Laser Dentistry Flashcards
What is the height of wave called in EM Spectrum?
Amplitude
What is the distance between 2 corresponding points in a periodic wave called? (the distance a photon travels in one complete oscillation)
Wavelength
What is # of complete oscillations of a wave called? (Cycles/Sec=Hz) also Inverse. proport. to WL
FREQUENCY=”Repetition Rate”=Hertz (Hz) (also “Emission Cycles” or “Pulses” per Second)
What is the velocity of a photon?
Speed of Light=186,282 miles/sec (300,000 km/hr)
How Laser Light is different than Visible Light? (Both are EM Radiation, traveling at the speed of light, as a wave and particle)
1) Man-made (doesn’t exist in nature)
2) special, unique form of light
3) found in WLs-UV,Visible,IR
What is a Photon?
EM particles associated with light=”quanta” of EM energy traveling at the speed of light
Who defined that energy was emitted in quantifiable form?
Max Planck=Quantum Physics=Planck’s Constant (h) =”Quanta packets” E=hv E=hc/wl
What physicist developed Quantum Theory=”photons”=”quanta of light”?
Neil’s Bohr
What physicist is responsible for the theory of “Stimulated Emission of Energy”?
Albert Einstein
if artificially stimulated, excited atoms can absorb “quantum of energy”
Who patented the term LASER?
Gordon Gould in 1957
Who developed the 1st Functional LASER? (credited for 1st LASER) 1st Functional Dental Laser?
1) Theodore Maiman in 1960 (inserted a Ruby Crystal into a photographic flashlamp
2) 1989 - 1st true dental laser
Who created the first LASER?
Charles Townes=MASER=Microwave Amplification by Stimulated Emission of Radiation
Laser Light or Visible Light?
- multiple wavelengths
- non-directional/focused
- unorganized/incoherent
- non-collimated
Visible Light
Laser Light or Visible Light?
- one wavelength
- directional/focused
- organized/coherent
- collimated (“parallel beam”)/monochromatic
Laser Light
- reflected back and forth by precise mirrors
- monochromatic=”one wavelength=one color”
- coherent=”light waves in phase”
- collimated=”non-divergent”
What is the definition of Coherence?
every wave is of the SAME WL/IN PHASE (Amplitudes Aligned)…the photons are well-ordered and travel parallel to each other
What is Amplification? (Amplitudes are aligned=”coherent”=thus maximizing wave energies)
a process that occurs in OPTICAL RESONATOR…where stimulated emission produces a population inversion
What part of the dental laser that is responsible for Amplification/Coherence of light waves?
OPTICAL RESONATOR=”AMPLIFIER”
Collimated Beam+Coherent Energy…responsible for Laser accuracy
Can you affect the MONOCHROMATICITY and COLLIMATION of Laser Light?
(Collimation=non-divergent)
Monochromaticity…can altar WL by passing laser light through “frequency dbling crystals” (i.e. Alexandrite Laser
Collimation…pass laser light through any medium>density than air-see some divergence (i.e. c.f. Lens convergence)
What does LASER acronym stand for?
Light Amplification by Stimulated Emission of Radiation
(atom in a “stimulated” state-stimulated by another quanta of energy…produce 2 “COHERENT quanta of energy”
What are the components of a LASER?
1) Pumping Mech 2) Active Medium
3) Optical Resonator (pumping mech/amplifier)
4) Delivery System 5) Cooling System (“fan”) 6) Control System= foot switch/display panel/safety mech
Name 2 types of Pumping Mechanisms in Dental Lasers?
“EXCITATION SOURCE”=”EXTERNAL ENERGY SOURCE”
1) FRP (Free running pulsed) = rapidly strobing Flashlamp (Er:YAG,Nd:YAG)
2) CW (Continuous Wave) = Electric Induction Coil (Diode or CO2)
* *can be Pulsed or Gated (“Chopped”)
Creates…population inversion within the active medium to cause continued stimulated emission of radiation or “Amplified Light” by mechanism to reflect photons back and forth?
