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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