final impressions

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final impressions

  1. 1. Final Impressions for Complete Dentures
  2. 2. Potential Impression Materials • Irreversible Hydrocolloid – Hydrophilic but viscous – Stock tray distorts vestibular tissues
  3. 3. Potential Impression Materials • Zinc oxide & eugenol – Fast set – Rigid (undercuts difficult), – Poor taste
  4. 4. Potential Impression Materials • Polysulfides – Poor taste – Poor dimensional stability – Poor elastic recovery
  5. 5. Potential Impression Materials • Silicones – Addition reaction – Acceptable taste – Dimensionally stable – Elastic recovery
  6. 6. Potential Impression Materials • Polyethers – Poor taste – Dimensionally stable – Elastic recovery – Expensive
  7. 7. Polyvinyl Siloxanes Addition Reaction Silicone • Hydrophobic • Newer materials more hydrophilic – Similar to Polysulfides & Polyethers • Flow – Thixotropic – Require pressure to flow
  8. 8. Polyvinyl Siloxanes Addition Reaction Silicone • Good dimensional stability • Excellent elastic recovery • Excellent dimensional accuracy • Material of choice
  9. 9. Wax Spacer Removal • After border molding, remove wax spacer • Do not dislodge border molding
  10. 10. Custom Trays • Smooth sharp surfaces of border molding or tray
  11. 11. Effect of Sharp Borders
  12. 12. Custom Trays • Place holes in tray to allow release of hydraulic pressure
  13. 13. Adhesive • Paint inside of tray & border molding • Allow to dry 7-15 minutes
  14. 14. Final Impressions • Dry tissues with 2x2 gauze folded in cotton pliers
  15. 15. Tissue Rest • Leave dentures out 24 hours – Tissue recovery • Use low viscosity polyvinyl siloxane material – Use adhesive
  16. 16. Final Impressions • Enough material to replace wax spacer • Load quickly - viscosity • Avoid bubbles when loading tray
  17. 17. Final Impressions • Cover all border molding with impression material
  18. 18. Tray Insertion • Insert side of tray against commissure of mouth & rotating the tray into place while pulling outward on the commissure of the contralateral side
  19. 19. Final Impressions • Seat tray front to back - use gauze over holes in tray • Ensure tray is centered & properly oriented Subsurface Voids Subsurface Voids Tech. Tech. Dentist Dentist A A B B C C TOTAL TOTAL F-B 2 1 6 F-B 3 3 2 1 6 Even 4 3 6 13 Even 4 3 6 13 B-F 6 4 3 13 B-F 6 4 3 13 __________________________ __________________________ TOTAL 13 TOTAL 13 9 9 10 10 32 32
  20. 20. Tissue Manipulation Maxilla • Slight manipulation of cheeks, lips • Patient moves mandible to side to side for maxillary impression
  21. 21. Tissue Manipulation Mandible • Hold tray in position & have patient: – Pucker lips – Lift & move tongue forward & side to side
  22. 22. Impressions Videos Final Impressions Two Mirror Impression Technique
  23. 23. Set Time • Most polyvinyl siloxane materials set within 6 minutes
  24. 24. Evaluating Impression Video
  25. 25. Evaluation of Borders • Material should not be more than l mm thick over border molding (otherwise it was not fully seated)
  26. 26. Final Impressions
  27. 27. Final Impressions
  28. 28. Final Impressions
  29. 29. Post-palatal Seal • Compensates for polymerization shrinkage away from palate • Enhances retention
  30. 30. Post-palatal Seal • Mark post-palatal seal with indelible stick – Glandular area & vibrating line • Place impression in mouth, line transfers to impression
  31. 31. Post-palatal Seal • • • • Disinfect Refresh the line with new indelible stick Prescribe a mechanical post-palatal seal Pour impression in Type III stone (ie. Microstone)
  32. 32. Boxing Final Impressions Rationale • Superior hardness of cast surface • Provides land area & preserves peripheral role • Minimizes trimming
  33. 33. Boxing Impression Trimming Alginate
  34. 34. Pour the Model
  35. 35. Trimming the Cast
  36. 36. Trimming the Cast Land Area = 4mm Wide
  37. 37. Boxing Impression Video

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