Restorative*Dentistry*Department,*Federal*University*of*Paraíba,*João*Pessoa,*PB,*Brazil**
Correspondence:*andreulisses@yahoo.com.br*(BATISTA*AUD)*|*Received*09*Jul*2014*Received'in'revised'form*12*Jul*2014*Accepted*18*Jul*2014*
*
*
LEITE
,*Priscila*Kelly*Batista*da*Silva**
MELO
,*Nicole*Freitas*Pereira**
SILVA
,*Pâmela*Lopes*Pedro**
MONTENEGRO
,*Robinsom*Viégas**
BONAN
,*Paulo*Rogério*Ferreti**
BATISTA
,*André*Ulisses*Dantas**
*
*
*
*
*
*
*
*
*
*
*
LOW=LEVEL'LASER'THERAPY'FOR'
TEMPOROMANDIBULAR'DISORDERS'
(TMD)'TREATMENT:'A'SYSTEMATIC'
REVIEW'OF'RANDOMIZED'TRIALS'
*
*
*
ABSTRACT'
*
AIM:* Conducting* a* systematic* review* of* randomized* clinical* trials*
focusing* on* the* efficacy* of* LLLT* on* pain* control* in* patients* with*
TMD,* diagnosed* by* the* Research* Diagnostic* Criteria* for*
Temporomandibular* Disorders* (RDC/TMD).*
MATERIAL' AND'
METHODS:* Search* was* performed* at* PubMed/MEDLINE* database*
with* the* terms:* (1)* “Laser* AND* temporomandibular* disorders”;*(2)*
“Laser* AND* temporomandibular* disorders* AND* RDC/TMD”;* (3)*
“Lowalevel* laser* therapy* AND* temporomandibular* disorders”;* (4)*
“Lowalevel* laser* therapy* AND* temporomandibular* disorders* AND*
RDC/TMD”;* (5)* “Lowalevel* laser* therapy* AND* temporomandibular*
joint* dysfuntion* syndrome”;* (6)* “Lowalevel* laser* therapy* AND*
temporomandibular*joint*dysfuntion*syndrome*AND*RDC/TMD”;*(7)*
“Laser* AND* temporomandibular* joint* dysfuntion* syndrome”* (8)*
“Laser* AND* RDC/TMD”;* (9)* “Lowalevel* laser* therapy* AND*
RDC/TMD”.*Inclusion*criteria:*articles*need*to*be*randomized*clinical*
trial* performed* in* humans;* evaluate* the* effect* of* LLLT* in* the*
treatment* of* TMD* diagnosed* by* the* use* of* RDC/TMD;* published* in*
English*or*Portuguese*in*the*last*10*years.*Protocol*studies*and*pilot*
studies* were* excluded.' RESULTS:* Ten* studies* were* included.* The*
type*of*laser*used*was*Gallium*Aluminum*Arsenide*(GaAlAs)*diode,*
with*exception*of*1*paper,*which*used*super*pulsed*Gallium*Arsenide*
laser.*Eight*studies*reported*decreased*in*pain*levels,*in*two*articles*
there* was* no* statistically* significant* difference* between* test* and*
placebo*groups.*CONCLUSION:*In*most*studies,*LLLT*was*effective*in*
pain* remission,* but* there* is* no* standardization* in* parameters* like*
wavelength,* output* power* and* frequency.* Studies* with* more*
complex* experimental* designs,* standardized* diagnostic* criteria* for*
TMD* and* defined* protocols* for* the* use* of* LLLT* are* needed* to*
determine*its*efficacy*in*the*treatment*of*TMD.*
'
'
KEYWORDS'
*
INTRODUCTION
Temporomandibular. disorder.(TMD). is.
term.that. includes. several. disorders. involving.
masticatory.muscles,.temporomandibular.joint.
(TMJ). and.orofacial. structures
1
.. Besides,. TMD.
is. considered. as. a. musculoskeletal. disorders.
subclass
2
.. It. possesses. multifactorial. etiology.
and.a.multidisciplinary.approach.is. necessary.
in.its.therapy...
)
Nowadays. there. are.two. main. systems.
for. classiDication. and. diagnosis. of.TMD. which.
are. accepted. worldwide,. the. American.
Academy. of. Orofacial. Pain. (AAOP). and. the.
Diagnostic. Criteria. for. Temporomandibular.
