working casts and die systems
TRANSCRIPT
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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