Use of light cure in dentistry Flashcards
Name some photoactivated materials that require light cure
- Certain sealants
- Resin-based cements
- Bonding agents
- Composite restorative materials
- Resin modified glass ionomer materials
What is the material like when uncured?
soft and malleable
all the components are not linked together
What happens when the light source with certain irradiance and wavelength is curing the material?
photoinitiator is activated releasing free radicals giving energy bringing the remaining components together
The material is now at a hard stage.
When does the creme brûlée effect occur?
when the incorrect energy levels, insufficient time curing occurs
fully cured at top but soft and under cured underneath
What does the creme brûlée effect lead to?
- Reduction of mechanical properties, leading to…
. marginal breakdown
. increased wear
. decreased strength
. fractures
. staining
- Microleakage -> secondary caries
- Increased elution of non-reacted monomers -> post-operative sensitivity
What light is released in early 1970s?
UV lights
What light is released in later 1970s?
Quartz-tungsten halogen lights
What light is released in 1990s?
first generation blue LED lights
What light is released in late 1990s?
plasma-arc lights
What light is released in 2000s?
second generation blue LED lights
What light is released in late 2000s?
third generation polywave LED lights
What light is released in 2021?
fourth generation LED lights from scan wave technology
What is the most common wavelength required for resin-based materials?
blue - visible blue light
What is happening to light curing units with evolution of dental materials?
materials now contain photoinitiators that require a near violet light (a lower wavelength)
production of a polywave light that contains a bulb emitting light for blue and the near violet wavelengths
What is the peak wavelength of camphorquinone?
470nm
What is the peak wavelength of lucirin TPO and PPD?
390-410nm
What are the light factors affecting the curing process?
- Wavelength
- Irradiance
- Effective tip size
- Homogeneity
What are the clinical factors affecting the curing process?
- Distance
- Protective sleeves, restoration size, matrix bands, etc
- Damage / contamination done to LED tip
- Handling technique
What equation can be used to calculate energy from irradiance and time?
Energy (mJ/cm2) = irradiance (mW/cm2) x time (s)
What do most manufacturer’s state as the minimum required irradiance?
500 mW/cm2
What happens to the older light curing units?
lower irradiance
Why does irradiance need measuring on a regular basis?
bulbs deteriorate with time and may need replacing
How can we effectively cure large restorations?
multiple curing overlapping the light will fully cure the material and reduce risk of fractures and failures
What do cheaper lights tend to be?
beam is less homogenous
