Structure And Properties Of Dental Materials

Front 1

1. To understand the proper use of a dental material, it is necessary to be familiar with its__ and ____ properties.

Back 1

Physical and Chemical

Front 2

2. List at least 3 questions that a dentist may ask when determining which dental alloy to use in a restoration.

Back 2

(What is its strength?);
(How far can it be bent without permanent distortion?)
(How hard is it? [giggaty])
(Will it discolor?)

Front 3

3. The mechanical and physical properties of any material depend on:
a. chemical makeup
b. internal structure
c. humidity
d. malleability

Back 3

B

Front 4

4. T or F:
_____The three states of matter are gas, solid, and liquid.

Back 4

True

Front 5

6. A _______________ state of matter will occupy a definite volume of space and whose shape does
not depend on a container.

Back 5

Solid

Front 6

7. If an objet feels hard and unyielding, one concludes that it is:
a. amorphous
b. a solid
c. amorphous plasma
d. compressed gas > 3000psi

Back 6

B

Front 7

8. There are _______ possible types of space lattices.
a. 4 b. 5 c. 14 d. 13

Back 7

C

Front 8

9. The ultimate structure of gold is composed of a repeated pattern of individual
_______________________ each one oriented in a definite threedimensional
relationship with the others.

Back 8

space lattices (tell me that doesn’t sound like something off the menu
of that one Asteroid Diner in “Space Balls”…)

Front 9

10. T or F:
_____Most crystalline materials used in dentistry form a rhombic spacelattice.

Back 9

FALSE (They have a cubic form)

Front 10

11. T or F:
_____ All solid materials are considered to be rigid.

Back 10

True

Front 11

12. T or F
:_____ If a material possesses rigidity, it usually can be described as crystalline.

Back 11

True

Front 12

13. The atoms in a space lattice tend to maintain their position relative to one another –
their:
a. interatomic distance
b. interatomic proximity
c. interatomic resilience
d. intraatomic distance

Back 12

A

Front 13

14. Jeopardy Question: “This is the distance at which the force of attraction between atoms is equal to the force that repels them.”

Back 13

“What is equilibrium?” or “What is normal interatomic distance?”

Front 14

15. T or F:
_____ Crystalline materials resist forces that either compress or stretch the space lattice.

Back 14

True

Front 15

16. Some apparently solid materials posses a structure in which the molecules tend to be
arranged at random, similar to the molecules in a liquid. Such a material is said to be:

Back 15

amorphous

Front 16

17. T or F:
_____ Amorphous literally means “modified form”.

Back 16

FALSE (it means “without form”)

Front 17

18. One example of an amorphous material would be:
a. rock
b. glass
c. cornstarch and water
d. diamond

Back 17

B

Front 18

19. T or F:
_____ Overtime, glass will actually “flow”, so it is not strictly speaking, a solid.

Back 18

True

Front 19

20. T or F:
_____ Flow is only a characteristic of amorphous solids

Back 19

FALSE (it is also a characteristic of liquids)

Front 20

21. T or F:
_____ Amorphous structures may flow under certain conditions.

Back 20

True

Front 21

21. T or F:_
____ Amorphous structures may flow under certain conditions.

Back 21

True

Front 22

23. T or F:
_____ The properties of all solid materials are intimately related to their atomic
structures.

Back 22

True

Front 23

24. There are essentially _____ ways of attaching solid structures together.
a. 2 b. 4 c. 6 d. 8

Back 23

A

Front 24

25. List the two ways solid structures can be attached to one another.

Back 24

mechanical mechanisms, the phenomenon of adhesion

Front 25

26. Strong attachments can be accomplished by mechanical bonding, or:
a. relief b. refraction c. retention d. retraction

Back 25

C

Front 26

27. Give any example of “mechanical retention”:

Back 26

Two pieces of wood being held together by a screw, nail, bolt etc.

Front 27

28. T or F:
____ An example of the adhesion phenomenon would be: “Two pieces of wood that
are joined and bonded with glue.”

Back 27

FALSE (This example is just a finer form of Mechanical bonding. The glue
penetrates small surface irregularities of the surface. When the glue hardens, the
multitude of the projections that are embedded in the surface provide “fingers” for
mechanical attachment and retention)

Front 28

29. T or F:
_____ The acid etch technique produces minute pores in a surface, making it easier for resin to provide mechanical retention.

Back 28

True

Front 29

30. Jeopardy Question: “This force causes unlike atoms or molecules to attach to eachother.”

Back 29

What is Adhesion?”

