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1. DIE MATERIALS
INDIAN DENTAL ACADEMY
Leader in continuing Dental Education

2. CONTENTS
• Introduction
• Ideal requirements of die materials
• Types of die materials
- Material Science
- Advantages
- Disadvantages
- Indications and contraindication
● Summary and conclusion
● References

3. DEFINITION
A die is working replica of a
single tooth, sveral teeth or tissue
surface.

4. MATERIALS USED FOR FABRICATION
OF DIES
• Gypsum products
• Electroformed dies
• Epoxy resins i.c silica filled and aluminium filled
• Amalgam dies
• Metal sprayed dies
• Ceramic dies
• Divestments
• Polyester and acrylic

5. IDEAL REQUIREMENTS
1. It should be accurate
2. It should be dimensionally stable under normal
conditions of use and storage
3. Setting expansion and contraction, variations in
response to change in temperature need to be
minimum
4. It should reproduce the fine details such as prepared
and unprepared tooth satisfactorily

6. 5. It should be strong and durable and be able to withstand
the subsequent manipulative procedures without
abrasion or fracture
6. They should withstand the carving and finishing
procedures
7. The color should contrast that of the wax to ease the
manipulation
8. Economical
9. Easy to use

7. GYPSUM
• Gypsum is a mineral mined in various parts of the world
• The mineral which is used for dental purposes is nearly
pure calcium sulphate dihydrate (CaSo4 . 2H2O)
• The most commonly used die materials are Gypsum
type IV (dental stone, high strength), Gypsum type V
(dental stone, high strength, high expansion )

8. Manufacture
• Gypsum is the dihydrate form of calcium sulphate
CaSo4.2H2O
• It is ground and subjected to temperature of 110 to
120o
C to drive off the water of crystallisation
• CaSo4.2H2O (CaSO4)2 + H2O

9. • The improved stone is made by removal of the water of
crystallization which is achieved by addition of another
chemical such as boiling in 30% calcium chloride
solution, after which the chloride ions are washed away
and the calcium sulphate hemihydrate is dried and
ground to the desired fineness
• The improved stone consists of α hemihydrate
• These crystals are prismatic and more regular in shape
than those of plaster

10. DENTAL STONE, HIGH STRENGHT
(TYPE IV)
• ADVANTAGES
• It has good strength , hardness (aprroximately 92 RHN)
• The surface hardness increases more rapidly than the
compressive strength (as the surface dries quickly)
which is an advantage as the surface resists abrasion
while the core of the die is tough and is less subject to
accidental breakage

11. • DISADVANTAGES
• Poor resistance to abrasion. In order to overcome this
gypsum hardeners have been used (colloidal silica) this
does not improve the strength but improves the abrasion
resistance by as much as 100%
• Certain low viscosity resins such as cyanoacrlates can
also be used to improve the strength

12. • Resin strengthened gypsum products such as Resin
Rock have high strength and low expansion
• Other material which can be added are gum arabic,
calcium hydroxide mixture etc
• But it is easier to use a die spacer with dental stone .
• The die spacers which can be used are resins, model
paint, certain paint on liquids, coloured nail polish or
thermoplastic ploymers dissolved in volatile solvents

13. DENTAL STONE, HIGH STRENGTH, HIGH
EXPANSION (TYPE V)
• ADVANTAGES
• Higher compressive strength than the Type IV
• Setting expansion has increased from 0.1to 0.3% (the
higher expansion compensates for the alloy solidification
shrinkage )

15. • Impression materials which can be used with gypsum
are impression compound, Zinc oxide eugenol, Agar,
alginate hydrocolloid, silicones and polyether rubber
based material
• Increase in hardness of stone dies poured against
impressions varies from
- 2% for silicones
- 110% for polyether
- 70% for agar
- 20% for polysulphide
• 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

16. • If less setting expansion is desired , potassium sulphate
(accelerator )or borax (retarder) are added to the
gauging water , which limits the setting expansion to
0.01%
• If a die slightly larger than the prepared tooth is required
then colloidal silica can be added to the gauging water or
the surface can be coated with resins

