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INTRODUCTION
FabricationFabrication ofof aa fixedfixed partialpartial denturedenture involvesinvolves
thethe fabricationfabrication ofof thethe waxwax pattern,pattern, casting,casting,
solderingsoldering andand finishingfinishing.. HereHere wewe shallshall studystudy inin
detaildetail aboutabout thesethese proceduresprocedures.
MODELS,CAST,& DIES
MODELMODEL:: ItIt aa positivepositive replicareplica ofof thethe teethteeth andand adjacentadjacent
structuresstructures usedused primarilyprimarily forfor observationobservation andand diagnosisdiagnosis..
CASTCAST:: AA workingworking model,model, mastermaster castcast..
DIEDIE:: DieDie isis aa positivepositive replicareplica ofof thethe individualindividual prepre--paredpared toothtooth
onon whichwhich thethe inlays,crowns,bridgesinlays,crowns,bridges areare mademade.. TheseThese areare individualindividual
toothtooth replicasreplicas preparedprepared forfor easiereasier handlinghandling duringduring waxwax patternpattern
fabricationfabrication andand finishingfinishing ofof inaccessibleinaccessible areasareas ofof thethe castcast
TYPES OF CAST AND DIE TYPES OF CAST AND DIE
MATERIALSMATERIALS
GYPSUM:
a) Type IV-Dental stone, Highstrength
b) Type V-dental stone ,High Strength, high Expansion
c) Dental stone+lignosulphonates
METALS:
a) Electroformed/Eletroplated.
b) Sprayed metals.
c) Amalgam.
POLYMERS;
a) Metal-filled resins or inorganic filled resins.
b) Epoxy.
CEMENTS:
a) silicophosphate or polyacrylic acid bonded cements.
CERAMIC OR REFRACTORY DIE MATERIALS:CERAMIC OR REFRACTORY DIE MATERIALS:
a)a) For direct baking of porcelain crown or preparation of wax For direct baking of porcelain crown or preparation of wax
pattern for casting.pattern for casting.
Type IV& Type V Stone dies, Electroformed dies, Epoxy
resins , Refractory or materials are recommended die
materials.
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IDEAL PROPERTIES OF DIE
MATERIALS1. It should be dimensionally accurate.
2. It should have high abrasion resistance, should possess
good strength,& have smooth surface .
3. Toughness to allow burnishing of foil & resist breakage.
4. Ability to reproduce all fine details in the impression.
5. Compatibility with all impression materials.
6. Colour contrast with wax, porcelain & alloys.
7. Easy & quick manipulation & rapid fabrication.
8. Non-injurious to health by touch or inhalation.
9. Economic.
IDEAL REQUIREMENTS OF A DIE
SYSTEM
The die should be easy to remove and replace The die should be easy to remove and replace
in its original position.in its original position.
The die must be stable when placed in the The die must be stable when placed in the
cast.cast.
It should be easy to mount in the articulatorIt should be easy to mount in the articulator
TYPES OF DIES
Based on the design, die systems can be classified into:
11 WORKINGWORKING CASTCAST WITHWITH SEPARATESEPARATE DIEDIE SYSTEMSYSTEM
22 WORKING CAST WITH REMOVABLE DIE SYSTEMWORKING CAST WITH REMOVABLE DIE SYSTEM.
There are three commonly used removable die systems,
they are:
a)Dowel pin system
-Straight
-Curved
b)Di-lok tray system
c)Pindex system
33 ACCUTRACACCUTRAC SYSTEMSYSTEM
WORKING CAST & SEPARATE DIE
SYSTEM
Here, two casts are poured from a single impression and one cast is Here, two casts are poured from a single impression and one cast is
sectioned and used as a die and the other is not sectioned and is used sectioned and used as a die and the other is not sectioned and is used
as the working cast. The wax pattern is prepared on the die and later as the working cast. The wax pattern is prepared on the die and later
transferred to the working cast. The die is shaped and finished using an transferred to the working cast. The die is shaped and finished using an
acrylic trimmer and the portion of the die below the cervical line is acrylic trimmer and the portion of the die below the cervical line is
finished using a scalpel. Sharp undercuts in the base should be finished using a scalpel. Sharp undercuts in the base should be
avoided.avoided.
