Transcript Altered Cast Technique

Altered Cast Technique
Altered Cast Technique
• Corrected Cast
• Modified Cast
• Destroyed Cast
Altered Cast Impressions
• Impression of soft tissue if not
captured in framework impression
Purpose
• Improve adaptation of the denture base to the
ridge to minimize movement during function
• Equalize stress between ridge and abutments
• Improve contours of peripheries
When Needed
• Mandibular distal extensions (Class I & II)
• Extensive edentulous spans
• Any case where periphery is distorted &
needs correction
• Less necessary in maxilla due to major
connector contact with palate
Impression Technique
• Framework must fit intraorally
• Add tray to framework
– 1 mm wax relief
– Heat and fully seat framework into wax
Check Seating on Cast and in Mouth
• After tray added
– Rests must be fully seated
– Tissue stop contacts cast
– No resistance as framework
seated
Check Peripheries
• 2-3 mm short of vestibular
• No displacement when:
– Pull on cheeks, lips
– Patient activates tongue
Border Mold
• Same as a denture
Altered Cast Impression
• Remove wax spacer
• Coat tray with adhesive
Altered Cast Impression
• Polyvinyl siloxane
• Carefully load tray
-no material under rests,
guideplanes, major
connector
• Seat with pressure ONLY
over rests
No Pressure Over Tray
• Will cause tissue compression
pressure
spring-back
Remove & Inspect Impression
• Fully seated
• No material under rests or
minor connectors
Send to Laboratory
• Lab Steps
– Section cast
– Place retentive grooves in cast
– Ensure no contact between
impression material & cast
– Sticky wax framework in place
Lab Steps
– Box impression
– Seal retainer, major & minor
connector borders
– Pour new ridge areas in
different color stone
Potential Problems with the
Altered Cast Technique
• Framework not seated either during
impression (material under rest, gp) or
when being poured will result in an
RPD that won’t fit properly on
teeth/tissues
• Stone leaking over teeth during
pouring makes articulation impossible
Next Step
• Lab adds record base and
occlusion rim to framework
for jaw relation records