Die materialsDie materials

ContentsContents

IntroductionIntroduction

Ideal requirementsIdeal requirements

Construction of dieConstruction of die

Four system of removable dieFour system of removable die

-- Straight dowel pin-- Straight dowel pin

--Curved dowel pin--Curved dowel pin

--Pindex system--Pindex system

--Di-lok trays--Di-lok trays

Various types of die materialsVarious types of die materials gypsum cast and die materialgypsum cast and die material die stone – investment combinationdie stone – investment combination amalgamamalgam epoxy resin diesepoxy resin dies electroformed dieselectroformed dies silico phosphate cementsilico phosphate cement metal sprayed diesmetal sprayed dies ceramic die materialsceramic die materials flexible die materialsflexible die materials

IntroductionIntroduction

Definition Definition A die is a model of a single tooth (or) teeth A die is a model of a single tooth (or) teeth (or) it is the positive replica of one tooth (or) it is the positive replica of one tooth prepared from an impression.prepared from an impression.

The working cast is the replica of the The working cast is the replica of the prepared teeth ridge areas, and other prepared teeth ridge areas, and other parts of the dental arch.parts of the dental arch.

A cast and die system captures the A cast and die system captures the necessary information so that it can necessary information so that it can be transferred to the laboratory. The be transferred to the laboratory. The ease with which a restoration is ease with which a restoration is fabricated and the accuracy with fabricated and the accuracy with which it will fit the mouth is directly which it will fit the mouth is directly affected by the cast.affected by the cast.

There are three requirements for good cast :There are three requirements for good cast :

They must be bubble free, especially They must be bubble free, especially along finish lines of prepared teeth.along finish lines of prepared teeth.

All portions of the cast must be distortion All portions of the cast must be distortion free.free.

The cast must be trimmed to ensure The cast must be trimmed to ensure access for carving wax pattern margins.access for carving wax pattern margins.

Ideal Requirements of die materials :-Ideal Requirements of die materials :-

It should be dimensionally stable and It should be dimensionally stable and reproduce the surface details of the reproduce the surface details of the impression accurately.impression accurately.

It should possess enough surface It should possess enough surface hardness, smoother surface and abrasion hardness, smoother surface and abrasion resistant during the carving of the wax resistant during the carving of the wax pattern.pattern.

It should possess a color contrast to the It should possess a color contrast to the wax pattern for easy manipulation.wax pattern for easy manipulation.

It should be simple to manipulate, less It should be simple to manipulate, less time consuming.time consuming.

It should be economical and not It should be economical and not hazardous to health.hazardous to health.

It should be compatible with the It should be compatible with the impression materials.impression materials.

Various types of Die materials :-Various types of Die materials :-

1. Gypsum:-1. Gypsum:-

The most commonly used die materials The most commonly used die materials are type IV and type V dental stone, the are type IV and type V dental stone, the properties of which are shown below:-properties of which are shown below:-

(Table 135; P No:- 266, V.K. Sileri)(Table 135; P No:- 266, V.K. Sileri)

Strength of these materials is greatly Strength of these materials is greatly increased by decreasing the porosity, thus increased by decreasing the porosity, thus pouring under vacuum is helpful.pouring under vacuum is helpful.

Decreasing the water / powder ratio Decreasing the water / powder ratio increase the strength. In limits, increase in increase the strength. In limits, increase in the mixing time will increase the strength.the mixing time will increase the strength.Incorporation of accelerators and retarders Incorporation of accelerators and retarders cause a loss of strength.cause a loss of strength.Certain water substitutes can dramatically Certain water substitutes can dramatically increase the strength and hardness of increase the strength and hardness of gypsum eg:- aqueous solution of colloidal gypsum eg:- aqueous solution of colloidal silica.silica.

Setting time can be accelerated by the Setting time can be accelerated by the operator by the use of fine particle operator by the use of fine particle gypsum, low water / powder ratio, long gypsum, low water / powder ratio, long and fast mixing, use of 2% potassium and fast mixing, use of 2% potassium sulphate solution (or) the use of slurry sulphate solution (or) the use of slurry water. water.

