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Die materials and Die system - Dental

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Die materials and die systems in prosthodontics - Dental

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Die materials and Die system - Dental

  1. 1. Dr. Dwij Kothari Darshan Dental College & Hospital
  2. 2. Definition Basic properties of die materials Materials used for making dies • Gypsum products • Die stone • Electroformed dies • Epoxy resins • Polyurethane CONTENTS
  3. 3. • Silicophosphate cement • Amalgam • Metal sprayed dies • Refractory die materials • Flexible die materials Compatibility with impression materials Comparisons of the various die materials
  4. 4. Cast & die systems • Working cast with removable die o Straight dowel and Curved dowel pin o Di – Lok tray o Pindex system o Accutrak system • Solid cast with individual die o DVA model system o Zeiser model system
  5. 5.  Preparation of the die for wax patterns  Review of literature  Summary and conclusion  References
  6. 6. introduction An accurate working cast with removable dies is essential to make a well fitting restoration. Detailed reproduction of die materials for fixed prostheses affects the accuracy of working casts and is related to the compatibility between the die and impression materials.
  7. 7. A working cast is the replica of the prepared teeth, ridge areas and other parts of the dental arch.
  8. 8. DEFINATION Die :- It is the positive reproduction of the form of the prepared tooth in any suitable substance. (GPT-8) Cast :- A life-size likeness of some desired form. It is formed within or is a material poured into a matrix or impression of the desired form (GPT-8)
  9. 9. Dowel pin:- A metal pin used in stone casts to remove die sections and replace them accurately in the original position (GPT-8) Die spacer An agent applied to a die to provide space for the luting agent in the finished casting (GPT-8)
  10. 10. MATERIALS USED FOR MAKING DIES IN FIXED PARTIAL PROSTHESIS 1. Gypsum products- Type IV Dental Stone Type V Dental stone 2. Die stone-Investment combination 3. Electroformed dies- Silver plated Copper plated 4. Epoxy resins 5. Polyurethane
  11. 11. Alternative die materials 6. Silicophosphate cement 7. Amalgam 8. Metal sprayed dies 9. Flexible die materials 10.Refractory die materials
  12. 12. BASIC REQUIREMENTS OF DIE MATERIALS They should accurately reproduce all fine details in the impression. It should be reasonably easy to use. They should be dimensionally stable. Setting expansion, contraction and dimensional variation in response to setting or change in temperature should be minimal.
  13. 13. The die should have a smooth surface that is sufficiently strong to withstand the abrasion of the surface They should be compatible with impression materials and there should be no interaction between the surface of the impression and cast or die.
  14. 14. Toughness to resist breakage during fabrication or burnishing of fine edges. Colour of the die should be in contrast to the colour of wax. This helps to facilitate the manipulative procedures that will be carried out.
  15. 15. GYPSUM PRODUCTS It is a mineral mined in various parts of the world chemically the gypsum produced for dental applications is pure calcium sulfate dihydrate [CaSO4.2H2O].
  16. 16. 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.
  17. 17. CaSO4 • 2H2O CaSO4 •½H2O +1½H2O (Gypsum) (calcium sulphate hemihydrate) 110-130 Degree C MANUFACTURING PROCESS Calcination reaction
  18. 18. Gypsum Heated for partial dehydration Open air Autoclave Beta hemihydrate (type I and II ) Alpha hemihydrate (type III, IV, V)
  19. 19. Gypsum is ground and subjected to temperature of 110o to 120oC to drive off the water of crystallisation
  20. 20. Gypsum 110-130 degree C In autoclave Boil with 30% CaCl2 or MgCl2 Or 0.5 - 1% sodium succinate Alfa hemihydrate calcium sulfate dihydrate
  21. 21. Setting reaction results from the hydration of calcium sulfate hemihydrate: CaSO4 • ½H2O +1½H2O CaSO4 • 2H2O + heat (3900 cal/gm)
  22. 22. Properties Type IV Type V Water powder ratio 0.22-0.24 0.18-0.22 Setting expansion 0.1% 0.1 to 0.3% Compressive strength 5000psi 7000psi
  23. 23. Advantage of gypsum as die material Compatibility with all impression materials Easy to use Dimensionally stable Inexpensive
  24. 24. Disadvantage of gypsum dies Susceptibility to abrasion Brittle  prone to fracture
  25. 25. Methods to increase abrasive resistance Substitution of colloidal silica for water. Treat surface with resin (epoxy, acrylic, styrene or cyanoacrylate) Impregnating acrylic resin into stone die. (compressive strength-7,000 psi)
  26. 26.  Colloidal silica: It increases resistance to surface abrasion but there is little increase in setting expansion, which is minor.