Disorders.Research.(RDC./.TMD)..According.to.
the. AAOP,. TMD. is. divided. into. two. large.
groups.of.disorders:.muscle.TMD.and.articular.
TMD
3
...
.
Dworkin. and. LeResche
4
. (1992),. when.
published.the. Research.Diagnostic. Criteria. for.
Temporomandibular. Disorders. (RDC/TMD),.
suggested. deDined. and. validated. criteria. to.
classify. TMD. patients. in. three. diagnostic.
groups:.Group.I.–.Muscle.disorders,. Group.II.–.
Disc. displacements.and. Group.III. R. Arthralgia,.
osteoarthritis. and. osteoarthrosis,. and. this.
classiDication. is. considered. the. Golden.
standard. in. TMD. diagnosis. research.. The.
diagnosis. is. given. through. two. axis. bringing.
information. on. clinical. evaluation. and. TMD.
classiDication. (Axis. I). and. psychosocial.
evaluation.(Axis.II).of.TMD
5
..Hence,.the.criteria.
e s t a b l i s h e d. b y. R D C / T M D. b r i n g. a.
standardization.for.diagnosis. on.TMD.and.it.is.
an.effective.tool.for.controlled.clinical.studies..
.
For. pain. treatment. of. TMD. patients,.
several. techniques. has. been. suggested,.
prioritizing. the. use. of. conservative. therapies.
such.as.physical.therapy,.acupuncture,.occlusal.
splints,. behavioral. cognitive. interventions,.
drug. therapy. and. lowRlevel. laser. therapy
1
..
Given.that,. invasive.or.irreversible.treatments,.
like. complex. occlusal. therapies,. occlusal.
adjustment.and.surgeries.should.be.avoided.as.
the.Dirst.choice.in.therapy.
.
Several. types. of. phototherapy. devices.
with. different. characteristics. are. available.
including. those. which.use.laser.light.. HeliumR
neon. laser. (HeNe). and. Gallium. Arsenide. and.
Aluminum. laser. (GaAlAs). are.highlighted.. The.
laser.often.applied.in.Dentistry.to.treat.TMD.is.
the.GaAlAs.laser.due. to. its.analgesic. and.antiR
inDlammatory.effects
6
.. Wavelength.of.choice.is.
infrared,..ranging.from.780R904.nm7,.due.to.its.
higher.penetration.power
7
.
.
The. use. of. LowRlevel. laser. therapy.
(LLLT). presents. bio. stimulant,. regenerative,.
analgesic. and. antiRinDlammatory. efDicacy,. also.
providing.the.possibility.to. act.on.the.immune.
system
8
.. Due. to. its. alegated. analgesic. effect,.
LLLT. has. been. suggested. for. TMD. clinical.
treatment..
.
The. low. power. pulse. of. GaAlAs. laser.
showed. signiDicant. stimulating. effects. on. the.
Dibroblasts. activity,. increasing. the. connective.
tissue. repair.. The. analgesia. was. explained.
377
suggesting.there.is.an.effect.on.the.stimulation.
of. peripheral. nerves. and. of. micro. circulation.
regulation,.interrupting.the.vicious.circle.in.the.
pain.origin.and.development
9
..
.
Regarding. to. the. laser. use. on. TMD.
treatment,. the.evidences. are. relatively. recent..
There. are. several. differences. on. regarding.
research. protocols,. studied. population,.
diagnostic. criteria. used,. laser. type. tested,.
intensity. of. energy,. number. and. places. of.
applications. and. use. or. not. of. placebo.. Many.
times. it. generates. controversial. results. and.
questioning.about.the.real.efDicacy.on.the.LLLT.
treatment. for.pain.control. in.TMD.patients.. In.
many.studies,.the.protocols.used.do.not.follow.
scientiDic. rules. accepted. for. clinical.
investigation. and. they. have. little. credibility.
d u e. t o. t h e. l a c k. o f. d e t a i l i n g. a b o u t.
methodology
8
.
.
Thus,. the. purpose. of.this. study. was. to.
assess,. through.a.systematic. literature.review.
of. randomized.clinical. trials,. the.effectiveness.
of. LLLT. in. the. treatment. of. TMD. pain,.
diagnosed.by.RDC./.TMD.criteria,.verifying.the.
