Die materials and die systems

Die materials and die systems

1. Die materials & Die systems

2. INTRODUCTION Fabrication of restorations of Fixed Prosthodontics require indirect techniques , in which the fabrication of the restoration is done outside the mouth. For this ,an accurate duplication of prepared teeth and maintenance of their relationship to one another is important .

3. DEFINITION Die may be defined as the positive reproduction of the form of a prepared tooth in any suitable substance. For the restoration to fit accurately in the mouth , the die should be accurate .

4. DOWEL PIN – A metal pin used in stone casts to remove die sections and replace them accurately in the original position . DIE SPACER –An agent applied to a die to provide space for the luting agent in the finished casting.

5. IDEAL REQUIREMENTS Dimensional accuracy . High abrasion resistance . Ability to produce fine details . Compatibility with all impression materials . - Toughness to resist breakage .

6. Colour contrast with wax ,porcelain , Ease of manipulation and rapid fabrication . Non injurious to touch and inhalation Economical .

7. CLASSIFICATION I . ACCORDING TO THE TYPE OF MATERIAL : Gypsum Products : Type IV Dental Stone . Type V Dental stone ,high strength , high expansion Type V Dental stone with ligho sulphonates .

8. b) Metal and metal coated dies : Electroformed dies . Metal sprayed dies . Silver amalgam dies . c) Resin or polymer dies : Metal or inorganic filled resins . Epoxy resins .

9. Cements : Silicophosphates . Polyacrylic acid bonded cement . Refractory Materials : Divestments . Investments (for RPD frameworks ) . f) Flexible die materials .

10. II . Based on the design : a) Working cast with seperate die system . b) Working cast with removable die system . c) Accutrac system .

11. GYPSUM DIE MATERIALS Most commonly used . A D A specification No : 25 . Type IV & V are used .

12. Advantages Easy to use . Relatively inexpensive . Easy manipulation . Good working time . Minimum shrinkage . Compatible with all impression materials . Good colour contrast .

13. Disadvantages Mechanical properties not ideal . Brittle . Less abrasion resistant .

14. Modifications To overcome the abrasion resistance Add colloidal silica . Impregnate the surface with a low viscosity resin such as cyanoacrylate . RESIN ROCK * (WHIP MIX ) .

15. ELECTROPLATED DIES It is the deposition of a coat of a metal . Pure silver or copper is used . ELECTROFORMING : It is process by which a thin coating of metal is deposited on the impression , after which a gypsum cast is poured into the impression .

16. PLATING CAN BE DONE : Individual tooth preparation . Full arch impression . Compound impression .( copper plated .) Polysulfide . (silver plated .) Silicone impression . .

17. ) Plating the impression Electrolyte placed into deeper parts of impression

18. C) pouring cast into plated impression

19. Silver plated die . Remaining silver fash between teeth severed with sharp scalpel .

20. ADVANTAGES : Dimensional accuracy . Hard & abrasion resistant . Economical . Does not absorb oil or water . Imparts smooth surface to wax pattern . Prevents cuspal wear

21. DISADVANTAGES Difficult to trim . Silver bath – health hazard . Colour contrast not good . Not compatible with all impression materials . Adaptation of wax not as good as stone

22. RESINS They are used to overcome low strength and abrasion resistance of stone . Epoxy resins are commonly used . Polyurethane may also be used . The are most effective with rubber based impression materials . (Silicones & Polyether )

23. EPOXY RESIN Supplied as resin paste and liquid activator (amine) Trade names : Epoxydent , Oxydental products Epoxy die material, Dentsply Pri -Die, Jelenko Diemmet

24. ADVANTAGES Tougher . Dimensionally stable . More abrasion resistant . Detail production better . Can be used at room temp .

25. DISADVANTAGES Shrinkage during polymerisation . Viscous ,does not flow readily . Setting may take upto 24 hrs . Expensive . Tight fitting prostheses . Not compatible with hydrocolloid & Polysulfide .

26. FLEXIBLE DIE MATERIALS They are similar to heavy bodied silicone or polyether impression materials . Advantages over gypsum : More rapid setting . Ease of removal of interim restoration .

27. Flexible die material is Injected into the impression . Putty applied to force the impression Material into the impression Set material . Die removed .

28. Provisional Restoration fabricated using composite resin Resin cured

29. Model sectioned to allow proximal access for contouring Restoration removed from flexible die

30. Advantage: Less time required Overcomes problems associated with making interim restoration on arches that have significant undercuts Disadvantage: Expensive Separator  surface details poor

31. ALTERNATIVE DIE MATERIALS A ) Silicophosphate cements : Similar to filling & cementing material . Adv : Harder than die stone . Disadv : Shrinkage on setting . Loss of water on standing .

32. SILVER AMALGAM Similar to restorative material . Advantages : Harder dies . Reproduces fine details and sharp margins

33. DISADVANTAGES -Can be packed only to a rigid impression . Takes long time to reach maximum hardness . High thermal conductivity . Separating agent needed .

34. POLYMERS & FILLED POLYMERS Self cured acrylic resins , Polymeric materials with fillers . ADV : More abrasion resistant . Not as brittle as die stone . DISADV : Shrinkage on polymerisation .

