Lasers can be used for nonsurgical periodontal therapy by using it for preprocedural decontamination to reduce bacteria in the sulcus and aerosols, as well as for decontamination by removing biofilm from the pocket wall. It also allows for coagulation to seal vessels and inhibit biofilm progression after decontamination. Lasers interact strongly with inflamed tissues and can remove necrotic tissue and biofilm similarly to conventional debridement.

1. LASERS...
Archana. B

2. Acronym
“Light Amplification By Stimulated
Emission Of Radiation”

3. Principle of working of a laser
Absorption of
radiation is the
process by which
electrons in the
ground state absorbs
energy from photons
to jump into the
higher energy level.
Spontaneous emission is
the process by which
electrons in the excited
state return to the ground
state by emitting photons.
Stimulated emission is the process by
which incident photon interacts with
the excited electron and forces it to
return to the ground state.

6. To put it simply

7. Historical landmarks
In 1917, Albert
Einstein
established the
theoretical
foundations for
the laser - in the
paper Zur
Quantentheorie
der Strahlung (On
the Quantum
Theory of
Radiation)
In 1928, Rudolf
W. Ladenburg
confirmed the
existence of the
phenomena of
stimulated
emission and
negative
absorption
in 1939, Valentin
A. Fabrikant
predicted the
use of
stimulated
emission to
amplify "short"
waves
In 1950, Alfred
Kastler (Nobel
Prize for Physics
1966) proposed
the method of
optical
pumping,
experimentally
confirmed, two
years later, by
Brossel,
A maser is a
device that
produces
coherent
electromagneti
c waves
through
amplification by
stimulated
emission. The
first maser was
built by Charles
H. Townes
Theodre H
Maiman
First LASER
(Ruby Laser
1960)
Leon Goldmann
Father of LASER
Medicine

9. Properties
• MONOCHROMATICITY - Laser light is mono-chromatic, meaning that
the light energy is concentrated within a very tight
spectral (wavelength) band.
• DIRECTIONALITY- Unidirectional
• COHERENCE
• BRIGHTNESS – Extremely High Intensity of light due to Collimation
Overlapping

10. Tissue Interactions
• Absorption – Specific molecules in the tissue known as chromophores absorb the photons. The light
energy is then converted into other forms of energy to perform work.
• Reflection – The laser beam bounces off the surface with no penetration or interaction at all. Reflection
is usually an undesired effect, but a useful example of reflection is found when Erbium lasers reflect off
titanium allowing for safe trimming of gingiva around implant abutments.
• Transmission – The laser energy can pass through superficial tissues to interact with deeper areas.
Retinal surgery is an example; the laser passes through the lens to treat the retina. The deeper
penetration seen with Nd:YAG and diode lasers is an example of tissue transmission as well.
• 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.

11. Classification
1. According to ANSI & OHSA
standards
Class 1 lasers are considered incapable of
producing damage and are exempt from any
control measures or other forms of
surveillance.
Class 1M lasers are safe during normal
operation, but can be dangerous if viewed with
an optical instrument, such as an eye loupe or
a telescope.

12. Class 2 lasers emit radiation in the visible
spectrum (400–700nm) and eye protection is
afforded by the aversion response, which is
usually 0.25 seconds.
Class 2M potentially dangerous if viewed with
certain optical aids
Class 3 is divided into 3R the R stands for
reduced requirements and 3B.
3B lasers can cause hazards under direct and
specular reflection. A Class 3B laser can cause
eye injury. The more powerful the laser, the
greater the chance of injury.

