Lasers in orthodontics

CONTENTS
 INTRODUCTION
 DISCOVERY OF LASERS
 LASER PHYSICS
 COMPONENTS OF LASER
 PROPERTIES OF LASER
 CLASSIFICATION OF LASERS
 LASER TISSUE INTERACTION AND BIOLOGICAL EFFECTS
 LASERS USED IN DENTISTRY
 USES OF LASERS IN ORTHODONTICS
 REFERENCE

INTRODUCTION
 Light has been used as a therapeutic agent for many
centuries.
 Natural light was used for medical treatment in
ancient Egypt and Greece.
 Later Roman and Arab physicians introduced light
therapy into general medical use

 Light is a form of electromagnetic energy that exists as
a particle, and travels in waves, at a constant velocity
 The basic unit of this radiant energy is called a photon

 The wave of photons travels at the speed of light can be
defined by two basic properties
 First is amplitude, which is defined the vertical height of
the wave oscillation from the zero axis to its peak.
 The second property of a wave is wavelength, which is the
horizontal distance between any two corresponding points
on the wave.

 This correlates to the amount of energy in the wave:
the larger the amplitude, the greater the amount of
energy that can do useful work
 A joule is a unit of energy

 As waves travel, they oscillate several times per second,
termed frequency.
 Frequency is inversely proportional to wavelength: the
shorter the wavelength, the higher the frequency and
vice versa.

 The newer treatment procedures are conservative,
painless and are more reliable and they contribute
towards better esthetics.
 The development of LASER (light amplification by the
stimulated emission of radiation) in dentistry has
allowed the dental professionals to provide comfort
and better treatment for the patient

 A laser is a device that emits light (electromagnetic
radiation) through a process of optical amplification
based on the stimulated emission of photons

Discovery of laser
 In 1704, Newton characterised light as a stream of
particles
 The Young’s interference experiment in 1803 and the
discovery of the polarity of light convinced other
scientists of that time that light was emitted in the
form of waves

 The concept of electromagnetic radiation, of which
‘light’ is an example, had been described in
mathematical form by Maxwell, in 1880
 Maxwell’s electromagnetic (EM) theory explained light
as rapid vibrations of electromagnetic fields due to the
oscillation of charged particles

 The electromagnetic spectrum is a comparative
arrangement of electromagnetic energy (photonic
quanta) relative to wavelength, spanning ultra-short
gamma and X-radiation, through visible light, to ultra-
long micro- and radio-waves

 Maxwell’s electromagnetic theory, the energy intensity
of electromagnetic emissions with a given frequency is
proportional to the square of this frequency
 At the turn of the 20th century, the black body
radiation phenomenon challenged the waveform light
theory

 According to Planck,radiation such as light, is emitted,
transmitted and absorbed in discrete energy packets or
quanta, determined by the frequency of the radiation
and the value of Planck’s constant

 In explaining the photoelectric effect, Einstein
assumed that a photon could penetrate matter, where
it would collide with an atom.
 Since all atoms have electrons, an electron would be
ejected from the atom by the energy of the photon,
with great velocity.

 Einstein explained about laser light in 1917 in his Zur
Theorie der Strahlung(Theory of Wavelength), that
when there exists the population inversion between
the upper and lower energy levels among the atom
systems, it was possible to realise amplified stimulated
radiation.

 Stimulated electromagnetic radiation emission has the
same frequency (wavelength) and phase (coherence)
as the incident radiation

MASER
 In 1953, Charles Townes, experimenting with microwaves,
produced a device whereby this radiation could be
amplified by passing it through ammonia gas
 This was the first MASER (microwave amplification by the
stimulated emission of radiation) and was developed as an
aid to communication systems and time-keeping (the
‘atomic clock’)

LASER
 Theodore Maiman in 1960 invented the first laser at
the Hughes Air Craft Company,USA using a lasing
medium of ruby that was stimulated using high energy
flashes of intense light.

 In 1964, Ralph Stern and Reidar Sognnaes used the
ruby laser to vaporise enamel and dentine.
 In 1969 Leon Goldman used the laser clinically on
enamel and dentine.

Laser physics
 Laser is a device that converts electrical or chemical
energy into light energy.
 In contrast to ordinary light that is emitted
spontaneously by excited atoms or molecules, the light
emitted by laser occurs when an atom or molecule
retains excess energy until it is stimulated to emit it
 The radiation emitted by lasers including both visible
and invisible Iight is more generally termed as
electromagnetic radiation

 The concept of stimulated emission of light was first
proposed in 1917 by Albert Einstein.
 He described three processes
1. Absorption
2. Spontaneous emission
3. Stimulated emission

 Einstein considered the model of a basic atom to
describe the production of laser
 An atom consists of centrally placed nucleus which
contains positively charged particles known as
protons, around which the negatively charged
particles, i.e. electrons are revolving.

 When an atom is struck by a photon, there is an
energy transfer causing increase in energy of the atom.
 This process is termed as absorption.