LLLT. efDicacy. on. RDC/TMD. subgroups,. the.
laser. type,. number. of.irradiated. points,. study.
duration,. interval. between. applications,.
applied. energy,. power. and. application. time.
with. better. results.. Also,. it. will. try. to.
determine. if. there. is. a. well. deDined. LLLT.
protocol. for. TMD. treatment. in. the. current.
literature..
MATERIAL)AND)METHODS
A. systematic. literature. review. was.
performed. using. the. data. base. PubMed/
MEDLINE. (International. Literature. in. Health.
S c i e n c e s ). a v a i l a b l e. o n. h t t p : / /
www.ncbi.nlm.nih.gov/pubmed.. Search. terms.
were. selected. in. articles. about. the. theme,.
previously. chosen. and. on. MESH. (Medical.
Subject. Headings). keywords. available. on.
http://www.ncbi.nlm.nih.gov/mesh.. These.
describers. were. used. singly. and. grouped,.
resulting.on.the.following.search.strategy:. (1).
“Laser. AND. temporomandibular. disorders”;.
(2).“Laser.AND.temporomandibular. disorders.
AND.RDC/TMD”;. (3). “LowRlevel. laser. therapy.
AND.temporomandibular.disorders”;.(4).“LowR
level. laser. therapy. AND. temporomandibular.
disorders.AND.RDC/TMD”;.(5).“LowRlevel.laser.
therapy. AND. temporomandibular. joint.
dysfuntion. syndrome”;. (6). “LowRlevel. laser.
therapy. AND. temporomandibular. joint.
dysfuntion. syndrome. AND. RDC/TMD”;. (7).
“Laser. AND. temporomandibular. joint.
dysfuntion. syndrome”. (8). “Laser. AND. RDC/
TMD”;. (9).“LowRlevel. laser. therapy.AND.RDC/
TMD”.
.
Nine. searches. were. performed.. On. the.
Dirst,.Difth.and.seventh.ones,.the.Dilters.from.the.
website. Pubmed. were. included. to. reDine. the.
research,. such. as:. clinical. trial,. randomized.
clinical.trial.e.10.years..On.the.third.search,.the.
Dilters.clinical.trial
)
and.10.years.were.used..On.
the.others.(two,. four,. six,. eight. and.nine),. the.
Dilters. were. not. used,. since. only. few. matches.
were.found..Each.article.was.revised.and.singly.
selected. by. an. examiner,. based. on. the.
inclusion. criteria. described:. (A). randomized..
clinical.trial;.(B).research.in.humans;.(C).use.of.
LLLT. for. TMD. treatment;. (D). TMD. diagnosed.
by.RDC/TMD.(Research.Diagnostic.Criteria.for.
Temporomandibular. Disorders). Axis. I;. (E).
published. in. English. or. Portuguese;. (F).
published. . in. . the. . last. . 10. years.. NonR
concluded.randomized..clinical.trials.were.not.
included..
RESULTS
The. Dinal. electronic. search. resulted. in.
66.matchs,. as. listed.on. the. Table. 1.. After. the.
revision.of.all.the.articles.found,.the.duplicates.
were.removed.and.the.exclusion.based.on.the.
title. and. abstract. was. performed,. and. 11.
studies. were. selected.. Next,. they. were. suited.
to. the. inclusion. criteria. proposed. on. the.
methods,. and. 10. articles. were. selected,. and.
one.study.was. excluded. because.it. was. in.the.
conclusion. stage. yet. (Table. 2).. The. Figure. 1.
demonstrates.how.the.selection.of.articles.was.
carried.out.in.this.study..
.
Table. 3. presents. data. extracted. from.
the.selected. papers:. author,. year. and. country.
where.the.study.was.performed,.as.well.as.the.
TMD. classiDication. (according. to. RDC/TMD),.
study.type,. number.of.subjects.evaluated,. age,.
presence. or. absence. of. control,. . evaluation.
period,. laser. type,. laser. energy. and. dose. as.
well.as.the.most.signiDicant.results..
.
The. TMD. classiDication. by. RDC/TMD.
occurred. as. follows:. group. I. –. myofascial.
pain
7,10,15
;. group. II. –. disc. displacement
14,15,17
;.
group. III. –. arthralgia
1,14
.. The. study. by.
Rodrigues. et. al.
