Q: What is laser
A: Laser therapy or Laser Phototherapy
is a method where light from a laser is applied to tissue
(or cells in culture) in order to influence cell or tissue
functions with such low light intensity that heating is negligable.
The effects achieved are hence not due to heating but to photochemical
or photobiologic reactions like the effect of light in plants.
The lasers used are normally called therapeutic lasers or
This is in contrast to the use of lasers in
surgery and for esthetic purpose where strong lasers are used
and where the biologic effects (cutting, evaporating, coagulating)
are based on heat development from the absorption of strong
light, i.e. burning glass effect.
Q: What is the correct name: LLLT, LPLT,
therapeutic laser, soft laser, MID laser or biostimulation?
A: Regarding the therapy, we have chosen to use
the term LLLT (Low Level Laser Therapy). This is the dominant
term in use today, but there is still a lack of consensus.
In the literature LPLT (Low Power Laser Therapy) is
also frequently used.
Regarding the laser instrument, we have chosen to use
the term "therapeutic laser" rather than
"low level laser" or "low power laser",
since high-level lasers are also used for laser therapy.
The term "soft laser" was originally used
to differentiate therapeutic lasers from "hard lasers",
i.e. surgical lasers. Several different designations then
emerged, such as "MID laser" and "medical
"Biostimulating laser" is another term, with
the disadvantage that one can also give inhibiting doses.
The term "bioregulating laser" has thus been
proposed. An unsuitable name is "low-energy laser".
The energy transferred to tissue is the product of laser output
power and treatment time, which is why a "low-energy
laser", over a long period of time, can actually emit
a large amount of energy. Other suggested names are "low-reactive-level
laser", "low-intensity-level laser",
"photobiostimulation laser" and "photobiomodulation
laser". "LPT - Laser Photo Therapy"
is a recently suggested term, and winning
Thus, it is obvious that the question
of nomenclature is far from solved.
This is because there is a lack of full agreement internationally,
and the names proposed thus far have been rather unwieldy.
Feel free to forget them, but remember LLLT until agreement
is reached on something else.
Is laser therapy scientifically well
A: Basicly yes. There are more than 130 double-blind
positive studies confirming the clinical effect of LLLT. More
than 3000 research reports are published. Looking at
the limited LLLT dental literature alone (370 studies
already in 1999), more than 90% of these studies do verify
the clinical value of laser therapy. About 250 papers
are annually published in peer reviewed scientific papers.
do I find such documentation?
A: The book "Laser
Therapy Handbook" is the best reference
guide for literature documentation. Abstracts from
scientific papers can be found on PubMed, http://www.pubmed.com
I have heard that there are dozens of studies failing
to find any effect of LLLT?
is true. But you cannot just take a any laser and irradiate
for any length of time and using any technique. A closer
look at the majority of the negative studies will reveal
serious flaws. Look for link under Laser literature and
read some examples. But LLLT will naturally not work on
anything. Competent research certainly has failed to demonstrate
effect in several indications. However, as with any treatment,
it is a matter of dosage, diagnosis, treatment technique
and individual reaction. Se
link critic on critic.
lasers can be used in medicine?
A: Examples of lasers which can be used in medicine,
both for surgery and therapy:
Therapeutic lasers (where the mechanism
is not based oh heat):
||904 nm (super
||Treatment of deep problems (back, shoulders,
knees, head ache etc)
nm (cont. or chopped)
||Also deep problem, often a complement
ot the GaAs-laser
||Treatment of skin and mucose problems
||Alternative to InGaAlP
Thermal lasers (for surgery or esthetic use):
||Hair removal (for Q-switch type: tattoo
||Coagulation of tumors, eye surgery (cataracts)
||Crushing of kidney stones, surgery
||Dental drill, laser peeling of wrinkles
||Coagulation of blood vessels, hemangioma.
||Hair removal (for Q-switch type: tattoo
||Surgery and laser peeling of wrinkles
||Eye surgery (treatment of retinopathy)
There are many other types, but those mentioned above are
the most common.
therapeutic lasers injure your eyes?
A: Yes and no! Read the following:
Any strong light source - laser or not - can injure an
eye.There are strong lasers that can cut in plastic and
even steel. They can injure eyes and tissue, but laser pointers
and therapeutic laser can normally not. Read more below:
The following factors are of importance regarding the eye
risk of different lasers:
The output power (strength) of the
laser. It is fairly obvious that a powerful
laser (many watts) is more hazardous to stare into than
a weak laser.