 The photon then ceases to exist, and an electron
within the atom pumps to a higher energy level.
 This atom is thus pumped up to an excited state from
the ground state

 In the excited state, the atom is unstable and will soon
spontaneously decay back to the ground state,
releasing the stored energy in the form of an emitted
photon.
 This process is called spontaneous emission

 If an atom in the excited state is struck by a photon of
identical energy as the photon to be emitted, the
emission could be stimulated to occur earlier than
would occur spontaneously.
 This stimulated interaction causes two photons that
are identical in frequency and wavelength to leave the
atom.
 This is a process of stimulated emission

 If a collection of atoms includes, more that are
pumped into the excited state that remain in the
resting state, a population inversion exists.
 This is necessary condition for lasing

 Now, the spontaneous emission of a photon by one
atom will stimulate the release of a second photon in a
second atom, and these two photon will trigger the
release of two more photons.
 These four then yield eight, eight yield sixteen and so
on.

 In a small space at the speed of light, this photon
chain reaction produces a brief intense flash of
monochromatic and coherent light which is termed as
'laser'

Components of laser
1. Active medium
2. Pumping mechanism
3. Optical resonator
4. Delivery system
5. Cooling system
6. Control panel

Active medium.
 This material may be a solid, liquid or gas.
 Lasing medium determines the wavelength of the light
emitted from the laser and the laser is named after the
medium.

 The first dental laser used a crystal of neodymium-
doped yttrium aluminium garnet (Nd:YAG) as its
active medium.

 The active medium is positioned within the laser
cavity, an Internally-polished tube, with mirrors co-
axially positioned at each end and surrounded by the
external energising input, or pumping mechanism

2. Pumping mechanism
 This represents a man-made source of primary energy
that excites the active medium.
 This is usually a light source, either a flashlight or arc-
light, but can be a diode laser unit or a electromagnetic
coil

 Energy from this primary source is absorbed by the
active medium, resulting in the production of laser
light.
 This process is very inefficient, with only some 3-10%
of incident energy resulting in laser light, the rest
being converted to heat energy.

3. Optical resonator
 Laser light produced by the stimulated active medium
is bounced back and forth through the axis of the laser
cavity, using two mirrors placed at either end, thus
amplifying the power.
 The distal mirror is totally reflective and the proximal
mirror Is partly transmissive, so that at a given energy
density, laser light will escape to be transmitted to the
target tissue

4.Delivery system
 Laser energy should be delivered to the surgical site by
various means that should be ergonomic and precise
 Dependant upon the emitted wavelength, the delivery
system may be a quartz fibre-optic, a flexible hollow
waveguide, an articulated arm (incorporating mirrors),
or a hand-piece containing the laser unit (at present
only for low-powered lasers).

 Shorter wavelength instruments, such as KTP, diode,
and Nd:YAG lasers, have small, flexible fiber‐optic
systems with bare glass fibers that deliver the laser
energy to the target tissue.
 Erbium and CO2 devices are constructed with more
rigid glass fibers, semi‐flexible hollow waveguides, or
articulated arms

 All the invisible dental lasers are equipped with a
separate aiming beam, which can either be laser or
conventional light.
 The aiming beam is delivered co‐axially along the
fiber or waveguide and shows the operator the exact
spot where the laser energy will be focused.

 Dental lasers can be used either in contact mode or
non contact mode
 In contact mode, the fiber tip is placed in contact
with the tissue.
 The charred tissue formed on the fiber tip or on the
tissue outline increases the absorption of laser energy
and resultant tissue effects

 Char can be eliminated with a water spray and then
slightly more energy will be required to provide time
efficient results.
 Advantage is that there is control feed back for the
operator

Non contact mode
 Fiber tip is placed away from the target tissue.
 The clinician operates with visual control with the aid
of an aiming beam or by observing the tissue effect
being created.

 There are two basic modes of wavelength emission for
dental lasers, based on the excitation source.
1. Continuous mode
2. Pulsating mode

1.Continuous mode
 Continuous wave emission means that laser energy is
emitted continuously— as long as the laser is
activated—and produces constant tissue interaction.
 CO2 and diode lasers operate in this manner

 These lasers are sometimes equipped with a
mechanical shutter with a time circuit or a digital
mechanism to produce gated or super‐pulsed energy.
 Pulse durations can range from tenths of a second to
several hundred microseconds.

2.pulsating mode
 Free‐running pulse emission occurs with very short bursts
of laser energy due to a flashlamp pumping mechanism.
 The usual pulse durations are in the low hundreds of
microseconds, and there is a relatively long interval
between pulses.
 Nd:YAG, Er:YAG, and Er,Cr:YSGG devices operate as
free‐running pulsed lasers.

5. Cooling system
 Heat production is a by product of laser light
propagation.

 It increases with the power output of the laser and
hence, with heavy-duty tissue cutting lasers, the
cooling system represents the bulkiest component.
 Co-axial coolant systems may be air- or water-assisted.

