DIE PREPARATION AND DIE SYSTEMS.pptx

In Prosthodontics, die preparation is a critical step in the fabrication of indirect restorations, such as crowns, bridges, inlays, and onlays. A die is a positive reproduction of a prepared tooth used to fabricate these restorations. The process involves making an accurate impression of the prepared tooth, pouring it with a die stone to create a durable and precise model. Careful trimming and finishing of the die are crucial to accurately replicate the margins and contours of the preparation, allowing for the precise fabrication of the final prosthesis. Die systems, which include removable die systems, solid cast systems, and articulated systems, are designed to facilitate the detailed work needed for these restorations, ensuring precise margins and occlusal contacts. Proper die preparation and selection of an appropriate die system are essential for achieving optimal fit, function, and aesthetics of the final prosthesis.

1. DIE PREPARATION AND DIE SYSTEMS D R. SATVIKA PRASAD MDS DEPARTMENT OF PROSTHODONTICS

2. CONTENTS Introduction Definitions Requirements of a die Materials used for fabrication of die Compatibility of die materials with impression materials Die systems Different types of dowel pins Different systems for dowel preparations Conclusion

3. 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

4. Definitions Die - It is the positive replication of the form of a prepared tooth in any suitable substance . GPT 7 Working cast- it is a master cast that reproduces the entire arch including the prepared and unprepared teeth, relevant soft tissues, and edentulous areas. Die pin / dowel pin – a metal pin used in stone casts to remove die sections and replace them accurately in the original position –GPT 8

5. Requirements of a die Reproduce the preparation exactly All surface should be adequately duplicated Avoid voids in the margins Adequate access to margin is imperative Adequately rigid Compatibility with the impression materials Mechanical properties- A) High strength to reduce the likelihood of accidental breakage B) Abrasion resistance so that the die can withstand the manipulative procedures during carving of wax pattern Economical Easy to use

6. Materials used for fabrication of die Gypsum products- A) Type IV (High strength) dental stone B) Type V (High strength and expansion) dental stone Electroformed dies- A) Electroplated Copper B) Electroplated silver Epoxy resins Silico -phosphate cement Amalgam dies Ceramic dies Metal sprayed dies

7. Compatibility with impression materials - Dental stone Impression compound Zinc oxide eugenol (ZOE) Alginate Impression plaster when used with separator Rubber base material Electroplated Cu Impression compound Electroplated Ag Polysulphide Rubber base material Epoxy resin Rubber base material Resin Polyether Polysulphide Addition silicone

8. Gypsum products These are the most commonly used materials 2 CaSO4 . 2H2O (CaSO4).H2O + 3H2O Calcium sulphate dihydrate Calcium sulphate hemihydrate

9. Electroplated dies Metal dies can be made by copper plating, compound impression or silver plating, rubber base impression, when a die is made in this manner the process is referred to as electroplating The areas to be plated are first coated with finely powdered silver or graphite to make them conduct electricity, and the impression is then placed in an electroplating bath. A layer of pure metal is deposited on the impression and is supported with type IV stone or resin. Polyether impressions, because of their hydrophilic nature, imbibe water and become distorted; they therefore cannot be plated accurately

10. ADVANTAGES DISADVANTAGES

11. Copper plating procedure Copper plated dies – compound or addition silicone rubber impressions Surface of the impression material is treated so that it conducts electricity, this process is called metallizing Coated impression is made cathode and copper plate is made anode Immersed in electrolytic solution of copper sulphate with alcohol / phenol and current of 15 amp is applied for 10 hrs.

12. Silver plating Indicated for polysulphide polyether, silicone rubber impression material Current applied is less than copper plating ~ 5mamp Similar to Cu plating Cathode- impression coated with Ag / graphite Anode – silver plate Electrolytic solution – alkaline solution of silver cyanide with potassium cyanide & potassium carbonate in distilled water Precaution:- Care must be taken to avoid the addition of acids to the cyanide solution, which can cause release of cyanide vapour a death chamber gas. Cu plating should not be done in the same area where Ag plating is done, because the risk of contamination of Ag plating solution with acidic Cu plating solution

13. Amalgam die They are made by packing the amalgam into impression made of impression compound Material of choice previously but replaced by electroplated dies Resistant to abrasion ADVANTAGES 1. Dies made of amalgam exhibit superior strength, resistance to abrasion and reproduce fine details and sharp margins 2. Can be packed only to a rigid impression DISADVANTAGES 1.Dimensional accuracy may vary from one die to other 2. Time required for fabricating is lengthy (procedure=30min ;hardening of die = 12-24hrs) 3.High thermal conductivity so it can cool the pattern rapidly which may cause distortion of the pattern { so to overcome it the die should be warmed }

