polyether,
polysulfide & addition silicone which were applied to
the impressions by spray atomization. They
concluded,
- The spray disinfectants did not appreciably alter the
dimensions of casts made with elastomeric
impressions.
- The most accurate casts were produced by addition
silicones even after disinfection.
- The impressions were contaminated with selected
test organisms which were disinfected by spraying.
The results showed an optimal disinfection of the
impressions.

• Tjan A.H.L., Nemetz H., Nguyen L.T.P., Contino R.
(1992)- conducted a study to find the effect of tray
space on the dimensional accuracy & stability of
impressions made from 4 brands of monophasic
polyvinyl siloxane material. It was assessed on the
recovered stone casts by quantitative & qualitative
methods. They concluded, that both evaluation
methods agreed that tray space & repeat pour did not
affect the accuracy of the dies for individual castings.
However, the measurement of the interpreparation
dimensions appeared to suggest a possible potential
problem for an FPD when cast in one piece because
of the significant reduction in the interpreparation
distance. However, from these findings it can be
concluded that a rigid stock tray can be used with a
monophasic polyvinyl siloxane impression material.

• Millar B.J., Dunne S.M., Robinson P.B.(1998)-
conducted an In vitro study with the purpose of
comparing the number of surface defects in addition-
cured silicone impressions recorded with monophase
materials in stock trays & two-phase impressions in
custom trays. They concluded, that the monophase
addition cured impression materials in stock trays
carries an increased risk of void formation on the
surface of the impression when compared with two-
phase addition silicone materials in custom trays.

ELASTIC IMPRESSION
MATERIALS
• As per ADA Sp. No. 19 - non-aqueous elastomeric
dental impression materials.
• There are a large variety of materials for making a
precision negative mold of soft & hard tissues.
1) Reversible Hydrocolloid.(Agar)
2) Polysulfide Polymer.
3) Condensation Silicone
4) Polyether.
5) Addition Silicone.

• These materials are available in various
viscosities:-
1. Light body or syringe consistency
2. Medium or regular body
3. Heavy body or tray consistency
4. Very heavy body or putty consistency

REVERSIBLE HYDROCOLLOID
• Also known as Agar Hydrocolloid, Hydrocolloid,
Agar-Agar.
• Polysaccharide derived from seaweed.
• Patented in 1925 and introduced to United States in
the late 1920’s
• J.D. Hart of Wewoka, Oklahoma in 1930 began to
use this material for fabrication of cast restoration.
• Supplied as preformed gel in polyethylene tubes that
is liquefied before use.
• Forms available are collapsible tubes, capsules
and “Sausages.”

• Before use, the material is subjected to a controlled
regimen with three water baths.
1. Liquifying Bath – At 1000
C
2. Storage Bath – At 630
– 660
C
3. Tempering Bath – At 440
–460
C
• At elevated temperatures, it changes from a gel to a
sol.
This change is reversible, i.e. as the material
cools, the viscous fluid sol is converted to an elastic
gel.
GEL SOL GEL

• Trays for reversible hydrocolloid impressions have
integral cooling water channels to accelerate
gelation.
• Gelation occurs from the tray towards the tissues.
The last portion of the material to gel contacts the
tissues, so any shrinkage accompanying gelation is
compensated for. The hydrocolloids thus have
excellent dimensional accuracy.

• Lack of dimensional stability is due to the ease
with which water can be released from (syneresis) or
absorbed by(imbibition) the material.
Combined effect of evaporation, imbibition, and
syneresis are so deleterious that the impression must
be poured immediately to avoid distortion and to
produce casts of excellent dimensional accuracy &
acceptable surface detail.
• Ways for storing impressions following removal
from the mouth:-
Wet towels, humidors, water baths & 2%potassium
sulfate solution baths.
• Disinfection:- Iodophor disinfectant is added to
water to further reduce risk of cross contamination.www.indiandentalacademy.com

Advantages:-
• Hydrophilic
• Long working time
• Low material cost
• No custom tray required.
Disadvantages:-
• Low tear resistance
• Low stability
• Equipment needed.
Uses:-
• Multiple preparations
• Problems with moisture
Precautions:-
• Pour immediately
• Use only with stone.