 Erbium lasers employ a water spray for cooling hard
tissues

6.control panel
 This allows variation in power output with time, above
that defined by the pumping mechanism frequency.
 Other facilities may allow wavelength change (multi-
laser instruments)

PROPERTIES OF LASER LIGHT
 There are several important properties of laser light
that distinguish it from the normal light

Monochromatism
 Lasers emit light that is monochromatic or specifically
have a single wave length from UV to infrared. i.e.
lasers express one color.

 Lasers of varying types emit an individual wave length
or specified wavelengths
 This property is important for the high spectra power
density of the laser beam

Collimation or (Directionality)
 The laser beam, as it exits from the laser device, has
very little divergence.
 They do not diverge and travel parallel to each other.
 The beam which is emitted has constant size and
shape.

 Most of the gas or solid-state laser emit laser beam
with a divergence angle of approximately a milli
radian.
 This explains why laser light is extraordinarily
hazardous.

 By not diverging over distance, laser light maintains
brightness, so that it is still concentrated enough to be
dangerous.
 But this property is important for good transmission
through delivery system

Coherency
 The laser light waves produced are physically identical.
i.e. they have identical amplitude and frequency.
 There are two types of coherence of laser light,
longitudinal and transverse.

 The longitudinal type of coherence represents time
coherence along the longitudinal beam, whereas
transverse coherence or spectral coherence refers to
coherence across the beam.

 Coherence causes the collimation of a laser beam over
extremely large distances and allows the beam to
accept extremely fine focusing
 Any given laser beam can be focused only to a
diameter equal to the wavelength of the specific laser

Brightness
 This property arises from the parallelism or
collimation of the laser light as it moves through space
maintaining its concentration.
 The high brightness factor translates to high
concentrations of energy when the laser is focused on
a small spot

 The focusing of the brightness of the laser beam is
what the clinicians depends on to elevate the
temperature of tissues or to cut or to vaporize the
tissues

Difference between ordinary light
and laser light

Classification of Lasers
1.BASED ON ACTIVE MEDIUM :
 Solid state- Nd: YAG
 Liquid state-diode laser
 Gas state- CO2

2.DEPENDING ON WAVE LENGTH
 Hard lasers- comes in infrared Spectrum (> 700 nm)
Eg: CO2; Nd: YAG; Argon laser
 Soft Lasers - Comes in UV (140-400nm) & visible light
(400-700) spectrum Eg: HeNe, diode laser

3.BASED ON SAFETY PROCEDURE
 Class 1: safe under all conditions (fully enclosed system) -
Eg: Nd: YAG laser. Laser used in dental laboratory.
 Class 2: Output is 1 mw- visible low power laser- Visible red
aiming beam of a surgical laser.
 Class 3A: Visible laser above 1 milli watt- No dental
examples

 Class 3B: Upper continuous power output limit is 0.5 w-
Low power diode laser used for biostimulation. Direct
viewing is hazardous to the eye.
 Class 4: Output excess of class 3B & are used for cutting &
drilling- All lasers used for oral surgery, whitening and
cavity preparation. Direct or indirect viewing is hazardous
to the eyes

LASER- TISSUE INTERACTION AND
BIOLOGICAL EFFECTS
 Once a laser beam is produced it is aimed at tissue to
perform a specific task.
 As the energy reaches the biological interface, one of
four interactions will occur
1. Absorption
2. Reflection
3. Transmission
4. Scattering

Absorption
 Specific molecules in the tissue known as chromophores
absorb laser light energy
 The light energy is then converted into other forms of
energy to perform work.
 Main chromophores seen in oral tissues are hemoglobin,
melanin,pigmented proteins,hydroxyapatite,and water

 Absorption is the most important interaction.
 Each wavelength has specific chromophores that
absorb their energy.

 Near infrared lasers like diodes and Nd:YAGs are
mostly absorbed by pigments such as hemoglobin and
melanin.
 Erbium and CO2 lasers are predominantly absorbed by
water
 with erbium wavelengths also exhibiting some
hydroxyapatite absorption.

 The shorter, near infrared wavelengths of diodes and
Nd:YAG lasers penetrate tissue more deeply than the
longer, mid infrared wavelengths of the Erbium and
CO2 lasers

Thermal relaxation
 Thermal relaxation is the term applied to the ability to
control a progressively increasing heat loading of
target tissue.
 Thermal relaxation rates are proportional to the area
of tissue exposed and inversely proportional to the
absorption coefficient of the tissue

Factors that influence absorption and thermal
relaxation are
1.Exposure time and Laser emission mode
Thermal relaxation will occur least with continuous
wave emission and maximally in free-running pulsed
delivery
2. Laser incident power (Joules per second)

3.Laser power density (Watts per square centimetre): for
any chosen level of incident power, the smaller the beam
diameter, the greater concentration of heat effects
4. Beam movement: relative to tissue site; rapid laser
beam movement will reduce heat build-up and aid
thermal relaxation

4. Endogenous coolant: blood flow.
5.Exogenous coolant: water, air, pre-cooling of tissue
6.Incident angle of laser beam
 Maximum control of laser tissue interaction can be
achieved if the incident laser beam is perpendicular to
the tissue surface

 Reducing the incident angle towards the refractive
angle of the tissue surface will increase the potential
for true light reflection with an associated reduction in
tissue change

Reflection
 Density of the medium , or angle of incidence being less
than the refractive angle , results in total reflection of the
beam.
 In true reflection ,the incident and emergence angles will
be the same .
 If the medium interface is rough or non homologous ,
some scatter may occur

Transmission
 In transmision beam enters the medium , but there is
no interaction between the incident beam and the
tissue.
 The beam will emerge distally , unchanged or partially
refracted.

