LASERS in endodontics.ppt

 Introduction
 History
 Fundamentals of Lasers
Lasers Physics
Laser Delivery Systems and Emission Modes
Laser Interaction with Biological Tissues
Laser Energy and Tissue Temperature
 Types of Lasers
 Application of lasers in conservative dentistry and endodontics
 Laser saftey measures
 Advantages and disadvantages
 Conclusion
 Refrences

 Dentistry has changed tremendously over the past
decade to the benefit of both the clinician and the
patient.
 One newer technology that has become increasingly
utilized in clinical dentistry is that of the laser.
 The use of lasers in dentistry has increased over the
past few years.
 Because of their many advantages, lasers are indicated
for a wide variety of procedures.
 Initially introduced as an alternative to the traditional
halogen curing light, the laser now has become the
instrument of choice, in many applications.

 In 1917 Albert Einstein postulated the theoretical
foundation of laser action, stimulated emission of
radiation.
 In 1953 Charles H. Townes invented the MASER
(microwave amplification by stimulated emission of
radiation), by means of ammonia gas and microwave
radiation.It was developed as an aid to communication
systems and time keeping (the ‘atomic clock’).
 In 1960, Theodore Maiman’s ruby laser became the first
working laser in history.
 In the 1960’s, Dr. Ali Javan invented the first gas laser
with Helium Neon.
 The carbon dioxide laser was successfully shaped by
Kumar Patel in 1964.

 Over the years, Goldman and Other researchers
documented the ability of various types of lasers to
cut, coagulate, ablate and vaporize biologic tissues.
 Historically, the first lasers to be marketed for intra
oral use generally were CO2 lasers - authorized by
FDA. In 1990, the FDA cleared it for intraoral soft
tissue surgery .
 A pulsed Nd: YAG laser developed by Myers and
Myers, recognized as the first laser designed
specifically for general dentistry.

The word LASER is an acronym for Light
Amplification by Stimulated Emission of
Radiation. A brief description of each of
these five words will begin to explain the
unique qualities of a laser instrument.

 Light is a form of electromagnetic energy that behaves as
a particle, and waves. The basic unit of this radiant
energy is called a photon.
 The light emitted from a laser is monochromatic, that is,
it is of one color/wavelength. In contrast, ordinary white
light is a combination of many colors (or wavelengths) of
light.
 Lasers emit light that is highly directional, that is, laser
light is emitted as a relatively narrow beam in a specific
direction. Ordinary light, such as from a light bulb, is
emitted in many directions away from the source.
 The light from a laser is said to be coherent, which
means that the wavelengths of the laser light are in phase
in space and time. Ordinary light can be a mixture of
many wavelengths.
 Collimation: is the beam having specific boundaries,
which ensures that there is constant size and shape of
the beam emitted from the laser cavity

1. Many wavelengths
2. Multidirectional
3. Incoherent
1. Monochromatic
2. Directional
3. Coherent

 Amplification is the part of a process that
occurs inside the laser. Indentifying the
components of a laser instrument is
important to understand how light is
produced.

 Active Medium
The active medium may be solid crystals such as ruby or
Nd:YAG, liquid dyes, gases like CO2 or Helium/Neon, or
semiconductors . Active mediums contain atoms whose
electrons may be excited to a metastable energy level by an
energy source.
 Excitation Mechanism
Excitation mechanisms pump energy into the active medium by
one or more of three basic methods; optical, electrical or
chemical.
 High Reflectance Mirror
A mirror which reflects essentially 100% of the laser light.
 Partially Transmissive Mirror
A mirror which reflects less than 100% of the laser light and
transmits the remainder.
 Cooling system, focusing lenses, and other controls complete
the mechanical components

 The term ‘‘stimulated emission’’ has its basis in the
quantum theory of physics.
 A quantum, the smallest unit of energy, is absorbed by the
electrons of an atom or molecule, causing a brief
excitation; then a quantum is released, a process called
spontaneous emission. This quantum emission, also
termed a photon, can be of various wavelengths because
there are several electron orbits with different energy levels
in an atom.

 Additional quantum of energy travelling in the field of the
excited atom that has the same excitation energy level
would result in a release of two quanta, a phenomenon
he termed stimulated emission.
 The energy is emitted, or radiated, as two identical
photons, travelling as a coherent wave.
 These photons are able to energize more atoms, which
further emit additional identical photons, stimulating
more surrounding atoms.

 If the conditions are right, a population inversion
occurs, meaning that a majority of the atoms of
the active medium are in the elevated rather than
the resting state.
 The mirrors at each end of the active medium
reflect these photons back and forth to allow
further stimulated emission, and successive
passes through the active medium increase the
power of the photon beam.This is the process of
amplification.
 There is some heat generated in the process, and
the optical cavity must be cooled. The parallelism
of the mirrors insure that the light is collimated.
 One of the mirror is selectively transmissive,
allowing light of sufficient energy to exit the optical
cavity

 Radiation refers to the light waves produced by the laser
as a specific form of electromagnetic energy.
 The very short wavelengths, those below approximately
300 nm, are termed ionizing.
 All available dental laser devices have emission
wavelengths of approximately 0.5 µm (or 500 nm) to 10.6
µm (or 10,600 nm).
 They are therefore within the visible or the invisible
infrared nonionizing portion of the electromagnetic
spectrum and emit thermal radiation.

