DIE AND DIE MATERIALS

GYPSUM PRODUCTS :

Gypsum (CaSo4 2 H2O) is a mineral mined in various parts of the

world however it is also produced as a byproduct of some chemical

processing operations.

Chemically the gypsum produced for ductal applications in nearly

pure calcium sulfate dehydrate.

Production of Calcium Sulfate Hemihydrate :

Plaster and stone are produced by cabining calcium sulfate dehydrate

or gypsum.

The gypsum in ground and subjected to temperatures of 1100 to 1200

C to drive off the water of crystallization and this is the amount of water

needed to convert calcium sulfate dehydrate to calcium sulfate hemihydrate.

CaSo4 2H2O CaSo4 ½ H2O CaSo4 CaSo4

Depending on the method of calcination, different forms of

hemihydrate can be obtained. They are , and -modified hemihydrates.

- hemihydrate is called artificial stone, die stone (or) improved

stone, ti consists of smaller, regularly shaped crystalline particles in the

form of rods / prisms. (fig. 10-2 pg. 258 phillyes).

Irregularly shaped orthorhombic crystals particles with capillary

pores.

(Fig: 10.1 pg. 256 philly)

- modified hemihydrate is made by boiling the gypsum in a 30%

aqueous solution of calcium chloride and magnesium chloride. This process

yields the smoothest, most dense powder particles.

1300 C – 2000 C

1100 C – 1300 C

1300 C – 2000 C

2000 C – 10000 C

Hexagonal anhydrite

Orthorhombic anhydrite

Types of Gypsum products :

The various types of gypsum products identified by ADA are :

1) Plaster, impression

2) Plaster model

3) Dental stone

4) Dental stone high strength

5) Dental stone high strength and high expansion.

Properties of Gypsum products :

Type W/p ratio

Setting

times

(mint)

Setting expansion

after 2 hr.

Compressive

strength after 1

hr.

Mini Maxi Mpa Psi

1) Plaster

impression0.40-0.75 4 1 0.00 0.15 4.0 580

2) Plaster

model0.45-0.50 12 4 0.00 0.30 9.0 1300

3) Dental

stone0.28-0.30 12 4 0.00 0.20 20.7 3000

4) Dental

stone high

strength

0.22-0.24 12 4 0.00 0.10 34.5 5000

5) Dental

stone high

strength

high

expansion

0.18-0.22 12 4 0.10 0.30 48.3 7000

In type III the compressive strength is 20.7 Mpa but it does not

exceed 34.5 Mpa. This is used for the construction of the casts in the

fabrication of full dentures that fit soft tissues.

Stone dies are reproductions of prepared teeth, on or within which

prostheses are constructed. Because of the severe wear conditions that occur

at the margins during carving of the wax patterns and because of higher

stresses induced in stone dies try-in and adjustments, greater strength and

hardness are required of the die materials.

Dental stone, high strength (Type IV) :

The principal requisites for a die material stone are :

Strength

Hardness

Abrasion resistance

Minimum setting expansion.

So -hemihydrate of densite type is used.

It consists of cuboidal – shaped particles.

The reduced surface area due to the shape of the particles produce above

properties without under thickening of the mix.

It gives hard surface as the surface dries more rapidly.

It is resistant to abrasion.

o They are necessary because cavity is filled with wax that in

carved flush with the margins of the die.

o As sharp instruments are used for caring stone must be resistant

to abrasion.

The surface hardness of –

Type IV – 92 Rock well hardness

Where as Type III – 982 Rock well hardness.

Even though the surface of Type IV in hard care should be

observed when the pattern is being carved.

Dental stone, high strength, high expansion (Type IV) :

This type V has compressive strength (48.3 Mpa) higher than that of

Type IV (34.5 Mpa).

This is due to making it possible to lower w/p ratio than Type IV.

The setting expansion has increased from 0.10% (Type IV) to 0.30

(Type V).

The rationale for the increase in setting expansion is that base metals

have greater casting shrinkage than do the traditional noble metal alloys.

Thus higher expansion is required in the stone used for the die to aid

in the compensating for the alloy solidification shrinkage.

