Polymerization & Curing Lights Flashcards
What does a photo-initiator in resin do?
- Absorbs photon energy
- Combines with activator (amine)
- Creating free radicals
- Initiates polymerization via monomer (Bis GMA)
What is Comphorquinone?
- Photoinitiator
- Most common photo-absorbing material
- Maximum sensitivity is in the BLUE RANGE
- 400-520 nm
- Peak at 468 nm
What is the first step of Polymerization?
Initiation
- Production of reactive free radicals
- Chemical, light, heat
What is the second step of Polymerization?
Propagation
- Monomer units
- Polymer network
- 50-60% degree of conversion
What is the last step of Polymerization?
Termination
What are some different energy sources for curing lights? Which one do we use?
- Halogen
- Plasma-arc
- Argon laser
- LED (WHAT WE USE!)
What does LED stand for?
Light Emitting Diode
What is the spectrum of an LED curing light for camphorquinone?
430-490 nm
What are some perks of using an LED curing light?
- Long lasting light source
- Minimal bulb aging
- Shock resistant
- Less lateral heat production
- Efficient
- Cordless
What are 2 different photoinitiators other then CQ?
PPD & TPO - VIOLET SPECTRUM
They use LESS yellow than comphorqinone
Less the CQ… 398 nm and 381 nm respectively
What is neat about third generation LED lights?
- They are Dual-Emission Spectrum
- Reportedly cures all photo-initiated materials
What is Attenuation of Violet Light?
- Decreases as thickness of composite increases
- Fill particles tend to scatter more light at shorter wavelengths
What type of curing light do you use?
- Dual-Spectrum LED
- Bluephase G2 by Ivoclar
- 10 mm diameter fiber-optic light guide
- Soft start polymerization available
- Low or high setting (650 or 1200 mW)
What are the effects of INCREASED light exposure?
- Increased depth of cure
- Increased conversion (polymerization)
- Increased hardness
- Only up to a threshold…
What are the effects of DECREASED light exposure?
Inadequate polymerization
What are some consequences of inadequate polymerization?
- Reduced physical properties
- Decreased color stability
- Increased wear
- Increased Solubility
- Leaching of unreacted monomer
- Increased toxicity
What is light attenuation?
Irradiance decreases with depth
Light gets absorbed and scattered from colored molecules, filler particles, and polymerized polymer
What factors affect HOW LONG it takes to cure an increment of composite?
Depends on…
- Radiant exposure (energy density - curing light strength)
- Distance from composite
- Collimation of light (light waves running parallel)
- Angulation
- Spectral emission
- Attenuation of light
- Composite Type (Opacity, shade, photoinitiator)
Larger tips of curing lights have low or high irradiance?
- Low (less concentrated)
Smaller tips of curing lights have low or high irradiance?
- High (more concentrated)
Does the shade of composite effect energy transmission?
Yes!
Darker and opaque shades impede energy transmission
Does the angle you hold the curing light matter?
Yes!
Ideally you should hold it at 0 degrees
Why have blue and violet on our curing lights at Dunn?
Covers multiple photoinitiators
We call this multispectrum
1200 mW on high
510 mW on low
You will want to INCREASE your curing time for the following factors…
- Lower irradiances - (less concentrated)
- Darker shades
- Greater distances
- Poor collimation (beams running parallel)
- Poor angulation
You will want to DECREASE your curing time for the following factors…
- Higher irradiances - (more concentrated)
- Lighter shades
- Close distance
- Good collimation (beams running parallel)
- Good angulation
What is the percentage of composite shrinkage after curing?
1-6%
- Microleakage
- Staining
- Post-op sensitivity
What is the primary reason for replacement of composites?
Secondary caries
What do studies show about “Soft Start” curing technique?
- May not be clinically significant
- More studies needed
Is there a significant risk of retinal damage due to blue light?
Yes!
What device can you use to measure if a curing light is working correctly?
Radiometer - $100
