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Impression procedures for removable partial denture

protho seminar

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Impression procedures for removable partial denture

  1. 1. Presented by Shiji margaret Final Year BDS
  2. 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. 3. MATERIALS AVAILABLE FOR MAKING IMPRESSION Reversible hydrocolloids (agar-agar) Irreversible hydrocolloids (Alginate) Elastomeric impression materials
  4. 4. STEPS IN IMPRESSION MAKING Position of patient & dentist Tray selection Mixing the material & loading into the tray Impression making & removal Inspecting, cleaning & disinfecting the impression
  5. 5. POSITION OF PATIENT & DENTIST Dentist should stand & 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. 6. Mandibular impressionMaxillary impression
  7. 7. IMPRESSION TRAY SELECTION Stock trays for dentulous & partially edentulous arches are of 3 types: Rimlock trays Perforated metal trays Plastic disposable trays
  8. 8. MIXING IMPRESSION MATERIAL Bowel Spatula Scoop and Measuring jar
  9. 9. REMOVAL OF IMPRESSION FROM MOUTH Clinically the initial set of alginate is determined by loss of surface tackiness Release seal by retracting lips & cheek Then impression is removed by a sudden jerk
  10. 10. INSPECT THE IMPRESSION FOR DEFECtS Mandibular impressionMaxillary impression
  12. 12. Mc LEAN’S 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 it’s functional position with finger pressure
  13. 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. 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. 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. 16. SELECTIVED PRESSURE IMPRESSION • More force are applied to areas that can absorb stress without adverse response & protect that areas that is least able to absorb force • Stress bearing areas are the buccal shelf area & the lingual slopes of residual ridge stress bearing areas • The denture base made from this impression will be closely adapted to & in firm contact with the tissues in buccal shelf area
  17. 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. 18. REFRENCE  Mc Cracken’s Removable Partial Prosthodontics  REMOVABLE PARTIAL PROSTHODONTICS-STEWART’S 4TH EDISION