17. • Stone dies may be from 0.02% to 0.05% larger than the
master to 0.04% to 0.25% smaller than the master
depending on the location of the measurement and the
impression material used
• In general occluso- gingival changes are greater than
bucco-lingual or mesio-distal

18. DIVESTMENT
• A commercial gypsum bonded material called
divestment is mixed with colloidal silical liquid.
• The die is made from this mix , wax pattern is
constructed on it, and then the entire assembly (die+
pattern) is invested in a mixture of divestment and water,
thereby eliminating the possibility of distortion of pattern
on removal from the die or during setting of the
investment
• Setting expansion is 0.9%
• Thermal expansion is 0.6% when heated to 677o
C
• It is highly accurate for conventional gold alloys
• It is not recommended for high fusing alloys like metal
ceramic restorations .

19. ELECTROPLATED DIES
• Electroplated dies are the ones that are produced when
an impression material is electroplated
• When a die is made in this manner this process is known
as electroforming
• The impression materials which can be electroplated are
impression compound and elastomeric materials
• The types of dies are-
- Copper plated dies
- Silver plated dies
• The popularity of copper plated dies began in the early
1930’s

20. • ADVANTAGES
• No dimensional changes occur during electro deposition
of a metal
• It reproduces the impression accurately
• The die is tough and has good strength characteristics

21. Apparatus
• A transformer and rectifier to reduce the voltage of the
domestic supply and to convert the AC current to DC
current
• The low voltage direct current passes through a variable
resistor, which is used to regulate the current and modify
the rate at which the metal is deposited
• A milliammeter that indicates the current passing through
the bath

22. COPPER PLATED DIES
• Impression compound is usually copper plated
• The impression material is the cathode and it is
connected to the anode which is made of electrolytically
pure copper and is immersed in the plating solution so
that the area of copper immersed is approximately equal
to that of the impression to be plated
• COMPOSITION OF SOLUTION FOR
COPPERPLATING BATHS
Copper Sulphate (crystals) - 200gms
H2SO4 (conc) - 30ml
Phenol Sulfonic Acid - 2ml
Water Distilled - 1000ml

23. • TECHNIQUE
• The surface of the impression is coated with a conductor
of electricity such as graphite, copper powder, silver
before it is attached to the cathode lead wire. This
process is known as “metalizing”. This determines the
surface character of the finished die
• The copper sulphate is the source of copper, the
sulphuric acid increases the conductivity and phenol
sulfonic acid helps to assist the penetration of the copper
crystals into the deeper parts of the impression
• Initially 15 ma current is given which can later be
increased to 2 to 3 times the initial current
• The plating is allowed to proceed for 12 to 15 hours
(usually overnight)

24. • Points to be noted
• If too high a current is used the copper deposit will be
friable and granular in nature
• High current densities also produce a heavier deposit on
those areas of the impression that are nearest to the
anode
• Rapid plating can result in a failure to cover adequately
the deeper areas of the impression

25. • The quality of deposit obtained with a freshly made
solution is not as good as that obtained with a solution
that has been in use for some time
• Loss of water from evaporation should be replaced from
time to time to maintain correct concentration of the
solution
• The sulphuric acid decomposes when the solution is in
use and a few ml of the acid should be added after few
weeks use

26. • In copper plating the distance between the anode and
the impression to be coated affects the quality of the
plating; the greater is the anode to impression distance ,
the more even is the quantity of copper deposited over
the impression
• 6 inches is considered to be suitable distance , if the
distance is reduced then more copper is deposited on
the more superficial areas of the impression leaving the
deeper areas inadequately plated

27. SILVERPLATED DIES
• Silver plating is done over rubber based impression
materials
• Though it is possible to copper plate rubber based dies
the results are not always consistent
• Silver plated dies show more vertical change than stone
dies, the difference being between 0.25% to 0.45%
depending on the impression material , while the
horizontal changes are not significant
• A pure silver anode and a silver cyanide plating solution
is required
• COMPOSITION OF THE SOLUTION
Silver cyanide - 36gm
Potassium cyanide - 60gm
Potassium carbonate - 45gm
Water (distilled) -1000ml

