Pain relief by single low-level laser irradiation appliance therapy

ORIGINAL ARTICLE
Pain relief by single low-level laser irradiation
in orthodontic patients undergoing fixed
appliance therapy
Dritan Turhani,a Martina Scheriau,b David Kapral,b Thomas Benesch,c Erwin Jonke,b and
Hans Peter Bantleond
Vienna, Austria
Introduction: The objective of this study was to analyze the effect of single low-level laser therapy (LLLT)
irradiation on pain perception in patients having fixed appliance treatment. Methods: Seventy-six patients
(46 women, 30 men; mean age, 23.1 years) enrolled in this single-blind study were assigned to 2 groups. The
patients in group 1 (G1; 38 patients, 13 men, 25 women; mean age, 25.1 years) received a single course of
LLLT (Mini Laser 2075, Helbo Photodynamic Systems GmbH & Co KG, Linz, Austria; wavelength 670 nm,
power output 75 mW) for 30 seconds per banded tooth. The patients in group 2 (G2; 38 patients, 17 men,
21 women; mean age, 21.0 years) received placebo laser therapy without active laser irradiation. Pain
perception was evaluated at 6, 30, and 54 hours after LLLT by self-rating with a standardized questionnaire.
Results: Major differences in pain perception were found between the 2 groups. The number of patients
reporting pain at 6 hours was significantly lower in G1 (n ⫽ 14) than in G2 (n ⫽ 29) (P ⬍.05), and the
differences persisted at 30 hours (G1, n ⫽ 22; G2, n ⫽ 33) (P ⬍.05). At 54 hours, no significant differences
were seen between the number of patients reporting pain (G1, n ⫽ 20; G2, n ⫽ 25), although the women had
a different prevalence between G1 (n ⫽ 11) and G2 (n ⫽ 15) (P ⫽ .079). At 6, 30, and 54 hours, more than
90% of the subjects in both groups described the pain as “tearing.” Conclusions: LLLT immediately after
multibanding reduced the prevalence of pain perception at 6 and 30 hours. LLLT might have positive effects
in orthodontic patients not only immediately after multibanding, but also for preventing pain during treatment.
(Am J Orthod Dentofacial Orthop 2006;130:371-7)
P
ain, lasting 2 to 4 days after fixed appliances are
placed, is a common clinical symptom in orthodontic patients.1-5 Pain reduces patient acceptance and compliance, and might even prompt discontinuation of treatment. To find alternatives to pain relief
by drugs, investigators have looked at low-level laser
therapy (LLLT).6-8 LLLT is well-established clinically
in dentistry because of its anti-inflammatory and regenerative effects and its conditioning effect on tooth
enamel.9-14
The mechanisms underlying pain relief by LLLT
are still poorly understood. Some authors attribute the
analgesia to the anti-inflammatory and neuronal effects
From the Medical University of Vienna, Vienna, Austria.
a
Resident, Department of Oral and Maxillofacial Surgery.
b
Resident, Department of Orthodontics, Dental School.
c
Resident, Department of Medical Statistics.
d
Professor and head, Department of Orthodontics, Dental School.
Sponsored by Bank Austria Creditanstalt.
Reprint requests to: Dr Dritan Turhani, Vienna University Clinic of Dentistry,
Department of Orthodontics, Waehringerstrasse 25 a, A-1090 Vienna, Austria;
e-mail, dritan.turhani@meduniwien.ac.at.
Submitted, September 2004; revised and accepted, April 2005.
0889-5406/$32.00
Copyright © 2006 by the American Association of Orthodontists.
doi:10.1016/j.ajodo.2005.04.036
of LLLT,15 including stimulation of nerve cell and
lymphocyte respiration, stabilization of membrane potentials and the release of neurotransmitters in the
inflammatory tissue.16-18 In addition, elongation of
substance P and CGRP-rich neurites was found to be
reduced in vitro.19 In previous studies, pain was reduced by LLLT both after separation and placement of
archwires, but no significant differences were found.6-8
Jones2 reported moderate to severe discomfort in the
first 8 days after the placement of a fixed orthodontic
appliance. Pain intensity was most pronounced in the
first 3 days.