 Some instruments use small, flexible glass fibers to deliver
energy, while others use more rigid, tube-like devices.
 The shorter wavelength instruments, like argon, diode, and
Nd:YAG, have small, flexible glass fiber-optic delivery systems,
with bare fibers that are usually used in contact with the target
tissue.
 The technical challenges of conducting the longer erbium and
carbon dioxide wavelengths are demanding, and some
manufacturers have chosen to use semiflexible hollow wave
guides or rigid sectional articulated arms to deliver the laser
energy to the surgical site.
 Some of these systems use additional small quartz or sapphire
tips, that attach to the operating handpiece.

 The first is continuous wave, meaning that the beam is emitted
at only one power level for as long as the operator depresses
the foot switch.
 The second is termed gated-pulse mode, meaning that there
are periodic alternations of the laser energy, much like a blinking
light. This mode is achieved by the opening and closing of a
mechanical shutter in front of the beam path of a continuous
wave emission.
 The third mode is termed free-running pulsed mode,
sometimes referred to as "true pulsed." This emission is unique
in that large peak energies of laser light are emitted for a short
time span, usually in microseconds, followed by a relatively long
time in which the laser is off. The timing of this emission is
computer controlled, not mechanically controlled as in a gated
pulse device

 Laser light can have four different interactions with
the target tissue, depending on the optical
properties of that tissue. Dental structures have
complex composition, and the four phenomena
which occur together in some degree are relative to
each other.
These four interactions are
 Absorption
 Transmission
 Reflection
 Scattering

 The first and most desired interaction is the Absorption of
the laser energy by the intended tissue. The amount of
energy that is absorbed by the tissue depends on the
tissue characteristics, such as pigmentation and water
content, and on the laser wavelength and emission mode.
 Water, the universally present molecule, has varying
degrees of absorption by different wavelengths.
 Dental structures have different amounts of water content
by weight. A ranking from lowest to highest would show
enamel (with 2% to 3%), dentin, bone, calculus, caries,
and soft tissue (at about 70%).

 Hydroxyapatite is the chief crystalline component of dental
hard tissues and has a wide range of absorption
depending on the wavelength.
 Water, which is present in all biologic tissue, maximally
absorbs the Erbium wavelengths, followed by CO2
wavelength.
 Conversely, water allows the transmission of the shorter
wavelength lasers, diode, and Nd:YAG.
 Hydroxyapatite crystals readily absorbs the CO2
wavelength, and, interacts to a lesser degree with Erbium.
 It does not interact with the shorter wavelengths. .

 The second effect is Transmission of the laser
energy directly through the tissue with no effect
on the target tissue, the inverse of absorption.
 This effect is highly dependent on the
wavelength of laser light.
 Water, for example, is relatively transparent to
the shorter wavelengths like argon, diode, and
Nd:YAG, whereas tissue fluids readily absorb
the erbium family and CO2 at the outer surface,
so there is little energy transmitted to adjacent
tissues.

 The third effect is Reflection, which is the beam
redirecting itself off of the surface, having no effect
on the target tissue.
 A caries-detecting laser device uses the reflected
light to measure the degree of sound tooth
structure.
 The laser beam generally becomes more divergent
as the distance from the handpiece increases.
 However, the beam from some lasers can have
adequate energy at distances over 3mtrs.

 The fourth effect is a Scattering of the laser
light, weakening the intended energy and
possibly producing no useful biologic effect.
 Scattering of the laser beam could cause heat
transfer to the tissue adjacent to the surgical
site, and unwanted damage could occur.
 However a beam deflected in different
directions is useful in facilitating the curing of
composite resin or in covering a broad area.

 There are five important types of biological
effects that can occur once the laser photons
enter the tissue:
 Fluorescence,
 Photothermal
 Photodisruptive
 Photochemical
 Photobiomodulation.

 Fluorescence happens when actively carious tooth
structure is exposed to the 655nm visible
wavelength of the Diagnodent diagnostic device.
The amount of fluorescence is related to the size of
the lesion, and this information is useful in
diagnosing and managing early carious lesions.
 Photothermal effects occur when the laser energy
is absorbed and heat is generated. This heat is
used to perform work such as incising tissue or
coagulation of blood. Photothermal interactions
predominate when most soft tissue procedures are
performed with dental lasers. Heat is generated
during these procedures and great care must be
taken to avoid thermal damage to the tissues.

Photodisruptive effects (or photoacoustic)
 Hard tissues are removed through a process known
as photodisruptive ablation.
 Short-pulsed bursts of laser light with extremely
high power interact with water in the tissue and
from the handpiece causing rapid thermal
expansion of the water molecules.
 This causes a thermo-mechanical acoustic shock
wave that is capable of disrupting enamel and bony
matrices quite efficiently.
 The pulsed Erbium laser ablation mechanism of
biological tissues is still not completely understood
but erbium lasers high ablation efficiency seems to
result from these micro-explosions of overheated
tissue water in which their laser energy is
predominantly absorbed.

 Photochemical reactions occur when photon energy
causes a chemical reaction.
 Photobiomodulation or Biostimulation refers to
laser’s ability to speed healing, increase circulation,
reduce edema, and minimize pain. Biostimulation is
used dentally to reduce postoperative discomfort and to
treat maladies such as recurrent herpes and aphthous
stomatitis.

