Investing and casting

Question 1

What is the purpose of the Sprue?

Answer 1

• Allows molten and volatile wax to escape from the mold

- Allows molten metal to flow into the mold

Question 2

The metal within the sprue must remain molten slightly longer than what?

Answer 2

-The metal that has filled the mold

Question 3

What gauge of sprue do you use for a molar?

Answer 3

10 gauge

Question 4

T/F In general smaller sprues are better because it provides a better reservoir to remain molten

Answer 4

False

-Later sprues

Question 5

What do all investements have?

Answer 5

• Binder Refractory material

- Modifier

Question 6

What does the refractory material do?

Answer 6

-Doesn’t burn or combust

Question 7

What is the most common simplest investment around used for gold?

Answer 7

-Gypsum bonded

Question 8

What is the problem with a gypsum bonded investment?

Answer 8

-If you heat it to much it will combust and burn up

Question 9

What is the phosphate bonded investment used for?

Answer 9

PFM

Question 10

T/F Stone and investments contract when setting

Answer 10

False,

-They both expand during setting

Question 11

T/F A casting that is slightly oversized is advantageous for accurate seating

Answer 11

True

Question 12

What are factors that increase expansion in gypsum bonded investments?

Answer 12

• Decreased water/powder ratio
• Prolonged spatulation
• Water bath set (100 F for 1 hr immediately after investing
• Use a dry ring liner
• Use two ring liners
• Use ringless investment technique

Question 13

What does adding water in gypsum bonded and phosphate bonded investments do?

Answer 13

-Decrease expansion

Question 14

What is quenching?

Answer 14

-Casting is placed in water when the button no longer has a red glow

Question 15

What does quenching result in?

Answer 15

-More malleable alloy