13. Class 4 lasers are a hazard to the eyes or skin
and may pose a diffuse reflection or fire
hazard.
Class 4 lasers may also produce laser-
generated air contaminants and hazardous
plasma radiation. The Lasers we use

15. 2. Based on the type of laser medium used
Lasers are classified into 4 types
based on the type of laser
medium used:
• Solid-state laser- cerium (Ce),
erbium (Eu), terbium (Tb)
• Gas laser- Helium (He) – Neon
(Ne) lasers, argon ion lasers,
carbon dioxide lasers (CO2 lasers)
• Liquid laser - A dye laser
• Semiconductor laser – Diode Laser

16. 3. CLASSIFICATION BASED ON WAVELENGTH

17. 4. Based on the emission mode
• Continuous wave mode
• Gated pulse mode
• Free running pulsed mode

18. Based on the penetration power of the beam
Soft Tissue
Hard Tissue
Soft
Tissue

19. Hard
Tissue

20. Soft
Tissue

21. Hard
Tissue

22. Soft
Tissue
Soft
Tissue

23. Biological effects of Laser in
tissues
• 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.

24. • Laser Doppler Flowmetry
- To monitor pulpal and gingival blood flow
- To assess tooth vitality
• Laser Doppler Vibrometry - LDVs are used in the dental
industry to measure the vibration signature of dental
scalers to improve vibration quality.

26. • 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.
• Photothermal ablation is also at work when CO2 lasers
are used on teeth as hard tissue is vaporized during
removal. Heat is generated during these procedures and
great care must be taken to avoid thermal damage to
the tissues.

27. Selective photothermolysis
• Precise laser tissue interaction in which the radiation is well
absorbed and the pulse duration is shorter than the
thermal relaxation time, which minimizes tissue damage.
• This used in periodontal Pocket to inhibit bacterial
colonozation is called “Pocket thermolysis”

28. • 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.

29. • Erbium lasers' high ablation efficiency results from
these micro-explosions of superheated 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. Thermal damage is very
unlikely as almost no residual heat is created when
used properly, particularly when the concept of
thermal relaxation is considered.

30. Laser and a chromophore
• Chromophore: Chromophore is a material, present either endogenous in the tissues or
exogenous i.e. brought from outside, which absorbs particular wavelengths depending on
its absorption coefficient.
• Examples of endogenous chromophores are melanin, haemoglobin, (oxy haemoglobin,
de-oxyhaemoglobin and meth haemoglobin), water, protein, peptide bonds, aromatic
amino acids, nucleic acid, urocanic acid and bilirubin.
• Exogenous compounds like different colors of tattoo ink also act as chromophores.
• If there is no chromophore then all the photons will pass through the tissue without
producing any effect. This is total transmission. Therefore, selection of a proper
chromophore in or near the target tissue is a first important step in laser therapy

31. Photochemical reactions occur when photon energy causes a chemical reaction.
• This property can be utilized for breaking several chemical bonds which may be utilized for
antimicrobial therapy as in case of Photodynamic therapy

32. • Photodynamic therapy was discovered in 1900 by Oskar Raab and Hermann von Tappeiner
who found that Paramecium spp. protozoans were killed after staining with acridine orange
and subsequent exposure to bright light
• PDT was initially developed as a therapy for cancer after it was discovered that porphyrins
selectively localized in tumors
• Recently, antimicrobial PDT has been proposed as an alternative approach for localized
infections (St. Denis et al., 2011)
• Photodynamic therapy involves the use of a non-toxic light-sensitive dye called a
photosensitizer (PS) combined with harmless visible light of the appropriate wavelength
to match the absorption spectrum of the PS.
• After photon absorption the PS reaches an excited state that can undergo reaction with
ambient oxygen, resulting in the formation of reactive oxygen species (ROS)

34. Ideal requsites of Photosensitizers
• High degree of chemical purity.
• Stability at room temperature.
• Photosensitive effect only in the presence of a specific wavelength.
• High photochemical reactivity
• Absorption minimum in the range from 400 nm to 600 nm.
• Minimal cytotoxicity in the dark.
• Easy solubility in the tissues of the body.
• High selectivity for neoplastic tissues
• Inexpensive and simple synthesis and easy availability

35. Most of the sensitizers used for medical purposes belong to the following
basic structure:
• Tricyclic dyes with different meso-atoms. E.g.: Acridine orange,
proflavine, riboflavin, methylene blue, fluorescein, and erythrosine
• Tetrapyrroles. E.g.: Porphyrins and derivatives, chlorophyll,
phylloerythrin, and phthalocyanines
• Furocoumarins. E.g.: Psoralen and its methoxyderivatives, xanthotoxin,
and bergaptene

36. • Photofrin and hematophyrin derivatives are referred to as
first generation sensitizers.
• Second generation photosensitizers include
5-aminolevulinic acid (ALA), benzoporphyrin derivative,
texaphyrin, and temoporfin (mTHPC).
• These photosensitizers have greater capability to generate
singlet oxygen.

