Laser basics[26239].pptx

Basic dental Laser
knowledge
Dr. Hanaa Mohammed El Shenawy
.. Professor of Laser applications in Dentistry, in oral surgery& medicine
department, National research Center Cairo
PhD degree in Medical and Biological Application of Laser Science

Introduction
Historical Perspective
Fundamentals of dental lasers
Laser Physics
Lasers in Dentistry
Endodontics ,Operative & Aesthetic Dentistry
Dental laser safety

Light
Amplification by
S timulated
Emission of
Radiation

Electromagnetic spectrum
 Generally, EM radiation is classified by
wavelength into electrical energy, radio,
microwave, infrared, the visible region we
perceive as light, ultraviolet, X-rays and
gamma rays.
 The behavior of EM radiation depends on its
wavelength. Higher frequencies have shorter
wavelengths, and lower frequencies have
longer wavelengths. When EM radiation
interacts with single atoms and molecules,
its behavior depends on the amount of
energy per quantum it carries.

A laser is a device that transforms
light of various frequencies into a
chromatic radiation in the visible,
infrared, and ultraviolet regions
with all the waves in phase capable
of mobilizing immense heat and
power when focused at close range

L.A.S.E.R
The solution that is looking
for the problem
Lasers can be ...
• based on solid, liquid, or gaseous media
• big or small, expensive or cheap
• high or low power,
• pulsed or continuous (CW)
• at wavelengths anywhere from the far
IR to the X- ray region

Laser Physics
 The electron may be in either of the two energy levels, thus:

Laser Physics
 If the electron is in the higher level it may fall down into the lower level.
In its doing this it must give up an amount of energy equal to the energy
difference between the two levels.
 Now we finally get to lasers. L.A.S.E.R. which can cause stimulated
emission in two more atoms to give four photons , and so on.

Laser consists of a lasing medium
contained with an optical cavity,
with an external energy source to
maintain a population inversion so
that stimulated emission of a
specific wavelength can occur,
producing monochromatic,
collimated and coherent beam of
light

 All dental lasers have emission wave
lengths of 0.5μm (500 nm) to 10.6μm
(10,600 nm)
 Within the visible or invisible infrared
non-ionizing EM range & emit thermal
radiation
 The dividing line between ionizing and
non-ionizing portion is on the junction of
ultraviolet and visible violet light

 Active medium – Gas, liquid or solid
 Contained in glass or ceramic tubes
 Energy – Electric current
 Mirrors are added to each end to increase
the back and forth movement of photons
 Thus increasing the stimulation of emission
of radiation

Laser Delivery Systems
 Coherent, Collimated beam of laser
light must be delivered to the target
tissue
 Two delivery systems that are
employed
Hollow Waveguide or Tube
Glass fiber optic cable

Flexible Hollow Waveguide (Tube)
 Has an interior finish mirror
 Laser energy is reflected along this tube
and exits through a hand piece
 Strikes the tissue in a non-contact manner
 An accessory tip of sapphire or hollow metal
can be connected

Glass Fiber optic cable
 More flexible than waveguide
Less weight and less resistance in movement
Smaller diameter (200-600 μm)
Glass component is encased in a resilient sheath
Fragile & can’t be bent in sharp angles
Used in contact and non-contact mode

Advantages
Thinner & flexible
Higher carrying capacity
Less energy degradation
Low power consumption
Non – inflammable
Light weight

Laser Emission Modes
 Dental lasers can emit light energy in 2
modalities
 Constant ON
 Pulsed ON/OFF
 In Constant or Continuous Wave, the beam is
emitted at one power
 In Gated Pulse Mode, there are periodic
alterations of laser energy (Blinking light)

 This is achieved by the opening and closing
of a mechanical shutter in front of the beam
path of a continuous wave emission
 All surgical lasers that operate in continuous
wave have this gated pulse feature
 Third mode is termed Free running pulsed
mode or True Pulsed
 In this large peak of energy of laser light is
emitted for a very short time

Laser – Tissue Interaction
 Laser light has four different interactions
with the target tissue
 Amount of energy absorbed by the tissue
depends on the tissue characteristics such
as pigmentation and water content