  27. 27. Low viscosity resins i.e. cynoacrylate, which is used to impregnate the die surface, care is taken while applying it so as to produce uniform thickness.
  28. 28. In order to improve the properties of dental stone: 1. Gum arabic. 2. Calcium hydroxide mixture. 3. Resin strengthened gypsum products such as Resin Rock with high strength and low expansion (particularly for implant casts). 4. Incorporation of wetting agents such as lignosulphonates  reduce water requirement of a stone  harder, stronger, dense set stone
  29. 29. CAD Stone is Type 4 die stone formulated especially for use with CAD/CAM systems. It has high compressive strength, low expansion, and an extended working time, enabling the pouring of multiple impressions.
  30. 30. • PRIMA- ROCK has the highest compressive strength (8,000 psi) of any Whip Mix die material.
  31. 31. Compatible with all types of impression materials. Its high expansion makes it especially suited for polyvinyl or polyether impression materials. Facilitates multiple pours
  32. 32. DIE STONE INVESTMENTCOMBINATION Commercial Gypsum Bonded Materials:- 1. The divestment is mixed with colloidal silica liquid. 2. Die is made & wax pattern is constructed on it. 3. This entire unit is invested in mixture of divestment & water, thereby eliminating the possibility of distortion of pattern on removal from the die.
  33. 33. 4. When heated to 677ºC, - Setting expansion – 0.9% - Thermal expansion – 0.6%. 5. Not recommended for high fusing alloys. 6. Highly accurate technique for conventional gold alloys especially intracoronal preparations.
  34. 34. AMALGAM DIES 1. They are made by packing amalgam into impression made of impression compound. 2. Dies made of amalgam exhibit superior strength, resistance to abrasion & reproduce fine details & sharp margins.
  35. 35. Disadvantages: Can only be packed into a rigid impression . Long time to reach a maximum hardness. High thermal conductivity hence can cool a wax pattern rapidly which can lead to distortion of the pattern.  This can be overcome by warming the die, a separating agent is needed as with stone dies.
  36. 36. SILICOPHOSPHATE CEMENT • The powder is a mixture of silicate powder & zinc oxide & liquid contains phosphoric acid. Advantages:- Strength & surface hardness superior to those of die stone.
  37. 37. Disadvantages:- 1. Material contracts during setting & may be dimensionally inaccurate. 2. Loss of water on standing since viscosity is relatively high. 3. Presence of surface voids can occur.
  38. 38. . Resins Self curing acrylic - epoxy resins, polyesters. Epoxy resins : are used as die materials to overcome the low strength and abrasion resistance of die stones.
  39. 39. The fast setting epoxy hardens rapidly so that dies can be waxed up in half an hour after injecting into the impression.