Based on these earlier studies, the effect of LLLT
on pain perception after the placement of a multiband
appliance was investigated in a randomized singleblind trial. Pain intensity and pain quality at 6, 30, and
54 hours were evaluated with a questionnaire developed at the Orthodontic Unit of Heinrich-Heine University, Düsseldorf, Germany.
MATERIAL AND METHODS
Seventy-six patients (46 women, 30 men; mean age,
23.1 years) treated at the Orthodontic Unit, Dental
School, Medical University of Vienna, were included in
371
372 Turhani et al
Table I.
American Journal of Orthodontics and Dentofacial Orthopedics
September 2006
Indications for treatment
Indications for treatment*
G1
G2
Class II Division 1 malocclusion
Class II Division 2 malocclusion
Class III malocclusion
Dental midline discrepancy
Overjet
Overbite
Anterior crossbite
Single-tooth malposition
12
6
5
7
6
4
3
12
12
4
6
11
3
6
5
14
*Patients could have multiple indications.
the trial. They were assigned to 1 of 2 groups. The 38
patients in group 1 (G1; 13 men, 25 women; mean age,
25.1 years) were treated with LLT. Altogether, 542
teeth (mean, 14.91 teeth per patient) were irradiated in
this group. In 19 patients, LLLT was confined to the
maxilla (213 teeth) and, in 11 patients, to the mandible
(141 teeth). Eight patients underwent LLLT irradiation
of both jaws (188 teeth). The 38 patients in group 2
(G2; 17 men, 21 women; mean age, 21.0 years) served
as controls. They were randomly selected and received
placebo laser treatment. Altogether, 511 teeth (mean,
13.45 teeth per patient) were treated in this group. In 21
patients, treatment was confined to the maxilla (239
teeth) and, in 10 subjects, to the mandible (123 teeth).
Seven patients underwent treatment of both jaws
(149 teeth). Informed consent of all patients or their
parents and approval of the ethics commission of the
Medical University of Vienna were obtained before
the start of the treatment. Patients with chronic pain
or histories of neurological and psychiatric disorders
were excluded.
Indications for therapy with fixed appliances are
summarized in Table I. All patients were treated with
fixed appliances; edgewise metal brackets (Ormco,
Glendora, Calif) were placed buccally with the total
etch technique in the anterior teeth, canines, and premolars.
One week after the separation phase, molar bands
(Snap-Fit First Molar Bands, GAC International, Bohemia, NY) were placed. The initial 0.016-in nickeltitanium archwire (Sentalloy, GAC International) was
fixed with preformed 0.09-in steel ligatures (GAC,
International). LLLT was given to bonded and banded
teeth immediately after ligation of the archwires.
Each tooth was treated separately with LLLT.
Analgesia in the separation area was a prerequisite for
treatment with LLLT. Therefore, for the evaluation of
pain intensity, the baseline was set at 0.
Subjects in G1 were treated with LLLT irradiation
(Mini Laser 2075 [dental version], Helbo Photody-
namic Systems GmbH & Co KG, Linz, Austria; 670
nm, 75 mW). This continuing weaves laser consists of
a semiconductor laser chip with a power output tolerance of 20%. Irradiations were made with a dental
applicator (Dent-AP, Helbo) for 30 seconds per banded
tooth at a distance of 5 to 8 mm and at a right angle to
the mucosa at the level of the biomechanical center of
resistance of the tooth. According to the manufacturer,
the power density at 5.5 cm is 140 mW/cm2. The
operator who applied the laser treatment and the placebo could distinguish between them, but the patients
were blinded to the difference (Fig 1).
