Transcript Final Impressions for Complete Dentures Polyvinyl Siloxanes Addition Reaction Silicone • Hydrophobic • Newer materials more hydrophilic – Similar to Polysulfides & Polyethers • Flow – Thixotropic –

Final Impressions for
Complete Dentures
Polyvinyl Siloxanes
Addition Reaction Silicone
• Hydrophobic
• Newer materials more hydrophilic
– Similar to Polysulfides & Polyethers
• Flow
– Thixotropic
– Require pressure to flow
Polyvinyl Siloxanes
Addition Reaction Silicone
• Good dimensional stability
• Excellent elastic recovery
• Excellent dimensional accuracy
• Material of choice
Wax Spacer Removal
• After border molding, remove wax
spacer
• Do not dislodge border molding
Custom Trays
• Smooth sharp surfaces of border
molding or tray
Effect of Sharp Borders
Custom Trays
• Place holes in tray to allow release of
hydraulic pressure
Adhesive
• Paint inside of tray & border
molding
• Allow to dry 7-15 minutes
Final Impressions
• Dry tissues with 2x2 gauze folded
in cotton pliers
Tissue Rest
• Leave dentures out 24 hours
– Tissue recovery
• Use low viscosity polyvinyl siloxane
material
– Use adhesive
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
Final Impressions
Subsurface Voids
• Seat tray front to
back - use gauze
over holes in tray
• Ensure tray is
centered &
properly oriented
Tech.
Dentist
A
B
C
TOTAL
F-B
3
2
1
Even 4
3
6
B-F
6
4
3
__________________________
6
13
13
TOTAL 13
32
9
10
Tissue Manipulation
Maxilla
• Slight manipulation of cheeks, lips
• Patient moves mandible to side to
side for maxillary impression
Tissue Manipulation
Mandible
• Hold tray in position & have patient:
– Pucker lips
– Lift & move tongue forward & side to side
Impressions Videos
Final Impressions
Two Mirror Impression Technique
Set Time
• Most polyvinyl siloxane
materials set within 6 minutes
Evaluating Impression Video
Post-palatal Seal
• Compensates for polymerization shrinkage and
distortion from palate
• Enhances retention
Prior to Removal from Cast
After Removal from Cast
Post-palatal Seal
• Mark post-palatal seal with indelible stick – Glandular area
& vibrating line
• Place impression in mouth, line transfers to impression
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)
Boxing Final Impressions
Rationale
• Superior hardness of cast surface
• Provides land area & preserves peripheral
role
• Minimizes trimming
Trimming the Cast
Trimming the Cast
Land Area = 4mm Wide
Boxing Impression Video