Front 30

31. The substance to which an adhesive is applied is called:
a. the adhessor
b. the adhesee
c. the adheror
d. the adherend

Back 30

D

Front 31

32. T or F
:_____ Tooth structure is the adherend to whoch plaque attaches.

Back 31

True

Front 32

33. The point at which an adhesive is in contact with the adherend is referred to as the:
a. interpoint
b. intercourse
c. interface
d. interproximal

Back 32

C

Front 33

34. The act of attaching like atoms or molecules to one another is called:
a. adhesion
b. prohesion
c. exhesion
d. cohesion

Back 33

D

Front 34

35. T or F:
_____ The strength of a material is governed by the cohesive forces of attraction between its atoms or molecules

Back 34

True

Front 35

36. Adhesion may involve attractions that are essentially___________________, or the
bonding may be ________.

Back 35

strong physical forces ; chemical

Front 36

37. JEOPARDY QUESTION: “Known to be quite strong, this type of chemical bond between
atoms or molecules of adhesives and adherends is the most desirable for achieving adhesion.”

Back 36

“What is a primary bond?”

Front 37

38. An example of a primary bond would be:
a. 2 wood pieces held together with wood glue
b. a galvanized plumbing pipe bolted to a copper one.
c. a dyed fabric or cloth.
d. melted wax on die stone surface.

Back 37

C

Front 38

38. An example of a primary bond would be:
a. 2 wood pieces held together with wood glue
b. a galvanized plumbing pipe bolted to a copper one.
c. a dyed fabric or cloth.
d. melted wax on die stone surface.

Back 38

D

Front 39

40. The most common type of adhesion involves physical forces, or ______.

Back 39

secondary bonds

Front 40

41. Adhesion involving physical forces or secondary bonds is called:
a. van der Waals forces
b. wan der Vaal forces
c. Won der wall forces
d. Van der Kamp forces

Back 40

A

Front 41

42. T or F:_
____ Van der Waals forces provide a much stronger bond than a when a chemical
union occurs.

Back 41

FALSE (Chemical unions are far stronger)

Front 42

43. T or F:
_____ The use of paint or glue involves Van der Waals forces.

Back 42

True

Front 43

44. T or F:
_____ for either chemical or physical adhesion to occur, the adhesive and adherend
must be in intimate contact.

Back 43

True

Front 44

45. In your own words, the term “wetting” as it applies to adhesion is best described as:

Back 44

(something to the effect of): Applying liquid adhesive to an adherend, with the idea that the adhesive will flow over the adherend, so the two substances to
be joined together will be brought into intimate contact……in layman’s terms… “spreading a bunch of glue onto something so it will stick better.”

Front 45

46. T or F:
_____ The better an adhesive flows over and wets the surface of the adherend, the more likely it is that adhesion will occur between the two.

Back 45

True

Front 46

47. A ____ is the angle formed when a drop of adhesive is is placed on the surface of an adherend.

Back 46

contact angle

Front 47

48. If the molecules of an adhesive are not attracted to the surface of an adherend, the adhesive will _____

Back 47

form a ball

Front 48

49. If there is strong attraction between the molecules of an adhesive and adherend, the
adhesive will

Back 48

flow readily over the surface of the adherend.

Front 49

50. The ideal adhesive spreads out to such a film that the contact angle will be:
a. 0° b. 15‐30° c. 45° d. 90°

Back 49

A

Front 50

51. One of the most important factors that influences an adhesive’s flow over an adherend is
called:
a. the surface tension
b. the surface friction
c. the surface differential
d. the surface energy

Back 50

D

Front 51

52. T or F:
_____ The following describes an object with “high” surface energy: “If the atoms on
the surface are eager to attract other atoms to them, then it is relatively easy to find adhesives that will bond to that surface.”

Back 51

True

Front 52

53. T or F:
____ Most metals have a high surface energy and, therefore are relatively easy to wet with a suitable adhesive.

Back 52

True

Front 53

54. A common substance with very low surface energy that is used to prevent substances from
sticking to a surface is _______________________

Back 53

Teflon.

Front 54

55. T or F:
_____ The surface energy of metallic restoratives is higher than that of tooth enamel.

Back 54

True

Front 55

56. T or F:
_____ Marginal caries around dental restorations can be partially attributed to the fact that the surface energy of metallic restoratives is higher than that of tooth enamel.