Tissue temp
in
Observed effect Application
37-50 Hyperthermia Above normal temp
60 - 70 Coagulation -Proteins
denaturation
-Tissue whitens
- Remove
diseased
granulation
tissue
- Haemostasis by
contraction of
vessel wall

Tissue
temp in
Observed
effect
Application
70-80 Welding Cause collagen
molecule helical
unfolding and
interwining with
adjacent
segments
Adherence of layer-
stickiness
100-150 Vaporization
Ablation
Liquid - steam -Excision of soft tissue
commences

Tissue temp
in
Observed
effect
Application
>200 Carbonization Dehydrated & burn
in presence of air
--carbon (heat sink)

According to the physical construction of
the laser
 Gas lasers; e.g. Argon, Helium-neon, CO2
 Liquid lasers; e.g. Dyes
 Solid state: e.g. Nd:YAG, Er,Cr:YSGG,
Er:YAG
 Semiconductor diode: e.g. Diode

 According to their potential of
causing biological hazard
Class Risk Example
I
Fully enclosed system Nd:YAG laser welding system
used in a dental laboratory
II
Visible low power laser Visible red aiming beam
protected by the blink reflex
surgical laser
IIIa
Visible laser above 1 milliwatt No dental examples
IIIb
Higher power laser unit
(up to 0.5 watts) which may or may not be visible.
Direct viewing hazardous to the eyes
Low power (50 milliwatt) diode
laser used for biostimulation
IV
Damage to eyes and skin possible. Direct or
indirect viewing hazardous to the eyes
All lasers used for oral surgery,
whitening, and cavity
preparation

According to wavelength used
LASER TYPE WAVELENGTH WAVEFORM
CO2 10.6 µm
Gated (or interrupted) /
continuous
Nd:YAG 1.064 µm
Pulsed
Er:YAG 2.94 µm
Pulsed
Er,Cr:YSGG
2.78 µm Pulsed
Argon
457-502 nanometers Pulsed/ continuous
Holmium:YAG 2.1 µm Pulsed
Diode 904 µm Pulsed continuous

CO2 Lasers
 The CO2 laser is a gas-active medium laser that
incorporates a sealed tube containing a gaseous mixture
with CO2 molecules pumped via electrical discharge
current.
 The light energy, whose wavelength is 10,600 nm and it is
delivered through a hollow tube-like waveguide in
continuous or gated pulsed mode.
 This wavelength is well absorbed by water, second only to
the erbium family.
 It can easily cut and coagulate soft tissue, and it has a
shallow depth of penetration into the tissues, which is
important when treating mucosal lesions.
 In addition, it is useful in vaporizing dense fibrous tissue.

 The laser energy is conducted
through the waveguide and is
focused onto the surgical site in a
non-contact.
 The continuous wave emission
and delivery system technology of
CO2 devices limit hard-tissue
applications because
carbonization and crazing of tooth
structure can occur due to the
long pulse duration and low peak
powers.

Applications of CO2 lasers
 Soft tissues incision and ablation
 Gingival troughing
 Esthestic contouring of gingiva
 Treatment of oral ulcers
 Frenectomy and gingivectomy
 De-epithelization of gingival tissues during
periodontal regenerative procedures.
 Very effective for ablation and vaporization of
leukoplakia and dysplasia.

Advantages of CO2 lasers
 Excellent hemostasis; offering the dentist a clear
operating field and allowing for instant visual
feedback.
 Quick and efficient tissue removal: causing
negligible concern about subsurface tissue
damage, as the effect is on the surface only.
 Postoperative pain usually is minimal to none.
Disadvantages of CO2 lasers
 Delayed wound healing
 Lack of tactile feedback

 Nd:YAG has a solid active medium, which is a
garnet crystal combined with rare earth
elements yttrium and aluminum, doped with
neodymium ions.
 The pumping mechanism is a flashlamp .
 They operate at an infrared wavelength of
1064 nm in a high intensity pulsed waveform.
 Photothermal interaction predominates and
the laser energy here can penetrate deeply
into tissues.
 These instruments operate only in a free-
running pulsed mode and feature small
flexible bare optic fibers that can contact
tissue
 Contact and non-contact mode are both
utilized depending on the procedure being
performed .

 Nd:YAG laser energy is slightly absorbed by dental
hard tissue, but there is little interaction with the
sound tooth structure, allowing soft tissue surgery
adjacent to the tooth to be safe and precise.
 Pigmented surface carious lesions can be
vaporized without removing the healthy surrounding
enamel.
Applications of Nd:YAG laser
 Soft tissue applications
 Esthestic contouring of gingiva
 Frenectomy
 Gingivectomy
 Removal of incipient enamel caries

Advantages of Nd:YAG laser
 Offers good hemostasis: during soft tissue procedures,
which facilitates a clear operating field.
Disadvantages of Nd:YAG laser
 Greatest depth of penetration of all the available dental
surgical laser systems, which means that tissues under
the surface are exposed to laser energy.
 The diminished localization of the energy on the tissue
surface makes vaporization of soft tissue with an Nd:YAG
laser slower than with the better absorbed laser
wavelengths, such as those produced by CO2 laser.
 Pulpal damage (such as denaturation and disruption of the
vascular and neural tissues) from this laser can occur, and
is associated with a decrease in pulpal function( i.e
sensitivity)

