Deck 12: Casting and Soldering

Question 1

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.

Answer 1

both A and C.

Question 2

Phosphate-bonded investments:

A) use a gypsum investment binder.
B) use a silica refractory.
C) are used for ceramic-alloy restorations and many partial denture frameworks.
D) both A and B.
E) both B and C.

Answer 2

both B and C.

Question 3

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

A) Expansion of the investment from added water is called hygroscopic 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) A and C are true statements.

Answer 3

A, B, and C are true statements.

Question 4

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

A) 100° C
B) 100° F
C) 500° C
D) 500° F
E) 1000° C

Question 5

The required temperature of a burnout oven for proper casting will vary,depending on:

A) type of investment.
B) liquidus of the alloy to be cast.
C) composition of the alloy to be cast.
D) A, B, and C.
E) A and C.

Question 6

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 7

If molten alloy were cast into a ring at room temperature,the:

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

Question 8

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) Both statements are true.
B) Both statements are false.
C) The first statement is true; the second statement is false.
D) The first statement is false; the second statement is true.

Question 9

The amount of thermal expansion of the investment is regulated by:

A) type of silica refractory used.
B) temperature used during burnout.
C) type of inlay wax used.
D) A and B.
E) B and C.

Question 10

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

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

Question 11

The purpose of a sprue is to:

A) form the occlusal surface of a casting.
B) form a channel in investment through which the molten alloy travels to form the casting.
C) form the proximal surface of a casting.
D) reduce the metal content of a casting.

Question 12

Before investing,a surfactant may be used to:

A) wet the ceramic-paper liner.
B) liquefy the investment material.
C) aid the flow of the investment material over the wax pattern.
D) reduce residual stress in the wax pattern.

Question 13

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

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

Question 14

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 15

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 16

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 17

An invested wax pattern is allowed to set for at least _____ before burnout.

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

Question 18

Most casting is done:

A) by press molding.
B) by slip casting.
C) in a linear casting machine.
D) in a centrifugal casting machine.

Question 19

The investment material is _____; the wax pattern is _____.

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

Question 20

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 21

The blowtorch used 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 22

Investment is retained in a __________ while it sets.

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

Question 23

Casting alloys are melted using:

A) a blowtorch.
B) an electric current.
C) a casting oven.
D) all of the above.
E) only A and B.

Question 24

If a metal sprue is used,it must be:

A) coated with a surfactant.
B) removed before casting.
C) burned out with the wax.
D) secured in the investment.

Question 25

If base-metal castings are pickled,_____ will occur.

A) oxidation
B) corrosion
C) tarnish
D) shrinkage

Question 26

A sprue forms a channel in the investment through which the molten alloy travels to form the restoration.Sprues often are wax but also may be plastic or even metal.

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 27

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

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

Question 28

Pickling a casting:

A) removes surface oxides.
B) uses hot calcium carbonate.
C) uses hot sulfuric acid.
D) A and B.
E) A and C.

Question 29

The purpose of flux is to minimize:

A) melting time.
B) melting temperature.
C) oxidation.
D) freezing time.

Question 30

Rapidly cooling a casting in cold water is referred to as:

A) soldering.
B) brazing.
C) pickling.
D) bench cooling.
E) quenching.

Question 31

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 32

Because cast metal shrinks as it freezes,investment must _____ as it sets.

A) shrink
B) expand
C) stay the same

Question 33

The sprue is removed with a thin _____ disc.

A) carbide
B) stainless steel
C) carborundum
D) diamond

Question 34

The type of flux used during dental castings depends upon all of the following except the:

A) liquidus of the casting alloy.
B) type of heat source used to melt the alloy.
C) type of casting alloy.
D) type of investment.
E) type of wax.

Question 35

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 36

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 37

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 38

The investment used in casting is _____; the wax pattern is _____.

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