OPTICAL RESONATOR = Pumping Mechanism in Dental Laser
3 Types of ACTIVE MEDIUM in dental lasers
1) Liquid=Excimer Dye
2) Gas=CO2 or Argon
3) Solid
a) YAG or YSGG Crystal
b) Diode Capacitor = Al (or IN), Ga, As
What is the “laser cavity” where light AMPLIFICATION occurs?
OPTICAL RESONATOR=”Amplifier”
What are the components within an OPTICAL RESONATOR?
1) Active Medium=Solid, Liquid or Gas
2) Mirrors (for amplification)
Definition of POPULATION INVERSION=
an environment that produces more atoms with electrons in higher energy orbitals that in the ground state…
LASER LIGHT is MONOCHROMATIC, meaning =
only a specific wavelength is preferentially stimulated from the “excited” atoms
LASER LIGHT is COHERENT, meaning =
the wavelengths of the stimulated photons line up with the passing photons
What type of Dental Laser uses a solid crystal active medium “sandwiched” between silicon wafers”
DIODE LASERS
the crystal is polished to act as mirrors
What type of Dental Lasers have wavelengths in the VISIBLE and NEAR-INFRARED EMS?
DIODE LASERS 800 nm-980 nm
(810,940,980,1064 nm)
What is the range of wavelengths on EMS spectrum for VISIBLE LIGHT?
WL = 400 nm -750 nm
blue-green-orange-yellow-red
EMS SPECTRUM = “The larger the wavelength, the ________ penetration into tissues”…The lower the wavelength, the __________ penetration into tissues”
“LESS”
“DEEPER”
What is the range of wavelengths on EMS spectrum for IONIZING RADIATION?
WL < 400 nm
Name the 3 types of INVISIBLE IONIZING RADIATION?
1) Gamma Rays
2) X-Rays (<100 nm)
3) Ultraviolet (>100 nm)
WAVELENGTH IS INVERSELY PROPORTIONAL TO FRQUENCY = “If Double the Frequency then _________ the wavelength”
“HALVE”…“The shorter the wavelength, the higher the frequency, and vice versa” Wavelength =c/v (frequency)
c=speed of light
PHOTON ENERGY IS INVERSELY RELATED TO WAVELENGTH
E = PLANCKS CONSTANT (h) * c / Wavelength
Photons with greater Energy have ______ Frequency and _______ wavelengths
Higher Frequency and Shorter Wavelengths
Type of Radiation that penetrates oral tissue, can disrupt DNA and overexposure can be harmful=
IONIZING RADIATION (DOES NOT vaporize by thermal radiation)
Type of Radiation that penetrates oral tissue, DOES NOT disrupt DNA and overexposure can be harmful=
NON IONIZING RADIATION (DOES vaporizes by thermal radiation)
What are the 3 types of DELIVERY SYSTEMS in dental lasers, to direct laser energy to target tissue?
LLLT-delivery is by hand-held units
1) Optical Fiber WLs-100 nm-Near IR
2) Art Arm-Sapphire tip (CO2/ErYAG)
* Er:YAG 2 delivery systems
a) Art Arm b) NON-quartz Fiber)
3) hollow-waveguide-Sapphire tip (CO2)
What are the 3 components of OPTICAL FIBERS used in soft tissue dental lasers?
1) CORE=quartz (or silica and/or sapphire)
2) CLADDING-Amine coating (“reflective”)
3) JACKET-silicone rubber
Which type of OPTICAL FIBER has a high -OH content? and therefore good for NEAR INFRARED WL?
Quartz Fiber ("not absorbed in water") w/ Sapphire Tip
"the higher WL (MID/FAR INFRARED) are highly absorbed in water so Quartz Fiber not a good option (ie Erbium and CO2 lasers)"What type of garnet crystal is in a YAG laser?
What is the crystal doped with?
Yttrium Aluminum Garnet
Doped with=Erbium OR Neodynium
What type of garnet crystal is in a YSGG laser?
What is the crystal doped with?
Yttrium Scandium Gallium Garnet
Doped with=Erbium AND CHROMIUM
What determines the NAME of the Laser?
THE ACTIVE MEDIUM b/c it determines the WAVELENGTH being emitted
What are the 3 different ACTIVE MEDIUMS used in DIODE lasers?