14. Silico - phosphate cement Similar to the filling and cementing material Powder is a mixture of silicate powder and zinc oxide liquid contains phosphoric acid ADVANTAGES DISADVANTAGES

15. Epoxy resin (polymers) Used with polyether, polysulphide or silicone Hardener polyamine causes polymerization Epoxy resin cannot be used with water containing agar and alginate materials because water retards the polymerization of the resin. Viscous when poured, porosity can occur ADVANTAGES DISADVANTAGES

16. Metal sprayed dies Bismuth- tin alloy which melts at 138 ̊C can be sprayed directly on to an impression to form a metal shell which can be filled with dental stone & solidify at 30 pounds of pressure ADVANTAGE a metal coated die can be obtained rapidly from elastomeric impression materials DISADVANTAGE the alloy is soft, care is taken to prevent abrasion of the die

17. POLYURETHANE It is the most accurate, strongest and cleanest die material than die stone and epoxy Silicone impression material is used Properties- No noticeable shrinkage or expansion More accurate than epoxy Water resistant Superior mechanical properties Uses- Long span bridges, inlay, onlay Excellent for scanning Fabricating CAD/CAM models Shoulder and partial crown preparations

18. Ceramic die materials Recent advance in die materials Porcelain inlays, onlays , veeners Manipulation- Supplied as powder and liquid system Mixed into paste and vibrated into the impression and allowed to set for an hour and then fired at 600 ̊C for 8 min to produce a strong die

19. W orking cast with separate die 01 W orking cast with a removable die 02 Die Systems - Two basic die systems

20. Working cast with separate die Obtained from – Separate impressions Pouring an elastomeric full arch impression twice first cast is used for the fabrication of die This technique can be used only with elastomeric impression, since hydrocolloid is torn and distorted too much for the 2 nd pour

21. 8 Stone is added to the impression in small increments above the preparation Tray is tilted to fill the impression Stone is added to the impression so that base of the set stone will be 1” 1”

22. The die is smoothened below the finish line with discoid end of a tanner carver Shaping of the handle near the finish line is completed with a scalpel The prepared finish line on the die should be outlined with a red pencil

23. Working cast with removable die R equirements of removable die system – D ies must return to their exact original positions D ie must remain stable, even inverted C ast containg the dies must be easy to mount on an articulator

24. Method of repositioning the die- Pre pour technique – devices are oriented into the impression before pouring the stone Post pour technique – devices are oriented into the impression after pouring the stone Methods of repositioning die in its working cast Systems using pre formed plastic trays without die pins 1 2

25. Different types of dowel pins Tapered, flat sided brass dowel pin Flat sided, stainless steel dowel pin Curved, single dowel pin Single dowels Double dowels Two separate dowels Horizontal contact tracks and vertical ribs Flat sided single dowel Single curved dowel Double straight dowel with common head Two separate parallel dowel Keyed plastic out tray

26. Systems for die preparations Straight dowel pin Curved dowel pin PINDEX system DI-LOK system ACCUTRAC ( veeners ) ZEISER system MONOTRAC ARTICULATION

27. S traight dowel pin C ommonly used for many years Brass dowel pin is used ADVANTAGES DISADVANTAGE

28. Sticky wax is used to stabilize the whole assembly Dowel pins are placed over the preparation in the impression using bobby pins Type IV (high strength) or type V (high strength and expansion) dental stone is used. Water and stone are first hand mixed till powder gets wet and then vacuum mixing is done for 15 sec. First small amount of stone is placed on the side of the preparation and is vibrated till the stone reaches the occlusal surface. Add stone in small increments and build stone to a height of 1” or 2.5 cm to have adequate bulk. Pouring impression Paper clips Bobby pins 1 2 3 4 5

29. Curved dowel pin Incorporate into the impression before or after the stone is poured

30. P rocedure for pre pour technique Curved dowel is placed in the impression using finger pressure, through a positioning bar The bar is oriented facio-lingually and the head of the dowel extends 1-2 mm into the impression Straight pins are places through the positioning bar, on the facial and lingual aspects of the impression, these are used for stabilization. Stone is poured into the impression Straight pins and positioning bar are removed after the stone is set Separating medium is applied and the cast is boxed Base is poured Dies are cut using a saw Dies are separated by tapping at the protruding end of the curved dowel

