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Composite Light Curing Units
Dr. Jagadeesh. K
P.G 3rd
year
Contents
• Introduction
• Advantages
• Limitations
• Characteristics of light
• Photo polymerization
• Light curing unit
• Types
• New developments
• Exposure
• Inadequate polymerization
• Irradiance
• Total energy density
• Time required for ...
• General considerations
• Maintenance
• Radiometer
– Hand held
– Built in
• Optical hazards
• Optical safety
INTRODUCTION
• Light activated resin system utilizes light energy to initiate
free radicals.
• Light cure composites were ...
• Available as single paste system in a light proof syringe.
• Consists of photosensitizer and an amine activator.
• Photo...
• Limitations:
– Limited curing depth so requires incremental building
up.
– Relatively poor accessibility in posterior &
...
Contact Pro2
Terms used to describe light sources for
polymerization of dental resins
Characteristics of Light
• Visible light
– 400-700 nm
• Most composites sensitive
– 400-520 nm (blue)
• Photo-initiator in...
Photo-polymerization
• Camphorquinone (CQ)
– most common
photo-absorbing material
– maximum sensitivity
• blue range
• 468...
Other photoinitiators used
1-phenyl 1, 2-propanedione (PPD)
Bis acylphosphine oxide (BAPO)
Tri acyl phosphine
Light Curing Unit
• It is an instrument capable of generating and transmitting a
high intensity blue light with a waveleng...
UV light cure systems
• NUVA-fil introduced by L.D.CAULK CO in 1970 was the first
in Light Cure Composite resins
• UV ligh...
• Wave length oscillating between 320 and 365nm
Disadvantages
• Limited depth of cure
• Harmful effects of UV radiation
• ...
Types of Light Curing Units
• Four light curing
options
– Quartz tungsten
halogen
– plasma-arc
– laser
– LED
• In order of lowest to highest intensity
– LED lamps
– QTH lamps
– PAC lamps
– Argon laser lamps
Quartz-Tungsten-Halogen
• Most widely used dental curing light.
• Consists of a quartz bulb with a
tungsten filament in a ...
• Quartz
– encasing structure
– crystalline
– heat resistant
• Tungsten
– filament coil
– flow of electricity
• Halogen ga...
• Heat
• Cooling critical
– do not turn off fan
– bulb life dramatically decreases
• Power Density:
500-1500mW/cm2
• Filters
– band-pass
• restricts broader light
to narrow blue light
• 400-500 nm
• range of photo-initiators
– 99.5% of o...
• Advantages:
– Economical.
– Filters used to dissipate heat to the oral
structures & provide restriction of visible
light...
460
camphorquinone
halogen
500420 nm
1
0.5
1
0.8
0.6
0.4
0.2
Emission
Absorptionunits
Spectral Emission / CQ Absorption
Plasma-Arc (PAC)
• Two tungsten electrodes
– small gap
• Pressurized chamber
– xenon gas
• High-voltage spark
– ionizes ga...
• High levels of IR and UV
– extensive filtering
• Blue light 400-500 nm.
• Heat generated.
• Has a highly filtered photos...
• Advantages:
– High irradiance up to 2400 mW/cm2
– claim 1-3 sec cure.
– Power density of 600-2050 mW/cm2
• Disadvantages...
Argon Laser
• Laser photons travel in phase (coherent) & are collimated
such that they travel in same direction.
• High en...
• Advantages:
– Produces narrow focused non divergent monochromatic
light of 490nm.
– Less power utilized.
– Thoroughness ...
Light-Emitting Diodes (LED)
• Combination of two semiconductors - n
doped & p doped.
• n doped have excess of e-
& p doped...
• Initially used Silicon – Carbide electrode.
• Now Gallium – Nitride electrode.
• When LED of suitable band gap energy is...
• Advantages:
– Long service life of more than 10,000hrs.
– Low temperature development.
– No filter system.
– Low power c...
• First generation
– high cost
– low irradiance
• < 300 mW/cm2
• increase exposure time
Classification
• 2nd
generation (2002-2004)
• Using more powerful diodes than in first generation.