1) AL (Aluminum) or IN (Indium)
2) GA (Gallium) 3) AS (arsenic)
Which dental lasers use a CONTINUOUS WAVE Emission mode (Electric Induction Coil)?
1) DIODE 2) CO2 “No colon in the name”
* *PULSED - GATED (“chopped”) is acquired CW = Ultrapulsed/Super-pulsed/Micro-pulsed/Q-switched**
Which dental laser uses a FREE-RUNNING PULSED (FRP) Emission mode?
Er:YAG 2940 nm “Rapidly strobing flashlamp”
Calculate the percentage (%) of “on time” that a laser is actually emitting energy during a pulsed, chopped or gated emission cycle?
DUTY CYCLE = EMISSION CYCLE = “Ratio between time the emitted energy is ON during the pulse”
DUTY CYCLE= Hz X PULSE DURATION = %
(10 Hz X .05 sec = .5 = 50% Duty Cycle) OR
.5 sec PULSE Width/1 sec PULSE DURATION=.5=50%
Amt of time power is actually being admitted during one pulse or “on-time” during one pulse?
PULSE DURATION or PULSE WIDTH
Solve for PEAK POWER (Rate of Energy Flow per pulse)?
if AVG POWER = 1.5 Watts and Duty Cycle = 25%
PEAK POWER=AVG POWER/Duty Cycle
1.5 Watts/.25 = 6 Watts
Solve for AVG POWER (Rate of Energy Flow averaged over 1 full time interval)?
(if Peak Power=6 watts, Duty Cycle = 25%)
AVERAGE POWER=PEAK POWER X DUTY CYCLE
6 Watts X .25 = 1.5 Watts
ALD BASIC TENET=
“Always use the MIN POWER levels necessary in order to achieve your desired clinical result”
Calculate Peak Power for Free-Running Pulsed Mode at 10 Hz and Pulse Duration of 200 microseconds?
if AVG POWER=2 Watts
Duty Cycle=10 X .0002 secs = .002 = .2% (Laser On Time)
Peak Power = 2 Watts / .002 = 1000 Watts
Laser is off 99.8 % of the time - TRT
The total Energy delivered for a laser procedure is measured with what? How is power measured (the rate of energy conversion or transfer with respect to time)?
Energy=Joules (milliJoules)=”Ability to do work”
Power=Watts=Joules/sec=”Rate of doing work”
Energy=Power (Watts) X Time (secs)=Joules
Amount of POWER delivered to the tissue surface area, at the point of tissue interaction?
POWER DENSITY=”INTENSITY”=mW/cm2=mJ/sec per Area (affected by Energy+Exposure Time+spot size)
Amount of ENERGY emitted per unit area at the point of tissue interaction, per tissue surface area?
ENERGY DENSITY=FLUENCE=mJ/cm2
This type of Laser-Tissue Interaction has no effect on Target Tissue?
1) REFLECTED Laser Photonic Energy
***TRANSMITTED (and scattered) Energy-depends-can have an indirect effect; Used in caries detection
This type of Laser-Tissue Interaction effects Target Tissue depending on Laser WL, Pigmentation,H2O,Tissue type
ABSORPTION= 1) Photothermal 2) Photochemical (curing lights) 3) Photoaccoustic (Er Hard tissue lasers)
4 types of compounds in dental tissues that ABSORB Laser Light and are called “Chromophores”?
1) H2O 2) Melanin 3) Hb and OxyHb 4) cOH-“carbonated Hydroxyapatite
Measurement of the amt of absorption of Laser Energy/per unit area?
ABSORPTION COEFFICIENT (higher means greater absorption of a WL’s photonic energy w/i chromophore)
Chromophore Content of Dental Tissues?
SOFT TISSUE H2O=72-77% Hb=3-4% Melanin=1-2% ENAMEL cHA=95% H2O=4%
BONE cHA=60-70% H2O=10-20%
Which Laser WL’s delivers NON-ABLATIVE Photothermal (non-contact) Energy (treat oral ulcers/herpetic lesions)?
