Dr. Dwij Kothari

Darshan Dental College & Hospital

Definition

Basic properties of die materials

Materials used for making dies

• Gypsum products

• Die stone

• Electroformed dies

• Epoxy resins

• Polyurethane

CONTENTS

• Silicophosphate cement

• Amalgam

• Metal sprayed dies

• Refractory die materials

• Flexible die materials

Compatibility with impression materials

Comparisons of the various die materials

Cast & die systems

• Working cast with removable die

o Straight dowel and Curved dowel pin

o Di – Lok tray

o Pindex system

o Accutrak system

• Solid cast with individual die

o DVA model system

o Zeiser model system

Preparation of the die for wax patterns

Review of literature

Summary and conclusion

References

introduction

An accurate working cast with removable dies is

essential to make a well fitting restoration.

Detailed reproduction of die materials for fixed

prostheses affects the accuracy of working casts and

is related to the compatibility between the die and

impression materials.

A working cast is the replica of the prepared teeth,

ridge areas and other parts of the dental arch.

DEFINATION

Die :- It is the positive reproduction of the form of

the prepared tooth in any suitable substance.(GPT-8)

Cast :- A life-size likeness of some desired form. It

is formed within or is a material poured into a

matrix or impression of the desired form(GPT-8)

Dowel pin:- A metal pin used in stone casts to

remove die sections and replace them accurately

in the original position(GPT-8)

Die spacer An agent applied to a die to provide

space for the luting agent in the finished casting(GPT-8)

MATERIALS USED FOR MAKING DIES IN FIXED PARTIAL PROSTHESIS

1. Gypsum products- Type IV Dental Stone

Type V Dental stone

2. Die stone-Investment combination

3. Electroformed dies- Silver plated

Copper plated

4. Epoxy resins

5. Polyurethane

Alternative die materials

6. Silicophosphate cement

7. Amalgam

8. Metal sprayed dies

9. Flexible die materials

10.Refractory die materials

BASIC REQUIREMENTS OF DIE MATERIALS

They should accurately reproduce all fine details in

the impression.

It should be reasonably easy to use.

They should be dimensionally stable. Setting

expansion, contraction and dimensional variation in

response to setting or change in temperature should

be minimal.

The die should have a smooth surface that is

sufficiently strong to withstand the abrasion of the

surface

They should be compatible with impression materials

and there should be no interaction between the

surface of the impression and cast or die.

Toughness to resist breakage during fabrication or

burnishing of fine edges.

Colour of the die should be in contrast to the colour

of wax. This helps to facilitate the manipulative

procedures that will be carried out.

GYPSUM PRODUCTS

It is a mineral mined in various parts of the world

chemically the gypsum produced for dental

applications is pure calcium sulfate dihydrate

[CaSO4.2H2O].

Gypsum products are available in five forms (ADA

Type I-V)

Type I- Impression plaster.

Type II- Model plaster.

Type III- Dental stone.

Type IV- Dental stone with high strength.

Type V- Dental stone with high strength and high

expansion.

CaSO4 • 2H2O CaSO4 •½H2O +1½H2O

(Gypsum) (calcium sulphate hemihydrate)110-130

Degree C

MANUFACTURING PROCESS

Calcination reaction

Gypsum

Heated for partial dehydration

Open air Autoclave

Beta hemihydrate

(type I and II )

Alpha hemihydrate

(type III, IV, V)

Gypsum is ground and subjected to temperature of 110o to

120oC to drive off the water of crystallisation

Gypsum

110-130 degree C

In autoclave

Boil with 30% CaCl2 or MgCl2

Or

0.5 - 1% sodium succinate

Alfa hemihydrate

calcium sulfate dihydrate

Setting reaction results from the hydration of

calcium sulfate hemihydrate:

CaSO4 • ½H2O +1½H2O CaSO4 • 2H2O + heat

(3900 cal/gm)

Properties

Type IV Type V

Water powder ratio 0.22-0.24 0.18-0.22

Setting expansion 0.1% 0.1 to 0.3%

Compressive strength 5000psi 7000psi

Advantage of gypsum as die material

Compatibility with all impression materials

Easy to use

Dimensionally stable

Inexpensive

Disadvantage of gypsum dies

Susceptibility to abrasion

Brittle prone to fracture

Methods to increase abrasive resistance

Substitution of colloidal silica for water.

