Laser

LASERS IN ORTHODONTICS
www.indiandentalacademy.com

Laser Evolution
Laser devices have been used in the past two decades in countless
ways to benefit humankind.
LASER – Light Amplification by Stimulated Emission of
Radiation.
1917-Einstein-if a photon struck a molecule already in an excited
state the molecule would fall back to the lower energy and emit a
photon of exactly the same size and move in the same direction as
the entering photon.
1957-Townes-amplify microwave frequencies-MASER –
“Microwave amplification of stimulated emission of radiation”.

1958 – Schawlow and Townes-extended MASER principle to the
optical portion of the electromagnetic field.
1960 – Theodore Hurold Maiman-first succesful operation of a
laser device using a synthetic ruby made from aluminium oxide
doped with chromium oxide.

Laser Physics
What are photons?
The basic units or quanta of light- photons.
A quantum of light can be depicted as an
electromagnetic wave with an electric field
oscillating up and down in the plane of the page.
Speed- 1 foot/nanosecond ( 1 ns = 1 billionth of a
second).

Light Absorption and Emission:
When light encounters matter – deflected or absorbed.
If a photon is absorbed - energy is not destroyed – but used to
increase the energy level of the absorbing molecule.
Atom absorbs photon
Photon ceases to exist and an electron
within atom jumps to higher energy level
Atom pumped up to an excited state from
resting ground state
Atom unstable and spontaneously decay back to
the ground state releasing stored energy in the
form of emitted photon.
“Spontaneous emission”www.indiandentalacademy.com

Light amplification by stimulated emission of radiation
Lasing occurs when an excited atom can be stimulated to emit a
photon before the process occurs spontaneously.
When a photon of exactly the right wavelength enters the
electromagnetic field of an excited atom,the incident photon
triggers the decay of the excited electron to lower energy state.
Release of stored energy in the form of second photon.
Stimulated emission occurs when the incident photon has
same energy as released photon.If a collection of atoms
include more that are pumped into excited state than resting
state,a population inversion exists.-ideal condition for lasing.www.indiandentalacademy.com

The spontaneous emission of a photon by one atom will
stimulate the release of a second photon in a second atom
and these two photons will trigger the release of two more
photons.
These four then yield eight; eight yield sixteen and so on.
A brief intense flash of monochromatic ( same wavelength)
and coherent (same phase) light is produced.

Principle of Laser
Laser works on the principle of generation of
monochromatic,coherent and collimated radiation by a suitable
medium in an optical oscillator.
Monochromatic:-
Laser light is characterized by radiation in which all waves have same
frequency and energy.
Coherent:-
All waves are in a certain phase relationship.
Collimated:-
All emitted waves are near by parallel and the beam divergence is
very low.

Components of Laser devices:-
Laser medium
• Solid
• Liquid
• Gas
This medium determines the wavelength of the light emitted from
the laser and the laser is named after the medium.
An Optical cavity or Laser Tube
It consists of two mirrors,one fully and the other partially
transmissive which are located at either end of the optical cavity.
Some form of External power source
This is necessary to excite the atom in the laser medium to a higher
energy level for population inversion to take place.www.indiandentalacademy.com

Classification of Lasers
According to mode of emission
•Fractioned
•Continuous
•Pulsed
According to power
•High power laser
•Medium power laser
•Low power laser

According to emitting material
•Gas laser
•Solid state laser
•Dye laser
•Semi conductor diode laser
•Ring laser
The Carbon dioxide laser
The lasing medium contains a mixture of carbon
dioxide,nitrogen and helium gases.
Nitrogen molecules are pumped up with energy from
an electric discharge applied to the lower tube.