37. PDT modifications
• The latest knowledge indicates that nano-carriers modification and technology of
synthesis can significantly enhance drug delivery
• Komiyama et al. also proposed a functionalization of single DNAs to achieve
stronger DNA binding, DNA aptamers and DNAzymes.
• It means that we are able to develop intelligent systems which are programmable
assemblies of DNAs (so called DNA Origami) and efficiently use them for smart
drug delivery

38. • Photosensitizers of the next generation are also
PUNP type photosensitizers (Photon Upconverting
Nanoparticles).
• They are made of photosensitive compounds and
nanoparticles which core has the ability to convert
energy obtained from photons.
• The uniqueness of the system lies in the fact that the
radiation emitted by the core has higher energy than
the absorbed photon.

39. • Lipoproteins play an important role in the transport and
release of photosensitizer molecules to cancer cells.
• Several studies show that a photosensitizer bonded
noncovalently to LDL prior to administration leads to an
increase in PDT efficiency compared to the
administration of the photosensitizer itself

40. Electroporation
• Electroporation (EP) is a technique of
reversible or irreversible cell membrane
unsealing induced by electrical pulses. (J.
Gehl)
• The reversible EP variant is effectively applied
for enhancement of cell membrane
permeability to achieve easier transport of
drugs or to enable gene transfection

41. • 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, and
the like with various wavelengths.
• 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.

42. • Biostimulation is used dentally to reduce postoperative
discomfort and to treat maladies such as recurrent herpes and
aphthous stomatitis.
• Low Level Laser Therapy (LLLT) is another term used to describe
this phenomenon.
• When a dental laser is employed it can be used in contact mode
or non-contact mode. The laser tip directly touches the target
tissue in contact mode. In non-contact mode the laser is
pointed at a distance from the target tissue anywhere from a
few millimeters, such as in operative dentistry, or up to several
centimeters when performing biostimulation.

43. • In 1967, Endre Mester noticed that applying laser light to the backs of shaven mice could
– induce the shaved hair to grow back more quickly than in unshaved mice.
– could stimulate wound healing
• LLLT involves exposing cells or tissue to low levels of red and near infrared (NIR) light, and is
referred to as “low level” because of its use of light at energy densities that are low
compared to other forms of laser therapy that are used for ablation, cutting, and thermally
coagulating tissue.
• According to Genovese, biological effects caused by low level lasers are due to low
energy deposited into tissues where deposited energy results in primary, secondary and
general therapeutic effects. This results in the analgesic and anti-inflammatory effects
as well as in improvement in healing

44. LLLT acts according to the Arndt-Schulz principle which states that if the stimulus is too
weak, no effect is seen. Increased stimulation and optimal dose leads to the optimal effect;
while, further dose increase leads to a decreased effect. Additional stimulation leads to the
inhibition of stimulation

46. A few Studies supporting LLLT
• Reduction of discomfort / pain (Kreisler
MB et al 2004).
• Promotion of wound healing (Qadri t et
al 2005).
• Bone regeneration (Merli LA et al 2005).
• Suppression of inflammatory process.
(Qadri T et al 2005).
• Activation of gingival and periodontal
ligament fibroblast
• (Kreisler M et al 2003), growth factor
release (Saygun I et al 2007).
• Alteration of gene expression of
inflammatory cytokines (Safavi SM et al
2007).
• Photo biostimulation (Garcia et al 2012)

54. In Medicine
Lasers are often used to:
• Treat varicose veins
• Improve vision during eye surgery on the cornea
• Repair a detached retina of the eye
• Remove the prostate
• Remove kidney stones
• Remove tumors
• Lasers are also often used during skin surgery.