POLYSULFIDE POLYMER
• Also known as rubber base, mercaptan or thiokol
rubber.
• Introduced in the early to middle 1950’s.
• Supplied as:-
2 tubes:-
BASE :- contains a liquid polysulfide
polymer mixed with an inert filler.
ACCELERATOR :- lead dioxide mixed with
small amounts of sulfur & oil,
acts as an oxidation initiator.
When 2 pastes are mixed,
Increased viscosity & finally elastic material.

• Polymerization …. moisture & temperature.
• Hydrophobic material…
- no moisture on preparation when impression is made
- thin layer of moisture on the surface … make the cast
slightly larger.
- moisture incorporated during injecting process..folds,
creases & voids in impression… fins & assorted
projections on cast.
• Have better dimensional stability & tear strength than
hydrocolloids.

• Impression should be poured as soon as possible.
• According to Luebke RJ et al(1979), impression
pouring delayed over an hour resulted in clinically
significant dimension change.
• Most polysulphide materials are polymerized with the
aid of lead peroxides - typical brown colour of the
material.
Alternatives to lead are :- Copper hydroxide
( polymerized form light green)
• Polysulfide unique … Radiopaque … presence of
lead dioxide in the formula … makes it toxic &
irritating to soft tissue when it becomes trapped.

Advantages:-
1. High tear strength.
2. Easier to pour than other elastomers.
Disadvantages:-
1. Messy
2. Unpleasant odor ..
3. Long setting time.
4. Stability only fair.
Precautions:-
1. Pour within 1hour.
2. Allow 10min. to set.

CONDENSATION SILICONE
• Also called organo-tin silicones.
• Named after the nature of their
polymerization reaction.
• Odorless & can be pigmented to any shade.
• Dimensional stability is less than
polysulphide but greater than reversible
hydrocolloid.

• Supplied as:- 2 pastes
- Base paste:- liquid silicone polymer with terminal
hydroxyl group, mixed with inert fillers.
- Reactor :- viscous liquid, consists of a crosslinking
agent, ethyl silicate, with an organo-tin
activator, tin octoate.
• The evaporation of by-products(alcohols)….
condensation reaction….shrinkage of material….
poor dimensional stability.
• Impression should be poured soon after removal from
the mouth.

Advantages:-
1. Short setting time in mouth(6-8min.) than polysulfides
2. Less affected by high operating temperatures &
humidity.
3. Pleasant to use… better patient acceptability.
Disadvantages:-
1. Poor wetting characteristics…extremely hydrophobic.
So, prepared teeth & gingival sulcus… completely
free of moisture… a defect free impression.
2. Pouring without trapping air bubbles is difficult & a
surfactant may be needed.
3. Limited shelf life… instability of alkyl silicates in
presence of organo-tin compounds…oxidation of
tin.

POLYETHER
• Developed in Germany in the mid 1960’s.
• Cure through cross-linking of a difunctional epimine
terminated prepolymer catalyzed by an alkyl benzene
sulfonate catalyst.
• No volatile by-product formed…excellent
dimensional stability.
• Polymerization shrinkage – low compared with
most room temperature cured polymer systems.

• A study conducted by Mansfield and Wilson
showed its thermal expansion greater than
that of polysulphide.
• High dimensional stability - so accurate casts
can be poured within one week after removal
from the mouth
• Stable only if stored dry…affinity for water…
significant dimensional change.

Advantages:-
1. Short setting time in mouth(about 5min.).
2. Dimensional accuracy.
3. Automix available.
Disadvantages:-
1. Stiffness of set material… causes problems when
separating a stone cast from the impression.
2. Short working time.
3. Cases of allergic hypersensitivity to polyether
elastomers were reported by Nally and Storrs. It
manifested as sudden onset of burning, itching and
general oral discomfort.