Indicated in the cast crowns (when inadequate expansion have been

achieved during the fabrication).

It is not indicated in the production of dies for inlays, since the higher

expansion may lead to unacceptably tight fits.

Propositioning :

The strength of the stone is inversely proportional to the water

powder ratio.

Strength

So amount of water should be as low as possible.

1W/P

It should not be so low that the mix will not flow into every detail of

the impression.

The water volume should be measured by using accurate graduated

cylinder.

The powder should be proportioned by weighing balance.

Powder should not be measured according to volume became powder

varies from product to product and does not pack uniformly.

W/p raio

Type IV : 0.22 – 0.24

Type V : 0.18 – 0.22

MIXING :

1) Hand mixing :

It is accomplished in a flexible rubber or plastic bowl by using

a stiff bladed spatula.

The walls of the bowl should be smooth and resistant to

abrasion.

Incorporation of air during mixing is avoided.

Air bubbles are unslightly, weaken the material and produce

surface in accuracies.

The water should be placed in the mixing bowl and the powder

should be shifted into the water.

When powder sinks into the water without an agglomeration of the

particles, les air is carried down.

The mixing is completed when all the mixture is smooth and

homogeneous in nature.

The further mixing is likely to breakup the crystals of the

gypsum formed and thus weaken the final product.

The time for hand mixing is approximately 1 to 2 month.

Addition of more powder to a mix that is judged to be too thin

provides essentially 2 mixes of stone.

It will set at different times

Results in weakened product.

Addition of water to a too thick mixture causes

Disarrangement of crystalline growth and a lack of intercrystalline

cohesion.

Mechanical Mixing :

The use of mechanical spatulator to mix gypsum products

offers considerable advantage.

Rapidly moving blades of device tend to breakup any air

bubbles into fine voids.

And strength of plaster is increased.

Mechanical mixing time under vacuum approximately 20

seconds.

Setting Reactions gypsum products :

(CaSO4)2 H2O +3H2O 2Ca So4.2H20 + Unreacted (CaSo4)2.1/2 H20

+Heat.

The calcium sulphate heucihydrate powder reacts with the

water and produce the gypsum.

1) When the hemihydrate is mixed with water, a suspension is formed

that is fluid and workable.

2) The hemihydrate dissolves until if forms a saturated solution.

3) This saturated hemihydrate solution, super saturated in dehydrate,

precipitates out dehydrate.

4) As dehydrate precipitates, the solution is no longer saturated with the

hemihydrate, so it continues to dissolve. Dissolution of hemihydrate

and precipitation of dihydrate proceeds as either new crystals form or

further growth accurse on the crystals already present.

The reaction is continuous and continues until no further dihydrate

precipitates out solution.

- The amhydrite is not formed in agueous media.

It is a exothermic reaction, heat is evolved and it is equivalent to heat

used in calcinations.

SETTING TIME

Type IV – 12 4 minutes

Type V – 12 4 minutes.

Control of Setting time :

1) Impurities :

If the gypsum particles remain in the powder.

i.e. if calcination is incomplete

Or if manufacturer adds gypsum

Setting time is shortened because of the increase in the potential nuclei

of crystallization.

If orthorhombic anhydrite is present Induction period increases

If hexagonal anhydrite is present Induction period decreases.

2) Fineness :

The Finer the particle size of the hemihydrate

Rate of hemihydrate dissolution increases

.

Rapid rate of crystallization occurs.

Mix hardens faster.

3) Water powder Ratio :

If more water is used for mixing;

Fewer nuclei are per unit volume;

So the setting time is prolonged.

4) Mixing :

The longer and more rapidly the plaster is mixed,

Gypsum crystals formed immediately when the stone is brought in

contact with water

As the mixing begins, the formation of crystals increases.

During mixing the crystals are broken up and are distributed throughout

the mixture, resulting in the formation of more nuclei of crystallization.

Thus the setting time is decreased.

Retarders and Accelerators :

If the chemical added decreases the setting time, it is known as

accelerator.

If the chemical added increases the setting time, it is known as

retarder.

Retaraders :

Retarders act by forming a layer on the hemihydrate to reduce the

solubility.