• Using LED chip design raising out pu...
• 3rd generation:
• In order to enable curing other restorative material not
only use (CQ) but use other intiators like (C...
Why do you think the manufactures go to
another photo initiators rather than (CQ) ??
• One of the main problem of
CQ initiator is there
yellow color rather than
their need to prolonged
light curing.
• Which ...
New Developments
• Narrow spectrum lights
– argon laser
– LED
• Other photoinitiators absorb at lower wavelengths
– Phenyl...
1
Spectral Emission / Absorption
1
460
halogen
LED
500420 nm
0.5
0.8
0.6
0.4
0.2
Emission
Absorptionunits
PPD
Phenyl propa...
Photo Initiators & Absorption Spectrum
Camphoroquinone
470 500400 430370
PPD
LED
Halogen
Argon Laser
Plasma Arc
Violet Blu...
From this graph we should see:
1- the peak of wave length of LED
units is perfectly matching the
wavelength needed to acti...
•As shown before 1st
and 2nd
generation of LED cannot activate
the new initiators of RBC.
•So the manufactures provide the...
1- has broader spectrum than QTH
2- easily handle with high power irradiance.(1000-3000
mW/cm2)
3- high battery capacity.
...
•Heat-sink features and automatic thermal cut out due to thermal
over heating.
•No stable irradiance or spectral stability...
Exposure
• Increased light exposure
– increased depth of cure
– increased conversion
• polymerization
– increased hardness...
Inadequate Polymerization
• Lack of retention
• Increased wear
• Color instability
• Microleakage
– post-op sensitivity
– ...
Techniques of light curing
• Continuous curing techniques:
1) uniform continuous curing.
2) Step cure.
3) Ramp cure.
4) Hi...
1) Uniform continuous cure:
• Light of medium constant intensity.
• Applied to composite for period of time.
• The most fa...
2) Step Cure:
• Firstly used low energy and then stepped up to high energy
• The purpose for Step cure is decreasing the d...
3) Ramp cure:
• The light is applied in low intensity and then
gradually increase over the time.
• It decrease initial str...
4) High energy pulse cure.
• High energy (1000-2800 mW/cm2
) which is three or six
times the normal power.
• It is used in...
5) Pulse delay cure.
• Single pulse of light applied to restoration then followed by
pause then a second pulse with higher...
Irradiance
• Power (mW) incident
upon an area (cm2
)
– surface area of the tip
of the light guide
• Large tips
– lower irr...
• The use of a single “irradiance” value to describe the output
from a LCU should be interpreted with caution as it implie...
• spectrometer-based systems that make many measurements
every second and have become the “gold standard” for
measuring th...
Spectral Emission–Spectral Radiant
Power (W/nm)
• To be effective when photocuring an RBC, sufficient spectral
radiant pow...
Beam profile of the LCU
Type of Composite
• Microfills scatter light
• Darker shades impede energy transmission
• Glass fillers transmit light bet...
How long does it take to
adequately cure a composite?
• Depends on
– energy density
• irradiance of light x time
– distanc...
So, how long should I cure the
composite?!
• Increase curing time
– lower irradiances
• LED
• Halogen
– microfill composit...
use high irradiance?
• Higher temperatures
• Accelerated polymerization shrinkage
– stress
• cracks, crazing
General Considerations
• A good rule of thumb is that the minimum power density
output should never drop below 300mW/cm2
•...
• Intensity of light is inversely proportional to the distance
from the fiber optic tip to the composite surface.
• Theref...
• Most light curing techniques require minimum of 20 sec
for adequate curing.
• To guarantee adequate curing, it is a comm...
Maintenance
• Periodic visual inspection of unit
– light guide
– filters
– bulb
• Check irradiance
– radiometer
Contamination of Light Tip
• Reduces passage of light
• Reflects light
– increases heat build-up
– shortens bulb life
• Re...
Radiometer
• Consists of photosensitive diode
– specific for light
• Measures total light output at curing tip
– hand-held...
