10/9/2013

1

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.

10/9/2013

2

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.

10/9/2013

3

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.

10/9/2013

4

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

10/9/2013

5

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..

10/9/2013

6