Miscellaneous Properties of Composites Flashcards
Under what conditions do DHPT and camphorquinone react?
Only under the presence of BLUE LIGHT
What 2 general substances are needed during a light cure reaction?
- Tertiary Amine
- Light Initiator
Explain how light can cause filling materials to set?
- The tertiary amine reacts with the light initiator, under blue light, to form free radicals
- Which then start off the addition polymerisation reaction
Advantages of light cured composites? 6
- Single component system
- Less decolouration
- Minimal porosity (no paste mixing)
- Virtually command set
- Rapid polymerisation
- Thin inhibited layer
Disadvantages of light cured composites? 3
- Light sensitive during application (direct sunlight could start reaction)
- Retina damage
- Limited depth of cure
What does limited depth of cure of a dental composite mean?
Light can only cure 2mm of composite at a time.
what wavelength do composites cure between?
450-500nm
What is the maximum light output used for camphorquinone?
460-480nm
What are 4 things to consider when carrying out a light cure
- 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
What can happen to light when it hits a composite? 3
- Reflected
- Scattered
- Absorbed
Which shades of composites take longer to cure?
Darker Shades
What were the earlier light curing units based off? 2
- UV light
- Benzoin Methyl Ether
What are modern light curing units based off?
Visible Light Activated - VLA
What is the most common light curing unit used today?
Quartz-Tungsten Halogen light curing unit
What is the filament used in a Quartz-Tungsetn light curing unit?
Tungsten Filament
What are some advantages of a LED light curing unit? 4
- Low lateral heat production
- Long lasting light source
- Requires low voltage
- Typically cordless
How long does a Plasma-Arc (PAC) light curing unit take to cure?
Claims 1-3 Second cure
What is a disadvantage of PAC light curing unit?
Very expensive bulbs
>$600
What are the 3 main advantages of composites?
- Good aesthetics
- Less tooth tissue removed
- Sets on command if light cured
What 2 substances can be used as composite lining materials?
- Calcium Hydroxide
- Glass Ionomer Cements
What is the alternative for a Quartz-Tungsten Halogen light curing unit?
LED curing unit
Which substance cannot be used as a composite lining material?
Eugenol based materials, as they inhibit setting
What can shrinkage of a composite potentially lead to?
Rapid progression of caries at the margin
What component causes a water uptake in composites?
Glass filler adsorbs water on its surface