1-Q: What is LLLT, LPLT, therapeutic laser,
soft laser, MID laser ?
2-Q: Is laser therapy scientifically well
documented ?
3-Q: But I have heard that there are dozens
of studies failing to find any effect of LLLT ?
4-Q: Which lasers can be used in medicine ?
5-Q: Can therapeutic lasers damage the eye ?
6-Q: How do I know which laser I should buy ?
7-Q: How come some LLLT equipment has power
in watts and some only in milliwatts ?
8-Q: Which type of laser is best suited to
which job ?
9-Q: Can carbon dioxide lasers be used for
LLLT ?
10-Q: How deep into the tissue can a laser
penetrate ?
11-Q: Can LLLT cause cancer ?
12-Q: What happens if I use a too high dose ?
13-Q: Are there any counter indications ?
14-Q: Does LLLT cause a heating of the tissue
?
15-Q: Does it have to be a laser? Why not use
monochromatic non coherent light ?
16-Q: Does the coherence of the laser light
disappear when entering the tissue ?
1
Q: What is LLLT, LPLT, therapeutic laser, soft laser, MID laser ?
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 laser". "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". 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.
2
Q: Is laser therapy scientifically well documented ?
A:
Basicly yes. There are some 100 double-blind positive studies
confirming the clinical effect of LLLT. More than 2000 research reports
are published. Looking at the limited LLLT dental literature alone (265
studies), more than 90% of these studies do verify the clinical value
of laser therapy.
3
Q: But I have heard that there are dozens of studies failing to find
any effect of LLLT ?
A:
That 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 negtive studies will reveal serious flaw. 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.
4
Q: Which lasers can be used in medicine ?
A:
Examples of lasers which can be used in medicine: Laser name Wavelength
Pulsed Use in medicine or cont. Crystalline laser medium: Ruby 694 nm p
holograms, tattoo coag. Nd:YAG 1 064 nm p coagulation Ho:YAG 2 130 nm p
surgery, root canal Er:YAG 2 940 nm p surgery, dental drill KTP/532 532
nm p/c dermatology Alexandrite 720-800 nm p bone cutting Semiconductor
lasers: GaAs 904 nm p biostimulation GaAlAs 780-820-870 nm c
biostimulation, surgery InGaAlP 630-685 nm c biostimulation Liquid
laser: Dye laser (tuneable) p kidney stones Rhodamine: 560-650 nm c/p
PDT, dermatology, Gas lasers: HeNe 633, 3 390 nm c biostimulation Argon
350-514 nm c dermatology, eye CO2 10 600 nm c/p dermatology, surgery
Excimer 193, 248, 308 nm p eye, vascular surgery Copper vapour 578 nm
c/p dermatology There are many other types, but those mentioned above
are the most common
5
Q: Can therapeutic lasers damage the eye ?
A: Yes
and no! Read the following: The following factors are of importance
regarding the eye risk of different lasers: 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
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 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 infra-red
laser or an infra-red 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. If the light source is concentrated,
which is often the case in the context of lasers, an image of the
source is projected on the retina as a point, provided it lies within
our accommodation range, i.e. the area in which we can see clearly. A
widely spread light source is projected onto the retina in a
correspondingly wide 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 (which is apprehended as a more concentrated light
source) penetrates the eye more than a so-called "pearl" light bulb. A
laser system with several light sources placed separately, such as a
multiprobe (the probe is the part of the laser you hold and apply to
the area to be treated: a single probe means there is only one laser
diode in the probe, as opposed to a multiprobe, which has several laser
diodes) with several laser diodes, can, seen as a whole, be very
powerful but at the same time constitute a smaller hazard to the eye
than if the entire power output was from one laser diode, because the
diodes' separate placement means that they are reproduced in different
places on the retina. We have often heard this kind of remark: "If it's
a class 3B laser then it's fine, otherwise it has no effect....". This
is of course entirely incorrect and has lead to a situation where
manufacturers have produced lasers to meet the 3B classification, so
that they will sell in greater volumes. Let us look at a couple of
examples: * A GaAlAs laser with a wavelength of 830 nm, an output of 1
mW and a well collimated beam (1 mrad divergence) is classified as
laser class 3B as it is judged to be hazardous to the eye. The reason
for this is partly the collimated beam, and partly the wavelength,
which is just outside the visible range and hence provokes no blink
reflex in strong light. * A HeNe laser with a wavelength of 633 nm, an
output of 10 mW and divergent beams (1 rad divergence, which coresponds
to a cone of light with a top angle of about 57°) is classified
as laser class 3A because, owing to its divergence, it cannot damage
the eye. With the recent advent of "high power low power lasers", i.e.
GaAlAs lasers in the range 100-500 mW there is another story. These
lasers are indeed dangerous for the eye and should only be used by
qualified persons and with proper protective measures taken.
6
Q: How 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. 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 For oral work and wound healing HeNe and GaAlAs are the most
common types, with GaAlAs as the most versatile one. Sterilizeable
probes are normally only available for GaAlAs lasers. 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.
4 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 dosage 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 dosage measured? What
kind of dosage is too high, and what is too low? 5 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. 6 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 an intensity
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. 7 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? 8 In most countries,
therapy lasers must be approved. 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 is either not a laser, or is being sold illegally. 9 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? 10
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?