Erbium Lasers are two distinct wavelengths that use erbium,
and these two lasers are discussed together because of their
similar properties. It includes:
 Erbium:YAG
 Erbium, chromium:YSGG
 The delivery systems of Er:YAG instruments are a hollow wave-
guide or a fiberoptic bundle, whereas Er,Cr:YSGG only use
fiberoptics.
 Both wavelengths are emitted in a free-running pulsed mode.
 The erbium lasers are truly hard and soft tissue capable and
have the most FDA clearances for a host of dental procedures.
 Photothermal interactions predominate in soft tissue procedures
and are photodisruptive in hard tissue procedures, though both
types can occur to varying degrees in any procedure

The Er:YAG laser operates at a wavelength of 2.94µm .
 It has an active medium of a solid crystal of yttrium,
aluminum garnet that is doped with erbium.
Applications of Er:YAG laser
 Caries removal
 Cavity prepration in both enamel and dentin
 Preparation of canals
Advantages of Er:YAG laser
 Clean sharp margins in enamel and dentine
 Negligible depth of energy penetration
 Is antimicrobial in nature when used in root canal and root surfaces
 Less discomfort and pain
 Has shown potential for removing calculus during root debridement
Disadvantages of Er:YAG laser
 Does not selectively remove calculus on root surfaces; it removes calculus ,
cementum and dentin together

 Erbium, chromium:YSGG operates at a wavelength of 2.78µm.
Applications of Er,Cr: YSGG laser
 Enamel etching
 Caries removal
 Cavity preparation
 In vitro bone cutting with no burning, melting
or alteration of calcium :phosphorus ratio
 Root canal preparation
Advantages of Er,Cr: YSGG laser
 Economical : since it can be used multiple times providing the laser
therapy more feasible.
 No smear layer formation which suggest good bonding.
 Increases the resistance to acid demineralisation.
 Safe for pulp
Disadvantages of Er,Cr: YSGG laser
 Etching results: with laser enamel etching produces bonds with a wide
range of strengths, which can be unreliable .

 Argon is laser with an active medium of argon gas that is
energized by a high-current electrical discharge.
 It is fiberoptically delivered in continuous wave and gated pulsed
modes and is the only available surgical laser device whose
light is radiated in the visible spectrum.
 There are two emission wavelengths used in dentistry: 488 nm,
which is blue in color, and 514 nm, which is blue green.
 The 488-nm emission is the wavelength needed to activate
camphoroquinone, the most commonly used photoinitiator that
causes polymerization of the resin in composite restorative
materials.
 The beam divergence of this blue light, when used in a
noncontact mode, produces an excessive amount of photons,
providing curing energy.

 The 514-nm wavelength has its peak absorption in tissues and has
excellent hemostatic capabilities.
Applications of Argon lasers
 Resin curing
 Tooth bleaching
 Esthetic contouring of gingiva
 Oral ulcer treatment
 Frenectomy and Gingivectomy
 Treatment of acute inflammatory conditions such as hemangioma
 Caries detection
Advantages of Argon lasers
 It operates at a wavelength that is absorbed by hemogoblin, which
produces excellent hemostasis.
Disadvantages of Argon lasers
 The unpredictable interaction with soft tissue, the postoperative
edema, and the quality of wound healing.

 It contains a solid crystal of yttrium aluminum
garnet sensitized with chromium and doped
with holmium and thulium ions and is
fiberoptically delivered in free-running pulsed
mode.
 The wavelength produced by this laser is 2100
nm, also in the near infrared portion of the
invisible nonionizing radiation spectrum.
 It is absorbed by water 100 times greater than
Nd:YAG is, and using high peak powers it can
ablate hard, calcified tissue.

Applications of Holmium:YAG laser
 Soft tissue incision and ablation procedures
Advantages of Holmium:YAG laser
 It is less penetrating than Nd:YAG laser and therfore more faster
than Nd:YAG at cutting soft tissues.
 It is bactericidal.
Disadvantages of Holmium:YAG laser
 Though it is bactericidal it should not be used to decontaminate
the implants as it could damage the implant surfaces.

 Diode lasers are becoming quite popular due to their compact size and
relatively affordable economically.
 A specialized semiconductor that produces monochromatic light when
stimulated electrically is common to all diode lasers .
 Diode is a solid active medium laser, manufactured from
semiconductor crystals using some combination of aluminum or
indium, gallium, and arsenic.
 It has an electrical current pumping mechanism.
 The available wavelengths for dental use range from about 800 nm for
the active medium containing aluminium to 980 nm for the active
medium composed of indium, placing them at the beginning of the
near infrared portion of the invisible nonionizing spectrum.
 Each machine delivers laser energy fiberoptically in continuous wave
and gated pulsed modes and is used in contact with soft tissue for
surgery or out of contact for deeper coagulation.

Application of diode lasers
 Soft tissues incision and ablation
 Biopsy
 Laser assisted tooth whitening
Advantages of diode lasers
 Smaller size and portable instrument is one of the chief advantage
 Bactericidal property enables it to be used as an adjunctive to
periodontal procedures.
 Within certain low energy ranges, it can stimulate the proliferation of
fibroblast.
Diadvantages of diode lasers
 The continuous wave emission mode of the diode laser can cause a
rapid temperature rise in the target tissue.