  40. 40. Properties Working time – 15 min Setting time _ 1-12 hrs Shrinkage _ 0.03%-0.3% Compressive strength – 9500-14200psi Hardness _ 83RHN
  41. 41. Disadvantages 1. Cannot be used with water containing agar and alginate impression material. 2. Shrinkage on polymerization. 3. Less dimensional stability. 4. Expensive. 5. Prone to trap air in preparation
  42. 42. Philip duke, Steven Haug and Carle Andres exhibited several physical properties that may be superior from a clinical point of view. •The epoxy resin exhibited much better detail reproduction, abrasion resistance, and transverse strength than the gypsum materials. •However, its setting shrinkage compared with the expansion observed with gypsum die materials may require modifications in technique to obtain castings that will be well adapted to the tooth preparation. Philip Duke, B.K eith Moore, Steven P. Haug and Carle J. Andres Study of the physical properties of type 4 gypsum, resin-containing, and epoxy die material J Prosthet Dent 2000;83:466-73
  43. 43. Metal sprayeddies Bismuth alloy with fusing point of 136ºF is melted by placing at constant temperature held at 145ºF. Die is poured & solidify at 30 pounds of pressure.
  44. 44. Advantages :  A metal coated die can be obtained rapidly from elastomeric impression materials. Disadvantages :  Alloy is soft, care is needed to prevent abrasion of the die.
  45. 45. Electro deposition of metals:- Can produce detailed reproduction up to 30µm. Have moderately high strength, adequate hardness & excellent abrasion resistance. Basic system consists of:- - An electrolyte solution - A source of direct current. - An anode – pure copper - pure silver
  46. 46. “Metalizing”:- The surface of the impression is coated with a conductor of electricity such as graphite, copper powder or silver before it is attached to the cathode lead wire. COPPER PLATING OR COPPER FORMED DIES : General technique: Electrolyteacid solution of CuSO4+organic constituents Coated impression cathode of a plating bath With an anode of copper. Surface is rendered conductive particles of copper or graphite
  47. 47. Dental stone is then cast into plated impression: when stone has set, the metal covered die can be removed from the impression. A current is passed (5-50mamp/cm2 of cathode is applied for 10-12 hrs)
  48. 48. SILVER FORMED DIES : (SILVER PLATING) For silver plating - Polysulfides & Silicone impressions are used.  Cleaning & drying the impression. Metalize the area to be plated with a fine silver powder by burnishing it with a sable brush. - Various metalizing agents are:- - Bronzing powder. - Aqueous suspension of silver powder. - Powdered graphite.
  49. 49. Insert cathode wire in the border of impression in the metalized area Fill preparations & the teeth with electrolytic solution Completely submerge the impression in plating solution. The silver anode immersed in the solution should be at least equal in size to the area of the surface to be plated.
  50. 50. • Proceed plating initially at approx. 5mA per tooth for 1hr and check for even deposition of metal and make certain there are no voids. • Resubmerge the impression in plating solution & plate it for approx. 12hrs. at 10mA per tooth. • Wash and dry impression and use dental stone.
  51. 51. Problems in Electroplating : 1. Silver cyanide solution is extremely dangerous, it contacts acid & produces fumes of extremely toxic hydrocyanic acid. 2. These dies are not significantly more or less accurate than stone dies. 3. The possibility of continued polymerization & distortion of impression during electroplating may lead to a clinically significant dimensional change in the impression.
  52. 52. 4. Friable metal deposit if current set  too high. 5. Silicone difficult to electroplate, because of low surface energy. 6. Polyether cannot be plated accurately, since it imbibes water. 7. Polysulfide can be silver plated but difficult to copper plate.
  53. 53. Flexible Die Materials:- - Similar to heavy bodied silicone or polyether impression material. Use:- - To make provisional restoration. - Indirect composite resin inlays or onlays chairside - Maryland bridges. Advantage:- - More rapid setting – 10min. - Ease of removal of provisional restoration.
  54. 54. Douglass Smith, Arun Nayyar, David L. Koth - Fabrication of removable dies using cemented dowel pins J Prosthet Dent: 1992:68:372-4 While fabricating of removable dies - Douglass used polyvinyl as cast, that may be flexed to remove the polymerized resin from the undercuts on adjacent teeth or from the die.
  55. 55. Procedure: Procedure involves :- • Make a preoperative mold of the tooth/teeth to be prepared, including the adjacent teeth. This can be either a custom thermoplastic form made from a diagnostic cast or an elastomeric impression made directly in the patient’s mouth.