Treat surface with resin (epoxy, acrylic, styrene or

cyanoacrylate)

Impregnating acrylic resin into stone die.

(compressive strength-7,000 psi)

Colloidal silica: It increases resistance to

surface abrasion but there is little increase in

setting expansion, which is minor.

Low viscosity resins i.e. cynoacrylate, which is

used to impregnate the die surface, care is taken

while applying it so as to produce uniform

thickness.

In order to improve the properties of dental stone:

1. Gum arabic.

2. Calcium hydroxide mixture.

3. Resin strengthened gypsum products such as Resin

Rock with high strength and low expansion

(particularly for implant casts).

4. Incorporation of wetting agents such as

lignosulphonates reduce water requirement of a

stone harder, stronger, dense set stone

CAD Stone is Type 4 die stone formulated

especially for use with CAD/CAM systems. It

has high compressive strength, low expansion,

and an extended working time, enabling the

pouring of multiple impressions.

• PRIMA-

ROCK has

the highest

compressive

strength

(8,000 psi)

of any Whip

Mix die

material.

Compatible with all types of impression materials. Its high expansion makes it

especially suited for polyvinyl or polyether impression materials.

Facilitates multiple pours

DIE STONE INVESTMENT COMBINATION

Commercial Gypsum Bonded Materials:-

1. The divestment is mixed with colloidal silica

liquid.

2. Die is made & wax pattern is constructed on it.

3. This entire unit is invested in mixture of

divestment & water, thereby eliminating the

possibility of distortion of pattern on removal from

the die.

4. When heated to 677ºC,

- Setting expansion – 0.9%

- Thermal expansion – 0.6%.

5. Not recommended for high fusing alloys.

6. Highly accurate technique for conventional gold alloys

especially intracoronal preparations.

AMALGAM DIES

1. They are made by packing amalgam into

impression made of impression compound.

2. Dies made of amalgam exhibit superior strength,

resistance to abrasion & reproduce fine details &

sharp margins.

Disadvantages:

Can only be packed into a rigid impression .

Long time to reach a maximum hardness.

High thermal conductivity hence can cool a wax

pattern rapidly which can lead to distortion of the

pattern.

This can be overcome by warming the die, a separating

agent is needed as with stone dies.

SILICOPHOSPHATE CEMENT

• The powder is a mixture of silicate powder & zinc

oxide & liquid contains phosphoric acid.

Advantages:-

Strength & surface hardness superior to those of

die stone.

Disadvantages:-

1. Material contracts during setting & may be

dimensionally inaccurate.

2. Loss of water on standing since viscosity is

relatively high.

3. Presence of surface voids can occur.

.

Resins

Self curing acrylic - epoxy resins, polyesters.

Epoxy resins : are used as die materials to overcome

the low strength and abrasion resistance of die stones.

The fast setting epoxy hardens rapidly so that dies can

be waxed up in half an hour after injecting into the

impression.

Properties

Working time – 15 min

Setting time _ 1-12 hrs

Shrinkage _ 0.03%-0.3%

Compressive strength – 9500-14200psi

Hardness _ 83RHN

Disadvantages

1. Cannot be used with water containing agar and

alginate impression material.

2. Shrinkage on polymerization.

3. Less dimensional stability.

4. Expensive.

5. Prone to trap air in preparation

Philip duke, Steven Haug and Carle Andres exhibited several

physical properties that may be superior from a clinical point of view.

•The epoxy resin exhibited much better detail reproduction, abrasion

resistance, and transverse strength than the gypsum materials.

•However, its setting shrinkage compared with the expansion

observed with gypsum die materials may require modifications in

technique to obtain castings that will be well adapted to the tooth

preparation.

Philip Duke, B.K eith Moore, Steven P. Haug and Carle J. Andres Study of the physical properties of type 4

gypsum, resin-containing, and epoxy die material J Prosthet Dent 2000;83:466-73

Metal sprayed dies

Bismuth alloy with fusing point of 136ºF is melted by

placing at constant temperature held at 145ºF. Die is

poured & solidify at 30 pounds of pressure.