Near IR=Diode and Nd:YAG (uninitiated laser tip emits “pure radiant energy”=Radiation=Thermal “Heat” Transfer)
TRUE LASER EFFECT
Near IR Laser has less collateral thermal tissue damage - soft tissue surgeries (“thermal ablation”)?
1064nm Nd:YAG Chromo=Hb/Melanin/ Granulation Tissue=FRP allows tissue relaxation time, more time to cool
Which Laser WL is absorbed by Porphryin rings in bacteria, causing Laser Fluoresence?
DiagnoDent=655 nm Diode
***377 nm Solid
What is the KEY to maximizing the Laser-Tissue Interaction (“ABSORBANCE OF LASER LIGHT”)?
Choose the LASER WL that matches the CHROMOPHORE OF THE TARGET TISSUE
List the PHOTOBIOLOGICAL effects of LASERS?
1) PHOTOTHERMAL=temp effects (LAPT,Ablation,Cautery)
2) PHOTOACCOUSTIC=Disruption,Plasma Effect
3) PHOTOCHEMICAL=PDT,+chemical bonds (curing lights)
4) BIOSTIMULATION=+collagen,wound healing,analgesia
5) Laser-Induced Fluorescence=caries detection
Laser Tissue Interaction, VAPORIZATION, occurs at what temperature (in Celsius)?
100 degrees Celsius (Tissue Welding=70-90 degrees Celsius, > 200 degrees Celsius=Carbonization)
Laser-Assisted Perio occurs at what temperature, in Celsius, a “photothermal” effect on tissue”?
> 60 degrees Celsius=protein denaturation + coagulation
can inactivate some non-sporulating bacteria at 50 C
Do Near IR Lasers (Diodes/Nd:YAG/Nd:YAP) ablate soft tissues by Thermal Ablation or Photothermal Ablation?
THERMAL ABLATION by Thermal Conduction=”Hot Tip”
NOT PHOTOTHERMAL ABLATION
Thermal transfer (heat generated by Lasers) can occur in 3 ways?
1) CONDUCTION - direct contact of heat w/ target tissue
2) CONVECTION - Heat moved in lg volumes near target
3) RADIATION - non-contact waves absorbed by target from source = “TRUE LASER EFFECT”
In Laser-Tissue Interaction, The BIOLOGIC EFFECT of Lasers depends on?
1) ENERGY DENSITY 2) TISSUE TYPE 3) WL+EMISSION MODE 4) Duration of Exposure + Amt of Cooling
Time during which the target tissue is allowed to cool, the time that the laser energy is OFF during a pulse?
THERMAL RELAXATION TIME
Characteristics of Target Tissue?
1) Tissue Profile=hypertrophic/fibrotic or thin/friable
2) Degree of Melanin Pigmentation
3) How much keratinized tissue?
What does LAPT stand for?
Indications for LAPT 1) Bleeding on Probing
2) Calculus 3) Attachment Loss
Laser Assisted Periodontal Therapy…
LA/Ultrasonic scaler w/ antimicrobial agent/light hand scaling/use Laser to removed dz epithelial lining and for coagulation-bacterial reduction
What are the results of Laser use in Periodontal Therapy (LAPT), after SR/P?
1) Reduction in bacterial flora
2) up to 97% reduction in bleeding when probing
3) decreased pocket depth
4) overall better gingival health
What is most important in performing LAPT?
Diode CW .5 Watts 12-15 secs/pocket site
Nd:YAG Pulsed 1.5 Watts (30 mJ,50 Hz) 40 secs/site
CO2 10,600 nm 2 Watts (40 mJ,50 Hz) 30 secs/tooth
1) Lase w/i 2 mm of pocket depth 2) place fiber in sulcus before firing/angle away from tooth 3) keep fiber moving
4) probing depths-Pre-op/3 mo post op
* *Nd:YAG-no need to condition fiber tip
POWER DENSITY (Watts/cm2) can be changed by…
1) changing the power setting (Watts)
2) changing the spot size/spot dia
3) use a lense to change spot size
4) moving tip toward or away (defocusing)
Laser ablation of GRANULATION tissue require more or less power?
Less Power (can defocus beam to decrease power) (Nd:YAG 1064 nm most effective on granulation tissue)
What is the Power Density Effect-Inverse Square Rule?
