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1. IMPRESSIONS MAKING IN FIXED
PARTIAL DENTURE

2. INTRODUCTION
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IMPRESSION : An impression is a negative likeliness of the
teeth and surrounding structures.
A good quality impression is only obtained
when we have a thorough knowledge of
materials, their properties, and techniques
for their best manipulation

3. IMPRESSION TRAY
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It is a receptacle into which suitable impression material
is placed to make a negative likeliness (or) a device that is
used to carry, confine and control impression material
while making impression - GPT 9

4. REQUIREMENTS OF CUSTOM TRAY
• Rigid
• Stops on the occlusal surfaces of the teeth to orient the tray
properly when it is seated in the mouth
• Impression material should adhere firmly to tray – rubber
adhesive is used.
• Beside this
–Perforation
–Roughening the inner surface of tray
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5. CUSTOM TRAY
Improves accuracy – limits volume of material
Reduces stress during removal & thermal contraction
Tray rigidity is important
Resin thickness of 2 – 3mm
Clearance of 2 – 3 mm
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6. CHALLENGES IN MAKING GOOD IMPRESSION
 Moisture control
• Saliva
• Blood
• Gingival tissue must be displaced laterally to allow access & provide space
for the material
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7. IMPRESSION MATERIALS USED IN FPD
1) Hydrocolloid impression material
a) Reversible
b) Irreversible
2) Elastomeric impression materials
a) Polysulfide
b) Addition silicone
c) Condensation silicone
d) Polyether
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8. According to Viscosity they are classified as
1. Light body/ Syringe consistency
2. Medium body/ Regular body
3. Heavy body/ Tray consistency
4. Very heavy body/ Putty consistency
ELASTOMERS
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9. IMPRESSION TECHNIQUES
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IMPRESSION
TECHNIQUES
1. Stock tray technique
Double mix
Single mix
2. Custom tray technique
3. Double arch technique
4. Copper band technique
5. Reversible hydrocolloid
Laminate
technique
Wet field
technique
6. Matrix system

10. IMPRESSION MATERIALS
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Wettability
Viscosity
Cost
Which
material to
choose

11. STOCK TRAY IMPRESSION TECHNIQUE
(Putty wash technique)
Mixing method : Double mix
Single mix
Procedure:
 Tray selection is done
 Coat the tray with adhesive on inside & rim
 Mix high viscosity putty according to
manufacturer’s instruction
 Adapt it into the stock tray
 Cover putty with manufacturer’s spacer(a sheet of polyethylene)
 Hold & wait until initial set
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12. ADAPTATION OF POLYETHLENE SPACER
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13. PUTTY WASH IMPRESSION TECHNIQUE
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 Remove the putty impression from mouth with minimal sideward
movement
 Light body is immediately injected into the sulcus & around
prepared teeth
 Tray is seated slowly until it is firmly in place for 6 minutes
 As the impression is set, its removed as quickly and in as straight a
path as possible to prevent plastic deformation of the material
 Impression is rinsed to remove blood & saliva, blown dry,
inspected, disinfected and poured

14. SINGLE MIX TECHNIQUE
 Mix the low viscosity impression material & load it into
syringe / take syringe material (light body)
 Syringe in inaccessible areas first
 Load the tray with putty material
 Seat the tray
 After final set remove the tray parallel to the preparation path
 Impression is evaluated for finish lines & for any distortion &
tear
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15. SINGLE MIX TECHNIQUE
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Stock tray is coated with tray
adhesive
Light body is injected around
Prepared tooth
Heavy body is loaded in stock tray
Space is created in putty and
Light body is injected
Tray seated in patient’s mouth Final impression

