2. CONTENTS
Introduction
Review of literature
Definition
Requirements of cast
Requirements of die preparation
Ideal requirements of die material
Materials
Methods
Bibliography
3. INTRODUCTION
Direct fabrication of patterns for
extracoronal restorations in the mouth is
inconvenient, difficult, time consuming,
and virtually impossible. A cast and die
system captures the necessary
information so that it can be transferred
to the laboratory.
Rosensteil (2001) Contemporary Fixed Prosthodontics 3rd edition Mosby
4. REVIEW OF LITERATURE
James Stackhouse (1970) conducted a study concerning the
accuracy of stone dies affected by the dimensional changes
in rubber impressions
They 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. Bench setting caused the stone dies to be shorter in length
and thicker in diameter
5. Gerald T Nomura et al(1980) evaluated the accuracy, fit,
detail registration and Knoop hardness of 3 commercially
available resin die systems
They concluded :
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
6. Myers M., Hembree J.H.(1982) – conducted a
study on the relative accuracy of four removable
die systems. 4 die systems were studied i.e.
the brass dowel pin, the Plastipin, the J-pin, &
Logix Model System & they determined the vertical
shift & the horizontal shift of the dies.
They concluded that Plastipin exhibited least
amount of horizontal shift & the brass dowel pin
exhibited greatest shift in both directions.
7. DEFINITION
MODEL : “A MODEL IS A REPLICA OF A
TEETH AND THE ASSOCIATED
SUPPORTING BONY TISSUE OF A
JAW,WHICH IS PREPARED FROM AN
IMPRESSION.”
DIE : “A POSITIVE REPRODUCTION OF
PREPARED TEETH AND CONSISTS OF A
SUITABLE HARD SUBSTANCE OF A
SUFFICIENT ACCURACY.”
8. REQUIREMENTS OF THE
CAST
Accurate surface detail
Free of voids.
Precise articulation.
Soft tissue should be reproduced
Rosensteil (2001) Contemporary Fixed Prosthodontics 3rd edition Mosby
9. REQUIREMENTS FOR THE
DIE PREPARATION
Reproduce the prepared tooth exactly.
No bubbles or void
The remaining unprepared tooth structure
immediately cervical to the finish line
should be 0.5 to 1mm visible.
Adequate access to the margin is
imperative.
Rosensteil (2001) Contemporary Fixed Prosthodontics 3rd edition Mosby
10. IDEAL REQUIREMENTS FOR
DIE MATERIAL
Accurate
Dimensionally stable
Setting expansion and contraction, variations in
response to change in temperature need to be
minimum
It should reproduce the fine details
Rosensteil (2001) Contemporary Fixed Prosthodontics 3rd edition Mosby
11. Strong and durable
Withstand the carving and finishing procedures
The color should contrast that of the wax to ease the
manipulation
Economical
Easy to use
Rosensteil (2001) Contemporary Fixed Prosthodontics 3rd edition Mosby
12. MATERIALS
It includes :
Gypsum
Type1-Impression Plaster
Type2-Model Plaster
Type3-Dental Stone
Type4-Dental Stone(High strength)
Type5 –Dental Stone(High strength and high expansion)
Resin
Epoxy Resin
Polyurathane
Electroplated Dies
Copper plated
Silver plated
Flexible Die Materials
Amalgam used die material
Metal sprayed die
Rosensteil (2001) Contemporary Fixed Prosthodontics 3rd edition Mosby
13. GYPSUM
Gypsum(CaSO4.2H2O) is a mineral mined
product used extensively in dentistry to
make dental models.
In its unrefined state, gypsum is the dihydrate
form of calcium sulfate.
Model plaster
Commonly called plaster of Paris, is used
primarily for pouring preliminary impressions
and the making of diagnostic models.
Dental stone
For use as a working model when a more
durable diagnostic cast is required.
Philips (1992) Science of dental materials 11th edition W.B Saunders
14.
15. -
Die Stone, High Strength (Type IV):
•α-hemihydrate of the “Densite” type.