55. • Lasers are used for photocoagulation of the retina to
halt retinal hemorrhaging and for the tacking of the
retinal tears, Higher power lasers are used after
cataract surgery if the supportive membrane
surrounding the implanted lens becomes milky.
• Lasers are used in the eye surgery, the refractive
surgery, the soft tissue surgery, laser scalpel and the
photobiomodulation (the laser therapy), Lasers are
used in the “No-Touch” removal of the tumors,
especially the tumors of the brain and the spinal cord.

56. Transmyocardial Laser
Revascularization
• Angina is heart disease when lower left
ventricle muscles of heart doesn’t recieve
oxygenated blood therefore increase the risk of
heart attack and cause painful condtion
• Laser drilled small holes from ventricle into
myocandium allowing blood to flow directly
into the heart muscle without the need to
travel through blocked coronary arteries

57. Lasers In Periodontics

58. Laser-Assisted Nonsurgical Periodontal
Therapy
• Preprocedural Decontamination
Preprocedural decontamination is a laser application done before any
instrumentation, even probing. The objectives are to eradicate the
bacteria within the sulcus, thereby reducing the risk of bacteremia
from instrumentation, and to lower the micro count in aerosols
created during ultrasonic instrumentation. (Assaf et al 2007)

59. • Decontamination
Just as conventional root debridement removes biofilm and accretions from the hard tooth surface, laser
decontamination removes biofilm within the necrotic tissue of the pocket wall. The laser energy interacts
strongly with inflamed tissue components (Coluzzi DJ t al 2007)
• Coagulation
When biofilm has been removed, the second objective in active phase I periodontal infection therapy is
coagulation, sealing the capillaries and lymphatics of the healthy tissue. As previously noted, biofilm tends to
continue its invasion of the host tissue through the vessels. Coagulation may inhibit the biofilm’s progression. It
also counteracts the swelling that occurs with the inflammatory process
• Sulcular Debridement with Carbon Dioxide Laser
The micropulsed 10,600-nm CO2 laser uses a defocused, noncontact technique. Marginal dehydration and
pocket decontamination are two steps applied in CO2 laser therapy. Because the CO2 laser’s wavelength
is absorbed by the crevicular fluids and water content in the diseased tissue wall, it is important to direct
the energy parallel to the tooth surface and toward the tissue

61. Application of photodynamic therapy
• PDT can be considered as an adjunctive to
conventional mechanical therapy.
• The technical simplicity and effective bacterial
eradication are the two reasons why PDT is
extensively studied in periodontics.

62. • Antimicrobial PDT not only kills the bacteria but may also lead to
the detoxification of endotoxins such as lipopolysaccharide.
• These lipopolysaccharides treated by PDT do not stimulate the
production of proinflammatory cytokines by mononuclear cells.
• Thus, PDT inactivates endotoxins by decreasing their biological
activity. (Wilson M et al)

63. • Scaling and root planning is to be carried out before PDT.
• While doing the PDT, the photosensitizer is first infused in
the periodontal pocket and allowed to pigment for 2 min.
• Then the fiber is inserted 1 mm short of the pocket and
lased by moving in a sinusoidal manner from side to side
toward the coronal third.

68. Lasers in Surgical Periodontics
• Gingivectomy
Clinical observation demonstrates that resecting gingiva with
a laser enhances access because of increased visualization
resulting from sealing of capillaries and lymphatics during
laser irradiation. In the early stage of tissue healing with use
of blades, inflammation is noted, along with collagen
production and epithelialization, and the wound has a high
tensile strength.

69. • The laser wound generally demonstrates delayed
epithelialization, collagen production, and inflammation,
with a lower tensile strength. In later phases of healing,
however, the process accelerates, with collagen production
and epithelialization.
• Myofibroblasts are present in fewer numbers during
healing of a laser-resected wound site, which leads to less
wound contraction and less scar formation (Fisher S, et al)
• Laser settings create a so-called laser bandage (settings
of low wattage, no water, and some air, with fewer
pulses per second).