Solid state lasers:
In solid state lasers,the lasing medium is suspended in a
transparent crystal.A garnet crystal made from yttrium and
aluminium is commonly used in a variety of surgical lasers
call YAG lasers.
YAG lasers can be used in combination with three rare earth
elements,neodymium,holmium and erbium.
Each element has a different arrangement of electron orbitals
so that lasing occurs at different wavelengths for each.
Argon laser:
It is one of the rare gas ion lasers capable of outputs of
several watts continuous light in the visible green and blue
portion of the spectrum.The active lasing medium is argon
gas. www.indiandentalacademy.com

Laser interaction with biologic tissues
When radiant energy is absorbed by tissue,four basic types of
interactions or responses can occur.
Photochemical interactions
Photochemical interactions include bio stimulation which describes
the stimulatory effects of laser light on biochemical and molecular
processes that normally occur in tissues such as healing and repair.
Photodynamic therapy which is the therapeutic use of lasers to induce
reactions in tissues for the treatment of pathologic conditions and
phosphorescent re emission or tissue fluoroscence-used as a
diagnostic method to detect light reactive substances in tissue.
Photothermal interactions
Photothermal interactions manifest clinically as photo ablation or the
removal of tissue by vaporization and super heating of tissue
fluids,coagulation and hemostasis and photopyrolysis.

Photomechanical Interactions
Photmechanical interactions include photodisruption or
photodissociation which is the breaking apart of structures by
laser light and photo acoustic interactions which involve the
removal of tissue with shock wave generation.
Photoelectrical Interactions
Photo electrical interactions include photo plasmolysis which
describes how tissue is removed through the formation of
electrically charged ions and particles that exist in a semi
gaseous,high energy state.

Laser Effects on Dental Hard Tissues
Thermal effects
The best known laser effect in dentistry is the thermal vaporization
of tissue by absorbing infrared laser light.The laser energy is
converted into thermal energy or heat that destroys the tissues.At
100 degrees centigrade the water inside the tissue vaporizes.The
absorption of the laser energy increases rapidly.
Mechanical effects
High energetic and short pulsed laser light can lead to a fast
heating of the dental tissues in a very small area.High and fast
shock waves lead to mechanical damage of the irradiated tissue.

Chemical effects
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.
Molecules can be dissociated directly with laser light of high
photon energies.

Enamel surface response to laser ablation
Carbon dioxide medium:-
Surface fusion,roughness,etching,partially fused
crystallites,charred,cracking.
Nd:YAG:-
Terraced surface,rough fused crystallites,charred,cracking.
Argon:-
Reflection of beam produces minimal effect on enamel surface.
Ruby:-
Cratering,irregular cavitation surface,charred.

Uses Of Lasers in Dentistry:-
Argon laser:
• Root planing and curettage
• Oral lesion therapy
• Laser Tissue welding-fusing vascular tissues by laser thermal
welding and for coagulation and hemostasis of bleeding
vessels.
Carbon dioxide laser:-
• Biopsies
• Tongue lesions
• White lesions – vesiculobulbous and premalignant lesions.

• Aphthous ulcers
• Herpetic lesions
• Coagulation
• Exposure of Implants
• Distal wedge and tuberosity reduction
• Hypersensitivity
• Pre prosthetic surgery
• Malignant lesions
• Gingival troughing
Er:YAG laser:-
• Removal of dental filling materials
• Bone ablation and oral soft tissue ablation.www.indiandentalacademy.com

Orthodontic applications of laser:
•Gingivectomy/gingivoplasty
•Frenectomy
•Temperomandibular disorders
•Low level laser therapy for arthritic cases
•Pain control with LLLT
•Etching
•Bonding
•Debonding
•Newer brackets with laser cut bracket bases
•Holographic studies

Laser Etching in Orthodontics
Laser etching can be done with the help of various types of
lasers such as Argon laser,Krypton flouride excimer laser and
so on.
Arf-193nm,Krf-248nm,Xecl-308 nm
Principle
The high performance density leads to a locally restricted very
strong and fast interaction with the irradiated material that
splits the bond of organic and inorganic substances on the
surface.This process of microexplosion is called photoablation.
Due to the extremely short pulse length of some nanoseconds
and sudden removal,there is no efficient heat conductance
through the hard substance which shows that there is no
harmful increase in the temperature of the pulp.www.indiandentalacademy.com

Bonding
Argon laser for light curing adhesives (Mark
Kurchak,Bernadette Desantos,John Powers,David Turner)
JCO 1997
•The enamel surface was etched with 37% phosphoric acid
for 15 seconds.
•The surface was treated with Megabond.
•Adhesive precoated brckets were placed on enamel
surface.
•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 strenghts
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.