Back 55

True

Front 56

57. Fluoridetreated
teeth may stay cleaner longer because:
a. fluoride kills plaque and neutralizes acid
b. fluoride reduces the wettability of tooth enamel surfaces, making it harder for plaque to stick.
c. fluoride hardens and strengthens tooth enamel
d. fluoride increases the amount of “good” bacteria in the mouth, which in turn “eat” the bad
bacteria.
e. it’s all a government plot for mind control….we MUST obey the ADA….obey…..obey

Back 56

B (… and just maybe D … The truth is out there.)

Front 57

58. Enamel and dentin are______ in composition.

Back 57

inhomogenous

Front 58

59. T or F:
_____ Few of the conditions essential for adhesion are present in the oral cavity.

Back 58

True

Front 59

60. T or F
:_____ Enamel and dentin are part organic, and part inorganic in composition

Back 59

True

Front 60

61. T or F:
_____ Because a microscopic, singlemoleculethick
layer of water is always present on the tooth’s surface, adhesives are prevented from coming into intimate contact with a tooth.

Back 60

True

Front 61

62. T or F:_____Surface moisture on teeth can be easily removed by dehydrating the teeth
surfaces, after which adhesives can be easily used.

Back 61

FALSE (Surface moisture is impossible to remove by dehydration without the use of temperatures or agents that could cause serious injury to the pulp.)

Front 62

63. JEOPARDY QUESTION: “Unless an adhesive exhibits this low contact angle behavior, it will not even wet the watercovered
surface of a tooth.”

Back 62

“What is hydrophilic behavior?”

Front 63

64. _____ is defined as any push or pull on an object and is measured in units of__ or pounds.

Back 63

Force ; Newtons

Front 64

65. T or F:_
____ Dental restorations are constantly subjected to forces of various types, such as those of biting and chewing.

Back 64

True

Front 65

66. The reaction with which an object resists an external force is called:
a. Strain
b. Stress
c. Steer
d. Stream

Back 65

B

Front 66

67. T or F:
_____Force can be measured in newtons or pounds, but the concept is meaningless unless it is known where the force is applied and the direction in which it is acting.

Back 66

True

Front 67

68. T or F:
_____ “Load” is the direction upward or opposite to an applied force.

Back 67

True

Front 68

69. T or F:
_____ The internal force of an object in resisting an applied force or load is called “Strain”.

Back 68

FALSE (it is called “Stress”)

Front 69

70. T or F:_
____ A “stress” is a force, but it is inside the structure or body on which the load is
acting.

Back 69

True

Front 70

71. When a force acts on a solid object, it’s atoms or molecules are slightly displaced from their equilibrium ______, causing interatomic forces to resist this displacement.

Back 70

interatomic spacing.

Front 71

72. The amount of deformation or change in shape of an object is called the:
a. stress
b. strain
c. stretch
d. pull

Back 71

B

Front 72

73. T or F:
_____ When load produces a stress in a structure, it also causes strain.

Back 72

True

Front 73

74. There are ______ types of stress.

Back 73

3

Front 74

75.The three types of stress are ____, and____.

Back 74

Tensile; Compressive; Shear

Front 75

76. Match the Type of stress with its definition.
a. Tensile Stress i. is a stress that opposes a load that compresses structure
b. Shear Stress ii. Results from a load that tends to elongate a structure
c. Compressive Stress iii. is induced when a structure is rotated, twisted or deformed by sliding one part parallel to another

Back 75

Aii);
(Biii);
(Ci)

Front 76

77. T or F:
_____ It is virtually impossible to induce only one type of stress in a structure.

Back 76

True

Front 77

78. ______is the property of a body that permits it to be deformed by an applied load and then assume its original shape when the load is removed.

Back 77

Elasticity

Front 78

79. A substance is said to be ___or _ __when it is deformed, and remains so after the load is removed.

Back 78

inelastic ; plastic

Front 79

80. At stresses that exceed the ________ proportional limit, the structure will not return to its original shape when the external force is removed.

Back 79

proportional limit.

Front 80

81. T or F:_
_____ Yield point and yield strength are used in the same connections as the term
“proportional limit”.

Back 80

True

Front 81

82. The property that defines the rigidity of a material under stresses below the elastic limit is
called:
a. modus of elasticity
b. modulus of elasticity
c. modular elasticity
d. modicus of elasticity

Back 81

B

Front 82

83. T or F:_
____ “Modulus” means a positive number that represents a measurement of elasticity – physics

Back 82

True

Front 83

84. T or F:_____ A material with a low proportional limit is desirable in fixed partial denture
applications, or any dental restoration or appliance subject to masticatory forces.

Back 83

FALSE (Not a low, but high proportional limit).