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BDS2: DM > Miscellaneous Properties of Composites > Flashcards

Miscellaneous Properties of Composites Flashcards

1
Q

Under what conditions do DHPT and camphorquinone react?

A

Only under the presence of BLUE LIGHT

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2
Q

What 2 general substances are needed during a light cure reaction?

A
  • Tertiary Amine

- Light Initiator

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3
Q

Explain how light can cause filling materials to set?

A
  • The tertiary amine reacts with the light initiator, under blue light, to form free radicals
  • Which then start off the addition polymerisation reaction
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4
Q

Advantages of light cured composites? 6

A
  • Single component system
  • Less decolouration
  • Minimal porosity (no paste mixing)
  • Virtually command set
  • Rapid polymerisation
  • Thin inhibited layer
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5
Q

Disadvantages of light cured composites? 3

A
  • Light sensitive during application (direct sunlight could start reaction)
  • Retina damage
  • Limited depth of cure
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6
Q

What does limited depth of cure of a dental composite mean?

A

Light can only cure 2mm of composite at a time.

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7
Q

what wavelength do composites cure between?

A

450-500nm

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8
Q

What is the maximum light output used for camphorquinone?

A

460-480nm

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9
Q

What are 4 things to consider when carrying out a light cure

A
  • Tip of light source must be close to surface of restoration
  • Light tip must not be contaminated
  • Must cure for manufacturers recommended time
  • Curing spots must overlap for large reaction
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10
Q

What can happen to light when it hits a composite? 3

A
  • Reflected
  • Scattered
  • Absorbed
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11
Q

Which shades of composites take longer to cure?

A

Darker Shades

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12
Q

What were the earlier light curing units based off? 2

A
  • UV light

- Benzoin Methyl Ether

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13
Q

What are modern light curing units based off?

A

Visible Light Activated - VLA

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14
Q

What is the most common light curing unit used today?

A

Quartz-Tungsten Halogen light curing unit

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15
Q

What is the filament used in a Quartz-Tungsetn light curing unit?

A

Tungsten Filament

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16
Q

What are some advantages of a LED light curing unit? 4

A
  • Low lateral heat production
  • Long lasting light source
  • Requires low voltage
  • Typically cordless
17
Q

How long does a Plasma-Arc (PAC) light curing unit take to cure?

A

Claims 1-3 Second cure

18
Q

What is a disadvantage of PAC light curing unit?

A

Very expensive bulbs

>$600

19
Q

What are the 3 main advantages of composites?

A
  • Good aesthetics
  • Less tooth tissue removed
  • Sets on command if light cured
20
Q

What 2 substances can be used as composite lining materials?

A
  • Calcium Hydroxide

- Glass Ionomer Cements

21
Q

What is the alternative for a Quartz-Tungsten Halogen light curing unit?

A

LED curing unit

22
Q

Which substance cannot be used as a composite lining material?

A

Eugenol based materials, as they inhibit setting

23
Q

What can shrinkage of a composite potentially lead to?

A

Rapid progression of caries at the margin

24
Q

What component causes a water uptake in composites?

A

Glass filler adsorbs water on its surface

25
Q

Which bond can be hydrolytically broke down by water in a composite?

A

Bond between resin and filler

26
Q

Where on the composite does staining most occur?

A

Margin between restoration and tooth

27
Q

What is the benefit of oxygen inhibition for composites?

A

Oxygen and resin interface results in a sticky resin surface which will allow placement of the next composite increment

28
Q

What features can be compromised by adsorbed water in composites? 2

A
  • Were resistance

- Colour stability (staining)

29
Q

How can you counteract the problem of a sticky composite surface? 3

A
  • Use a clear matrix strip then cure so oxygen doesn’t get through but light still does
  • Overfill and polish
  • Some clinicians apply bonding agent
30
Q

What are the advantages for silorane composites? 2

A
  • Low polymerisation shrinkage

- Low water absorption

31
Q

Why was silorane removed from the market? 2

A
  • High cost

- Requires alternative bonding agent

32
Q

What are some benefits of Bulk fill restorative composites? 4

A
  • One step placement
  • 5mm Depth of cure
  • Excellent sculptability
  • Availible in capsule or syringe delivery in 5 shades
33
Q

What are Class I restorations?

A

Restorations less than 4mm deep

34
Q

What are Class II restorations?

A

Restorations that are 5mm deep

35
Q

What are the setting times for Class I Bulk fill restorations?

A

20 seconds from occlusal surface

36
Q

What are the setting times for Class II Bulk fill restorations?

A

10 Seconds from each tooth surface

BDS2: DM (6 decks)

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