Impression tray and impression technique Dr. Nora Sheta

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

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 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

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 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

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)

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

Custom Tray With Spacer

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 .

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)

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 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