•Absorbed by tissues
and results and
light energy is
converted to
thermal energy
•Light travels in
different
directions,
absorbed over a
greater surface
area
•Causes less thermal
effect
• Light transfers
to tissue
without any
interaction &
injury
• Little or no
absorption
• No thermal
effect on Tissue
Reflection Transmission
Absorption
Scattering

 At low temperatures below 100°C, the
thermal effects denature proteins and
produce hemolysis
 They cause coagulation & shrinkage
 Above 400°C, carbonization of organic
materials occurs with onset of some inorganic
materials
 Between 400°C & 1200°C, inorganic
constituents melt, re-crystallize or vaporize

Tissue Feature
Hemoglobin Absorbed by Blue & Green WL
Melanin Absorbed by short
wavelengths
Hydroxyapatite Absorbed by a wide range of
WL
Dental structures have different amount of water content,
Enamel being the least followed by Dentin, Bone, Calculus,
Caries and Soft tissue
Dental lasers have a Photothermal effect

In general, shorter WL (500-1000
nm) are well absorbed in
pigmented tissues and blood
elements
Longer WL are more interactive
with water and Hydroxyapatite
Co2 (10,600 nm) is well absorbed
by water and has the highest
affinity for Hydroxyapatite

What does the Operator
control?
Level of
applied
power
(Power
Density)
Total energy
to be
delivered
(Energy
density)
Rate &
Duration of
exposure
(Pulse
Repetition)
Mode of
energy
delivery

Common Laser types Used in
Dentistry

Classifications:
 Lasers are named according to:
Active medium
Wavelength
Delivery systems
Emission modes
Tissue absorption
Clinical Application

Classifications:
I. Based on Active Medium
a) Solid State
b) Gas
c) Semiconductors
d) Excimer
e) Dye
II. Mode of action
a) Contact mode (focused or defocused) -
Ho:YAG ; Nd: YAG
b) Non-contact mode (focused or defocused)
- CO2

III. Based as application
a) Soft tissue laser - Argon, Co2, diode;
Nd:YAG.
b) Hard tissue laser - Er : YAG
c) Resin curing laser - Argon
IV. Based on Level of energy emission:
a) Soft lasers (Low level energy): He-Neon; Ga-Arsenide.
b) Hard lasers (High level energy): Er:YAG laser ; Nd: YAG laser.

Argon
 Active medium is Argon gas
 Fiber optically delivered
 Continuous wave & Gated Pulsed modes
 Only laser whose light is in the visible spectrum
 2 wavelengths are used:
 488 nm (Blue)
 514 nm (Blue-Green)

 488 nm emission is used to activate
camphoroquinone in composite resins
 The beam divergence of this blue light is used
in non-contact mode, produces excessive
amount of photons thus providing curing energy
 More strength in cured resin when compared to
conventional blue light
 Shorter curing time

 514 nm has its peak absorption in tissues
containing Hb, Hemosiderin and Melanin
 Has excellent hemostatic capabilities
 Small diameter flexible glass fiber is used for
delivery
 Used in contact mode
 Used in Surgical Endodontics
 Acute inflammatory Periodontal conditions and
highly vascularized lesions such as Hemangioma

 Neither wavelength is absorbed by dental tissues
or water
 Their poor absorption by enamel and dentin is an
advantage when used for incising and sculpting
gingival tissues
 Minimal interaction and no damage to tooth
surface
 Both can be used for caries detection
 Argon laser light illuminates the tooth, the disease
area appears dark orange-red colored

Diode
 Is a solid active medium laser
 Manufactured from semiconductor
crystals using combinations of Al, In,
Ga and Ar
 Available wavelengths are 800 nm (Al)
to 980 nm (In), placing them at the
beginning of the infra red spectrum
 Fiber optic delivered
 Continuous wave or Gated Pulse
modes
 Used in Contact mode

 Diode WL are highly absorbed by pigmented tissue and
deeply penetrating, though hemostasis is not as rapid
as with Argon laser
 Poorly absorbed by tooth tissues
 Soft tissue surgeries can be performed near tooth
 Causes a rapid increase in temperature thus, surgical
site needs to be air or water cooled
 Diode is an excellent soft tissue surgical laser
 Small size & Portable