Gypsum products are sometimes Gypsum products are sometimes modified to:-modified to:-

Make the material more abrasion Make the material more abrasion resistant. This can be done by using die resistant. This can be done by using die – hardening agents such as – hardening agents such as cyanoacrylate and acrylic resin lacquer.cyanoacrylate and acrylic resin lacquer.

-- These hardening agents must be These hardening agents must be used in very thin coats to avoid any used in very thin coats to avoid any unacceptably thick relief at the margins unacceptably thick relief at the margins of the preparation.of the preparation.

Change the dimensions of the die.Change the dimensions of the die.

This is most commonly done by using a This is most commonly done by using a die spacer. The most common die die spacer. The most common die spacers are resins.spacers are resins.

Models paint, coloured nail polish (or) Models paint, coloured nail polish (or) thermoplastic polymers dissolved in thermoplastic polymers dissolved in volatile solvents may also be used.volatile solvents may also be used.

The thickness varies with the number of The thickness varies with the number of coats applied. Usually a relief of 20 to coats applied. Usually a relief of 20 to 40 um is desired.40 um is desired.

The tooth preparation on the die is painted The tooth preparation on the die is painted to within 0.5mm of the finish line.to within 0.5mm of the finish line.

Die – Stone investment Die – Stone investment combination:combination:

This technique increases the This technique increases the refractoriness of the die.refractoriness of the die.

In this technique, the die material and the In this technique, the die material and the investment have a comparable investment have a comparable composition.composition.

A commercial gypsum bonded material, A commercial gypsum bonded material, called “Divestment”, is mixed with colloidal called “Divestment”, is mixed with colloidal silica liquid.silica liquid.

The die is made from this mix and wax The die is made from this mix and wax pattern constructed on it.pattern constructed on it.Then the entire assembly is invested in the Then the entire assembly is invested in the mixture of divestment and water, thereby mixture of divestment and water, thereby eliminating possibility of distortion of wax eliminating possibility of distortion of wax pattern on removal from die (or) during pattern on removal from die (or) during setting of the investment.setting of the investment.The setting expansion of the material is The setting expansion of the material is 0.9% and thermal expansion is 0.6%, 0.9% and thermal expansion is 0.6%, when it is hasted to 677oC.when it is hasted to 677oC.

Because divestment is gypsum bonded Because divestment is gypsum bonded material, it is not recommended for high material, it is not recommended for high fusing alloys, as used in metal ceramic fusing alloys, as used in metal ceramic restorations.restorations.However it is highly accurate technique for However it is highly accurate technique for use with conventional gold alloys, use with conventional gold alloys, especially for extra coronal restoration.especially for extra coronal restoration.Divestment phosphate is phosphate Divestment phosphate is phosphate bonded investment that is used in the bonded investment that is used in the same manner as Divestment and is same manner as Divestment and is suitable for high fusing alloys.suitable for high fusing alloys.

Amalgam :-Amalgam :-

Conventional amalgam is also used to Conventional amalgam is also used to make dies similar to the silver amalgam make dies similar to the silver amalgam which is used to restore teeth.which is used to restore teeth.

Technique:-Technique:-

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

A thin piece of boxing wax, 28 to 30 gauge, is A thin piece of boxing wax, 28 to 30 gauge, is wrapped around the impression and band matrix wrapped around the impression and band matrix and extended about 3/8 inch beyond and along and extended about 3/8 inch beyond and along the gingival margins of the band and its the gingival margins of the band and its contained impression.contained impression.

The boxed impression is embedded with the The boxed impression is embedded with the open end showing the cavity facing up, in a mix open end showing the cavity facing up, in a mix of plaster, which has been previously placed in a of plaster, which has been previously placed in a small rubber ring to hold it steady and prevent it small rubber ring to hold it steady and prevent it spreading during setting.spreading during setting.

