Investing Procedure (2) Flashcards
Margin Adaptation
Want a smooth contour at the cavo-surface margin and close fit
Make sure there are no defects in the wax before continuing - wax up often requires rewaxing at the margin
Where should the Sprung be placed?
At the thickest area of the pattern
45 degress to the long axis of the prep
Not on the occlusal surface or proximal contact
What type of sprue should be used?
10 gauge
How long should the sprue be?
6mm at most
When should the wax pattern be sprued? Why?
Immediately - to avoid distortion
Investment Technique
Wet all surfaces of the wax with wax cleaner
Wet the ring liner
Gypsum bonded investment
Vacuum mix for 20 sec - 2 min working time, and use to fill casting ring
After filling, immediately place in 100F water bath
How long should the ring be in the water bath?
30min - 3 hr
What are the 2 sources of expansion?
- Setting expansion - powder provides the expansion (more poweder = more expansion)
- Water acts to feed crystal growth - increases expansion
What is the wax pattern elimination
a burnout that occurs in 2 stage
- 200F for 45 min
- 900F for 1 hr
How many turns should you wind the casting machine?
3 turns
What are the materials for the gold casting procedure
Crucible
Gold alloy
Cradle
Metal tongs
What should the torch flame look like?
10-12 inches
Well defined core
T/F - the flame should be kept constantly moving
True
T/F - don’t heat the crucible until the gold alloy is in it
False - preheat the crucible
How much gold should be placed in the crucible?
8 pennyweight
