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Working cast &die shams new1

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Working cast &die shams new1

  1. 1. by Shams Waaz Amgad Ali Lecturer of Fixed Prosthodontics Minia University
  2. 2. DEFINITION
  3. 3. It is the positive reproduction of the prepared teeth, ridge areas and other parts of the dental arch.
  4. 4. - It is the positive reproduction of the prepared tooth on which the wax pattern is made and are finished. - It consists of a suitable hard substance of sufficient accuracy.
  5. 5. The cast can not contain more information than the impression from which it was made. IS IT TRUE???
  6. 6. REQUIRMENTS
  7. 7.  Reproduction of both prepared teeth and edentulous area ( for pontic fabrication)  Reproduction of occlusal surfaces of un prepared teeth to allow proper articulation with opposing teeth  Reproduction of the adjacent and contra lateral teeth to allow proper alignment and contouring
  8. 8.  Reproduction of the gingival tissue accurately  Free from bubbles specially at the finish line of the prepared tooth  Free from distortion  The cast must be trimmed to insure access for carving wax pattern margins
  9. 9. 1. It must reproduce the prepared tooth exactly. 2. All surfaces must be accurately duplicated. 3. No bubbles or voids especially along Finish line. 4. The remaining unprepared tooth structure immediately cervical to the finish line should be easily discernible on the die, ideally with 0.5 to1 mm visible
  10. 10. Allow 0.5-1mm of unprepared surfaces apical to the Finish line WHY ????????? To identify the contour of the tooth & allow margin adaptation
  11. 11.  High dimensional accuracy and stability on setting  High strength and abrasion resistance to withstand handling without fracture  Contrast color with wax to facilitate defining preparation margin  Good wetting with wax
  12. 12.  Compatible with the separating agent, so that the wax pattern does not stick.  Compatible with the impression material used.  Ease of sectionable & trim.  Ease of manipulation and time saving
  13. 13. How select the die material???? .
  14. 14. The type of impression material determines the choice of the die or cast material . Hydrocolloid impression are effective only with gypsum products Compound impression are usable with stone, amalgam, electro-deposition of metal Polysulfide impression are usable with
  15. 15. DIE SYSTEMS
  16. 16. DIE SYSTEMS
  17. 17. I-SINGLE DIE
  18. 18.  Impression for a single full metal crown preparation.  Used with either impression compound or rubber base impression material.  Copper band are supplied in different sizes and diameter to fit for anterior, premolars and molars.
  19. 19.  Inexpensive  Compatible with most impression materials  Reproduce fine details in the impression.  Easy to use Advantages
  20. 20. 1) Poor resistance to abrasion Disadvantage Overcome by: Gypsum hardeners (colloidal silica) Application of low viscosity resin (Cyanoacrylates). Resin-strengthed gypsum product e.g Resin Rock  Gum arabic and calcium hydroxide mixture.
  21. 21. DIVESTMENT DIE Gypsum bonded investment+ colloidal silica The wax pattern is constructed on the die & not removed during setting the investment. BUT , Used for gold alloys only ??????
  22. 22. To Control setting expansion: Avoid: 1. Decrease water/ powder. 2. Increasing mixing time. 3. Immersion of gypsum products in water during the setting process. ????? 4. Increasing temperature of mixing water( from 23- 30°). 2)Setting expansion: Linear expansion occur during setting (0.06-0.9%). Follow the manufacturer’s instruction for the current water/powder ratio and manipulation.
  23. 23.  High abrasion resistance & compressive st.  Compatible with rubber base ??& compound  Very long setting time Resin are used as a die material to overcome the low strength and abrasion resistance of die stone e.g. Autopolymerizing resin,Epoxy Resin & Polyurethane Advantages
  24. 24.  Expensive  High polymerization shrinkage (under sized die )  Incompatible with poly-sulfides & hydrocolloids. WHY????? Disadvantages
  25. 25. Used only with copper bands with impression compound Very hard die Long setting time Dimensionally unstable(delayed expansion)
  26. 26.  It is a special type of ceramic supplied as powder and liquid (Mainly quartz silica )  Special for construction of all-ceramic restorations  It allows porcelain to be built direct on the die?????  Can withstand very high temperatures without any distortion  Expensive
  27. 27. Flexible die materials is similar to heavy bodied silicone or polyether impression materials Indications: •Provisional restorations. •Indirect composite resin inlays or onlays. Advantages: more rapid setting ease of removal of the provisional or inlay
  28. 28. Electrolytic deposition of a coat of pure metal on the impression
  29. 29.  Impression compound  Silicon rubber base Metalizing stage  The impression compound metalized by painting graphite to conduct electricity.  The impression rubber base metalized by copper powder.
