final impressions

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    06-May-2015
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  • 1.Final Impressions for Complete Dentures

2. Potential Impression Materials Irreversible Hydrocolloid Hydrophilic but viscous Stock tray distorts vestibular tissues 3. Potential Impression Materials Zinc oxide & eugenol Fast set Rigid (undercuts difficult), Poor taste 4. Potential Impression Materials Polysulfides Poor taste Poor dimensional stability Poor elastic recovery 5. Potential Impression Materials Silicones Addition reaction Acceptable taste Dimensionally stable Elastic recovery 6. Potential Impression Materials Polyethers Poor taste Dimensionally stable Elastic recovery Expensive 7. Polyvinyl Siloxanes Addition Reaction Silicone Hydrophobic Newer materials more hydrophilic Similar to Polysulfides & Polyethers Flow Thixotropic Require pressure to flow 8. Polyvinyl Siloxanes Addition Reaction Silicone Good dimensional stability Excellent elastic recovery Excellent dimensional accuracy Material of choice 9. Wax Spacer Removal After border molding, remove wax spacer Do not dislodge border molding 10. Custom Trays Smooth sharp surfaces of border molding or tray 11. Effect of Sharp Borders 12. Custom Trays Place holes in tray to allow release of hydraulic pressure 13. Adhesive Paint inside of tray & border molding Allow to dry 7-15 minutes 14. Final Impressions Dry tissues with 2x2 gauze folded in cotton pliers 15. Tissue Rest Leave dentures out 24 hours Tissue recovery Use low viscosity polyvinyl siloxane material Use adhesive 16. Final Impressions Enough material to replace wax spacer Load quickly - viscosity Avoid bubbles when loading tray 17. Final Impressions Cover all border molding with impression material 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. Final Impressions Seat tray front to back - use gauze over holes in tray Ensure tray is centered & properly orientedSubsurface Voids Subsurface Voids Tech. Tech.Dentist Dentist A AB BC CTOTAL TOTALF-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 139 910 1032 32 20. Tissue Manipulation Maxilla Slight manipulation of cheeks, lips Patient moves mandible to side to side for maxillary impression 21. Tissue Manipulation Mandible Hold tray in position & have patient: Pucker lips Lift & move tongue forward & side to side 22. Impressions Videos Final Impressions Two Mirror Impression Technique 23. Set Time Most polyvinyl siloxane materials set within 6 minutes 24. Evaluating Impression Video 25. Evaluation of Borders Material should not be more than l mm thick over border molding (otherwise it was not fully seated) 26. Final Impressions 27. Final Impressions 28. Final Impressions 29. Post-palatal Seal Compensates for polymerization shrinkage away from palate Enhances retention 30. Post-palatal Seal Mark post-palatal seal with indelible stick Glandular area & vibrating line Place impression in mouth, line transfers to impression 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. Boxing Final Impressions Rationale Superior hardness of cast surface Provides land area & preserves peripheral role Minimizes trimming 33. Boxing Impression Trimming Alginate 34. Pour the Model 35. Trimming the Cast 36. Trimming the Cast Land Area = 4mm Wide 37. Boxing Impression Video