ADVANTAGEADVANTAGEADVANTAGEADVANTAGEADVANTAGEADVANTAGEADVANTAGEADVANTAGE
Simplest and easiest method
DISADVANTAGEDISADVANTAGEDISADVANTAGEDISADVANTAGEDISADVANTAGEDISADVANTAGEDISADVANTAGEDISADVANTAGE
The wax pattern may get distorted while transferring it from the die to
the cast.
Proximal margins tend to get overcontoured.
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WORKING CAST WITH A
REMOVABLE DIE SYSTEM
InIn thisthis systemsystem aa specialspecial typetype ofof workingworking castcast isis preparedprepared andand thethe diesdies
areare carefullycarefully sectionedsectioned soso thatthat thethe individualindividual diesdies cancan bebe removedremoved
andand replacedreplaced inin theirtheir originaloriginal positionposition inin thethe castcast.. DowelDowel pinpin
systems,systems, didi--loklok traytray systemssystems andand thethe pindexpindex systemssystems comecome underunder
thisthis categorycategory..
DOWEL PIN SYSTEMSDOWEL PIN SYSTEMSDOWEL PIN SYSTEMSDOWEL PIN SYSTEMSDOWEL PIN SYSTEMSDOWEL PIN SYSTEMSDOWEL PIN SYSTEMSDOWEL PIN SYSTEMS
Dowel pins may be straight or curved:
1. STRAIGHT DOWEL PIN SYSTEMS
They are prepared using two techniques,
namely
the pre-pour and post-pour techniques.
PRE-POUR TECHNIQUE
Here the die pins are positioned in their
appropriate places within the impression using
bobby pins and sticky wax.
The dowel pin is positioned within the
impression using sticky wax
After positioning the pins, the impression is
poured up to the level of the alveolar process
of the remaining teeth. First pour is poured upto the level of the alveolar process
Separating medium is applied over the first
pour and die pin and the remaining portion of
the cast is poured. Separating medium is applied and the base is poured
After the cast is set, the dies are sectioned by After the cast is set, the dies are sectioned by
placing vertical sections on the placing vertical sections on the interproximalinterproximal regions regions
of the cast using a die of the cast using a die sectionersectioner or a manual saw. or a manual saw.
Vertical sections at the inter- proximal regions Vertical sections at the inter- proximal regions
should be made without damaging the contour of should be made without damaging the contour of
the adjacent teeth.the adjacent teeth.
Since the separating medium was applied before pouring the Since the separating medium was applied before pouring the
second half of the cast, the dies can be easily separated with second half of the cast, the dies can be easily separated with
vertical sections alone.vertical sections alone.
The die is carefully separated from the cast without chipping. After The die is carefully separated from the cast without chipping. After
removing the die, a small hole will be visible in the cast. This indexing removing the die, a small hole will be visible in the cast. This indexing
hole will guide the pin into position while replacing the diehole will guide the pin into position while replacing the die.
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POST-POUR TECHNIQUE
Here, the cast is poured Here, the cast is poured uptoupto the level of the the level of the
crowns of the teeth in the impression. crowns of the teeth in the impression.
Subsequen-tly, small holes are drilled within Subsequen-tly, small holes are drilled within
the first pour in the required places and the the first pour in the required places and the
dowel pins are cemented into the holes The dowel pins are cemented into the holes The
remaining part of the cast is poured and the remaining part of the cast is poured and the
dies are sectioned as described in the predies are sectioned as described in the pre--
pour technique.pour technique.
ADVANTAGES
Easy to prepare
No special equipment is necessary
DISADVANTAGES
The pins may get displaced while pouring the cast.
2. CURVED DOWEL PIN SYSTEM2. CURVED DOWEL PIN SYSTEM2. CURVED DOWEL PIN SYSTEM2. CURVED DOWEL PIN SYSTEM
This is similar to straight dowel pin technique except that curved pins This is similar to straight dowel pin technique except that curved pins
are used. The curved pins will project from the sides of the base of the are used. The curved pins will project from the sides of the base of the
cast. When the projecting pins are pressed, the die unit attached to cast. When the projecting pins are pressed, the die unit attached to
the respective pin will pop out from its place.the respective pin will pop out from its place.
Curved dowel pin system (pushing the pin from the side pops the die out).
