WORKING CASTS AND DIE SYSTEMS dr shabeel pn

WORKING CASTS WITH A SEPARATE DIE The 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 لاا WORKING CAST WITH A REMOVABLE DIE

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

FOUR SYSTEMS Straight dowel pin Curved dowel pin Pindex system Di-lok trays

PINDEX SYSTEM Reverse drill press is used that can be removed and replaced with great precision Impression poured before positioning dowel pins Drills parellel holes from underside Of the trimmed cast

Pour the impression adding 20mm of stone beyond the edge of the tray—allow trimmg Cast set in 60 min Remove the cast -Wet the cast

PARTS OF PINDEX MACHINE

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 holes The 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 former Wax is removed

Saw cuts are marked with pencil Cast is removed

Dies are sectioned from underside and from occlusal aspect

Large condensers are used to loosen the dies

Mounted on an articulator

DI-LOK TRAY 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 cast Errors in CRrecord are significant in working casts Kinematic face bow is used Reorganised occlusion by selective grinding and reorganising anterior guidance before tooth preparation

REFERENCES FUNDAMENTALS OF FPD ----H.T . SHILLINGBURG THEORY AND PRACTICE OF FPD --- TYLMAN CONTEMPARORY FPD----ROSENSTIEL

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