Advantages :

A metal coated die can be obtained rapidly from

elastomeric impression materials.

Disadvantages :

Alloy is soft, care is needed to prevent abrasion of the

die.

Electro deposition of metals:-

Can produce detailed reproduction up to 30µm.

Have moderately high strength, adequate hardness &

excellent abrasion resistance.

Basic system consists of:-

- An electrolyte solution

- A source of direct current.

- An anode – pure copper

- pure silver

“Metalizing”:- The surface of the impression is coated with a

conductor of electricity such as graphite, copper powder or silver

before it is attached to the cathode lead wire.

COPPER PLATING OR COPPER FORMED DIES :

General technique:

Electrolyteacid solution of CuSO4+organic constituents

Coated impression cathode of a plating bath

With an anode of copper.

Surface is rendered conductive particles of copper or graphite

Dental stone is then cast into plated impression: when stone has set, the metal covered die can be removed from the

impression.

A current is passed (5-50mamp/cm2 of cathode is applied for 10-12 hrs)

SILVER FORMED DIES : (SILVER PLATING)

For silver plating - Polysulfides & Silicone impressions are used.

Cleaning & drying the impression.

Metalize the area to be plated with a fine silver

powder by burnishing it with a sable brush.

- Various metalizing agents are:-

- Bronzing powder.

- Aqueous suspension of silver powder.

- Powdered graphite.

Insert cathode wire in the border of

impression in the metalized area

Fill preparations & the teeth with

electrolytic solution

Completely submerge the impression in

plating solution. The silver anode immersed

in the solution should be at least equal in

size to the area of the surface to be plated.

• Proceed plating initially at approx. 5mA per tooth for

1hr and check for even deposition of metal and make

certain there are no voids.

• Resubmerge the impression in plating solution &

plate it for approx. 12hrs. at 10mA per tooth.

• Wash and dry impression and use dental stone.

Problems in Electroplating :

1. Silver cyanide solution is extremely dangerous, it

contacts acid & produces fumes of extremely toxic

hydrocyanic acid.

2. These dies are not significantly more or less accurate

than stone dies.

3. The possibility of continued polymerization &

distortion of impression during electroplating may

lead to a clinically significant dimensional change in

the impression.

4. Friable metal deposit if current set too high.

5. Silicone difficult to electroplate, because of low

surface energy.

6. Polyether cannot be plated accurately, since it

imbibes water.

7. Polysulfide can be silver plated but difficult to copper

plate.

Flexible Die Materials:-

- Similar to heavy bodied silicone or polyether impression material.

Use:-

- To make provisional restoration.

- Indirect composite resin inlays or onlays chairside

- Maryland bridges.

Advantage:-

- More rapid setting – 10min.

- Ease of removal of provisional restoration.

Douglass Smith, Arun Nayyar, David L. Koth - Fabrication of removable dies using cemented dowel pins J

Prosthet Dent: 1992:68:372-4

While fabricating of removable dies - Douglass used

polyvinyl as cast, that may be flexed to remove the

polymerized resin from the undercuts on adjacent teeth

or from the die.

Procedure:

Procedure involves :-

• Make a preoperative mold of the tooth/teeth to be

prepared, including the adjacent teeth. This can be

either a custom thermoplastic form made from a

diagnostic cast or an elastomeric impression made

directly in the patient’s mouth.

Irreversible hydrocolloid impression

Fill with the fast setting, medium

viscosity polyvinyl impression material

Place the polyvinyl cast into

the pre operative mold

Custom made thermoplastic crown form is filled with auto

polymerizing resin and is seated on the flexible cast.

The polyvinyl cast is flexed to

remove tooth colored resin from the

undercuts.

Interim restoration on the prepared

tooth

A low viscosity polyvinyl siloxane

duplicating material is used to

reproduce dies

Adapt a strip of putty around the prepared teeth on working cast and

dies to limit the flow of mold material.

Refractory Dies:-

These are made for preparation of all ceramic restorations.

Advantages – Excellent marginal adaptation

• To avoid air entrapment, fill the putty reservoir by

pouring the mix.