 Diagnodent (Kavo) is a visible red
diode with a WL of 655 nm and 1
milliwatt power
 This red energy excites fluorescence
from carious tooth structure, which is
reflected back into a detector device
in the unit
 This analyses and quantifies the
degree of caries

Neodynium:YAG (Nd:YAG)
 Has a solid state active medium, which is a
garnet crystal combined with rare earth
elements Yytrium & Aluminum doped with
Neodynium
 Wavelength is 1064 nm
 Operate in free running pulsed mode with
short pulse durations
 Delivered via fiber optic cable
 Contact mode

 Laser light is highly absorbed by melanin
 Clinical applications include cutting and coagulating
soft tissues
 Energy is slightly absorbed by dental hard tissues but
there is little interaction between sound tooth
structure following soft tissue surgery
 Pigmented surface carious lesions can be vaporized
without removing the healthy surrounding enamel

Holmium:YAG
 Consists of a solid crystal of Yytrium, Aluminum Garnet
sensitized with Chromium and doped with Holmium and
Thulium ions
 Delivered via Fiber optic cable
 Free running pulsed mode
 Absorbed by water 1000 times more than Nd:YAG

 Using peak powers it can ablate hard
calcified tissues
 As a soft tissue laser instrument it does
not react with Hb or other tissue
pigments
 Used more in TMJ disorders and
Orthopedic cases

The Erbium Family
 2 distinct lasers
 Erbium Chromium: YSGG
 Erbium:YAG

Er Cr:YSGG
 Erbium Chromium:Yytrium Scandium Gallium
Garnet
 Wavelength – 2780 nm
 Delivered via fiber optics
 Fiber cable diameter is much larger and requires
an air or water coolant

Er:YAG
 Erbium: Yytrium, Aluminum Garnet
 Delivered via hollow tube and fiber optic
cable

 These 2 WL’s have the highest absorption in
water and have high affinity for
hydroxyapatite
 The laser couples into hydroxyl radical in the
apatite crystal and into water that is bound to
the crystalline structures of tooth
 Caries removal and tooth preparation can be
easily carried out
 The increased water content in carious lesions
allows the laser to preferentially interact with
diseased tissue

 This is the most efficient laser for
drilling and cutting enamel as its
energy is well absorbed by
hydroxyapatite

CO2
 Gas active medium laser
 Co2 pumped via electrical discharge current
and is present in a sealed tube
 Wavelength is 10,600 nm
 Delivered via hollow tube or wave guide
 Continuous or Gated pulsed mode

 Well absorbed by all biological hard & soft tissues
 Can easily cut and coagulate soft tissue
 Has a shallow depth of penetration into tissue
 The laser energy is delivered by a hollow wave guide in a
non contact fashion
 This WL has the highest absorption in hydroxyapatite of any
dental laser
 Thus tooth must be protected during soft tissue application

 Its high thermal absorption makes
the CO2 laser less suitable for
cutting and drilling enamel &
dentin as the damage to the
dental pulp may occur

Lasers in Endodontics
Dentinal Hypersensitivity
Pulp Diagnosis
Pulp Capping & Pulpotomy
Cleaning & Shaping of root canal systems
Sterilization
Endodontic Surgery

Dental Hypersensitivity
 Characterized as short, sharp pain from
exposed dentin that occurs in response to
provoking stimuli such as cold, heat or
chemicals
 Not ascribed to any other dental defect or
pathology
 Can be attributed to non carious tooth loss
(Wasting diseases)

 Various treatment modalities
 Blocking the dentinal fluid flow
 Application of various agents to exposed
dentinal tubule
 Oxalate salts
 Isobutyl cyanoacrylate
 Fluoride releasing resins
 Reduce Neuronal Responsiveness
 5% Potassium Nitrate & 10% Strontium Nitrate

Laser as a treatment modality
 Rationale for laser induced reduction in DH is
based on 2 possible mechanisms
 1st mechanism – implies direct effect of laser
irradiation on the electric activity of nerve fibers
within the dental pulp
 2nd mechanism – modification of the tubular
structure of dentin by melting and fusing of the
hard tissue or smear layer and subsequent
sealing of dentinal tubules