Scattering
 Once the laser energy enters the target tissue it will
scatter in various directions.
 This phenomenon is usually not helpful, but can help
with certain wavelengths biostimulative properties.

 There are five important types of biological effects that
can occur once the laser photons enter the tissue:
 They are
1. fluorescence
2. photothermal
3. photodisruptive
4. photochemical
5. photobiomodulation

Fluorescence
 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 chromophores
absorb the laser energy and heat is generated.
 This heat is used to perform work such as incising
tissue or coagulating 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
tissue

Photodisruptive 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.

 Thus tooth and bone are not vaporized but pulverized
instead through the photomechanical ablation
process.
 This shock wave creates the distinct popping sound
heard during erbium laser use.

 Photochemical reactions occur when photon energy
causes a chemical reaction.
 These reactions are implicated in some of the
beneficial effects found in biostimulation

 Photobiomodulation or Biostimulation refers to
lasers ability to speed healing, increase circulation,
reduce edema, and minimize pain.
 Many studies have exhibited effects such as increased
collagen synthesis, fibroblast proliferation, increased
osteogenesis, enhanced leukocyte phagocytosis

 The exact mechanism of these effects is not clear, but
it is theorized they occur mostly through
photochemical and photobiological interactions
within the cellular matrix and mitochondria.
 Biostimulation is used dentally to reduce postoperative
discomfort and to treat recurrent herpes and aphthous
stomatitis

 When a laser heats oral tissues, certain reversible or
irreversible changes can occur
1. Hyperthermia – below 50 degrees C
2. Coagulation and Protein Denaturation – 60+
degrees C
3. Vaporization – 100+degrees C
4. Carbonization - 200+ degrees C

 Irreversible effects such as denaturation and
carbonization result in thermal damage that causes
inflammation, pain, and edema.

Immediate post operative view of an excisional
procedure using a diode laser.

Immediate post operative views of excisional procedures
using Erbium and Carbon Dioxide lasers.

Jerun jose
2nd year pg
Department of orthodontics

CONTENTS
 LASER EFFECTS ON DENTAL HARD AND SOFT TISSUES
 LASERS USED IN DENTISTRY
 USES OF LASERS IN ORTHODONTICS
 LASER SAFETY IN DENTAL PRACTICE
 CONCLUSION
 REFERENCE

Laser Effects on Dental Hard
Tissues
Thermal Effect
 Here thermal vaporization of tissue by absorbing infrared
laser light occur
 The laser energy is converted into thermal energy or heat
which destroys the tissues.

 The laser beam couples to the tissue surface, and this
absorption leads to a heating with denaturation at about
45°C to 60°C.
 Above 60°C coagulation and necrosis can be observed
accompanied by a desiccation of the tissue.
 At 100°C the water inside the tissue vaporizes

 Carbonization and later pyrolysis with vaporization of the
bulky tissue terminate the thermal laser tissue interaction.
 The laser light will be absorbed and converted to thermal
energy by stimulating the lattice vibrations of the tissue
molecules.

 This leads to a heating of the surrounding tissues to a
boiling of water followed by carbonization and tissue
removal
 Damage to the adjacent tissue is manifested by massive
zones of carbonization, necrosis and cracks.

Mechanical Effect
 High energetic and short pulsed laser light can lead to a
fast heating of the dental tissues in a very small area.
 The energy dissipates explosively in a volume expansion
that may be accompanied by fast shock waves

 These waves can lead to very high pressures so that
adjacent tissue will be destroyed or damaged.
 To avoid micro cracks in dental tissues, the maximum laser
energy density of all laser systems must be kept below a
certain threshold.

Chemical Effect
 The basis of the photochemical effect is the absorption of
laser light without any thermal effect which leads to an
alteration in the chemical and physical properties of the
irradiated tissues
Normal enamel Lased enamel

Thermomechanical Effect
 Due to the good absorption of laser in water as well as in
hydroxyapatite, the laser radiation leads to fast heating of
water inside.
 In the mineralized matrix there is an explosive volume
expansion

 In dentin, no cracks are seen, but more thermal damage
like carbonization and necrosis are found.
 In enamel, cracks are always found

Morphological analysis of Er:YAG laser treated enamel
 Enamel. 100 mj. 10 Hz.
With water cooling.
 Honey-comb appearance
can be seen but not
throughout the surface
due to non-homogenous
application of the laser
With water cooling.
 Honey-comb appearance
can be seen on the surface
similar to acid etching.

With water cooling.
 Higher magnification of
the surface
 No signs of thermal
damage.
 Honey-comb appearance.
With water cooling.
 Serrated surface with
honey-comb appearance.