70. • Frenectomy
The clinician should first visualize the procedure by forming a mental outline of the incision.
This incision begins at the coronal attachment; the laser tip is then moved unidirectionally,
with tension achieved by pulling on the lip. With use of the correct parameters (spot size,
power, hand speed), one pass of the laser should be sufficient to sever all of the fibers. If
multiple passes are necessary, care must be taken to avoid excessive lateral thermal necrosis
from reexposure of already-treated tissue. The laser incision is continued to undermine the
muscle attachment until the periosteum is reached.

71. Though scalpel remains the gold standard
choice in gingivectomy but Diode laser may
have some advantages over it.

72. • Mucogingival Surgery
Lasers can be used in mucogingival procedures for a variety of therapies. Donor
material can be acquired from the palate or other keratinized areas in the oral cavity
with laser therapy. Using a laser to “seal” the wound when donor material is taken from
these areas using blades can reduce hemorrhage significantly

76. Lasers In Periodontal Therapy
• Patients needing standard periodontal
treatment with pocket depth (PD) ≥4 mm are
indicated for LANAP (Katuri KK et al)

77. • An optic fiber tip measuring 0.3-0.4 μ is placed parallel to the root surface,
to carry away the epithelium lining of the pocket in coronal to apical motion
to reflect the gingival flap. The first pass laser or troughing dissipates energy
at 4 W, free running 100 milliseconds pulse expels the unhealthy lining of
the pocket. The duration of the pulse is short.
• Calcified plaque adherent to the root surface is removed.
• Selective photothermolysis removes unhealthy, infected and inflamed
epithelium of the pocket sparing the intact connective tissue separation of
the layers of tissues at rete pegs and ridges level.

78. • The second pass with a variation in parameters, energy dissipation at 4 W
650 milliseconds pulse allows reentry of the pocket. This establishes a
sticky fibrin blood clot which secures the pocket from detritus matter and
perpetuates healing from inside out.
• The pocket is closed by compressing gingival tissues against the root
surface which creates a firm fibrin clot. No placement of sutures or
surgical glue. Splinting of grade II mobile teeth if needed.

81. LANAP, when compared to conventional periodontal surgery, provided some elusive
advantages like,
• Minimally invasive with better patient compliance
• Decreased postoperative pain and morbidity
• Less likely to develop hypersensitivity
• Less prone to recession
• Faster healing
• Natural teeth as well as implant both show regeneration of the surrounding
tissues

82. • Yukna et al, conducted one of the most valid histological studies and were the first
to publish and prove, positive results of LANAP therapy in comparison with
traditional periodontal surgery.
• McAllister conducted a study in 2009 on 3 cases which were conclusive of positive
results of LANAP using the Nd:YAG PerioLase MVP-7 laser for the treatment of
moderate-to-severe adult periodontitis in routine dental practice. All three cases
reflected clear radiographic bone regeneration following LANAP. He concluded that
LANAP unveils a less invasive approach and shows better patient compliance

83. • A study by McCraken could show that the combination of LANAP protocol
and orthodontics is a truly innovative concept and has quite positive
outcomes
• Food and Drug Administration 510(k) approved PerioLase MVP-7 in 2016
as the only appliance in medicine and dentistry with which regeneration
of the cementum mediated attachment apparatus could be achieved
when LANAP protocol was followed.

84. LANAP and Implants
• McCarthy brought forth the concept of LAPIP, “Laser-Assisted Peri-Implantitis
Procedure” as a modification of LANAP which could be used in diseased implants.
• Laser, removes inflamed pocket tissue, disrupt biofilms, and decontaminate the
root/implant surface.
• Decrease in inflammation and a laser-induced hemostasis further decontaminates the
tissue creating a durable blood clot to close the system.
• LAPIP brings back diseased structure to healthy states, promotes bone and tissue
regeneration, and the most commendable feature is that the procedure is performed
on implant without damaging it.