7
Q: How come some LLLT equipment has power in watts and some only in
milliWatts ?
A:
This applies to GaAs lasers. When a GaAs laser 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 dosage 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 watt peak pulse output" naturally
seems more impressive than 35 milliwatts average output! Rule of thumb
is: Take the "watt peak pulse" figure, divide by 2, and you have the
average output in mW.
8
Q: 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 same instrument. *
The HeNe laser or InGaAlP laser is used a great deal in dentistry in
particular, as it was the first laser available. The HeNe laser has now
been used for wound healing for more than 30 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 25 mW is available. An optimal dosage
when using a HeNe laser for wound healing is 0.5-1.0 J/cm2 around the
edge of the wound, and approximately 0.2 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, neuralgia, etc. It should be noted that HeNe
fibres cannot be sterilized in an autoclave. The alternative is to use
alcohol to clean the tip, or to cover it with cling-film or a
thermometer sleeve. HeNe lasers cost somewhere between US $3,000 and
$4,000, depending on their power output and the quality of their
fibres. InGaAlP lasers of the same power costs usually about half as
much and can be had with considerably higher output. * 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 oral use. Prices are usually between US
$3,000 and $6,000 for output power between 4 and 20 mW. A GaAs laser
needs an integral output meter that shows that there is a beam and its
strength in milliwatts - this is necessary because the light this type
of laser emits is invisible. Protective glasses for the patient may be
appropriate in view of the invisible nature of the light. In older
systems the power output of conventional apparatus follows pulsation.
This means that a GaAs laser with an average output of 10 mW when
pulsing at 10,000 Hz, only produces 1 mW when pulsed at 1,000 Hz, and
at 100 Hz only 0.1 mW. If you therefore want to administer treatment at
low frequencies around e.g. 20 Hz (for the treatment of pain), the
output power is, clinically speaking, unusable. However, there are GaAs
lasers with "Power Pulse", which means that the power output is held
constant at all pulse frequencies. This would be of interest to a
physiotherapist, for example, when one considers that the GaAs laser
has the deepest penetration of the common therapeutic lasers. Large
doses can be administered to deep-lying tissue over a short period of
time. A GaAs multiprobe can also shorten treatment times for conditions
involving larger areas (neck/shoulders). The GaAs laser is, like GaAlAs
and InGaAlP lasers, a semicon-ductor 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 0.1 J/cm2. * The GaAlAs laser has
become increasingly popular during the 1990s. As it is very easy to run
electrically, small rechargeable lasers have been put on the market
which are not much larger than an electrical toothbrush. (They can run
on normal or rechargeable batteries.). 20-30 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 400 mW. Many GaAlAs lasers have
well-designed, exchangeable, sterilizeable intraoral probes. Output
meters are essential because the light from this type of laser is
largely invisible. The price tag for a GaAlAs laser of around 30 mW can
be between US $3,000 and $4,000, excluding value added tax. Price
differences depend on factors such as output, ergonomics, and standard
of hygiene, to name but a few. GaAlAs lasers of 300-500 mW are in the
range $4.000-$6.000 .
9
Q: Can carbon dioxide lasers be used for LLLT ?
A:
Yes.Therapeutic laser treatment with carbon dioxide lasers have 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 that 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. There are small, portable CO2 lasers on the market today -
even battery-driven ones - producing up to 15 watts, which is more than
enough power output! Prices in the range of $ 10,000 - $25,000. 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
tranmsitter substances from superficial blood vessels. Conventional
LLLT wavelengths combine this effect with "direct hits" in the deeper
lying affected tissue.
10
Q: How 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 in contact treatment. 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 can even penetrate bone (as well as it can penetrate
muscle tissue). Fat tissue is more transparent than muscle tissue. For
example: a HeNe laser with a power output of 3.5 mW has a greatest
active depth of 6-8 mm depending on the type of tissue involved. A HeNe
laser with an output of 7 mW has a greatest active depth of 8-10 mm. A
GaAlAs probe of some strength has a penetration of 3.5 cm with a 5.5 cm
lateral spread. A GaAs laser has a greatest active depth of between 20
and 30 mm (sometimes down to 40-50 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.
11
Q: Can 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. 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 has 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 right treatment with LLLT
12
Q: What happens if I use a too high dose ?
A: You
will have a biosuppressive 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.
13
Q: Are there any counter indications ?
A: You
should not treat cancer, for legal reasons. Pregnant women is not a
counter indication, if used with common sense. Pace makers are
electronical, do not respond to light. The most valid counter
indication is lack of medical training.
14
Q: Does LLLT cause a heating of the tissue ?
A: Due
to increased circulation there is usually an increase of 0.5-1
centigrades locally. The biological effect have nothing to do with
heat. GaAlAs lasers in the 300-400 mW range may cause a noticable heat
sensation, particularly in hairy areas.
15
Q: 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 be
useful for superficial tissues such as wounds. In comparative studies,
however, lasers have shown to be more effective than monochromatic non
coherent light sources. Non coherent light will not be effective in
deeper areas.
16
Q: Does the coherence of the laser light disappear when entering the
tissue ?
A: No.
The length of coherence, though, is split into very small coherent
"islands" called specles. These specles remain coherent and will
penetrate deeply into the tissue.
