Deck 2: Properties of Materials

Question 1

For which of the following materials do dimensional changes occur during setting as a result of a chemical reaction?

A) Elastomeric impression materials
B) Gold restorations
C) Wax patterns
D) A and C
E) B and C

Answer 1

Elastomeric impression materials

Question 2

Given a schematic sketch of two opposing teeth, one with a temporary aluminum alloy crown and the other with a gold crown, which one would be the electrolyte?

A) Saliva
B) Gold crown
C) Difference in electrical potential
D) Temporary aluminum alloy crown

Answer 2

Saliva

Question 3

Which of the following terms indicates concentration of molecules at the surface of a solid or liquid?

A) Corrosion
B) Adsorption
C) Absorption
D) Hydrophilic

Answer 3

Adsorption

Question 4

With regard to wettability and water, what does a low contact angle indicate?

A) The material is hydrophilic.
B) The material is hydrophobic.
C) The contact angle is greater than 90°.
D) Both A and C are correct.
E) Both B and C are correct.

Question 5

What is used as a measurement of heat transfer?

A) Linear coefficient of thermal expansion
B) Thermal conductivity
C) Galvanism
D) Absorption
E) Adsorption

Question 6

Which of the following dental restorative materials has a linear coefficient of thermal expansion closest to teeth?

A) Unfilled acrylics and sealants
B) Glass ionomer base
C) Dental amalgam
D) Composites
E) Gold alloys

Question 7

Which of the following dental restorative materials has the greatest thermal conductivity?

A) Resin composites
B) Unfilled acrylics
C) Dental amalgam
D) Gold alloys
E) Ceramic

Question 8

Why are cavity varnishes and liners ineffective as thermal insulators?

A) Used in thin layers
B) High thermal conductivity
C) Low coefficient of thermal expansion
D) High coefficient of thermal expansion

Question 9

The volumetric dimensional change is equal to _____ times the linear dimensional change.

A) two
B) three
C) four
D) six

Question 10

Which of the following choices encourage good wetting?

A) Low-energy solid
B) High-energy solid
C) High-energy liquid
D) A and C are correct.
E) B and C are correct.

Question 11

What occurs as the result of a discrepancy between the linear thermal coefficient of expansion between teeth and the restorative material if there is no bonding?

A) Stress
B) Strain
C) Percolation
D) Yield strength
E) Elastic modulus

Question 12

Because the thermal expansion of a restorative material usually does not match that of the tooth structure, a differential expansion or contraction occurs that may result in leakage of oral fluids between the restoration and tooth.

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 13

Percolation is thought to decrease with time following insertion of which of the following dental restorative materials?

A) Filled resin composite
B) Unfilled acrylic resin
C) Dental amalgam
D) Cast gold
E) Ceramic

Question 14

Which of the following is an electrical property of interest in the mouth?

A) Coefficient of thermal expansion
B) Elastic modulus
C) Percolation
D) Galvanism
E) Ductility

Question 15

What refers to the uptake of liquid by a bulk solid?

A) Absorption
B) Adsorption
C) Hydrophilic
D) Hydrophobic

Question 16

A new addition silicone impression material is tested for linear dimensional change upon setting. The result of -0.34% indicates that _______________ took place within 24 hours after setting.

A) linear expansion
B) linear shrinkage
C) thermal expansion
D) thermal shrinkage

Question 17

How is the percentage of dimensional change measured?

A) An original length or volume
B) The final length or volume
C) The compressive strength
D) The tensile strength
E) The shear strength

Question 18

Which of the following dental materials has a thermal conductivity that is most similar to tooth structure?

A) Composites
B) Gold alloys
C) Dental amalgam
D) Zinc phosphate cement
E) Zinc oxide-eugenol cement

Question 19

Which of the following restorative materials has a linear thermal coefficient of expansion that is lower than that of human teeth?

A) Ceramics
B) Composites
C) Dental amalgam
D) Unfilled acrylics and sealants

Question 20

The thermal coefficient of expansion _____ uniform throughout the entire temperature range and is usually _________ for liquids than solids.

A) is; lower
B) is; higher
C) is not; lower
D) is not; higher

Question 21

For a given force, the _______ the area over which it is applied, the ________ the value of the stress.