•Cuboidal shaped particles & reduced surface area produce
such properties without undue thickening of mix.
•W/P ratio – 0.22 – 0.24
•Setting time - 12±4min.
•2hr Setting Expansion – Maxi. 0.10%
•1hr compressive strength – 5000psi.
Philips (1992) Science of dental materials 11th edition W.B Saunders
16. Die Stone, High Strength, High Expansion (Type
V)
Higher compressive strength than Type IV.
Setting Expansion – 0.10% - 0.30%.
W/P ratio – 0.18 – 0.22
Setting time - 12±4min.
1hr compressive strength – 7000psi.
GYPSUM HARDENER
Philips (1992) Science of dental materials 11th edition W.B Saunders
17. RESINS
EPOXY RESIN
Used effectively with rubber based impression materials
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
Philips (1992) Science of dental materials 11th edition W.B Saunders
18. PROPERTIES
Working time -15min
Setting time 1 to 12 hours depending on the products
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
Philips (1992) Science of dental materials 11th edition W.B Saunders
19. Advantages
1. More resistant to abrasion
2. 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
Philips (1992) Science of dental materials 11th edition W.B Saunders
20. 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
Philips (1992) Science of dental materials 11th edition W.B Saunders
21. 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
Philips (1992) Science of dental materials 11th edition W.B Saunders
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
Philips (1992) Science of dental materials 11th edition W.B Saunders
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)
Philips (1992) Science of dental materials 11th edition W.B Saunders
24. SILVERPLATED DIES
Silver plating is done over rubber based
impression materials
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
COMPOSITION OF THE SOLUTION
Silver cyanide - 36gm
Potassium cyanide - 60gm
Potassium carbonate - 45gm
Water (distilled) -1000ml
Silver plated dies marginal accuracy of cast restorations J Prosth Dent 51;1984: 768-772
25. 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
Silver plated dies marginal accuracy of cast restorations J Prosth Dent 51;1984: 768-772
26. 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
Comparision of surface detail reproduction of flexible die materials J Prosth Dent 1998; 80:485-9
27. 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
Philips (1992) Science of dental materials 11th edition W.B Saunders
28. 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
Philips (1992) Science of dental materials 11th edition W.B Saunders
29. METAL SPRAYED DIES
A bismuth – tin alloy which melts at 138oCcan 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
Philips (1992) Science of dental materials 11th edition W.B Saunders
30. CAST & DIE SYSTEMS
1) Working cast with removable die
i. Straight dowel pin
ii. Curved dowel pin
iii. Di-lok tray
iv. Pindex system
2) Working cast with separate die
3) DVA model system
4) Zeiser model system
Shillenberg (1981) Fundamentals of fixed prosthodontics 3rd edition Quintessence
31. STRAIGHT DOWEL PIN
The brass dowel pin is one of the most
accurate dowel types in terms of
resisting horizontal displacement and
the second lowest in vertical deviation of
four types of removable dies.
A dowel pin is positioned over each
prepared tooth in the impression.
Place a dowel between
the arms of a bobby.
Shillenberg (1981) Fundamentals of fixed prosthodontics 3rd edition Quintessence
32. Push a straight pin between the arms of the
bobby pin and into the impression material on
both the buccal and the lingual surfaces of
each tooth to have a dowel pin placed over it.
Stabilize the dowel in the bobby pin.
Pour die stone into the impression, filling the
impressions of the teeth and covering the
knurled end of the dowel pin.
The pin should parallel the long axis of the
preparation.
Shillenberg (1981) Fundamentals of fixed prosthodontics 3rd edition Quintessence
33. When the stone is hard and dry, use a
saw frame with a thin blade
There should be a cut on the
mesial and distal side of each die,
and the cuts should taper toward
each other slightly from
occlusal to gingival.
Take the die form the cast and trim away excess stone gingival to
the finish line.
Complete the trimming of the die with a no.25 blade in the
laboratory knife and then mark the finish line with the red pencil.
Repeat the procedure for each die on the cast.