• The duplication material should be at least 3.00mm

thick and it should extend 3 mm beyond incisal edges of

teeth to provide adequate support refractory material.

• The duplicating material is allowed to set for about 30

minutes.

• By applying pressure on base of tray, master cast is loosened with duplicating material intact.

• The master dies removed from cast and duplicating material.

• The refractory material is poured and vibrated in the area of missing dies.

• Allow the refractory dies set for about 1-2 hours.

Technical considerations of refractory die material

• Recommended powder liquid ratio must be followed

since it may cause uncontrolled expansion or, shrinkage

during setting and possibly a weakened die.

• Wax burnout furnace – up to 700°C for degassing to

eliminate sulfur and ammonia gases and then ceramic

furnace – up to 1080°C in vacuum.

• Cooled down at room temperature

• Application of die sealant

i.e. Application of 2 thin wash of half glaze, half dentin

porcelain to prevent porous die material to absorb water

from porcelain & fire.

Compatibility with impression materials :

Dental stone -Impression compound

-Zinc oxide eugenol

-Alginate

-Impression plaster when

used with separator

-Rubber base material

Electroplated Cu - Impression compound

Electroplated silver - Polysulphide

- Rubber base material

Epoxy Resin - Rubber base material

Comparisons:

If a release agent is not needed on the surface of the impression,

epoxy dies reproduce detail the best(10µm)

Followed by silver plated dies (30µm)

Then the stone dies (170µm)

However a polysulphide impression requires the use of a release

agent with epoxy dies and their reproduction of detail is

comparable to that of the stone die

Silver plated dies have superior resistance to abrasion , epoxy

dies have good resistance and stone dies have the least

Materials Advantages Disadvantage Use Precaution

ADA TYPE 4

stone

• Dimensional

accuracy

• Straight

forward

technique

• Low cost

Low abrasion

resistance

Most

situations

Accurate

proportioning

essential

ADA TYPE 5

stone

•Straight

forward

technique

• Low cost

•Improved

strength than

type4

Increased

expansion

Most

situations

Accurate

proportioning

essential

Materials Advantages Disadvantage Use Precaution

Electroplating High strength

Good abrasion

resistance

•Time

consuming

Complete

ceramic

crowns

•Silver uses

toxic cyanide

•Incompatible

with many

impression

materials

Epoxy resin •High strength

•Good abrasion

resistance

•Polymerization

shrinkage

• Time

consuming

complex

procedure

Complete

ceramic

crowns

Not

compatible

with

polysulfide

and

hydrocolloid

Die Hardener

Materials applied on the surface of die to

increase the surface hardness.

Should have low viscosity

Commonly used materials as die

hardeners:

Cyanoacrylate resins (Eg: Premabond)

Acrylic resin lacquer (Eg: Die Prep die hardener)

Applied to finish line area of the die to prevent

abrasion by waxing instruments during the fabrication

of wax pattern

Applied with brush or PKT instrument no 1.

Quickly blown off and dried from above the margin

toward the cervical area.

or

Blot with tissue

Optimal Thickness 2-3 micro m, but if not properly

manipulated10 micro m (JPD 1991;65;713)

Air blowing or blotting the excess with tissue, decreases

the film thickness of die hardener to 1 micro m

Hisao F Effectiveness of hardening films on die stones. JPD 1980;44;57.

Lacy AM et al (JPD1980:44:356) concluded that

Cyanoacrylate resins and resinous die hardeners

effectively improved the hardness and abrasion resistance

of stone dies.

Application of liquid resins followed by blotting and/or

blowing with compressed air produced an improved

surface without clinically significant dimensional change.

The extent of film build up was qualitatively related to the

viscosity of the resin.

Application of multiple coats of resin without further

blotting or other mode of removal of the excess produced

a thick film which can obliterate surface detail .

Paul E. Harris et al (JPD 2004;92;35) compared the

surface micro-hardness of type IV and type V gypsum

materials with and without surface die hardeners

(Premabond 910 & Clear coat) . They concluded that die

hardeners evaluated did not increase the surface hardness of

gypsum materials, but they actually decreased the surface

hardness.

Paul E. Harris Alteration of surface hardness with die hardener. JPD 2004:92;35.