  56. 56. Irreversible hydrocolloid impression Fill with the fast setting, medium viscosity polyvinyl impression material Place the polyvinyl cast into the pre operative mold Custom made thermoplastic crown form is filled with auto polymerizing resin and is seated on the flexible cast.
  57. 57. The polyvinyl cast is flexed to remove tooth colored resin from the undercuts. Interim restoration on the prepared tooth
  58. 58. A low viscosity polyvinyl siloxane duplicating material is used to reproduce dies Adapt a strip of putty around the prepared teeth on working cast and dies to limit the flow of mold material. Refractory Dies:- These are made for preparation of all ceramic restorations. Advantages – Excellent marginal adaptation
  59. 59. • To avoid air entrapment, fill the putty reservoir by pouring the mix. • The duplication material should be at least 3.00mm thick and it should extend 3 mm beyond incisal edges of teeth to provide adequate support refractory material. • The duplicating material is allowed to set for about 30 minutes.
  60. 60. • By applying pressure on base of tray, master cast is loosened with duplicating material intact. • The master dies removed from cast and duplicating material.
  61. 61. • The refractory material is poured and vibrated in the area of missing dies. • Allow the refractory dies set for about 1-2 hours.
  62. 62. Technical considerations of refractory die material • Recommended powder liquid ratio must be followed since it may cause uncontrolled expansion or, shrinkage during setting and possibly a weakened die. • Wax burnout furnace – up to 700°C for degassing to eliminate sulfur and ammonia gases and then ceramic furnace – up to 1080°C in vacuum.
  63. 63. • Cooled down at room temperature • Application of die sealant i.e. Application of 2 thin wash of half glaze, half dentin porcelain to prevent porous die material to absorb water from porcelain & fire.
  64. 64. Compatibility with impression materials : Dental stone -Impression compound -Zinc oxide eugenol -Alginate -Impression plaster when used with separator -Rubber base material Electroplated Cu - Impression compound Electroplated silver - Polysulphide - Rubber base material Epoxy Resin - Rubber base material
  65. 65. Comparisons: 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
  66. 66. Materials Advantages Disadvantage Use Precaution ADA TYPE 4 stone • Dimensional accuracy • Straight forward technique • Low cost Low abrasion resistance Most situations Accurate proportioning essential ADA TYPE 5 stone •Straight forward technique • Low cost •Improved strength than type4 Increased expansion Most situations Accurate proportioning essential
  67. 67. Materials Advantages Disadvantage Use Precaution Electroplating High strength Good abrasion resistance •Time consuming Complete ceramic crowns •Silver uses toxic cyanide •Incompatible with many impression materials Epoxy resin •High strength •Good abrasion resistance •Polymerization shrinkage • Time consuming complex procedure Complete ceramic crowns Not compatible with polysulfide and hydrocolloid
  68. 68. Die Hardener Materials applied on the surface of die to increase the surface hardness. Should have low viscosity Commonly used materials as die hardeners:  Cyanoacrylate resins (Eg: Premabond)  Acrylic resin lacquer (Eg: Die Prep die hardener)
  69. 69. 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. Quickly blown off and dried from above the margin toward the cervical area. or Blot with tissue
  70. 70. Optimal Thickness  2-3 micro m, but if not properly manipulated10 micro m (JPD 1991;65;713) Air blowing or blotting the excess with tissue, decreases the film thickness of die hardener to 1 micro m Hisao F Effectiveness of hardening films on die stones. JPD 1980;44;57.
  71. 71. Lacy AM et al (JPD1980:44:356) concluded that Cyanoacrylate resins and resinous die hardeners effectively improved the hardness and abrasion resistance of stone dies. 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 build up was qualitatively related to the viscosity of the resin.
  72. 72. 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 .
