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Direct Restoration > Lecture 6 Reading > Flashcards

Lecture 6 Reading Flashcards

1
Q

Why can the walls of a preparation for bonded resin composite diverge ?

A

Because the restoration would be bonded to the enamel and dentin

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2
Q

Problems associated with using resin composite in posterior restorations:

A

shrinkage, postop sensitivity, poor resistance to wear (especially if functional cusps) and restoration fractures

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3
Q

AFR stands for:

A

annual failure rate

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4
Q

How much greater is the risk for secondary caries for resin composite restorations than amalgam?

A

3.5 times

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5
Q

Long term success of poster resin composites restorations depends upon:

A

cavity size, restoration type, functional/occlusal stresses, patient risk status, and tooth type

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6
Q

How does the composition of visivle light-cured resin composites compare to that of auto cured systems?

A

lss amine content

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7
Q

What does less amine content in VLCs compared to auto cured systems result in?

A

less yellowing and greater color stability over time

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8
Q

Which resin composites systems has the smoothest surface finish of all systems?

A

microfilled resin composites

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9
Q

How do microfilled resin composites maintain their esthetic better than other types of composites?

A

through enhanced resistance to surface staining

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10
Q

How does the preparation for a resin composite restorations differ from Black’s amalgam preparation?

A

shallower, narrower outline form allowing for less occlusal contact on the restoration, decreased shrikinage because it is less bulky, rounded internal line angles which decreases the stress concentration associated with sharp line angles, enhancing resin adaptation, no “extension for prevention”

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11
Q

Why can a resin composite restorations preparation be shallower than Black’s amalgam preparation?

A

retention is provided by bonding to tooth structure and not mechanical undercuts, no need to penetrate dentin if the caries lesion does not. This expands the area of enamel available for bonding

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12
Q

True or False? Extending the Class 2 preparation through the occlusal fissure makes the restoration more resistant to fracture than a proximal slot restoration.

A

F.

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13
Q

True or False? Bonded posterior restorations can be relied upon to provide long-term reinforcement of tooth structure.

A

F

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14
Q

Major benefit to having radiopaque restorative materials

A

detection of voids and recurrent caries lesions better when radiopacity is equal to or greater than that of enamel

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15
Q

Reasons why radiopaque materials are necessary:

A

evalutate the contours and marginal adaption, to distinguish among the restoration,

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16
Q

What does the ADA require in terms of radiopacity of restorative materials?

A

greater than that of an equal thickness of aluminum (approximately equal to dentin)

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17
Q

What is required for mercury removal as waste?

A

expensive separator systems to remove mercury from the wastewater

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18
Q

Volumetric shrinkage of modern resin composites upon polymerization:

A

1.5% to 5%

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19
Q

From which margins are restorative materials most likely to pull away from during polymerization?

A

least retentive margins, usually those with the least enamel

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20
Q

What type of force develops in the enamel margins?

A

tensile force, resulting in marginal degradation, enamel cracks, and craze lines

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21
Q

Toward which wall does shrinkage occur toward?

A

the walls of cavity preparations to which it is bonded most strongly, regardless of the initiator mode

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22
Q

How does incremental placement of resin composites decrease the effect of setting contraction upon polymerization?

A

by reducing the bulk of resin composites cured at a time AND the reduction of the ratio of bonded to unbonded surface area (C-factor) to relieve stress between the tooth and resin composite

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23
Q

Why are auto cured resin composites sometime recommended for posterior restorations?

A

induce less polymerization stress than VLC composite, greater porosity incorporated into the auto cured resin composite as a result of mixing.

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24
Q

What inhibits the set of resin immediately adjacent to voids and decreases the C-factor in auto cured resin composites?

A

the incorporated oxygen, void increase the free surface area for stress compensation by flow of the resin during the setting reaction

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25
Q

Why do autocured resin composites develop shrinkage stress more slowly than VLC materials?

A

because of slower polymerization rate

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26
Q

What does a slower polymerization rate allow for with autocured resin compostites?

A

increased restorative flow during polymerization

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27
Q

How can the rate of polymerization of VLC resin composite be decreased?

A

by crying the intensity of the curing light.

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28
Q

form of curing for VLC resin composites:

A

two-step or soft-start polymerization

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29
Q

Benefit to slow initial cure followed by high-level irradiance:

A

enhancement of marginal integrity

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30
Q

True or False? Mechanical properties of VLC resin composites are adversely affected with a reduced initial irradiance followed by a high-intensity irradiance.

A

F

31
Q

Why might the creation of resin material with zero shrinkage be a bad thing?

A

composites are based on polymers that absorb small amounts of water, leading to expansion that may apply pressure to the cavity walls

32
Q

What allows for ingress of cariogenic bacteria?

A

marginal gap formation at the gingival margin

33
Q

Will marginal degradation increase with time?

