When a good impression of the prepared tooth has been made in the mouth, it's important that it may be handled properly to obtain accurate and detailed casts. As the direct fabrication of patterns for extra-coronal restorations in the mouth is inconvenient, time-consuming, and virtually impossible, all the wax patterns are made in the laboratory using the indirect technique. This requires an accurate working cast with removable dies with a detailed reproduction of prepared tooth, and soft tissues to produce restorations that fit as accurately as possible.
4. DIE: The positive reproduction of the form of a prepared tooth in any
suitable substance. (GPT-9)
A reproduction of a prepared tooth made from a gypsum product, epoxy
resin, a metal or a refractory material (Philips).
4
Definitions
5. Die spacer: An agent applied to a die to provide
space for the luting agent in the finished casting.
(GPT-9)
Electroplating:
The process of covering the surface of an object with a thin coating of metal by means
of electrolysis (GPT-9)
5
6. Die preparation:
According to Shillingburg,
Die preparation involves trimming the die apical to the finish
line of the preparation to facilitate good axial contours in the
finished restoration.
7. PAGE 7Rosensteil SF, Land FM, Fujimoto J. Contemporary fixed prosthodontics.3rded. St.Louis:Mosby;2001
8. It must reproduce the prepared
tooth.
All surfaces must be accurately
duplicated.
No bubbles or voids.
Rosensteil SF, Land FM, Fujimoto J. Contemporary fixed prosthodontics.3rded. St.Louis:Mosby;2001 PAGE 8
9. 4. The remaining unprepared tooth structure
immediately cervical to the finish line should be
easily discernible on the die.
5. Adequate access to the margin is imperative
Rosensteil SF, Land FM, Fujimoto J. Contemporary fixed prosthodontics.3rded. St.Louis:Mosby;2001
PAGE 9
10. Rosensteil SF, Land FM, Fujimoto J. Contemporary fixed prosthodontics.3rded.
St.Louis:Mosby;2001
PAGE 10
11. 1. It must reproduce both prepared and
unprepared tooth surfaces.
2. The unprepared teeth immediately
adjacent to the preparation must be free of
voids.
Rosensteil SF, Land FM, Fujimoto J. Contemporary fixed prosthodontics.3rded. St.Louis:Mosby;2001 PAGE 11
12. 3. All surfaces of any
teeth involved in anterior
guidance and the occlusal
surfaces of unprepared
teeth must allow for
precise articulation of the
opposing casts.
Rosensteil SF, Land FM, Fujimoto J.
Contemporary fixed prosthodontics.3rded.
St.Louis:Mosby;2001
PAGE 12
13. 4. All relevant soft tissues should be
reproduced in the working casts
including edentulous spaces and residual
ridge contours that will be involved in
fixed prosthesis.
5. Must be bubble free, especially along
the finish lines of the prepared teeth
Rosensteil SF, Land FM, Fujimoto J. Contemporary fixed prosthodontics.3rded. St.Louis:Mosby;2001 PAGE 13
14. 6. The casts must be trimmed to
ensure access for carving wax pattern
margins.
7. Each cast must have a base that
allows firm attachment to the
articulating instrument
Rosensteil SF, Land FM, Fujimoto J. Contemporary fixed prosthodontics.3rded. St.Louis:Mosby;2001 PAGE 14
15. DIE MATERIALS2,3
Phillips, RW. Skinner's Science of Dental Materials. 11th ed. The WB Saunders Co, Philadelphia; 1982.
Rosensteil SF, Land FM, Fujimoto J. Contemporary fixed prosthodontics.3rded. St.Louis:Mosby;2001
PAGE 15
17. Stone die or gypsum die
Amalgam die
Acrylic or epoxy resin dies
Electroplated dies – silver plated, copper plated
Flexible die
Ceramic die
Refractory materials – gypsum bonded die material
DIE MATERIALS
PAGE 17
18. The selection of any of the materials is
determined by the following:
The impression material in use.
The purpose for which the die is to be used.
18
19. GYPSUM DIES2,3
19
Phillips, RW. Skinner's Science of Dental Materials. 11th ed. The WB Saunders Co, Philadelphia; 1982.
Rosensteil SF, Land FM, Fujimoto J. Contemporary fixed prosthodontics.3rded. St.Louis:Mosby;2001
20. Gypsum
products are
available in
five forms
(ADA Type I-
V)
Type I- Impression plaster.
Type II- Model plaster.
Type III- Dental stone.
Type IV- Dental stone with high strength.
Type V- Dental stone with high strength and
high expansion.
IV and V are used for making dies.
PAGE 20
21. Setting reaction results from the hydration of calcium
sulfate hemihydrate:
CaSO4 . ½H2O +1½H2O CaSO4 • 2H2O
+ heat (3900 cal/gm)
PAGE 21
22. Water/powder ratio: To attain maximum strength, surface hardness and a well
controlled setting expansion, it is necessary to gauge the amount of water and
powder as recommended by the manufacturer.
Type IV – 0.22-0.24;
Type V – 0.18 – 0.22
PAGE 22
24. TYPE 4
Abrasion resistant & minimum
setting expansion
Because the surface dries more
rapidly, the surface hardness
increases more rapidly than does
the compressive strength
the core of the die is tough and
less subject to accidental breakage
TYPE 5
Exhibits even higher
compressive strength
Setting expansion increased.
PAGE 24
25. Two crucial characteristics of cast and die materials, dimensional accuracy
and resistance to abrasion while wax pattern is being formed, are
adequately achieved with gypsum.
Surface detail reproduction with type IV and type V gypsum products is
acceptable for fixed prosthodontics.
26. Advantage of gypsum as die material3
Compatibility with all impression materials
Easy to use
Dimensional accuracy
Inexpensive
26
Rosensteil SF, Land FM, Fujimoto J. Contemporary fixed prosthodontics.3rded. St.Louis:Mosby;2001
27. Disadvantage of gypsum dies
Susceptibility to abrasion
Brittle prone to fracture
27Rosensteil SF, Land FM, Fujimoto J. Contemporary fixed prosthodontics.3rded. St.Louis:Mosby;2001
28. Gypsum dies can be modified:2
To make them more abrasion- resistant
To change the dimensions of the dies
To increase the refractoriness of the dies
To produce a combination of these effects
28
Phillips, RW. Skinner's Science of Dental Materials. 11th ed. The WB Saunders Co, Philadelphia; 1982.
29. 1) Methods to increase abrasive resistance2,3
Silver plating
Adding die hardener to gypsum (eg. Colloidal silica)
Treat surface with resin (epoxy, acrylic, styrene or cyanoacrylate)
Use gum arabic or calcium hydroxide mixture
Application of additives used in industrial applications
29
Rosensteil SF, Land FM, Fujimoto J. Contemporary fixed prosthodontics.3rded. St.Louis:Mosby;2001
Phillips, RW. Skinner's Science of Dental Materials. 8th ed. The WB Saunders Co, Philadelphia; 1982.