The divergence of the light beam.
A parallel light beam with a small diameter is by far the
most dangerous type of beam. It can enter the pupil, in
its entirety, and be focused by the eye's lens to a spot
with a diameter of hundredths of a millimetre. The entire
light output is concentrated on this small area. With a
10 mW beam, the power density can be up to 12,000 W/cm2
The exposure time. To
burn the retina, a certain energy is needed. Energy is power
multiplied by time, so exposure time is important.
The wavelength of the light. Within
the visible wavelength range, we respond to strong light
with a quick blinking reflex. This reduces the exposure
time and thereby the light energy which enters the eye.
Light sources which emit invisible radiation, whether
an infrared laser or an infrared diode, always entail a
higher risk than the equivalent source of visible
light. Radiation at wavelengths over 1400 nm is absorbed
by the eye's lens and is thus rendered safe, provided the
power of the beam is not too high. Radiation at wavelengths
over 3,000 nm is absorbed by the cornea and is less dangerous.
The distribution of the light source. In
an eye, like in a camera, the image of the source is projected
on the retina/film. In a laser, the source is very small,
so it is depicted as a point (compare with a burning glass
where you get a picture of the sun in the focus "point").
A widely spread light source is projected onto the retina
in a correspondingly wider image, in which the light is
spread over a larger area, i.e. with a lower power density
as a consequence. For example: a clear light bulb is apprehended
as a more concentrated light source than a so-called "pearl"
light bulb. A laser system with several light sources placed
separated from each other (often called multi probe) constitutes
a smaller hazard to the eye than if the entire power output
was from one laser source, because the light sources separate
placement means that they are reproduced in different places
on the retina.
In conclusion. Lasers in general are much
less dangerous than people think. No person has become blind
by a laser. A few people have got injuries. Normally they
will not notice such an injury. Even in the worst cases
(where the inury is extensive and in the midle of the fovea)
the consequensies are much less than any injury caused by
stones, knifes, dart arrows, fireworks, dry branches int
the forrest etc. See further the presentation named: What
lasers can make you blind?
do I know which laser I should buy?
A: The laser market is very complicated and full
of pitfalls. How do you know which instruments are good?
What is expensive? Will it be expensive in the long run
to buy something cheap? It is easy to make hasty decisions
when faced with a skilful salesman - who is likely to know
much more about the field than the customer. Before you
know it, you've signed on the dotted line. All lasers are
given a laser class. This classification is only to indicate
the possible eye risk and has nothing to do with the possible
efficktiveness in treatment. There are four laser classes
where class 4 is the strongest and class 1, 2 and 3A and
3B are less hazardous to eyes. Lasers in CD players and
for reading bar codes are usually class 1 lasers while surgicla
and industial lasers usually are class 4 lasers.
Here are a number of questions which you
should ask both the salesman and yourself. You would be
well advised to read these carefully in case you regret
not doing so later on!
1 "Laser instruments"
have been sold which do not even contain a laser, but LEDs
or even ordinary light bulbs. These instruments have been
sold for between US $3,000 - $10,000. How can you acquire
proof that the instrument really does contain a laser?
2 In a number of products, laser
diodes have been combined with LEDs. This is often kept
secret and the salesman has only talked about a laser. Are
all light sources in the apparatus (except guide lights
and warning lights) really lasers?
3 Is a strong laser better than a
week? No, not necessarily. There is an optimal dose for
what ever treatment - let's say that you want to administer
10 joules to a certain area. If the laser output is 1 watt,
it takes 10 seconds to give 10 joules. With a 100 mW laser
it takes 100 seconds to produce 10 joules. Further, it has
become clear that also treatment time should not be too
short or too long. As high power has become a more and more
common sales argument, it can be difficult to achieve both
optimal dose and optimal treatment time. Naturally, also
a too weak laser can make the treatment less successful.
4 For oral work and wound healing,
InGaAlP and GaAlAs are the most common types, with GaAlAs
as the most versatile one. For injuries to joints, vertebrae,
the back, and muscles, that is, for the treatment of more
deep-lying problems, the GaAs laser is the best documented.
For veterinary work, a laser is needed which is designed
so that the laser light can pass through the coat, and penetrate
to the desired depth. For superficial tendon and muscle
attachments, the required depth can be reached with the
GaAlAs laser. Many companies have only one type of laser,
such as a GaAlAs, and the salesman will naturally tell you
that it is the best model for everything, and that it is
irrelevant which type of laser is used. However, research
tells quite a different story. GaAs further requires lower
dosage than GaAlAs, so nominal power is not everything.