Die Spacer :-

An agent applied to a die to provide space for the

luting agent in the finished casting.

Types of die spacers :

Resins

Paint or liquids

Model paint

Coloured nail polish

Thermoplastic resins dissolved in volatile solvents.

Optimal thickness

20-40 micro meter (Acc. to rosenstiel 4th edi. Pg 557)

Rudd and Morrow – 10-15 micro meter

Fusayama et al (JPD 1964;14;95)-thickness should not be less

than 30 micro meter

Jorgensen et al (JPD 1966:16;740) variations of thickness from

20-140 micro m had only moderate influence on retention.

Eames et al (JADA 1978;96;432) – optimal thickness - 25 micro

meter

Should flow uniformly

and smoothly

Color should be readily

identifiable on the die

Thinners are available to

decrease the viscosity of

die spacer.

Should be applied

0.5-1mm short of margin

Brush strokes in one direction

Wait for 2 mins before

applying next coat

W.G. Campagni at al (JPD 1982;47;606) Did a

study on measurement of die spacers used for casting relief

and concluded that measurements of thickness of

commercial die spacers were not consistent with those

reported by the manufacturer.

Tjan et al (JPD 1981;46;399) found that grooves

significantly inhibit the seating of castings, presumably

by acting as small hydraulic cylinders during cementation

process. Therefore application of spacer in groove is

essential.

Terry D et al (JPD 1982;47;606) concluded that

grooves should not be die spaced because intimate

adaptation of the casting to the tooth is essential to achieve

optimum resistance and retention, and the die spacer may

tend to pool in the groove and hence obliterate much of the

critical detail.

W.V. Campagni et al (JPD 1986;55;324) concluded

that grooves did not disrupt seating when die spacer

application was specifically omitted from grooves.

PEEL-AWAY DIE SPACER

Following crown fabrication easily removed and a

final check for fit is made on the original clean die.

25 microns of space.

Advantage:

Eliminates see-through of undesirable die spacer color

under all ceramic crowns

Allows true verification of fit to the original die form

Die Spacer Pens (Kerr Laboratory)

Poly fiber disposable tip.

die lub

Die Separator

The lubricants or die separators which can be used to

prevent wax from adhering to stone are oils, liquid soap,

detergents and a number of commercially available

preparations.

Die Separator

Easy removal of wax pattern

without damaging margins.

Applied with brush

Excess to be removed with

tissue paper

Eg: Kleen lube (Kerr)

Picosep (Renfert)

Dielube wax sep(Dentecon Inc.)

Cast & Die Systems

CONTENTS

Die systems

Working cast with separate die

Working cast with removable die

Conventional dowel pin system

Di-lok

Pindex

DVA

Belle de st. Claire

Zeiser

Accu-trac system

Mono trac

Working cast with separate die

Simplest method of

fabrication

Advantages:

Easy to fabricate

Keeps relation between

abutments fixed

Better contours and

emergence profile while

wax pattern fabrication.

Disadvantages:-

Wax pattern must be transferred from die to cast

destroy internal adaptation of wax

Some times difficult to seat wax pattern on the cast

- Different impressions

- Second pour –impression damaged

- Different thickness of spacers

Procedure:-

Both working cast and sectional die can be obtained by:

- Pouring impression twice

- Making two impressions

Preparation of separate die

Stone added to side

of impression in small

increments

Tray tilted to fill the

Impression displacing

air as it moves

Add stone in small

increments

If large amount of stone

dropped into preparation

or

If two sizable masses of

stone meet

Air trapped voids

• Build to height of approx 1 inch

Pour stone to receive

working cast

Make base

Retrieve cast

Trim sectional cast

Octagonal in shape

Sides parallel or slightly

taper towards base

Handle 1 inch long

Pear shaped acrylic bur

trimmed apical to finish line

Final trimming sharp blade

Smoothened

Contour be approximately like root

To facilitate good axial contours in

restoration

Sharply undercutting thick

gingival areas, improper axial

contours

Finish line highlighted with red

pencil

Not to use black graphite pencil

Apply die spacer

Fabrication of FPD

Die of each part is left

joined to each other by

means of common base

Edentulous ridge area

cut back

Philippe A. et al (IJP 1993:6;533) compared 2 removable

die systems (Zeiser system (Girrbach Dental), Pindex

(Coltene-Whaledent) and working cast with separate die.