  73. 73. Paul E. Harris et al (JPD 2004;92;35) compared the surface micro-hardness of type IV and type V gypsum materials with and without surface die hardeners (Premabond 910 & Clear coat) . They concluded that die hardeners evaluated did not increase the surface hardness of gypsum materials, but they actually decreased the surface hardness. Paul E. Harris Alteration of surface hardness with die hardener. JPD 2004:92;35.
  74. 74. Die Spacer :- An agent applied to a die to provide space for the luting agent in the finished casting. Types of die spacers : Resins Paint or liquids Model paint Coloured nail polish Thermoplastic resins dissolved in volatile solvents.
  75. 75.  Optimal thickness  20-40 micro meter (Acc. to rosenstiel 4th edi. Pg 557) 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 m had only moderate influence on retention. Eames et al (JADA 1978;96;432) – optimal thickness - 25 micro meter
  76. 76. Should flow uniformly and smoothly Color should be readily identifiable on the die Thinners are available to decrease the viscosity of die spacer.
  77. 77. Should be applied 0.5-1mm short of margin Brush strokes in one direction Wait for 2 mins before applying next coat
  78. 78. W.G. Campagni at al (JPD 1982;47;606) Did a study on measurement of die spacers used for casting relief and concluded that measurements of thickness of commercial die spacers were not consistent with those reported by the manufacturer.
  79. 79. Tjan et al (JPD 1981;46;399) 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.
  80. 80. Terry D et al (JPD 1982;47;606) concluded that 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.
  81. 81. W.V. Campagni et al (JPD 1986;55;324) concluded that grooves did not disrupt seating when die spacer application was specifically omitted from grooves.
  82. 82. PEEL-AWAY DIE SPACER 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
  83. 83. Die Spacer Pens (Kerr Laboratory) Poly fiber disposable tip.
  84. 84. die lub Die Separator 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.
  85. 85. Die Separator Easy removal of wax pattern without damaging margins. Applied with brush Excess to be removed with tissue paper  Eg: Kleen lube (Kerr) Picosep (Renfert) Dielube wax sep(Dentecon Inc.)
  86. 86. Cast & Die Systems
  87. 87. CONTENTS Die systems  Working cast with separate die  Working cast with removable die Conventional dowel pin system Di-lok Pindex DVA Belle de st. Claire Zeiser Accu-trac system Mono trac
  88. 88. Working cast with separate die Simplest method of fabrication Advantages: Easy to fabricate Keeps relation between abutments fixed Better contours and emergence profile while wax pattern fabrication.
  89. 89. 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 - Different thickness of spacers
  90. 90. Procedure:- Both working cast and sectional die can be obtained by: - Pouring impression twice - Making two impressions
  91. 91. Preparation of separate die Stone added to side of impression in small increments Tray tilted to fill the Impression displacing air as it moves
  92. 92. Add stone in small increments If large amount of stone dropped into preparation or If two sizable masses of stone meet Air trapped voids • Build to height of approx 1 inch
  93. 93. Pour stone to receive working cast Make base Retrieve cast
  94. 94. Trim sectional cast Octagonal in shape Sides parallel or slightly taper towards base Handle 1 inch long
  95. 95. Pear shaped acrylic bur  trimmed apical to finish line Final trimming sharp blade Smoothened
  96. 96. Contour be approximately like root  To facilitate good axial contours in restoration Sharply undercutting  thick gingival areas, improper axial contours
  97. 97. Finish line highlighted with red pencil Not to use black graphite pencil Apply die spacer
  98. 98. Fabrication of FPD Die of each part is left joined to each other by means of common base Edentulous ridge area cut back
  99. 99. Philippe A. et al (IJP 1993:6;533) compared 2 removable die systems (Zeiser system (Girrbach Dental), Pindex (Coltene-Whaledent) and working cast with separate die. They concluded that the Zeiser system was the most accurate of the three systems studied, followed by working cast with separate die.