30. 2) Methods of altering die dimensions2
Addition of accelerator (potassium sulphate) &
retarder (borax)
Reduce setting expansion of type IV die stone < 0.1%
Reduce diameter of die
30
Phillips, RW. Skinner's Science of Dental Materials. 11th ed. The WB Saunders Co, Philadelphia; 1982.
31. DIE STONE –INVESTMENT
COMBINATION DIES2
Phillips, RW. Skinner's Science of Dental Materials. 11th ed. The WB Saunders Co,
Philadelphia; 1982. 31
32. Divestment (Whipmix corp) +
Die is made & wax pattern fabricated on it
Die & pattern invested in mixture of Divestment & water
eliminates possibility of distortion of the pattern on removal from
the die
When it is heated to 677oC, setting expansion is 0.9% & thermal
expansion(0.6%)
32
Phillips, RW. Skinner's Science of Dental Materials. 11th ed. The WB Saunders Co, Philadelphia; 1982.
33. Advantage
Highly accurate technique for use with conventional gold alloys
Disadvantage
Divestment gypsum bonded material not recommended for
high fusing alloys
33
34. ELECTROPLATED/
ELECTROFORMED DIES1,2,3
34
1. The Glossary of Prosthodontic Terms. J Prosthet Dent 2005 Jul;94(1):10-92
2. Phillips, RW. Skinner's Science of Dental Materials. 11th ed. The WB Saunders Co, Philadelphia; 1982
3. Rosensteil SF, Land FM, Fujimoto J. Contemporary fixed prosthodontics.3rded. St.Louis:Mosby;2001.
36. Advantages3
Hard and abrasion resistant
Dimensionally accurate
Reproduce finer details
Prevent cuspal wear due to repeated contact with opposing
cast
36Rosensteil SF, Land FM, Fujimoto J. Contemporary fixed prosthodontics.3rded. St.Louis:Mosby;2001
37. Disadvantages3
Difficult to trim
Not compatible with all impression materials
In Silver electroplating, hydrogen cyanide release can occur
Wax pattern cannot be as easily adapted as on stone.
Plating can some times tear from the cast during separation.
37
Rosensteil SF, Land FM, Fujimoto J. Contemporary fixed prosthodontics.3rded. St.Louis:Mosby;2001
38. SILVER PLATED DIES4,5
38
Myers GE. Electroformed die technique for Rubber base impressions. J Prosthet Dent 1958;8:531-535.
Morrow RM, Rudd KD, Rhoads JE. Dental Laboratory Procedures. USA:Mosby;1986
43. A)PREPARING IMPRESSION FOR PLATING:
1. The silver powder conductive coating is applied with a small inlay brush and
dusted into-
cavity and teeth areas of the impression,
interproximal papillae areas and
to the gingival and mucosal areas around the teeth
to be plated.
43
44. 2. Excess powder removed by blast of air.
(care: no excess in tip of cusps.)
3. Metal tray used should be cover with wax.
44
45. 45
4. Plating current is conducted to the silvered impression through wires that are
inserted into suitable points of impression.
5. 20 gauge Cu wires with plastic insulation
46. 46
B) PLATING THE IMPRESSION
Electrolyte placed into deeper parts of impression with a pipette
47. Distance between Anode and cathode minimum 4 inch
Current calculated on basis of 10 Ma per tooth
47
49. 49
C) POURINGCAST INTOPLATEDIMPRESSION
the stone is poured into the impression in two stages :
i) First the stone is poured into the impressions
of the teeth in which cavities are prepared and
a dowel pin is inserted into each prepared tooth .
50. 50
ii) The knurled end of the dowel is completely
immersed in the stone, and the pins are
arranged to be parallel to each other and in the
line of the long axis of the tooth.
iii) After the stone has set, any irregular areas
are trimmed and then the pins and the stone
surface are coated with a separating solution or
a thin smear of petroleum jelly. The impression
is boxed with wax and stone is poured into it.
51. 51
Silver plated die
Remaining silver flash between
teeth severed with sharp scalpel.
52. Precautions
Cyanide solution should always be kept in cupboards with no acids nearby.
Place the bath in a well-ventilated area and avoid use of all the acids near the bath.
Addition of any acid hydrogen cyanide gas toxic. Plating solution be kept alkaline.
Silver plating solution poisonous avoid contamination of hands, working area etc.
PAGE 52
53. Compared the accuracy of cast restoration fabricated on silver plated
dies and die stone dies. They concluded that marginal accuracy of
crowns fabricated on silver plated dies is statistically as accurate as
that of crowns fabricated on stone dies.8
53
Crispin et al. Silver-plated dies. Part II: Marginal accuracy of cast restorations. J Prosthet Dent 1984;51:768.
54. COPPER PLATED DIES7,8
54
7. Raymond L Cummins. A laboratory procedure for copper plating rubber base impressions. J. Prosthet. Dent. March 1975.
8. Cassimaty EM et al. Effect of three variables on the accuracy and variability of electroplated copper dies. Int J
Prosthodont 1996; ;9(6):547-54.
55. Components:
Apparatus : electrolyte bath with anode and cathode holders
Anode: pure copper
Cathode: Impression metallized
Metallizing agent:
Colloidal dispersion of graphite impression compound
Copper powder silicones
55
56. Electrolyte: acid solution of copper sulphate
Copper sulphate crystals -200 gm source of copper
Conc. Sulphuric acid- 30ml increases conductivity of
solution
Phenol sulfonic acid - 2 ml improves throwing power of
the solution
Distilled water - 1000 ml
56
57. Procedure
Same as for silver plating
Current passed is more as compared to Ag plating (5-
50mA for 10-15 hrs)
57
-
59. IF A RUBBER BASED IMPRESSION MATERIAL IS
ELECTROPLATED WITH COPPER7 :
i) The electrolyte used must be neutral or slightly acidic in reaction.
ii) The electrolyte must be heated to approx. 1150C and kept in constant
motion .
iii) A silicone separating media must be applied before coating the
impression with the metallizer.
59Raymond L Cummins. A laboratory procedure for copper plating rubber base impressions. J. Prosthet. Dent. March 1975.
60. Distancebetweencathodeandanode
Greater the distance more even quantity of Cu deposited, more readily
are deeper areas plated
4-6 inch suitable
If distance less more Cu deposited on superficial areas of impression,
leaving deeper areas inadequately plated.
60
61. Compared the accuracy of electroplated copper and stone dies and concluded
that copper plated dies were more accurate than the stone dies. Also the
stone dies were found to be oversized compared to the master die.
61
Cassimaty EM et al. Effect of three variables on the accuracy and variability of electroplated copper dies. Int J Prosthodont
1996; ;9(6):547-54.