After the plaster base has hardened, a After the plaster base has hardened, a plastic mass of amalgam alloy is mixed. plastic mass of amalgam alloy is mixed. The amalgam is condensed into the The amalgam is condensed into the impression as is done in making a good impression as is done in making a good restoration.restoration.After it has thoroughly set, the rubber ring After it has thoroughly set, the rubber ring and plaster is removed and the die is and plaster is removed and the die is immersed in warm water to remove the immersed in warm water to remove the impression compound and wax.impression compound and wax.The die is then trimmed and tapered so The die is then trimmed and tapered so that it simulates the shape of a tooth root.that it simulates the shape of a tooth root.

An impression of the upper and lower An impression of the upper and lower arches is made. The amalgam die is arches is made. The amalgam die is placed in the impression of the prepared placed in the impression of the prepared tooth and the cast is poured.tooth and the cast is poured.Amalgam dies and all metal dies are good Amalgam dies and all metal dies are good conductors of heat and so softened wax conductors of heat and so softened wax applied to them cools rapidly. applied to them cools rapidly. This rapid cooling of the wax may produce This rapid cooling of the wax may produce internal stresses, which can cause internal stresses, which can cause distortion of the wax pattern.distortion of the wax pattern.

The sudden cooling of the liquid wax when The sudden cooling of the liquid wax when applied to a metal die may also result in applied to a metal die may also result in the contraction of wax away from the die the contraction of wax away from the die and discrepancies may arise because of and discrepancies may arise because of imperfect adaptation of the wax pattern to imperfect adaptation of the wax pattern to the die.the die.

These problems can be avoided by:-These problems can be avoided by:-

Warming the metal die to mouth Warming the metal die to mouth temperature (or) slightly below.temperature (or) slightly below.

In case of amalgam dies, the die should In case of amalgam dies, the die should be lubricated with oil prior to fabrication of be lubricated with oil prior to fabrication of the wax pattern.the wax pattern.

Epoxy resin dies:-Epoxy resin dies:-

Epoxy resins are supplied in two (or) three parts Epoxy resins are supplied in two (or) three parts that are mixed before insertion into the that are mixed before insertion into the impression.impression.

The first part contains 50 – 60% epoxy polymers The first part contains 50 – 60% epoxy polymers 30 – 40% vinyl, cyclo – hexene diepoxide and 30 – 40% vinyl, cyclo – hexene diepoxide and the rest are copolymers.the rest are copolymers.

The second part consists of partially hydrolyzed The second part consists of partially hydrolyzed benzophene tetracarboxylic acid dianhydride.benzophene tetracarboxylic acid dianhydride.

The third part is a tertiary amine catalyst.The third part is a tertiary amine catalyst.

The material is mixed in Vacuum and then The material is mixed in Vacuum and then poured into the impression. It is compatible with poured into the impression. It is compatible with all impression materials except hydrocolloids. all impression materials except hydrocolloids. The resin cures in about half an hour at room The resin cures in about half an hour at room temperature.temperature.

During this curing it shrinks about 0.02 to 0.6% During this curing it shrinks about 0.02 to 0.6% depending on configuration and bulk of the die.depending on configuration and bulk of the die.

This shrinkage can be compensated for by This shrinkage can be compensated for by thermal treatment of the die.thermal treatment of the die.

It is heated in steps of 10o per minute to 160oC It is heated in steps of 10o per minute to 160oC and then held at 160oC for one hour.and then held at 160oC for one hour.

It is then rapidly cooled to room It is then rapidly cooled to room temperature.temperature.The exact mechanism of this expansion of The exact mechanism of this expansion of the material is not known. One hypothesis the material is not known. One hypothesis is that further cross – linking of the is that further cross – linking of the polymer occurs which generates water polymer occurs which generates water causing expansion.causing expansion.Epoxy dies are stronger and more Epoxy dies are stronger and more abrasion resistant than gypsum dies and abrasion resistant than gypsum dies and also the reproduction of surface details is also the reproduction of surface details is much better than with gypsum dies.much better than with gypsum dies.