  100. 100. WORKING CAST WITH REMOVABLE DIE Advantage: Convenient to use 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
  101. 101. 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
  102. 102. Systems using die pins Methods of repositioning die in its working cast Systems using pre formed plastic trays without die pins
  103. 103. Pre pour technique Post pour technique Devices are oriented in the impression before it is poured Attached to the underside of the cast that has already been poured Systems using die pins
  104. 104. Conventional dowel pin systems Dowel pin (GPT 8): a metal pin used in stone casts to remove die sections and replace them accurately in the original position
  105. 105. Straight Curved
  106. 106. Straight dowel pin Flat sided dowel Double straight dowel with common head (Bi pin) Rounded single dowel pin
  107. 107. BI-PIN with case BI-FIXED-pin Doubles straight dowel with fixing wire for accurate positioning in impression
  108. 108. Procedure (Pre pour technique)
  109. 109. Marking to act as guide in placement of pins Positioning of dowel pins A)
  110. 110. Mann paralleling instrument Clamps holding Dowel pins (33)
  111. 111. C) • Disposable anesthetic needles
  112. 112. D) Straight pins with modeling clay E) Matchsticks (JPD 1975;34;467)
  113. 113. F) Bobby pins (1)
  114. 114. Die stone poured into impression filling the impressions of teeth and covering the knurled end of the dowel pin
  115. 115. V- shaped orientation grooves made Separating media-area adjacent to each dowel pin
  116. 116. Small wax ball placed on tip of each dowel Boxing done Base formed
  117. 117. Curved dowel pin Positioning bar Stone poured covering heads of dowel and 1-2mm of body of dowel
  118. 118. Orientation grooves made
  119. 119. Using metal strips (JPD 1996;35;231) Thin metal strips (0.001 gauge) were carefully wedged in the impression
  120. 120. Placement and tapering of matrix band Matrix band kept parallel in case of multiple preparations
  121. 121. 2 mm of band exposed
  122. 122. Post pour techniques Fabrication of removable stone dies using cemented dowel pins (JPD 1979;41;579)
  123. 123. Pour cast- minimum height from border -10 mm Trim borders-U shaped outline  B-L width 15 -20mm Horizontal line - 10mm from lowest portion of edentulous ridge (4-5mm mesial and distal to prepared teeth)
  124. 124. Draw vertical parallel lines to indicate common path of removal of all die segments. Draw broken lines  dividing into half
  125. 125. Orientation grooves
  126. 126. Di lok tray system (Di –Equi Dental products Co)
  127. 127. Snap apart plastic tray with internal orienting grooves and notches to reassemble the working cast and die. Before using check for space in articulator
  128. 128. Cast poured1inch height No stone in lingual area Trim to fit Di lok tray
  129. 129. Horizontal grooves Fill tray ¾ with stone Seat the cast  cervical area of teeth be about 4mm above the edge of tray
  130. 130. Disassemble the tray
  131. 131. Cut till ¾ length
  132. 132. PINDEX SYSTEM (Coltene / Whaledent) Light beam director Drill hole Work table Handle bar Motor housing
  133. 133. Bottom should be flat to ensure that the Pins will be parallel Faciolingual width – 20 mm
  134. 134. Two pins for each die Two for each pontic area One /Two pins in each terminal segment containing unprepared teeth
  135. 135. Round parallel side brass pins (15mm, 10mm) Collar of pin should flush with base of cast to avoid creating an undercut
  136. 136. 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.
  137. 137. Strip of utility wax along ends of long pins Ball of wax on isolated pins on contralateral side Ends of shorter sleeves  place wax
  138. 138. Pinned cast can be removed from base in one piece  sectioning of cast from underside. (limited interdental space possibility of damaging finish line.