5 Size, colour, shape, appearance
and price vary a great deal from manufacturer to manufacturer.
Because a piece of equipment is large, it does not necessarily
follow that its medical efficacy is high, or vice versa.
The most important factor is the energy (dose) which enters
the tissue. Make sure the laser you buy is designed so that
all the light actually enters the tissue. Ask the salesman:
how is the dose measured? What dose is too high, and what
is too low?
6 Many companies which import lasers
have deficient knowledge in terms of medicine, laser physics,
and technology. In fact, there are many examples of companies
which have gone bankrupt. If a piece of equipment is faulty,
it may have to be sent to the country of manufacture for
repair. How long would you be without your equipment in
such a case, and what would it cost to repair? Can the importer
document his expertise? Who can you speak to who has used
the apparatus in question for a long period of time? Is
there a well-known professional who uses this make? What
does it cost to change a laser diode or laser tube, for
example, after the guarantee has expired? Can you get written
confirmation of this? Try to get a list of references who
you can call and ask.
7 The difference between a colourful
brochure and reality is often considerable. There are examples
of brochures which describe output ten times that which
the equipment actually provides. How can you find out the
real performance of the equipment (e.g. its output)? Are
there measurement results from an independent authority?
Is it possible to borrow an apparatus in order to measure
its performance? Is there a power meter on the apparatus
which can measure what is emitted and show it in figures?
It is not enough simply to have a light indicator.
8 Some dealers know that their products
are sub-standard. This can often be seen by the fact that
they are anxious to get the customer to sign a contract.
If a product is good, the dealer will have no doubts about
selling it on sale-or-return basis, with written confirmation
of this. What happens if the medical effects are not as
promised? Is it possible to get a written guarantee of sale-or-return?
9 In most countries, therapy lasers
must be approved (e.g. CE or FDA approval). The approval
certificate shows the laser type and the class to which
the instrument belongs, e.g. laser class 3B. There is also
a certificate number. A laser which is not approved may
either not be a laser, or might be sold illegally.
10 Many companies organize courses
and "training" events of markedly varying quality.
A serious importer or manufacturer takes pains to ensure
that his equipment is used in a qualified way, and makes
sure that the customer receives some training in its use.
What are the instructor's background and qualifications?
Has he or she published anything? Is there a course description?
What does the training material cost? Is a training course
included in the cost of the equipment? Is the training material
included? Is it possible to buy the training material only?
11 Development is going
on at a fast pace. Suddenly, you have out-of-date laser
equipment and a new and perhaps more efficient type of laser
comes onto the market. What happens if your laser becomes
outmoded? Do you have to buy a new laser, or can your equipment
be updated with future components lasers?
12 Is it possible to get education
or a qualified treatment manual? Is literature included
in the price?
How come some LLLT equipment
has power in watts and some only in milliWatts?
A: A typical example is GaAs lasers. As a GaAs laser
always works in a pulsed fashion, the laser light power
varies between the peak pulse output power and zero. Then
usually the laser's average power output is of importance,
especially in terms of dose calculation. The peak pulse
power value is of some relevance for the maximum penetration
depth of the light. Some manufacturers specify only the
peak pulse output in their technical specifications. "70
W peak pulse output" or even "70 000 mW power
output" naturally sounds more impressive than 35 milliwatts
|Q: Which frequency
(pulsing) should be used for the various
A: First we must differentiate between “chopping”
and “superpulsing”. Some lasers, like the GaAs
laser, are always pulsed. The pulses are very short but the
peak power of the pulse is very high, several watts, but the
pulse duration is typically only 100 to 200 nano seconds.
Other lasers like the HeNe and the GaAlAs are normally continuous,
but can be pulsed by mechanical or electrical devices. This
means that the beam is turned off and on but the peak output
power of each pulse is the same as if the light is continuous.
If a continuous laser is pulsed, the average output power
will be lower. With most GaAs lasers the power decreases with
lowered frequencies (unless there is a pulse train arrangement)
and with “chopped” lasers we typically loose 50%
(50% duty cycle).
There is some evidence from cell studies that the pulsing
can makes a difference. But the evidence from clinical studies
is almost absent. Since GaAs is always pulsed, we have to
choose a frequency and then to use the anecdotal evidence
there is about what frequency is good for what.