85. • A single appointment might be sufficient. Since no flap is reflected,
it even leaves chances for other therapies in the future. The LAPIP
protocol recommends the PerioLase MVP-7, a Nd:YAG “free-
running” pulsed laser, to treat periimplantitis.
• Giannelli et al conducted a study on the effects of Nd:YAG laser an
In vitro study. He concluded that the use of Nd:YAG laser appears as
a solution to treat periimplantitis.

87. LCPT
• Aoki et al. in 2010 proposed the concept of
‘LASER-ASSISTED COMPREHENSIVE POCKET
THERAPY in The 12th congress of the World
Federation for lasers Dentistry (WFLD). Dubai

88. Expected simultaneous photo biomodulation effects activating the surrounding
gingival and bone tissues from the inside by low-level laser penetration during
pocket irradiation.
Laser-assisted debridement (or laser-only debridement)
following mechanical instrumentation (curettes and
ultrasonic scalers) of the diseased root surface for removal
of the deposited subgingival calculus and
decontamination and detoxification of the root surface.
Ablation of lining epithelium and diseased connective tissue on the
inner surface of the gingival tissue as well as diseased connective tissue
in the vertical bone defect during pocket irradiation for comprehensive
treatment, in combination with mini-curette and/or mini bone curette,
which aims for thorough decontamination of the whole pocket and
increased bleeding in the bone defect from bone surface, which may be
advantageous for tissue regeneration.

91. Laser microstructured
Implants
Laser grooved –
Laser Lok

94. Laser Hazards
• Martin Strassl said “Only twice you can make
mistake with Lasers, First you lose one eye and
second the other”

95. LASER HAZARDS IN DENTAL PRACTICE
Ocular injury:
- retinal and corneal injury
( 400 – 780nm visible, 780 – 1400 infrared)
Tissue hazards:
- >21oC above normal body temperature leads to cell destruction and
denaturation of cellular enzymes and proteins
- Happens if by mistake hands come in the way of path of laser
- Should change the laser to the standby mode whenever
interruption in laser use is encountered

96. • Environmental hazards:
- inhalation – resp. system
- Smoke, the byproduct of laser surgery
- Laser plume
– Steam, carbon particles and cellular product
– Contains many toxic substances such as
formaldehyde, hydrogen cyanide
Use of high volume laser smoke evacuation

97. Combustion hazard
• Flammable solids, liquids and gases within the surgical
settings
• Particular concern : flammable gases and endotracheal
tubes
due to their proximity during head and neck procedures.
• Use of polypropylene surgical gloves/drapes and use of
laser
safe endotracheal tubes

98. Electrical hazards:
• Grouped as electrical shock hazards/ electric fire
hazard/
explosion
• Insulated circuitry, shielding, grounding, housing
of high
voltage electrical components – adequate
protection

99. Laser Safety
• Recommended by ANSI
• Personal protection
- eyewear ( goggles and
safety glasses, saline
soaked gauze)
- clothing and masks
• Administrative controls
- standard operative procedures
- warning signs
- protective devices
- training and education
• Engineering controls
- equipments label
- key switch
- protective housing
- warning systems
- beam enclosures
• Special controls
- fire and explosion
- repair and maintenance
- fibre optic delivery system

100. Training and education
All staff members should receive objective and recognized training in the safety aspects of laser use within dentistry, as
with other specialties.
Dentists should use the devices within their licensed scope of practice, training and experience.
For personnel who work with Class 3b and 4 lasers, the training will included the following topics:
• The biological effects of laser radiation
• The physical principles of lasers
• Classification of lasers
• Basic safety rules
• Use of protective equipment
• Control of related hazards including electrical safety, fire safety, and chemical safety
• Emergency response procedures

102. Conclusion
• Lasers have emerged as powerful weapon in the hands of modern dentistry.
• But a clinician cannot afford to ignore potential risks associated with the use of
Lasers.
• It is most important for the dental practitioner to be aware of the nature of laser
hazards, procedures and safeguards that need to be implemented, have clinical
experience, and have received proper laser training.
• Most of the Laser injuries can be avoided by establishing an adequate safety policy
for the management and control of risks arising from the use of laser equipment.

103. THANKYOU.....!