  139. 139. DVA System Pre manufactured base system Two tapered round brass pins per die - 7mm
  140. 140. Impression on alignment fixture Secured with putty Marking dowel pin locations On clear plate with twin tip marker
  141. 141. Drill holes for dowel pins Using drilling press Insert dowel pins
  142. 142. Impression is poured and stone is placed around dowel pin Alignment fixture is replaced over poured impression
  143. 143. Set cast is removed from baseplate with gentle tapping Cast is trimmed
  144. 144. Cast is sectioned Definitive cast trimmed with DVA model system
  145. 145. Zeiser model system (Girrbach dental Gmbh, Germany) (14,17)
  146. 146. Impression leveled, blocked out with silicone putty positioned over the base
  147. 147. Pin locations determined Pin holes drilled in base
  148. 148. Pins inserted into base Impression is poured
  149. 149. Base inverted The cast is separated from the impression
  150. 150. Belle de st. claire Round slightly tapered S.S. dowel pins15 mm long Flat surface and plastic indexer positive lock  retention and anti-rotational Feature. Holes pindex system with drill available with the system
  151. 151. Plastic indexers
  152. 152. Accu- Trac Die Precision System - (Coltène Whaledent) (14,17)
  153. 153. Place the impression on the precision base and adjust, so that it is centered and horizontal. Place die stone in the impression and in the base of tray
  154. 154. Open the retaining arms to remove the model
  155. 155. Monotrac Articulation
  156. 156. Vertical single pour base (VSP)
  157. 157. Pour stone Spray silicone spray on VSP Cones. Separator on stone
  158. 158. Trim impression –fit the base molds Pin –act as guide for placement
  159. 159. Remove base mold and impression VSP base removed by tapping
  160. 160. Sectional impression
  161. 161. Dies for CAD CAM systems
  162. 162. CEREC SYSTEM (Sirona Dental System, Germany)
  163. 163. Intraoral camera to take optical impression of the preparation
  164. 164. Preparation covered with opaque powder ( Titanium dioxide )
  165. 165. Image as viewed on monitor Cavity outlines are identified for formation of future restoration
  166. 166. Cerec milling unit
  167. 167. Procera all ceram system (Nobel Biocare)
  168. 168. Scanning of the die Scanner probe with a ball tip Light pressure of about 20 gms Elevated by 200 micro meter
  169. 169. Displayed image
  170. 170. Spacer thickness programmed designing of the restoration done
  171. 171. Soft Tissue Masque
  172. 172. Sawing of model for separation of dies and ditching the die (to reveal preparation margins) removes critical anatomy which would help guide the creation of optimal restoration contours.
  173. 173. 1. No guide left for axial contours Overcontouring tissue impengement and poor accessibility for oral hygiene plaque buildup Inflammation Undercontouring unesthetic opening of interproximal spaces 2. No proper emergence profile
  174. 174. TECHNIQUE
  175. 175. Elastomeric impression of untrimmed cast made Pink polysiloxane material (Gi-mask,Coltene)placed in putty index
  176. 176. Impression with silicone material placed on the working cast Cast with soft tissue mask
  177. 177. REVIEWOF LITERATURE
  178. 178. Gerald T Nomura et al J Prosthet Dent 1980:44:1:45 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
  179. 179. • 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
  180. 180. 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
  181. 181. E. Ricardo Schwedhelm et al J Prosthet Dent 1997;78:554-9 Study evaluated the fracture resistance of 4 die stone materials at different time intervals. Additional silicone impressions were made of a maxillary master cast. Two Type V, one Type IV die stones and one Type IV resin reinforced stone were tested. A total of 80 casts were prepared, separated, and tested on the Instron Universal Testing Machine at 1/2, 1, 12, and 24 hours to measure resistance to fracture.
  182. 182. Significant differences to fracture resistance of the different die stone materials were observed at all time intervals except at 24 hours. Type IV resin gypsum product was the only material that really benefits by waiting 24 hours for the cast to set.
  183. 183. Conclusion: It is recommended to wait at least 12 to 24 hours when separating casts from impressions to avoid casts from fracturing. It is possible that residual moisture in the stone cast may be concentrated near the preparation and may affect the strength of die stone.