Lasers for treatment of DH are divided into 2
groups:
Low Output Power Lasers Middle Output Power Lasers
Helium – Neon Diode Nd:YAG
Gallium-Aluminum-Arsenide diode Co2

Pulp Diagnosis
 Laser Doppler flowmetry (LDF) was developed to
assess blood flow in microvascular systems, e.g.
in the retina, gut mesentery, renal cortex and
skin
(Morikawa et al. 1971, Riva et al. 1972)

 Helium – Neon and Diode laser at a low
power of 1 or 2 mW
 Wavelength is 632.8 nm
 Laser beam is directed towards the tooth
(to the blood vessels)
 Moving RBC causes the frequency of the
laser beam to be Doppler shifted and some
of the light be back scattered out of the
tooth

 The reflected light is detected by the
photocell on the tooth surface and its
output proportional to the number and
velocity of the blood cells
 Advantages :
 Can be used in traumatized teeth
 Does not rely on painful sensation to
determine vitality

Pulp Capping & Pulpotomy
 Pulp capping is a procedure in which a
dental material such as Calcium hydroxide
or MTA is placed over a pulpal wound to
encourage the formation of reparative
dentin
 Pulpotomy is defined as the surgical
removal of the coronal portion of the pulp
by means of preserving the remaining
radicular tissues

 Melcer et al used Co2 lasers & demonstrated
new mineralized dentin formation without
cellular modifications in pulpal tissues
 Shoji et al used Co2 lasers in different WL and
reported that no damage was detected in the
radicular pulp. Charring, coagulation necrosis
and degeneration of odontoblastic layer
occurred, with no pulp damage
 Jukic et al used Co2 and Nd:YAG lasers on
exposed pulp tissue and reported that a
dentinal bridge was formed

 Co2 and Nd:YAG lasers are well
absorbed by the hydroxyapatite of
enamel and dentin, causing tissue
ablation, melting and re-solidification
 These lasers do not cause any thermal
damage to the pulp tissue and do not
increase the intra-pulpal temperature
– if used at the correct power,
duration of time and intensity

Cleaning & Shaping of Root Canal
System
 Various laser systems can deliver the energy
into the root canal using a thin optical fiber
 Various systems that have been used are
 Nd:YAG
 Er,Cr:YSGG
 Argon
 Diode
 Er:YAG

 It has been demonstrated in many studies
that the laser radiation has the ability to
remove debris and smear layer from the
root canals
 It also has the potential to kill the
microorganisms
 Bergman et al suggested that lasers is not
an alternative to the conventional
cleaning & shaping, but can be used as an
adjunct

Limitations for use in Root
Canals
 Emission of laser energy from the tip of optical
fiber or the laser when directed into the root
canal is not uniform
 There may be thermal damage to the periapical
tissues
 May be hazardous when the tooth apex is near
vital structures such as mandibular nerve or
mental foramen

Laser assisted Obturation
 Aim of Obturation:
 Eliminate all avenues of leakage
 Seal the RC system from all ends
 Rationale in using lasers for obturation is that
the irradiation can be used as a heat source for
softening the GP
 Conditioning of the dentin walls can also be done

Lasers in Endodontic Surgery
 Weichman & Johnson attempted to
seal the apical foramen of freshly
extracted teeth in which the pulp had
been removed
 Laser is used for the surgery, a
bloodless surgical field should be
easier to achieve due to the ability of
the laser to vaporize tissue and
coagulate and seal small blood vessels

 The use of this laser seals the dentinal
tubules in the apical portion of the root and
sterilizes the surgical site
 On, extracted teeth (Stabholz et al. 1992
Arens et al. 1993, Wong et al. 1994), used
the Nd:YAG laser and found that there was a
reduction in the penetration of dye or
bacteria within resected roots
 When the laser was used for resection itself,
either in extracted human teeth in vitro
(Maillet et al. 1996), found that tissue
repairs was quicker when compared with
those roots resected with a bur

Advantages
 Good hemostasis
 Improved visualization of surgical site
 Sterilization operative field
 Reduced permeability of root surface
dentin
 Reduction in post operative pain
 Reduced risk of contamination of surgical
site by eliminating use of air turbines