They concluded that the Zeiser system was the most

accurate of the three systems studied, followed by

working cast with separate die.

WORKING CAST WITH REMOVABLE DIE

Advantage:

Convenient to use

Various drawback of separate die are

overcome

Disadvantage:

Risk of introducing error in the

pattern if die does not seat accurately

in the working cast

Requirements:

1) Dies must return to their exact original position

2) Dies must remain stable even when inverted

3) Cast containing dies must be easy to mount on an

articulator

Systems using die pins

Methods of repositioning die

in its working castSystems using pre formed

plastic trays without die pins

Pre pour technique Post pour technique

Devices are oriented

in the impression

before it is poured

Attached to the underside

of the cast that has already

been poured

Systems using die pins

Conventional dowel pin systems

Dowel pin (GPT 8): a metal pin used in stone

casts to remove die sections and replace them

accurately in the original position

Straight Curved

Straight dowel pin

Flat sided

dowel

Double straight

dowel with

common head

(Bi pin)

Rounded single

dowel pin

BI-PIN with case

BI-FIXED-pin

Doubles straight dowel

with fixing wire for

accurate positioning

in impression

Procedure

(Pre pour technique)

Marking to act as

guide in placement

of pins

Positioning of dowel pins

A)

Mann paralleling instrument

Clamps holding

Dowel pins

(33)

C)

• Disposable anesthetic needles

D) Straight pins with modeling clay

E) Matchsticks (JPD 1975;34;467)

F) Bobby pins(1)

Die stone poured into

impression filling the

impressions of teeth and

covering the knurled end of

the dowel pin

V- shaped orientation

grooves made

Separating media-area

adjacent to each dowel pin

Small wax ball placed

on tip of each dowel

Boxing done

Base formed

Curved dowel pin

Positioning bar

Stone poured covering

heads of dowel and

1-2mm of body of dowel

Orientation grooves made

Using metal strips (JPD 1996;35;231)

Thin metal strips (0.001

gauge) were carefully

wedged in the impression

Placement and tapering

of matrix band

Matrix band kept parallel

in case of multiple

preparations

2 mm of band exposed

Post pour techniques

Fabrication of removable stone dies using cemented dowel

pins

(JPD 1979;41;579)

Pour cast- minimum height

from border -10 mm

Trim borders-U shaped

outline B-L width 15 -20mm

Horizontal line - 10mm from

lowest portion of edentulous

ridge

(4-5mm mesial and distal to

prepared teeth)

Draw vertical parallel lines

to indicate common path

of removal of all die

segments.

Draw broken lines dividing into half

Orientation grooves

Di lok tray system

(Di –Equi Dental products Co)

Snap apart plastic tray with internal orienting

grooves and notches to reassemble the working

cast and die.

Before using check for space in articulator

Cast poured1inch height

No stone in lingual area

Trim to fit Di lok tray

Horizontal grooves

Fill tray ¾ with stone

Seat the cast cervical area

of teeth be about 4mm above

the edge of tray

Disassemble the tray

Cut till ¾ length

PINDEX SYSTEM

(Coltene / Whaledent)Light beam

director

Drill hole

Work table

Handle bar

Motor housing

Bottom should be flat to ensure

that the Pins will be parallel Faciolingual width – 20 mm

Two pins for each die

Two for each pontic area

One /Two pins in each

terminal segment

containing unprepared

teeth

Round parallel side brass pins (15mm, 10mm)

Collar of pin should flush with base of cast to avoid

creating an undercut

Shorter pins on lingual side

Longer on buccal side makes the ends of the dowel

pins more accessible for easy removal after the casts

are mounted.

Strip of utility wax along ends of

long pins

Ball of wax on isolated pins on

contralateral side

Ends of shorter sleeves place wax

Pinned cast can be removed from base in one piece

sectioning of cast from underside.

(limited interdental space possibility of damaging

finish line.