Optical Hazards
• Halogen laboratory study
– No thermal hazard
– Photochemical hazard
• Roll
– max 1 min/day reflected lig...
Optical Safety
• Do not look directly at light
• Protection recommended
– glasses
– shields
• May impair ability
to match ...
PHOTOCURING TRAINING, EVALUATION, AND
PROCESS MANAGEMENT
The MARC Device and Training System
Four variables affect the ext...
• A recently introduced device, “MARC” (an acronym for
“managing accurate resin curing,” BlueLight Analytics Inc.,
Halifax...
• Spectrum-corrected sensors inside the dentoform teeth are
attached to a laboratory-grade spectro radiometer embedded
wit...
• In addition to providing real-time feedback to judge when
adequate photoenergy has been delivered, the MARC device
can a...
CONCLUSION
• The commonly used term of irradiance measured at the light
tip should no longer be used to describe the outpu...
• Ideally, both manufacturers and researchers should include
the following information about the LCU:
1. Radiant power out...
References
• Phillips’ Science of Dental Materials – 12th
ed
• Craig’s Restorative Dental Materials – 13th
ed
• Light curi...
• Text book of operative dentistry – vimal. k sikri 4th
ed
Light curing units - Dr. JAGADEESH KODITHYALA
Light curing units - Dr. JAGADEESH KODITHYALA
Light curing units - Dr. JAGADEESH KODITHYALA
Light curing units - Dr. JAGADEESH KODITHYALA
Light curing units - Dr. JAGADEESH KODITHYALA
Light curing units - Dr. JAGADEESH KODITHYALA
Light curing units - Dr. JAGADEESH KODITHYALA
Light curing units - Dr. JAGADEESH KODITHYALA
Light curing units - Dr. JAGADEESH KODITHYALA
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Light curing units - Dr. JAGADEESH KODITHYALA

  1. 1. Composite Light Curing Units Dr. Jagadeesh. K P.G 3rd year
  2. 2. Contents • Introduction • Advantages • Limitations • Characteristics of light • Photo polymerization • Light curing unit
  3. 3. • Types • New developments • Exposure • Inadequate polymerization • Irradiance • Total energy density • Time required for adequate polymerization • Soft start polymerization
  4. 4. • General considerations • Maintenance • Radiometer – Hand held – Built in • Optical hazards • Optical safety
  5. 5. INTRODUCTION • Light activated resin system utilizes light energy to initiate free radicals. • Light cure composites were introduced to overcome the limitations of self curing composites – Less porosity and discoloration. – Longer working time. – Ease of manipulation. – Increased hardness and wear resistance of superficial layer.
  6. 6. • Available as single paste system in a light proof syringe. • Consists of photosensitizer and an amine activator. • Photosensitizer – Camphoroquinone (CQ) absorbs blue light with wavelengths between 400-500 nm. • Amine activator – dimethylaminoethyl methacrylate (DMAEMA)
  7. 7. • Limitations: – Limited curing depth so requires incremental building up. – Relatively poor accessibility in posterior & interproximal areas. – Variable exposure times due to shade differences. – Sensitivity to room illumination. – Requires more clinical time. – Expensive due to cost of light curing unit.
  8. 8. Contact Pro2
  9. 9. Terms used to describe light sources for polymerization of dental resins
  10. 10. Characteristics of Light • Visible light – 400-700 nm • Most composites sensitive – 400-520 nm (blue) • Photo-initiator in resin – absorbs photon energy – combines with activator • Amine (DMAEMA) – creating free radicals • initiates polymerization
  11. 11. Photo-polymerization • Camphorquinone (CQ) – most common photo-absorbing material – maximum sensitivity • blue range • 468 nm to 474nm
  12. 12. Other photoinitiators used 1-phenyl 1, 2-propanedione (PPD) Bis acylphosphine oxide (BAPO) Tri acyl phosphine
  13. 13. Light Curing Unit • It is an instrument capable of generating and transmitting a high intensity blue light with a wavelength oscillating between 400-500 nm that is designed specifically to polymerize visible light sensitive dental material.