Constraints
Time Consuming
Increase temperature
Cause irreversible pulpal
damage
Needs precise execution
Increased cost of treatment

Lasers in Operative &
Aesthetic Dentistry
 Lasers have become a part of routine
operative and aesthetic practice
 There are five lasers that are currently in
the armamentarium

Argon lasers
 The wavelength is absorbed by Hb
 This attribute allows precision cutting,
hemostasis & coagulation of vascular tissue
 Use of argon lasers have been used for curing
composites (at low power achieving higher
bond strength)
 Transillumination in diagnosis of tooth
fractuures

Plasma Arc Curing (PAC)
 PAC & Argon laser curing systems have
rapid polymerization of composites
 However they increase heat generation
and polymerization shrinkage stresses
 Studies have shown that they exhibit a
narrow spectral output and do not
coincide with the spectral requirements
of all restorative resins
 Bleaching of stained teeth

Co2 Lasers
Used for vaporizing, cutting and
coagulation of soft tissue
Used more for soft tissue
procedures which include gingival
re-modelling and shaping in
aesthetic dentistry (Perio-
Aesthetics)

Diode Lasers
 2 different WL are used
 Ga-Al-As Laser (800 nm) & In-Ga-
As (980 nm)
 These are used in contact mode
for cavity preparation, removal of
bacterial contamination and
coagulation of tissue
 Also used for Diagnosis

Erbium Family
 Er lasers are absorbed by Hydroxyapatite and
water
 Allows to cut soft tissue, tooth structure and
bone
 Er:YAG (2940 nm) cuts teeth easily & quickly
 Also used for removal of caries (excavation)

Decay present on the facial of the
maxillary left lateral incisor
The Erbium laser used to remove the
decay. No anesthesia was required
After caries removal and preparation is
complete
Definitive direct bonded restoration
after preparation with the Erbium laser

Etching
 Laser etching has been evaluated as an
alternative to acid etching of enamel and
dentine. The Er:YAG laser produces micro-
explosions during hard tissue ablation that
result in microscopic and macroscopic
irregularities
 These micro irregularities make the
enamel surface micro retentive and may
offer a mechanism of adhesion without
acid-etching

 However, it has been shown that adhesion to
dental hard tissues after Er: YAG laser etching
is inferior to that obtained after conventional
acid etching (Martinez-Insua et al., 2000)
 The weaker bond strength of the composite
to laser-etched enamel and dentine to the
presence of subsurface fissuring after laser
radiation. This fissuring is not seen in
conventional etched surfaces
 The subsurface fissuring contributed to the
high prevalence of cohesive tooth fractures in
bonding of both laser-etched enamel and
dentine

Caries prevention
 Studies examined the possibility of using
laser to prevent caries (Hossain et al.,
2000; Apel et al., 2003)
 It is believed that laser irradiation of
dental hard tissues modifies the calcium
to phosphate ratio, reduces the
carbonate to phosphorous ratio, 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 (Watanabe et al., 2001;
Arimoto et al., 2001)
 The degree of protection against
caries progression provided by the
one-time initial laser treatment was
reported to be comparable to daily
fluoride treatment by a fluoride
dentifrice (Featherstone, 2000)

Laser Assisted Bleaching
 Two laser-assisted whitening systems have
been cleared by the FDA
 The laser is used to enhance the activation of
bleaching material, which then whitens the
teeth
 The argon laser wavelength of 488 nm for 30
seconds to accelerate the activity of the
bleaching gel
 After the laser energy is applied, the gel is
left in place for three minutes, then
removed. This procedure is repeated four to
six times

 Laser-assisted tooth bleaching, however, still
poses a number of unanswered questions
 Because of continuing concerns and
unknowns about laser interactions with hard
tissue and the lack of controlled clinical
studies, CO2 laser-assisted bleaching is not
recommended (FDA)
 Based on previously accepted uses of argon
lasers and associated temperature-rise
studies, the use of the argon laser in place of
a conventional curing light may be
acceptable if the manufacturer’s suggested
procedures are carefully followed (FDA)