62. PROBLEMS OF ELECTROPLATING
Faulty conduction of current Short circuit exposure of
conducting wire to the solution
Exhausted solution Plating slow
Over concentrated solution Soften surface of impression
materials
Metal anode too small Slow and irregular plating
62
63. Current too high
Gas bubbles at the surface of impression
Granular and friable deposits unsatisfactory die
Heavier deposits on areas of impression nearer to anode
Some times failure to adequately cover the deeper areas of an impression
Current too low
Satisfactory results take longer time to get necessary thickness
63
64. AMALGAM DIE2,3,5
Alloy proportioned triturated condensed in the impression
Can be used with rigid impression materials only
Advantage:
Reproduction of fine details and sharp margins is good
Hard and high abrasion resistance
64
65. Used only in copper band impressions
with modelling compound, and
Contraindicated with rubber base
impressions due to elastic properties of
the material so it will not withstand
the forces of amalgam condensation.
65
66. Disadvantage:
Only in rigid impression materials
Takes long time to reach maximum hardness
Improper manipulation can lead to significant dimensional changes in the
resulting die.
66
68. They are self curing polymeric materials with fillers.
eg:
Acrylic resin die
Epoxy resin dies
Polyester resin dies
Compatible with polysulfide or polyether impression materials.5
68
69. ADVANTAGES5 :
Better abrasion resistance
High compressive strength than dental stone.
DISADVANTAGES5 :
• More viscous than dental stone so more entrapment of air in the preparations.
• Shrink upto 0.02% on polymerization
PAGE 69
70. EPOXY RESIN1
A resin characterized by the reactive epoxy or ethyloxyline groups that
possess unique characteristics in terms of adhesion to metals, woods,
and glasses (GPT-9)
Epoxy resin die: a reproduction formed in epoxy resin (GPT-9)
70
71. EPOXY RESIN
Supplied as resin paste and liquid
activator (amine)
Trade names:
Epoxydent, Oxydental products
Epoxy die material, Dentsply
Pri-Die, Jelenko
Diemmet 71
72. 72
Working time 15 mins
Setting time 1-12 hrs (depending on product)
Shrinkage 0.03%-0.3%
Hardness (after 24hrs) 83-94 (Rockwell N)
73. Relatively long setting times,
Incompatibility with certain impression materials and
Polymerization shrinkage.
All dies aged beyond 24 hrs were found to be unsuitable for use in
precision fixed prosthodontic procedures.
739. Vermilyea SG, Huget EF. Evaluation of resin die materials. J Prosthet Dent 1979;42;304.
Compared resin die materials with die stone and concluded that advantages
offered by the strength and hardness of resin die materials are overshadowed
by9
75. They are similar to heavy bodied silicone or Polyether
impression materials and are used to make interim
restorations or indirect composite resin inlays or onlays
chairside.
75
79. ADVANTAGES3
Less time required (rapid setting)
Ease of removal of interim restoration or inlay.
DISADVANTAGES
Expensive
Surface details poor
79
80. Compared the surface detail production of flexible die material systems with stone
dies and concluded that flexible die material can produce better surface detail
reproduction the die stones.10
But if separator is used, surface detail reproduction is poor
80
10. Jack D.G. Comparison of the surface detail production of flexible die material systems (JPD 1998;80:485-9)
81. CERAMIC DIES
81
Ceramic: of or relating to the manufacture of any product made essentially
from a nonmetallic mineral (as clay) by firing at a high temperature1 (GPT-9)
82. Powder and liquid Mix in putty consistency and fill in impression Remove
after 1 hour from impression Fire at 600 oC
Advantage: Hard, strong die with high abrasion resistance
Disadvantage: High shrinkage
82
83. Compatibility of cast or Die materials with impression
materials4:
Cast or die material compatible impression material
Gypsum products Zinc- oxide eugenol
Alginate
Rubber base material
Impression plaster used by a
separator
Impression compound
83
84. Compatibility of cast or Die materials with Impression materials:
Electroplated copper Impression compound
Electroplated silver Polysulfide
Silicones
84
85. Compatibility of cast or Die materials with impression materials3,5:
Epoxy resins
Polysulfide
Polyether
85
86. Surface reproduction of details:
According to ADA specification no. 25 , the material shall reproduce a
groove 0.050 mm (50 microns) in width.
According to Ella et al., epoxy resin can reproduce even 1 micron
Resin modified gypsum- 15 micron and Type IV gypsum -20 microns
According to Craig, Epoxy dies are best for reproducing detail (10 μm),
followed by high-strength stone dies (170 μm).
88. 88
• Materials applied on the surface of die to increase the
surface hardness.
• It also prevents the die spacer from seeping into the die.
• Should have low viscosity
• Must be applied lightly
• Thickness of cyanoacrylate- 1-2.5 µm
• Thickness of acrylic lacquers- 4 -10 µm
18. Shillingburg HT. Fundamentals of fixed prosthodontics. 4th ed. Quintessence Publishing; 2012.
89. COMMONLY USED MATERIALS AS DIE HARDENERS:
•Resins like
1. Cyanoacrylate resins
2. Acrylic resin lacquer
3. Epoxy resin
4. Styrene
•Colloidal silica
•Gum arabic, calcium hydroxide mixture
89
24. Dykema RW, Goodacre CJ, Phillips RW. Modern practice in fixed prosthodontics. 4th ed. Philadelphia: W B Saunders
Company; 1986.
90. Applied to finish line area of the die to prevent abrasion by waxing
instruments during the fabrication of wax pattern
Applied with brush or PKT instrument no 1.
90
19. Fukui H, Lacy AM, Jendresen MD. Effectiveness of hardening films on die stone. J Prosthet Dent 1980:44(1);57-63.
91. Quickly blown off and dried from above
the margin toward the cervical area.
or
Blot with tissue
9119. Fukui H, Lacy AM, Jendresen MD. Effectiveness of hardening films on die stone. J Prosthet Dent 1980:44(1);57-63.
92. 1. Cyanoacrylate resins and resinous die hardeners effectively improved the hardness
and abrasion resistance of stone dies.
2. Application of liquid resins followed by blotting and/or blowing with compressed air
produced an improved surface without clinically significant dimensional change. The
extent of film buildup was qualitatively related to the viscosity of the resin
3. Application of multiple coats of resin without further blotting or other mode of
removal of the excess produced a thick film which can obliterate surface detail
92
12. Lacy AM et al. Effectiveness of hardening films on die stone. J Prosthet Dent. 1980:44:356
94. Die spacer: An agent applied to a die to provide space for the
luting agent in the finished casting1(GPT-9)
This material is applied to the die to increase the cement space
between the axial walls of the prepared tooth and the restoration3.
94
95. 12. Cho SH, Chang WG, Lim BS, Lee YK. Effect of die spacer thickness on shear bond strength of porcelain laminate veneers. J Prosthet Dent 2006;95(3):201-8.
Die spacer thickness should be adequate enough to allow for proper seating
of a restoration, but not in excess to the extent that a thicker than necessary
cement layer results.
95
96. Various materials used as die spacers
96
DVA spacer DVA spacer –
Blue & red – 12 micrometer Gold & silver – 6 micrometre
Die spacer (Kerr laboratory)
Silver metallic Pactra airplane dope (Pactra industries ,
Calif. )
Pico-fit die spacer (RenfertGermany)
Tru-fit die spacer-(George Taub products)
Lacquer
Finger nail paint
97. Optimal thickness according to various authors
20-40 micro meter (Acc. to rosenstiel 4th edi.)