DVA System

Pre manufactured base system

Two tapered round brass pins per die - 7mm

Impression on alignment fixture

Secured with putty

Marking dowel pin locations

On clear plate with twin tip

marker

Drill holes for dowel pins

Using drilling pressInsert dowel pins

Impression is poured and stone

is placed around dowel pinAlignment fixture is replaced over

poured impression

Set cast is removed from

baseplate with gentle tappingCast is trimmed

Cast is sectioned Definitive cast trimmed with

DVA model system

Zeiser model system

(Girrbach dental Gmbh, Germany)

(14,17)

Impression leveled, blocked out

with silicone putty

positioned over the base

Pin locations determined Pin holes drilled in base

Pins inserted into base Impression is poured

Base inverted The cast is separated

from the impression

Belle de st. claire

Round slightly tapered S.S. dowel pins15 mm long

Flat surface and plastic indexer positive lock

retention and anti-rotational Feature.

Holes pindex system with drill available with

the system

Plastic indexers

Accu- Trac Die Precision System

-

(Coltène Whaledent)

(14,17)

Place the impression on the

precision base and adjust,

so that it is centered and

horizontal.

Place die stone in the

impression and in the

base of tray

Open the retaining

arms to remove the

model

Monotrac Articulation

Vertical single pour base (VSP)

Pour stoneSpray silicone spray on VSP

Cones.

Separator on stone

Trim impression –fit the

base molds

Pin –act as guide for placement

Remove base mold

and impression

VSP base removed by tapping

Sectional impression

Dies for CAD CAM systems

CEREC SYSTEM

(Sirona Dental System,

Germany)

Intraoral camera to take optical impression of the

preparation

Preparation covered with opaque powder

( Titanium dioxide )

Image as

viewed on monitorCavity outlines are identified for

formation of future restoration

Cerec milling unit

Procera all ceram system

(Nobel Biocare)

Scanning of the die

Scanner probe with a

ball tip

Light pressure of about

20 gms

Elevated by 200 micro meter

Displayed image

Spacer thickness programmed designing of the restoration

done

Soft Tissue Masque

Sawing of model for separation of dies and ditching the die

(to reveal preparation margins) removes critical anatomy

which would help guide the creation of optimal restoration

contours.

1. No guide left for axial contours

Overcontouring tissue impengement

and poor accessibility for oral hygiene

plaque buildup Inflammation

Undercontouring unesthetic opening of

interproximal spaces

2. No proper emergence profile

TECHNIQUE

Elastomeric impression of

untrimmed cast made

Pink polysiloxane material

(Gi-mask,Coltene)placed

in putty index

Impression with silicone

material placed on the

working cast

Cast with soft tissue mask

REVIEW OF LITERATURE

Gerald T Nomura et al J Prosthet Dent 1980:44:1:45

evaluated the accuracy, fit, detail registration and Knoop

hardness of 3 commercially available resin die systems

• The control used was improved stone

• Impressions were made of each MOD and complete

crown preparation

• A total of 80 dies were obtained

• 40 die registrations were also made , 10 of each material

• 4 dentists were selected to see the master castings on

each die and to evaluate it as fit or non fit

The fit of each casting was confirmed by seating it on the die

upon which the wax pattern was made

The author concluded that

1. Complete crown epoxy resin dies are undersized

2. MOD onlay epoxy resin dies are accurate

3. Detail duplication of epoxy resin dies is comparable to die

stone

4. Hardness values of epoxy resin are less than those of stone

E. Ricardo Schwedhelm et al J Prosthet Dent 1997;78:554-9

Study evaluated the fracture resistance of 4 die stone materials at

different time intervals.

Additional silicone impressions were made of a maxillary master

cast.

Two Type V, one Type IV die stones and one Type IV resin

reinforced stone were tested. A total of 80 casts were prepared,

separated, and tested on the Instron Universal Testing Machine at

1/2, 1, 12, and 24 hours to measure resistance to fracture.

Significant differences to fracture resistance of the different die

stone materials were observed at all time intervals except at 24

hours. Type IV resin gypsum product was the only material that

really benefits by waiting 24 hours for the cast to set.

Conclusion: It is recommended to wait at least 12 to 24

hours when separating casts from impressions to avoid

casts from fracturing.

It is possible that residual moisture in the stone cast

may be concentrated near the preparation and may

affect the strength of die stone.