Which type of laser is
best suited to which job?
A: There are three
main types of laser on the market: HeNe (now being gradually
replaced by the InGaAlP laser), GaAs and GaAlAs. They can
be installed in separate instruments or combined in the
* The InGaAlP- or HeNe-laser
has been used a great deal in dentistry in particular, as
it was the first laser available. They are especially good
for and have been used for wound healing for more than 40
years. One advantage is the documented beneficial effect
on mucous membrane and skin (the types of problem it is
best suited to), and the absence of risk of injury to the
eyes. A Japanese researcher has even treated calves with
keratoconjunctivitis with excellent results, that is, irradiation
of the eye through the eye lid. Because HeNe light is visible,
the eye's blink reflex protects it.
Normal HeNe output for dental
use is 3-10 mW, although apparatus with up to 60 mW is available.
An optimal dosage when using a HeNe laser for wound healing
is 1-4 J/cm2 around the edge of the wound, and approximately
0.5 J/cm2 in the open wound. HeNe lasers are used to treat
skin wounds, wounds to mucous membrane, herpes simplex,
herpes zoster (shingles), gingivitis, pains in skin and
mucous membrane, conjunctivitis, etc.
* The GaAs laser is excellent
for the treatment of pain and inflammations (even deep-lying
ones), and is less suited to the treatment of wounds and
mucous membrane. Very low dosages should be administered
to mucous membrane! Most GaAs equipment is intended for
extraoral use, but there are special lasers adapted for
The GaAs laser is, like
GaAlAs and InGaAlP lasers, a semiconductor laser. A purely
practical advantage of this type of laser is that the laser
diode is located in the hand-held probe. This means that
there is no sensitive fibre-optic light conductor which
runs from the laser apparatus to the probe, but just a normal,
cheap, robust electric cable. Optimum treatment dosages
with GaAs lasers are lower than with HeNe lasers.
The GaAs laser is most effective
in the treatment of pain, inflammations and functional disorders
in muscles, tendons and joints (e.g. epicondylitis, tendonitis
and myofacial pain, gonarthrosis, etc.), and for deep-lying
disorders in general. As mentioned above, GaAs is not thought
to be as effective on wounds and other superficial problems
as the HeNe laser (InGaAlP laser) and GaAlAs laser. GaAs
can, nevertheless, be used successfully on wounds in combination
with HeNe or InGaAlP, but the dosages should be very low
- under 0.5 J/cm2.
* The GaAlAs laser can have
a wavelength in the interval 750 to 980 nm and has become
increasingly popular. Most common wavelength is 808 nm.
As they are very easy to run electrically, small rechargeable
lasers have been put on the market, often not much larger
than an electrical toothbrush. (They can run on normal or
rechargeable batteries.). GaAlAs
lasers have appeared on the market with an output of over
200-300 mW laser diodes
are now relatively cheap and the GaAlAs laser gives "a
lot of milliwatts for the money". Recently, GaAlAs
lasers have appeared on the market with an impressive output
of over 500 mW. In Europe, GaAlAs laser with powers above
500 mW can only be used by doctors and dentists, being Class
Many InGaAlP/GaAlAs lasers
have well-designed, exchangeable, sterilizable intraoral
fiber tips (light guides). For the infrared types especially,
output power meters are essential because the light is invisible.
carbon dioxide lasers be used for LLLT?
A: Yes. Therapeutic laser treatment
with carbon dioxide lasers has become more and more popular.
This does not require instruments expressly designed for
that purpose. Practically any carbon dioxide laser can be
used as long as the beam can be spread out over an appropriate
area, and as long as the power can be regulated to avoid
burning. This can always be achieved with an additional
lens of germanium or zinc selenide, if it cannot be done
with the standard accessories accompanying the apparatus.
It is interesting to note that the CO2
wavelength cannot penetrate tissue but for a fraction of
a mm (unless focused to burn). Still, it does have biostimulative
properties. So the effect most likely depends on transmittor
substances from superficial blood vessels. Conventional
LLLT wavelengths combine this effect with "direct hits"
in the deeper lying affected tissue.
deep into the tissue can a laser penetrate?