Rudd and Morrow – 10-15 micro meter
Fusayama et al (JPD 1964;14;95)-thickness should not be less than 30 micro
meter.
Jorgensen et al (JPD 1966:16;740) variations of thickness from 20-140 micro
meter had only moderate influence on retention.
Eames et al (JADA 1978;96;432) – optimal thickness - 25 micro meter
PAGE 97
98. PROPERTIES3
Should flow uniformly and smoothly
Color should be readily identifiable on the die
Thinners are available to decrease the viscosity of die spacer.
98
99. Brush strokes in one direction
Wait for 2 mts before applying next coat
Should be applied 0.5-1mm short of margin
99
102. Found that grooves significantly inhibit the seating of castings,
presumably by acting as small hydraulic cylinders during cementation
process. Therefore application of spacer in groove is essential.
102
14. Tjan et al. Effect of multiple axial grooves on the marginal adaptation of full cast-gold crowns. J Prosthet Dent 1981;46;399
103. Grooves should not be die spaced because intimate adaptation of the casting
to the tooth is essential to achieve optimum resistance and retention, and
the die spacer may tend to pool in the groove and hence obliterate much of
the critical detail.
103
15. Donovan T et al. Use of paint-on die spacers in preparations with grooves. J Prosthet Dent 1984;47;606.
104. Grooves did not disrupt seating when die spacer application was
specifically omitted from grooves.
10416. W.V. Campagni et al. effect of die spacer on the seating of complete cast gold crowns with grooves. (JPD 1986;55;324
105. 105
Following crown fabrication easily removed
and a final check for fit is made on the original
clean die.
25 microns of space.
Advantage:
Eliminates see-through of undesirable die spacer
color under all ceramic crowns
Allows true verification of fit to the original die
form
PEEL-AWAY DIE SPACER
108. DIE SEPARATORS
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 preparation.
PAGE 108
110. PREPARATION OF DIE18,24,25
110
18. Shillingburg HT. Fundamentals of fixed prosthodontics. 4th ed. Quintessence Publishing; 2012.
24. Dykema RW, Goodacre CJ, Phillips RW. Modern practice in fixed prosthodontics. 4th ed. Philadelphia: W B Saunders
Company; 1986.
25. Tanquist RA. Die trimming : a guide to physiologic contour. J Prosthet Dent 1982;48(8):485-9.
111. Ditching the Die16
Ditching or trimming the die defines the position of the margin and acts
as a guide to gingival contour when the restoration is being waxed.
Excessive trimming does not give the correct emergence profile and may
lead to an over-contoured or bulky crown.
111
112. Pear shaped acrylic bur
trimmed apical to finish line
Final trimming sharp blade
Smoothened
112
120. .Shillingburg HT. fundamentals of fixed prosthodontics. 3rd ed. Quintessence Publishing
Working cast with separate die
Working cast with removable die
Working cast or definitive cast or master cast is the replica of the
prepared teeth, ridge areas and other parts of dental arch.
120
121. Working cast with separate die
Simplest method of fabrication
121
.ShillingburgHT.fundamentalsoffixedprosthodontics.3rded.QuintessencePublishing
122. ADVANTAGES
•Easy to fabricate
•Keeps relation between abutments fixed & immovable
•Better contours and emergence profile while wax pattern fabrication.
122
123. DISADVANTAGES
Wax pattern must be transferred from die to cast destroy internal
adaptation of wax
Some times difficult to seat wax pattern on the cast
- Different impressions
- Second pour –impression damaged
Can be used only with elastomeric impressions
123
125. The die is an integral component of the definitive cast and
can be lifted from the cast to facilitate access3
Precise relocation of the die is crucial to this system’s
success3
Brass pins or dowels used
125
Rosensteil SF, Land FM, Fujimoto J. Contemporary fixed prosthodontics.3rded. St.Louis:Mosby;2001
126. Advantages:
Convenient to use
Reduced chance of breakage during transfer
Various drawback of separate die are overcome
Disadvantage::
Risk of introducing error in the pattern if die does not seat accurately in the
working cast
Difficulty in sawing the die out of cast
126
127. The cast is made in two pours of type IV or V stone of
contrasting colors : the first forms the teeth and the second
forms the base of the cast. The area to be removed is coated
with the separating media before the second layer is
produced.
PAGE 127
128. Requirements:
1) Dies must return to their exact original position
2) Dies must remain stable even when inverted
3) Cast containing dies must be easy to mount on an articulator.
128
129. CONVENTIONAL DOWEL PIN SYSTEM
DI-LOK
PINDEX
DVA
BELLE DE ST. CLAIRE
ZEISER
ACCU-TRAC SYSTEM
MONO TRAC
129
OTHER DIE SYSTEMS :
130. 130
Pre pour technique
Devices are
oriented in the
impression before
it is poured
Post pour technique
Attached to the
underside of the cast
that has already been
poured
Pre pour technique
Devices are
oriented in the
impression before
it is poured
Post pour technique
Attached to the
underside of the cast
that has already been
poured
Methods of repositioning die in its working cast
131. Dowel pin : a metal pin used in stone casts to remove die
sections and replace them accurately in the original position
131
DIMENSIONS:
length – 23 mm
taper – 18 mm
head – 5 mm
136. 1. Positioning of dowel pins
Marking to act as guide in placement of pins
136
137. 2. Paralleling instrument - for alignment of dowel pins
137
Mann paralleling instrument Clamps holding Dowel pins
138. 138
Devices to position dowels before pouring impression:
needles and pins,
paper clips,
bobby pins,
wax wafers,
Match sticks
Balshi et al. Matches, clips, needles or pins. J Prosthet Dent 1975;34(4):467-72.
146. 146
The intended saw cuts are marked in pencil, and the saw blade
is carefully positioned. It must not
touch the prepared tooth.
The first pour is sawed completely through. Finishing the cut
short of the second pour will prevent a
clean separation.
155. Two pours: (contrasting colors)
155
1) Forms the teeth 2) Forms the base
Rosensteil SF, Land FM, Fujimoto J. Contemporary fixed prosthodontics.3rded. St.Louis:Mosby;2001
158. Di - Lok tray system3,19.
(Di –Equi Dental products Co)
158Miranda et al. Comparative stability of two removable die systems: J Prosthet Dent 1976;36;326
159. The full-arch Di-Lok tray can be disassembled into
three pieces:
159
1) the body of the tray which establishes arch
curvature
160. The full-arch Di-Lok tray can be disassembled into
three pieces:
160
2) outer tray perimeter which confines the poured
base to this curvature
161. The full-arch Di-Lok tray can be disassembled into
three pieces:
161
3) posterior locking bar which stabilizes the assembly
as a unit
162. The first two pieces are ribbed so that when the base is poured
the entire cast-base system has stability and accuracy
during reassembly
The initial cast must be trimmed to fit the space provided in
the tray
The trimmed cast is then notched on its sides so as to provide
additional retentive locks for the stone base
162
163. The cast is placed into the space provided in the tray, and a
base of stone is poured
Once material sets, the tray can be disassembled and the
cast removed for production of dies
163
164. A, With a single-pour technique, the impression is formed in the usual way, and the Di-Lok tray
is filled. Then the tray is inserted into the impression while the stone is still wet.
