Altered Cast TechniqueAltered Cast Technique

Altered Cast TechniqueAltered Cast Technique

• Corrected Cast

• Modified Cast

• Destroyed Cast

• Corrected Cast

• Modified Cast

• Destroyed Cast

Altered Cast ImpressionsAltered Cast Impressions

• Impression of soft tissue if not captured in framework impression

• Impression of soft tissue if not captured in framework impression

PurposePurpose

• Improve adaptation of the denture base to the ridge to minimize movement during function

• Equalize stress between ridge and abutments

• Improve contours of peripheries

• 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 NeededWhen 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

• 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 TechniqueImpression Technique

• Framework must fit intraorally

• Add tray to framework– 1 mm wax relief

– Heat and fully seat framework into wax

• 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 MouthCheck Seating on Cast and in Mouth

• After tray added– Rests must be fully seated

– Tissue stop contacts cast

– No resistance as framework seated

• After tray added– Rests must be fully seated

– Tissue stop contacts cast

– No resistance as framework seated

Check PeripheriesCheck Peripheries

• 2-3 mm short of vestibular

• No displacement when: – Pull on cheeks, lips

– Patient activates tongue

• 2-3 mm short of vestibular

• No displacement when: – Pull on cheeks, lips

– Patient activates tongue

Border MoldBorder Mold

• Same as a denture• Same as a denture

Altered Cast ImpressionAltered Cast Impression

• Remove wax spacer

• Coat tray with adhesive

• Remove wax spacer

• Coat tray with adhesive

Altered Cast ImpressionAltered Cast Impression

• Polyvinyl siloxane• Carefully load tray

-no material under rests, guideplanes, major connector

• Seat with pressure ONLYover rests

• Polyvinyl siloxane• Carefully load tray

-no material under rests, guideplanes, major connector

• Seat with pressure ONLYover rests

No Pressure Over TrayNo Pressure Over Tray

• Will cause tissue compression• Will cause tissue compression

Remove & Inspect ImpressionRemove & Inspect Impression

• Fully seated

• No material under rests or minor connectors

• Fully seated

• No material under rests or minor connectors

Send to LaboratorySend 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– Section cast

– Place retentive grooves in cast

– Ensure no contact between impression material & cast

– Sticky wax framework in place

Lab StepsLab Steps

– Box impression

– Seal retainer, major & minor connector borders

– Pour new ridge areas in different color stone

– Box impression

– Seal retainer, major & minor connector borders

– Pour new ridge areas in different color stone

Potential Problems with the Altered Cast Technique

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

• 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 StepNext Step

• Lab adds record base and occlusion rim to framework for jaw relation records

• Lab adds record base and occlusion rim to framework for jaw relation records