1. Impression tray and impression technique
Dr. Nora Sheta

2. 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

3. 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) .

4. IMPRESSION TRAYS Parts 2 . Handle Dentulous Tray Edentulous Tray
“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
2 . Handle
Body
Body
Handle
Handle
DENTULOUS TRAY
EDENTULOUS TRAY
Floor
Flat
Body
Flange
Long
Dentulous Tray
Handle
Straight
Floor
Round
Body
Edentulous Tray
Flange
Short
Handle
L - Shape

5. Types of Trays
I- Stock trays II- Custom trays (Special, Individual trays)

6. Impression tray is composed of
Body: The body consists of a floor and flanges.
Handle.

7. The body and handle are designed to suit different mouths
1-Dentulous mouth cases .
2-Edentulous mouth cases
3-Partially edentulous mouth cases.

8. types Stock tray
Perforated or non perforated
Metal or plastic

9. 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.

11. 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 .

12. 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

13. 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

14. 1- with a spacer 2- without a spacer
Tray can be

15. “ One thickness of modeling wax or shellac base plate adapted on the study cast under the special tray “
SHIM OR SPACER

16. Upper & Lower spacer (Shim)

17. Custom (Special) trays with spacer (Shim) Steps for fabrication upper tray

18. Custom Tray With Spacer

19. Custom (Special) trays with spacer (Shim) Steps for fabrication lower tray

20. 1 2 3

21. 4 5 6 7

22. 8 9

23. 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 .

24. 2NDRY IMPRESSION TECHNIQUES
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)

25. CLINICAL
5 Final Impression .
Upper Impression
Lower Impression

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

27. Methods for boxing
1- Wax method 2- Plaster and Pumice method

28. Beading wax for boxing 1- Wax Method

29. 1-wax method

30. 1-wax method Lower impression

31. 2-Plaster and Pumice method Plaster and pumice for boxing

32. 2-Plaster and Pumice method Upper impression

33. BOXING

35. ADVANTAGES OF BOXING MASTER CASTS
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