B, After the die stone has fully set, the locking and curved arms of the tray are removed. The
cast can then be removed by tapping the anterior pad of the tray base
164
165. A handsaw is used to section upto 3/4th through the
stone
Gentle finger pressure is used to “snap” the dies
apart,
leaving a small area of stone surface on each
segment that can be intimately joined to adjacent
units during reassembly
165
167. Advantages3
Use of a specially articulated tray for precise reassembly of sectioned
definitive cast
Cast pouring unimpeded
Less costlier than Pindex
167
Disadvantage3
Overall size of the tray can make articulation and manipulation difficult.
169. The Pindex system is composed of a precision
drill mechanism (aligned drill and light
source), dowel pins, and corresponding
precision plastic sleeve
169
170. 170
Base should be flat to ensure
that the Pins will be parallel
Facio-lingual width – 20 mm
171. 171
working cast is placed on the drill
table
oriented until the light beam in the
drill unit is directed to the desired
point (occlusal surface of the
proposed die)
174. 174
Shorter pins on lingual side
Longer on buccal side makes the ends of the dowel pins more accessible
for easy removal after the casts are mounted.
Collar of the pin should
be flush with the base.
181. Serrano et al. An accuracy evaluation of four removable die systems. J Prosthet Dent 1998;80:575-86.
This study evaluated the 3-dimensional accuracy of 4 removable die
systems:
Belle de St. Claire
Pindex
DVA
conventional brass dowel system
181
182. Serrano et al. An accuracy evaluation of four removable die systems. J Prosthet Dent 1998;80:575-86.
All 4 die systems provided a similar degree of dimensional accuracy,
although Pindex showed the least horizontal movement and the brass
dowel system produced the least occlusogingival reseating discrepancy.
182
183. DVA system3
The DVA Precision Model System produces totally poured and pinned
models and dies in only one pour.
Fast, simple to use, and clean method of producing dies and models of
maximum cross-arch accuracy.
This precision system compensates for the normal, distorting linear
expansion experienced by die stones during setting.
183
184. DVA system3
The DVA Precision Model System includes:
a specially designed Pin Alignment and Drilling Machine, which
determines dowel pin locations prior to the pouring of the model;
pre-manufactured Base Plates;
specially designed dowel pins.
Arch-Trimming Machine, with its own built-in vacuum and dust
collection systems
184
185. A, Trimmed impression on alignment fixture. B, Marking dowel pin locations on clear plate
185
186. C, Drilling holes for dowel pins as marked.
D, Inserting dowels in the baseplate. An adhesive is not required
186
187. F, G, Set cast is removed from baseplate &
trimmed.
187
E, The impression is poured, stone is placed around
dowel pins, and the alignment fixture is replaced
over poured impression.
H, Cast is trimmed.
188. Advantages Disadvantages
Compensates for expansion of
cast
Single pour needed
Removable die
188
• Special equipment needed
• Quite technique sensitive
196. Accu- Trac Die Precision System (Coltène Whaledent)
196
-
https://www.coltene.com/fileadmin/Data/EN/Products/Laboratory/Modelmaking/Accu-Trac_Model_System/ACCUTRAC
197. Accu- Trac Die Precision System (Coltène Whaledent)
197
-
The ACCU-TRAC System makes the fabrication of
precision models and dies easier.
The model and base are poured as one, eliminating
the additional work when using pins and sleeves.
Saves time & material & is precise
203. ADVANTAGES
One universal tray size
Low base height
One pour technique
Economical
Numerical die location
Open bottom tray
203
204. TROUBLE SHOOTING13 (Rudd & Morrow)
PROBLEM:
204
Voids or bubbles
in cast
Stone not vacuum
mixed
Stone added to
impression too
rapidly
205. TROUBLE SHOOTING13 (Rudd & Morrow)
PROBLEM:
205
Removable dies
fracturing at neck
Dowel pin placed
too deep in
impression
Die ditched too
deeply
206. TROUBLE SHOOTING13 (Rudd & Morrow)
PROBLEM:
206
Removable die
rotating in
working cast
Dowel pin too
short in base of
cast
Base of die
lacking positive
seat
207. TROUBLE SHOOTING13 (Rudd & Morrow)
PROBLEM:
207
Unable to remove
dies after saw
cuts are made
Saw cuts not
tapered
Adjacent natural
teeth restricting
removal of die
208. TROUBLE SHOOTING13 (Rudd & Morrow)
PROBLEM:
208
Removable die
unable to seat
completely on die
Debris in pinhole,
on pin, on base,
209. Dies for CAD CAM systems30
30. Christensen GJ. Will Digital Impressions Eliminate the Current
Problems With Conventional Impressions. Canadian Journal of
Restorative dentistry and prosthodontics 2009 209
210. Problems with conventional methods30
210
Remake dies
digital impression concept allows retention of
the digital information in appropriate computer
storage as soon as it is received
222. REFERENCES
1. The Glossary of Prosthodontic Terms. J Prosthet Dent 2005 Jul;94(1):10-92.
2. Phillips, RW. Skinner’s science of dental materials. 11th ed., Philadelphia: The WB Saunders Co;
1982.
3. Rosensteil SF, Land FM, Fujimoto J. Contemporary fixed prosthodontics. 3rd ed. St.Louis: Mosby;
2001.
4. Craig RG. Restorative dental materials. 9th ed. St. Louis: Mosby; 1993.
5. Mason HJ. Impregnation of stone dies with acrylic resin. J Prosthet Dent 1970;23:96-8.
222
223. REFERENCES
6. Myers GE. Electroformed die technique for Rubber base impressions. J Prosthet
Dent 1958;8:531-5.
7. Crispin et al. Silver-plated dies. Part II: Marginal accuracy of cast restorations. J
Prosthet Dent 1984;51(6):768-73.
8. Cassimaty EM et al. Effect of three variables on the accuracy and variability of
electroplated copper dies. Int J Prosthodont 1996; ;9(6):547-54.
9. Gerrow JD , Price RB. Comparison of the surface detail reproduction of flexible
die material systems. J Prosthet Dent 1998;80(4):485-9.
223
224. REFERENCES
10. O’Briene WJ. Dental materials and their selection. 3rd ed. Quintessence Publication; 2002.
11. McCabe JW, Walls AWG. Applied dental materials. 8th ed. Blackwell Science; 1998.
12. Cho SH, Chang WG, Lim BS, Lee YK. Effect of die spacer thickness on shear bond strength of porcelain
laminate veneers. J Prosthet Dent 2006;95(3):201-8.