With water cooling.
 Interprismatic matrix has
been removed.
 some melting points due to
repeated shots at the same
point seen
Without water cooling.
 Layered enamel surface
due to dehydration of
enamel during laser
application

 Enamel. 800 mj. 5 Hz
 Melted and resolidified
enamel.
 This texture is highly acid
resistant.

 Rose-bud like appearance.
 over destruction of enamel
with high energy intensity.
 Enamel lost its integrity in
layers around the lased
point.
 Overdestructed and
layered surface as a result
of excessively heated
enamel.

Effects on dentin
 Dentin. 250 mj. 10 Hz.
 Swollen dentin orifices
With water cooling.
 Partially open dentinal
tubules with crater
formations

 Pop-corn like appearance.
 Thermal destruction of
dentin
 Dentin. 500 mj. 5 Hz. With
water cooling.
 Dehydartion resulted in
cracking

Ablation Threshold of Er:YAG and Er:YSGG Laser
Radiation in Enamel and dentin

Laser Effect on Dental Pulp
 Vital dental pulp is acutely sensitive to thermal change
The pulp tissue response to lasers is evaluated in three forms
 Histologic analysis
 Radiographic analysis
 Laser Doppler flow meter measurement

 Use of a continuous wave apparatus has been shown to
generate significant thermal tissue damage in the oral
cavity
 Pulpal tissue cannot survive in an environment of elevated
temperatures for long periods when tooth structure is
irradiated with lasers

 Rise of 6°C results in irreversible pulpitis
 Rise of 11°C results in necrosis of pulp

 Pulsing which has been used during soft tissue laser
ablation has an effective mechanism for reducing the
extent of collateral tissue damage
 The use of a combination of air and water spray before,
during or immediately after laser irradiation to enamel and
dentin may be a more effective method for temperature
control and reduction of heat transfer to the pulp

 Air-water cooling is used with laser systems such as CO2,
holmium and erbium.
 This can provide adequate heat protection to the pulp
equivalent to that of the common dental drill

 Uncontrolled laser irradiation of oral structures can cause
pulpal inflammation with any type of laser
 The undesirable side effects of laser vary primarily with
power and energy density and secondarily with the type of
laser used

 If pulp temperature is raised beyond 5°C level, the
odontoblastic layer may not be present.
 Odontoblastic alignment may be disrupted, displaying
vertical and layering type of structure.
 The threshold response for pulp reaction appears to lie at
energy density less than 60 J/cm

LASERS USED IN DENTISTRY
 The dental lasers in common use today are Erbium,
Neodynium, Diode, and CO2.
 Each type of laser has specific biological effects and
procedures associated with them.

Erbium Lasers
 Erbium lasers are built with two different crystals, the
Er:YAG (Erbium yttrium aluminum garnet crystal) and
Er,Cr:YSGG (Erbium chromium sensitized yttrium
scandium gallium garnet crystal).

 They do have different wavelengths, Er:YAG has 2940 nm
and Er,Cr:YSGG has 2780 nm.
 There is a significant water absorption difference between
these two wavelengths.
 Er:YAG wavelength is at the peak of water absorption in
the infrared spectrum whereas the Er,Cr:YSGG exhibits less
absorption

 The Er,Cr:YSGG has also been shown to have significantly
deeper thermal penetration in tooth structure

 The erbium lasers are hard and soft tissue capable
 Their primary chromophore is water, but hydroxyapatite
absorption occurs to a lesser degree

 Photothermal interactions predominate in soft tissue
procedures and photodisruptive in hard tissue procedures.
 Thermal relaxation is excellent and very little collateral
thermal damage occurs in tissues

 Bone cutting with erbium lasers results in minimal thermal
and mechanical trauma to adjacent tissues.
 Atraumatic effect and excellent healing response
 Very short laser pulses of 50 to 100 microseconds are
typically used for hard tissue procedures.

SOFT TISSUE LASER
 The main parameters that differ from hard tissue uses are
much longer pulse durations (300-1000 microseconds) and
less or no water spray.
 There will be thermal relaxation and minimal heat
penetration into underlying tissues

Nd:YAG Lasers
 Nd:YAG lasers were the first types of true pulsed lasers to
be marketed exclusively for dental use in 1990.
 They are a near infrared wavelength of 1064 nm.
 This wavelength is absorbed by pigment in the tissue,
primarily hemoglobin and melanin

 Photothermal interaction predominates and the laser
energy here can penetrate deeply into tissues.
 Contact and noncontact mode are both utilized depending
on the procedure being performed.

 Nd:YAG also have excellent biostimulative properties.
 Nd:YAG lasers have the unique capacity to stimulate fibrin
formation.
 This effect is maximized when the pulse duration is set at
650 microseconds

 These lasers are primarily used for periodontal treatments.
 Their proclivity for pigmented tissue allows for effective
debridement and disinfection of periodontal pockets.