Shillenberg (1981) Fundamentals of fixed prosthodontics 3rd edition Quintessence
34. CURVED DOWEL PIN
To install pin before pouring the impression, use finger
pressure to insert tip of dowel into large opening of
position bar.
Hold the bar faciolingually, so that head of the dowel is
1-2mm into the proposed area of impression.
The tail of dowel extends facially; however if the tooth
is linguoversion, turn it towards lingual side for easy
removal.
Shillenberg (1981) Fundamentals of fixed prosthodontics 3rd edition Quintessence
35. Insert a straight pin into one of 3 holes into the facial
aspect of bar and into the facial flange of impression and
another pin into lingual flange through lingual holes of bar.
The dowel should not touch the impression and its head
should be parallel to long axis of prepared tooth or teeth.
This procedure is repeated for all abutments and pontic
areas.
One pin is placed near the center of each segment of
unprepared teeth, this wall help in removal of segment for
better access of gingival wax pattern.
Impression is poured with die stone until it covers heads of
dowel. This will fill the impression about 4 mm above
gingival finish line.
The straight pins and positioning bar are removed as soon
as stone is set.
Shillenberg (1981) Fundamentals of fixed prosthodontics 3rd edition Quintessence
36. To assist in orienting each large segments
of unprepared teeth, cut a 2mm deep hole
on either side of each dowel with a large
acrylic bur.
Petrolatum is applied on stone and also an
exposed part of dowel for easy separation
from the base.
Shillenberg (1981) Fundamentals of fixed prosthodontics 3rd edition Quintessence
37. •Impression is boxed, allowing the tails of
the dowels to extend slightly through the
heat softened wax.
•Fill the boxed impression with dental stone. The dowel should be covered by at
least 2mm of stone.
•After the stone has hardened, make vertical
saw cuts on either side of each die.
•A die is removed by
pressing the dowel
Shillenberg (1981) Fundamentals of fixed prosthodontics 3rd edition Quintessence
38. TO PLACE THE DOWELS AFTER THE
CAST HAS BEEN MADE.
•Pour the impression with die stone to form
a horseshoe shaped working cast.
•Trim the bottom of cast flat to level 10mm
from the necks of teeth.This is done
because thin cast are easy to saw and
short dowels are more stable than larger
ones.
•Drill a 5mm deep hole in the bottom of the
cast directly under the center of each
prepared tooth, pontic area, and segment
containing unprepared teeth.
•This can be made with 2mm diameter drill
in hand piece or drill press.
Shillenberg (1981) Fundamentals of fixed prosthodontics 3rd edition Quintessence
39. •Clean the dowel holes, insert the curved
dowel pin properly and then adjusted for
proper fit.
•Cement the dowels into holes one at time
with placing a drop of cyanoacrylate
cement into each hole.
•The head of a curved dowel is seated into the
holes.
•Seat the heads completely with tail pointing facially.
•Then same procedure of pouring base and preparing dies
is repeated
Shillenberg (1981) Fundamentals of fixed prosthodontics 3rd edition Quintessence
40. PINDEX SYSTEM(Coltene/Whaledent,Mahwah,NJ)
In the pindex system a reverse drill
press is used to create a master cast
with dies that can be removed and
replaced repeatedly with great precision.
The impression is poured without
positioning and attaching dowel pins
beforehand.
The machine accurately drills parallel
holes from the underside of trimmed
cast.
Shillenberg (1981) Fundamentals of fixed prosthodontics 3rd edition Quintessence
41. PINDEX SYSTEM
Diagram showing the pindex machine
Shillenberg (1981) Fundamentals of fixed prosthodontics 3rd edition Quintessence
42. •Pour the impression, adding approximately
20mm of stone.
•Wet the cast prior to trimming
•Then trim the bottom of the cast, resting
the heels on the table of the trimmer.
•It should sit perfectly flat on a
tabletop, and its thickness must be a
minimum of 15mm.
Shillenberg (1981) Fundamentals of fixed prosthodontics 3rd edition Quintessence
43. •Periphery of the cast should be trimmed.