14
. (2013). was. the. only. one.
which. allowed. patients. with. any. RDC/TMD.
classiDication,.in.the.Group.I,.II.or.III.
.
The. number. of. patients. in. the.
researches. varied. from. 10. (Rodrigues. et. al.,.
2010). to. 99. (Marini,. Gatto. e. Bonetti;. 2010),.
and. the. female. gender. were. prevalent,. what.
corroborates. with. several. studies. that. show.
the.high.prevalence.of.TMD.in. female.gender..
All.the.studies.presented.control.group,.except.
for.Melchior. et. al.. (2013).and.Rodrigues.et.al..
(2013)..The.period.of.study.and.the.quantity.of.
sessions. applied. on. the. patients. varied.
signiDicantly. among. the. studies,. as. can. be.
observed.on.the.Table.3..
.
The. standard. laser. type. used. was.
Gallium. Arsenide. and. Aluminum. laser.
(GaAlAs). diode. in. all. the. studies,. except. for.
Marini,. Gatto. e. Bonetti
16
(2010),. who. used.the.
super.pulsed.Gallium.Arsenide.laser.with.wave.
length. γ. =. 910. nm.. The. wave. length. in. the.
other.studies.varied.from.780.to.830.nm..
379
Table21.2Number2of2articles2found2for2each2term2researched.2
Term)used)for)search
Number)of)results)
laser.AND..temporomandibular.disorders
24
laser.AND..temporomandibular.disorders.AND.RDC/TMD
02
low.laser.therapy.AND.temporomandibular.disorders
19
low.laser.therapy.AND.temporomandibular.disorders..AND.RDC/TMD
01
low.laser.therapy.AND.temporomandibular.joint.dysfunction.syndrome
06
low.laser.therapy.AND.temporomandibular.joint.dysfunction.syndrome..AND.RDC/TMD
01
laser.AND..temporomandibular.joint.dysfunction.syndrome
08
Laser.AND.RDC/TMD
03
Low.laser.therapy.AND.RDC/TMD
02
Table22.2Article2excluded2after2complete2evaluation.
Author)and)year
Exclusion)criteria
Godoy.et.al.(2013)
10Study.in.recruiting.stage
Figure21.2Experimental2draw2for2this2study.
.
About.energy.(J/cm²).and.power.(mW),.
a.great.variety.of.parameters.used.can.be.seen..
The.energy.used.varied.from.3.J/cm².to.105.J/
cm²,.and.the.power.from.10.mW.to.400.mW..
Ta
bl
e&3.&Descript
ion&of&sel
ect
ed&a
rt
icl
es&a
ccording&t
o&t
he&eva
lua
tion&crit
eria
&proposed.&
Author
TMD*classif
Type*of*study
Sample
Con
trol*group
Quan
t*of*session
s/
period*of*study
Laser*type
En
ergy,*power*an
d*
applic
ation
*time
Results
1.&
Çet
iner,&
Kahraman,&Yucetas,&
(2006)
7Mus
cle
&T
MD
&G
ro
up&
I:&myofascial&pain
Randomized&
cont
rol
led&Cl
inical
&
tr
ial&
39&(4&men&and&35&
women)
Test
&group:&24&
patients
Con
trol
&g
rou
p:&
15&
(l
aser&t
urned&off)
16&
to&
62&
yea
rs&
ol
d
Yes&(15)&–placebo&
las
er
&(
tur
ne
d&o
ff
)
10&
sessions&
divided&
int
o&&2&w
eek
s,&ex
cept
&
we
eke
nd
s
GaAlAs&(830&
nm&–&infra&
red)
7&J/cm²
No&information
by
&1
62
s
Improvement&on&maximum&
mouth&opening,&pain&and&
masticatory&difYicult&
redu
ct
ion
&w
ere&
st
at
ist
ica
lly&
signiYica
nt
&in&
the&
test
&grou
p&
when&compared&to&the&
control&one.&C
onclusion&Z&
LLLT&
w
as&
effect
ive.