  184. 184. Lawrence G. Breault etal J Prosthod 1998;7:13-16 conducted a study were in Substitution of a 5.23% solution of sodium hypochlorite in place of 10% of the gauging water when mixing a Type V stone. Conclusion: resulted in an increased compressive strength and rigidity and a decrease in setting time. There was no change in tensile strength, setting expansion, hardness, or detail reproduction.
  185. 185. Incorporation of sodium hypochlorite in the gauging water may be an effective, convenient, and inexpensive method of disinfecting gypsum casts in the laboratory without adversely effecting physical and mechanical properties. However, there may be a reaction between sodium hypochlorite and base metal alloys.
  186. 186. Alvin G. Wee, C. Cheng and Ryan N. conducted a study to check an accuracy of 3 conceptually different die systems used for implant casts. 3 different die systems tested: double-pour (Pindex), plastic base (DVA), and die tray (KO Tray) They concluded that the use of a double-pour or plastic base die system is recommended when sectioned dies are needed for a multi-implant–retained prosthesis Alvin G. Wee, C. Cheng and Ryan N. Accuracy of 3 conceptually different die systems used for implant casts J Prosthet Dent 2002;87:23-9
  187. 187. Conclusions: 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.
  188. 188. REFRENCES Anusavice K.J.-“Phillips’ Science of Dental materials” 11th edition , 2003 Craig’s R.G., Powers J.M. – “Restorative Dental Materials” 11thedition, 2002 Rosenstiel S.F., Land M.F. – “ Contemporary fixed prosthodontics” 3rd edi. 2001. Rudd K.D., Morrow R.M. – “Dental laboratory procedures” FPD 2nd edi, 1986.
  189. 189. Dr.Sama Sudharshan Reddy-“Evaluation of the effect of die spacing on the retention of complete coverage cast crowns,” 2004 Shillingburg H.T. – “Fundamentals of fixed Prosthodontics.”3rd edition Anna Belsuzarri Olivera and Tetsuo Saito- The Effect of Die spacer on Retention and Fitting of Complete Cast Crowns J Prosthodont 2006;15:243-249.
  190. 190. C, Douglass Smith, Arun Nayyar, David L. Koth-Fabrication of removable dies using cemented dowel pins J Prosthet Dent: 1992:68:372-4 Alvin G. Wee A nsgar C.Cheng, andRyan N. Eskridge-accuracy of 3 conceptually different die systems used for implant casts J Prosthet Dent 2002;87:23-9 Michael A. Mansueto and Rodney D. Phoenix -A Comprehensive Approach to Die Trimming J Prosthod 1994;3:251-255
  191. 191. Gerald T.Nomura, Morris H. Reisbick, jack D. Preston-An investigation of epoxy resin dies J Prosthet Dent 1980:44:1:45 Lawrence G. Breault, James R. Paul ,Steven 0. Hondrum, and hren C. Christensen - Die Stone Disinfection: Incorporation of Sodium Hypochlorite J Prosthod 1998;7:13-16 Philip Duke, B.K eith Moore, Steven P. Haug and Carle J. Andres Study of the physical properties of type 4 gypsum, resin- containing, and epoxy die material J Prosthet Dent 2000;83:466- 73
  192. 192. Dr. Alex Touchstone , Dr. Randy J. Phillips Simplifying CAD/CAM Dentistry Chair side CAD/CAM designing and milling are not as complex as they may seem Dental Products Report (Supplement 1) November 2005 Juan Glen Serrano, Xavier Lepe, John D. Townsend, Glen H. Johnson, Stephen Thielke-An accuracy evaluation of four removable die systems-J Prosthet Dent 1998;80:575-86. E. Ricardo Schwedhelm and Xavier Lepe- Fracture strength of Type IV and Type V die stone as a function of time J ProsthetDent 1997;78:554-9.)
  193. 193. Alvin G. Wee, C. Cheng and Ryan N. Accuracy of 3 conceptually different die systems used for implant casts J Prosthet Dent 2002;87:23-9

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