Laser Applications
 Frenectomy
• Gingival
troughing

Laser Applications
 Gingival Recontouring
• Gingivoplasty

Laser Applications
 Gingivectomy
• Biopsy

Dental Laser Safety
 Safety is an integral part of
providing dental treatment with
lasers
 3 aspects to safety:
Manufacturing process
Proper operation of the device
Personal protection

Regulatory Agencies
 American National Standard Institute
(ANSI)
 Food and Drug Administration (FDA)
 Center for devices and Radiological Health
(CDRH)
 Occupational safety health administration
(OSHA)

Safety Laser Classification
Class Laser Properties
I Pose no health hazard e.g. CD Player
II Emit only visible light with low power output & do not pose any
health hazards
Maximum allowable output is 1 mW
IIIa Emit any WL and have an output power of 0.5 W of visible
light; In this laser light can be viewed only momentarily
Caution label is present
IIIb Hazardous to unprotected eye; Output power no greater than
0.5 W; eg. Argon Laser curing light; Eye protection is must
IV Hazardous from direct viewing and may produce diffuse
reflections; Output power more than 0.5 W; Can produce fire
and severe skin reactions; Can ignite inflammable devices

Fire & Explosion Hazards
 Use only wet and fire retardant
materials in operative field
 Use non combustible anesthetics
 Avoid alcohol based topical
anesthetics
 Avoid alcohol moistened gauze or
cotton
 Fire Extinguisher
 Stay informed
 Follow ANSI regulations

Laser Safty:
Safety Precautions.
Ocular Hazard.
Skin Hazard.

Guidelines
 Mention outside
 Door Switch
 Fire hazards

Eye Protection
 In 1962, the awareness to eye
protection began
 Eye is a critical target for laser
injury
 Class III & IV lasers pose a threat
to the eye
 Proper eye wear is a must

Why the Eye ???
 Cornea is made up of 90% Water
 Absorbs emissions from all lasers
 Cause Corneal Burns
 Holium and Erbium lasers affect the
Aqueous and Vitreous Humor as well as
the lens which lead to Aqueous Flare &
Cataract formation
 Retinal damage occurs due to lasers with
more depth of penetration and is absorbed
into the pigments (Argon, Diode, He:Ne)

 The eye is 100,000 times more
vulnerable to injury than the skin
 WL from 400-1400
 Protective glasses must have an
Optical Density of at least 4
 For specific high WL lasers like Nd:YAG
& Diodes, there are specific eye wear
 Eyewear is designed to have adequate
protection for a wide range of WL’s
 Regardless of protection, NEVER look
directly into the laser beam

Sterilization & Infection
Control
 Fiber optic cables & handpieces can be
autoclaved in pouches
 Oil based aerosols must not be used
 The wires and protective casing / housing
should be wiped clean and not autoclaved

The advantages of laser in dentistry:
• Compared to the traditional dental
drill, lasers:
 May cause less pain in some instances,
therefore, reducing the need for
anesthesia
 May reduce anxiety in patients
uncomfortable with the use of the dental
drill
 Minimize bleeding and swelling during

The disadvantages of lasers in dentistry:
 Lasers can't be used on teeth with fillings already in
place.
 Lasers can't be used in many commonly performed
dental procedures. For example, lasers can't be
used to fill cavities located between teeth, around
old fillings, and large cavities that need to be
prepared for a crown.
 In addition, lasers cannot be used to remove
defective crowns or silver fillings, or prepare teeth
for bridges.
 Traditional drills may still be needed to shape the
filling, adjust the bite, and polish the filling even
when a laser is used.

There are thousands of research studies and medical
publications,saying that LASER is a very effective
modality of treatment that is being widely used all
over the world with promising and successful
results, also in Orthopedic surgery which is very
targety oriented, convenient and cost effective.
LASER has been widely used in medical science with
proved & promising success for treatment of a
variety of medical conditions including carpal
tunnel syndrome, cervical neck pain, low back
pain, joint pain, frozen shoulder, generalized
muscle pain. and acceleration of wound healing.
Besides orthopedic application,
NASA are currently using Laser for medical
conditions in space applications.
All of these events validate the growing
acceptance in mainstream medicine for the
medical efficacy of laser therapy as a viable,
often superior therapeutic treatment modality.

