Working Cast And Dies

Question 1

Define working cast?

Answer 1

Replica of prepared teeth, ridge areas, and dental arch

Question 2

Define die?

Answer 2

Positive reproduction of prepared tooth

Question 3

what are the requirements of a good cast?

Answer 3

1. free from bubbles
2. free from distortion
3. trimmed to insure access for carving wax pattern margins

Question 4

what are the requirements of dies?

Answer 4

1. accuratey reproduce prep. tooth
2. no bubbles
3. 0.5-1 mm remaining unprepared tooth structure cervical to FL should be apparent on the die

Question 5

what are the requirements of die materials?

Answer 5

1. high strength to withstand handling w/o fracture
2. high surface hardness to resist scratching or abrasion
3. excellent dimensional accuracy
4. compatible with impression material
5. compatible with separating medium
6. color contrast with other materials

Question 6

examples of working cast with removable die?

Answer 6

dowel pin technique 
pindex system
DI-LOK tray tech.
zeiser system
DVA system

Question 7

examples of single die?

Answer 7

stone die
amalgum die
acrylic & epoxy resin die
refractory die
flexible die
electroplated die

Question 8

requirements of removable die?

Answer 8

1. must return to exact original position
2. must remain stable even when inverted
3. cast must be easily mounted on articulator

Question 9

summarize pindex system?

Answer 9

1. wash impression w. cold water to remove mucous and saliva then dry.
2. stone IV (4) V (5). mix water and stone with spatula until powder is completely wet then use vacuum mixer.
3. place on vibrator. add small increments of stone on most distal area on one side of impression. slowly tilt distal end of impression mesially from tooth to tooth filling them from bottom
4. add stone until all teeth are filled then wait until setting then seperate cast from impression.
5. use cast trimmers to remove excess stone
6. pindex machine: light indicator, flat table, drill. drill parallel holes from underside of trimmed cast by using reverse drill press “pinholes”
7. dowel pin= cyanoacrylate cement to lute pins in their holes then apply seperating medium
8. base fabrication: mix stone of diff color to visualize where to end the saw cuts when sawing out dies by hand or spatula under vacuum. pour the stone mix. place working cast into base, base trimming.
9. sawing by saw frame with a thin blade to cut through a layer of wax. cut mesial and distal side of each die and they should taper toward each other slightly from occlusal to gingival. loosen the die using an instrument handle

Question 10

what happens in die preparation trimming?

Answer 10

die is removed from cast and any excess stone gingival to finish line is trimmed away. by bur or lancet blade

Question 11

die preparation ditching?

Answer 11

create undercut the contour of die apical to finish line should be like root

Question 12

die prep. finish line marking?

Answer 12

also called highlighting

we use a red pencil to facilitate carving the wax pattern margins

Question 13

die prep application of die spacer?

Answer 13

20-40 micron-thickness
provides room for luting agent complete seating of restoration
0.5-1mm away from f.l and good margin adaptation

Question 14

mounting on articulator

Answer 14

working cast and opposing cast are mounted on articulator

Question 15

dowel pin technique

Answer 15

working cast with removable die
step 1 and 2 like pindex
step 3 place dowel pin between arms of bobby pin which is positioned bucco-lingually across impression