21 - Visible Light Curing

Question 1

four main structures of eye affected by ligh

Answer 1

1. lens
2. cornea
3. retina
4. vitreous humor

Question 2

what filters long wavelength UV radiation (300-400 nm)

Answer 2

lens

Question 3

excess exposure to long UV radiation can cause what

Answer 3

lens damage and cataract formation

Question 4

what filters middle wavelength UV (~300 nm)

Answer 4

cornea

Question 5

what protects retina

Answer 5

cornea

Question 6

what is most effective against wavelength around 500 nm

Answer 6

vitreous humor

Question 7

what protects retina

Answer 7

vitreous humor

Question 8

what are types of retinal damage caused by visible light

Answer 8

1. mechanical
2. thermal-energy absorption
3. photochemical = actinic

Question 9

retinal tissue absorbs light whose energy acts like high power shock waves causes what type of damage

Answer 9

mechanical

Question 10

an increase in temperature of 10 degree can damage the eye due to what damage

Answer 10

thermal-energy absorption

Question 11

what is damage by extended exposure to short wavelength light

Answer 11

photochemical = actinic

Question 12

what is primary source of ocular damage associated with VLC techniques

Answer 12

photochemical damage

Question 13

does the light source need to be bright or intense?

Answer 13

NO! it will cause photochemical damage

Question 14

___ light is more damaging than ___

Answer 14

blue; green

Question 15

why is vitreous humor not effective from photochemical damage

Answer 15

because it is not intensity dependent

Question 16

what are parameters that determine type of retinal insult

Answer 16

1. power level
2. exposure duration
3. wavelength (color)
4. cumulative effects

Question 17

how does power level result in retinal insult

Answer 17

• Mechanical and thermal require high intensity of light
• Photochemical NOT intensity dependent

Question 18

how does exposure duration result in retinal insult

Answer 18

• More exposure=more damage
• Chemical damage has cumulative effects
• Repeated exposure to blue light (468-480nm) causes an irreversible loss of blue sensitivity

Question 19

how does wavelength cause retinal insult

Answer 19

Blue/green spectrum most responsible; blue most damaging (loss of being able to see blue)

Question 20

how do cumulative effects cause retinal insult

Answer 20

• Repeated exposure to blue peaks (460nm) produces irreversible loss of blue sensitivity
• Same for exposure to green peaks

Question 21

methods to protect eyes

Answer 21

1. amber eyeglasses
2. hand held sheid
3. shield mount on light source
4. avoid direct vision

Question 22

how to avoid direct vision when using light source

Answer 22

1. do not look at light source, avert eyes
2. have patient close eyes
3. do not turn light on until in patient’s mouth

Question 23

what are conditions that require extra precautions regarding eye protection

Answer 23

1. cataract surgery
2. photosensitive drug therapy
3. albinism
4. known ocular diseases

Question 24

why do patients that have cataract surgery require extra precaution

Answer 24

patient has no lens protection

Question 25

why do patients that have photosensitive drug therapy require extra precaution

Answer 25

do to the sulfonamides, chlorthiazides, and phenothiazines

Question 26

what are known ocular diseases require extra precaution

Answer 26

retinitis pigmentosa and maculaar degeneration of retina

Question 27

what does QTH stand for

Answer 27

Quartz Tungsten Halogen

Question 28

what are types of curing lights

Answer 28

1. QTH = Quartz Tungsten Halogen 2. Variable Curing Intensity Halogen 3. Argon lasers 4. Plasma Arc Curing Unit (PAC) 5. Light Emitting Diode (LED) i.e VALO (Ultradent)

Question 29

what type of curing light: As unit ages, the bulb and reflector degrade, reducing light output and curing effectiveness

Answer 29

halogen

Question 30

what is a curing radiometer

Answer 30

light analyzer

Question 31

what is checked on the halogen curing light for clarity?

Answer 31

light tip (e.g., resin composite or bonding agent adhered to tip)

Question 32

what can affect depth of of cure

Answer 32

1. Shade 2. Translucency 3. Photoinitiator concentration 4. Elastic modulus 5. These are more important to determine cure than curing mode.

Question 33

what have increased degre of conversion compared to halogen, depth of cure improved, but HIGH COST

Answer 33

argon lasers

Question 34

does argon cure faster than halogen

Answer 34

YES

Question 35

what light: Monochromatic light, with narrower bandwidth. Some manufacturers using ***photoinitiators*** with absorption spectra different than ***camphorquinone*** (470 nm)

Answer 35

argon lasers

Question 36

what light: - Higher irradiance than halogen - Cures faster than halogen - Increased cure rate DOES NOT enhance adhesion of composite resin to cavity walls

Answer 36

plasma arc curing (PAC)

Question 37

advantages of LED light

Answer 37

- Wavelength spectrum emission close to camphorquinone (CQ) - More energy efficient - Diodes have life span 1,000X longer than halogen

Question 38

what are the most expensive curing light

Answer 38

LED - light emitting diodes ($1599)

Question 39

what are disadvantages of LED lights

Answer 39

1. Narrow wavelength spectrum (with earlier versions)-much better with newer lights that have multiple bulbs to cover more nanometers 2. Limits usefulness in curing materials that do not use camphorquinone--Not as much of a concern anymore 3. Heat Generation!

Question 40

what is the power of Dentsupply SIrona SmartLite Focus (the light cure we use in lab)

Answer 40

power = 1000 mv/cm^2

Question 41

range for curing with Smart Lite

Answer 41

460-490 nm as long as dental material cures with 460-490 nm

Question 42

what are activating compounds to generate free radicals

Answer 42

1. Diketones (Camphoroquinone) 2. Aromatic Ketones (Biacetyl) 3. Reducing Agents (Tertiary Amines)

Question 43

what stops free radical generations

Answer 43

free radical scavengers

Question 44

free radicals originate from what

Answer 44

ketone source such as diketones or aromatic ketones

Question 45

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.

Answer 45

free radical generation

Question 46

do free radical generations amines participate in chemical reaction as in the chemically cured materials

Answer 46

NO! so no amine discoloration

Question 47

describe how light source is very specific

Answer 47

Visible light activation using wavelengths greater than ^400 nanometers Most effective= ^468nm-480nm Must have sufficient INTENSITY=300mW/cm2

Question 48

what initiate the polymerization of the bisGMAor urethane dimethacrylate

Answer 48

free radicals

Question 49

free radicals must have what

Answer 49

MUST have proper wavelength of light INTENSITY of light source must be highenough

Question 50

what are factors influencing cure

Answer 50

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

Question 51

advantages of VLC resin

Answer 51

Increased restoration density Decreased surface staining Increased working time Improved color stability Improved shelf life Higher degree of resin polymerization

Question 52

how do we knot if lights are working properly

Answer 52

- BlueLight Analytics CheckMARC™ - Radiometers

Question 53

are irradiance measurements from dental radiometer ACCURATE?

Answer 53

no - generally inaccurate!

Question 54

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.

Answer 54

TRUE

Question 55

the sensitivity of dental radiometers to light of different wavelengths varies. what does this mean?

Answer 55

This means that the irradiance readings given by the radiometer may ignore or incorrectly read some of the output from a curing light

Question 56

does a dental radiometer give a COMPLETE portrayal of the output from a curing light

Answer 56

NO! INCOMPLETE!

Question 57

why worry about light output

Answer 57

1. Depth of Cure 2. Curing through a ceramic crown or inlay/onlay 3. Cheap lights from overseas 4. Best care for our patients!!!