•Remove any excess stone in the
palate/tongue area with an arbor band on a
lathe.
•The lingual border of the cast should taper
slightly toward the base to facilitate
removal of the dies from the cast later.
•The faciolingual width -20mm.
•Use a pencil mark the desired location of
the pins on the occlusal surfaces of the
teeth or preparations.
Shillenberg (1981) Fundamentals of fixed prosthodontics 3rd edition Quintessence
44. •Place the prepared cast on the worktable and
align the first pencil mark with the illuminated
dot from the light beam director.
•Using both hands, exert firm downwards
pressure on the cast with thumbs.
•Raise the handle bar with slow, even pressure
and the drill assembly moves upwards cutting
the pinholes.
•When proper depth is achieved, red light goes
off.
•Same procedure is repeated with each mark.
•For better results, cast is made slightly damp
to prevent dust formation.
Shillenberg (1981) Fundamentals of fixed prosthodontics 3rd edition Quintessence
45. •Compressed air and brush is used to
remove debris from holes.
The pin holes are refined with hand reamer.
•Cyanoacrylate cement is placed on the pins prior to
cementing the pin tips.
•Shorter pins are placed before the long
pins in lingual or palatal holes and long
pins in the facial holes.
Shillenberg (1981) Fundamentals of fixed prosthodontics 3rd edition Quintessence
46. •White sleeves are placed on the long pins and gray
sleeves on the short pins.
•The bottom of the cast is lightly coated with
the petrolatum.
•Gray sleeves are blocked with small
amount of molten wax to prevent the
sleeve from filling with stone when
secondary base is added.
•Strip of utility wax along the ends of the long pins
to facilitate removal of the dies later.
Shillenberg (1981) Fundamentals of fixed prosthodontics 3rd edition Quintessence
47. •A palatal or tongue filler is made of boxing wax.
•The filler is seated to the cast.
•Boxing wax is applied aaround the cast.
•Base is poured with the die stone.
Shillenberg (1981) Fundamentals of fixed prosthodontics 3rd edition Quintessence
48. •When stone becomes hard, the cast is seated in the
base former.
•Saw cuts are premarked with the pencil.
•Then dies are sectioned from the underside.
•It may also be sectioned from the occlusal
aspect.
Shillenberg (1981) Fundamentals of fixed prosthodontics 3rd edition Quintessence
49. After the die are sectioned, trim them in a
conventional manner.
Mark the finish line with red pencil.
Apply die hardener and die spacer.
Then place the completed cast on the
articulator and then cast is ready for
fabrication of the wax pattern.
Shillenberg (1981) Fundamentals of fixed prosthodontics 3rd edition Quintessence
50. DI-LOK TRAY SYSTEM
A snap apart plastic tray with internal orienting
grooves and notches is used to reassemble
working cast and dies.
Shillenberg (1981) Fundamentals of fixed prosthodontics 3rd edition Quintessence
51. TECHNIQUE
The cast should be poured in a U shape, with no stone
in the center building it up to 2.5cm. (1.0 inch)
A lingual side of the cast base is trimmed with an arbor
band.
Horizontal grooves are cut in the base to for retention.
When stone has set for 1 hr, separate it from impression.
Cast is trimmed in horseshoe configuration to fit in Di-lok
tray and the buccal border is tapered towards base with
arbor band.
Shillenberg (1981) Fundamentals of fixed prosthodontics 3rd edition Quintessence
52. Soak the base of cast with water for 5
min.
Pour the base in tray, until ¾ of its is
filled
Seat the cast on tray; in such a way that
cervical line of the prepared teeth should
be approximately 4mm above the level
of base.
Wipe off the excess stone.
Allow the stone to set until it is hard and
dry .
To complete the dies, the cast must be
removed from the tray.
Shillenberg (1981) Fundamentals of fixed prosthodontics 3rd edition Quintessence
53. •Disassemble the tray by lifting the back
up, and then slide the buccal segment
forward.
•Then with a saw frame and a thin saw blade,
cut between the prepared tooth and the
adjacent tooth.