  14. 14. UV light cure systems • NUVA-fil introduced by L.D.CAULK CO in 1970 was the first in Light Cure Composite resins • UV light curing systems used Benzoin methyl ether as initiater • UV radiation generated by a light source capable of emitting an intense luminous radiation was used to polymerize the resins
  15. 15. • Wave length oscillating between 320 and 365nm Disadvantages • Limited depth of cure • Harmful effects of UV radiation • Opthalmological effects • Carcinogenic • Loss of intensity over time.
  16. 16. Types of Light Curing Units • Four light curing options – Quartz tungsten halogen – plasma-arc – laser – LED
  17. 17. • In order of lowest to highest intensity – LED lamps – QTH lamps – PAC lamps – Argon laser lamps
  18. 18. Quartz-Tungsten-Halogen • Most widely used dental curing light. • Consists of a quartz bulb with a tungsten filament in a halogen environment. • Electric current passes through an extremely thin tungsten filament which at about 3000o C produces Electro Magnetic radiation in the form of visible light.
  19. 19. • Quartz – encasing structure – crystalline – heat resistant • Tungsten – filament coil – flow of electricity • Halogen gas – protects filament • oxidation – re-deposits tungsten to filament
  20. 20. • Heat • Cooling critical – do not turn off fan – bulb life dramatically decreases • Power Density: 500-1500mW/cm2
  21. 21. • Filters – band-pass • restricts broader light to narrow blue light • 400-500 nm • range of photo-initiators – 99.5% of original radiant energy filtered • Decreased efficiency
  22. 22. • Advantages: – Economical. – Filters used to dissipate heat to the oral structures & provide restriction of visible light to narrower spectrum of initiators. • Disadvantages: – Diminished light intensity over a period of time causes degradation of halogen bulb & degradation of reflector. – Shorter life about 100 hrs. – High temperature production. – Bond strength decreases with increase in distance.
  23. 23. 460 camphorquinone halogen 500420 nm 1 0.5 1 0.8 0.6 0.4 0.2 Emission Absorptionunits Spectral Emission / CQ Absorption
  24. 24. Plasma-Arc (PAC) • Two tungsten electrodes – small gap • Pressurized chamber – xenon gas • High-voltage spark – ionizes gas • plasma • High voltage is generated between two tungsten electrodes creating a spark that ionizes Xenon creating a conductive gas known as Plasma.
  25. 25. • High levels of IR and UV – extensive filtering • Blue light 400-500 nm. • Heat generated. • Has a highly filtered photosensor which measures light coming from end of curing tip based on which microcomputer calculates the time required for curing.
  26. 26. • Advantages: – High irradiance up to 2400 mW/cm2 – claim 1-3 sec cure. – Power density of 600-2050 mW/cm2 • Disadvantages: – Expensive. – High temperature development. – Heavy so not portable. – Requires an in built filter to produce narrow continuous spectrum.
  27. 27. Argon Laser • Laser photons travel in phase (coherent) & are collimated such that they travel in same direction. • High energy – coherent, non-divergent – non-continuous • Highest intensity • Emits single wavelength of 490nm. • Very expensive
  28. 28. • Advantages: – Produces narrow focused non divergent monochromatic light of 490nm. – Less power utilized. – Thoroughness and depth of cure is greater. – Laser curing bond strength did not decrease with increasing distance. • Disadvantages: – Risk of other tissues being irradiated. – Ophthalmic damage of operator and patient. – Large in size and heavy. – expensive
  29. 29. Light-Emitting Diodes (LED) • Combination of two semiconductors - n doped & p doped. • n doped have excess of e- & p doped have holes. • When both types are combined & voltage is applied e- & holes connect resulting in emission of light of characteristic wavelength.
