Download Laser in dentistry

‫وقاية \ خامس اسنان‬
)3(‫ ساهر م‬.‫د‬
2017 \5 \9
Laser in Dentistry
The word laser has came from the abbreviation of: Light
Amplification by Stimulated Emission of Radiation. Laser has been
introduced in dentistry to overcome disadvantages of conventional
methods of dental procedures.
Terminology
Laser are named for the active medium that charged with energy
inside the laser unite to create laser light. For example:
- YSGG laser : yttrium, scandium, gallium and garnet.
- CO2 laser: CO2 gas
- Nd:YAG laser: Neodymium, Yttrium, Aluminum and Garnet.
- Ho:YAG laser: Holmium, Yttrium, Aluminum and Garnet.
- Er:YAG laser: Erbium, Yttrium, Aluminum and Garnet.
When the crystal is pumped with energy, a specific monochromatic
wavelength of light is emitted from the crystal and transferred to the
target tissue through a delivery system.
- YSGG laser wavelength 2,780 nanometers
- Nd:YAG laser 1.064 nanometers
- CO2 laser 10.600 nanometers
- Er:YAG laser 2.94 nanometer
Different lasers react with tissues in different manner depending on
their absorption coefficient
- Adiode laser effective on darker pigment and melanin
- YSGG laser effective on water and hydroxyapatite
Properties or Characteristics of Laser Radiation
1.
2.
3.
4.
Monochromaticity
Unidirectionality
Brightness
Coherence
Monochromaticity: All emitted photons are the same wave length,
energy of laser is concentrated at few discrete wave length W.L (usually
one ) which is used to selectively target a specific biological element in
the tissue ex; hemoglobine, water or melanin.
Unidirectionality: Laser light emission is contained in a narrow almost
parallel bundles and travels in a single direction .The divergence of a
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laser beam can be very small (insignificant), the laser light is highly
collimated which means that there is minimum loss of power along the
laser beam.
Brightness: As laser light travels in a parallel bundle ,so it maintains its
concentration, and thus is very intense light.
Coherent: The unique characteristic of laser light, they have nearly the
same wave length, the same direction and the same phase together, these
3 properties make the laser light coherent.
Laser effects on tissue :
1-Reflection:
The beam redirects itself from the surface, having no effect on the
target tissue.
2-Transmission:
Transmission of laser energy directly through the tissue with no
effect on the target tissue.
3- Scattering:
Scattering of the laser light, weakening the intended energy and
producing no useful Biological effect.
4- Absorption:
Absorption of laser energy by the target tissue which is the
desirable effect, the amount of energy that is absorbed by the tissue
depends on the tissue characteristics such as pigmentation , water
content, and on laser wave length and emission mode.
The principle of laser-tissue interaction are:
1. photo-thermal, which means the energy is transformed into heat
[surgical incision and excision ].
2. photochemical [curing of
composite resin, disinfection of
periodontal pockets and endodontic canals]
3. fluorescence [biological pigments absorb laser light] and this is useful
for caries detection.
Types of laser:
There are different types of laser that can be used in dentistry. Each
laser has a different spectrum of possible application. Laser system are
named after the material that is used to produce the IR radiation.
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1. GAS: laser of Carbon dioxide (CO2).
The CO2 laser can be used to perform surgical procedures within
the oral cavity. For hard tissue, the CO2 laser can be used to vaporize
small, superficial caries and seal the dental tubules.
2. Solid state: Erbium (Er), Neodymium (Nd), Er,Cr: YSGG
Erbium (Er): Various version of Erbium laser are currently used in
odontostomatology, because of it's evident potential in the treatment of
hard tissue (enamel, dentin, cementum and bone). The huge absorption by
both water and hydroxyapatite of the radiation at a wave length of
approximately 2.9 µm permits tissue removal with minimal or no damage
to the surrounding structure.
Neodymium (Nd): The pulsed ND: YAG laser was introduced in
odontostomatology in the 1990s, essentially for treatment of gingival
pocket. Another application is emptying and sterilization of the root
canals by introducing the fiber which, when it radiates the laser energy,
vaporizes and disinfects the canal, eliminating the risk of apical damage.
Er,Cr: YSGG: WaterlaseTM uses the HydrokineticTM process which
gently washes away decay with YSGG laser-energized water droplet.
HydrokineticTM energy is produced by combining a spray of atomized
water with laser energy.
The resulting waterlase energy gently and precisely removes a
wide range of human tissue including tooth enamel, and soft tissue with
no heat or discomfort in most cases.
3. Liquid dye laser: Liquid dye laser use a solution of complex dye
materials as the active medium. The pump source is an Argon laser.one of
the most important feature that dye laser offer is tenability, that is, the
wavelength of output beam can be varied by adjusting the inter-cavity
tuning element and by changing the type of dye used. Dye lasers are
chosen for application like spectroscopy.