Pain was evaluated with a standardized questionnaire (Fig 2), a modified version of the questionnaire
developed by the Orthodontic Unit, Heinrich-Heine
University in Düsseldorf, Germany. The patients
were instructed to complete the questionnaire themselves or, if they were less than 13 years of age, with
their parents at 6, 30, and 54 hours after treatment.
The questionnaire collected information about the
prevalence of pain (item 1), the quality (item 2), the
intensity (items 3 and 4), the localization (item 3),
and the time course (item 4) of subjectively perceived pain. Items 3 and 4 were evaluated with a
scale from 0 (no pain) to 5 (unbearable pain). An
additional item, 5, was intended to shed light on the
frequency of pain relief by drugs.
Statistical analysis
Excel (Microsoft, Redmond, Wash) software was
used to compile the data. Statistical analyses were
carried out with SAS software (Cary, NC). Significant
differences in pain prevalence (item 1) were evaluated
with the Fisher exact test (2-sided) (significance level,
P ⬍.05; Bonferroni correction: P ⬍.0033). The intensity of pain (item 3) was analyzed by a general linear
model with fixed effects group, sex, maxillary/mandibular, right/left, anterior/posterior teeth, and time, with
age as the covariable and patients as the random effect.
We used a 2-group chi-square test with a 0.050
2-sided significance level; it had 80% power to detect
the difference between the G1 proportion of 0.500 and the
G2 proportion of 0.800 (odds ratio of 4.000) when the
sample size in each group was 38.
RESULTS
Table II shows the responses to item 1 after
statistical analysis.
Pain at 6 hours was reported by significantly
fewer patients in G1 compared with G2 (P ⬍.05, P
⬍.0033). This difference persisted at 30 hours with
22 subjects in G1 and 33 in G2 (P ⬍.05). At 54
Turhani et al 373
American Journal of Orthodontics and Dentofacial Orthopedics
Volume 130, Number 3
54 hours (n ⫽ 5) than in G2 after 6 hours (n ⫽ 17), 30
hours (n ⫽ 18), and 54 hours (n ⫽ 14).
The smallest differences between G1 and G2 were
observed in patients over 18 years of age. After 54
hours, more patients in G1 (n ⫽ 15) reported pain than
in G2 (n ⫽ 11). There were no significant differences in
male patients and patients over age 18 years between
G1 and G2.
At 6 hours, pain was reported by fewer female
patients in G1 (n ⫽ 9) than in G2 (n ⫽ 16). This
difference persisted at 30 hours (G1, 12; G2, 18). At 54
hours posttreatment, the difference between women
reporting pain in G1 (n ⫽ 11) and G2 (n ⫽ 15) (P ⫽
.079) was somewhat stronger.
The responses to item 2 showed that in both G1
after 6 hours (n ⫽ 12), 30 hours (n ⫽ 19), and 54 hours
(n ⫽ 18) and G2 after 6 hours (n ⫽ 27), 30 hours (n ⫽
30), and 54 hours (n ⫽ 22), 90% of the subjects
reported the pain to be “tearing,” and 67 reported it as
“squeezing.”
The responses to item 3 are summarized in Table III.
They were evaluated separately by quadrants, incisors,
and premolars/molars for G1 and G2. The values in
Table III analyzed with a general linear model showed
no significant difference between any fixed effects and
the covariable. The data suggested no specific trend. No
significant differences between G1 and G2 were found
for the responses to item 5. In G1, 8 patients reported
taking drugs for pain relief vs 9 in G2. Analysis of the
data from item 4 showed no statistical significance,
with only limited clinical relevance (data not shown).
DISCUSSION
Fig 1. Protocol for LLLT irradiation and placebo laser
application (A) used in G1 (B) and G2 (C).
hours, there was no significant difference between
G1 (n ⫽ 20) and G 2 (n ⫽ 25).