  30. 30.  Impression connected to cathode (-ve)
  31. 31.  Impression submerged into tank solution( electrolyte)  Copper plate at anode must be 8 inches away from impression.  20 mA current  12 hours plating  After complete plating ,pouring the impression with stone or resin.
  32. 32.  The impression material is rubber base.  Washing and drying impression  Metalizing the impression (silver powder).
  33. 33.  Impression submerged into tank solution( electrolyte)  Bar of silver as anode (+ve),  placed 4 inches away from impression  10 mA current  12 hours plating  After complete plating ,pouring the impression with stone
  34. 34.  . The main disadvantage of silver plating is that a cyanide solution is used & this needs special precautions because of its extreme toxicity  This technique cannot be performed with all impression materials.  Silicone impression materials have low surface energy, are difficult to be electroplated.
  35. 35.  Polyether impressions, because of their hydrophilic nature imbibe water & become distorted.  Polysulfide polymers can be silver plated, but it is much more difficult to copper plate them.
  36. 36. Silver plated die Copper plated die Impression material Rubber base • Impression compound • Silicon rubber base Impression is metalized by Applying metalizing powder( which increase the affinity of impression toward silver) e.g. •Bronze •Graphite •Silver 1. The impression compound metalized by painting graphite. 2. The impression rubber base metalized by copper powder. Current intensity 10 (mA) for band impression Or 60 mA for tray impression 20(mA)* Distance between impression and plate 4 inch 8inch** Time of plating 12 hours 12 hours
  37. 37. Thank you
  38. 38. by Shams Waaz Amgad Ali Lecturer of Fixed Prosthodontics Minia University
  39. 39. DIE SYSTEMS
  40. 40. WORKING CAST WITH SEPARATE DIES (Multiple Pour Technique) (Solid cast with individual die)
  41. 41.  The impression is poured twice or triple:  Full arch cast for proximal contact and occlusion.  Sectional cast (Separate die) for wax coping and margins.
  42. 42. Advantages:  Ease of fabrication Keep the relationship between abutments fixed and immovable The gingival tissues are intact, so we can easily obtain harmonious contour of the wax pattern.
  43. 43. Disadvantages:  Difficult to transfer fragile wax patterns from cast to die (distortion of internal adaptation ) The second pour of the impression may be different (slightly larger) than the first, (seating of the wax pattern may be problematic). Used with elastomeric impression material only
  44. 44. WORKING CAST WITH REMOVABLE DIES
  45. 45. Eliminates discrepancies between a separate die and working cast that may be caused by impression distortion or deterioration between pours, or by a cast and die made from separate impressions that are not identical.
  46. 46. Impression is poured to get a stone cast,  Trimming of the base is performed and lubricated ,  another color stone is poured in wax box then the cast is inserted into it to a depth of 1.5cm(plaster index ). To prevent rocking ,two vertical cuts are then done adjacent to the prepared tooth extending 3mm shorter than the base Using the finger pressure at either end of the cut will separate the dies.
  47. 47.  It is a non anatomic cover which fits to a single die, its advantage is a single die can be used as a removable die. A coping is constructed and transferred to the patient mouth and the impression is taken and removed including the coping. The single die is placed in its position in the impression with the die on it. After lubrication of the impression and the die, box it and a stone cast is poured with the die in it. The single die can then be removed from the cast to produce a removable die.
  48. 48. Single tapered Pin Single curved Pin Doubled Pins Separated cemented Pins Performed tray
  49. 49.  It is positioned over each prepared tooth in the impression.  Dowels are parallel to the long axis of the tooth  Not impinge on the margins.  Flat from one side ???? to prevent rotation.
  50. 50. Bobby pins used for positioning the dowel pins. A dowel is placed between the arms of the bobby pins.
  51. 51.  Bobby pin is positioned BL across the impression.  Dowel pin must not touch the impression.
  52. 52. The first pour of stone should completely cover the dowel head but not on the shaft ??? ( to allow dowel stability)
  53. 53. Paper clips are put into the stone before it sets to provide retention for the base which will be placed later, then straight and bobby pins are removed
  54. 54. Place wax around the tips of the dowels to protect them from the plaster contamination
  55. 55. Two vertical cuts adjacent to the abutments and to the depth of the 2nd stone pour
  56. 56. Parallel saw cuts or converging towards the base Avoid damaging margin or proximal contact
  57. 57. What happens if saw cuts are made diverging towards the base of the cast ?????