2.&
De&
Ca
rl
i&et
&a
l.,&
(2013)
1Mus
cle
&and
&o
r&jo
int&
TM
D
Pat
ient
s&coul
d&have&
ot
her&TM
D&
subtypes,&inasmuch&
as
&d
iagno
se
d&wi
th
&
changes&of&Group
IIIa&Z&Arthralgia
Randomized&doubleZ
bli
nd
&c
ontr
olle
d&
Cl
in
ica
l&t
ria
l&
32&(29&women&and&3
&
men)
G1:laser+20&mg&de&
piroxicam&(11)
G2:l
Ta
bl
e&3.&Descript
ion&of&sel
ect
ed&a
rt
icl
es&a
ccording&t
o&t
he&eva
lua
tion&crit
eria
&proposed.&
Author
TMD*classif
Type*of*study
Sample
Con
trol*group
Quan
t*of*session
s/
period*of*study
Laser*type
En
ergy,*power*an
d*
applic
ation
*time
Results
4.&Gokçen<Rohlig&et&
al.,&(
20
12
)
13Mus
cle
&T
MD
Group&I:&&myofascial&
pain
Randomized&
cont
rol
led&Cl
inical
&
tr
ial
40&(28&women&and&
12&men)
Group&t
est
:&l
aser&
(20)
Group&cont
rol
:&
hea
lt
hy&individua
ls
Average&33&years&
ol
d
Ye
s&(
20
)&G
ro
up&
cont
rol
:&heal
thy&
individua
ls
3×&a&week&–&10&
sessions
GaAlAs&(820&
nm&–&infra&
red)
3&J/cm²
300&mW&by&10s
No&information&on&
the&number&of&
appli
cati
on&po
ints
&
There&w
as&pa
in&decrea
se&on
&
th
e&gr
oup&i
rr
ad
iate
d,&but&no
&
changes&on&t
he&b
it
e&force.&
Conclusion&<&LLLT&was&
effect
ive&on&pa
in&rel
ief,&b
ut
&
it
&does¬
&provide&
improvement&on&the&bite&
force.&
5.&
M
arini,&
Ga
tt
o,&
Bo
ne
tti
,&(
20
10
)
14Join
t&TM
D
Cha
ng
es&
of&
Grou
p&
II
&
–&disc&displacement&
wi
th
out&r
ed
uc
ti
on&
and&Group&III&–&
ost
eoa
rt
hrit
is
Randomized&double<
bli
nd
&c
ontr
olle
d&
Cl
in
ica
l&t
ria
l
99&(74&women&and&
25&men)
GL:&l
aser&(39)
GD:&Ib
uprofen&800&
mg&(30)
GC:&pl
aceb
o&l
aser&
(30)
15&
a&
50&
yea
rs&
ol
d
Ye
s&
(G3:30)&pl
aceb
o&
las
er
10&
sessions&
al
ong&
2&
we
eks
SLLLT&–&
Arsenide&
diode&
gallium,&
su
per&
pu
lsed&
laser&–&910&
nm
No&information
400&mW
Appliction&of&20kH
z&
por&10&min,&18&kH
z&
by&5&min&and&16kH
z&
by&5&min
The&pain&decreased&more&
wi
th
&SL
LL
T
&th
an&o
n&th
e&
medicine&groups&and&
control&from&5th&day&until&
th
e&e
nd
&o
f&th
e&pe
ri
od
.&&On&
the&mouth&opening&and&side
&
movements,&the&superiority&
of&SLLLT&w
as&evident
&one&
month&after&the&treatment.&
Conclusion&–the&laser&was&
effect
ive&on&t
he&pa
in&
treatment.