 Bacterial decontamination in tissues treated with Nd:YAG
laser energy also contributes to resolution of periodontal
infection
 Nd:YAG lasers can also be used for multiple soft tissue
procedures such as gingivectomy, frenectomy, impression
troughing and biopsy

Diode Lasers
 Diode lasers are becoming quite popular due to their
compact size and relatively affordable pricing.
 A specialized semiconductor that produces
monochromatic light when stimulated electrically is
common to all diode lasers

 A simple laser pointer is an example of a diode laser.
 Diode lasers can be used in both contact and non-contact
mode and can function with continuous wave or gated
pulse modes

 They are not capable of free running pulsed mode.
 Diode lasers are invisible near infrared wavelengths and
current machines range from 805 – 1064 nm.
 One exception is the Diagnodent caries diagnostic laser
which uses a visible red wavelength of 655 nm

 Diode lasers are used for soft tissue only.
 The chromophores are pigments such as hemoglobin and
melanin.
 Photothermal interactions predominate

 They are quite effective for gingivectomy, biopsy,, and
frenectomy, photobiomodulation

CO2 Lasers
 The CO2 laser is a gas-active medium laser
 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, is placed
at the end of the mid-infrared invisible nonionizing
portion of the spectrum, 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 tissue, which is
important when treating mucosal lesions,.

 In addition, it is useful in vapourizing dense fibrous tissue.
 There is rapid tissue interaction

 The CO2 laser cannot be delivered in a conventional optic
fiber.
 The laser energy is conducted through the waveguide and
is focused onto the surgical site in a noncontact fashion

 The loss of tactile sensation could pose a disadvantage for
the surgeon, but the tissue ablation can be precise with
careful technique.
 Large lesions can be treated using a simple back and forth
motion

 The noncontact mode thus has an advantage when treating
movable oral structures, such as the tongue and floor of the
mouth.
 This wavelength has the highest absorption in
hydroxyapatite of any dental laser, about 1000 times greater
than erbium

 Therefore, tooth structure adjacent to a soft-tissue surgical
site must be shielded from the incident laser beam
 usually a metal instrument placed in the sulcus provides
the protection

A portable hand-held CO2 laser system
 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

Uses of Lasers in orthodontics
 1.Laser etching
 2.Bonding
 3.Debonding of ceramic brackets
 4.Bracket mesh designing
 5.Efficacy of low level laser therapy in reducing
orthodontic post adjustment pain

 6.Lasers in holography
 7.Laser spectroscopy
 8.3D laser scanning
 9.Laser microwelding
 10.Effect of laser for demineralisation resistence

 11.Soft tissue lasers
 12.Mangement of impacted teeth
 13.Laser orthopedics
 14.Effect of low level laser in accelerated tooth movement

Laser Etching in Orthodontics
 Argon laser
 Krypton flouride excimer laser

Principle
 Splits the bond of organic and inorganic substances on the
surface.
 Explosive vapourization of water modifies the smooth
surface of enamel

 Due to the extremely short pulse length of some
nanoseconds and sudden removal,there is no efficient heat
conductance through the hard substance
 so no harmful increase in the temperature of the pulp.
Etched enamel by Er;YAG laser Etched by Malic acid

Bonding
 Argon laser is commonly used as light curing adhesives.
 The procedure for light curing is almost same as
conventional light curing

 The enamel surface was etched with 37% phosphoric acid
for 15 seconds
 The surface was treated with Megabond
 Adhesive precoated brackets were placed on enamel
surface
Mark Kurchak,Bernadette Desantos,John Powers,David Turner JCO 1997

 Laser tip was held 0.5mm from the bracket and the light
curing wand was kept touching the bracket.
 No enamel damage caused by argon lasers at energy levels
of 1.6 to 6 watts

Result
• The study demonstrates that 10 seconds of curing with
argon laser produces bond strength comparable to those
achieved with 20 to 40 seconds of curing with a
conventional high intensity light.
• The time savings involved in bonding a full arch is
significant with the help of Laser.

Laser Debonding of Ceramic Orthodontic
brackets
 Laser light has been shown to degrade resins by thermal
softening or photo ablation.
• Both polycrystalline alumina and single crystal alumina
(saphire) ceramic orthodontic brackets were bonded to the
labial surface of lower deciduous teeth with regular acid
etch technique.
Robert M Tocchio,Peter T Williams,Franz J Mayer,Kenneth G Standing)
AJO 1993

• The brackets were debonded by irradiating the labial
surfaces of the brackets with laser light at wavelengths
of,1060nm.
• Debonding times were measured and the surfaces created
by debonding were examined with both light and scanning
electron microscopy to determine the extent of bracket and
enamel damage

Results
• No enamel, bracket damage in any sample.
• The debonding of polycrystalline brackets is caused by
thermal softening of the bonding resin resulting from
heating of the bracket.
• The hot bracket then slides off the tooth

• Ideal debonding time – 0.5 seconds shows no pulp
reaction,
• No enamel tear outs and catastrophic bracket failures were
observed.
• Lasers used are Nd:YAG laser and carbon dioxide laser.

