Deck 11: Casting Alloys, wrought Alloys, and Solders

Question 1

Malleability is defined as:

A) the ability to be drawn into a wire.
B) the ability to be mechanically formed.
C) tarnish resistance.
D) corrosion resistance.

Answer 1

the ability to be mechanically formed.

Question 2

Gold is used in dental alloys primarily because of:

A) its resistance to corrosion.
B) its relatively high melting point.
C) its yellow color.
D) A, B, and C.
E) A and C.

Answer 2

its resistance to corrosion.

Question 3

Noble metals are defined by their:

A) resistance to corrosion.
B) inability to be used in an alloy.
C) indistinct melting point.
D) lack of malleability.

Answer 3

resistance to corrosion.

Question 4

Greening of ceramic may be avoided by:

A) selecting an appropriate alloy.
B) firing the restoration at the appropriate temperature.
C) periodic cleaning of the ceramic oven.
D) A, B, and C.
E) A and C.

Question 5

Silver is added to casting alloy to:

A) prevent oxidation.
B) enhance bond strength.
C) harden the gold.
D) prevent tarnish.

Question 6

_____ alloys are first cast but then shaped by mechanical force into their final forms.

A) Dental casting
B) Wrought
C) Ceramic bonding
D) Resin composite

Question 7

The best solution to the problem of debonding of ceramic from a ceramic-alloy restoration after cementation in the mouth is to:

A) remove the crown, refire new porcelain to the metal, and then recement the crown.
B) refire new porcelain to the metal while the crown remains in the mouth.
C) prevent debonding by selection of compatible alloys and ceramics and the proper manipulation of these materials during fabrication.
D) bond direct composite to the metal substructure.

Question 8

For ceramic-bonding alloys:

A) the solidus of the alloy must be higher than the fusion temperature of the ceramic.
B) the solidus of the alloy must be lower than the fusion temperature of the ceramic.
C) the coefficient of thermal expansion for the alloy should be less than that of the ceramic.
D) both A and C.
E) both B and C.

Question 9

If an alloy contains 40 wt % gold,20 wt % palladium,10 wt % platinum,and 30 wt % copper,the nobility would be _____ wt %.

A) 10
B) 20
C) 30
D) 40
E) 75

Question 10

_____ alloys are the most difficult to cast and polish of all the alloys.

A) High-noble
B) Noble gold-based
C) Noble palladium-based
D) Noble silver-based
E) Base-metal

Question 11

When a molten (liquid)alloy freezes,crystals _____ and _____ as the material cools.

A) dissolve; disperse
B) grow; disperse
C) form; dissolve
D) form; grow

Question 12

An alloy liquidus is defined as the temperature at which:

A) an alloy begins to melt.
B) all of the alloy melts.
C) some of the alloy freezes upon cooling.
D) all of the alloy freezes upon cooling.

Question 13

Which of the following is a noble metal?

A) Copper
B) Palladium
C) Nickel
D) Zinc
E) Titanium

Question 14

According to the ADA classification for dental casting alloys,high-noble alloys must have a noble metal content of at least ____% by weight.

A) 20
B) 40
C) 60
D) 80
E) 90

Question 15

Which of the following statements is true concerning noble and base metals?

A) Seven noble metals are commonly used in dental casting alloys.
B) Silver will not corrode in the oral environment.
C) The term precious metal is preferred over noble metal.
D) Base metals are viewed in dentistry as bad metals and are not used in dental restorations.
E) Base metals are required in dental alloys for strength, flexibility, and wear resistance.

Question 16

Wrought alloys have a grain structure often described as fibrous.The fibrous structure is responsible for increased yield strength and hardness compared with the cast form of the alloys.

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 17

Palladium:

A) has poor corrosion resistance.
B) has a much lower melting point than gold.
C) is much harder than gold.
D) may be used in pure form for dental restorations.
E) both B and C.

Question 18

Which of the following statements is(are)true of the density of an alloy?