Ex : Glue, gelatin, some gums, borax, potassium citrate, concentrated

sodium chloride. (20%).

(If less concentration act as accelerator).

Accelerators

Accelerator that are used mostly are –

Gypsum, potassium sulfate, sodium chloride is less concentrations.

Setting Expansions :

Expansion of the mass can be detected during the change from

hemihydrate to the dihydrate.

Crystals grow from nuclei and intermesh.

And obstruct the growth of adjacent crystals.

This process is repeated by thousands of crystals during growth

And outward stress or thrust develops

That produces an expansion of entire mass

Crystal impingement and movement result in production of micro

pores.

On drying, the excess water is lost

And void space is increased.

Linear Expansion :

- Low – 0.06%

- High - 0.5%.

Control of Setting Expansion :

Sometimes a setting expansion is advantageous for a dental

procedure, sometimes it is disadvantageous, because it may be a source of

error. So setting expansion must be controlled to obtain the desired accuracy

in the dental applications.

- Low w/p ratio and longer mixing time increases the setting

expansion.

- Setting Expansion can be reduced by adding either potassium sulfate,

sodium chloride and Borax.

HYGROSCOPIC EXPANSION

The most well accepted reason for the increased expansion when the

hemihydrate reacts under water is the additional crystal growth permitted by

allowing crystals to grow freely rather than being constrained by the surface

tension when the crystals form in air.

Fig 10-8; pg 270 Phillips

In this theory -

1) In stage I the initial mix is represented by the three round particles of

hemihydrate surrounded by the water.

2) In stage II reaction starts, and crystals of dihydrate begins to form.

In normal setting the water around the particles is reduced and

particles are drawn closely by the surface tension of the water.

In the hygroscopic expansion, as setting takes place under

water the particles remains the same.

3) In stage III, in normal setting water reduced, particles are drawn

closely, but contraction is opposed by the outward thrust of growing

crystals.

In the hygroscopic expansion – crystals are not inhibited, the water is

again replenished from the outside.

4) In stage IV and V-

In normal setting the crystals are habited and become intermeshed

and entangled much sooner than hydroscopic setting.

In hygroscopic setting the crystals are grown freely before

intermeshing and this inter meshing finally prevent the further

expansion.

So the expansion under water is more than that in the normal setting.

The reduction in w/p ratio results the hygroscopic expansion

In creased spatulation results in the hygroscopic expansion.

The hygroscopic expansion during setting of the dental stone is

generally small in the magnitude.

Eg ; Normal expansion of dental stone may be 0.15% and

hygroscopic expansion of dental stone may be 0.30%. This difference

may be sufficient to cause the misfit of the denture or similar device

made on the cost/die.

STRENGDTH OF DIE MATERIALS

The strength of gypsum products is generally expressed in terms of

compressive strength, although tensile strength should also be considered in

order to secure satisfactory guide to the total strength characteristics.

The strength of the plastu/stone increases rapidly as the material

hardens after initial setting time.

The free water content of the set product definitely affects its

strength.

Table 10.5 pg 273 Phillips.

The water traces at last leave fine crystals of gypsum to precipitate.

These fine crystals anchor the large crystals.

Then if water is added or if excess of water is present.

These small crystals are the first to dissolve

Thus the reinforcing anchors are lost.

And also line of the w/p ratio is high, the greater is the porosity, the

fewer crystals are available per unit volume for a given weight of

hemihydrate; and the dry strength is less in the set material.

COMPRESSIVE STRENGTH

Mpa PSI W/p ratio

IV 34.5 5000 0.22-0.24

V 48.3 7000 0.18-0.22

Electro plated Dies/Electro formed Dies :

Besides resin, electro plating can be used to over come the poor

abrasion resistance of gypsom. The metal dies that are produced from

electroplated impression material have high strength, hardness and abrasion

resistance.

Detail reproduction of a line 4 m or less in width is readily

attainable when a non aqueous elastomeric impression material is

used.

Variable degrees of distortion commonly occur, and the technique

must be performed slowly, other wise distortion in the metal will

subsequently stress the impression. CERAMIC DIE MATERIALS

Ceramic materials are supplied as a powder and liquid

They are mixed to a putty like consistency.