28. • Technique
• The impression is first made conductive by brushing the
surface with powdered silver
• A current of 5ma is suitable to start plating a single tooth
impression and 10 ma for larger areas
• Once a layer of silver is deposited the current can be
doubled or trebled
• Time period is usually 12 to 15 hours

29. • Points to be noted
• The solution used is poisonous and extreme care should
be taken that the hands, working area and clothes do not
get contaminated
• Accidental contact of the solution with acid will produce
hydrogen cyanide which is an extremely poisonous gas
• The plating bath should have a cover to control
evaporation and dissipation of fumes

31. • Problems in silverplating
1. Faulty conduction – the ammeter may show current
flowing but the impression does not plate or plates
irregularly or slowly. This difficulty is due to a short
circuit through the electrolyte usually due to the
exposure of the conducting wire to the solution
2. Exhausted solution- plating is very slow and the
deposit is discoloured. The solution should be
discarded and replaced with a fresh one

32. 3. Over concentrated solution- sometimes the ammeter
reading drops rapidly to zero after the impression is
placed in the bath. Resetting of the current regulator is
followed by another drop to zero, this is due to too
concentrated solution. Adding distilled water and rinsing
the silver anode in distilled water will solve the problem
An over concentrated solution will also cause softening of
the rubber and discoloration of the stone areas of the
cast
4. Silver anode too small- an anode that is smaller than the
impression will lead to slow and irregular plating

33. RESINS
• Two types of die materials are available
1. Epoxy resin
2. Polyurethane
• Of the two epoxy resin is more commonly used these
are self curing acrylic materials with fillers either
metallic or ceramics

34. EPOXY RESINS
• They are used effectively with rubber based impression
materials
• They cannot be used with water based agar and alginate
impression materials because the water retards the
polymerisation of the resin
• It is available in the form of a paste to which an activator
is added to initiate hardening
• Care should be taken that the activator not come in
contact with the skin as it is toxic

35. PROPERTIES
• Working time -15min
• Setting time 1 to 12 hours depending on the products
• Knoop hardness no is 25 KHN+/-15 less than that of high
strength stone 77 KHN
• Compressive strength after 7days is 16,000psi
• Abrasion resistance is superior to stone dies
• Dimensional change due to shrinkage during
polymerization is between 0.03% to 0.3% and continues
to occur for up to 3 days
• Epoxy resin are very viscous when pored hence porosity
can occur

36. • Advantages
1. It is more resistant to abrasion and is less stronger
than dental stone
2. It is reasonably dimensionally stable
• Disadvantage
1. The epoxy resin cannot be readily introduced into the
details of a large impression as dental stone and
requires a centrifugal machine for the same
2. It shrinks by about 0.1to 0.2% in about 24 hours
3. It is expensive

38. AMALGAM DIES
• Model amalgam is similar to silver amalgam which is
used for fillings
• It is used to make hard metal dies which reproduce fine
details and sharp margins from impression compound of
prepared teeth
• They cannot be made in hydrocolloid impressions as
they cannot withstand condensation pressure
• After packing the impression with amalgam the die can
be removed after a minimum of 12 hours, by gently
warming the compound

39. • As amalgam is a good conductor of heat , softened wax
applied to them cools rapidly
• This may produce internal stresses which may distort the
wax pattern after removal from the die
• Sudden cooling of the wax may also result in contraction
of the wax away from the die
• A separating agent is needed as with die stone

40. FLEXIBLE DIE MATERIALS
• They are similar to heavy bodied silicone or polyether
impression materials
• Selection of a compatible die and impression material is
very important in case of flexible dies
• Advantages over die stone
• Rapid setting
• Ease to removal

