Altered Cast TechniqueAltered Cast Technique

Altered Cast TechniqueAltered Cast Technique

• Corrected Cast

• Modified Cast

• Corrected Cast

• Modified Cast

Altered Cast ImpressionsAltered Cast Impressions

• Impression of residual ridge

• Custom impression tray attached to the framework

• Impression of residual ridge

• Custom impression tray attached to the framework

PurposePurpose

• Impression is used to modify master cast

• More accurate relationship between abutments & ridge

• Equalize stress between ridge and abutments

• Correct peripheral adaptation

• Impression is used to modify master cast

• More accurate relationship between abutments & ridge

• Equalize stress between ridge and abutments

• Correct peripheral adaptation

When NeededWhen Needed

• Framework most likely adjusted

• Class I & II - relationship most N.B.

• Extensive Class III & IV cases

• Tooth mobility + compressible mucosa

• Less necessary in maxilla

• Framework most likely adjusted

• Class I & II - relationship most N.B.

• Extensive Class III & IV cases

• Tooth mobility + compressible mucosa

• Less necessary in maxilla

Impression TechniqueImpression Technique

• Well Fitting Framework

• Place relief over ridge– 1 mm wax relief

– Separator (Alcote)

– Heat and fully seat framework

• Well Fitting Framework

• Place relief over ridge– 1 mm wax relief

– Separator (Alcote)

– Heat and fully seat framework

Check SeatingCheck Seating

• If not seated, remove, repeat– Rests fully seated

– Tissue stop contacts cast

– Metal adjacent abutment contacts cast

– No resistance as framework seated

• If not seated, remove, repeat– Rests fully seated

– Tissue stop contacts cast

– Metal adjacent abutment 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

• Simulate final denture border• Simulate final denture border

Make Altered Cast ImpressionMake Altered Cast Impression

• Ensure tray is well retained by framework

• Remove wax spacer

• Coat tray with adhesive

• Wait 10-15 minutes

• Ensure tray is well retained by framework

• Remove wax spacer

• Coat tray with adhesive

• Wait 10-15 minutes

Altered Cast ImpressionAltered Cast Impression

• Polyvinyl siloxane– Light or medium body

• Carefully load tray• No material under rests,

g.p.’s, max. major connector, etc.

• Seat with pressure over rests

• Polyvinyl siloxane– Light or medium body

• Carefully load tray• No material under rests,

g.p.’s, max. major connector, etc.

• Seat with pressure over rests

No Pressure Over GridworkNo Pressure Over Gridwork

• Fulcruming or tissue compression

• Spring back and lack of tissue contact

• Fulcruming or tissue compression

• Spring back and lack of tissue contact

a

spring-backpressure

Remove & Inspect ImpressionRemove & Inspect Impression

• Absence of voids

• Minimal burnthrough

• Covers supporting tissues

• Fully seated, etc.

• Absence of voids

• Minimal burnthrough

• Covers supporting tissues

• Fully seated, etc.

Send to LaboratorySend to Laboratory

• Lab Steps– Section residual ridge from cast

– Ensure no contact between impression & cast

– Place retentive grooves in cast

– Sticky wax in place

• Lab Steps– Section residual ridge from cast

– Ensure no contact between impression & cast

– Place retentive grooves in cast

– Sticky wax in place

Lab StepsLab Steps

– Box impression

– Ensure water tight seal

– Seal retainer, major & minor connector borders

– Pour new ridge areas in different color stone

– Box impression

– Ensure water tight seal

– Seal retainer, major & minor connector borders

– Pour new ridge areas in different color stone

Problems with the Altered Cast Technique

Problems with the Altered Cast Technique

• If tray is added carelessly, it can alter passive relationship

• Excess impression material under framework

• If inadequately sealed, stone over teeth, can’t articulate model

• If tray is added carelessly, it can alter passive relationship

• Excess impression material under framework

• If inadequately sealed, stone over teeth, can’t articulate model

Record Base for Wax SetupRecord Base for Wax Setup

• Place Denture Base– Hard baseplate wax

• Easier to remove during processing

• Can melt or distort

– Acrylic resin• Harder to remove• More rigid and stable for jaw

relation

• Place Denture Base– Hard baseplate wax

• Easier to remove during processing

• Can melt or distort

– Acrylic resin• Harder to remove• More rigid and stable for jaw

relation

Jaw Relation RecordsJaw Relation Records

• Mount Casts on Articulators– Facebow / Earbow Record

• Maxilla to hinge axis

– Centric Record• Maxilla to mandible position

– Protrusive Record• Program articulator for excursions

• Mount Casts on Articulators– Facebow / Earbow Record

• Maxilla to hinge axis

– Centric Record• Maxilla to mandible position

– Protrusive Record• Program articulator for excursions