This material is placed over the impression

And removal from impression after 1 hour.

Then it is fired at 6000C for 8 minutes to produce a hard strong die.

Common brands :

Ceramite H and V

Cosmotech Vest.

Ducera-Lay

Doric HT2

DVP Investment.

V.H.T. Investment

Vitadurvest.

Properties :

Extremely abrasion-resistant.

Some shrinkage on firing.

Applications :

The prdoduction of dies for porcelain inlays, onlays and veneers.

METAL SPRAYING

Many alloys and metals can be melted and dispersed in the fine

droplets with an oxy acetylene or other flame.

- These fine particles of molten metal or alloy can be sprayed on to

many dry materials with out burning.

- A Bismuth-tiss alloy which melts at 1380C can be sprayed directly

on to an impression to form a metal shell.

- Then this is filled with the dental stone

This method is applicable to the

- Elastomers.

- Impression compound.

If the spraying is done slowly with care softessing of the compound

does not occur.

Advantages :

Accuracy is good.

Disadvantages :

The alloy is rather soft care is needed to prevent abrasion of the die.

Special equipment is needed.

Face mask must be worm to prevent inhalation of the fine spray of the

metal.

AMALGAM

Amalgam may be packed into rigid impression materials such as

impression compound.

The dimensional accuracy achieved depends upon the efficacy of

condensation and the dimensional changes of these materials.

Disadvantages :

The this sections of impression compound occur in the impression

and these may be damaged on condensing the amalgam.

There is a delay of 10-12 hours for the die to be hard enough to be

used.

Location of dowel into the amalgam is not easy. So it is done later.

Mercury hygiene should be practiced.

Contamination of gold alloys by mercury can take place.

Procedure :

An impression is made in a copper band with modeling compound.

A this piece of boxing wax 28 to 30 guage is wrapped around the

impression and extended about 3/8 inch beyond and along gingival

margins of the band and impression.

The boxed impression is embedded in the mix of plaster in a small

rubber ring with the opens end showing the cavity facing up.

After plastic has hardened then plastic mass of amalgam is condensed

into impression.

After setting the rubber ring and plaster is removed and the die is

immersed in warm water to remove the impression compound and

wax.

Impressions of upper and lower arches is takers.

Then amalgam die is placed in the impression of prepared tooth and

cast is poured.

Precaution :

Amalgam dies and all metal dies are good conductors of heat and so

softened wax applied to them cools rapidly.

This rapid cooling of wax may produce internal stresses, which can cause

distortion of wax pattern.

So warming the metal die to mouth temperature or slightly below should be

done.

Polymeric Materials :

1) Auto – polymerizing Acrylic :

The self-cure acrylic is used as die material and it is fabricated in the

same way like the fabrication of the self cure dentures.

Disadvantages :

The monomer reacts with all except silicone impression materials.

The heat of reaction distorts thermoplastic materials.

Volumetric contractions takes place.

All these disadvantages makes the material unsuitable as a die material.

2) Filled Polymeric Materials :

Ex ;

Epoxy Resins.

Polyesters

Epimines

Poly urethane resins.

They are available as liquid and powder and postes; one of which is

either liquid monomer or unsaturated polymer like epime, epoxy, poly ester

or poly urethane resins and the other component may contain powdered

polymer particles and a suitable initiator or activator for polymerizing or

cross linking the fluid phase to produce a solid. Either of them may contain

an inert metallic or ceramic filler.

Common brands :

Diemet

Goldex

Impredur.

Polyroqq.

Manipulation :

The constituents are mixed according to manufacturer’s

recommendations into homogenous paste.

Mixing time is 1 minute.

The paste is then vibrated into the impression.

Some elabtomers require coating with a separating medium; often

finely powdered metal.

Applications :

The production of dies from those impression materials with which

they are compatible, generally elabtomers coated with separating medium.

Advantages :

Rapid set (1hour)

More abrasion resistant.

Not as brittle as die stones.

Better reproductions of the details.

Disadvantages :

Shrinkage (0.02-0.6%) on polymerization may be a source of

inaccuracy-fillers reduce this shrinkage.