 Introduction
 History
 Fundamentals of Lasers
Lasers Physics
Laser Delivery Systems and Emission Modes
Laser Interaction with Biological Tissues
Laser Energy and Tissue Temperature
 Types of Lasers

 Recently, it has been found that bacterial metabolites
within caries produce fluorescence that can be enhanced
by a laser light
 It is a device by which the laser induced fluorescence can
be measured to quantify tooth deminirealization .
 Based on the earlier findings on the fluorescence of
organic components in human teeth and the difference in
this fluorescence between sound and carious enamel, an
argon laser with blue green light of 448 nm wavelength
was used to detect caries.
 The technique was developed further in the early 1990s,
known as Quantitative Light-Induced Fluorescence
(QLF).

 It is a highly sensitive method for
determining short-term changes in
lesions in the mouth. The control
unit consists of an illumination
device and imaging electronics.
 In visible light, a typical smooth
surface lesion in the initial stage
appears as a whitish or opaque
discolouration. In fluorescent light
however, the same lesion is
perceived as a dark area within the
greenish flourescening sound hard
tissues and thus easier to detect.
This is due to the higher contrast
between sound hard dental tissues
affected by caries.

Kuhnisch J et al in 2007 conducted a study to
compare the outcome of quantitative light-
induced fluorescence (QLF) and meticulous visual
inspection (VI) in detecting non-cavitated caries
lesions on occlusal surfaces.
The study shows that QLF detects (1) more non-
cavitated occlusal lesions and (2) smaller lesions
compared to VI.

 The first commercially
available unit DIAGNOdent
using a red laser was
manufactured by Kavo
(Kavo GmbH) in 1998, with
an emission wavelength of
655 nm.
 The effectiveness of this
system is deemed to be best
incorporated as an adjunct
to other diagnostic methods
(tactile, visual, radiographic),
to limit the possibility of
‘false positive’ results.

 Primarily, the use of this
modality has been to detect
occlusal or flat surface
defects, although interstitial
caries can also be recorded.
 This system illuminates the
tooth surface with pulses of
red laser light and analyzes
the emitted fluorescence.
 The device analyzes the
emitted fluorescence on the
occlusal surface of the tooth,
which correlates with the
degree of demineralization in
the tooth and indicates the
relative amount of caries
present

 DIAGNOdent offers
the posibility of
fluorescence
measurement in
fissure areas since the
laser light may be
reflected through the
most minute access
routes.
 When using hand
instruments, it is not
generally possible to
probe drop-shaped
fissures.

Goel A. et al in 2009 conducted a study to compare the in vivo
effectiveness of DIAGNOdent with other conventional methods
(visual, tactile and bitewing radiographs) for the detection of
occlusal caries in primary molars. DIAGNOdent showed higher
sensitivity and accuracy as compared with other conventional
methods for detection of enamel caries, whereas for detection of
dentinal caries, even though the sensitivity was high, accuracy of
the DIAGNOdent device was similar to other conventional caries
diagnostic methods.
 Costa AM et al in 2009 conducted a study to evaluate the use of a
laser fluorescence device for detection of occlusal caries in
permanent teeth. Visual inspection, radiographic examination and
laser measurements were performed under standardized
conditions. Although the laser device had an acceptable
performance, this equipment should be used as an adjunct method
to visual inspection to avoid false positive results.

 Several studies examined the possibility of using laser to prevent
caries (Hossain et al, 2000; Apel et al, 2003).
 It is believed that
laser irradiation of dental hard tissues
modifies the calcium to phosphate ratio
reduces the carbonate to phosphorous ratio
leads to the formation of more stable and less acid soluble
compounds
reducing susceptibility to acid attack and hence caries.

 Watanabe and Arimoto in 2001 showed in their
study that enamel surfaces exposed to laser
irradiation are more acid resistant than non-laser
treated surfaces. The degree of protection against
caries progression provided by the one-time initial
laser treatment was reported to be comparable to
daily fluoride treatment by a fluoride dentifrice .
The threshold pH for enamel dissolution was
reportedly lowered from 5.5 to 4.8 and the hard
tooth structure was four times more resistant to
acid dissolution.

 The use of fluoride before and after laser
irradiation increases the fluoride uptake and
decreases the amount of solubility in acidic
solutions.
 Lasers that are being used in carious lesions
prevention comprise Nd:YAG, CO2, Er:YAG,
Er;Cr:YSGG, Argon and Diode.

 The Nd:YAG lasers is indicated for removal of
superficial pigmented caries, however, the
erbium family of lasers are the lasers of choice
and most efficient for deep enamel and dentin
caries removal.
 Thermal energy absorption by tissues
 Water vapourization and ablation
 Carious lesions have more water hence greater
effect

Eren F et al in 2013 conducted a study to perform a preliminary
evaluation of pain perception during
cavity preparation comparing the mechanical removal and
Er,Cr:YSGG laser removal of caries from enamel and dentine. The
subjects rated the perception of pain lower when the laser technique
was used. The application of the Er,Cr:YSGG laser system was a
more comfortable alternative or adjunctive method to conventional
mechanical cavity preparation.
Shahabi S et al in 2013 evaluated the effect of Er:YAG and
Er,Cr:YSGG laser on tensile bond strength of composite resin to
dentine in comparison with bur-prepared cavities. There is
significant difference in tensile bond strength of composite resin in
Er:YAG and Er,Cr:YSGG lased-prepared cavities in comparison with
bur-prepared cavities.

Power bleaching is the term used for
accelerated in-office tooth whitening
procedures, using laser .