13. Morrow RM, Rudd KD, Rhoads JE. Dental laboratory procedures fixed partial dentures. 2nd ed. USA
Mosby;1986
14. Eames WB, G’Neal SJ, Monteiro J, Miller C, Roan JD Jr, Cohen KS. Techniques to improve the seating of
castings. J Am Dent Assoc 1978;96:432-7.
15. Fusayama T, Ide K, Hosada H. Relief of resistance of cement of full cast crowns. J Prosthet Dent 1964;14:95-
106.
16. Bassett RW. Solving the problems of cementing the full veneer cast gold crown. J Prosthet Dent
1966:16(4);740-7. 224
225. REFERENCES
17. Campagni WV, Preston JD, Reisbick MH. Measurement of paint-on die spacers used for casting relief. J
Prosthet Dent 1982;47:606-11.
18. Shillingburg HT. Fundamentals of fixed prosthodontics. 4th ed. Quintessence Publishing; 2012.
19. Fukui H, Lacy AM, Jendresen MD. Effectiveness of hardening films on die stone. J Prosthet Dent
1980:44(1);57-63.
20. Li-Hong et al. A micro-mechanical evaluation of the effects of die hardener on die stone. Dental Materials
Journal 2010;29(4): 433–7.
225
226. REFERENCES
21. Miranda FJ, Diltis WE, Duncanson MG, Collard EW. Comparative stability of two removable die
systems. J Prosthet Dent 1976;36(3):326-33.
22. Serrano et al. An accuracy evaluation of four removable die systems. J Prosthet Dent 1998;80:575-
86.
23. Sivakumar et al. A comparison of the accuracy of three removable die systems and two die materials.
European Journal of Prosthodontics and Restorative Dentistry 2013;21(3):115-9.
24. Dykema RW, Goodacre CJ,Phillips RW. Modern practice in fixed prosthodontics. 4th ed. Philadelphia:
W B Saunders Company; 1986.
25. Tanquist RA. Die trimming : a guide to physiologic contour. J Prosthet Dent 1982;48(8):485-9.
226
227. REFERENCES
22. Li-Hong et al. A micro-mechanical evaluation of the effects of die hardener on die stone. Dental
Materials Journal 2010; 29(4): 433–437.
23. Shillingburg HT. fundamentals of fixed prosthodontics. 3rd ed. Quintessence Publishing
24. Available at: http://www.usdentaldepot.com
25. Millstein P. A Comparison of Two Die Systems Using Prepour and Postpour Pin Placement.
Quintessence of Dental Technology 2004:195-200.
26 Comparative stability of two removable die systems: J Prosthet Dent 1976;36;326
27. Serrano et al. An accuracy evaluation of four removable die systems. J Prosthet Dent 1998;80:575-86.
28. Sivakumar et al. A comparison of the accuracy of three removable die systems and two die materials.
European Journal of Prosthodontics and Restorative Dentistry 2013;;21(3):115-119.
29. Available at: http://whipmix.com/wp-content/uploads/via-product-catalog/product_docs/Gypsum
30. Christensen GJ. Will Digital Impressions Eliminate the Current Problems With Conventional
Impressions. Canadian Journal of Restorative dentistry and prosthodontics 2009.
31. Available at: https://www.youtube.com/watch?v=L6Ornv6a79w
227
Editor's Notes
When good impression of the prepared tooth have been made in the mouth, its important that it may be handled properly to obtain an accurate and detailed casts. As the direct fabrication of patterns for extra-coronal restorations in the mouth is inconvenient, time consuming and virtually impossible, all the wax patterns are made in the laboratory using the indirect technique. This requires an accurate working cast with removable dies with detailed reproduction of prepared tooth, and soft tissues to produce restorations that fit as accurately as possible.
electrolysis is the process in which the current is passed bw 2 electrodes through an ionized solution that is electrolyte.
First of all , there is no definite definition for die preparation..
.
All the surfaces of the teeth that are involvd in anterior guidance and the occlusal surfaces of the unprepared teeth must follow precise articulation of the opposing casts.
4. Means 0.5 to 1mm visible enough must be present to help the technician establish the correct cervical contour of the restoration.
Diagram: To facilitate trimming, the impression should extend beyond the preparation margin. A properly trimmed die must have the same cervical contour as the tooth. (The dark yellow area indicates the parts of the die to be removed during trimming.)
THE CAST THAT WILL BE USED TO MAKE THE FIXED RESTORATION MUST MEET CERTAIN REQUIREMENTS
FOR EXAMPLE: IF WE HAVE VOIDS ON PROXIMAL SURFACE THEN WE FACE DIFFICULTY OR WE LAND UP IN MAINTANING IMPROPER CONTACTS WITH THE ADJACENT TOOTH AS WE DON’T HAVE THE REFERENCE.
Compatibility is specific and germane only to the particular brand rather than to chemical types of impression materials.
Moreover, in the case of filled autopolymerizing acrylic resins, the curing contraction is excessive (0.6 linear percent for one material). Therefore acrylic ]resin cannot he used when an accurate die is required. The same is true for polyester resin materials.
In some cases the resin die should be no more undersized than the stone die is oversized. However, this issue must be taken into consideration, because it may be necessary to adjust the investing and casting technique accordingly. A cast crown that is fabricated on a slightly undersized resin die may not seat completely on the tooth compared with one made on a slightly large stone die.
Metal dies produced from electroplated impression material have moderately high strength, adequate hardness, and excellent abrasion resistance. Detail reproduction of a line 4 pm or less in width is readily attainable on an electroplated die when a nonaqueous elastomeric impression material is used.
The physical properties of die stone are improved over the dental stone because less water is required to obtain a sufficiently fluid mix.
The most commonly used die materials are ‘type IV (dental stone, high strength) and Type V (dental stone, high strength, high expansion) improved stones.
'These materials are relatively inexpensive, easy to use, and generally compatible with all impression materials. Certified ‘type IV stones have a setting expansion of 0.1% or less, whereas the harder 'Type V stones expand as much as 0.3% in accordance with ANSI/ADA Specification No. 25.
TYPE V- This greater expansion is useful for compensation of the relatively large solidification shrinkage of base metal alloys.
The W:P ratio is a very important factor in determining the physical and chemical properties of the set gypsum product. For example, higher the water/powder ratio, the longer will be setting time and weaker will be the gypsum product. This is because there is more water per unit volume and less nuclei of crystallization per unit volume.
The strength that is obtained is reached maximum only after 15 seconds of mechanical mixing as compared to the hand mixing.
HAND MIXING - Measured amount of water is placed in the bowl & weighed powder is sifted into the water.The mixture is then vigorously stirred with periodic wiping of inside of bowl with spatula:to ensure wetting of all powder breaking of any agglomerates or lumps.
In MECHANICAL MIXING-Repeatedly adding water & powder by guesswork should be avoided yields lower strength & may cause distortion
Measured water added to the bowl followed by Gradual addition of pre-weighed powder within 15seconds.
For 20-30 seconds mechanical mixing under vacuum in performed.