Water retards polymerization of resing-so epoxy resins can not be

used with water containing agar and alginate impression materials.

Advances of epoxy materials :

Recently fast setting epoxy materials have been supplied in

automixing systems similar to those for automixing addition

silicones.

The epoxy resin is in on cartridge and the catalyst is in the other.

Forcing the two pasts through the static mixing tip thoroughly mixes

the epoxy material which can be directly injected into a rubber

impressions.

REFRACTORY MATERIALS

There are advantages, of the die, together with its pattern, can be used

directly for casting. This eliminates possible errors in the shape of the

pattern on removing it from the die.

The gypsum bonded material is available for gold castings. The use of

phosphate bonded investment materials has also been suggested for high

fusing alloys.

A commercial gypsum-bonded material is available for gold castings.

The use of phosphate bonded investment materials has also been

suggested for high fussing alloys.

A commercial gypsum-bonded material called divestment is mixed

with a colloidal silica liquid.

The die is made from this mix and the wax pattern is constructed on

it.

Then the entire assembly (die and pattern) is invested in the

divestment to eliminate the possibility of distortion of the pattern

upon removal from the die or during the setting of investment.

Precautions :

special seperator is used with polysurfides.

With out seperator the colloidal silica softens the elastomers and the

die sticks firmly to impression.

It may lead to the destruction of the master die.

Properties :

Compressive strength – 45-50 N/mm2.

Setting time – 15 min

Setting expansion – 1%

Thermal expansion – 0.3%

Hygroscopic expansion – 0.3%.

DIE SYSTEMS :

In the fabrications of the wax pattern, it is used to establish inter

proximal contacts, buccal and lingual contours and occlusion with the

opposing teeth. The die is a model of the Individual prepared tooth on which

the margins of the wax pattern are finished. There are two basic working

cast and die systems-

1. Working cast with a separate die.

2. Working cast with a removable die.

1. Working cast with a separate die :

The working cast and the sectional cast for the die can be obtained

from separate impressions or by pouring an impression twice.

The first cast is used for preparation of the die this

procedure (double pour) can be used only with elastomeric

impressions, since hydrocolloid is form and distorted too much to

be used for an accurate 2nd pour.

Procedure :

1. Impression pouring is done

with the type IV /type die materials.

2. Build up the stone to height of

approximately 1 inch (2.5 cm) over the preparation to allow bulk for

an adequate handle on the die.

Fig 18.3 pg : 310 shillinburs

3. Carefully separate the poured

cast from the impression

4. A material such as Super-Sep

(kerr) may be painted on the surface of the prepared tooth to guard

against surface erosion. (Liquid/Latex).

5. Trim the cast from which the

die is made on a model trimmer to remove all excess stone around the

prepared tooth.

Fig 18.4 pg 311-shillin

6. The handle of the die should

be slightly larger in diameter than the preparation and octagonal in

cross section.

Fig 18.5 pg 311-shillin

7. Sides should be parallel or

slightly tapered towards the base.

Handle should not be angled. (Fig 18.6-311

shill)

8. The handle should be approximately 1 inch long.

Fig 18.7-312-shillin

9. Use a pear shaped bur to trim the die apical to the

finish line of the preparation.

Fig 18.8-312 shillin

10. Finally trim the die with No.25 blade

Fig 18.9-312 shill

11. Smoothers below the finish line with discoid end of

tanner carver.

Fig 18.10-312 Shillin.

12. Die contours should be maintained similar to those of

natural tooth.

Fig 18.12 313 shillin

13. should not have any sharp under cuts or ditching as

instrument used for finishing the margins of the wax pattern will rest

against this portion of the die and this will result in thick gingival area

as the restorations that is not good for gingival health.

Fig 18.13 313.

14. The finish line should be highlighted with a sharp colo

bite red pencil that facilitate carving of the wax pattern.

Fig 18.14 313 shillin

15. Relief should be applied to the preparation area of the

die to provide space for cement.

Usually used relief’s

– Enamels

– Lacquers.

Desired thick ness – 20-40 m.

Should be painted 0.5 mm above the finish line.

