Die materials/ orthodontics workshop

SEMINAR ON;
DIE MATERIALS
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com

CONTENTS
 Introduction
 Ideal requisites of die materials
 Classification of die materials
 Gypsum
 Trimming dies
 Variations in die techniques and materials
 Altering die dimensions
 Die stone-investment combination
 Types of die materials
 Conclusion
 References

DEFINITION
DIE:
A Positive replica of a prepared tooth or teeth in a suitable hard
substance usually in metal or specially prepared stone or resin on which
inlays , crowns and other restorations are made.

INTRODUCTION
Indirect fabrication of patterns for extracoronal restorations
in the mouth is inconvenient, difficult, time consuming, and virtually
impossible, practically all wax patterns are made in the laboratory with the
indirect technique.

Ideal requirements:
 Accuracy of surface reproduction,
 Dimensional accuracy and stability,
 High strength
 Abrasion resistance,
 Compatibility with impression materials,
 Good color contrast,
 Economical,
 Easy to use.

CLASSIFICATION
Inorganic materials
Die stone, based on calcium sulfate hemihydrate
Dental cement – zinc silicophosphate
Ceramic materials
Metallic materials
Dental amalgam
Metal sprayed dies
Electroplated dies
Copper plated
Silver plated
Polymeric materials
Auto-polymerizing acrylic
Other resins which polymerize at room temperature.

 Casts and dies are frequently prepared from dental stone, which has calcium
sulfate hemihydrate CaSO4. ½ H2O as their main constituent, prepared by
heating calcium sulfate dihydrate.
 Dental gypsum products are available in 5 forms (ADA Types I to V)
1) Type I – Impression plaster
2) Type II – Model plaster
3) Type III – Dental stone
4) Type IV – High-strength dental stone
5) Type V – High strength, high expansion stone

PROPERTIES :
 W/P ratio: 0.22-0.24 ml,
 Setting time: 12(+/-)4 min,
 Setting expansion: 0.1%
 Compressive strength: 5000(psi),
 W/p ratio:0.18-0.22 ml,
 Setting time:12(+/-)4 min,
 Setting expansion:0.3%,
 Compressive strength:7000psi .
Type IV stone Type V stone

IMPRESSION SURFACE
 Clean
 Dry
 Immersed in 3% potassium sulphate solution

PROPORTIONING
 Measuring by weight
 Thin mix
 Thick mix

TRIMMING DIES

VARIATION IN DIE TECHNIQUE
 Sevaral means are used to increase resistance to abrasion:
 Gypsum hardners-aqueous colloidal silica.
 Treating surface with epoxy resin or cyanoacrylate - dilution with acetone.
 Incorporation of wetting agents such as lignosulphonates.

METHODS OF ALTERING DIE DIMENSIONS
 To reduce setting expansion and therefore to reduce diameter of die
(0.1 % to 0.01 %) :
 pottasium sulfate ( accelerator )
 borax ( retarder )
o To increase setting expansion:
 Colloidal silica added to guaging liquid

DIE SPACER
 To produce relief space for cement it is common to use a die spacer with a
stone die.
 Most commonly used die spacer are resins.
 Other die spacers used are:
 Model paint
 Color nail polish
 Spacers are applied in sevaral coats to with in 0.5 mm of preparation finish
line

 Advantages of gypsum die materials:
 Good strength
 Easy manipulation
 Excellent working time
 Sets quickly
 Compatible with impression materials
 Have smooth hard surface
 Can be easily trimmed
 Have good color contrast
 Is economical.

 Disadvantages:
 Brittle
 Susceptibility to abrasion during carving of wax pattern.

DIE STONE-INVESTMENT COMBINATION
( DIVESTMENT ):
 This the combination of die material and investing medium.
 The gypsum bonded material called divestment is mixed with colloidal
silica liquid.
 The setting expansion is 0.9% and thermal expansion is 0.6% when heated
to 677c.
 it is accurate technique for gold alloys.