•The saw cut should start in the interdental
papilla area and extend downward on a very
slight taper.
•The occlusal saw cut should extend three-
quarters of the way through the stone base.
•Use finger pressure to break the die and
attached teeth from the cast.
Shillenberg (1981) Fundamentals of fixed prosthodontics 3rd edition Quintessence
54. •Remove excess stone gingival to the
finish line with a pear-shaped acrylic bur.
•Then cast and dies are
reassembled in the tray.
•Then the cast and tray mounted on the
articulator.
•When the stone has set, the articulated cast in the Di-lok tray is
ready for the fabrication of the wax pattern.
Shillenberg (1981) Fundamentals of fixed prosthodontics 3rd edition Quintessence
55. WORKING CAST WITH
SEPARATE DIE(MULTI-POUR
TECHNIQUE)
ADVANTAGES
Simple
Slightly more accurate.
Minimum trimming.
DISADVANTAGES
Difficult to transfer complex or fragile wax
patterns from cast to die.
Seating the pattern on the cast may be
problematic.
Technique can be used with elastomeric
impression materials.
Rosensteil (2001) Contemporary Fixed Prosthodontics 3rd edition Mosby
56. The area of preparation is poured with
the stones in small increments.
When set,it is separated.A second pour
is then made of the entire arch.
•The first pour which is more accurate is
trimmed into a die with a handle.
•A properly trimmed die handle is slightly
larger in diameter than the preparation
Rosensteil (2001) Contemporary Fixed Prosthodontics 3rd edition Mosby
57. •Improperly trimmed die with a handle that
meets the preparation at an angle
•Handle should be 1 inch long
•The die is trimmed with an acrylic bur
•Shaping of the handle near the finish line is completed with a
scalpel
•The die is smoothened below the finish
line with the discoid end of a tanner carver
•The prepared finish line on the die should be outlined with a red
pencil.
•Die relief agent is painted on the preparation-20 to 40
mm
Rosensteil (2001) Contemporary Fixed Prosthodontics 3rd edition Mosby
58. DVA Model System:-
Trimmed impression on Marking dowel pin locations
alignment fixture. on clear plate
Drilling holes for dowel pins Inserting dowels in the
as marked baseplate
Rosensteil (2001) Contemporary Fixed Prosthodontics 3rd edition Mosby
59. Impression is poured, stone placed around dowel pins &
alignment fixture replaced over poured impression
Set cast is removed from baseplate
Rosensteil (2001) Contemporary Fixed Prosthodontics 3rd edition Mosby
60. Cast is trimmed Cast is sectioned
Trimmed working casts using the DVA Model
System
Rosensteil (2001) Contemporary Fixed Prosthodontics 3rd edition Mosby
61. ZEISER MODEL SYSTEM
Zeiser Model System Impression is leveled, blocked out with
silicone putty,& positioned over
baseplate
Pin locations are determined &
the pinholes drilled in the base.
Rosensteil (2001) Contemporary Fixed Prosthodontics 3rd edition Mosby
62. Pins are inserted into the Impression is poured
base.
Base is inverted into the
stone
Rosensteil (2001) Contemporary Fixed Prosthodontics 3rd edition Mosby
63. Cast is separated from the impression when set &
then separated from the base.
Sectioned cast
Precision saw aids
sectioning Rosensteil (2001) Contemporary Fixed Prosthodontics 3rd edition Mosby
64. BIBLIOGRAPHY
1. Philips (1992) Science of dental materials
11th edition W.B Saunders
2. Rosensteil (2001) Contemporary Fixed
Prosthodontics 3rd edition Mosby
3. Shillenberg (1981) Fundamentals of fixed
prosthodontics 3rd edition Quintessence
4. Silver plated dies marginal accuracy of
cast restorations J Prosth Dent 51;1984:
768-772
5. Comparision of surface detail reproduction
of flexible die materials J Prosth Dent
1998; 80:485-9
6. An investigation of epoxy resin dies J
Prosth Dent 1980;44:45-9