Assalamu-alaikum DR. TAJAMMUL AHMED a.tajammul@gmail.com.

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Presentation transcript:

Assalamu-alaikum DR. TAJAMMUL AHMED a.tajammul@gmail.com

Fabrication of working casts and dies.

SPECIFIC LEARNING OBJECTIVES; At the end of the class student should be able; To define a die Type of die materials To enumerate the classification of die materials & die systems. To enumerate the steps involved in preparing working cast & dies.

Definition DIE: Die is a positive replica of the individual pre-pared tooth on which the inlays, crowns, bridges are made. These are individual tooth replicas prepared for; 1. easier handling during wax pattern fabrication and 2. finishing of inaccessible areas of the cast

TYPES OF DIE MATERIALS Gypsum: Type IV-dental stone, high strength Type V-dental stone ,high strength, high expansion Dental stone + lignosulphonates Metals: Electroformed/eletroplated. Sprayed metals. Amalgam. Polymers; Metal-filled resins or inorganic filled resins. Epoxy. Cements: silicophosphate or polyacrylic acid bonded cements. Ceramic or refractory die materials: For direct baking of porcelain crown or preparation of wax pattern for casting. Type IV& Type V Stone dies, Electroformed dies, Epoxy resins , Refractory materials are recommended die materials.

IDEAL PROPERTIES OF DIE MATERIALS It should be dimensionally accurate. It should have high abrasion resistance, should possess good strength,& have smooth surface . Toughness – to allow burnishing of foil & resist breakage. Ability to reproduce all fine details in the impression. Compatibility with all impression materials. Colour contrast with wax, porcelain & alloys. Easy & quick manipulation & rapid fabrication. Non-injurious to health by touch or inhalation. Economic.

IDEAL REQUIREMENTS OF A DIE SYSTEM The die should be easy to remove and replace in its original position. The die must be stable when placed in the cast. It should be easy to mount on the articulator

TYPES OF DIE SYSTEM Based on the design, die systems can be classified into: 2. Working cast with separate die system 1. working cast with removable die system three commonly used removable die systems, a)Dowel pin system -Straight -Curved b)Di-lok tray system c)Pindex system

WORKING CAST WITH A REMOVABLE DIE SYSTEM In this system a special type of working cast is prepared and the dies are carefully sectioned so that the individual dies can be removed and replaced in their original position in the cast. Methods of repositioning die in its working cast systems using die pins dowel pin systems Systems using pre formed plastic trays without die pins straight curved

Attached to the underside of the cast that has already been poured a. DOWEL PIN SYSTEMS They are prepared using two techniques, namely 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

PRE-POUR TECHNIQUE The dowel pin is positioned within the impression using sticky wax First pour is poured upto the level of the alveolar process Separating medium is applied and the base is poured After the cast is set, the dies are sectioned by placing vertical sections in the interproximal regions using a die sectioner. Since the separating medium was applied before pouring the second half of the cast, the dies can be easily separated with vertical sections alone.

POST-POUR TECHNIQUE Here, the cast is poured up to the level of the crowns of the teeth in the impression. Subsequently, small holes are drilled within the first pour in the required places and the dowel pins are cemented into the holes The remaining part of the cast is poured and the dies are sectioned as described in the pre-pour technique.

b. DI-LOK TRAY SYSTEMS In this technique to pour the cast, use special tray with orientation grooves on the inner aspect & is made of multiple components, which can be assembled or dismantled. Impression is poured using two-pour technique. The first pour is poured up to the level of the impression and the second or base pour is poured after positioning the rim of the di-lok tray over the impression. Later, the di-lok tray is dismantled and the grooves on the base of the cast formed by the di-lok tray is used as a guide to do die sectioning.

c. PINDEX SYSTEMS This system is similar to the post-pour dowel pin technique. Special drill press equipment is used to do die sectioning. The drill press has a platform with a slot like opening through which the drill pin will project during the procedure.

Base of cast togingival crest Die sectioning procedure is simple wherein the cast of 15 mm base is placed on the drill press and drill holes are prepared in the under surface of the base of the cast using the pilot light as a guide. The unit has a red pilot light lamp on top, which will shoot a point exactly on the drill & act as a guide while drilling Base of cast togingival crest 15-20 mm

After making the drill holes to the required depth, sleeved die pins are placed and cemented using cyanoacrylate adhesive. After cementing the pins, a base is poured over the base of drilled cast.

Dies are sectioned from underside and from occlusal aspect Working cast with removable die mounted on an articulator

WORKING CAST & SEPARATE DIE SYSTEM Here, two casts are poured from a single impression. One cast is sectioned and used as a die and The other is not sectioned and is used as the working cast. The wax pattern is prepared on the die and later transferred to the working cast. The die is shaped and finished using an acrylic trimmer and the portion of the die below the cervical line is finished using a scalpel. Sharp undercuts in the base should be avoided.

Working cast with separate die Procedure Both working cast and sectional die can be obtained by: Pouring impression twice or Making two impressions. Stone added to side of prepared teeth in impression in small increments. Tray tilted to fill the Impression displacing air as it moves Build the height of cast to approx 1 inch. Trim sectional cast to obtain die. Die contour be approximately like root to facilitate good axial contours in restoration

Working cast with separate die Advantages: Easy to fabricate Keeps relation between abutments fixed better contours and emergence profile while wax pattern fabrication. 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

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.

THANK YOU