35. MEATAL SPRAYED DIES A Bismuth – Tin alloy (MP -138*c) can be sprayed directly on to an impression to form a metal shell which can be filled with dental stone . ADV : Can be obtained rapidly from elastomeric impression material . DISADV : Care should be taken to ptrevent abrasion if the alloy is soft .

36. Advantage: Less time consuming than electroplating Disadvantage: Alloy is soft low abrasion resistance Complex equipments required Inhalation of spray dangerous Compatible with elastomeric impressions only.

37. CERAMIC DIE MATERIALS Two types of materials are available . .One without using the platinum foil matrix for porcelain restorations . 2) . A ceramic material ,supplied as a powder & liquid

38. DIE SPACER Provides space for the luting agent Olden days: etching or milling  to get space

39. Various materials used as die spacers Finger nail paint Lacquer Model air craft dope

40. Should flow uniformly and smoothly Color should be readily identifiable on the die Thinners are available to decrease the viscosity of die spacer.

41. Brush strokes in one direction Wait for 2 mins before applying Should be applied 0.5-1mm short of margin

42. Die Spacer Pens (Kerr Laboratory) Poly fiber disposable tip. 0ptimal thickness is 20-40micrometre

43. 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 Acrylic resin lacquer .

44. 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 Optimal thickness : 2-3 micrometre .

45. Die Separator Easy removal of wax pattern without damaging margins. Applied with brush excess to be removed with tissue paper

46. DIE SYSTEMS Working cast with separate die Working cast with removable die Dowel pin system . Di – Lock Tray system . Pindex system . Accutrac system .

47. 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.

48. 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

49. Procedure Both working cast and sectional die can be obtained by: Pouring impression twice Making two impressions

50. Preparation of separate die Stone added to side of impression in small increments Tray tilted to fill the Impression  displacing air as it moves

51. 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

52. Pour stone to receive working cast Make base Retrieve cast

53. Trim sectional cast Octagonal in shape Sides  parallel or slightly taper towards base Handle 1 inch long

54. Pear shaped acrylic bur  trimmed apical to finish line Final trimming  sharp blade Smoothened

55. Contour be approximately like root  To facilitate good axial contours in the restoration .

56. Finish line highlighted with red pencil Not to use black graphite pencil Apply die spacer

57. Fabrication of FPD Die of each part is left joined to each other by means of common base Edentulous ridge area cut back

58. 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

59. WORKING CAST WITH REMOVABLE DIE

60. 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

61. Methods of repositioning die in its working cast Systems using die pins Systems using pre formed plastic trays without die pins

62. 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

63. Conventional dowel pin systems Dowel pin (GPT 7): a metal pin used in stone casts to remove die sections and replace them accurately in the original position

64. Curved straight

65. Flat sided dowel Rounded single dowel pin Double straight dowel with common head (Bi pin)

66. Procedure (pre pour technique) Procedure Marking to act as guide in placement of pins (pre pour technique)

67. D) Straight pins with modeling clay E) Matchsticks

68. F) Bobby pins

69. Die stone poured into impression filling the impressions of teeth and covering the knurled end of the dowel pin

70. V- shaped orientation grooves made Separating media-area adjacent to each dowel pin

71. Small wax ball placed on tip of each dowel Boxing done

72. Curved dowel pin

73. Orientation grooves made

74. Di lok tray system

75. Snap apart plastic tray with internal orienting grooves and notches to reassemble the working cast and die. Before using  check for space in articulator

76. Cast poured 1inch ht No stone in lingual area Trim to fit Di lok tray

77. horizontal Grooves Fill tray ¾ with stone Seat the cast  cervical area of teeth be about 4mm above the edge Of tray

78. Disassemble the tray

79. Cut till ¾ length

80. PINDEX SYSTEM ( Coltene / Whaledent )

81. Similar to post pour dowel pin technique . Showed the least horizontal movement . Adv : Allows accurate placement of the die pins . Excellent if instrument is well maintained . Disadv : Special equipment is needed .

82. Accu - Trac Die Precision System ( Coltène Whaledent )

83. Used in fabrication of porcelain laminate veneers Removable die system that is modification of a plastic tray with internal grooves and notches The technique of obtaining die is similar to Di- lok system

84. Other systems include DVA Model system and Zeiser model system These systems use a precision drill and special base plates that are aligned and drilled to provide die removal Advantage: allows for expansion of stone , which is relieved by saw cuts

85. CONCLUSION A good impression and accurate die are the first steps towards the fabrication of an accurate restoration. Proper selection of the die material and its manipulation are paramount to achieve accuracy in the die.

86. Removable die systems are preferable, as they can be used with all impression materials , as no second pour is required. Proper sectioning of the cast and their reassembly depends on the system used. Choice of the die material and system depends on the operator, as none fulfills all the requirements. The advantage and disadvantage of each must be weighed.

87. References Herbet T Shillingburg - Fundamentals of Fixed Prosthodontics - 3 rd edition Notes on Dental Materials, E. C Combe - 6 th edition Contemporary Fixed Prosthodontics IIIrd Edition by Rosenthal, Land & Fujimoto. Kenneth J,. Anusavice - PhilipsScience of Dental materials- 10 th edition Robert G Craig- Restorative dental Materials- 11 th Edition William J. o brien - Dental matereials and their selection- 3 rd edition