DIE SYSTEMS and die material in dentistry

dental

1. DIE SYSTEMS There are two basic working cast and die systems WORKING CAST WITH A SEPARATE DIE WORKING CAST WITH REMOVABLE DIE

2. WORKING CAST WITH A SEPARATE DIE ADVANTAGE : Simple Ease of fabrication More accurate Because of the gingival tissues and other landmarks are intact, it is easier to obtain physiologically harmonious restoration contours when fabricating the wax pattern. No special equipment is required

3. DISADVANTAGE: The wax pattern must transferred from one cast to the other. I n the process one can destroy the internal adaptation of the wax pattern It is difficult to transfer fragile or complex wax pattern.

4. PROCEDURAL STEPS 1. IMPRESSION POURING Mixed die stone is applied with a brush onto the occlusal surface of the impression Impression of the prepared teeth filled with stone

5. Blotted stone formed into a root Stone root in position

6. 2.DIE PRPARATION Untrimmed die separated from the impression Trimming root of the die with lathe

7. Trimmed die Working cast

8. WORKING CAST WITH REMOVABLE DIE They are two types Pre poured technique : most of the devises can be oriented in the impression before it is poured. Post poured technique : The device is attached to the underside of a cast that has already been poured.

9. WORKING CAST WITH REMOVABLE DIE CAN BE CLASSIFIED AS: 1.Dowel pin system 1. Straight pin (single) a. Sleeve-Plastic -Metal b. Without sleeve 2. Straight pin (double) a. Sleeve-Plastic -Metal b. Without sleeve 3.Curved pin 2.Di lok tray system 3.Pindex system 4.Accutrac system

10. ADVANTAGE Convenient Wax pattern need not be removed from their respective dies when they are transferred to the working cast Eliminates discrepancies between separate die and working cast. No special equipment is required.

11. DISADVANTAGE Risk of introducing an error in the pattern if the die does not reseat accurately in the working cast if dowels are not placed properly. Interproximal margins can be damaged during the sawing procedure , particularly if clearance between a proximal preparation margin and the adjacent tooth is minimal.

12. If a removable die system is used, it should satisfy these requirements : 1 . The dies must be return to their exact original positions 2 . The dies must remain stable ,even when inverted 3 . The cast containing the dies must be easy to mount on an articulator Several methods can be employed to allow the repositioning of a die in its working cast.

13. Types of antirotational devices used for removable dies Flat-sided single dowel Single curved dowel Double straight dowels with a common head Two separate parallel dowels Keyed plastic outer tray

14. Dowel pins are available in various shapes and sizes Conventional dowel pins Small Large J-Pin Short index pin Long pin Short index pin Long pin

15. Several methods for positioning the pins To the marks on the borders of the impresson Using paralleling instrument Pin setter

16. STRAIGHT DOWEL PIN SYSTEM Dowel pins are positioned in the initial pour of the stone in impression with a pin setter

17. Separating medium is painted on the area of the cast adjacent to each dowel pin Small balls of wax are placed on tips of dowel pins

18. Wax balls are located by trimming base of the cast on the model trimmer Tips of dowel pin are exposed after removal of wax

19. Saw used to cut through the stone Saw cuts are made through initial pour of stone

20. Die is removed by tapping instrument with mallet Excess stone is trimmed

21. Die is ditched with a fissure bur Final working cast with trimmed, ditched removable dies

22. CURVED DOWEL PIN SYSTEM Curved dowel pin Positioning bar Straight pins The first pour of the die stone to the impression. The head of the dowel extends 1.0 -2.0 mm into the impression of the prepared tooth. The tail of the dowel points facially

23. Thin coats of separating medium is applied to the stone and dowels Boxing wax is placed around the impression ,with the tips of the Dowels sticking through.

