Deck 12: Casting, Soldering, and Welding

Question 1

Depending on ______________, the required temperature of a burnout oven for proper casting will vary.

A) type of investment
B) liquidus of the alloy to be cast
C) solidus of the alloy to be cast
D) A, B, and C are all correct.
E) Only A and B are correct.

Answer 1

Only A and B are correct.

Question 2

What is the purpose of the sprue?

A) Provides access channel for molten alloy to reach casting
B) Form the occlusal surface of a casting
C) Form the proximal surface of a casting
D) Reduce the metal content of a casting

Answer 2

Form the occlusal surface of a casting

Question 3

If molten alloy was cast into a ring at room temperature, what will occur?

A) Casting would be much larger than the die.
B) Margins of the casting would be complete.
C) Investment would partially decompose.
D) Investment would likely crack.

Answer 3

Investment would partially decompose.

Question 4

Following removal of a ring from the burnout oven, any delay in casting of more than ___________ will severely compromise the fit and quality of the cast restoration.

A) 1 to 2 seconds
B) 8 to 10 seconds
C) 20 to 30 seconds
D) 60 to 90 seconds
E) 2 to 3 minutes

Question 5

Which of the following is correct about phosphate-bonded investments?

A) Use a silica refractory
B) Use a gypsum investment binder
C) Are used for ceramic-alloy restorations
D) Both A and C
E) Both B and C

Question 6

Which of the following sequences describing the steps involved in making a dental casting from start to finish is correct?

A) Burnout, casting, making the wax pattern, spruing the pattern, investing, removal of investment, pickling, and finishing
B) Making the wax pattern, burnout, casting, spruing the pattern, investing, removal of investment, pickling, and finishing
C) Making the wax pattern, spruing the pattern, burnout, casting, investing, removal of investment, pickling, and finishing
D) Making the wax pattern, spruing the pattern, investing, burnout, casting, removal of investment, pickling, and finishing

Question 7

What method is used to inject the molten alloy into the casting ring?

A) Slip casting
B) Press molding
C) Linear casting machine
D) Centrifugal casting machine

Question 8

To prevent premature freezing in the sprue channel, sprues are generally as _____ in diameter and as _____ as possible.

A) small; long
B) small; short
C) large; long
D) large; short

Question 9

What regulates the amount of thermal expansion of the investment?

A) Temperature used during burnout
B) Type of silica refractory used
C) Type of inlay wax used
D) A and B
E) B and C

Question 10

The total expansion of the investment is the sum of the hygroscopic and thermal expansions. Investments rely primarily on hygroscopic expansion to compensate for casting shrinkage of the metal.

A) The first statement is correct; the second statement is correct.
B) The first statement is correct; the second statement is incorrect.
C) The first statement is incorrect; the second statement is correct.
D) The first statement is incorrect; the second statement is incorrect.

Question 11

An invested wax pattern should set for at least ________ before burnout.

A) 10 minutes
B) 45 minutes
C) 12 hours
D) 24 hours
E) 1 week

Question 12

Which of the following statements is(are) true concerning expansion of an investment material?

A) Expansion of the investment from added water is called hydroscopic expansion.
B) Investments are designed to expand to compensate for casting shrinkage.
C) Expansion of the investment from heat is called thermal expansion.
D) A, B, and C are true statements.
E) B and C are true statements.

Question 13

Why is a surfactant used prior to investment?

A) Wet the ceramic-paper liner
B) Liquefy the investment material
C) Reduce residual stress in the wax pattern
D) Aid the flow of the investment material over the wax pattern

Question 14

The accuracy of a cast crown may be as good as ____% in dimensional change from the wax pattern if care is taken to perform each step properly.

A) 1
B) 0.5
C) 0.1
D) 0.05
E) 0.01

Question 15

The temperature in a burnout oven is commonly _____ for high noble alloys.

A) 100° C
B) 100° F
C) 500° C
D) 500° F

Question 16

What is the purpose of a casting ring?

A) Retains the investment while it sets
B) Is commonly lined with a dry ceramic-paper liner
C) Is commonly lined with a wet ceramic-paper liner
D) Both A and B
E) Both A and C

Question 17

Which of the following statements is(are) true of sprues?

A) Sprues may be made of wax, plastic, or metal.
B) Sprues are placed on cusps of the wax pattern.
C) Sprues are placed in the central groove of the wax pattern.
D) A and B are true statements.
E) A and C are true statements.

Question 18

Which of the following statements is true of investments used for casting?

A) The refractory material in most dental investments is a form of calcium.
B) The binder and the refractory material contribute to expansion of the investment.
C) The binder and the refractory material contribute to contraction of the investment.
D) The binder, but not the refractory material, contributes to expansion of the investment.
E) The refractory material, but not the binder, contributes to expansion of the investment.

