Deck 2: Properties of Materials

Question 1

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

Answer 1

linear shrinkage

Question 2

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

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

Answer 2

Galvanism

Question 3

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

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

Answer 3

Elastomeric impression materials

Question 4

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

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

Question 5

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

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

Question 6

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

A) temporary aluminum alloy crown.
B) gold crown.
C) saliva.
D) difference in electrical potential.

Question 7

Cavity varnishes and liners are ineffective as thermal insulators because they:

A) have high thermal conductivity.
B) have a high coefficient of thermal expansion.
C) have a low coefficient of thermal expansion.
D) are used in thin layers.

Question 8

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

Question 9

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) Cast gold
D) Dental amalgam
E) Ceramic

Question 10

Dimensional change usually is expressed as a percentage of:

A) the compressive strength.
B) the shear strength.
C) the tensile strength.
D) an original length or volume.
E) the final length or volume.

Question 11

_____ is used as a measure of heat transferred.

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

Question 12

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 13

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

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

Question 14

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

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

Question 15

With regard to wettability and water,a low contact angle indicates:

A) the material is hydrophilic.
B) the material is hydrophobic.
C) the contact angle is greater than 90°.
D) both A and C.
E) both B and C.

Question 16

_____ 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) Elastic modulus
D) Percolation
E) Yield strength

Question 17

_____ refers to the uptake of liquid by a bulk solid.

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

Question 18

Which of the following restorative materials have thermal conductivity that is most similar to tooth structure?

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

Question 19

Which of the following choices encourage good wetting?

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

Question 20

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

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

Question 21

If a liquid presents a contact angle of wettability greater than 90°,the material is said to be:

A) thixotropic.
B) hydrophilic.
C) hydrophobic.
D) viscous.

Question 22

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 23

The greatest biting forces are on:

A) molars.
B) bicuspids.
C) cuspids.
D) incisors.

Question 24

The energy required to fracture a material is a measure of its:

A) resilience.
B) toughness.
C) ductility.
D) malleability.

Question 25

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 26

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.This is known as:

A) coefficient of thermal expansion.
B) thermal conductivity.
C) dimensional change.
D) percolation.

Question 27

Dimensional change may occur during setting as a result of:

A) chemical reaction.
B) volumetric change.
C) cooling.
D) all of the above.
E) only A and C.

Question 28

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

Question 29

Corrosion is the result of:

A) contact of two dissimilar metals in the mouth.
B) poor oral hygiene around restorations.
C) acidic food and drink.
D) A and C only.

Question 30

The change in the length or deformation of a material when subjected to force is:

A) flexure.
B) strain.
C) shear.
D) tensile.

Question 31

A metallic taste in the mouth may be a result of:

A) galvanism.
B) corrosion.
C) contamination.
D) percolation.

Question 32

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 33

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

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

Question 34

The ratio of the force to the area is called:

A) stress.
B) strain.
C) elastic modulus.
D) tensile strength.

Question 35

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 36

The hardness of a dental material is reported in:

A) Knoop hardness.
B) nano-indentation.
C) diamond indenter.
D) dynamic properties.

Question 37

Deformation of a material becomes permanent when the material reaches its:

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

Question 38

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

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

Question 39

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

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

Question 40

Which of the following is not a form of stress?

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

Question 41

Compare and contrast the terms absorption and adsorption.

Question 42

Explain the difference between ductility and malleability.

Question 43

Detail the significance of thermal dimensional change.