A

yes

34
Q

True or False? S. mutans levels are significantly higher in the plaque adjacent to proximal surfaces of posterior resin composite restorations than next to amalgam or glass ionomer restorations.

A

T

35
Q

How do organic acids of plaque effect bis-GMA polymers?

A

soften the polymers (possible effect on wear and staining)

36
Q

True or False? There is a greater need for greater recall and close follow-up of patients with posterior resin composites

A

T

37
Q

What has led to the decrease in reports of post-overproduction sensitivity in patients with posterior resin composites?

A

improvements in dentin adhesives, clinician more proficient in case selection and clinical techniques

38
Q

Most accepted guess for why post-op sensitivity occurs with posterior resin composites:

A

polymerization shrinkage

39
Q

What can cause plural inflammation and tooth sensitivity?

A

bacterial entry into dentinal tubules

40
Q

True or False? Gap formation allows a low continuos fluid flow into the dentinal tubules.

A

F. dentinal fluid flows from the pulp through the tubules to the gap

41
Q

What can cause a sudden rapid outflow of tune;around fluid that stimulates the nerve surrounding the odontoblastic process?

A

Cold or other stimuli that cause contraction of fluid in the gap

42
Q

This can result in cusp deformation:

A

contraction forces of polymerization

43
Q

Flexure of resin composite under an occlusal load may cause this type of pressure in the tubular fluid to be transmitted to the odontoblastic process:

A

hydraulic pressure

44
Q

Patients that experience post operative sensitivity within 1 month of posterior resin composite restoration placement are about ____ as likely to have that restoration fail within 5 years.

A

twice

45
Q

Why does resin composites wear occur?

A

chemical damage and mechanical break down

46
Q

Wear of resin composites occurs by these 2 mechanisms:

A

abrasion and attrition

47
Q

This is generalized wear that occurs across the entire occlusal surface;

A

abrasion, abrasive action of particles during mastication, occurs in all areas of the restoration

48
Q

This is the loss of restoration material due to direct contact with opposing tooth surfaces:

A

attrition

49
Q

Wear can be related to either of these 2 factors:

A

material or clinical factors

50
Q

on which areas of the tooth does attrition occur?

A

Occlusal contacts

51
Q

First step in attrition:

A

cracks in the resin matrix from occlusal stress that will coalesce and lead to the loss of resin composite material from the surface

52
Q

Material factors of wear are related to:

A

Content, size, and distribution of the resin composite’s filler particles

53
Q

Which exhibit unacceptable wear, heavily filled composites or less-heavily filled composites?

A

less heavily filled

54
Q

True or False? Generally, higher filler contact composites are more subject to attrition and marginal break down, especially adjacent tooth structure.

A

F. lower filler content, microfilled

55
Q

Why are lower filler content resins more resistant to abrasion?

A

because of their smoother surfaces, decreased inter particle spacing and lowered coefficient of friction.

56
Q

Which are more resistant to attrition, heavily filled or less heavily filled hybrid resin composites?

A

heavily filled

57
Q

Which have higher abrasion wear, composites with larger or smaller mean particle size?

A

larger, wear happens more between the fillers, they will get loose and be lost from the matrix

58
Q

The rate of wear varies with:

A

particle size

59
Q

How do composites with larger filler particles wear?

A

more rapid initial but slower wear over time

60
Q

Clinically relevant wear factors:

A

size and location of restoration, occlusal load, and how well it was cured

61
Q

True or False? As the surface area and length of cavosurface margins increase, so does the exposure to occlusal forces, with a resultant increase in wear.

A

T

62
Q

Does fracture resistance increase or decrease as a result of fatigue from chewing?

A

decreases

63
Q

What type of wear are proximal surfaces subjected to?

A

abrasion

64
Q

Is proximal surface wear greater on posterior resin composites or enamel proximal surfaces?

A

posterior resin composites

65
Q

How is the longevity of a restoration related to the mechanical properties of the restorative material?

A

the more closely the mechanical properties of a restorative material simulate those of enamel and dentin, the better the longevity

66
Q

Is the fracture toughness of resin composite materials higher or lower than metallic restorative materials?

A

lower

67
Q

How can the fracture toughness of a restoration material be increased?

A

increased filler loading

68
Q

Does resin composite have a high or low degree of elastic deformation?

A

high, 6-8 times that of amalgam

69
Q

Does resin composite have a high or low modulus of elasticity?

A

low

70
Q

The higher the filler content, the less/more the elastic deformation:

A

less

71
Q

Is the coefficient of thermal expansion of resin composite higher or lower than that of tooth strcuture?

A

higher

72
Q

How is marginal leakage affected by the thermal expansion properties of tooth structure and resin composite?

A

the greater the mismatch, the greater the likelihood of marginal leakage

73
Q

How is filler content associated with thermal expansion properties of tooth structure and resin composites?

A

increase filler content, decrease mismatch of thermal expansion properties

Direct Restoration (23 decks)

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