Newer Bracket Systems
 Newer brackets with laser reinforced structured bases
enable the force to be applied even closer to the crown.
 The base of brackets guarantees an excellent bond during
the entire treatment period

 Laser markings help in easy identification of brackets.
 Compared with conventional markings,laser markings
cannot be abraded and does not contain harmful colouring
agents

Accelerated Tooth movement
 Method of increasing tooth movement are ,Injection of
1. Prostaglandins
2. Active form of vitamin D3
3. Osteocalcin
4. Relaxin
 Side effects are local pain and discomfort

 Electric stimulation ,corticotomy and resonance vibration
 Requires complex apparatus

Low level laser therapy(LLLT)
 Fujita et al. (2008) and Yamaguchi et al. (2007) reported
that LLLT stimulated the velocity of tooth movement via
RANK and c-Fms gene expressions in vitro
 This was confirmed by Yamaguchi et al. (2010) which
showed that LLLT accelerates the process of bone
remodeling by stimulating MMP-9, cathepsin K, and
integrin subunits.

 Study conducted by Gauri Doshi-Mehta and Wasundhara
in 2012 at Nagpur showed 56%increase in rate of tooth
movement in first 3 months and later 30%
Gauri Doshi,Wasundhara,AJODO 2012

Reducing orthodontic post adjustment pain
Methods
1. TENS
2. Low level laser therapy
3. Vibratory stimulation

Low level laser therapy
 LLLT has been shown to produce analgesic effects
 Here the energy output is low enough so as not to cause a
rise in the temperature of the treated tissue above 36.5
degrees centigrade

 Biostimulatory effects of LLLT have been attributed to its
anti inflammatory and neuronal effects.
 Harris proposed that LLLT has benign stimulatory
influence on depressed neurons and lymphocytes

• Stabilization of membrane potential and release of neuro
transmitters.
• Laser unit used was Galium diode laser

Laser Holography
 Hans Rydin and Bielkhagen(1982) developed a new method
for comparing the tooth positions on the dental casts at
different stages.
 Holograms of the casts were prepared using Helium Neon
laser

 Burstone C.J.,T.W.Every and R.J.Pryputneiwiz (1982)based
on pulsed laser hologram inferometry studied the
dynamics of incisor extrusion

Procedure
 The output from the laser is split into two parts by beam
splitter.
 One part was expanded by a beam expander and is used to
illuminate the object.
 The scattered wave from the object is called object wave.

 The second part was expanded by a beam
expander,reflected by a mirror and a wave called reference
wave is formed which forms the hologram

Laser spectroscopy
 Used in the field of dentistry for the purpose of analyzing
the surface structures of dental materials
 Used for evaluating the surface roughness of orthodontic
wires, brackets, comparison of materials, surface changes
of orthodontic materials

3D LASER SCANNING
 Obtains 3D surfaces by gathering measurements made by
smoothly sweeping a handheld laser scanning wand over
an object
 Similar to spray painting

 The object's image instantly appears on computer screen
 Finished scan is processed to combine any overlapping
sweeps
 Significantly reducing the time to develop surface models

 The scanner works by casting a fan of laser light over the
object, while the camera on the wand views the laser to
record a cross-sectional profile of the object.
 The software is used to determine the position and
orientation of the wand enabling the computer to
reconstruct the full three-dimensional surface of the
object.

LASER MICRO WELDING
 Laser welding produces deep penetration
welds with minimum heat effective zones.
 Laser welding has the advantage of welding
dissimilar metals while producing very low heat

 The process is a non-contact one that directs laser outputs
of 2-10 kW into a very small area
 The laser beam makes a 'keyhole and the liquid steel
solidifies behind the traversing beam, leaving a very
narrow weld and heat affected zone

 The weld is approximately 1 mm wide and the surrounding
material is not distorted
 Because the weld bead is small, there is usually no need for
finishing or re-working and this reduces costs.

ORTHOPHASER
 Orthophaser Unit is bigger than the conventional spot
welder
 It provides highly superior result

 Almost all metals including the most recent and popular
titanium can be welded.
 The unit consists of working microscope with integrated
eye protections, flexible hand piece with a locking
mechanism for the hand piece and a compact control with
preprogrammed parameters
 The gas used in this is Argon

EFFECT OF LASERS FOR DEMINERLIZATION
RESISTANCE
 Exposure of enamel to laser irradiation imparts
some degree of protection against
demineralization under acid attack
 Using quantitative microradiography, argon laser
irradiation of enamel reduces the amount of
demineralization by 30- 50%.

 Fox et al found that, in addition to decreasing enamel
demineralization and loss of tooth structure, laser
treatment can reduce the threshold pH at which
dissolution occurs by about a factor of five.