Phosphate-bonded investment ( divestment phosphate )
 Used in same manner as divestment.
 Used for metal ceramic restorations ( high fusing alloys )

ELECTROFORMED DIES
 Electroforming refers to electrodeposition of the metal on a metallic or non
metallic object by passage of electrical current through the electrolyte
 The art of electroforming is called galvanoplasty.
 1934 Jacob first used it.
 1937 Wajna applied in dentistry.

 Metalizing:
 The impression surface is made conductive so that it can conduct electric
current.
 Metalizing agents are:
 Bronzing powder
 Aqueous suspension of silver powder.
 Powdered graphite.
 They are placed with camel hair brush.

METALS USED FOR ELECTROFORMING
 Copper sulfate crystals 200 gms,
 Conc sulfuric acid 30 ml,
 Phenol 2ml,
 Distilled water 1000ml.
 Silver cyanide 36gms,
 Potassium cyanide 60gms,
 Potassium carbonate 45gms,
 Distilled water 1000ml.
Copper bath: Silver bath:

Anode (+)
Copper or
silver plate
Cathode ( _ )
Impression
ammeter
Electrolyte solution
External circuit

PROBLEMS IN METAL FORMING
 Faulty conduction
 Exhausted solution
 Overconcentrated solution
 Metal anode too small
 Friable metal deposit

ADVANTAGES:
1.Superior surface reproduction,dimensional accuracy.
2.Hard,abrasion resistant.
3.Imparts a smooth surface to wax pattern.
3.Not very expensive.
4.Better marginal definition.
5.Does not absorb oil or water.
6. Allows satisfactory finishing and polishing.

DISADVANTAGES:
 1.Difficult to trim.
 2.Silver bath health hazard ( death chamber gas )
 3.Not compatible with all impression materials.
 4.Colour contrast not as good as die stone.
 5.Adaptaion of wax pattern is not good,it tends to lift.

EPOXY RESIN DIES:
 They are either self curing acrylic materials, e.g epoxy resins, poly esters,
and polymeric materials with metallic or ceramic fillers.

COMPOSITION:
They are two component systems that include resin and hardener.
mix ratio: 10 parts resin to 1 part activator by weight.
 The hardener is a polyamine , when mixed with a resin for about a minute
causes polymerization
 Dimensional changes occuar between 0.1 % to 0.2 % and may continue to
occur up to 3 days
 Auto mixing device
 Compatibility with impresssion materials .

 Advantages:
 Excellent surface detail
 Adequate surface hardness and abrasion resistance.
 Less brittle than die stone.
 Can be cured at room temperature.
 Disadvantages:
 Dimensional inaccuracy.
 Expensive.

AMALGAM DIES:
 They are made by packing amalgam in to impression made of impression
compound.
 Dies exhibit superior strength and reproduce fine details.
 Limitations:
 It can be packed only in to a rigid impression material.
 It is technique sensitive
 It requires 24hrs for hardening.
 It has high thermal conductivity and can cool wax pattern rapidly
 Residual mercury presents a health hazard.
 Dimensional changes due to delayed expansion.

SILICATE CEMENT DIES:
 It is similar to the filling cement material.
 Advantages:
 Initial strength and surface hardness is superior to that of die stone.
 Used with all impression materials
 Disadvantages:
 the cement contracts during setting and may be dimensionally in accurate.
 There is loss of water on standing, causing a rough and dehydrated surface.

METAL SPRAYED DIES
 A bismuth-tin alloy, which melts at 138c is sprayed directly on to an
impression to form a shell. Which can be filled by die stone.
 Disadvantage is that the alloy is soft and does not fulfill mechanical
requirements of the die material.

CERAMIC DIE MATERIALS
 Ceramic material supplied as a power and liquid and mixed to a putty like
consistency.
 After 1hr material is recovered from the impression and fired at 600c for 8
min to produce a hard strong die.
 Advantages:
 Accuracy is good.
 Can be obtain rapidly from elastomeric impression materials.
 disadvantages:
 Less abrasion resistant.
 Special equipment necessary.

