Final Impressions for Complete Dentures

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Final Impressions for Complete Dentures
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Potential Impression Materials

• Irreversible Hydrocolloid
• Hydrophilic but viscous
• Stock tray distorts vestibular tissues

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Potential Impression Materials

• Zinc oxide eugenol
• Fast set
• Rigid (undercuts difficult),
• Poor taste

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Potential Impression Materials

• Polysulfides
• Poor taste
• Poor dimensional stability
• Poor elastic recovery

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Potential Impression Materials

• Silicones
• Addition reaction
• Acceptable taste
• Dimensionally stable
• Elastic recovery

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Potential Impression Materials

• Polyethers
• Poor taste
• Dimensionally stable
• Elastic recovery
• Expensive

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Polyvinyl Siloxanes Addition Reaction Silicone

• Hydrophobic
• Newer materials more hydrophilic
• Similar to Polysulfides Polyethers
• Flow
• Thixotropic
• Require pressure to flow

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Polyvinyl Siloxanes Addition Reaction Silicone

• Good dimensional stability
• Excellent elastic recovery
• Excellent dimensional accuracy
• Material of choice

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Wax Spacer Removal

• After border molding, remove wax spacer
• Do not dislodge border molding

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Custom Trays

• Smooth sharp surfaces of border molding or tray

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Effect of Sharp Borders
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Custom Trays

• Place holes in tray to allow release of hydraulic
  pressure

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Adhesive

• Paint inside of tray border molding
• Allow to dry 7-15 minutes

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Final Impressions

• Dry tissues with 2x2 gauze folded in cotton pliers

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Tissue Rest

• Leave dentures out 24 hours
• Tissue recovery
• Use low viscosity polyvinyl siloxane material
• Use adhesive

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Final Impressions

• Enough material to replace wax spacer
• Load quickly - viscosity
• Avoid bubbles when loading tray

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Final Impressions

• Cover all border molding with impression material

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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

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Final Impressions
Subsurface Voids Tech. Dentist
A B C TOTAL F-B 3 2 1 6 Even 4 3 6 13
B-F 6 4 3 13 __________________________
TOTAL 13 9 10 32

• Seat tray front to back - use gauze over holes in
  tray
• Ensure tray is centered properly oriented

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Tissue ManipulationMaxilla

• Slight manipulation of cheeks, lips
• Patient moves mandible to side to side for
  maxillary impression

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Tissue ManipulationMandible

• Hold tray in position have patient
• Pucker lips
• Lift move tongue forward side to side

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Set Time

• Most polyvinyl siloxane materials set within 6
  minutes

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Evaluation of Borders

• Material should not be more than l mm thick over
  border molding (otherwise it was not fully seated)

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Final Impressions
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Final Impressions
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Final Impressions
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Post-palatal Seal

• Compensates for polymerization shrinkage away
  from palate
• Enhances retention

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Post-palatal Seal

• Mark post-palatal seal with indelible stick
  Glandular area vibrating line
• Place impression in mouth, line transfers to
  impression

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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)

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Boxing Final ImpressionsRationale

• Superior hardness of cast surface
• Provides land area preserves peripheral role
• Minimizes trimming

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Boxing ImpressionTrimming Alginate
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Pour the Model
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Trimming the Cast
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Trimming the CastLand Area 4mm Wide