Silicophosphate Cement :-Silicophosphate Cement :-Compositon:- Compositon:-

It is a glass consisting of silica (sio2), It is a glass consisting of silica (sio2), alumina(Al2o3), fluoride compounds such alumina(Al2o3), fluoride compounds such as NaF, CaF, and Na3AlF3 and some as NaF, CaF, and Na3AlF3 and some calcium salts. This is similar to the filling calcium salts. This is similar to the filling and cementing materials.and cementing materials.These are sometimes used to make dies These are sometimes used to make dies in compound impressions they give harder in compound impressions they give harder dies than dental stone.dies than dental stone.

One disadvantage of these materials is One disadvantage of these materials is that they shrink on setting and the surface that they shrink on setting and the surface of the cement has a tendency to loose of the cement has a tendency to loose water upon standing making it friable.water upon standing making it friable.

- Therefore the cement dies are - Therefore the cement dies are stored in water or glycerine. stored in water or glycerine.

Metal sprayed dies :-Metal sprayed dies :-

A bismuth – tin alloy, which melts at A bismuth – tin alloy, which melts at 138oC can be sprayed directly on to an 138oC can be sprayed directly on to an impression to form a metal shell, which impression to form a metal shell, which can then be filled with dental stone.can then be filled with dental stone.

Advantage :-Advantage :-

A metal coated die can be obtained rapidly A metal coated die can be obtained rapidly from elastomeric impression materials. from elastomeric impression materials.

Dis – Advantage :-Dis – Advantage :-

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

Ceramic die materials :-Ceramic die materials :-Ceramic dies are prepared and used in two Ceramic dies are prepared and used in two methods.methods.In one method, the ceramic should be heated In one method, the ceramic should be heated upto 1000oC.upto 1000oC.In another method, the porcelain powder and In another method, the porcelain powder and liquid are mixed to putty consistency and the liquid are mixed to putty consistency and the material is placed in the impression, is removed material is placed in the impression, is removed after one hour and heated at 600oC for 8 after one hour and heated at 600oC for 8 minutes to produce a hard strong die.minutes to produce a hard strong die.

Flexible Die materials :-Flexible Die materials :-

Flexible die materials are similar to heavy – Flexible die materials are similar to heavy – bodied silicone (or) polyether impression bodied silicone (or) polyether impression materials.materials.

They have been used to make provisional They have been used to make provisional restorations (or) indirect composite resin inlays restorations (or) indirect composite resin inlays (or) onlays chair side.(or) onlays chair side.

The advantages of the flexible material over a The advantages of the flexible material over a stone die include more rapid setting and the stone die include more rapid setting and the ease of removal of the provisional restorations ease of removal of the provisional restorations (or) inlay.(or) inlay.

Construction of the Die :-Construction of the Die :-

The dies can be constructed in two ways:-The dies can be constructed in two ways:-

Where we need two sets of pours (ie) Where we need two sets of pours (ie) working cast with a separate Dieworking cast with a separate Die

Where we need one set of pour (ie) Where we need one set of pour (ie) working cast with removable die.working cast with removable die.

Techniques necessitating two sets of pours:-Techniques necessitating two sets of pours:-

Two pours can be had if elastomeric impression Two pours can be had if elastomeric impression materials are used.materials are used.

Two separate impressions are required if Two separate impressions are required if reversible hydrocolloid is used.reversible hydrocolloid is used.

Dies are prepared from the first pour. These dies Dies are prepared from the first pour. These dies are not incorporated into the working model.are not incorporated into the working model.

Working models are poured from the second Working models are poured from the second impression.impression.

Advantages :-Advantages :-

The mounted casts are not subjected to The mounted casts are not subjected to distortion since mechanical removal and distortion since mechanical removal and insertion of the die may induce stresses insertion of the die may induce stresses and may interfere with its relationship with and may interfere with its relationship with the master cast.the master cast.

There is complete immobilization of the There is complete immobilization of the prepared tooth replica, during building the prepared tooth replica, during building the anatomy, contact and contour of the wax anatomy, contact and contour of the wax pattern.pattern.

Disadvantages :-Disadvantages :-

Moving the wax pattern from the working Moving the wax pattern from the working model to the die and vice – versa can model to the die and vice – versa can induce stresses in the wax.induce stresses in the wax.

