Deck 11: Casting Alloys, Wrought Alloys, and Solders

Question 1

Which of the following statements is true about ceramics used in restorative dentistry?

A) The solidus of the alloy must be lower than the fusion temperature of the ceramic.
B) The solidus of the alloy must be higher 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

Answer 1

The solidus of the alloy must be higher than the fusion temperature of the ceramic.

Question 2

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

A) Bond direct composite to the metal substructure.
B) Refire new porcelain to the metal while the crown remains in the mouth.
C) Remove the crown, refire new porcelain to the metal, and then re-cement the crown.
D) Prevent debonding by selection of compatible alloys and ceramics and the proper manipulation of these materials during fabrication.

Answer 2

Refire new porcelain to the metal while the crown remains in the mouth.

Question 3

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.

Answer 3

A and C are true statements.

Question 4

An alloy liquidus is defined as the temperature at which ____________.

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

Question 5

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 6

Which of the following is a noble metal?

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

Question 7

What factors determine the definition of a noble metal?

A) Inability to be used in an alloy
B) Indistinct melting point
C) Resistance to corrosion
D) Lack of malleability

Question 8

How can greening of ceramic be avoided?

A) Select an appropriate alloy.
B) Periodic cleaning of the ceramic oven
C) Firing the restoration at the appropriate temperature
D) A, B, and C
E) Only A and C are correct.

Question 9

Define malleability.

A) The ability to be mechanically formed
B) The ability to be drawn into a wire
C) Corrosion resistance
D) Tarnish resistance

Question 10

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) 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 11

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

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

Question 12

Why is silver added to casting alloy?

A) Enhance bond strength
B) Prevent oxidation
C) Harden the gold
D) Prevent tarnish

Question 13

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 14

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 15

Which of the following is correct about palladium?

A) Is much harder than gold
B) Has poor corrosion resistance
C) Has a much lower melting point than gold
D) May be used in pure form for dental restorations
E) Both B and C

Question 16

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

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

Question 17

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 large 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 correct.
E) B and C are correct.

Question 18

Why is gold used in dental alloys?

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

Question 19

Of all the alloys, which alloys are the most difficult to cast and polish?

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

Question 20

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

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

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

Noble alloys must have at least 15% noble metal content. Noble content must include gold to be classified.

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 23

The ________ of an alloy is the mass in grams that occupies a volume of 1 cubic centimeter.

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

Question 24

A patient who is allergic to nickel might also be allergic to what other base metal?

A) Silver
B) Cobalt
C) Chromium
D) Aluminum

Question 25

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 26

High-density alloys are sold by ________ and cost _________ by ________ in any given volume of restoration.

A) grams; less; dose
B) mass; more; mass
C) mass; less; dose
D) grams; less; mass

Question 27

Which ADA class of casting alloy has the highest melting point?

A) High-noble
B) Noble
C) Base

Question 28

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

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

Question 29

The __________ is the temperature at which an alloy melts completely.

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

Question 30

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 31

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

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

Question 32

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

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

Question 33

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 34

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

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

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) gradations
B) granules
C) lattice
D) grains

Question 36

What are PGP wires used for?

A) Endodontic files
B) Orthodontic wires
C) Clasps in removable partial dentures
D) Substructures for fixed partial dentures

Question 37

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

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

Question 38

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

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

Question 39

When are solders used in dentistry?

A) Clasp wire to a partial denture framework
B) Orthodontic wire to a band in full treatment
C) Bond two units of a fixed partial denture together after each is cast separately.
D) A, B, and C
E) A and C

Question 40

The ____________ is the temperature at which the entire alloy freezes on cooling.

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

Question 41

Discuss the process of categorizing casting metals used in dentistry.

Question 42

Why are elements such as iron, gallium, iridium and tin added to the metal bases for a ceramic-faced crown?

A) Forms a surface oxide layer to bond to
B) Smooth surface to prevent irregularities in the ceramic
C) Decreases the thickness to allow for more ceramic build-up
D) Lowers the solidus of the metal so it is compatible with the ceramic temperatures

Question 43

Compare and contrast high-noble metals, noble metals, and base metals.