TYPE V –
Indicated - when inadequate expansion achieved during cast crown fabrication
Contraindicated – dies for inlays ( higher expansion leads to tight fit)
TYPE V- This greater expansion is useful for compensation of the relatively large solidification shrinkage of base metal alloys.
Type IV During carving of a wax pattern
The two crucial characteristics of cast and die materials is dimensional accuracy and resistance to abrasion while the pattern is being formed.
The disadvantage for gypsum dies is relatively resistant to abrasion.
These chemical act by forming an adsorbed layer on the hemiydrate to reduce its solubility and on the gypsum crystals to inhibit growth.
Linear expansion gypsum, - .06% to 0.5% max.
Another technique for modifying the gypsum dies employs a die material and an investing medium mixed with a colloidal silica to form the divestment .
Die material and investing media . (commercial gypsum bonded material )+(blend of gypsum and silica)
Because divestment is gypsum bonded , it is not recommended for high fusing alloys like metal ceramic restorations but for conventional gold alloys .
Gypsum -Provides rigidity and acts as binder for remaining materials. Does not possess the needed refractory properties.
Silica: does not possess strength to withstand necessary manipulation and is employed because of its properties of setting and thermal expansion
High fusing alloys that are used with metal-ceramic restorations because of
Contamination
Undersized coping
Release of sulfur dioxide gas.
The area to be electroplated is coated with the powdered silver or copper or graphite to make them a good conductor of electricity and the impression is poured in the electroplating bath.
The basic system consist of electrolytic solution of copper sulfate or silver cyanide and a source of direct current.
the time that is required to produce a cohesive film is 8 hrs.
(JPD 1958;8;531)
Components:
Apparatus : electrolyte bath with anode and cathode holders
(Same apparatus used for both Cu and Ag plating. Silver plating lower current setting)
Anode: pure silver Cathode: Impression metallized
Silver cyanide solution is used. If greated surface detail reproduction is required – silver nitrate solution can be used.
Surface of the impression is treated with the graphite or silver so that it conducts electricity- metallizing. Applied with camel hair brush.
Electrolyte: Silver cyanide plating solution (Alkaline solution)
Metalizing agent: fine Ag powder or dispersion of silver powder in volatile liquid or powdered graphite.
Not all impressions are suitable for plating. Hydrocolloid are diffilcult to electroplate (Philips)
Because of their low surface energies silicones are difficult to electro plate evenly.
Polyether and hydrocolloids can not be electroplated because of their hydrophilic nature, imbibe water and become distorted there fore cannot be electroplated accurately.
(alkaline solution soften surface)
If remain exposed it will acquire a thin layer of silver coating.
This is not detrimental but over a period of time it wastes a considerable amount of silver.
The wires are placed on either side of the area of the impression containing the cavity preparations and far enough away from the prepared teeth to avoid any distortion.
The shorter pointed end of the wire is pushed into the rubber base impression until the insulation on the wire is flush with the impression. Wire Is stabilized by twisting them.
After the impression is silvered and the wires are attached, the impression is ready to be placed into the bath.
The pippete is used to place small solution into the impression to avoid retention of air bubbles.
Placed into the bath and connected to the electrode.
If no mucosa involved 5-7 ampere current.
If distance less more Ag(silver) deposited on superficial areas of impression, leaving deeper areas inadequately plated.
Deposition of Ag rapid at end of 5 mins complete covering attained
An impression that contains the electroformed die surface is then filled with dental stone.
When the stone hardens. It is mechanically locked into the rough interior of the electroformed metal shell.
The impression material is then removed to provide a die with greater surface hardness and resistance to abrasion.
The model and die are prepared in the normal manner and margins of the die are trimmed with a finishing disk.
An impression that contains the electroformed die surface is then filled with
dental stone.
When the stone hardens. It is mechanically locked into the rough interior of the electroformed metal shell.
The impression material is then removed to provide a die with greater surface hardness and resistance to abrasion.
The model and die are prepared in the normal manner and margins of the die are trimmed with a finishing disk.
Fumes of extremely toxic hydrocyanic acid.
However rudd n morrow says that the silver plated dies are not significantly more accurate than the stone dies because of the possibility of the continued polymerization and distortion of the impression during electroplating may lead to significant dimensional changes in the impression.
Withstand condensation pressure
ACRYLIC RESIN DIE IS AVAILABLE AS POWDERED POLYMER WITH LIQUID MONOMER
EPOXY RESIN IS AVAILABLE AS A JAR OF RESINS AND SYRINGE OF HARDNER.
Incompatible with hydrocolloids because water retarded the polymerization of the resin.
So the resin die can be smaller than the prepared tooth and unles the dentist make some adjustment for this situation during investing and casting, it can be clincally significant.
Temp. rise 16 degree C in 25 mins
Eg:Poly vinyl siloxane medium body impression materials
Model sectioned to allow proximal access for contouring
Restoration removed from flexible die
This study depicted that the use of a separator is necessary when using systems with polyvinyl siloxane materials for both the impression and the die.
When no separator was used, the polyvinyl siloxane impression materials were found to be incompatible with the polyvinyl siloxane die materials because the dies failed to separate from the impression. When a separator was used, the impression did separate from the die material, but the detail reproduction was significantly worse than the control dies.
Impression material compatible with gypsum products are..
Epoxy resion can be poured on impression made with polysulfide and polyether impression material
If not applied carefully , can form excessively thick surface layer. .it will create a n unacceptably thick relief over the finish line resulting in ill fitting margin.
He applied three different cyanoacrylate resin die hardeners and two acrylic resins lacquer.
He found that All the materials were less than 25 micron thick. This thickness could be considered the upper limit of acceptability from a clinical standpoint
The study concluded that a film thickness of less than 25 microns should be acceptable limit for die hardeners
.
Cyanoacrylate resins are inexpensive, easy to apply, and seem to provide clinically inconsequential thickness of protective film over dry stone dies, preventing abrasion of sharp margins.
This study investigated four products used to influence the hardness, surface topography, and abrasion resistance of the treated dies, and also to
measure the increased thickness. (Eastman, krazyglue, superglue and die hardner)
For adequate amrgianl adaptation, a band of 1mm immediately adjacen to finish line is left unpainted.
DVA spacer - Blue & red – 12 micrometre
Gold & silver – 6 micrometre
1st step application of clear die spacer over all of the axial surface and occlusal surface. They recommend extending the first layer above and beyond the marginal line in order to protect the marginal line against mechanical damage. After drying of the first layer apply the color die spacer in an even cover ending circularly about 1 mm before the marginal line on axial surface and also over the occlusal surface. It should be applied in one direction.
The direct role of hydrostatic pressure is resisting crown seating .
Dis spacing is essentiall to allow for the hydrodynamics of the cementation procedure.
The Perfectim Systems Peel-Away Die Spacer Kit includes a paint-on die hardener, two die spacers, respective
thinners and applicators, and die lubricant in a convenient storage tray.