Laser Wavelength
(typical)
nm
Properties and risk when used for light activated
bleaching
Argon-ion laser (continuous wave or pulsed) 488 (blue) Limited penetration depth into dental hard tissue; risk of
thermal damage relatively low
Argon-ion laser (continuous wave or pulsed)
514 (blue-green)
Low absorption in water and tooth mineral; risk of thermal
damage relatively low
KTP laser (kalium-titanyl-phosphate crystal
frequency doubled Nd:YAG laser, pulsed) 532 (green)
Relatively low absorption in water and tooth mineral; medium
penetration depth into dental hard tissue
He–Ne laser (continuous wave)
632 (red)
Relatively low absorption in water and tooth mineral;
deeper penetration depth into dental hard tissue
Nd:YAG laser (neodynium: yttrium
aluminumgarnet, pulsed) 1064 (IR-A, NIR)
Low absorption in water and tooth mineral; absorption in dark
pigments; deep penetration into dental hard tissue—pulp
damage due to temperature rise
Diode laser (continuous wave or pulsed) 810, 830, 980 (IR-A,
NIR)
Low absorption in water and tooth mineral; absorption in
pigments; deep penetration into dental hard tissue—pulp
damage due to temperature rise
Er,Cr:YSGG laser (erbium chromium: yttrium
scandium gallium garnet, pulsed) 2790 (IR-B, SWIR)
Very high absorption in water and high absorption in tooth
mineral (OH−); low penetration depth into dental hard tissue—
relatively low risk of direct pulp damage
Er:YAG laser (erbium: yttrium aluminum garnet,
pulsed) 2940 (IR-B, SWIR)
Highest absorption in water and high absorption in tooth
mineral (OH−); low penetration depth into dental hard tissue—
relatively low risk of direct pulp damage
CO2 laser (continuous wave or pulsed) 9400, 10600 (IR-C,
LWIR)
High absorption in water and highest absorption in tooth
mineral (phosphate); low penetration depth into dental hard
tissue—relatively low risk of direct pulp damage using pulsed

 Sari T et al in 2013 evaluated the increase in temperature
induced by various light sources during in-
office bleaching treatment, under simulated blood
microcirculation in pulp conditions. The highest pulp
temperature increases were recorded for the diode laser
group (2.61 °C), followed by the Er:YAG laser (1.86 °C)
and LED (1.02 °C) groups. Despite the significant
differences among the groups, the temperature increases
recorded for all groups were below the critical value of
5.6 °C that can cause irreversible harmful changes in pulp
tissue. It can be concluded that, with regard to temperature
increase, all the light sources evaluated in this study can
be used safely for in-office bleaching treatment within the
described parameters.

Argon lasers are used for this purpose. For
polymerization of camphorquinone
activated composite resin,the argon laser.
 Increases;
~ the depth of cure
~ the diametric tensile strength
~ adhesive bond strength
~ degree of polymerization of
materiels.
 Reduces;
~ acid solubility of surrounding enamel
decreases the time of activation
significantly.

Desensitization of hypersensitive teeth with
laser has focused two different approaches:
 Low-level laser therapy
 High-level laser therapy.

Low-level laser therapy
 It is believed that low-level therapy lasers
stimulate nerve cells, interfering with the
polarity of cell membranes thus blocking the
transmission of pain stimuli in hypersensitive
dentin.
 It seems that the low output lasers mediate
analgesic effects due to depressed nerve
transmission.

High-level Laser Therapy
 High-level laser therapy (HLLT) has also
been applied to minimize dentinal pain, and
may be delivered by devices with higher
power outputs, such as carbon dioxide
(CO2), Nd:YAGand Er:YAG lasers, when
they are used at lower energy settings.
 Scanning electron microscopy (SEM) after
irradiation has shown occlusion of dentinal
tubules thus suggesting this may be the
possible mechanism involved in pain relief.

 Gholami GA et al in 2011 evaluated the
occluding effects of Er;Cr:YSGG, Nd:YAG),
CO2, and 810-nm diode lasers on dentinal
tubules. The results indicate that Nd: YAG, Er;
Cr: YSGG, and CO(2) lasers, can occlude
dentinal tubules partially or totally, and therefore
reduce patients hypersensitivity symptoms. The
810-nm diode laser sealed tubules to a far
lesser degree, with negligible effects on
desensitization.

 LASER DOPPLER FLOWMETRY- Laser
Doppler flowmetry (LDF), is a
noninvasive, objective, painless, semi-
quantitative method, has been shown to
be reliable for measuring pulpal blood
flow .
 Laser light is transmitted to the pulp by
means of a fibre optic probe.
 Scattered light from moving red blood
cells will be frequency-shifted whilst that
from the static tissue remains unshifted.
 The reflected light, composed of Doppler-
shifted and unshifted light, is returned by
afferent fibres and a signal is produced.
 Helium-Neon & Diode lasers at low
power of 1-2mW.

 Moritz et al in 1998 conducted a study in which 260
pulp capping procedures i.e.direct pulp capping was
performed using Ca(OH)2. The CO2 laser was used in
superpulsed mode. The controls were conventionally
treated. After 2 years, the success rate was 93% in the
laser group compared to 66.6% in the control group.
Dentinal bridge formation along with charring,
coagulation necrosis & degeneration was seen.
 Santucci in 1999 performed a retrospective study in
which 93 pulp cappings in permanent teeth were
evaluated. He used an Nd:YAG laser with Vitrebond as
a capping material and Ca(OH)2 as a control; results
were evaluated after 54 months. The success rate was
90.3% in the lased and 43.6% in the control group.