  30. 30. • Initially used Silicon – Carbide electrode. • Now Gallium – Nitride electrode. • When LED of suitable band gap energy is used they produce only the desired wavelength range. • Narrow emission spectrum – 400-490 nm • peak at 470 nm • near absorption max of camphoroquinone • efficient
  31. 31. • Advantages: – Long service life of more than 10,000hrs. – Low temperature development. – No filter system. – Low power consumption. – Wavelength of 400-490nm. • Disadvantages: – Photoinitiator is only CQ. – Requires longer exposure time to adequately polymerize microfills & hybrid resin.
  32. 32. • First generation – high cost – low irradiance • < 300 mW/cm2 • increase exposure time Classification
  33. 33. • 2nd generation (2002-2004) • Using more powerful diodes than in first generation. • Using LED chip design raising out put of LED to QTH units. • But it was expensive. • High heat generation so manufacture incorporate external fans for cooling or automatic unit shutoff to avoid over heating.
  34. 34. • 3rd generation: • In order to enable curing other restorative material not only use (CQ) but use other intiators like (CQ+tertiary amine), (1-phenyl propane), (trimethylbenzyl-diphenyl phosphine enzyme), (Leucin TPO). • These other initiators need near UV wavelength to activate them.
  35. 35. Why do you think the manufactures go to another photo initiators rather than (CQ) ??
  36. 36. • One of the main problem of CQ initiator is there yellow color rather than their need to prolonged light curing. • Which give the RBC undesirable yellow color after polymerization • So the manufactures turn into another substitutes as mentioned before
  37. 37. New Developments • Narrow spectrum lights – argon laser – LED • Other photoinitiators absorb at lower wavelengths – Phenyl propanedione (PPD) - Bis acylphossphine oxide(BAPO) - Tri acyl phosphine • Narrow spectrum lights may not polymerize materials containing other initiators
  38. 38. 1 Spectral Emission / Absorption 1 460 halogen LED 500420 nm 0.5 0.8 0.6 0.4 0.2 Emission Absorptionunits PPD Phenyl propanedione camphorquinone
  39. 39. Photo Initiators & Absorption Spectrum Camphoroquinone 470 500400 430370 PPD LED Halogen Argon Laser Plasma Arc Violet Blue Green 450 AADR Abstract 0042 Efficiency of Various Light Initiators after Curing with Different Light-curing Units P. BURTSCHER, and V. RHEINBERGER, Ivoclar Vivadent, Schaan, Liechtenstein J. Lindemuth 2003
  40. 40. From this graph we should see: 1- the peak of wave length of LED units is perfectly matching the wavelength needed to activate CQ initiators. 2- the new initiators like Lucerin TPO & PPD their peak near UV wave length away from LED wave length zone. Poggio, C., Lombardini, M., Gaviati, S., & Chiesa, M. (2012). Evaluation of Vickers hardness and depth of cure of six composite resins photo-activated with different polymerization modes. Journal of Conservative Dentistry :  JCD, 15(3), 237–41.
  41. 41. •As shown before 1st and 2nd generation of LED cannot activate the new initiators of RBC. •So the manufactures provide the their light cures with LED chipsets that emit more than one wave length.(POLYWAVE LED) •It provide sufficient irradiance to cure any type of composite.
  42. 42. 1- has broader spectrum than QTH 2- easily handle with high power irradiance.(1000-3000 mW/cm2) 3- high battery capacity. Advantages:
  43. 43. •Heat-sink features and automatic thermal cut out due to thermal over heating. •No stable irradiance or spectral stability so the new sensitive initiators which are sensitive to spectrum of the wave length, are not probably activated Disadvantages:
  44. 44. Exposure • Increased light exposure – increased depth of cure – increased conversion • polymerization – increased hardness – up to threshold • Decreased light exposure – inadequate polymerization
  45. 45. Inadequate Polymerization • Lack of retention • Increased wear • Color instability • Microleakage – post-op sensitivity – secondary caries
  46. 46. Techniques of light curing • Continuous curing techniques: 1) uniform continuous curing. 2) Step cure. 3) Ramp cure. 4) High-energy pulse cure. • Discontinuous cure techniques: 1) pulse delay cure.