31. 1 2 3 4 5 (For indexing)

32. Post pour technique is used Reverse drill press is used to create a master cast The machine accurately drills parallel holes from the under side of the trimmed cast PINDEX System

33. Mark the finish line with red pencil and be careful not to destroy the finish line Prepare the die with tungeston and rose head burs and sand paper Die trim

34. ADVANTAGE Allows accurate placement of the die pins DISADVANATGE Special equipment is required COMPLETING THE DIE

35. DI – LOK TRAY A snap apart plastic tray with internal orienting grooves and notches is used

36. ACCUTRAC The model and base are poured as one, eliminating the additional work when using pins and sleeves It is a modification of a plastic tray with internal orientation grooves and notches

37. One pour technique One universal tray size Economical Low base height Advantages

38. ZEISER SYSTEM The double expansion of the base & in the teeth leads to undesirable heights and axial displacements of the whole model In Zeiser model, the original dimensions of the impression of on a dimensionally stable base plane transfer is done to avoid undesired discrepancies

39. MONOTRAC ARTICULATION Monotrac Articulation has evolved as the first single-pour, cast-in-place, and pin-less articulation system. Vertical single pour base (VSP)

40. Trim the impression Spray silicone spray on cones to separate the stone Map pins are used – act as guide for placement Retrieve the model by tapping SILICONE SPRAY

41. Section the models Because there are no natural vertical stops, this particular case will require full tripod vertical stabilization to hold solid centric location. A combination of plug-in vertical stop and Cast-In Place Stop Heads will be used

42. The model is closed into the cup to dry fit check for clearance After the plaster has set up, remove the cup, rubber bands and break away the retainer tabs from the Stop Heads to allow the articulator to open up The Pic-Up Cup is poured with dental plaster

43. Advantages Simple and fast  Eliminating labor intensive pinning and basing procedures Easily removed and re-seated with solid stable precision. Even lower anterior, the thinnest of dies, resist lateral movement. The plug-in adjustable vertical stops are easy to place and eliminate the need for a metal articulator set up Does not require stone basing, cross arch and linear secondary base expansion issues

44. CEREC system The ED4 (D4D TECH) DCS PRECIDENT System iTERO LAVA Dies for CAD/ CAM system

45. CEREC System

46. Designed for metal copings for PFM Conventional wax up required Touch probe Acceptable marginal adaptability Concludes that manual adjustment significantly improves marginal accuracy of CAD / CAM system fabricated titanium copings. The highest marginal accuracy was achieved with the DCS system, using a longer refinement time. DCS PRECIDENT System

47. It uses a camera that takes several views (stills), and uses a strobe effect as well as a small probe that touches the tooth to give an optimal focal length. NO use of powder iTERO

48. Chair side oral scanner, takes a completely different approach using a continuous video stream of the teeth Crowns from intra oral scans revealed signs of better marginal fit than crowns from silicone impressions These tend to show better interproximal contact area quality LAVA ADVANTAGES Saves time and 1 visit in –office systems Opportunity to view occlusion Accurate restorations created Wear and chip resitant No casting / soldering errors Cross infection control

49. The choice of a specific technique relies on operator preference and after assessment of each methods advantages and disadvantages. 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. Conclusion

50. Shillingburg HT, Hobo S, Whitsett LD, Jacobi R, Brackett SE. Fundamentals of fixed prosthodontics. Chicago, IL, USA: Quintessence Publishing Company; 1997 Jan. Anusavice KJ, Shen C, Rawls HR, editors. Phillips' science of dental materials. Elsevier Health Sciences; 2012 Sep 27. Rosenstiel SF, Land MF, Walter R, editors. Contemporary fixed prosthodontics-e-book. Elsevier Health Sciences; 2022 Jun 22. Rudd KD, Morrow RM, Eissmann HF, editors. Dental Laboratory Procedures: Fixed partial dentures. Mosby; 1979. Touchstone A, Nieting T, Ulmer N. Digital transition: the collaboration between dentists and laboratory technicians on CAD/CAM restorations. The journal of the American dental association. 2010 Jun 1;141:15S-9S. Mansueto MA, Phoenix RD. A comprehensive approach to die trimming. Journal of Prosthodontics. 1994 Dec;3(4):251-5. Thornton LJ. Simplified procedure for preparing removable dies. Journal of Prosthetic Dentistry. 2001 Mar 1;85(3):306-7. References