Compatibility of impression materials
Cast or die material Impression material
Gypsum product Compound
Zinc oxide eugenol
Agar or Alginate,
Plaster, if coated with separator
Elastomeric impression materials
Electroplated copper Compound
Silicone (all types) rubber base.
Electroplated silver Elastomeric impression materials
Epoxy resin Elastomeric impression materials

REVIEW OF LITERATURE:
1. James c. ragain etal: Detail reproduction, contact angle and die hardness of
elastomeric impression and gypsum die material combination.
Int J PROSTHODONT 2000; Vol 13; No. 3; pp 214-20.
i. Adequate detail reproduction of prepared teeth may be achieved with the
combination of any of the elastomeric impression materials with any of the
die stone materials tested.
ii. When using polyvinyl siloxane or polyether impression material, type IV-
resin reinforced die stone may produce dies that are less scratch resistant on
the surface than the type IV die stone used in this study.
iii. No overall combination of die and impression materials was identified as
superior to another for all of the surface properties studied.

2. Reza h. heshmati etal: Delayed linear expansion of improved dental
stone J Prosthet Dent 2002 Jul Vol 88 No. 1 pp: 26-31.
The objective of this invitro study were to measure the linear
setting expansion of 6 ADA types IV and V dental stones
To compare their expansion at 2 hours to 120 Hrs. All stones showed higher
mean linear expansion values at 120 hrs than at 2 hrs.
The amount of expansion varied significantly among the materials with
22% - 71% of the expansion occurring after 2hrs.

3. Philip duke etal : Study of the physical properties of type IV gypsum,
resin-containing and epoxy die materials
J Prosthet Dent 2000 Apr; 83 (4): 466-73.
i. All gypsum products expanded, whereas the epoxy resin material contracted
during setting.
ii. The epoxy resin exhibited much better detail reproduction, abrasion
resistance and transverse strength than the gypsum materials.
iii. A conventional type IV gypsum exhibited the highest surface hardness
whereas the epoxy resin had the lowest value.
iv. The resin-modified gypsum products were not significantly superior to the
conventional type IV gypsum die materials.

4. Tadanori , shane n. white: Dimensional accuracy of an epoxy resin die
material using 2 setting methods
J Prosthet Dent 2000 Mar; 83 (3): 301-5.
Retarding the setting reaction of an epoxy resin die
material improved its accuracy of the materials tested. The retarded set
epoxy dies had the least mean dimensional change from the metal master.
Epoxy resin die materials had a net shrinkage, but the gypsum-based
materials had a net expansion. The epoxy resin materials exhibited more
variability than the gypsum-based materials

5.Johnson etal : Dimensional accuracy of 7 die materials.
J Prosthodont 2005;14;25-31.
i. Type 1V resin impregnated dental stone and copper plate dies most closely
approximates the master die.
ii. Conventional type 1V and V - setting expansion
iii. Epoxy resin - shrinkage
iv. Polyurethane-combination of expansion and shrinkage
v. Bis-acryl composite dies – excessive shrinkage

6. E ricardo etal : Fracture strength of type iv and type v die stone as
function of time
J Prosthet Dent 1997 ;vol 78; no 6; pp 554-559
The study evaluated the fracture resistance of four die stone
materials at different time intervals ½, 1, 12, 24 hours and recommended to
wait atleast 12-24 hours when separating casts from impressions to avoid
fracturing casts. Residual moisture content in a stone cast may contribute to
fracture.

7. Paul E. harris and etal : Alterations of surface hardness with gypsum
die hardners
J Prosthet Dent 2004; vol 92; pp 35-38
The purpose of this study was to compare the surface
microhardness of 4 contemporary gypsum materials with and without
surface die hardner. Die stones evaluated in this study did not differ
significantly in surface microhardness. Die hardner coatings reduced the
surface hardness of the gypsum material.

8. Gerard derrien etal : Compatibility of type IV dental stone with
Polysulfide impression materials
J Prosthodont 1992 Sep, Vol, No.1 pp:32-6.
This study evaluated the compatibility of 6 polysulfide
impression materials and 11modified type IV dental stone. The
compatibility was determined by the presence of a reproduce line on the
dental stone.
The study showed that many combinations of polysulfide
impression materials and modified type IV dental stones did not reproduce
the 20 microns line, therefore not every polysulfide is compatible with
every type IV dental stone.