Question 19

A casting alloy is heated in a _________ made of heat-resistant ceramic.

A) burnout oven
B) casting ring
C) sprue base
D) crucible

Question 20

The investment material is _________; the wax pattern is __________.

A) hydrophilic; hydrophilic
B) hydrophilic; hydrophobic
C) hydrophobic; hydrophilic
D) hydrophobic; hydrophobic

Question 21

Expansion of the binder from added water to the investment is called ________ expansion.

A) hygroscopic
B) chemical
C) burnout
D) thermal

Question 22

It is important that the temperature of the molten metal not be more than ________ than the burned out investment.

A) 500° F higher
B) 500° C higher
C) 500° F lower
D) 500° C lower

Question 23

What will occur if base-metal castings are pickled?

A) Tarnish
B) Oxidation
C) Corrosion
D) Crystallization

Question 24

Investment is retained in a __________ while it sets.

A) mold
B) crucible
C) centrifuge
D) casting ring

Question 25

During the casting process, how is a metal sprue treated?

A) Coated with a surfactant
B) Removed before casting
C) Burned out with the wax
D) Secured in the investment

Question 26

Once a molten alloy freezes, what is the percentage of shrinkage that may occur?

A) 0.5% to 1.0%
B) 1.0% to 2.5%
C) 1.5% to 2.0%
D) 1.2% to 2.5%

Question 27

Which factor below does not determine the type of flux used during dental castings?

A) Type of heat source used to melt the alloy
B) Liquidus of the casting alloy
C) Type of casting alloy
D) Type of investment
E) Type of wax

Question 28

Which is the correct order of operations to construct a cast appliance?

A) Wax pattern, investment, sprue, burnout, cast
B) Investment, wax pattern, sprue, cast, burnout
C) Wax pattern, sprue, cast, burnout, investment
D) Wax pattern, sprue, investment, burnout, cast

Question 29

Which of the following will flux minimize?

A) Oxidation
B) Melting time
C) Freezing time
D) Melting temperature

Question 30

How are casting metals melted?

A) A blowtorch
B) A casting oven
C) An electric current
D) Only A and B are correct.
E) Only A and C are correct.

Question 31

Which of the following is an advantage to using wax when constructing an indirect restoration?

A) Flows easily
B) Releases stress
C) Does not distort
D) May be formed on the tooth

Question 32

Most dental solders are silver or gold alloys. Only certain types of alloy solders require flux.

A) Statement 1 is correct; statement 2 is correct.
B) Statement 1 is correct; statement 2 is incorrect.
C) Statement 1 is incorrect; statement 2 is correct.
D) Statement 1 is incorrect; statement 2 is incorrect.

Question 33

What will occur if the molten metal and the investment material are too far apart in temperature?

A) The metal will solidify too quickly.
B) There will be too much shrinkage.
C) The investment will crack.
D) The metal will crack.

Question 34

The investment used in casting is ________; the wax pattern is __________.

A) hydrophobic; hydrophobic
B) hydrophobic; hydrophilic
C) hydrophilic; hydrophilic
D) hydrophilic; hydrophobic

Question 35

For some gold-based alloys, bench cooling produces a ________, ________ state of the alloy referred to as a(n) ____________.

A) harder; weaker; ordered solution
B) harder; stronger; ordered solution
C) softer; weaker; eutectic
D) softer; stronger; eutectic

Question 36

Which statements are correct regarding the pickling of a casting?

A) Uses hot calcium carbonate
B) Removes surface oxides
C) Uses hot sulfuric acid
D) A and B
E) B and C

Question 37

Because cast metal __________ as it freezes, investment must __________ as it sets.

A) shrinks; shrinks
B) expands; shrinks
C) shrinks; expands
D) expand; expands

Question 38

Which term refers to rapidly cooling a casting in cold water?

A) Brazing
B) Pickling
C) Quenching
D) Bench cooling

Question 39

The sprue is removed with a thin _____ disk.

A) cuttle
B) carbide
C) diamond
D) carborundum

Question 40

Which characteristics are necessary for a blowtorch to heat casting alloys?

A) May operate on a combination of natural gas and compressed air for low-temperature alloys
B) May operate on a combination of natural gas and oxygen for higher temperature alloys
C) Must heat the alloy sufficiently to ensure a low viscosity of the alloy for casting
D) A, B, and C
E) A and C

Question 41

Explain the advantages and disadvantages of using inlay wax to construct an indirect restoration.

Question 42

Compare and contrast casting with milling.

Question 43

Approximately how long does it take for the wax to burn out in the kiln?

A) 30 minutes
B) 1 hour
C) 1.5 hours
D) 2 hours