  47. 47. 1) Uniform continuous cure: • Light of medium constant intensity. • Applied to composite for period of time. • The most familiar method that currently used. • Carried out by QTH & LED curing units.
  48. 48. 2) Step Cure: • Firstly used low energy and then stepped up to high energy • The purpose for Step cure is decreasing the degree of polymerization shrinkage and polymerization stresses by allowing the composite to flow while it is in gel state. • Step Cure cannot be carried out by plasma arc or laser.
  49. 49. 3) Ramp cure: • The light is applied in low intensity and then gradually increase over the time. • It decrease initial stresses and polymerization shrinkage. • It cannot be carried out by plasma arc or Laser curing unit.
  50. 50. 4) High energy pulse cure. • High energy (1000-2800 mW/cm2 ) which is three or six times the normal power. • It is used in bonding of ortho brackets or sealents. • 8-10 sec. • It carried out by argon laser, plasma arc, third generation of LED.
  51. 51. 5) Pulse delay cure. • Single pulse of light applied to restoration then followed by pause then a second pulse with higher intensity and longer duration. • The first low intensity pulse slowing the rate of polymerization, decreasing the rate of shrinkage and stresses in the composite. • While the second high intense pulse allow the composite to reach the final state of polymerization. • It carried out by QTH light cure.
  52. 52. Irradiance • Power (mW) incident upon an area (cm2 ) – surface area of the tip of the light guide • Large tips – lower irradiance • Small tips – higher irradiance Irradiance mW cm2 =Irradiance
  53. 53. • The use of a single “irradiance” value to describe the output from a LCU should be interpreted with caution as it implies that this single irradiance value describes the light that every part of the RBC is receiving. This is not the case for dental curing lights because they all deliver varying degrees of light beam inhomogeneity (Vandewalle et al. 2008; Price, Labrie, et al. 2010; Price, Labrie, et al. 2011; Michaud et al. 2014; Price, Labrie, et al. 2014; de Magalhães Filho et al. 2015; Haenel et al. 2015; Shortall et al. 2015).
  54. 54. • spectrometer-based systems that make many measurements every second and have become the “gold standard” for measuring the output from an LCU (Kirkpatrick 2005). • Such systems are now readily available and can measure radiant exposure (J/cm2 ) over the entire output cycle of the LCU as well recording radiant power (W), spectral radiant power (W/nm), and radiant exitance (W/cm2 ) at any given moment.
  55. 55. Spectral Emission–Spectral Radiant Power (W/nm) • To be effective when photocuring an RBC, sufficient spectral radiant power must fall within the spectral range required to activate the photoinitiator(s) present in the resin (Nomoto 1997; Price and Felix 2009; Leprince et al. 2013), but neither thermopiles nor dental radiometers measure the spectral radiant power.
  56. 56. Beam profile of the LCU
  57. 57. Type of Composite • Microfills scatter light • Darker shades impede energy transmission • Glass fillers transmit light better – hybrids > flowables
  58. 58. How long does it take to adequately cure a composite? • Depends on – energy density • irradiance of light x time – distance from composite – collimation of light – wavelengths • emitted • absorbed – composite type
  59. 59. So, how long should I cure the composite?! • Increase curing time – lower irradiances • LED • Halogen – microfill composites – darker shades – flowable composites – greater distances – poor collimation • Decrease curing time – higher irradiances • Plasma arc – hybrid composites – lighter shades – close distance – good collimation Refer to the manufacturer’s instructions for guidance
  60. 60. use high irradiance? • Higher temperatures • Accelerated polymerization shrinkage – stress • cracks, crazing
  61. 61. General Considerations • A good rule of thumb is that the minimum power density output should never drop below 300mW/cm2 • Shifting from a standard 11mm diameter tip to a small 3mm diameter increases the light output eightfold. • Ideally, the fiber optic tip should be adjacent to the surface being cured but this will lead to tip contamination.