Lawrence G. Breault etal J Prosthod 1998;7:13-16 conducted a

study were in Substitution of a 5.23% solution of sodium

hypochlorite in place of 10% of the gauging water when mixing a

Type V stone.

Conclusion: resulted in an increased compressive strength and

rigidity and a decrease in setting time. There was no change in

tensile strength, setting expansion, hardness, or detail

reproduction.

Incorporation of sodium hypochlorite in the gauging water may

be an effective, convenient, and inexpensive method of

disinfecting gypsum casts in the laboratory without adversely

effecting physical and mechanical properties. However, there

may be a reaction between sodium hypochlorite and base metal

alloys.

Alvin G. Wee, C. Cheng and Ryan N. conducted a study to

check an accuracy of 3 conceptually different die systems

used for implant casts.

3 different die systems tested: double-pour (Pindex),

plastic base (DVA), and die tray (KO Tray)

They concluded that the use of a double-pour or plastic

base die system is recommended when sectioned dies are

needed for a multi-implant–retained prosthesis

Alvin G. Wee, C. Cheng and Ryan N. Accuracy of 3 conceptually different die systems used for

implant casts J Prosthet Dent 2002;87:23-9

Conclusions:

A good impression and an accurate die are the first

step towards the fabrication of an accurate restoration

whether its inlay, onlay or crown. Proper selection of the

die material and its manipulation are paramount to

achieve accuracy in the die.

REFRENCES

Anusavice K.J.-“Phillips’ Science of Dental materials” 11th

edition , 2003

Craig’s R.G., Powers J.M. – “Restorative Dental Materials”

11thedition, 2002

Rosenstiel S.F., Land M.F. – “ Contemporary fixed

prosthodontics” 3rd edi. 2001.

Rudd K.D., Morrow R.M. – “Dental laboratory procedures” FPD

2nd edi, 1986.

Dr.Sama Sudharshan Reddy-“Evaluation of the effect of die

spacing on the retention of complete coverage cast crowns,”

2004

Shillingburg H.T. – “Fundamentals of fixed

Prosthodontics.”3rd edition

Anna Belsuzarri Olivera and Tetsuo Saito- The Effect of Die

spacer on Retention and Fitting of Complete Cast Crowns J

Prosthodont 2006;15:243-249.

C, Douglass Smith, Arun Nayyar, David L. Koth-Fabrication of

removable dies using cemented dowel pins J Prosthet Dent:

1992:68:372-4

Alvin G. Wee A nsgar C.Cheng, andRyan N. Eskridge-accuracy

of 3 conceptually different die systems used for implant casts J

Prosthet Dent 2002;87:23-9

Michael A. Mansueto and Rodney D. Phoenix -A

Comprehensive Approach to Die Trimming J Prosthod

1994;3:251-255

Gerald T.Nomura, Morris H. Reisbick, jack D. Preston-An

investigation of epoxy resin dies J Prosthet Dent 1980:44:1:45

Lawrence G. Breault, James R. Paul ,Steven 0. Hondrum, and

hren C. Christensen - Die Stone Disinfection: Incorporation of

Sodium Hypochlorite J Prosthod 1998;7:13-16

Philip Duke, B.K eith Moore, Steven P. Haug and Carle J. Andres

Study of the physical properties of type 4 gypsum, resin-

containing, and epoxy die material J Prosthet Dent 2000;83:466-

73

Dr. Alex Touchstone , Dr. Randy J. Phillips Simplifying

CAD/CAM Dentistry Chair side CAD/CAM designing and

milling are not as complex as they may seem Dental Products

Report (Supplement 1) November 2005

Juan Glen Serrano, Xavier Lepe, John D. Townsend, Glen H.

Johnson, Stephen Thielke-An accuracy evaluation of four

removable die systems-J Prosthet Dent 1998;80:575-86.

E. Ricardo Schwedhelm and Xavier Lepe- Fracture strength of

Type IV and Type V die stone as a function of time J

ProsthetDent 1997;78:554-9.)

Alvin G. Wee, C. Cheng and Ryan N. Accuracy of 3 conceptually

different die systems used for implant casts J Prosthet Dent

2002;87:23-9