Decrease spot size 1/2=2 (squared)=4X increase in power
DIVERGENCE=How much does energy decrease when laser light diverges from the delivery system?
@ 1 mm out of contact=<=44% energy decrease
CO2-Optimal Distance=Focal Spot=3.5 mm-10 mm
Non-contact lasers, Hollow Waveguides and Articulated Arms minimize power loss due to DIVERGENCE by?
FOCUSING LENSES (ie 7 mm from tip) minimize divergence and resultant decrease in energy
How do non-contact laser systems achieve coagulation/hemostasis?
PHOTOTHERMAL CONVECTION- “Hot” effect” by defocusing beam - “Radiant Heat” > 60 degree C
(Contact Lasers-by Thermal Conduction-seals BVs)
What are the sizes of Sapphire Tips used Lasers wih hollow-wave guide or articulated arm delivery systems?
Sapphire Tips sizes = 200 microns-1300 microns
- Sapphire is a lower OH fiber*
- **Diode Sapphire Tip sizes=200 microns-1200 microns
The DUTY CYCLE of a 810 nm laser w 1 sec pulse?
1 sec pulse-emitted energy is ON=.5 sec and OFF=.5 sec
DIVIDE….5 sec PULSE WIDTH/1 sec PULSE DURATION =50% DUTY CYCLE
What is a cold laser?
Very short WL UV lasers that react on a molecular basis NO PHOTOTHERMAL interaction. 1) ArF 2) XeCl
What is the difference between Hard Lasers (high power) and Soft Lasers (low power)?
Soft Lasers- LOW POWER lasers interact INDIRECT with biological tissues 1) biostimulation 2) PDT
3) Caries detection 4) aiming beam
What is the laser wavelength range for Photobiomodulation (PBM or LLLT) Soft Lasers?
600nm-1060 nm (HeNe 633 nm Vet Med) milliWatts
1) BIOSTIMULATION (Primary Therapy)
2) PDT-Photodynamic Therapy (Secondary Therapy) 3) Caries Detection (680 nm)
What are the results of BIOSTIMULATION with a Soft Laser (PBM/LLLT)?
Sm doses over periods of time are more effect than closely sched txmts at higher doses
1) +local blood flow,macrophages,fibroblasts
2) -pain receptor mechanisms/+”feel good factors”
3) Used post-surgery, TMD,Trigeminal neuralgia, hypersensitivity, herpes, apthous ulcers
What happens at the cellular level in PBM/LLLT Soft Laser Therapy?
Light Photons-absorbed by the Mitochondria of the cell…alters cell membrane/permeability…+mRNA synthesis 1) Biostimulation 2) Anti-inflammation 3) Analgesic
Hard Tissue WLs?
Argon 488-513nm (visible/bleaching/curing)
Diode 800-980 nm Nd:YAG 1064 nm Er,Cr:YSGG 2790 nm Er:YAG 2940 nm CO2 9300 nm
Which wavelengths can cause more Edema due to deeper penetration into tissues?
Shorter WLs 1) Diode 2) Nd:YAG
What was the first dental WL available?
Nd:YAG 1064 nm Hb/Melanin
1) dental sensitivity to close dentinal dentubles 2) Endo- remove pulpal tissues…depth of penetration is 2 mm, lase 2 mm < working length (apex)
Why do we use the minimum power to reach treatment objective?
TEMP to underlying tissue is related to POWER
No difference in cutting efficiency when increase power, temp increases as power increases/Coagulation starts @ 50 Hz-100 Hz start cutting at 50 Hz, when increased coagulation is needed, increase to 100 H
Which laser can cause problems with Edema in periostal bone if use too much power?
Nd:YAG too much power, too much heat…if see carbonization too much power=”hot tip”-depth of penetration is too much…have to move quickly, don’t use too long
If use Nd:YAG on tooth structure, what happens?
Depth of Penetration is too much - too much heat generated and transmittance of energy to pulpal tissues
Why aren’t Erbium pulsed lasers good for use in soft tissue surgeries?
