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