ADDITION SILICONE
• Introduced as a dental impression material in the
1970’s.
• Also known as polyvinyl siloxane.
• Supplied as 2 pastes:-
Base paste:- silicone with terminal silane hydrogen
group & an inert filler.
Catalyst paste:- silicone with terminal vinyl groups,
chloroplatinic acid catalyst & a filler.
• No by-product formed – stable material.

• Excellent dimensional accuracy & long term
dimensional stability…. least affected by pouring
delays, or by second pours, & is still accurate even
when poured 1 week after removal from the mouth.
• Study conducted by Dhuru et al(1986) showed
release of hydrogen gas from the impression
surface….. voids in the surface of the setting stone
cast(pour within 15min. or after 24hours).
• Newer materials contain Palladium as hydrogen
absorber…. poured after 15-30min.

• Hydrophobic…. surfactant incorporated….less
hydrophobic & easy to pour.
Disadvantage:-
- Slightly less accurate casts with surface softer than
those poured in conventional polyvinyl siloxanes.
- Incorporated surfactant…. makes electroplating
difficult.
- Makes impression material more sensitive to
retardant action of sulfur.
• If putty is used, should not be mixed wearing latex
gloves…. setting of the material impeded…. sulfur
derivatives in latex.

Advantages:-
1. Dimensional stability.
2. Pleasant to use.
3. Short setting time.
4. Automix available.
Disadvantages:-
1. Hydrophobic
2. Poor wetting
3. Some materials release H2.
4. Hydrophilic formulations imbibe moisture.
Precautions:-
1. Avoid bubbles when pouring.

POLYETHER URETHANE
DIMETHYLACRYLATE
• They are photo initiated elastomers.
• Marketed by Densply & introduced in late 1980’s.
• Discontinued because of problems with surface
polymersation.
• It is polyether urethane dimethylacrylate resin with a
diketone initiator, an amine accelerator & 40%-60%
silica filler.
• Used in a clear tray & is photo initiated by 400-500nm
wavelength blue light creating unlimited working time
coupled with a short setting time.

IMPRESSION TECHNIQUES
• There are 2 types of trays used for making
impressions:-
1. Stock Trays
2. Custom Trays
• With any system, tray rigidity is important, because
even slight flexing of the tray will lead to a distorted
impression.
• Errors are undetectable until attempts are made to
seat the restoration.
• Therefore, thin, disposable plastic trays are
unacceptable.
• Resin thickness of 2-3mm are needed for adequate
rigidity. www.indiandentalacademy.com

Methods of impression making using stock
trays:-
- Putty wash double mix.
- Putty wash single mix.
Advantages:-(stock tray)
1. Eliminates time and expense of fabricating custom
tray.
2. Metal stock trays are rigid and are not susceptible to
distortion.
Disadvantages:-
1. More impression material is required.
2. Metal trays must be sterilized.

Putty Wash Double Mix:-
1. Coat the tray with tray adhesive 15min. prior…
2. Mix high – viscosity putty according to manufacturer’s
instruction.
3. Roll putty into elongated cylinder.
4. Insert it into the stock impression tray.
5. Cover putty with a sheet of polyethylene spacer.
6. Insert and seat the tray with a rocking type motion.
7. Hold and wait until initial set(approx. 2min.).
8. Remove it from the mouth with minimal sideward
movement and peel off the spacer.

9. Remove excess impression material with a sharp
knife.
10. Isolate the area to be impressed with cotton rolls
and dry preparation with short bursts of
compressed air.
11. Retract the gingival tissue with the help of gingival
retraction cord.
12. Mix low-viscosity impression material according to
manufacturer’s instructions.
13. Load the syringe by holding it at a slight angle while
scrapping the pad.
14. Grasp 2 mm excess of cord with forceps & slowly
tease the top cord towards the occlusal.

15. Quickly blow away seepage with short bursts of
compressed air or dry with cotton pledgets.
16. Syringe inaccessible areas first e.g.., Distolingual
finish line.
17. Insert the low-viscosity impression material into the
tray without overfilling the tray.
18. Position the tray over the arch.
19. Seat from posterior to anterior, allowing the excess
to extrude anteriorly.
20. Apply force in a vertical direction until further seating
is impossible
21. Evaluate final position and adjust tray quickly
if necessary.