Cuts vessel-No coagulation…microsecond pulse so fast, no heat generated (which is good for pulp when cutting hard tissues)
What is the temp of the H2O in Enamel/Dentin heated up Er:YAG lasers?
Walls of Prep=800-1000 degrees Celsius
(Need to keep Pulp Temp rise <4 C)
similar to HS handpiece with H2O
How do higher WL lasers (Er:YAG, Er,Cr:YSGG, CO2 affect hydroxyapatite?
CO2 @ 9.6 micrometer=8000=Absorp Coeff
(Er:YAG @ WL=2.94 micrometer=only 770 Absorp Coeff)
Higher WL lasers change carbonated cHA to HA-more acid resistant form (can add Fl ions to change HA to Fluorapatite, increases acid resist even more)
(400-900 C) Er:YAG Er,Cr,:YSGG CO2 lasers
What is the melting Temp of Enamel?
1000 degrees Celsius (Er:YAG laser heats Enamel to 400-900 degrees Celsius-cHA converts to HA-“stronger”)
Why is Er:YAG laser better with bone surgery than high speed drill? (for Bone surgery-use Nd:YAG or CO2)
No smear layer when using laser…Rotary Drill creates “smear layer” and if not removed creates sig inflammation post-operatively (pain)…plus thermal cracking
What Laser WLs can be used for Laser Bleaching?
1) Argon=200 mJ (low power/best choice) 2) Nd:YAG low power=100 mJ/10 Hz 3) CO2 low power=1 Watt CW
Which Laser has selective absorption in bacteria only (Calculus or carious lesions)?
doesn’t ablate healthy Dentin/Cementum
Alexandrite=377 nm w/ Frequency Doubled
*selective Calculus/Caries removal w/o harm to Cementum or Dentin (explodes bacteria to remove)
What is PHOTOTHERMAL ABLATION seen in Med/Far IR Lasers?
LIGHT ENERGY is changed into HEAT during ABSORPTION by the target tissue (H2O=chromophore)
What is the tissue-interaction that occurs when Mid IR Lasers (Erbiums) are used in soft tissue surgeries?
PHOTOTHERMAL vaporization of H2O=100 degrees C
What is the tissue-interaction that occurs when MID/FAR IR Lasers are used in soft tissue surgeries?
PHOTOTHERMAL ABLATION ("vaporization") of H2O in soft tissue (also vaporizes H2O in enamel,dentin,bone)
**Heals by secondary intention**Does the explosion of H2O in hard tissue by Erbium Lasers generate heat?
No-minimal heat transfer to surrounding tissue…water spray from handpiece acts as heat sink…keep tip moving
(Pain w/ Erbium would be from heat/close to pulp)
Why does Erbium WLs have preferential selectivity for dental disease?
Dental Caries ("carious tooth structure") >H2O content than Healthy Dentin > H2O content than Enamel
**Erbiums remove the smear layer***How is a CO2 laser @ 9300nm WL different than Erbiums?
- CW that is Micropulsed=<10,000 Hz/Pulse Width=300-100 msecs/HIGH ENERGY DENSITY LEVELS=10-20 J/Cm2
- Bacteriocidal (Erbiums only reduce bacteria in soft tissue)
- Char-free Ablation-heal by secondary intention
What is the 3 gases in the active medium of CO2 Lasers?
1) CO2 2) Nitrogen 3) Helium
Diff between Isotopic CO2 Laser @ 9,300 nm and CO2 Laser at 10,600 nm? (Both=char-free soft tissue ablation)
(Both=low level of penetration=50-100 microns/pulse)
9,300 nm = Hard Tissue removal (Solea)
10,600 = Soft Tissue surgeries (Light Scalpel)=H2O chromophore=spot size=100,200,500 microns
Which NEAR IR Laser can be used for new LANAP (bone regeneration) procedure (Alternative to Perio surgery)?
Nd:YAG LANAP=”Laser Assis New Attach Procedure”
*cementum-mediated new PDL attachment to root surface in the absence of long junctional epithelium
NEAR IR Laser-used for Endo (retreatment, removal of files/canal obstructions) and Peri-implantitis Txmt?
Which NEAR IR Laser is used in canal -bacteria?