6.&
M
el
chior&
et
&a
l.,&
(2013)
15My
of
as
ci
al&pai
n&wi
th
&
or&w
it
hout
&joint
&
TM
D
Group&I&–myofascial&
pain&can&pr
es
ent&
ot
her&cha
nges&of&
gr
oups&II&and&III
Randomized&
cont
rol
led&Cl
inical
&
tr
ial
12&(all&women)
All&of&the&group&test&
–&laser
18&
to&
60&
yea
rs&
ol
d
No
2&
sessions&
a&
w
eek
&
du
ring&
4&
w
eek
s
(8&sessions)
GaAlAs&(780&
nm&–&infra&
red)
60&J/cm²
60&mW
by
&4
0&s
&in&e
ac
h&
point&(total&4
&
points
)
There&w
as&signi_ica
nt
&
decrea
se&
on&
the&
va
lu
es&
of&
pain&s
ubjective&to&palpation&
(p&<0.05).&Initial&pain&(A1)&
was
&s
igni
_ic
ant&d
iff
er
ent&o
f&
A2&(30&days&after&
treatment),&but&it&was&no&
signi_icantly&different&of&A3&
(30&days&after&treatment).&
Pain&improvement&did¬&
Ta
bl
e&3.&Descript
ion&of&sel
ect
ed&a
rt
icl
es&a
ccording&t
o&t
he&eva
lua
tion&crit
eria
&proposed.&
Author
TMD*classif
Type*of*study
Sample
Con
trol*group
Quan
t*of*session
s/
period*of*study
Laser*type
En
ergy,*power*an
d*
applic
ation
*time
Results
7.& O z& et &a l.,& (2010) 16 Mus cle &T MD Group&I&–&myofascial& pain Randomized&controlled & Cl in ica l&t ria l 40&(34&women&and&6& men) Group&t est :&l aser&(20) Group&cont rol :&occl usa l& splint&by&3&months Average&32&years&old Ye s (Cont rol &w it h&occl usa l& sp lint &u sed& 24h& hou rs& a& day&during&3&months) Twice&a&week&P&10& sessionsGaAlAs&diode& laser
,&8
20
&nm
3&J/cm² 300mW by
&1 0s No&information&on&the& number&of&application& points Bo th &o f&th e&gr oups &pr es ente d& decrea sed& sensit ivit y& to& palpation&of&muscles& signiXicantly.&C onclusion&P&LLLT& is&a s&effect ive&a s&t he&occl usa l& sp lint &on& the& pa in& decrea se& and& mandibular&movement& improvement.& 8.& Rodrigu es& et &a l.,& (2013) 17 Mus cle &T MD &and /o r& joint Allowed&patients&with& any&clas si Xicati on&o f& RD C:&Gr oup&I:& myofascial&pain,&Group& II:&disc&displacement&or &
Group&III:&Arthralgia,& arth
ri ti s&e &ar tr ho si s Randomized&controlled & Cl in ica l&t ria l
10&(9&women&and&1& man)&all&elderly 63&
to& 82& yea rs& ol d No 2& sessions& a& w eek & du ring& 4& w eek s (8&sessions)
GaAlAs&diode& laser
,&7 80 &nm My of as ci al&pai n: 5&J/cm² 10&mW&by&20s Join t&TM D: 105&J/cm² 70&mW&by&60s The&resul ts&show ed&signiXica nt & pain&r ed uction&in&all&the& patients.&C onclusion&P&LLLT&was& effect ive&on&t he&pa in&reduct ion& ando&n&the&movement&in&TMD& el derl y&pa tient s. 9.& Sil va &et &a l.,& (2012) 18 Mus cle &T MD &and /o r& joint Repor ts&that&all&the& patients &s hould &have& int ra &joint &TM D.&Resul ts & ar e&no t&d etai le d&by&RD C& dia gnosis& Randomized&doubleP bli nd &c ontr olle d& Cl in ica l&t ria l 45&(30&women&and&15& men) 3& grou ps
G1:&Laser&(52.5&J/cm2) G2:&Laser&105&J/cm2 G3:&pl
aceb o&l aser 25& to& 53& yea rs& ol d Ye s (G3:&pl aceb o&l aser) 2& sessions& a& w eek & du ring& 5& w eek s (10&sessions) GaAlAs&(780& nm&–&infra&red) G1:&52.5&J/cm²&(30s) G2:&105&J/cm² (60s) G3:&0&J/cm² (30s) 70&mW 5& joint &p oint s& and& 4& muscle The&resul ts&show ed&signiXica nt &
statistically&difference&among& the&gr
oups .&T he &pati ents &o f&G 2& ha d&fa st er&response.&Concl usion&
P&LLLT&was&effective&on&the& mandibular&movement& improvement&and&pain&
redu ct ion .& 10.& Venezia n& et &a l.,& (2010) 19 Mus cle &T MD & Group&I&–myofascial& pain&(Ia&e&Ib) Randomized&controlled & Cl in ica l&t ria l 48&(43&women&and&5& men)& G1:&Laser&(25&J/cm2) G2:&pl aceb o&l aser G3:&Laser&(60&J/cm2) G3:&pl aceb o&l aser 18& to& 60& yea rs& ol d Ye s (G2&a nd&G4&w ere& placebo) Tw ice&a &w eek &during&4& we eks (8&sessions)
GaAlAs&diode& laser