Bond strengths of two ceramic brackets using argon
laser,light and chemically cured resin systems
(Sergio J Weinberger,Timothy F Foley,Robert J
McConell,Gerald Z Wright) AJO 1998
Three methods were used to bond the brackets to the teeth.
•First method consisted of a light cured microfilled resin and
laser energy for curing.
•Second method consisted of light cured microfilled resin and
visible light curing unit for curing.
•Third method involved a one step no mix chemically cured
adhesive.
•Debonded samples were examined under a stereo microscope
and bond strengths measured with the help of Instron machine.www.indiandentalacademy.com

Result
•There were no differences noted in the bond
strength between light and laser cured brackets.
•Upon debonding,no enamel fractures occurred
among chemically cured brackets.Light and
laser cured brackets exhibited a 10% rate of
enamel fracture on debonding.

Laser Debonding of Ceramic Orthodontic brackets
(Robert M Tocchio,Peter T Williams,Franz J Mayer,Kenneth G
Standing) AJO 1993
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.
•Under externally applied stress of 0.8Mpa,the brackets were
debonded by irradiating the labial surfaces of the brackets with laser
light at wavelengths of 248nm,308nm,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.www.indiandentalacademy.com

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,Pulp
irritation increases only with increased lasing time.
•No enamel tear outs and catastrophic bracket failures were
observed.
•Lasers used are Nd:YAG laser and carbon dioxide laser.
•Porosity suggestive of gas production in a molten resin was
observed in a few locations.

Newer Bracket Systems
Newer brackets with laser reinforced structured bases enable the
force to be applied even closer to the crown.
The patented laser structured base of brackets guarantees an
excellent bond during the entire treatment period.
Laser markings help in easy identification of brackets.When
compared with conventional markings,laser markings cannot be
abraded and does not contain harmful colouring agents.

Efficacy of low level laser therapy ( LLLT) in
reducing orthodontic post adjustment pain
LLLT has been shown to produce analgesic effects in many clinical
applications.
Terminology included soft laser,mid laser,low energy laser,cold
laser.
Defined as laser treatment in which 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 or normal body temperature.
Biostimulatory effects of LLLT have been attributed to its anti
inflammatory and neuronal effects.
Harris proposed that LLLT has benign stimulatory influence on
depressed neuronal and lymphocyte respiration.

•Stabilization of membrane potential and release of neuro
transmitters.
•Laser unit used was Class 3B Galium diode laser probe with
a wavelength of 830 nm.
Result:
Although LLLT was found to be unable to provide immediate
pain relief,it could have a potential in reducing the intensity
of pain during its time course with just one or two
applications.

Laser in 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.www.indiandentalacademy.com

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 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.
• During ablation of oral tissue with carbon dioxide laser a
carbonized layer of tissue or char layer forms.This 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.www.indiandentalacademy.com

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
•Flammable materials found in dental treatment areas.
Solids Liquids Gases
Clothing Ethanol Oxygen
Paper Products Acetone Nitrous oxide
Plastics Methylmethacrylate General anesthetics
Waxes and Resins Solvents Aromatic Vapours

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
Light produced by lasers presents potential hazard for 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.www.indiandentalacademy.com

Laser

More Related Content

What's hot (20)

Similar to Laser (20)

More from Indian dental academy (20)

Recently uploaded (20)

Laser