Due to ditching, angulation may be exaggerated due to undercut as the finishing instrument rest against the die and hence a thick gingival area in the restoration will result
Begin final trimming of the die wtith a sharp 25 no. blade
The area apical to the finish line should be smoothened with a Tanner carver
We Start 2mm below finish line i. e. apically the preparation carried out under light pressure with good finger rest. Finger rest is essential to prevent accidental distortion of finish line. Engage the bur such that it is prepared 2mm below the finish margin. Here, we are preparing so as to undermine the stone that compromise the free gingival margin.
Here Pear-shaped acrylic bur trimmed apical to finish line
Smoothened with the discoid end of the tanner carver, without engaging the margin.
After the die has been trimmed, the finish line is marked with the sharp colorbite red pencil. It facilitates carving the margins of wax pattern. The color should contrast with that of the wax used. Ordinary lead pencil not used because: (Rosenstiel) darker color can interfere with efforts to verify that wax has been properly adapted to the margin. When used with blue or green inlay, finish line outlined in black doesn't become evident , infact it makes the margin appear unsealed or open.
Dark color wont give contrast to wax
Traces of graphite can be carried to investment on pattern which could contaminate the margin of the casting
These marked margin can then be coated with low viscosity cyanoacrylate resin
If reversible hydrocolloid is used, separate impressions needed for cast & die
Wax pattern need not be removed from the resp. dies when transferred to the working cast
Interproximal margins can be easily damaged during sawing procedure, if clearance is less between proximal margin and adjacent tooth
Male and Female parts are perfectly fitted without any torsion. Male pin is combined very softly with female (sleeves).Zinc and Nickel plated. Each rubber cap is packed individually for convenience.
Dowel Pin improves the accuracy and efficiency of pin-process. Dowel Pin is designed elaborately and has a unique shape in order to prevent distortion during pin modeling process.Available in size medium #2 in gold-colored brass or silver-colored nickle-plated.
With Plastic SleeveNickel Plated Zinc
Extended pin head allows for increased stability
Able to compensate for the expansion of anhydrite while hardening
DIES are separated from the cast with the fine saw.
The cut should be made in such a away that it should taper towards each other slightly from occlusal to gingival
Gently tap on the end of the dowel with an instrument handle to loosen the die
The head of the dowel extends 1-2 mm in to the impression of the prepared tooth.
Depressions are made around 2 mm deep on either side of the dowels in the two large segements of the cast that will carry the unprepared teeth.
Thin coat of petrolatum is applied to the stone and the dowels.
Boxing wax is placed around the impression with the tip of the dowels sticking through.
The completed cast is sawed
A segement is removed by pressing on the exposed tip of its curved dowel.
Before using check for space in articulator
Snap apart plastic tray with internal orienting grooves and notches to reassemble the working cast and die.x
Before using check for space in articulator
Snap apart plastic tray with internal orienting grooves and notches to reassemble the working cast and die.x
Before using check for space in articulator
Snap apart plastic tray with internal orienting grooves and notches to reassemble the working cast and die.x
With a single-pour technique, the impression is formed in the usual way, and the Di-Lok tray is filled. Then the tray is inserted into the impression while the stone is still wet.
After the die stone has fully set, the locking and curved arms of the tray are removed. The cast can then be removed by tapping the anterior pad of the tray base
which, in conjunction with
orienting ribs on the inner surfaces of the tray, will reproduce an accurate relationship of the separate members
The dies are sectioned by sawing three fourths through the stone and are separated
by breaking the remaining stone base.
Unimpeded - Not obstructed or hindered
Reverse drill press is used
20mm of stone beyond the edge of the tray.
Pilot light
Exert firm downward pressure on the cast with thumbs
Shorter pins on lingual side
Longer on buccal side makes the ends of the dowel pins more accessible for easy removal after the casts are mounted.
Machine is checked then working cast is placed on the drill table
oriented until the pilot light beam in the drill unit is directed to the desired point (occlusal surface of the proposed die)
Apply cyanoacrylate cement on the ends of dowel pin and place it into the prepared portion of base of die
Plastic sleeve inserted. Separating media is applied and The cast is then placed in a die base former and the base is poured in dental stone
For cutting die
It also has a tendency to break off from the edentulous area at the level of pin.
Fill both accu tray and impression tray with stone.
Align the reference marks of impression with guide points on accu tray.
With help of magnetic indexer mounting is done.
Articulation in conventional manner.
Remove locking arm for easy access.
Section the model.
SOLUTION: 1) VACCUUM MIXED DENTAL STONE
2) Add stone in small increments at one border of impression; allow it to flow throughout impression
Solution: 1) place gnarled portion of pin in middle of preparation; end at or slightly below gingival margin of preparation
2) Ditch die to max depth of 0.5 mm to avoid weakening of die in this area
Solution: 1) initialy pour no more than 5 mm over margin of preparation and slightly over gnarled portion of dowel pin
2) Augment base of die with grooves or depressions to give positive unyielding seat to resist rotation
Solution: 1) taper cuts to make narrow portion adjacent to base of cast
2) Place dowel pin in natural teeth adjacent to preparations to make teeth removable and alow for removal of preparation dies
Solution: clean with air pressure, toothbrush, pipe cleaners
Sometimes, an impression is poured improperly. It may contain bubbles. The stone used for the die material may be too thick or too thin. The impression or the poured dies may be misplaced or lost. The result of each of these problems is a need to remake the dies. When this need arises in the case of an impression made with conventional impression techniques, the impression must be repoured. The digital impression concept allows retention of the digital information in appropriate computer storage as soon as it is received. Assuming the digital information is backed up adequately, the problems created by poorly poured, lost or misplaced impressions are eliminated by the digital impression concept, thus potentially improving impressions.
Sometimes, an impression is poured improperly. It may contain bubbles. The stone used for the die material may be too thick or too thin. The impression or the poured dies may be misplaced or lost. The result of each of these problems is a need to remake the dies. When this need arises in the case of an impression made with conventional impression techniques, the impression must be repoured. The digital impression concept allows retention of the digital information in appropriate computer storage as soon as it is received. Assuming the digital information is backed up adequately, the problems created by poorly poured, lost or misplaced impressions are eliminated by the digital impression concept, thus potentially improving impressions.
Chairside Economical Restoration of Esthetic Ceramics
The segment was isolated with a rubber dam, and titanium-dioxide powder was applied to the area as an optical imaging agent The use of titanium dioxide ensures uniform scattering of the light when taking an optical impression. Without the contrasting agent, some of the light is absorbed into the enamel and some light is scattered by the glare of the field.
Light pressure of about 20 gms
Elevated by 200 micro meter
Model is tightly screwd on a special base. The user then began the scanning process which is fully automatic with this mechanical scanner and it last about 3 min. and margin is marked and coping is generated in the computer and data is then transferred to the procera production system
A good impression and an accurate die are the first step towards the fabrication of an accurate restoration whether its inlay, onlay or crown.
Proper selection of the die material and its manipulation are paramount to achieve accuracy in the die.
So, a wise choice of material, combined with proper handling and meticulous approach to the details of each step of fabrication will bring us that much closer to perfection