Nd:YAP (“Perovskite”) 1340 nm FRP laser/Fiber DIRECT-contact-THERMAL ABLATION of soft tissues
Can use to ablate Fx endo file*
Er,Cr,:YSGG=radial tip-antimicrobial-dentinal tubules
How is PDT (Photo Dynamic Therapy, Soft Laser @ 630 nm) with SOFT LASERS used for Cancer Therapy?
*Selective malignant tumor destruction-low WL laser light to ABLATE TUMOR (IV injection of haemoporphorin derivative, absorbed by tumor site then expose site to laser light, nascent O2 radicals released)
BIOSTIMULATION (PBM therapy)-what is the Fluence (Energy Density) levels in the therapeutic window (“Arndt-Schultz Curve”)? 540 nm-830 nm
Cell Stimulation >2 J/cm to 6 J/cm2 < Cell Inhibition
- HIGHER FLUENCE=6-10 J/cm2=ANTI-INFLAMMATORY
- HIGHEST FLUENCE=20-50 J/cm2=ANALGESIC (“acute”)
LLLT/PBM applications in Dentistry?
soft laser or cold laser < 1 Watt of energy
Post-surgery Healing, Bone/Nerve Regeneration, Paresthesia, Pain, Dentin Hypersensitivity, Herpes, Mucositis, TMD, Trigeminal Neuralgia
Applying or systemically introducing a material that in the presence of laser energy will be transformed into a useful material/create the release of singlet O2 that will cause disruption of cellular membrane, is called what?
PHOTODYNAMIC THERAPY (PDT)=Photo-activated Medication Delivery=Photosensitizer agents+O2+ LLL Light=ROS (Reactive O2 Species)=Microbial reduction or Selective Destruction of Tumors
What are uses of PDT (photodynamic therapy) in dentistry? “photo-sensitive liquid injected into body …selectively accumulates within unhealthy cells”
Localized Osteitis, Perio Dz, Herpes/Apthae, mucositis, Peri-implantitis/Perio-mucositis, Endo (-bacteria), post-invasive tooth prep and oral cancer (Photophrin dye)
Which visible (“green” Laser @ 532 nm is used for bleaching (“red alkaline gel”), photoablation and photocoagulation?
KTP LASER = FREQ DOUBLED (2X) Nd:YAG Laser …directed through a POTASSIUM-TITANYL-PHOSPHATE CRYSTAL (“less heat”) PERIOENDO*PBM
Which CO2 laser can be used to altar the surface structure of tooth enamel to render it resistant to caries?
9600 nm-Absorp Coeff=8000 (ENAMEL REMODELING)
*changes to enamel surface occur w/o harming pulp
The distance between the APICAL END of the GINGIVAL SULCUS to the CREST of ALVEOLAR BONE is called?
Keep finish lines approx .5 mm subgingival*
Biologic Width of Attachment (BWA)APPROX 2.79 mm (1.77 mm-2.43 mm?)…allow 3 mm (BWA+Connective Tissue Attach+Junct Epi+Gingival Sulcus)
LASER Excisional Biopsies Technique…
- 45 degree angle towards tissue base/slight tension
- Biopsy should include normal tissue margins
- do not carbonize lesion/biopsy report state used laser
APTHOUS ULCER (HERPETIC LESION) Technique…
- can use most WLs (CO2s/Erbiums-no H2O spray)
- *should take 1-2 min total…poss need anesthetic?
- start at CW=.5 W around lesion border for 30 secs
- each 30 sec pass increase power until evap exudate
- Uninitiated Fiber=2mm out of contact=Radiant Heat”
What is the most efficient way to cut enamel with Hard Tissue Lasers?
- Tip should be parallel to the direction of the enamel rod exit @ target interface-DO NOT aim into groove
- Prep will be spoon or bowl shaped
- Bevel Enamel cavosurface-seal photochemical bond
How to achieve LASER ANALGESIA?