B) DI-LOK TRAY SYSTEMThis technique uses a special tray to pour the cast. This special tray has
orientation grooves on the inner aspect. Actually the tray is made of multiple
components, which can be assembled or dismantled as required (Fig. 33.7).
Impression is poured using a two-pour technique. The first pour is poured up
to the level of the impression and the second or base pour is poured after
positioning the rim of the di-lok tray over the impression. Before the second
pour is set, the base of the di-lok tray is assembled and the cast is allowed to
set. Later, the di4ok tray is dismantled and the grooves on the base of the cast
formed by the di-lok tray is used as a guide to do die sectioning.
ADVANTAGES
Simple and easy to prepare
The cast can be mounted in an articulator
DISADVANTAGES
Requires special equipments.
C) PINDEX SYSTEM
This system is similar to the postThis system is similar to the post--pour dowel pin technique. Here a special drill pour dowel pin technique. Here a special drill
press equipment is used to do die sectioning. The drill press has a platform with a press equipment is used to do die sectioning. The drill press has a platform with a
slot like opening through which the drill pin will project during the procedure. The slot like opening through which the drill pin will project during the procedure. The
entire platform is spring mounted and when pressed down automatically starts entire platform is spring mounted and when pressed down automatically starts
the drill, which will project through the slot. The unit has a red pilot light lamp on the drill, which will project through the slot. The unit has a red pilot light lamp on
top, which will shoot a point exactly on the drill. This red pilot pointer will act as a top, which will shoot a point exactly on the drill. This red pilot pointer will act as a
guide while drilling (Fig. a).guide while drilling (Fig. a).
Fig - guide to drill holes in the base of the cast. The
platform of the pindex machine is spring loaded. When
the cast is passed against the platform, the motor will
get activated and drill a hole in the casta. The cast is
placed on the pindex machine and the pilot light is used
as a
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Die sectioning procedure is simple wherein the cast Die sectioning procedure is simple wherein the cast
of 15 mm base is placed on the drill press and drill of 15 mm base is placed on the drill press and drill
holes are prepared in the under surface of the base holes are prepared in the under surface of the base
of the cast using the pilot light as a guide. After of the cast using the pilot light as a guide. After
making the drill holes to the required depth, sleeved making the drill holes to the required depth, sleeved
die pins are placed and cemented using die pins are placed and cemented using
cyanoacrylatecyanoacrylate adhesive. Remember that the holes adhesive. Remember that the holes
will not be very deep. Hence a portion of the pins will will not be very deep. Hence a portion of the pins will
be projecting from the base of the cast.be projecting from the base of the cast.
After cementing the pins, a base is poured over the base of drilled After cementing the pins, a base is poured over the base of drilled
cast. Consecutively the dies are sectioned but not cast. Consecutively the dies are sectioned but not uptoupto the base as the base as
described in the dowel pin system.described in the dowel pin system.
ADVANTAGES ADVANTAGES ..
Allows accurate placement of the die pins.Allows accurate placement of the die pins.
DISADVANTAGES .DISADVANTAGES .
Special equipment is required.
THE ACCUTRAC SYSTEM
These dies are exclusively used in the fabrication of These dies are exclusively used in the fabrication of
laminate veneers. Basically this system involves the fabrication of laminate veneers. Basically this system involves the fabrication of
two casts as described in the working two casts as described in the working castwithcastwith separate die system. separate die system.
One cast (master cast) is sectioned into dies and used to prepare One cast (master cast) is sectioned into dies and used to prepare
the coping. After preparing the wax pattern, the sectioned dies are the coping. After preparing the wax pattern, the sectioned dies are
reassembled in the master cast.reassembled in the master cast.
TheThe mastermaster castcast isis blockedblocked outout withwith waxwax (filled(filled withwith waxwax toto
sealseal thethe crevices)crevices).. TheThe secondsecond castcast (refractory(refractory cast)cast) isis
duplicatedduplicated fromfrom thethe blockedblocked out,out, sectioned,sectioned, diedie mastermaster castcast
usingusing additionaddition siliconesilicone.. TheThe secondsecond castcast isis pouredpoured usingusing
speciallyspecially formulatedformulated stone,stone, whosewhose expansionexpansion willwill
compensatecompensate forfor thethe shrinkageshrinkage ofof porcelainporcelain whenwhen firedfired inin thethe
furnacefurnace..
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