21 - Visible Light Curing Flashcards
four main structures of eye affected by ligh
- lens
- cornea
- retina
- vitreous humor
what filters long wavelength UV radiation (300-400 nm)
lens
excess exposure to long UV radiation can cause what
lens damage and cataract formation
what filters middle wavelength UV (~300 nm)
cornea
what protects retina
cornea
what is most effective against wavelength around 500 nm
vitreous humor
what protects retina
vitreous humor
what are types of retinal damage caused by visible light
- mechanical
- thermal-energy absorption
- photochemical = actinic
retinal tissue absorbs light whose energy acts like high power shock waves causes what type of damage
mechanical
an increase in temperature of 10 degree can damage the eye due to what damage
thermal-energy absorption
what is damage by extended exposure to short wavelength light
photochemical = actinic
what is primary source of ocular damage associated with VLC techniques
photochemical damage
does the light source need to be bright or intense?
NO! it will cause photochemical damage
___ light is more damaging than ___
blue; green
why is vitreous humor not effective from photochemical damage
because it is not intensity dependent
what are parameters that determine type of retinal insult
- power level
- exposure duration
- wavelength (color)
- cumulative effects
how does power level result in retinal insult
- Mechanical and thermal require high intensity of light
- Photochemical NOT intensity dependent
how does exposure duration result in retinal insult
- More exposure=more damage
- Chemical damage has cumulative effects
- Repeated exposure to blue light (468-480nm) causes an irreversible loss of blue sensitivity
how does wavelength cause retinal insult
Blue/green spectrum most responsible; blue most damaging (loss of being able to see blue)
how do cumulative effects cause retinal insult
- Repeated exposure to blue peaks (460nm) produces irreversible loss of blue sensitivity
- Same for exposure to green peaks
methods to protect eyes
- amber eyeglasses
- hand held sheid
- shield mount on light source
- avoid direct vision
how to avoid direct vision when using light source
- do not look at light source, avert eyes
- have patient close eyes
- do not turn light on until in patient’s mouth
what are conditions that require extra precautions regarding eye protection
- cataract surgery
- photosensitive drug therapy
- albinism
- known ocular diseases
why do patients that have cataract surgery require extra precaution
patient has no lens protection
why do patients that have photosensitive drug therapy require extra precaution
do to the sulfonamides, chlorthiazides, and phenothiazines
what are known ocular diseases require extra precaution
retinitis pigmentosa and maculaar degeneration of retina
what does QTH stand for
Quartz Tungsten Halogen
what are types of curing lights
- QTH = Quartz Tungsten Halogen
- Variable Curing Intensity Halogen
- Argon lasers
- Plasma Arc Curing Unit (PAC)
- Light Emitting Diode (LED) i.e VALO (Ultradent)
what type of curing light:
As unit ages, the bulb and reflector degrade, reducing light output and curing effectiveness
halogen
what is a curing radiometer
light analyzer
what is checked on the halogen curing light for clarity?
light tip (e.g., resin composite or bonding agent adhered to tip)
what can affect depth of of cure
- Shade
- Translucency
- Photoinitiator concentration
- Elastic modulus
- These are more important to determine cure than curing mode.
what have increased degre of conversion compared to halogen, depth of cure improved, but HIGH COST
argon lasers
does argon cure faster than halogen
YES
what light:
Monochromatic light, with narrower bandwidth. Some manufacturers using photoinitiators with absorption spectra different than camphorquinone (470 nm)
argon lasers
what light:
- Higher irradiance than halogen
- Cures faster than halogen
- Increased cure rate DOES NOT enhance adhesion of composite resin to cavity walls
plasma arc curing (PAC)
advantages of LED light
- Wavelength spectrum emission close to camphorquinone (CQ)
- More energy efficient
- Diodes have life span 1,000X longer than halogen
what are the most expensive curing light
LED - light emitting diodes ($1599)
what are disadvantages of LED lights
- Narrow wavelength spectrum (with earlier versions)-much better with newer lights that have multiple bulbs to cover more nanometers
- Limits usefulness in curing materials that do not use camphorquinone–Not as much of a concern anymore
- Heat Generation!
what is the power of Dentsupply SIrona SmartLite Focus (the light cure we use in lab)
power = 1000 mv/cm^2
range for curing with Smart Lite
460-490 nm
as long as dental material cures with 460-490 nm
what are activating compounds to generate free radicals
- Diketones (Camphoroquinone)
- Aromatic Ketones (Biacetyl)
- Reducing Agents (Tertiary Amines)
what stops free radical generations
free radical scavengers
free radicals originate from what
ketone source such as diketones or aromatic ketones
what has a reducing agent (aliphatic tertiary amine) which is present to lower the energy in the bonds of the ketone source so they are split to form free radicals.
free radical generation
do free radical generations amines participate in chemical reaction as in the chemically cured materials
NO! so no amine discoloration
describe how light source is very specific
Visible light activation using
wavelengths greater than ^400
nanometers
Most effective= ^468nm-480nm
Must have sufficient
INTENSITY=300mW/cm2
what initiate the polymerization of the bisGMAor urethane dimethacrylate
free radicals
free radicals must have what
MUST have proper wavelength of light
INTENSITY of light source must be highenough
what are factors influencing cure
Wavelength of Emitted Light (should be
450-500nm)
Intensity of Light Source (Affected by bulb life and line voltage)
Time (of exposure to light)
Distance of light from resin
Shade of resir
Type of filler
Thickness of resin
advantages of VLC resin
Increased restoration density
Decreased surface staining
Increased working time
Improved color stability
Improved shelf life
Higher degree of resin polymerization
how do we knot if lights are working properly
- BlueLight Analytics CheckMARC™
- Radiometers
are irradiance measurements from dental radiometer ACCURATE?
no - generally inaccurate!
T/F: The tip of a curing light may have hot and cold spotsthat can lead to clinically relevant differences when curing. As a result, the irradiance value given by a radiometer is insufficient to characterize the light output from a curing light.
TRUE
the sensitivity of dental radiometers to light of different wavelengths varies. what does this mean?
This means that the irradiance readings given by the radiometer may ignore or incorrectly read some of the output from a curing light
does a dental radiometer give a COMPLETE portrayal of the output from a curing light
NO! INCOMPLETE!
why worry about light output
- Depth of Cure
- Curing through a ceramic crown or inlay/onlay
- Cheap lights from overseas
- Best care for our patients!!!