Fig 18.15-314 shillin

16. A die hardening agent is applied to finish line area of a

die to prevent abrasion by waxing instruments.

Cyno acrylate – 1-25 m

(or)

Acrylic lacquers – 4-10 m

17. Then the wax pattern prep. Done.

Advantages :

Ease of falorication.

Keeps relationships between abutments fixed and

immovable.

Because the gingival tissue and other land marks

are intact, it is easier to obtain physiologically harmonious

restoration contours when fabricating the wax pattern.

Disadvantages :

Use of working cast with a separate die is that the

wax pattern must be transferred from one to the other an din this

process they destroy some of the internal adaptation of the wax

pattern.

2. WORKING CAST WITH A REMOVABLE DIE :

Requirements :

1) The dies must return to their exact original

positions.

2) The dies must remain stable, even when

inverted.

3) The cast containing the dies must be easy to

mount on an articulator.

Several methods can be employed to allow the repositioning of a die

in its working cast. Most of these devices can either be oriented in the

impression before it is poured i.e., pre-pour technique (or) attached to

the under side of a cast that has already been poured.

Removable Die Systems –

1) Straight dowel pin.

2) Curved dowel pin.

3) Pindex System.

4) Die-lok tray.

1. STRAIGHT DOWEL PIN :

Impression is taken.

Orientation of the dowel pin can be done by the

anesthetic needles, paper clips and bobby pins.

Dowel pin is placed in between the arms of the

bobby pin. Then this bobby pin is positioned bucco-lingually

across the impression, so that the dowel pin will be centered

directly over the preparation.

- Push the straight pins into arms of the bobby pin and into the

impression material on both buccal and lingual surfaces. Stabilize

the dowel pins and straight pins with bobby pins with the sticky

wax.

Fig 18.8 pg-316 shillins

Then pour the die stone into the impressions of the

teeth. The pins should be straight and not touch the impression.

Fig 18.19 pg 316

After impression had set remove bobby and

straight pins place a utility wax at the tip of dowel pin as an aid in

locating dowels after the base has been poured.

- Lubricate the stone around each dowel with a thin coat of

petrolatum or seperating medium to permit easy seperation of the

dies from the working cast later.

Fig 18.20 pg 316 shillin

Place a wet paper towel into the open lingual

space to enable complete base for the cast to be poured.

Fig 18.21 pg316 shillin

Use a sharp knife to uncover the utility wax

Fig 18.22 pg 317

When the stone is hard and dry use a saw frame

with a thin blade to cut mesial and distally through the layer of die

stone. The cut should taper towards gingivally.

Fig 18.23-317

Gently tap the dowel with instrument tip to loosen

the die.

Fig 18.24-317 shi

Take the die from the cast and tries away excess

stone gingivally to the finish live.

Fig 18.25-318 shi

Reseat the dies to make certain that they will seat

completely and will be stable.

Fig 18.26-318

Place wax around the tips of dowels and there

mounted on to the articulator using mounting stone.

Then wax is removed from the ends of the dowel

pins.

2. CURVED DOWEL PIN.

Curved dowels can be incorporated into a working cast by fixing the

dowels to the impression before it is poured or by cementing the dowels into

the holes drilled in a previously poured cast.

i) Installing the pins before pouring :

To install pins before pouring the impression, use

finger pressure to insert a curved dowel tip into the large opening

in the positioning bar.

Bar is oriented taciolingually so that dowel

extends 1-2 mm into impression of prepared tooth.

Place straight pins facio lingually to stabilize bar.

Fig 18.28 pg : 319.

After die has hardened straight and positiong bar

are removed. Depressions are made about 2 mm deep by acrylic

bur on either side of dowels that will assist in orienting the

unprepared tooth.

Fig 18.29 319

This coat of petrolatum is applied to the stone and

dowels.

Fig 18.30 - 320

Boxing wax is placed around the impression, with

the tips of the dowels sticking through.

Fig 18.31 - 320

Then the cast is sectioned.

Fig 18.32 - 320

Segment is removed by pressing on the exposed

tip of curved dowel with knife handle or other instrument.