9. Smith D.C etal : Comtpatibility of impressions and die stone material
Oper Dent 1990 May-Jun Vol 15 No. 3 Pp: 82-5.
The purpose of this pilot study is to test the compatibility of four light-
bodied polysiloxane impression materials with 11 different die stones.
The ADA Spec No. 19 states that in order for an elastomeric
impression material to be considered compatible with gypsum materials, it must
reproduce a 20 µm wide line in stone.
All 11 die stones and polysiloxane impression combinations
performed within the 20µm ADA standard.

10. Jack D. gerrow : Compatibility of a new epoxy resin with impression
materials :
Am J Dent 1990 Aug Vol 3 No.4 pp: 171-4.
This study evaluated the compatibility of 5 Polyvinyl siloxanes,
one Polysulfide and one Polyether impression materials with the new epoxy
resin (Alpha die 87). Only the polysulfide and polyether were prepared
with the super sepator. Detail reproduction of the line or compatibility was
determined by the presence of the reproduced line on the epoxy specimen.
The line was reproduced in only 71.4% of the epoxy specimens.
The epoxy specimens reproduced the line in all the
polyvinyl siloxane specimens.

CONCLUSION :
The ease with which a restoration is fabricated and the
accuracy with which it will fit the mouth is materially affected by the casts
and dies. So a die material should be selected that has good dimensional
accuracy, abrasion resistance and ability to reproduce fine detail and sharp
margins.

REFERENCES :
1. Anusavice - Phillips Sciences of Dental materials, 10th
Edition.
2. Contemporary fixed prosthodontics – Stephen F. Rosenstiel – 3rd
Edition.
3. Dental materials- Properties and manipulation – Craig, Obrein,
Powers, 5th
Edition.
4. E.C. Combe-Notes on Dental Materials, 6th
Edition.
5. John N.Andreson – Applied dental materials, 5th
Edition.
6. John F. McCabe- applied dental materials, 7th
edition
7. Restorative dental materials – Robert, G. Craig and John H.
Powers, 11th
Edition.
8. The clinical hadling of Dental materials – Bernard G.N, Smith,
Paul S.Wright and David Brown 2nd
Edition.

1. James c. ragain etal: Detail reproduction, contact angle and die
hardness of elastomeric impression and gypsum die material
combination. Int J PROSTHODONT 2000; Vol 13; No. 3; pp 214-20
2. Reza h. heshmati etal: Delayed linear expansion of improved dental
stone J Prosthet Dent 2002 Jul Vol 88 No. 1 pp: 26-31.
3. Philip duke etal : Study of the physical properties of type IV gypsum,
resin-containing and epoxy die materials. J Prosthet Dent 2000 Apr; 83
(4): 466-73.
4. Tadanori , shane n. white: Dimensional accuracy of an epoxy resin die
material using 2 setting methods .J Prosthet Dent 2000 Mar; 83 (3): 301-
5.

5.Johnson etal : Dimensional accuracy of 7 die materials.
J Prosthodont 2005;14;25-31.
6. E ricardo, xavier lepe : Fracture srrength of type iv and type v die
stone as function of time. J Prosthet Dent 1997 ;vol 78; no 6; pp 554-559
7. Paul E. harris, scott hayer, clark m. stanford : Alterations of surface
hardness with gypsum die hardner. J Prosthet Dent 2004; vol 92; pp 35-
38

8. Gerard derrien, georges sturtz : Compatibility of type IV dental stone
with Polysulfide impression materials:
J Prosthodont 1992 Sep, Vol, No.1 pp:32-6.
9. Smith D.C, price C.ACompatibility of impressions and die stone
materials: Oper Dent 1990 May-Jun Vol 15 No. 3 Pp: 82-5.
10. Jack D. gerrow : Compatibility of a new epoxy resin with impression
materials : Am J Dent 1990 Aug Vol 3 No.4 pp: 171-4.

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Die materials/ orthodontics workshop

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