Impression tray and
impression technique
Dr. Nora Sheta
Clinical
Laboratory
1. Examination & Diagnosis
2. Primary impression

3. Final impression

4a. Jaw relation registration
4b. Selection of artificial teeth

5. Try in
Processing
6. Insertion
7. Post insertion care
Study cast
 Special tray
Boxing and pouring  master cast
 Occlusion blocks
Mounting on articulator
 Setting of artificial teeth and
waxing up
IMPRESSION TRAYS AND IMPRESSION
TECHNIQUES
IMPRESSION
An impression is a negative record or imprint of the tissues of the
oral cavity that forms the basal seat of the denture.
Reproduce a positive form and shape of the same oral tissues (Cast) .
IMPRESSION TRAYS
“A tray is an instrument used to carry the impression material to the mouth ,
holding it in position against tissues until the material hardens ,it helps
in removing the impression from the mouth “.
Parts
1 . Body
Body
2 . Handle
Body
Handle
Handle
EDENTULOUS TRAY
DENTULOUS TRAY
Body
Floor
Flat
Flange
Long
Dentulous Tray
Handle
Straight
Floor
Round
Flange
Short
Body
Edentulous Tray
Handle
L - Shape
Types of Trays
I- Stock trays
II- Custom trays
(Special, Individual trays)
Impression tray



is composed of
Body: The body
consists of a floor
and flanges.
Handle.
The body and handle are designed
to suit different mouths
1-Dentulous mouth cases
.
2-Edentulous mouth cases
.
3-Partially edentulous
mouth cases.
types Stock tray

Perforated or non
perforated
 Metal or plastic

Preliminary Impression
USES
Study cast
As a study cast to study :
1. Ridge shape .
2. Palatal Vault shape .
3. Denture bearing areas .
4. Areas of undercut .
5. Relief areas .
6. Posterior palatal seal area .
7. Sharp bony edges .
8. Depth of the sulcus .
9. Inter-ridge space
10. Inter-ridge relations .
As a cast on which the final impression
tray is fabricated.
SPECIAL OR INDIVIDUAL TRAYS
TYPES
1. Shellac base plates .
2. Self & light curing acrylic resin .
3. Cast or swaged metal .
Advantages of Special Trays
1 . Fit more accurately the individual arch of the patient.
2 . Bulk of the impression material is reduced .
4 . More accurate border contour
5 . Less impression material is used .
6. More comfortable to the patient .
Types of special trays
1- Shellac base plate special tray
2- Acrylic resin custom (special) trays:
a- cold cured
b- heat cured
c- light cured
Both heat and cold cured are used widely now. It is
rigid and light in weight, not wrap in the mouth .
3- Cast or swaged metal tray
4- Vacuum formed plastic sheets
It needs a pressure forming machine
Comparison between shellac and
acrylic resin custom trays
• Shellac base plate
special tray
1. Low strength.
2. Easily distorted by load
and temperature.
3. Improper adaptation to
the cast
4. Easily constructed
Self-cured acrylic
resin special tray
1. Higher strength and rigidity.
2. Not distorted by temperature.
3. Well adapted
4. Easily constructed
1- with a spacer
2- without a spacer
Tray can be
“
One thickness of
modeling
wax
or
shellac base plate
adapted on the study
cast
under
the
special tray “
SHIM OR SPACER
Upper & Lower spacer (Shim)
(Shim)
Steps for fabrication upper tray
Custom Tray With Spacer
(Shim)
Steps for fabrication lower tray
1
2
3
4
6
5
7
8
9
FINAL IMPRESSION TECHNIQUES
OR THEORIES
1 . Minimal Pressure Impression Technique (Mucostatic
Impression Technique) .
2 . Definite Pressure Impression Technique or Mucocompression
Impression or Functional Impression Technique .
3 . Selective Pressure Impression Technique .
2NDRY IMPRESSION
TECHNIQUES
(1) IMPRESSION
TECHNIQUE
MINIMAL PRESSURE
( MUCOSTATIC)
FUNCTIONAL PRESSURE
(MUCOCOMPRESSIVE)
SELECTIVE PRESSURE
(2) PHILOSOPHY
ALL THE TISSUES ARE UNDER
THE LEAST PRESSURE.
ALL THE TISSUES ARE UNDER
FUNCTIONAL PRESSURE.
TISSUES THAT CAN WITHSTAND PRESSURE ARE LOADED. AND TISSUES THAT
CAN'T ARE RELIEVED.
(3) TRAY
PERFORATED + ON SPACER +
WITH TISSUE STOPS.
WELL ADAPTED + NO SPACER +
WAXRIM.
STOCK TRAY WITH COMPOUND ,THEN IT IS RELIEVED AND WASHED WITH
PLASTER IMPRESSION MATERIAL.
(4) PRESSURE
FINGER PRESSURE
PATIENTS BITING FORCE.
FINGER PRESSURE.
(5) IMPRESSION
MATERIAL
PLASTER, FLOWY MATERIAL.
ZnO/E , HEAVY MATERIAL
IMPRESSION COMPOUND (HEAVY)+ PLASTER OR ZnO/E(FLOWY)
CLINICAL
5 Final Impression .
Upper Impression
Lower Impression
Boxing the impression
An impression is boxed to preserve the borders of
the impression so that it will be accurately
reproduced in the cast.
Methods for boxing
1- Wax method
2- Plaster and Pumice method
Beading wax for boxing
1- Wax Method
1-wax method
1-wax method
Lower impression
2-Plaster and Pumice method
Plaster and pumice for boxing
2-Plaster and Pumice method
Upper impression
BOXING
ADVANTAGES OF BOXING
1 . The borders of the impression are preserved
2 . The thickness of the base of the cast can be controlled
3 . Permits vibrating the stone material into the impression
4 . Time is conserved
5 . Material are conserved
MASTER CASTS