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BDS2 CDS DMS > 5. Composite Resins: Part 2 > Flashcards

5. Composite Resins: Part 2 Flashcards

1
Q

Properties that affect the choice of material (10)

A 
Mechanical
Bonding
Thermal
Aesthetic
Handling/viscosity
Surface finish
Polymerisation shrinkage
Anticariogenic
Biocompatible
Radiopacity
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2
Q

Clinical requirements of large posterior cavity (3)

A

High strength
High rigidity
High abrasion resistance

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3
Q

Clinical requirements of deciduous restoration (4)

A

Strong in thin section
Wear of tooth
Bonding
Microleakage

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4
Q

Types of composite (3)

A

Conventional
Microfine
Hybrid

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5
Q

Features of conventional composite (2)

A

Strong

Problems with finishing and staining due to soft resins and hard particles

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6
Q

Features of microfine composite (3)

A

Smaller particles
Allows for smoother surfaces (better aesthetics for longer periods)
Inferior mechanical properties (elastic limit and rigidity)

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7
Q

Features of hybrid composites (2)

A

Compromise between conventional and microfine composites

Improved filler loading and coupling agents cause improvement in mechanical properties

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8
Q

Definition of hardness (3)

A

Resistance to scratching or indentation resistance
Related to material surface
Measured by the amount of surface indentation (KHN)

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9
Q

Definition of abrasion (2)

A

Abrasion occurs when the tooth grinds/slides along the opposing tooth surface (or restorative material at its surface
Abrasion leaves behind a rough surface

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10
Q

What does surface roughness affect (3)

A

Appearance
Plaque retention
Sensation when in contact with tongue (laceration)

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11
Q

Process of tooth wear of composite resins (4)

A

Resin is removed
Leaves some of the filler particle exposed
If enough resin is removed, the filler particle is dislodged, leaving a “cut” out of the resin
Process continues

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12
Q

Factors that affect tooth wear (2)

A

Material factors

Clinical factors

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13
Q

Material factors that affect tooth wear (5)

A 
Filler material
Filler size distribution
Filler loading
Resin formulation
Coupling agents
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14
Q

Clinical factors that affect tooth wear (7)

A 
Cavity size
Cavity design
Tooth position
Occlusion
Placement technique
Cure efficiency
Finishing methods
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15
Q

Features of material/tooth bonding (2)

A

Bonding to enamel occurs through acid etch technique

Bonding to dentine occurs through dentine/universal bonding agents (DBAs)

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16
Q

Typical bonding strength of composite to enamel/dentine

A

40MPa

Dependent on the surface preparation of tissue, composite brand and test method

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17
Q

Function of good material/tooth surface bonding (3)

A

Help reduce microleakage
Help to counteract polymerisation shrinkage
Help to reduce the likelihood of a gap between the restoration and tooth

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18
Q

Features of composite restoration placement (2)

A

Will not have to withstand full stress - the stress will be transferred to tooth and bone
Poor bonding to tooth concentrates stress on the restoration, so failure is more likely

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19
Q

Compressive strength of enamel

A

250MPa

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20
Q

Compressive strength of dentine

A

280MPa

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21
Q

Compressive strength of amalgam

A

350MPa

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22
Q

Compressive strength of (hybrid) composite

A

300MPa

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23
Q

Compressive strength of microfilmed composite

A

260MPa

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24
Q

Compressive strength relationship between materials (4)

A

Amalgam > composite > dentine > enamel

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25
Q

Elastic limit (Yield) stress of (hybrid) composite

A

300MPa

26
Q

Elastic limit (Yield) stress of microfilled composite

A

160MPa

27
Q

Tensile strength of enamel

A

35MPa

28
Q

Tensile strength of dentine

A

40-260MPa

29
Q

Tensile strength of amalgam

A

60MPa

30
Q

Tensile strength of (hybrid) composite

A

50MPa

31
Q

Tensile strength of microfilled composite

A

40MPa

32
Q

Tensile strength relationship between materials (4)

A

Dentine > amalgam > composite > enamel

33
Q

Flexural strength of (hybrid) composite

A

150MPa

34
Q

Flexural strength of microfilled composite

A

80MPa

35
Q

Elastic modulus of enamel

A

50GPa

36
Q

Elastic modulus of dentine

A

12GPa

37
Q

Elastic modulus of amalgam

A

30GPa

38
Q

Elastic modulus of (hybrid) composite

A

14GPa

39
Q

Elastic modulus of microfilled composite

A

6GPa

40
Q

Elastic modulus relationship between materials (4)

A

Enamel > amalgam > composite > dentine

41
Q

Hardness of enamel

A

350VHN

42
Q

Hardness of dentine

A

60VHN

43
Q

Hardness of amalgam

A

100VHN

44
Q

Hardness of (hybrid) composite

A

90VHN

45
Q

Hardness of microfilled composite

A

30VHN

46
Q

Hardness relationship between materials (4)

A

Enamel > amalgam > composite > dentine

47
Q

Thermal properties include (2)

A

Thermal conductivity

Thermal expansion coefficient

48
Q

Ideal thermal properties of composite

A

Thermal conductivity should be low to avoid pulpal damage from hot and cold foods/fluids
Thermal expansion should be equal to that of the tooth, to reduce microleakage

49
Q

Actual thermal properties of composite

A

Low thermal conductivity

High thermal expansion coefficient

50
Q

Thermal expansion coefficient of enamel

A

11ppm/C

51
Q

Thermal expansion coefficient of dentine

A

8ppm/C

52
Q

Thermal expansion coefficient of amalgam

A

22-28ppm/C

53
Q

Thermal expansion coefficient of composite

A

25-68ppm/C

54
Q

Thermal expansion coefficient of GIC

A

10-11ppm/C

55
Q

Thermal expansion coefficient of ceramic

A

8-14ppm/C

56
Q

Thermal expansion coefficient of gold alloy

A

12-15ppm/C

57
Q

Thermal expansion relationship between materials (7)

A

Composite > amalgam > gold alloy > ceramic > enamel = GIC > dentine

58
Q

Components of aesthetic properties (5)

A 
Shade range
Translucency
Maintenance of properties over lifetime
Resistance to staining
Surface finishing
59
Q

Why should composite restorations be radiopaque

A

To allow secondary caries to be diagnosed more easily on radiographs

60
Q

Handling/viscosity properties of composite (4)

A

Light-curing
Mixing/working times
Viscosity
User-friendly

61
Q

Composite setting shrinkage

A

Low

Polymerisation shrinkage is still a problem as stresses develop at hard tissue surfaces, making de-bonding more likely

62
Q

Bonding occurs between (2)

A

Filler and resin particles

Resin and hard tissues

BDS2 CDS DMS (15 decks)

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