22. Stabilize the tray and wait till final setting
23. Remove the tray parallel to the preparation (s) path
of withdrawal.
24. Rinse impression and dry with short, small bursts of
compressed air.
25. Elastomeric material should be present 0.5mm
beyond visible finish line.
26. There should be no tray show-through in any areas
of the impression except at tissue stops.
27. Pour the impression with die stone.

Putty wash double mix technique

Putty Wash Single Mix:-
1. Same as the putty wash double mix method,
except for the use of polyethylene spacer.
retraction cord.
3. Putty and light-bodied materials are mixed at same
time.
4. Putty material is put onto the stock tray and syringe
material is loaded in the syringe.
5. Remove the gingival retraction cord.
6. Blow dry the area with compressed air & syringe
the low-viscosity material on the preparations.
7. Position the tray over the arch.
8. Wait till it sets.

Putty wash single mix technique

Methods of impression making using custom trays:
Advantages:-(custom tray)
1. Less impression material is needed than with stock
tray.
2. Because the trays are used only once, sterilization
is not a problem.
3. A uniform thickness of impression material
minimizes distortion resulting from curing
shrinkage.
4. Precuring of the tray material is not required.
Disadvantages:-
1. Construction of the custom tray is time consuming.
2. The tray must be made 24 hours prior to minimize
further distortion.
3. The monomer may be a sensitizer for some
personnel. www.indiandentalacademy.com

Heavy Body Light Body Combination:-

Single Mix Technique:-
- Only one mix is used to load the syringe & fill the
tray.
- Paste is mixed, part of it is loaded on to the tray &
the remaining onto the syringe.
- Syringe material is injected onto the prepared area
& tray material is seated over it.

Automix Technique:-
1. Impression material is supplied in prepackaged
cartridges with a disposable mixing tip attached.
2. The cartridge is inserted in a gunlike device, & the
base & catalyst are extruded into the mixing tip,
where mixing occurs as they progress to the end of
the tube.
3. The homogeneously incorporated material can be
directly placed on the prepared tooth & impression
tray.
4. Advantage:- Elimination of hand mixing.
A study conducted by Chong et al showed that
elimination of hand mixing on pad produce fewer
voids in the impression.

Machine Mixing Technique:-
- An alternate method for improving mixing is to use
a machine mixer.
- Convenient & produces void-free impressions.

Pin-retained Restorations:-
- Elastomeric impression materials are strong enough
to reproduce a pinhole without tearing.
- To avoid bubbles, they must be introduced carefully
into pinhole with a lentulo or cement tube.
- With reversible hydrocolloid, a special nylon bristle
must be used for the impression.

r
Procedure:-
1. Apply separating medium, e.g. die lubricant to the
pinholes & displace tissue.
2. Mix light-bodied impression material.
Cement tube:-
- Fill the tube & squeeze small amount of material
into each pinhole. No air should be trapped in the
base of the pinhole.

Lentulo:-
- Pick up a small quantity of impression material &
spiral the material into the pinholes, rotating slowly
while moving the lentulo along the side of the pinhole.
Prefabricated plastic pins:-
- Elastomer bristles, used to register the pinholes can
be modified with a scalpel to eliminate inaccuracy
relating to fit. Length should be adjusted so that they
do not contact the impression tray. Place the bristle &
complete impression.www.indiandentalacademy.com

Impression Technique for Post & Core:-
• Elastomeric materials can be used to make
impressions of the post space when
endodontically treated teeth are being restored.
• The impression should be reinforced with a plastic
pin or orthodontic wire.

Direct Procedure:-
1. Lightly lubricate the canal & notch a loose fitting
plastic dowel that extends to the full depth of the
prepared canal.
2. Use bead-brush technique to add resin to the dowel
& seat it in the prepared canal. Mix some resin &
roll it into a thin cylinder & place it into the canal &
push with the monomer moistened plastic dowel.
3. Do not allow the resin to harden fully within the
canal. Loosen & reseat it several times while its
rubbery.
4. Once polymerized, remove the pattern.
5. Once the pattern is made, additional resin is added
for the core.

