Altered Cast Impression Technique

rationale
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rationale
Making an impression of the mucosa under controlled pressure

Allows the ridge recorded in functional form to be related to teeth.
Allows the ridge recorded in functional form to be related to teeth.

therefore
the prosthesis derives support from both the teeth and mucosa when it is seated
Indications for Altered cast Impression
Mandibular distal extension (Class I & II)

Large edentulous spans

Any case which border is distorted
Image: Indications for Altered cast Impression
altered cast impression is not indicated when?
short edentulous spaces

(image: kennedy class III mod 2)
Image: altered cast impression is not indicated when?
altered cast technique steps
framework try-in

delineate RPD borders

apply vaseline to distal extension

block out undercuts

warm one layer of baseplate wax and adapt to RPD distal extension

apply vaseline

heat framework and press to cast

adapt triad to cast and over framework

place cast in curing unit for polymerization

round borders using acrylic bur

check borders clinically (2-3 mm short of vestibule)

border molding
altered cast technique steps

framework try in
fit checker PVS injected into partial

sit partial ASAP

high spots will show as burnout

adjust with high speed and diamond bur

then check with explorer to see if rest seats are completely seated

now ready for altered cast technique
Image: altered cast technique steps framework try in
altered cast technique steps

heat framework and press to cast
Apply pressure ONLY to rest seats and major connector.

Therefore, framework is not tilted
Image: altered cast technique steps heat framework and press to cast
altered cast technique steps

border molding movements
pull on cheeks and lips

patient activates tongue (stick out and move R and L)
altered cast technique steps

border molding material
green compound or heavy body PVS
Image: altered cast technique steps border molding material
altered cast technique steps

border molding material: green compound
pain tray with PVS adhesive

then use PVS light body for final impression
Image: altered cast technique steps border molding material: green compound
altered cast technique steps border molding material: heavy body PVSmake final impression using PVS light body (no PVS adhesive needed)alternative impression materialPolyether -Helpful when patient has excessive salivalab stepsCut the edentulous segment of the master cast Place retentive groove in the cast Assure there is no contact between impression material and cast Box the impression pour the impression There should be no impression material under rests, guide planes, major connectorcommon errorsFramework is not seated during impression or pouring Verified framework fit while wax denture try-in Stone leaking over teeth during pouring the model Carefully seal the waxaltered cast vs one-piece cast study M&M: Seventy-two patients receiving a mandibular bilateral distal extension removable partial denture were assigned randomly for treatment using either a one-piece or an altered cast. conclusion:The altered cast impression procedure does not offer significant advantages over the one piece cast provided the standards used in this study are metThe altered cast impression procedure does not offer significant advantages over the one piece cast provided the standards used in this study are met what are the standards used?a completely extended impression use of magnification to adjust and ensure complete seating of the framework coverage of the retromolar pad and buccal shelf by the base