Physical Effects: 1) Occlude narrow dentinal tubules
2) Evaporation of intra-tubular transmitter fluid
- Defocus Fiber Tip (Erbium 1 cm for 1-2 min)
- Reduce Power
- Increase H2O
- Increase Frequency (+Hz)
LASER ANALGESIA using GATE CONTROL THEORY…
Lasers at Lower Power/Frequencies…
+C Fibers (larger)=increase inhibitory neuron influence…GATE IS CLOSED to “pain perception
*A beta Fibers (smaller)=reduce inhibit neuron influence …OPENS GATE to “pain perception”
Effect of Er:YAG on Pulp vs HS drill (in study of rats)?
*Mid IR Laser pulp chamber temp - < 5 degrees C
Er:YAG is less damaging to pulp and faster rate of repair (calictonin gene-related peptide immunoreative fibers)
Treatment Technique for Peri-implant Mucositis…
PD < 4mm w/o bone loss (BOP/SOP)
- Soft Tissue Incision/uncovering implant (most WLs)
* Osseous Tissue Prep - use Erbium Lasers (want less hemostasis-improved perfusion)
Which laser is absorbed by camphor quinone?
ARGON Laser 488-512 nm Visible/CW/Fiber(“contact”)
1) cure composite resin 2) Bleaching 3) Melanin/Hb (good scalpel/hemostasis)
Advantages of Laser use in non-Contact Mode?
1) Defocused beam reduces power density
2) Greater area of tissue exposed to beam
3) Greater control of Laser-Tissue Interaction:LOWER
RISK OF DEEP PENETRATION OF LASER ENERGY
Disadvantages of Laser use in non-Contact Mode?
1) Defocused beam reduces power density
2) Greater area of tissue exposed to beam
3) GREATER RISK OF COLLATERAL DAMAGE
4) May mimic LLLT action
SUMMARY POINTS FOR LASERS IN DENTISTRY:
OPTIMAL EFFECTS only occur with energy ABSORPTION by target tissue
- Delivery modes can influence power levels
* Laser-tissue interactions obey the laws of optical physics
IDEAL LASER TISSUE INTERACTION SUMMARY:
CHOOSE CORRECT WL FOR MAXIMUM INTERACTION
*Use MINIMUM POWER to achieve desired tissue interaction *Expose tissue to laser light for MINIMUM TIME to achieve interaction * Achieve MAXIMUM THERMAL RELAXATION to prevent collateral thermal damage *Prevent unwanted damage episodes
LASERS USED IN ENDO PROCEDURES
1) Nd:YAG - remove files/disinfect canals 2) Nd:YAP
2) Diodes - Disinfect canals 3) Er,Cr:YSGG
ADV of Laser Excision vs Scalpel
Less Post-op pain but “NOT QUICKER” healing
Accuracy/Ease of Access/No bleeding (depends on WL)/No sutures/Reduced Inflammatory response/Reduce bacterial contamination-“more sterile”
Tissue Reaction with NO CHANGE IN WL
1) REFLECTION 2) SCATTERING 3) TRANSMISSION
What is Q-SWITCHING (“Giant Pulse Formation”)?
Controlled Pulse vs “Free Running Pulses w/ Flashlamps
“Controlled Pulse”…allows a laser to produce one High Very High Power Peak per “pulse”…(ie Selective ablation of calculus, Lasers used to remove TATOOS)
CONTENTS OF PLUME?
toxic gases/vapors, polycyclic aromatic hydrocarbons and particulates (carcinogens, mutagens, irritants,fine dusts,blood fragments,bacterial spores and viruses
What causes Photokeratitis?
UV rays causes “sunburn” to CORNEA,CONJUNCTIVA
What are examples of PHOTOACOUSTIC Effects?
…localized vaporization of tissue or fluids …then a rapid increase in pressure produce by VAPORIZATION-creates mechanical shock waves, causing disruption/damage
What is HeNe (“gas/DC electrical charge”) laser used for?
RED=632.8 nm or GREEN=543.5 nm
1) LLLT
2) Aiming beam for dental lasers
What does the FLUORESCENCE in caries detection mean?
…when exposed to light-also “emits light” (the WL of emitted light is LONGER that the ABSORBED LIGHT)
BEST PRACTICE in Laser Dentistry includes the following:
1) Knowledge of the laws of Biophysics and Safety
2) Application of knowledge and Clinical Skill