Pain was reported by fewer patients under age 19
years in G1 after 6 hours (n ⫽ 5), 30 hours (n ⫽ 9), and
The effect of single LLLT on the perception of pain
by patients having orthodontic treatment with fixed
appliances was investigated. Unlike in previous studies,
pain relief by single LLLT irradiation was evaluated
immediately after the placement of fixed appliances,
and many patients were studied prospectively.6,7
Reports on the effect of LLLT should be interpreted
with due attention to 2 factors that might influence the
outcome of the analysis: (1) the subjectiveness of pain
perception and the resultant dependence of the responses on the subject’s rating, and (2) the many
currently marketed laser systems, which differ both in
technical specifications and modes of application.
Among these systems are semiconductor lasers such as
the one we used, GaA1As lasers (wavelength, 809
nm),20 and helium-neon lasers,10 which are no longer
used in this indication. The nature of the laser beam
might also modify the pain-reducing effect of LLLT.
For wound healing, continuing weaves lasers were
374 Turhani et al
American Journal of Orthodontics and Dentofacial Orthopedics
September 2006
Fig 2. Modified 5-item questionnaire for evaluating pain at 6, 30, and 54 hours after actual or
placebo laser therapy.
shown to be superior to pulsed lasers.21 The biologic
effects of LLLT on nociception and its attenuation are
not yet fully understood.15-18,22
Pain perception varies considerably from patient to
patient. This biases the quantification of pain. Studies
on pain perception during initial orthodontic treatment
showed that patients become accustomed to the pain
within the first 3 to 5 days. Patients who have higher
perceptions of the severity of their malocclusions
seemed to adapt faster and have less pain during
orthodontic treatment.23
In a recent study, perceived pain was most pronounced in the first 3 days after multibanding.24 The
peak pain intensity was reached at 24 hours after a
latency of 2 hours. This agrees well with our data,
which showed that pain intensity peaked 6 hours after
multibanding, with less pain at 30 and 54 hours.
Studies on pain relief by LLLT are not confined to
fixed orthodontic treatment. Other studies have shown
pain relief by LLLT after surgical endodontics20 and in
patients with temporomandibular joint pain, trigeminal
neuralgia, myalgia, aphthaes, and hypersensitivity.25-27
Turhani et al 375
American Journal of Orthodontics and Dentofacial Orthopedics
Volume 130, Number 3
Table II. Distribution of pain and analgesia prevalence in G1 and G2 by different selection criteria, based on
responses to item 1
G1 (n ⫽ 38)
Patients with pain
Patients without pain
Patients under 19 years with pain
Patients under 19 years without pain
Patients over 18 years with pain
Patients over 18 years without pain
Male patients without pain
Male patients with pain
Female patients with pain
Female patients without pain
G2 (n ⫽ 38)
Fisher exact test (P ⬍.05)
6h
30 h
54 h
6h
30 h
54 h
14
24
5
9
9
15
5
8
9
16
22
16
9
5
13
11
10
3
12
13
20
18
5
9
15
9
9
4
11
14
29
9
17
3
12
6
13
4
16
5
33
5
18
2
15
3
15
2
18
3
25
13
14
6
11
7
10
7
15
6
6h
30 h
54 h
S
S
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
S, Significant; NS, not significant.
Table III.
