Impression procedures

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<ul><li>1.By:AhmedAliAbbas </li></ul> <p>2. INTRODUCTION An impression is defined as a negative likeness of the teeth and/or edentulous areas where the teeth have been removed, made in a plastic material which becomes relatively hard while in contact with these tissues 3. MATERIALS AVAILABLE FOR MAKING IMPRESSION Reversible hydrocolloids (agar-agar) Irreversible hydrocolloids (Alginate) Elastomeric impression materials 4. STEPS IN IMPRESSION MAKING Position of patient &amp; dentist Tray selection Mixing the material &amp; loading into the tray Impression making &amp; removal Inspecting, cleaning &amp; disinfecting the impression 5. POSITION OF PATIENT &amp; DENTIST Dentist should stand &amp; patient should sit upright Occlusal plane should be parallel to the floor MAXILLARY IMPRESSION- dentist should stand at the right rear of the patient MANDIBULAR IMPRESSION- dentist should stand at the right front of the patient 6. Mandibular impressionMaxillary impression 7. IMPRESSION TRAY SELECTION Stock trays for dentulous &amp; partially edentulous arches are of 3 types: Rimlock trays Perforated metal trays Plastic disposable trays 8. MIXING IMPRESSION MATERIAL Bowel Spatula Scoop and Measuring jar 9. REMOVAL OF IMPRESSION FROM MOUTH Clinically the initial set of alginate is determined by loss of surface tackiness Release seal by retracting lips &amp; cheek Then impression is removed by a sudden jerk 10. INSPECT THE IMPRESSION FOR DEFECtS Mandibular impressionMaxillary impression 11. IMPRESSION TECHNIQUES Mc LEANS PHYSIOLOGIC IMPRESSION FLUID WAX FUNCTIONAL IMPRESSION SELECTIVED PRESSURE IMPRESSION 12. Mc LEANS PHYSIOLOGIC IMPRESSION Procedure A custom impression tray is constructed over a preliminary cast Functional impression of distal extension ridge is made. Patient applies some biting force with occlusion rims Then an Alginate impression is made with the 1st impression held in its functional position with finger pressure 13. FLUID WAX FUNCTIONAL IMPRESSION Make an anatomic impression of the arch using alginate Fabricate a refractory cast using this impression Fabricate the partial denture framework over the refractory cast 14. Draw the outline of the denture base Cast is coated with separating medium Wax Spacer is adapted over the crest of the edentulous ridge 15. Framework is placed over the spacer Auto-polymerizing resin is mixed to dough stage and is adapted and contoured over the framework along the length of the ridge Borders of the tray are trimmed 16. SELECTIVED PRESSURE IMPRESSION More force are applied to areas that can absorb stress without adverse response &amp; protect that areas that is least able to absorb force Stress bearing areas are the buccal shelf area &amp; the lingual slopes of residual ridge stress bearing areas The denture base made from this impression will be closely adapted to &amp; in firm contact with the tissues in buccal shelf area 17. CONCLUSION An accurate impression is vital for the success of a cast partial denture. So proper selection of material, impression technique and the skill of the dentist plays a key role in the success of the overall treatment. 18. REFRENCE Mc Crackens Removable Partial Prosthodontics REMOVABLE PARTIAL PROSTHODONTICS-STEWARTS 4TH EDISION </p>