Impression tray and impression technique

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Impression tray and impression technique

• Dr. Nora Sheta

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Steps of Complete Denture Construction
Clinical Laboratory
1. Examination Diagnosis
2. Primary impression Study cast Special tray
3. Final impression Boxing and pouring ? master cast Occlusion blocks
4a. Jaw relation registration 4b. Selection of artificial teeth Mounting on articulator Setting of artificial teeth and waxing up
5. Try in Processing
6. Insertion
7. Post insertion care
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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) .
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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
Floor
Flat
Body
Flange
Long
Dentulous Tray
Handle
Straight
Floor
Round
Body
Edentulous Tray
Flange
Short
Handle
L - Shape
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Types of Trays

• I- Stock trays
• II- Custom trays
• (Special, Individual trays)

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Impression tray

• is composed of
• Body The body consists of a floor and flanges.
• Handle.

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The body and handle are designed to suit
different mouths

• 1-Dentulous mouth cases
• .
• 2-Edentulous mouth cases
• .
• 3-Partially edentulous mouth cases.

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types Stock tray

• Perforated or non perforated
• Metal or plastic

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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.
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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 .
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• 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

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Comparison between shellac and acrylic resin
custom trays

• Shellac base plate special tray
• Low strength.
• 2. Easily distorted by load and temperature.
• 3. Improper adaptation to the cast
• 4. Easily constructed

Self-cured acrylic resin special tray

• Higher strength and rigidity.
• Not distorted by temperature.
• Well adapted
• 4. Easily constructed

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Tray can be

• 1- with a spacer
• 2- without a spacer

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SHIM OR SPACER

• One thickness of modeling wax or shellac base
  plate adapted on the study cast under the special
  tray

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Upper Lower spacer (Shim)
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Custom (Special) trays with spacer (Shim)Steps
for fabrication upper tray
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Custom Tray With Spacer
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Custom (Special) trays with spacer (Shim)Steps
for fabrication lower tray
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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 .
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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)
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CLINICAL
5 Final Impression .
Upper Impression
Lower Impression
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Boxing the impression

• An impression is boxed to preserve the
  borders of the impression so that it will be
  accurately reproduced in the cast.

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Methods for boxing

• 1- Wax method
• 2- Plaster and Pumice method

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Beading wax for boxing1- Wax Method
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1-wax method
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1-wax method Lower impression
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2-Plaster and Pumice method Plaster and pumice
for boxing
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2-Plaster and Pumice methodUpper impression
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BOXING
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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