PRiMARY IMPRESSION

PRiMARY IMPRESSION:its anegative likeness of the denture bearing tissues. It should be :* *overextended A ll anatomical landmarks and soft tissue recorded* Static* *Taken by stock –tray *No distoration *No larg voids

REQUIERMENTS: STOCK TRAY: *RIGID *SIZE & SHAPE *BORDER EXTENSION *RETAIN ITS SHAPE

Definition and classification Impression trays TYPES OF STOCK TRAY Definition and classification

Impression tray It is a device used to carry ,confine & control impression material while making an impression

Parts of the tray floor flanges handle 1- Body: which consist of : a) floor. b) flanges. 2- Handel.

Classification of trays Based on whether they are prefabricated or individualized 1- prefabricated Stock tray: used for primary impression procedure. Perforated trays Non perforated trays Rim lock trays 2- individualized Special tray/ custom try which is used for final impression procedure. Close fitting special try Loss fitting or spacer special try

STOCK TRAY Based on shape of stock trays: 1- Stock tray for dentulous patient (Square). 2- Stock tray for edentulous patient (oval). We can distinguish between them by: stock trays for dentulous patient have long flanges, wide and flat floor, while the other have short flanges, oval and narrow floor. 3-Tray with combination flat and oval floor are suitable for partial denture work. aa

Based on material used for fabrication a) metallic. b) Non- metallic. Material used for fabrication stock Tray 1- metal Tin-lead alloy Stainless steel 2- plastic

TRAY SELECTION 1-3-5MM OF clearance with soft tissues 2-maxillary trays should extend slightly beyond viberating line 3-mandibular trays should cover the retro molar pads 4-trays can be modified with wax or compound to extend the tray desired

IMPRESSION MATERIAL FOR PRiMARY IMPRESSION 1-ALGINATE-IRREVERSIBLE HYDROCOLLOIED 2-IMPRESSION COMPOUND 3-ELASTOMER 4-IMPRESSION PLASTER PATIENT PREPARATION BEFOR THE IMPRESSION 1-CORRECT POSITION OF THE DENTAL CHAIR & PATIENT 2-DRY THE MUCOSA 3-DON’T LeT Patient CLOSE

TAKING THE IMPRESSION FIND THE CORRECT POSITION OF THE DENTAL CHAIR &PATIENT SUPPORT the tray during seting DON’T leve the patient movement CAUSES DISTORATION Important constraction to accurate impression 1- 2-4 mm bulk material in tray 2- snap action removal from mouth 3-allow extra 1-2 minutes after setting to improve tear strength 4-stored in moist environment to avoid loss of water evaporation &deformation 5-disinfect in less than 10 minutes to avoid dimentional instability

CAST Cast:_:the cast is appositive likeness of the denture bearing tissues Primary cast:made according to primary impression special tray is constracted on to it Pouring acast Cast should be aminimum of 12mm in thinnest part Sparate the alginate impression from the cast after 45 minutes

TRIMMING CASTS Trim the base on the model trimmer parallel to the residual ridges Leave the vestibular reflection intact for making aspacial\custom tray