16. DOUBLE MIX TECHNIQUE
 For the stock tray double mix insert the low viscosity impression
material into the tray without overfilling it
 Position the tray over the arch
 Evaluate final position & adjust tray quickly if necessary
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17. Prepared teeth
After applying tray adhesive
Putty is loaded in stock tray
Putty impression is
made
Space is created for
light body
Light body is injected around
the prepared tooth & the
impression is reaseated
Final impression
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18. DUAL-ARCH IMPRESSIONS
use of only one tray –
• Captures an impression of the prepared tooth, the adjacent and
opposing teeth
• And the relationship between them in maximal intercuspation
without the need for an interocclusal record
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19. DUAL IMPRESSION TECHNIQUE
Indication
– single tooth with intact adjacent
and opposing teeth
– intact, mutually protected Angle‘s Class I
occlusion
• Low-viscosity impression material is injected
around prepared tooth
• High-viscosity material into the tray
• Tray is inserted immediately
• Maximal interocclusion is checked
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20. DUAL IMPRESSION TECHNIQUE
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ADVANTAGES:
 Physical deformation of mandible is minimal
 Shifting of teeth occuring during maximum intercuspation is captured
 Less impression material is needed
 Less gagging
DISADVANTAGES:
 Tray is not rigid
 Limited to one quadrant
 Distribution of impression material is not uniform

21. COPPER BAND OR TUBE METHOD
 The copper band is used to salvage an impression of multiple
preparation where there is only vague margins on one or two
preparation that are not adequately replicated in the impression
FITTING OF COPPER BAND TO PREPARATION:
 A copper band is selected & annealed by heating on a flame &
quenching in alcohol
 Mark the finish line with explorer & round off the edges
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22.  Evaluate the fit & cut orientation hole in top one fifth of the facial surface
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23. EVALUATING THE FIT OF COPPER BAND:
 The circumference of the copper band must be such that it will fit over the
preparation and still project into the gingival crevice.
 An oversize band should not be used since it will impinge on the gingival
tissues
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24. PROCEDURE:
 Make 4 to 5 holes evenly distributed above the bottom of the copper tube
for retention of the impression material
 Coat the internal surface sparingly with adhesive
 Clean and isolate the preparation
 Mix heavy viscosity material & inject to the band & position it on the tooth
 Once the material is set remove the band & inspect the impression
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25. REVERSIBLE HYDROCOLLOID TECHNIQUE
This impression requires a special conditioning unit which consists of 3
thermostatically controlled water baths.
1. A liquefaction bath
2. A storage bath
3. A tempering bath
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26. 26

27. PROCEDURE:
 Select the correct size of water cooled impression trays
 Place a small modelling compound or pre fabricated stops in the
tray to prevent over seating
 Fill the impression tray with heavy bodied material from the
storage bath & place it in the tempering bath
 Load the syringe material in the syringe & replace it in the storage
bath
 Carefully remove the retraction cord and flood the tooth with water
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28.  Inject the syringe material on the tooth
 Remove impression tray from the bath , wipe with the gauze &
place it in the mouth
 After seating cold water is circulated through the tray until the
impression material is set
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29. Laminate Technique or Agar Alginate combination
technique
 After injecting the syringe agar on to the area to be recorded, an
impression tray containing a mix of chilled alginate that will
bond with the syringe agar is positioned on it
 Alginate gels by chemical reaction & agar gels by means of
contact with cool alginate rather than the water circulating
through the tray
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30. ADVANTAGES:
 Less air bubbles
 Water cooled trays are not required
 It sets faster than regular agar technique
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31. Wet Field Technique
 Popular & relatively new technique
 Areas to be recorded are actually flooded with warm water
 Then the syringe material is introduced quickly, liberally & in bulk
to cover the occlusal and / incisor areas only
 While the syringe material is still liquid, the tray material is seated
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32. Wet Field Technique
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 The hydraulic pressure of the
viscous tray material forces the fluid
syringe hydrocolloid down into the
areas to be recorded
 This motion displaces the
syringe materials as well as blood
and debris throughout the sulcus

33. MATRIX IMPRESSION SYSTEM
This system uses three impression materials
1. Matrix impression material
2. Tray impression material
3. Matrix forming material
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34. Tooth preparation Clear plastic template selected
Matrix is made in carrier with PVS material before soft tissue is retracted
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35. Impression syringe is used to
fill matrix with high viscosity material
Matrix impression is seated with
light pressure
Stock tray filled with medium viscosity impression material is seated over matrix impression
before matrix material polymerizes
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