Indirect Procedure:-
1. Cut pieces of orthodontic wire to length & shape
them like letter “J”.
2. The wire should fit loosely & extend to the full depth
of the post space.
3. Coat the wire with tray adhesive.
4. Using lentulo spiral, fill the canal with elastomeric
impression material.
5. Seat the wire reinforcement to the full depth of post
space, syringe more impression material around
the prepared teeth, & insert the impression tray.
6. Remove the impression & pour cast.www.indiandentalacademy.com

Copper Band Impressions:-
The copper tube or band is used to salvage
an impression of multiple preparations
when there are only vague margins on one
or two preparations that are not adequately
replicated in the impression

Procedure:-
1. Select copper band diameter by trial and error by
deforming the tubes to semiellipsoidal cross
section and trying in.
2. Anneal selected tube by heating in flame and
quenching in alcohol.
3. Cut with scissors and smoothen rough edges with
carborundum stone.
4. Evaluate fit, band should extend approximately
1mm beyond finish line and produce minimal
tissue blanching
5. Cut orientation hole in top one-fifth of facial surface
of tube.
6. Make compound plug on top one-third of facial
surface of tube.

7. Seat and orient band onto preparation. The
compound placed on top should just touch occlusal
surface.
8. Cool the tube with water and remove it from the
mouth using Backus towel clamp.
9. Using a long shank round carbide bur, drill a hole
through the center of the compound plug.
10. Cut approximately 4-5 evenly distributed holes
2-3mm above the bottom of the copper tube.
11. Coat the internal surface with adhesive.
12. Clean and isolate preparation.
13. Seat the copper band on the prepared tooth. Inject
the Elastomeric material into the copper band.

14. Position fingers on top edge of band; orient and
seat customized copper tube.
15. Evaluate tube position; if incorrect, reposition.
16. Stabilize band and compress excess into plug’s
hole with lubricated finger.
17. Remove the finger; protect copper band from
movement and await final set.
18. Grasp top one-fifth of impression with sharp
Backus towel clamp and gentle remove from
tooth.
19. Evaluate the impression and pour a die.

Closed Bite Double Arch Method:-
1. The articulator should have a vertical stop such as an
incisal pin or other metal-to-metal contact.
2. There should be sufficient space distal to the terminal
tooth in the arch to allow tray approximation.
Advantages:-
1. The physical deformation of the mandible during
opening is minimized.
2. The shifting of teeth occuring during maximum
intercuspation is captured.
3. Less elastomeric impression material is needed so
the patient is more comfortable.
4. Less gagging may occur.

Disadvantages:-
1. Tray is not rigid, depends on impression material
for rigidity.
2. Is not a functionally generated technique, so it is
limited to one casting per quadrant.
3. The distribution of the impression material is not
uniform.

Procedure:-
1. Evaluate the fit of the tray in patient’s mouth &
position the tray’s crossbar distal to last tooth in arch.
retraction cord.
3. Mix low-viscosity impression material according to
manufacturer’s instructions.
4. Load the syringe by holding it at a slight angle while
scrapping the pad.
5. Grasp 2 mm excess of cord with forceps & slowly
tease the top cord towards the occlusal.

6. Quickly blow away seepage with short bursts of
compressed air or dry with cotton pledgets.
7. Syringe inaccessible areas first e.g.., Distolingual
finish line.
8. Mix high-viscosity elastomer & “overfill” bilaterally.
9. Manually seat the tray on maxillary arch.
10. For quadrant trays, position the crossbar distal to
the last tooth in the arch.
11. Instruct patient to slowly close mouth.
12. Evaluate complete closure by observing the
interdigitation on the opposite arch.

13. Once the material is set, place a finger on either
side of the tray & remove with equal pressure
bilaterally to minimize distortion of the tray.
14. Rinse impression and dry with short, small bursts of
compressed air.
15. Pour the impression with die stone.