 Deep dentinal cavities- indirect pulp
capping- reducing the permeability of
dentin by sealing dentinal tubules – Nd:YAG
& CO2 lasers.

Cleaning and Shaping
 Using an Er:YAG laser, root canal orifices were prepared.
 Weichman & Johnson (1971) first applied a laser to the root
canals by attempting to seal the apical foramen in vitro by
means of a high-power CO2 laser.
 Although the goal was not achieved the Nd:YAG laser was used
to seal the entrance to the root canal at the apex of a tooth in
vitro .
 The development of a thin fibre for the Nd:YAG laser stimulated
its application in root canals. Debris and smear layer were
removed using appropriate laser parameters and dentine
permeability was also reduced.
 Argon laser irradiation can achieve an efficient cleaning effect
on instrumented root canal.
 Er:YAG laser irradiation was more effective in removing the
smear layer and debris on root canal walls than the Ar or
Nd:YAG laser.

 Various methods have been
advocated to render the canal
walls free of irregularities.
 After irradiation by an Er:YAG
laser, the root canal surface
appeared smooth in the light
microscope and scale-like when
viewed by SEM.
 Since clean and regular root canal
walls can be achieved using
Nd:YAG laser irradiation, root
canal shaping using this modality
has been suggested.

Sterilization of root canals:
 Pulp space therapy will fail if pathogenic
bacteria persist in the canals even after
cleaning and shaping.
 Researchers have proved Nd: YAG and CO2
laser to disinfect the dentinal tubules and root
canals. Many other lasers such as the Er:YAG
laser ,a diode laser have also been used for this
purpose.
 Lasers can be delivered into root canals using a
hollow tube or thin fibre optics .
 All lasers have a bactericidal effect at high
power that is dependent on each laser.

 Inadvertent transmission of laser into the
Periapical region can be dangerous. Er: YAG
laser with a side firing tip has been
developed to overcome this.
A thin, flexible endo fiber tip eliminates
infected tissue from a canal.

 Yasuda Y et al in 2010 evaluated the
bactericidal efficacy of Nd:YAG and
Er:YAG laser in the experimentally infected
curved root canals. Er:YAG laser showed
higher bactericidal effects than did the
Nd:YAG laser both in the curved and
straight root canals.

Obturation:
Ar, CO2 and Nd: YAG lasers have been
used to soften gutta- percha and results
indicate Ar laser to produce a very good
apical seal.
Park DS in 2001 evaluated the effect of
Nd:YAG laser irradiation on the apical
leakage of obturated root canals .
Laser irradiation following root canal
preparation reduced apical leakage
following root canal obturation.

 Nd:YAG laser at three output power has
been used to remove gutta percha and
broken files from root canals. The time
required for removal of any root canal filling
is shorter than the conventional methods.

 Laser has the ability to vaporize tissue and
coagulate and seal small blood vessels and thus a
bloodless field can be achieved.
 The cut surface if irradiated it is sterilised and
sealed by the laser.
 Since no thermal and structural damage is caused
by Er: YAG laser while properly cutting through
dental hard tissues, the need for mechanical drill is
eliminated.
 Er: YAG laser give smooth, clean resected
surfaces.
 Clinically patients reported less discomfort and
improved healing.

84
 Lasers are classified by hazard potential
based upon their optical emission.
 Necessary control measures are
determined by these classifications.
 In this manner, unnecessary restrictions
are not placed on the use of many lasers
which are engineered to assure safety.
 In the U.S., laser classifications are based
on American National Standards Institute’s
(ANSI) Z136.1 Safe Use of Lasers.

› Class 1 denotes laser or laser systems that do
not, under normal operating conditions, pose a
hazard.
› Class 2 denotes low-power visible lasers or
laser system which, because of the normal
human aversion response (i.e., blinking, eye
movement, etc.), do not normally present a
hazard, but may present some potential for
hazard if viewed directly for extended periods of
time (like many conventional light sources).

• Class 3a denotes some lasers or laser systems having a CAUTION
label that normally would not injure the eye if viewed for only
momentary periods (within the aversion response period) with the
unaided eye, but may present a greater hazard if viewed using
collecting optics.
• Class 3b denotes lasers or laser systems that can produce a hazard
if viewed directly.
• Class 4 denotes lasers and laser systems that produce a hazard not
only if viewed directly, but may also produce significant skin hazards
as well as fire hazards.

Safety officers
Dental practices offering Class IIIB and IV laser treatment, must
appoint a laser protection advisor (LPA) and a laser safety
officer (LSO). The LPA is usually a medical physicist who will
advise on the protective devices required, for any given laser
wavelength being used.
Access
Most Class IV lasers have a remote inter-lock jack socket,
whereby door locks and warning lights can be activated during
laser emission. Those dental clinics that operate a multi-chair,
open-plan environment would need to address the requirement
in greater detail. During laser treatment, only the clinician,
assistant and patient should be allowed within the controlled
area.

