Die materials and die system in prosthodontics

die
die material
die system

1. DIE MATERIALS

2. DEFINTIONS DIE : the positive reproduction of the form of a prepared tooth in any suitable substance ( GPT 9 ) DIE SPACER : an agent applied to a die to provide space for the luting agent in the finished casting. (GPT 9)

3. PREREQUISITES FOR DIE

4. REQUIREMENTS OF THE DIE MATERIALS Should have, accuracy and dimensional stability . a smooth, hard surface which should not easily abrade . Should be compatible with impression material . high strength . good color contrast . Economical. able to manipulate easily and fast . ability to reproduce fine details & sharp margins .

5. CLASSIFICATION OF DIE MATERIALS

6. Gypsum products ADA specification No . 25 Five types: Type 1. Impression plaster Type 2. Model plaster / plaster of paris Type 3 . Dental stone / Hydrocal Type 4 . Dental stone, high-strength / Densite / Die stone Type 5 . Dental stone, high-strength, high-expansion The most commonly used materials for fabrication of a die are Type IV and Type V gypsum products .

7. Advantages disadvantages 1)compatible with all impression materials. 1)Poor surface hardness 2)Have ability to reproduce fine detail and 2)abrasion during carving of sharp margins. wax pattern on the die 3)Dimensionally accurate and stable. 3)Prone to fracture 4)Easy to use.

8. DIE STONE INVESTMENT COMBINATION A commercial gypsum bonded material, called Divestment is mixed with colloidal silica liquid. The die is made from this mix and the wax pattern constructed on it. it can be used only for gold alloys.

9. Advantage Highly accurate technique for use with conventional gold alloys Disadvantage Divestment  gypsum bonded material not recommended for high fusing alloys

10. ELECTROPLATED/ ELECTROFROMED DIES ELECTROPLATING : THE PROCESS OF COVERING THE SURFACE OF AN OBJECT WITH A THIN COATING OF METAL BY MEANS OF ELECTROLYSIS ( GPT-9 ) THE ART OF ELECTROFORMING IS CALLED AS GALVANOPLASTY.

11. electroforming compound impressions require copper and elastomeric impressions require silver.

12. ADVANTAGES Hard and abrasion resistant Dimensionally accurate Reproduce finer details Prevent cuspal wear due to repeated contact with opposing cast DISADVANTAGES 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

13. SILVER PLATED DIES Anode Cathode Electrolytic solution Source of current

14. Impression materials compatible 1)Polysulfide 2) Silicones- disortion Not compatible 1)Polyether 2)Hydrocolloids(reversible and irreversible) 3)Impression compound

15. Copper plated dies

16. Impression materials compatible Silicones Impression compound Not compatible Poly ether Hydrocolloids (reversible and irreversible) Polysulfide

17. 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

18. AMALGAM DIE 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 USED ONLY IN COPPER BAND IMPRESSIONS WITH MODELLING COMPOUND.

19. 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. CONTRAINDICATED WITH RUBBER BASE IMPRESSIONS DUE TO ELASTIC PROPERTIES OF THE MATERIAL SO IT WILL NOT WITHSTAND THE FORCES OF AMALGAM CONDENSATION.

20. Resin dies Resins are used as die materials to overcome the low strength and abrasion resistance of die stones. They are self curing polymeric materials with fillers eg : Epoxy resin dies Acrylic resin die Polyester resin dies Not compatible with –Hydrocolloid or impression compound Compatible with elastomeric impression materials

21. EPOXY RESIN Epoxy resin die : a reproduction formed in epoxy resin (GPT-9) Supplied as resin paste and liquid activator (amine)

22. ADVANTAGES Better abrasion resistance High compressive strength than dental stone. DISADVANTAGE More viscous than dental stone so more entrapment of air in the preparations. Shrink upto 0.02% on polymerization

23. ACRYLIC RESIN DIES They have adequate surface hardness and abrasion resistance but undergo shrinkage on polymerization. PMMA resins are used. Polymerization shrinkage is 0.6% Can not be used for accurate die.

24. FLEXIBLE DIE MATERIALS 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.

25. ADVANTAGES Less time required (rapid setting) Ease of removal of interim restoration or inlay. DISADVANTAGE Expensive Surface details poor

26. SILICATE CEMENT DIES It is similar to the filling and cementing material. Advantages: Initial strength and surface hardness is superior to that of die stone. Disadvantages: The cement contracts during setting and may be dimensionally inaccurate. There is loss of water on standing, causing a rough and dehydrated surface. High viscosity predisposes to surface voids.

27. Ceramic dies Ceramic : of or relating to the manufacture of any product made essentially from a nonmetallic mineral (as clay) by firing at a high temperature ( GPT-9)

28. Die hardner MATERIALS APPLIED ON THE SURFACE OF DIE TO INCREASE THE SURFACE HARDNESS. IT ALSO PREVENTS THE DIE SPACER FROM SEEPING INTO THE DIE.

29. Die spacer An agent applied to a die to provide space for the luting agent in the finished casting (GPT-9) This material is applied to the die to increase the cement space between the axial walls of the prepared tooth and the restoration

30.   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.  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.

31. Die Separator Separating fluid between the die cast and the base. Also used on split casts and with flasks in prosthetic dentistry Easy removal of wax pattern without damaging margins. Applied with brush, excess to be removed with tissue paper. Also known as die lubricant   Eg : Kleen lube (Kerr), Picosep ( Renfert ), Dielube wax sep

32. CONCLUSION 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 much closer to perfection