Final Impressions for Complete Dentures

| April 21, 2012 | 0 Comments

Final Impressions for Complete Dentures

For final impressions for Complete Dentures required materials are :

Impression Materials
Irreversible hydrocolloid – hydrophilic, but viscous; stock tray distorts vestibular tissues
Zinc oxide and eugenol – fast set, rigid (undercuts difficult), poor taste
Polysulfides – poor taste, poor dimensional stability, poor elastic recovery
Silicones – addition reaction – acceptable taste, dimensionally stable, elastic recovery
Polyethers – poor taste, dimensionally stable, elastic recovery, expensive

Custom Trays:
– After completion of border molding, remove wax spacer carefully, so as not to dislodge the border molding
– The remaining space provides relief from the buildup of hydraulic pressure and provides room for an adequate, uniform thickness for impression material to improve impression accuracy
– Bevel any sharp internal surfaces of the border molding or tray to provide a smooth transition that will not distort the tissue
– Place holes in tray to allow release of hydraulic pressure
– Paint inside of tray and border molding with adhesive – allow to dry 7-15 minutes

Taking Final Impression

  1. Leave dentures out for 24 hours prior – tissue recovery
  2. Use low viscosity polyvinyl siloxane material (must use rubber base adhesive in tray)
  3. Place enough impression material to replace the wax spacer
  4. Try not to incorporate bubbles when loading the custom tray
  5. Cover all border molding with impression material
  6. Dry tissues with 2×2 gauze folded in cotton pliers
  7. Insert by placing one side of the tray against one of the commissures of the mouth and rotating the tray into the mouth while pulling outward on the commisure of the contralateral side
  8. Seat tray front to back – use gauze over holes in tray
  9. Ensure the tray is centered and properly oriented
  10. Manipulate cheeks, lips and move mandible to sides for maxillary impression; hold tray in position and have patient suck cheeks together, lift and move tongue forward and toward the corners of the mouth
  11. Most polyvinyl siloxane materials set within approximately 6 minutes
  12. Material should not be more than l mm thick over border molding (otherwise it was not fully seated)

Recording Post-palatal Seal Area

  1. Mark the area of the post-palatal seal intraorally with indelible stick – glandular areaand vibrating line
  2. Place impression in mouth, line transfers to the impression
  3. Disinfect, refresh the line with a new indelible stick
  4. Prescribe a mechanical post-palatal seal
  5. Pour impression in Microstone

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Category: Prosthodontics, WIKI

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