Altered cast technique
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Altered Cast Technique - PowerPoint PPT Presentation

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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

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Altered cast technique2 l.jpg
Altered Cast Technique

  • Corrected Cast

  • Modified Cast

  • Destroyed Cast

Altered cast impressions l.jpg
Altered Cast Impressions

  • Impression of soft tissue if not captured in framework impression

Purpose l.jpg

  • 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 l.jpg
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 l.jpg
Impression Technique

  • Framework must fit intraorally

  • Add tray to framework

    • 1 mm wax relief

    • Heat and fully seat framework into wax

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Check Seating on Cast and in Mouth

  • After tray added

    • Rests must be fully seated

    • Tissue stop contacts cast

    • No resistance as framework seated

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Check Peripheries

  • 2-3 mm short of vestibular

  • No displacement when:

    • Pull on cheeks, lips

    • Patient activates tongue

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Border Mold

  • Same as a denture

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Altered Cast Impression

  • Remove wax spacer

  • Coat tray with adhesive

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Altered Cast Impression

  • Polyvinyl siloxane

  • Carefully load tray-no material under rests, guideplanes, major connector

  • Seat with pressure ONLYover rests

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No Pressure Over Tray

  • Will cause tissue compression

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Remove & Inspect Impression

  • Fully seated

  • No material under rests or minor connectors

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Send to Laboratory

  • Lab Steps

    • Section cast

    • Place retentive grooves in cast

    • Ensure no contact between impression material & cast

    • Sticky wax framework in place

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Lab Steps

  • Box impression

  • Seal retainer, major & minor connector borders

  • Pour new ridge areas in different color stone

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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 teethduring pouring makes articulation impossible

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Next Step

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