Impression Technique for Reversible
Hydrocolloid:-
Step by step procedure:-
1. Select the correct size of water-cooled impression
tray.
2. Place small modeling compound or prefabricated
stops (tripod fashion) in the tray to prevent over
seating.
3. Displace the gingival tissues with the help ofwww.indiandentalacademy.com

4. Fill the impression tray with heavy-bodied material
from the storage bath wash hydrocolloid. Squeeze
some onto the tray material & submerge the tray in a
tempering bath. Load the syringe and replace it in the
storage tank.
5. Remove the cord from the sulcus, flood the sulcus
with warm water, and inject the light- bodied
impression material over the entire surface of the
prepared tooth.

6. Remove the impression tray from the tempering
tank, wipe off the surface layer with a gauze piece
and place it in the patient’s mouth.
7. After seating, cold water is circulated through the
tray until the impression material is completely set.
(5-6min.)
8. Hold the tray firmly in the patient’s mouth while the
impression material is setting.
9. Remove the tray with a rapid motion, wash it with
cold water, disinfect it, immerse it in 2%potassium
sulfate solution.
10. Pour immediately with type IV or V stone.www.indiandentalacademy.com

LAMINATE TECHNIQUE
• This technique combining reversible and irreversible
hydrocolloid was described in 1951 by Schwartz.
• Modified reversible hydrocolloid that could bond to
alginate was introduced in late 1970’s.
• Alginate in the tray, mixed with water at 700
F, cools
the reversible hydrocolloid that has been injected
around the prepared tooth, causing it to solidify.

Advantages:-
1. No need for water-jacketed trays and tubing.
2. Impression is removed from mouth faster than
other elastic materials.
3. Less expensive.
Disadvantages:-
1. Fast gelation time of syringe material, which
requires the impression to be handled very
quickly.
2. Sometimes syringe material separates from the
alginate in the tray.

DISINFECTION
• Dental professionals are exposed to a wide variety of
microorganisms that exist in saliva & blood, as they
directly deal with the oral cavity which houses these
microorganisms that can cause infectious diseases.

CONCLUSION
Making impressions from prepared hard tooth
substances requires a selective approach. A suitable
procedure should be selected for each impression
task according to the clinical situation. Impression
materials & methods available today offer excellent
results in terms of material characteristics. It is only
the general clinical circumstances which limit the
realisation of what is technically possible on the
patient.

REFERENCES
1. Drannon D.G. – “The accuracy & efficiency of disinfection by
spray atomization on elastomeric materials. JPD
1989;61:610-612.
2. Johnston J.F,Phillips R.W.- “Modern practice in fixed
prosthodontics.4th
edi.Philadelphia,Saunders co.
3. Linke B.A., Nicholls J.I. – “Distortion analysis of stone casts
made from impression materials”. JPD 1985;54:794-802.
4. Malone W.F.P,Koth D.L. – “ Tylman’s theory & practice of
fixed prosthodontics.” 8th
edi. 1997.
5. Millar B.J., Dunne S.M. – “ In vitro study of the number of
surface defects in monophase & two-phase addition silicone
impressions.” JPD 1998;80:32-35.
6. Pratten D.H., Craig R.G. – “ Wettability of a hydrophilic
addition silicone impression material.” JPD 1989;61:197-202.
7. Rosenstiel S.F., Land M.F. – “ Contemporary fixed
prosthodontics” 3rd
edi. 2001.
8. Shillingburg H.T. – “Fundamentals of fixed Prosthodontics.”
3r edi.quintessence pub.co
9. Tjan A.H.L., Nemetz H., - “ Effects of tray space on the
accuracy of monophasic polyvinylsiloxane impressions.”
JPD 1992;68:19-28. www.indiandentalacademy.com

Impression materials and techniques in fpd /orthodontic courses by Indian dental academy

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Viewers also liked

Viewers also liked (8)

Similar to Impression materials and techniques in fpd /orthodontic courses by Indian dental academy

Similar to Impression materials and techniques in fpd /orthodontic courses by Indian dental academy (20)

More from Indian dental academy

More from Indian dental academy (20)

Recently uploaded

Recently uploaded (20)

Impression materials and techniques in fpd /orthodontic courses by Indian dental academy