A) The alloy with the highest density weighs the most.
B) High-density alloys are generally the most difficult to cast.
C) High-density alloys cost more than low-density alloys, because more mass is present in any given volume of restoration.
D) A, B, and C are true statements.
E) A and C are true statements.

Question 19

Which of the following statements is(are)true of dental alloy crystal structure and grains?

A) The areas between crystals in an alloy are called grain boundaries.
B) A small grain size is generally more desirable than a large grain size for dental alloy properties.
C) If an alloy is rolled into a sheet or drawn into a wire, the grain structure takes on a fibrous appearance.
D) A, B, and C are true statements.
E) A and C are true statements.

Question 20

The correct order of firing to create sintered alloy composites is firing:1.of a ceramic that mediates ceramic-alloy bonding.2.to create a spongy coping of high-noble metals.3.of a lower fusing alloy that is absorbed by capillary action.

A) 1, 2, 3
B) 2, 1, 3
C) 3, 1, 2
D) 1, 3, 2
E) 2, 3, 1

Question 21

The color of an alloy is a good predictor of its composition or other properties.Yellow alloys contain gold.

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 22

The ceramic must _____ and bond to the alloy at a temperature below the solidus.

A) liquefy
B) melt
C) flow
D) sinter

Question 23

Solder metals usually rely on _____ to encourage a lower melting temperature of the solder.

A) tin
B) copper
C) titanium
D) nickel

Question 24

People are most likely to have an allergic reaction to which of the following base metals used in dentistry?

A) Copper
B) Nickel
C) Tin
D) Titanium
E) Chromium

Question 25

Which of the following is not an organization that classifies and certifies alloys?

A) American Dental Association
B) Nordic Institute of Dental Materials
C) International Standards Organization
D) All of the above
E) Only A and C

Question 26

The _____ of an alloy is the mass in grams that occupies a volume of one cubic centimeter.

A) density
B) area
C) circumference
D) thickness

Question 27

Solders may be used in dentistry to join:

A) an orthodontic wire to a band in construction of a space maintainer.
B) a clasp wire to a partial denture framework.
C) two units of a fixed partial denture together after each are cast separately.
D) A, B, and C.
E) A and C.

Question 28

Common base metals used in dentistry include:

A) gold.
B) silver.
C) platinum.
D) palladium.

Question 29

The color of oxides on metal varies from _____ on high-noble alloys and some noble alloys to _____ oxides on some base-metal alloys.

A) dark gray; dark yellow
B) light yellow; light gray
C) light yellow; dark gray
D) dark gray; light yellow

Question 30

Biocompatibility of dental alloys is often based on _____ of the alloy.

A) long-term contact.
B) amount of corrosion.
C) combined elements.
D) amount of nickel used.

Question 31

Pure metals have physical and chemical properties more appropriate to dental applications than alloy metals.Some alloys are formed into restorations by casting.

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 32

The stress required to permanently distort an alloy is the:

A) strength.
B) yield strength.
C) hardness.
D) modulus.

Question 33

Noble alloys must have at least ____% noble metal content but have no stipulation for gold content.

A) 10
B) 15
C) 20
D) 25
E) 30

Question 34

The temperature at which the entire alloy freezes on cooling is the:

A) flow.
B) liquidus.
C) solidus.
D) viscosity.

Question 35

Dental alloys have a crystal structure like ice,salt,or sugar.These crystals,or _____ as they are called in metallurgy,can be seen clearly under a microscope.

A) granules
B) gradations
C) grains
D) lattice

Question 36

Which of the following is not considered a noble metal in dentistry?

A) Gold
B) Silver
C) Platinum
D) Palladium

Question 37

PGP wires are used for:

A) orthodontic wires.
B) endodontic files.
C) clasps in removable partial dentures.
D) substructures for fixed partial dentures.

Question 38

The temperature at which an alloy melts completely is its:

A) flow.
B) liquidus.
C) solidus.
D) viscosity.