24. A segment is removed by pressing on the exposed tip of its curved dowel

25. PINDEX SYSTEM A reverse drill press Dowel pins Plastic sleeves

26. Pour the impression in the die stone Trim the cast in a horse shoe shape

27. Position the cast on the drill stage. A light indicates the location of the drill. . Hold the cast firmly and depress the lever, this activates the drill and which penetrates into the cast. The hole should be cleanly drilled

28. Pin cemented Plastic sleeve placed Small balls of wax are placed on tips of dowel pins

29. The Pindex cast after sectioning Ditching done and spacer applied

30. DIE LOCKING SYSTEM DI-LOK TRAY SYSTEM This die – relating system has two main components : FULL ARCH TRAY : This is useful for indexing multiple preparation on both sides of the dental arch . SECTIONAL DI-LOK TRAY : This can be used for isolated or adjacent preparations such as inlay or onlay There are two die locking systems: DI-LOK TRAY SYSTEM ACCU-TRAC SYSTEM

31. DI-LOK TRAY SYSTEM- SECTIONAL DI-LOK TRAY It consists of two components: A rectangular index compartment with one wall that is made of a single indexed locking arm that can be opened and closed on a hinge. This locking arm securely holds the individual dies in place and allows for access to the die sections.

32. DI-LOK TRAY SYSTEM - FULL ARCH TRAY The full arch tray consists of 3 components: A grooved base An internally indexed outer arm. A posterior locking bar which joins the other components together in a rigid fashion

33. Impression is poured and the di-Lok tray is also filled. The tray is inserted into the impression while the stone is still wet.

34. After the die stone has fully set, the locking and the curved arms of the tray are removed. The dies are sectioned with the help of a saw.

35. The dies are separated along with the stone base Trimmed dies Assembled cast

36. ACCU-TRAC SYSTEM The system is similar in design to the full arch Di- Lok tray It consists of 3 main components: A blue flexible bas ,which confines the dental stone A precision indexed full arch tray containing a magnet in the centre position. The magnet is used to aid in mounting the tray to the articulator. 3 . Two independent, indexed, locking arms that securely contain the individual die for easy access.

37. ADVANTAGE OF DIE LOCKING SYSTEM Accurate Trays are reusable Cost effective Sectional trays are used for inlays and onlays No auxillay pins or dowels are needed are needed. Impression need to be poured once. Magnetic indexing on the Accu trac tray provides easy and clean mounting The removable dies have no movement in any direction.

38. DISADVANTAGE OF DIE LOCKING SYSTEM Time consuming The dental arch circumference does not always confirm to the universal die locking trays Much cast trimming is needed The indexing grooves in the Accu trac system are small and the die stone may easily fracture in these places during die removal.

39. DVA MODEL SYSTEM It uses a precision drill and special baseplates that are aligned and drilled to provide die removal ADVANTAGE: Compensates for expansion of cast, which is relieved by saw cuts. DISADVANTAGE: Special equipment needed Cost factor Quite technique sensiti ve.

40. Impression on alignment fixture Secured with putty Marking dowel pin locations On clear plate with twin tip marker

41. Drill holes for dowel pins Using drilling press Insert dowel pins

42. Impression is poured and stone is placed around dowel pin Alignment fixture is replaced over poured impression

43. Set cast is removed from baseplate with gentle tapping Cast is trimmed

44. Cast is sectioned Definitive cast trimmed with DVA model system

45. COMPARISON OF THE DIE SYSTEMS ADVANTAGE DISADVANTAGE Solid cast with individual die Straight forward procedure No special equipment Risk of introducing an error in the pattern Brass dowel pin Removable die facilitates waxing and carving Difficult to master Pindex Cast pouring unimpeded Special equipment needed Di-Lok Much less costly than Pindex Bulky Care needed during reassembly

46. CONCLUSION There are different techniques and different materials used for developing working casts and removable dies. Whichever technique or material we choose to use our ultimate goal is to fabricate an accurate fixed restoration. Careful attention to detail and precision are of utmost importance in providing the best possible service .