Laser safety features
All lasers have in-built safety features
that must be cross-matched to allow
laser emission. These include:
 Emergency ‘Stop’ button,
 Emission port shutters to prevent
laser emission until the correct
delivery system is attached,
 Covered foot-switch, to prevent
accidental operation,
 Control panel to ensure correct
emission parameters,
 Audible or visual signs of laser
emission,
 Locked unit panels to prevent
unauthorised access to internal
machinery,
 Key or password protection,

Eye protection
 All persons within the controlled area must wear
appropriate eye protection devices during laser
emission. It is considered advisable to cover the
patient’s eyes with damp gauze for long wavelength
perioral procedures.The LSO should select the correct
eyewear for the laser wavelength being used; these
should be free of any scratches or damage and be
constructed with side protection
Test firing
 Prior to any laser procedure and before admitting the
patient, either the clinician or LSO should test-fire the
laser. This is to establish that the laser has been
assembled correctly, is working correctly and that
laser emission is occurring through the delivery
system.
Training
 All staff members should receive objective and
recognised training in the safety aspects of laser use
within dentistry, as with other specialties .

ADVANTAGES DISADVANTAGES
Selective removal of affected epithelium and minimal damage to
surrounding healthy tissues.
High cost of equipment
Dressing or suturing is not required for wound closing. Excellent
wound healing due to biostimulation Laser beam could injure the patient, doctor or staff by direct beam or
the reflected light causing retinal burn.
Laser beam exerts a hemostatic effect.
No single wavelength will optimally treat all dental disease.
Risk of blood borne contamination is dramatically reduced. Not available in all hospitals.
Causes reduction in bacterial count, reduces the risk of infection. Special trained persons needed for operation.
Pain is reduced to absent 90% of the time, probably due to the sealing
of nerve fibers.
Their antiseptic efficiency reduces the need for post operative
antibiotic therapy in most cases.
Little chance for mechanical trauma by employing a ‘non-contact’
technique.
Little post operative scarring.

 Lasers represent a phenomenal change in dentistry, and in
the future the laser may be just as common place as the
dental handpiece in the dental office.
 Although much more scientific research- especially clinical
research is needed.
 When used efficaciously and ethically, lasers are an
exceptional modality of treatment for many clinical
conditions that dentists treat on daily basis.
 But laser has never been the “magic wand” that many
people have hoped for. It has got its own limitations.
 However, the futures of dental laser are bright with some
of the newest ongoing researches.

 Oral laser application- A. Moritz
 Lasers in dentistry- Leo J./ Robert M Pick
 D.J. Coluzzi and R.A. Convissar .Lasers in Clinical Dentistry .DCNA. October 2004
VoL 48, Issue 4.
 Matsumoto K . Lasers in endodontics. Dent Clin North Am. 2000 Oct;44(4):889-906.
 Kimura Y, Wilder-Smith P, Matsumoto K. Lasers inendodontics: a review.
International Endodontic Journal, 33 , 173–185, 2000.
 Kuhnisch J et al .In vivo detection of non-cavitated caries lesions on occlusal
surfaces by visual inspection and quantitative light-induced fluorescence. Acta
odontol scand. 2007 jun;65(3):183-8.
 Goel A et al. Comparison of validity of DIAGNOdent with conventional methods for
detection of occlusal caries in primary molars using the histological gold standard:
an in vivo study.J. Indian soc pedod prevn dentistry 2009 Oct-Dec;27(4):227-34.
 Lasers in Endodontics – A Practical Overview Andreas Moritza, Ulrich Schoopb,
Johannes Klimschab, Kawe GoharkhayJ Oral Laser Applications 2004; 4: 159-166.
 Direct Pulp Capping Using an Er,Cr:YSGGLaser JanWalter BlankenaJ Oral Laser
Applications 2005; 5: 107-114.
 Park DS et al.Effect of Nd:YAG laser irradiation on the apical leakage of
obturated root canals: an electrochemical study. IEJ 2001 Jun;34(4):318-21.

 Yasuda Y et al.Bactericidal effect of Nd:YAG and Er:YAG lasers in
experimentally infected curved root canals. Photomed Laser Surg. 2010
Oct;28 Suppl 2:S75-8.
 Santucci PJ. Dycal versus Nd:YAG laser and Vitrebond for directpulp
capping in permanent teeth. J Clin Laser Med Surg 1999;17:69-75.
 Moritz A, Schoop U, Goharkhay K, Speer W. Advantages of a pulsed CO2
laser in direct pulp capping: a long-term in vivo study. Lasers Surg Med
1998;22:288-293.
 Gholami GA An evaluation of the occluding effects of Er;Cr:YSGG,
Nd:YAG, CO₂ and diode lasers on dentinal tubules: a scanning electron
microscope in vitro study. Photomed Laser Surg. 2011 Feb;29(2):115-21.
 Ana Raquel Benettia, Eduardo Batista Francob, Eric Jacomino Francoc,
José Carlos. Laser Therapy for Dentin Hypersensitivity: A Critical Appraisal
PereiradJ Oral Laser Applications 2004; 4: 271-278.
 Roeland De Moor, Dries Torbeyns, Maarten Meire .Lasers in endodontics.
Part 2: Root canal wall cleanliness and modification. ENDO .2009;3(1):19–
33
 Lasers in endodontics : Beginning of new era. Ratnakar P.Indian J stomatol
2010.
 Sari T. Temperature rise in pulp and gel during laser-activated bleaching: in
vitro. Lasers Med Sci. 2013 Jun 21.
 Weichman JA, Johnson FM . Laser use in endodontics. A preliminary
investigation. Oral Surg Oral Med Oral Pathol. 1971 Mar;31(3):416-20.

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