Fig 18.33 – 320 shillin

ii) Placing the pins after the Impression pouring :

Pour the impression with a die stone to form a

horse-shoe shaped working cast. Trim the bottom of the cast flat

on model trimmer so that not more than 10 mm from the necks of

the teeth.

Fig 18.34 pg :320

Drill 5 mm deep hole with hand piece or drill

press (pindex) in the bottom of the cast directly under the center of

each prepared tooth, pontic area and segment containing

unprepared teeth.

Fig 18.35 pg : 320

If the removable segment is larger than width of

two teeth, the stone on each side of the dowel hole should be

keyed to a depth of 2 mm with large acrylic bur.

Fig 18.36 pg : 321

A drop of cyno acrylate cement is placed into each

of the drilled holes.

Fig 18.37 Pg : 321

The head of a curved dowel is seated into the

cement lined hole and tipes are faced facially.

Fig 18.38 pg : 321

A curved dowel is cemented into each removable

part and thus the boxing is done. Base is poured and dies are

separated as explained previously.

Fig 18.39 pg : 321

3. PINDEX SYSTEM

In the pindex system a reverse drill press is used to create a master

cast with dies that can be removed or replaced repeatedly.

Impression is poured without positioning dowel

pins.

Fig 18.41 pg : 322

After impression is set, wet it and trim with model

trimmer.

Fig 18.42 pg : 322

The cast should be 15 mm thick, exclusive of the

teeth.

Fig 18.43 pg : 323

Periphery and tongue area should be trussed.

Fig 18.44, 18.45 – Pg : 323

Location of pin holes is marked with the pencil.

Fig 18.46 pg : 324

Switch on the pindex macline. A red pilot light

will indicate that it is running.

Fig 18.40 pg : 322

Place the prepared cast on the work table and align

the pencil mark with the light beam director.

Fig 18.47 pg : 324

Raise the handle bar with slow pressure ford 3-5

seconds. And when proper depth has reached the red pilot light

will go off indicating hole is finished.

Fig 18.48 pg : 324

Debris is removed from the pin holes with a brash.

Fig 18.49 pg : 324

Use a hand reamer to remove debris from the pin

holes.

Fig 18.50 pg : 324

Cyno acrylate cement is placed on the pins prior to

cementing the tips. Fig 18.51 pg : 325

Shorter pins are placed first, there longer pins.

Fig 18.52 pg : 325

White slews are placed on long pins and gray

sleeves on the short pins. Fig 18.53

pg : 325

Utility wax is place on the ends of the long pins to

facilitate removal of dies wax is filled over the gray slever to

prevent the filling of the stone into sleves.

Fig 18.56 pg : 325

A palatal/tongue filler is made by boxing wax.

Fig 18.59 pg : 326

Boxing wax is applied around the cast.

Fig 18.60 pg : 326

Thus the base is poured

Fig 18.61 pg : 326

Wax is removed and sectioning of the die and die

preparation and mouting are same as the previous procedures.

4. Di-LOK TRAY

A snap-apart plastic tray with internal orienting

grooves and notches also can be used to reassemble the working

cast and die.

Before using the tray for a given case, examine the

mounting of the diagnostic casts on the articulator to determine

weather there is space for the bulky tray.

Pour the entire full arch impression with die stone

and it should be poured in a U-shape with no stone in the center.

Fig 18.72 pg : 330

The lingual side and base are trimmed. With arbor

band.

Fig 18.73 pg : 330

Horizantal grooves are cut in the base to give it

retention.

Fig 18.74 pg : 330

Stone is poured into the tray and cast is placed into

the tray teeth should be 4 mm above the tray.

Fig 18.75 pg : 331

To complete the dies, the cast must be removed

from the tray.

Fig 18.76 pg : 332

A saw cut is made on each side of the prepared

tooth.

Fig 18.78 pg : 332

The prepared tooth is broken free from the cast by

finger pressure.

Fig 18.79 pg : 332

Trim the die as previously

Fig 18.80 pg : 333

Slide the buccal facing on to the base of the tray

from front place the back down over the lugs on the buccal facing,

locking the tray together.

Fig 18.81 pg : 332

The wax pattern and mounting as explained

previously.

Fig 18.82 pg : 333

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5)