Miscellaneous Properties of Composites

Question 1

Under what conditions do DHPT and camphorquinone react?

Answer 1

Only under the presence of BLUE LIGHT

Question 2

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

Answer 2

• Tertiary Amine

- Light Initiator

Question 3

Explain how light can cause filling materials to set?

Answer 3

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

Question 4

Advantages of light cured composites? 6

Answer 4

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

Question 5

Disadvantages of light cured composites? 3

Answer 5

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

Question 6

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

Answer 6

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

Question 7

what wavelength do composites cure between?

Answer 7

450-500nm

Question 8

What is the maximum light output used for camphorquinone?

Answer 8

460-480nm

Question 9

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

Answer 9

• 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

Question 10

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

Answer 10

• Reflected
• Scattered
• Absorbed

Question 11

Which shades of composites take longer to cure?

Answer 11

Darker Shades

Question 12

What were the earlier light curing units based off? 2

Answer 12

• UV light

- Benzoin Methyl Ether

Question 13

What are modern light curing units based off?

Answer 13

Visible Light Activated - VLA

Question 14

What is the most common light curing unit used today?

Answer 14

Quartz-Tungsten Halogen light curing unit

Question 15

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

Answer 15

Tungsten Filament

Question 16

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

Answer 16

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

Question 17

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

Answer 17

Claims 1-3 Second cure

Question 18

What is a disadvantage of PAC light curing unit?

Answer 18

Very expensive bulbs

>$600

Question 19

What are the 3 main advantages of composites?

Answer 19

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

Question 20

What 2 substances can be used as composite lining materials?

Answer 20

• Calcium Hydroxide

- Glass Ionomer Cements

Question 21

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

Answer 21

LED curing unit

Question 22

Which substance cannot be used as a composite lining material?

Answer 22

Eugenol based materials, as they inhibit setting

Question 23

What can shrinkage of a composite potentially lead to?

Answer 23

Rapid progression of caries at the margin

Question 24

What component causes a water uptake in composites?

Answer 24

Glass filler adsorbs water on its surface

Question 25

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

Answer 25

Bond between resin and filler

Question 26

Where on the composite does staining most occur?

Answer 26

Margin between restoration and tooth

Question 27

What is the benefit of oxygen inhibition for composites?

Answer 27

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

Question 28

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

Answer 28

- Were resistance | - Colour stability (staining)

Question 29

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

Answer 29

- 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

Question 30

What are the advantages for silorane composites? 2

Answer 30

- Low polymerisation shrinkage | - Low water absorption

Question 31

Why was silorane removed from the market? 2

Answer 31

- High cost | - Requires alternative bonding agent

Question 32

What are some benefits of Bulk fill restorative composites? 4

Answer 32

- One step placement - 5mm Depth of cure - Excellent sculptability - Availible in capsule or syringe delivery in 5 shades

Question 33

What are Class I restorations?

Answer 33

Restorations less than 4mm deep

Question 34

What are Class II restorations?

Answer 34

Restorations that are 5mm deep

Question 35

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

Answer 35

20 seconds from occlusal surface

Question 36

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

Answer 36

10 Seconds from each tooth surface