Altered Cast Technique Altered Cast Technique Corrected Cast

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

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