The two replicas of the tooth may not have The two replicas of the tooth may not have the same exact dimension and shape, the same exact dimension and shape, thus inducing stresses in the wax pattern.thus inducing stresses in the wax pattern.

Technique :-Technique :-

A pre – measured amount of water is placed in a A pre – measured amount of water is placed in a plastic bowl and a measured amount of die plastic bowl and a measured amount of die stone is added to the water.stone is added to the water.

Die can be poured with approximately 50 – Die can be poured with approximately 50 – 70gms of stone. Full arch impressions require 70gms of stone. Full arch impressions require approximately 200 gms.approximately 200 gms.

The water and powder is vacuum mixed. The water and powder is vacuum mixed. Excessive water is blown from the surface of the Excessive water is blown from the surface of the hydrocolloid impression material without actually hydrocolloid impression material without actually desiccating it.desiccating it.

In case of elastomeric impression material, In case of elastomeric impression material, a surface wetting agents may be sprayed a surface wetting agents may be sprayed on it. on it. A small amount of stone is then carried on A small amount of stone is then carried on the side of the impression above the the side of the impression above the preparation and then vibrated until stone preparation and then vibrated until stone reaches the “bottom” of the preparation.reaches the “bottom” of the preparation.Small increments are continually added till Small increments are continually added till the impression is filled completely.the impression is filled completely.

Stone is built to approximately 1- inch height to Stone is built to approximately 1- inch height to allow adequate bulk for preparation of a handle allow adequate bulk for preparation of a handle on the die.on the die.After this pour is hardened, the impression is After this pour is hardened, the impression is poured again (for elastomers); second poured again (for elastomers); second impression can be used for hydrocolloids to impression can be used for hydrocolloids to obtain full arch working models.obtain full arch working models.The cast from which die is poured is trimmed, all The cast from which die is poured is trimmed, all excess stone around the prepared tooth is excess stone around the prepared tooth is removed.removed.

A handle is cut for the die. The handle A handle is cut for the die. The handle should be slightly larger in diameter than should be slightly larger in diameter than the preparation and octagonal in cross – the preparation and octagonal in cross – section.section.Its sides should be parallel (or) slightly Its sides should be parallel (or) slightly tapered toward the base.tapered toward the base.The handle should be parallel to the long The handle should be parallel to the long axis of the tooth preparation.axis of the tooth preparation.It should be approximately 1 inch long.It should be approximately 1 inch long.

The contour o the die apical to the finish line The contour o the die apical to the finish line should approximate that of the root to facilitate should approximate that of the root to facilitate good axial contours in the finished restoration.good axial contours in the finished restoration.

The wax pattern contacts, contours and occlusal The wax pattern contacts, contours and occlusal morphology is build on the working casts. morphology is build on the working casts.

The dies are reserved for final margination, The dies are reserved for final margination, surface treatment and spruing of the wax surface treatment and spruing of the wax pattern. pattern.

Techniques utilizing one pour :-Techniques utilizing one pour :-

In these technique, the die will be part of In these technique, the die will be part of the working cast, where it can be used to the working cast, where it can be used to build occlusion, contact and contour of the build occlusion, contact and contour of the wax pattern. wax pattern.

The die can be removed from the working The die can be removed from the working cast to marginate, adjust and treat the wax cast to marginate, adjust and treat the wax pattern.pattern.

Advantages :-Advantages :-

It saves time and effort by using only one It saves time and effort by using only one cast.cast.

It eliminates dimensional discrepancies It eliminates dimensional discrepancies between dies.between dies.

There is less distortion of the wax pattern There is less distortion of the wax pattern since it is not moved from one die to since it is not moved from one die to another.another.

Disadvantages :-Disadvantages :-

Mobility in one or more directions is not Mobility in one or more directions is not completely prohibited, especially with the completely prohibited, especially with the loss of interproximal gypsum of adjacent loss of interproximal gypsum of adjacent teeth.teeth.

Necessity for additional tools and Necessity for additional tools and equipment.equipment.