A) smaller; smaller
B) smaller; larger
C) larger; larger
D) A and C
E) B and C

Question 22

Which of the following statements is true of the measure of Knoop hardness?

A) It is obtained by measurement of the short diagonal of an indentation from a diamond indenter.
B) Enamel has a lower Knoop hardness value than dentin and cementum.
C) Hardness is directly related to yield strength and wear resistance.
D) The larger the indentation, the smaller the value.

Question 23

What is the ratio of the force to the area called?

A) Stress
B) Strain
C) Tensile strength
D) Elastic modulus

Question 24

Analysis of the strain-time curve indicates that the ________ the time and the _____ force applied to the impression material, the lower the permanent strain and the more accurate the impression.

A) shorter; less
B) longer; less
C) shorter; more
D) longer; more

Question 25

Dimensional change may occur during setting as a result of which factor?

A) Volumetric change
B) Chemical reaction
C) Cooling
D) All of the above
E) B and C are correct.

Question 26

When a material reaches its ______________, deformation of a material becomes permanent.

A) stress-strain curve
B) ultimate strength
C) elastic modulus
D) yield strength

Question 27

How is the hardness of a dental material reported?

A) Knoop hardness
B) Nano-indentation
C) Diamond indenter
D) Dynamic properties

Question 28

Expansion and contraction rates between dental materials and tooth structure caused by temperature change vary. Gaps at the margins allow fluids to enter the space. What is this known as?

A) Coefficient of thermal expansion
B) Thermal conductivity
C) Dimensional change
D) Percolation

Question 29

Patients with dentures can apply about ____% of the force of those with normal dentition.

A) 10
B) 19
C) 50
D) 90
E) 150

Question 30

Which of the following statements is true of the tensile and compressive strengths of a material?

A) They may be significantly different.
B) Brittle materials are stronger in tension than in compression.
C) Brittle materials have small differences in tensile and compressive strength.
D) A, B, and C are true.
E) A and C are true.

Question 31

On which teeth are the greatest biting forces located?

A) Molars
B) Canines
C) Incisors
D) Premolars

Question 32

Which of the following statements is true of the proportional limit?

A) Below the proportional limit a material is plastic, and above the proportional limit it is elastic.
B) Below the proportional limit a material is elastic, and above the proportional limit it is plastic.
C) A material is elastic both below and above the proportional limit.
D) A material is plastic both below and above the proportional limit.

Question 33

"Measures the energy required to fracture a material" is the definition of which term?

A) Ductility
B) Resilience
C) Toughness
D) Malleability

Question 34

Which term refers to the change in the length or deformation of a material when subjected to force?

A) Flexure
B) Tensile
C) Strain
D) Shear

Question 35

Which of the following is not a form of stress?

A) Compressive
B) Flexure
C) Strain
D) Shear

Question 36

Of the following materials, which has the closest coefficient of expansion to tooth structure?

A) Ceramic
B) Amalgam
C) Filled polymers
D) Composite resins

Question 37

Which of the following materials has the highest rating related to thermal conductivity?

A) Glass ionomer
B) Gold alloy
C) Enamel
D) Dentin

Question 38

Which term refers to the cause of a metallic taste in the mouth?

A) Corrosion
B) Galvanism
C) Percolation
D) Contamination

Question 39

What causes corrosion?

A) Contact of two dissimilar metals in the mouth
B) Poor oral hygiene around restorations
C) Acidic food and drink
D) A and C are correct.

Question 40

What is a material called if a liquid presents a contact angle of wettability greater than 90°?

A) Viscous
B) Thixotropic
C) Hydrophilic
D) Hydrophobic

Question 41

Compare and contrast the terms absorption and adsorption.

Question 42

Explain the difference between ductility and malleability.

Question 43

What is the energy it takes to deform a material called?

A) Relationship
B) Resistance
C) Resilience
D) Rebound

Question 44

Detail the significance of thermal dimensional change.

Question 45

What is the purpose of using dental cements as bases within a cavity preparation?

Question 46

Compare and contrast the processes of tarnish and corrosion.

Question 47

What is the energy necessary to fracture called?

A) Yield strength
B) Toughness
C) Stress
D) Strain