A: The depth of penetration of laser light depends
on the light's wavelength, on whether the laser is super-pulsed,
and on the power output, but also on the technical design
of the apparatus and the treatment technique used. A laser
designed for the treatment of humans is rarely suitable
for treating animals with fur. There are, in fact, lasers
specially made for this purpose. The special design feature
here is that the laser diode(s) obtrude from the treatment
probe rather like the teeth on a comb. By delving between
the animal's hair, the laser diode's glass surface comes
in contact with the skin and all the light from the laser
is "forced" into the tissue.
A factor of importance here is the compressive
removal of blood in the target tissue. When you press lightly
with a laser probe against skin, the blood flows to the
sides, so that the tissue right in front of the probe (and
some distance into the tissue) is fairly empty of blood.
As the haemoglobin in the blood is responsible for most
of the absorption, this mechanical removal of blood greatly
increases the depth of penetration of the laser light.
It is of no importance whether the light
from a laser probe, held in contact with skin is a parallel
beam or not.
There is no exact limit with respect to
the penetration of the light. The light gets weaker and
weaker the further from the surface it penetrates. There
is, however, a limit at which the light intensity is so
low that no biological effect of the light can be registered.
This limit, where the effect ceases, is called the greatest
active depth. In addition to the factors mentioned above,
this depth is also contingent on tissue type, pigmentation,
and dirt on the skin. It is worth noting that laser light
also penetrate bone (as well as it can penetrate muscle
tissue). Fat tissue is more transparent than muscle tissue.
For example: a InGaAlP laser with a power
output of 35 mW has a greatest active depth of about 10
mm depending on the type of tissue involved. A GaAlAs probe
of some strength has a penetration of 35 mm and a GaAs laser
has a greatest active depth of between 30 and 40 mm (sometimes
down to 50 mm), depending on its peak pulse output (around
a thousand times greater than its average power output).
If you are working in direct contact with the skin, and
press the probe against the skin, then the greatest active
depth will be achieved.N.B. Clothes will reduce
penetration between 80 and 100% depending on thickness and
LLLT cause cancer?
A: The answer is no. No mutational effects have
been observed resulting from light with wavelengths in the
red or infra-red range and of doses used within LLLT.
But what happens if I treat someone who has cancer and
is unaware of it? Can the cancer's growth be stimulated?
The effects of LLLT on cancer cells in vitro have been studied,
and it was observed that they can be stimulated by laser
light. However, with respect to a cancer in vivo, the situation
is rather different. Experiments on rats have shown that
small tumours treated with LLLT can recede and completely
disappear, although laser treatment had no effect on tumours
over a certain size. It is probably the local immune system
which is stimulated more than the tumour.
The situation is the same for bacteria and virus in culture.
These are stimulated by laser light in certain doses, while
a bacterial or viral infection is cured much quicker after
the treatment with LLLT
happens if I use a too high dose?
A: You may have a biosuppressive effect or just
a non optimal effect. That means that, for instance, the
healing of a wound will take longer time than normally.
Very high doses on healthy tissues will not damage them.
there any contraindications?
A: No, no medical contraindications. In most countries
there are legal contraindications, i.e. you should not treat
cancer or some other seious deseases. Pregnancy is not a
contra indication if treatment is done with common sense.
Pacemakers are electronical and are not influenced by light.
The most valid contraindication is possible lack of adequate
LLLT cause a heating of the tissue?
A: Principally yes - all light will cause some heating
if absorbed by tissue. However stronger laser types. like
GaAlAs lasers in the 300-500 mW range may cause a noticeable
heat sensation, particularly in hairy areas, dark tattoo
and on sensitive tissues such as lips. The amount of melanin
in the skin is an important factor; dark skin will be more
heated than fair skin. The biological effects have nothing
to do with heat. Due to increased circulation there is usually
an increase of 0.5-1 degrees Celcius locally.
Does it have to be a laser? Why not use monochromatic
non coherent light?
A: Monochromatic non coherent light, such as light
from LED's can give good effect on superficial tissues such
as wounds. In comparative studies, however, lasers have
shown to be more effective than monochromatic non coherent
light sources, especially in deep tissue.
the coherence of the laser light disappear when the light
is scattered in the tissue?
A: No. The length of coherence,
though, is shortened. Through interference between laser
rays in the tissue, very small "islands" of more
intense light, called speckles occur. These speckles will
be created as deep as the light reaches in the tissue and
within a speckle volume, the light is partially polarized.
It is easy to show that speckles are formed rather deep
down in tissue and the existence of laser speckles prove
that the light is coherent.
therapeutic lasers produce so-called soliton waves?
A: No. Such claims are just sales
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