41. METAL SPRAYED DIES
• A bismuth – tin alloy which melts at 138o
Ccan be sprayed
directly on to an impression to form a metal shell which
can than be filled with dental stone
• A metal coated die can be obtained rapidly from
elastomeric impression material
• Disadvantage the alloy is soft care is needed to prevent
abrasion of the die

42. CERAMIC DIE MATERIALS
• A material for the production of die on which porcelain
restorations are to be fabricated with out the use of a
platinum foil matrix to form the dies heating to over
1000o
C is necessary this can be used for all ceramic
crowns and veneers
• A ceramic materials supplied as a powder and liquid and
mixed to a putty like consistency after 1 hour the material
is removed form the impression and fired at 600c
C for 8
min to produce a hard stone die

43. REVIEW OF LITERATURE
• Gerald T Nomura et al 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

44. • 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

45. • James Stackhouse (1970) conducted a study
concerning the accuracy of stone dies affected by the
dimensional changes in rubber impressions
• Material used were three silicone rubber impression
materials
• Impression techniques used were
1. Heavy body with wash syringe material
2. Perforated tray and the heavy body impression
material was also perforated
3. Simultaneous double mix technique
• 10 stone dies were made of each material/ technique/
time period groups
• More than 500 dies were made

46. • The author concluded that
1. More uniform dies were produced from silicon
2. One silicone material was more significant than the
others
3. Perforated tray technique caused the dies to be
undersized in diameter
4. The first and third technique were not significantly
different from the other
5. Bench setting caused the stone dies to be shorter in
length and thicker in diameter

47. • B. J. Crispan et al conducted a study of the marginal
accuracy of cast restorations
• The impression materials used were Permlastic,
Impregum, Xantoprene and Reprosil
• 3 silver plated dies and 3 stone dies were fabricated
from each of the 4 impression materials
• The author concluded that
1. The marginal accuracy of crowns fabricated on silver
plated dies is as accurate as crowns fabricated on
stone dies
2. Silver plated dies fabricated from Reprosil produced
more accurate crowns than other dies tested
3. Silver plated dies can be used without compromising
crown margin accuracy.

48. • In a study conducted in our department under Prof
N.P.PATIL - the critical evaluation of dimensional
behaviour of 3 different die materials was evaluated
• The die materials studied were Type IV Gypsum, Type
IV synthetic Gypsum and epoxy resin
• The impression material used was poly vinyl silicon
• A total of 90 dies were fabricated from 3 different die
materials and 3 different combination impression
techniques were used

49. • The conclusion drawn was
1. All the dies obtained differed in interabutment distance
at the occlusal level
2. All the dies showed decrease in bucco lingual width
3. All the dies showed decrease in height of molar and
premolar abutments
4. Epoxy dies were undersized and are acceptable
alternatives to gypsum when PVS is the impression
material
5. Putty and light body impression using stock trays are
more reliable when compared with impressions made
using custom acrylic trays

50. Comparison
• 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

51. SUMMARY AND CONCLUSION

53. CONCLUSION
• All factors considered the high strength stones (Type IV
and V) appear to be the most successful die materials
available, with care , abrasion during carving of the wax
pattern can be avoided . In case of metal ceramic
restoration gypsum dies can be damaged and a resin or
metal die can be prepared.

54. REFRENCES
• Craig Restorative dental materials sixth edition Mosby
• Philips (1992) Science of dental materials 9th
edition W.B Saunders
• Rosensteil (2001) Contemporary Fixed Prosthodontics 3rd
edition
Mosby
• Shillenberg (1981) Fundamentals of fixed prosthodontics 2nd
edition
Quintessence
• Silver plated dies marginal accuracy of cast restorations J Prosth
Dent 51;1984: 768-772
• Comparision of surface detail reproduction of flexible die materials J
Prosth Dent 1998; 80:485-9
• An investigation of epoxy resin dies J Prosth Dent 1980;44:45-9
• The accuracy of stone dies made from rubber impression materials
J Prosth Dent 1970;24:377-85

55. THANK YOU