Working Casts and Die Systems

WORKING CASTS AND DIE SYSTEMS

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WORKING CASTS WITH A SEPARATE DIE

oThe simplest means•It keeps the relationship with the abutment

fixed and immovable

Stone is added to the impression in small increments above the preparation

TRAY IS TILTED TO FILL THE PREPARATION

Stone is added to the impression so that the base of the set stone will be 1 inch

The die is first trimmed on a model trimmer

•A properly trimmed die handle is slightly larger in diameter than the preparation

Improperly trimmed die with a handle that meets the preparation at an angle

Handle should be 1 inch long

The die is trimmed with an acrylic bur

Shaping of the handle near the finish line is completed with a scalpel

The die is smoothened below the finish line with the discoid end of a tanner carver

The preparation finish line on the die should be red pencil outlined with a

Die relief agent is painted on the preparation-20 to 40 mm

WORKING CAST WITH A REMOVABLE DIE

The die must return to their exact original positionsThe die must remain stable , even when invertedThe cast containing the dies must be easy to mount on the articulator

FOUR SYSTEMSFOUR SYSTEMS

Straight dowel pinCurved dowel pinPindex system

Di-lok trays

Reverse drill press is used that can be removed and replaced with great precisionImpression poured before positioning dowel pinsDrills parellel holes from underside Of the trimmed cast

Pour the impression adding 20mm of stone beyond the edge of the tray—allow trimmgCast set in 60 minRemove the cast

-Wet the cast

Cast should be 15mm thick , exclusive the teeth

After trimming location of pin holes is marked with a pencil

Pencil marks are placed under the illuminated dot

Debris is removed from pin holesThe holes are refined with a hand reamer

Cyanoacrylate cement is placed on the prior to cementing the pin tips

Shorter pins are placed before the long pins

White sleeves are placed on the long pins and gray sleeves on the short pins

The bottom of the cost is lightly coated with petrolactum

The ends of the gray sleeves are blocked with wax

Utility wax is placed on the ends of the long pins

A palatal \tongue filler is made of boxingwax and seated on the cast

Boxing wax is applied around the cast

The base is poured in microstone

Cast is seated in the base formerWax is removed

Saw cuts are marked with pencilCast is removed

Dies are sectioned from underside and from occlusal aspect

Large condensers are used to loosen the dies

Mounted on an articulator

Snap apart plastic tray with internal orienting grooves and notches to reassemble working casts and dies are used

CURVED DOWEL PIN

DOWELS INCORPORATED BEFORE POURING THE IMPRESSINO

WORKING CAST VERSES DIAGNOSTIC CASTS

Accuracy of the castErrors in CRrecord are significant in working castsKinematic face bow is usedReorganised occlusion by selective grinding and reorganising anterior guidance before tooth preparation

REFERENCESREFERENCESFUNDAMENTALS OF FPD ----H.T .

SHILLINGBURGTHEORY AND PRACTICE OF FPD ---

TYLMANCONTEMPARORY FPD----

ROSENSTIEL

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