  62. 62. • Intensity of light is inversely proportional to the distance from the fiber optic tip to the composite surface. • Therefore, the tip should be within 2mm of composite to be effective. • Light transmitting wedges for interproximal curing & light focusing tips for access into proximal boxes are available. • Intensity of the tip output falls off from the centre to the edges. So bulk curing of the composite produces bullet shaped curing pattern. • DC is related to intensity of light & duration of exposure.
  63. 63. • Most light curing techniques require minimum of 20 sec for adequate curing. • To guarantee adequate curing, it is a common practice to postcure for 20-60 sec. postcuring improves the surface properties slightly. • More intense curing units have been developed to hasten the curing cycles. E.g. PAC & laser units. • Rapid polymerization may produce excessive polymerization stresses & weaken the bonding system layer against tooth structure.
  64. 64. Maintenance • Periodic visual inspection of unit – light guide – filters – bulb • Check irradiance – radiometer
  65. 65. Contamination of Light Tip • Reduces passage of light • Reflects light – increases heat build-up – shortens bulb life • Remove debris – polishing kit – blade
  66. 66. Radiometer • Consists of photosensitive diode – specific for light • Measures total light output at curing tip – hand-held – built-in • Light-specific radiometers – halogen – LED
  67. 67. Optical Hazards • Halogen laboratory study – No thermal hazard – Photochemical hazard • Roll – max 1 min/day reflected light – 30 cm • Satrom – stare directly for > 2.4 minutes – 25 cm distance
  68. 68. Optical Safety • Do not look directly at light • Protection recommended – glasses – shields • May impair ability to match tooth shades
  69. 69. PHOTOCURING TRAINING, EVALUATION, AND PROCESS MANAGEMENT The MARC Device and Training System Four variables affect the extent to which a resin is polymerized within the tooth: operator technique, type of curing light, location of the restoration, type of resin used.
  70. 70. • A recently introduced device, “MARC” (an acronym for “managing accurate resin curing,” BlueLight Analytics Inc., Halifax, NS), takes these four variables into by measuring both the irradiance and the energy received by simulated preparations in a mannequin head. • The MARC device combines precise, laboratory spectral technology with clinically relevant measuring conditions within prepared dentoform teeth in a mannequin head.
  71. 71. • Spectrum-corrected sensors inside the dentoform teeth are attached to a laboratory-grade spectro radiometer embedded within the manikin’s head to record the light received from curing units. • Output from the spectrometer is fed into a laptop computer, where custom software provides real-time and accumulated comparison data: spectral irradiance, total energy delivered over a given exposure duration, and the estimated exposure duration needed to deliver a specified energy dosage.
  72. 72. • In addition to providing real-time feedback to judge when adequate photoenergy has been delivered, the MARC device can also be used as a training aid for performing optimal clinical photocuring. The effect of minor alterations in tip distance and angle and movement during exposure is displayed in real time, and the ultimate consequence in terms of altered energy delivered is determined. • The device can also be used to determine the ability of various lamps to deliver adequate energy levels between different tooth locations.
  73. 73. CONCLUSION • The commonly used term of irradiance measured at the light tip should no longer be used to describe the output of curing lights as it implies that this is the irradiance the specimen is receiving and takes no account of distance between the LCU and the RBC or the effects of beam inhomogeneity.
  74. 74. • Ideally, both manufacturers and researchers should include the following information about the LCU: 1. Radiant power output throughout the exposure cycle and the spectral radiant power as a function of wavelength 2. Analysis of the light beam profile and spectral emission across the light beam 3. Measurement and reporting of the light the RBC specimen received as well as the output measured at the light tip
  75. 75. References • Phillips’ Science of Dental Materials – 12th ed • Craig’s Restorative Dental Materials – 13th ed • Light curing units: A Review of what we need to know R.B. Price et al, Journal of Dental Research (2015) • Advances in light-curing units: four generations of LED lights and clinical implications for optimizing their use: Part 2. From present to future, Adrian C C Shortall et al, Dental Update · June 2012
  76. 76. • Text book of operative dentistry – vimal. k sikri 4th ed

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