Worldwide laser sales by application
( Ref: Journal of Laser Application, Feb 2005

General Laser F A Q
Q: Is the radiation from lasers harmful?
A: The radiation from lasers is light, a form of
electro magnetic radiation, which is non-ionizing
radiation and is around us all the time. It can be
dangerous under certain circumstances such as
when a laser beam is projected into the eye,
onto the skin or onto flammable materials (see
Basic Laser Safety). Ionizing radiation such as
that from X-rays, and nuclear materials is
dangerous as it can cause cell damage and
cancer. If treated with caution and respect, a
laser is not dangerous.

Q: Who invented the laser?
A: The actual inventor of the laser is lost
in a storm of controversy, claims and
counter claims. Most historians will
agree that the first recorded operation
of a laser was on 7th July 1960 by Dr.
Theodore Maiman at the Hughes
Research Labs in Malibu California. Dr.
Maiman’s laser was based on the
theoretical ideas of Albert Einstein, Dr.
Charles Townes and Arthur Shawlow.

Q: What is the star/sun shaped symbol I see all
over the web site?
A: The symbol is a stylized or simplified version
of the international “sunburst” symbol which
stands for lasers. The standard international
symbol is shown on the left in the International
"Lasers In Use" warning sign which should be
posted in areas where unshielded lasers are in
use. You may even find a similar sign or logo
inside your CD player or CD-ROM drive as they use
low power laser diodes to read the data from the
disk.

Q: How can lasers hurt me?
A: If a high power laser beam strikes you in
the eye it can cause a burn on your
retina. Just as you can use a magnifying
glass to focus the sun and burn with the
light, the lens in the human eye focuses
the laser beam down to a very small point
on the retina which can cause a burn. The
focusing effect can concentrate a laser
beam up to 100,000 times thus a one watt
beam entering the eye can be focused to a
point with 100,000 watts of power, more
than enough to cause a severe retinal burn
and loss of vision

Q: Are lasers powerful enough to use as
weapons like we see in the Star Wars
movies and on Star Trek?
A: Fortunately present day laser systems
are unsuitable for use as weapons as the
power needed to cut through space ships
or do serious damage to metal objects is
extremely high. Presently lasers that are
powerful enough to machine metal are
large and heavy and require lots of power
and cooling water to operate thus are not
useful as portable “death rays”.

Q: How is laser power measured?
A: Laser power is measured in watts
- the same watts used to measure
the power of light bulbs. A 10 watt
laser will appear much brighter than
a 10 watt light bulb since the light
from the bulb travels in all
directions and spreads rapidly, while
the light from the laser is
concentrated in a beam only a few
millimeters in diameter.

Q: Can I build my own laser?
A: To build your own laser, you would have to have access
to a precision machine shop to build the frame, have
glassblowing skills to make the tube, vacuum equipment to
pump down the tube and access to rare gasses to fill the
tube; you would also need considerable electronics skills to
build the exciter (power supply). It would be like trying to
build your own light bulb or fluorescent tube. It is simpler
to purchase a laser as low cost HeNe and diode lasers are
readily available.
Q: I still want to try building a laser... is there any
place I can get plans?
A: You can visit the Laser Hobbyists topic in our Backstage
Area which has a Laser Construction page with some
information that may be helpful. Be leery of those who
offer low cost plans for building a laser on the net as these
plans are often useless.

Q: Do all Lasers need to have a cooling system?
A: Small lasers such as HeNe and diode lasers
usually do not need any special cooling systems
as they cool by convection of the air around
them, or by conduction of the heat into the
mounting or casing. As the output power of the
laser increases, the amount of heat produced
increases and cooling systems have to be used.
CW lasers up to about one watt can be air-
cooled, over 1 watt most lasers require water
cooling as air can not remove the heat fast
enough, although there are Copper Vapor and
YAG lasers that produce several watts of optical
power and are air-cooled.

References
 Pathways of Pulp (9th Ed.) – S.Cohen
 Art & Science of Operative Dentistry –
Sturdevant
 Textbook of Endodontics (6th Ed.)– Ingle
 DCNA – 2000, 2005
 Journal of Endodontics
 International Endodontic Journal
 Journal of American Dental Association
 British Dental Journal

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