  58. 58. Curved dowel pin The tail of the dowel pins protrudes from the facial surface of the cast for convenience of accessibility while the cast is mounted
  59. 59. A snap-apart plastic tray with internal orienting grooves and notches also can be used to reassemble the working cast and die
  60. 60. Pour the full arch impression with die stone, restricted to U- shaped arch (with no stone on the center)
  61. 61. Mix another color of extra hard stone, put it into Di lock tray then seat the cast (above the cervical line)
  62. 62. After stone hardening, remove excess stone and disassemble the tray
  63. 63. By using a saw blade, cut between the prepared tooth and the adjacent one till approximately ¾ the way of the stone base
  64. 64. Reassemble the dies & other parts of the cast in the tray
  65. 65. The Pindex system is a reverse drill press is used to create a master cast with dies that can be removed and replaced repeatedly with great precision The impression is poured without positioning and attaching dowel pins. The machine accurately drills parallel holes from the underside of trimmed cast.
  66. 66.  Pour the impression with correct w/p ratio of extra hard stone
  67. 67. Base of cast to gingival crest 15-20 mm . Flat, smooth and parallel to the occlusal plane
  68. 68. Direct the light indicator to be centralized over the prepared teeth.
  69. 69. Drill from the other side (toward the base) with drill a hole in the base in the center of the die
  70. 70. •Repeat drilling for each prepared tooth. (all holes will be parallel to each others).
  71. 71. Pins (long & short ) their sleeves A dowel pin is attached to hole using cyano- acrylate cement
  72. 72. •Long pin toward facial •Short pin toward lingual (Glue first for better access)
  73. 73. Apply of petroleum( separating media) WHY???? to allow easy separation
  74. 74. Box and seal cast
  75. 75. Pour second base with yellow stone
  76. 76. •Saw mesial and distal to each removable die.
  77. 77. Parallel saw cuts or converging towards the base Avoid damaging margin or proximal contact
  78. 78.  It is a model consists of : 1-Underside base plate having an alignment fixture for impression 2-A top clear plate which having another fixture opposing to those on the bottom base plate. Attach the dowel pins to a clear plate so, that when the clear plate is positioned over the impression , the dowels are suspended in their selected locations
  79. 79. Underside base plate having an alignment fixture for impression
  80. 80. Mark the dowel pin locations in a clear plate
  81. 81. Drilling holes for dowel pins as marked
  82. 82. Inserting dowel pins in base plate (no adhesive )
  83. 83. Pouring the impression &put stone around pins
  84. 84. Replace the alignment fixture over poured impression
  85. 85. Remove the set cast from the base plate by gentle tapping
  86. 86. Sectioning (sawing)the die
  87. 87. Working cast with DVA Model system
  88. 88.  Similar to DVA but instead of visual determination of dowel pin position. A drilling device supplied with a pointer is used to locate the pin position in an attaching plate and drilling a hole in it
  89. 89. ZEISER MODEL SYSTEM
  90. 90. Place the impression in base plate
  91. 91. Determine the locations on pin holes
  92. 92. Insert the pins in the base
  93. 93. Pour the impression
  94. 94. Invert the base with pins over the impression
  95. 95. Working cast after sectioning
  96. 96. DIE TRIMMING & DITCHING
  97. 97.  Remove most of excess stone with #7 lab carbide bur with protective eyewear  Fine trimming with scalpel or cleoid-discoid carver  Margin should be sharp and distinct for access, but it should not be undermined  0.5-1mm uncut tooth beyond finish line should be maintained to provide proper contours in wax
  98. 98. A sharp scalpel is used to trim to final contour, working away from the margin.
  99. 99. Die ditching
  100. 100. Axial contour affected by die trimming & ditching
  101. 101.  The original contour of cervical tooth structure should be preserved.  Over trimming results in an over contoured restoration
  102. 102. DIE PREPARATIONDIE PREPARATION
  103. 103.  Mark the margin with red pencil, not a graphite, traces of the graphite (an antiflux) can prevent complete casting of the margins.  1. Apply die hardener Allow to set for 5 minutes  2. Apply die spacer(cement spacer) 20-40 micron thickness allows space for cement 1 mm short of finish line WHY????? for optimum marginal adaptation
  104. 104. Die spacer ( relief application)
  105. 105. Thank you

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