Laser dentistry can be used for soft tissues (gums) and hard tissues
(teeth). Soft tissue laser dentistry includes:
1. periodontal (gum) therapy.
2. gum reshaping and contouring.
3. excision of small growth on the gums and lips.
4. crown lengthening, which eliminates "gummy" smiles by removing
excess gum tissue and exposing more tooth.
Hard tissue laser dentistry includes:
1. removal of decay within a tooth.
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2. preparation for fillings.
3. curing and hardening of composite fillings.
Benefits of laser dentistry
- Ability to do more than one procedure in a single appointment
- Less need for separate surgical appointment
- Increased bone healing
- Faster healing
- Less time in the dental chair
- Less noise than the traditional dental drill
- Reduced risk of infection
- Less bleeding
- Less need for anaesthesia or injection
- Reduced sensitivity
- Less post operative pain
- Better results
Clinical applications:
- DIAGNOdent laser
A DIAGNOdent laser caries detector is a machine that detect decay
and allows the dentist to eliminate decay earlier with smaller fillings. It
operates at a wave length of 655 nm. At this specific wave length, clean
healthy tooth structure exhibit little or no fluorescence, result in very low
scale readings on the display. However, carious tooth structure will
exhibit fluorescence, proportionate to the degree of caries, resulting in
elevated scale readings on the display of the DIAGNOdent. An audio
signal allows the operator to hear changes in the scale values.
- Cavity preparation:
The Er:YAG laser was tested for preparing dental hard tissues for
the first time in 1988. it was successfully used to prepare holes in enamel
and dentin even without water cooling.
- Caries removal:
Caries material contains a higher water content compared with
surrounding healthy dental hard tissue. Consequently, the ablation
efficiency of caries is greater than for healthy tissues.
- Restoration removal:
The Er:YAG laser is capable of removing cement, composite resin
and glass ionomer. Lasers should not be used to ablate amalgam
restorations because of potential release of mercury vapor. The Er:YAG
laser is incapable of removing gold crowns, cast restorations and ceramic
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materials because of the low absorption of these materials and reflection
of the laser light.
- Etching:
Laser etching has been evaluated as an alternative to acid etching
of enamel and dentin. The ER:YAG laser produce micro explosions
during hard tissue ablation that result in microscopic and macroscopic
irregularities. These micro irregularities make the enamel micro retentive
and may offer a mechanism of adhesion without acid etching.
- Treatment of dentinal hypersensitivity:
A comparison of the desensitizing effect of an ER:YAG laser with
those of a conventional desensitizing system on cervically exposed
hypersensitive dentin showed that desensitizing of hyper sensitive dentin
with an ER:YAG laser is effective, and the maintenance of a positive
result is more prolonged than with other agents.
- Caries prevention:
It is believed that laser irradiation of dental hard tissues modifies
the calcium to phosphate ratio, reduces the carbonate to phosphorous
ratio, and leads to the formation of more stable and less acid soluble
compounds, reducing susceptibility to acid attack and caries. Laboratory
studies have indicated that enamel surfaces exposed to laser irradiation
are more acid resistant than non-laser treated surfaces.
- Bleaching:
The objective of laser bleaching is to achieve an effective power
bleaching process using the most efficient energy source, while avoiding
any adverse effect. Power bleaching has its origin in the use of highintensity light to raise the temperature of hydrogen peroxide, accelerating
the chemical process of bleaching.
- Bacterial reduction:
Intracanal radiation absorbed by tissue substances produce a
thermal effect capable of eliminating microorganisms. The ability to
eliminate bacteria even in deep dentinal layers increases the success rate
of endodontic therapy of contaminated canals, avoiding periapical
surgery.
- Root canal treatment:
High-intensity lasers are capable of performing morphological
superficial changes on root dentin, influencing the permeability of the
walls and the adaptability of the root filling to the root dentin.
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- Intra canal soft tissue vaporization:
The potential of specific wavelengths to vaporize soft tissue allows
the removal of intracanalicular granulation tissue present in internal
root resorption cases. In addition, disinfection will be achieved in
contaminated root resorped canals due to the bactericidal effect of
interaction.
- Curing laser:
Another use of light in dentistry began with the advent of
photopolymerized dental composite materials. These composite were
used for anterior esthetic dental restorations and also for sealing the
occlusal pits and fissures in posterior teeth to reduce decay.
DISADVANTAGES OF LASERS
(1) Laser beam could injure the patient or operator By direct beam or
reflected light, causing retinal Burn.
(2) G.A. Is usually required for the patients Undergoing laser surgery.
(3) Combustion hazards.
(4) Removal of soft tissue overlying the bone can Damage the underlying
bone.
(5) It available only at big hospital & treatment is very expensive.
(6) Specially trained person is needed.
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