 In sound enamel, calcium, phosphorus and fluoride ions
diffuse into the acid solutions and are released into the oral
environment
 With lased enamel, the microspaces created by laser
irradiation,trap the released ions and act as sites for
mineral reprecipitation within the enamel structure.
Lloyd Noel, Joe Rebellato, Rose D. SheatsAngle Orthod 2003;73:249–258
10 sec lased enamel 5 sec lased enamel Control group

 Thus, lased enamel has an increased affinity for calcium,
phosphate and fluoride ions
 This will prevent demineralization

SOFT TISSUE LASERS
 Soft tissue laser is an effective tool to help manage
treatment and enhance our aesthetic outcomes
 The soft-tissue laser can significantly reduce treatment
time by creating access for brackets/bands, improving
bracket placement by improving tooth proportionality, and
helping manage oral hygiene through removal of
pseudopockets

 Gingival aesthetics can be enhanced through shaping and
contouring the gingival tissue during treatment

MANAGEMENT OF IMPACTED TEETH
 Commonly, cuspids are the last teeth bonded due to slow
eruption, delayed passive eruption, or impaction.
 This will take long treatment time.
 It is a functional issue if the cuspids cannot be bracketed
ideally

 Archwire bends are required if the bracket cannot be
placed ideally, resulting in increased chair time and
difficulty in finishing treatment.
 The posterior occlusion is often hindered by delayed
passive eruption of the second premolars

 The diode laser can be used to assist the clinician in
avoiding these situations by going directly to attachment,
bracket, or band placement

LASER-ORTHOPEDICS
 Lasers can be applied to manipulation facial growth
 Study by Mostafa Abathi and Maryam in rabbits showed
irradiation TMJ by LLL during mandibular advancement
increases bone formation in condylar region
Abathi etal.Head and face medicine 2012

 They irradiated TMJ by 630 nm KIO3 laser for 3 weeks
 Found that increase in bone formation in condylar region,
while no increase in cartilage thickness and fibrous tissue

Laser Safety in Dental Practice
Tissue hazards
 Laser induced damage to the skin and other non target
tissue can result from thermal interaction of radiant energy
with tissue proteins
 Temperature elevations of 21 degrees centigrade above the
normal body temperature can produce cell destruction by
denaturation of cellular enzymes and structural proteins

• Histologically thermal coagulation necrosis is
produced.

 Char layer is formed
 char layer is a strong absorbent of different wavelengths of
laser light and the extent of collateral damage increases
with this layer.
 Mechanical removal of char layer is essential

Environmental hazards
• Potential inhalation of airborne hazardous materials that
may be released as a result of laser therapy.
• Some lasers contain inert gases (argon, krypton or xenon)
mixed with toxic gases such as fluorine or hydrogen
chloride as the active medium

• Inhalation of toxic material in the form of aerosols has
been found potentially damaging to the respiratory system.
• Standard surgical masks and surgical smoke evacuation
equipment is used in the theatre

 Greatest producers of smoke – carbon dioxide and Nd:YAG
laser

Combustion Hazards
• Flammable solids,liquids and gases used within the
surgical setting can be easily ignited if exposed to the laser
beam.
• The use of flame resistant materials and other precautions
therefore is recommended

Electrical hazards
• Electrical hazards of lasers can be grouped as electrical
shock hazards,electric fire hazards or explosion hazards.
• Insulated circuitry,shielding,grounding and housing of
high voltage electrical components provide protection
under most circumstances from electrical injury

Personal Protective Equipment
Eye protection
 lasers can cause occular damage by either direct viewing or
reflection of the beam.
 Adequate eye protection must be worn by the operator as
well as the patient.

 They are available in the form of safety goggles or screening
devices.
 Laser protective eyewear filters are specified according to
their optical density which takes into account the
wavelength,power and diameter of the beam

Laser filtration masks
 Prevents air borne contamination

Foot pedal control switch with protective hood
 Prevents accidental depression by surgical staff.

conclusion
 With technology and science reaching new heights it is
needless to say that lasers would soon become a necessity
in every field of science .
 Orthodontics has also been captured into this magical
spell of laser which would enable us to reach new goals

REFERENCES
1. Lasers in DentistryFrom Fundamentals toClinical
Procedures By:Dr. Donald J. Coluzzi
2. Basic Laser Principles , MELLESGRIOT
3. The Use of Lasers in Dentistry A Clinical Reference
Guide for the Diode 810 nm & Er:Yag
4. Introduction history of lasers,laser production,s.parker
,practice 1

5. Introduction history of lasers,laser
production,s.parker ,practice 2
6.Versatality of an 810 nm Diode laser in dentistry; An over
view.Samo piranat,Journal of laser and health
academy.vol.2007
7. Lloyd Noel, DMD, MSa; Joe Rebellato, DDSb; Rose D.
Sheats, DMD, MPHcAngle Orthod 2003;73:249–258

8. Hu Longa; Ujjwal Pyakurela; Yan Wangb; Lina Liaoa; Yang
Zhoua; Wenli LaicAngle Orthodontist, Vol 83, No 1, 2013
9.Elaut j,Weharbein Eur journal of orthodontics 26(2004)
10. C. Apel, J. Meister1,, R.S. Ioana Lasers Med Sci 2002,
17:246–252

11. David M. Sarver and Mark YanoskyAm J Orthod
Dentofacial Orthop 2005;127:262-4
12. Jasmina Primoz; Giuseppe Perinettib,Angle Orthodontist,
Vol 82, No 4, 2012
13. Y. Mahesh Kumara; N.S. RavindranbAngle Orthodontist,
Vol 79, No 2, 2009

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