Average pain intensity and site of peak pain sensation in G1 and G2, based on responses to item 3
G1 (n ⫽ 38)
6h
1.Qu,
1.Qu,
2.Qu,
2.Qu,
3.Qu,
3.Qu,
4.Qu,
4.Qu,
I
P/M
I
P/M
I
P/M
I
P/M
G2 (n ⫽ 38)
30 h
54 h
6h
30 h
54 h
Mean
SD
Mean
SD
Mean
SD
Mean
SD
Mean
SD
Mean
SD
2.85
2.92
2.5
2.46
2.82
3
3
3.25
0.9
1.24
1.17
1.45
1.08
1.23
0.94
1.04
2.62
2.47
2.5
2.82
2.71
2.55
2.64
2.82
1.16
1.28
1.28
1.24
1.27
1.37
1.39
1.25
2.3
2.25
2.24
2.27
2.17
2.5
2.36
2.25
1.3
1.06
1.15
1.28
0.94
1.07
1.03
1.04
2.2
1.94
2.53
2.64
2.55
1.86
2.5
2.6
1.01
0.8
0.83
1.08
1.04
1.07
1.24
0.55
2.55
1.7
2.83
2.22
2.33
2.4
2.08
2
1.01
0.92
0.79
1.26
1.3
1.27
1.32
1.16
1.81
1.42
2.13
2.09
1.43
1.86
1.75
1.67
0.98
0.51
0.92
1.14
0.79
0.69
0.89
0.52
Qu, Quadrant; I, incisors; P/M, premolars/molars.
Statistically, anxious patients and patients with
chronic pain from orthodontic treatment with fixed
appliances were found to experience more intense pain,
a phenomenon known from surgical studies.28
An interesting result of this study was that we could
observe a reduction in pain at 6 and 30 hours posttreatment with LLLT, but no differences were found in pain
intensity. We can only speculate about this result.
Obviously, patients in G1 most likely experienced no
reduction of subjectively perceived pain at 6 hours
posttreatment with LLLT compared with G2. To prove
this assumption, a quantitative survey of pretherapeutic
pain intensity would be necessary. Another approach
would be to evaluate the reduction of pain in a shorter
time span after treatment with LLLT before the 6-hour
time point.
Alternatively, the notion that LLLT has no effect on
pain intensity and pain prevalence must be considered;
perhaps the observed reduction in pain prevalence is
due to the Hawthorne effect29 or a true placebo effect.
Both possibilities cannot be entirely excluded. The
operator who applied the experimental and placebo
treatments could distinguish between G1 and G2. Although the patient was blinded to the difference, the
operator’s knowledge, transferred subconsciously to
the patient, might be enough to explain the difference
between the groups. However, the significance level of
P ⫽ .001 was a strong indicator for a statistically
significant and relevant correlation between LLLT and
pain reduction.
Additionally, a possible rebound effect after the
reduction of pain with LLLT cannot be excluded.
Possibly, the initial reduction of subjectively perceived
pain before 6 hours is followed by a subjectively
increased pain perception after the 6-hour time point.
With these statistical considerations, the use of a
visual analog scare for the evaluation of pain intensity
might be more significant.
Our results showed no differences in the location of
pain. This led to the conclusion that, on the 1 hand,
subjective pain perception is not related to the type of
malocclusion and the type of fixed appliance (brackets
376 Turhani et al
or molar bands) used. Otherwise, in both groups,
statistically significant increased pain intensity would
be expected. On the other hand, this study showed no
evidence that LLLT has a better analgesic effect on
certain areas of the teeth.
There is no consensus in the literature about potential differences in pain perception after multibanding
between preadolescents, adolescents, and adults.5,7,30,31
No conclusive evidence is available that 1 age group
perceives more or less pain than another.
In our study, a distinction was made between
patients under and over age 18 years to pinpoint a
differential effect, if any, of LLLT irradiation on pain
perception in the 2 age groups. The results suggested
that fewer patients under 18 reported pain at 6, 30, and
54 hours with LLLT than without it. No significant
differences were found between G1 and G2 in pain
intensity, and the responses to item 3 indicated no
specific trend for pain intensity.
CONCLUSIONS
LLLT irradiation clearly reduced the pain prevalence at 6 and 30 hours in this study. In the female
patients, the difference between G1 and G2 increased at
the 54-hour time point. Women appear to recover more
quickly than men according to subjective pain perception; no other study describes this phenomenon. However, conclusions about the effect of LLLT on pain
intensity cannot be drawn.
We thank Karoline Jokesch and Natascha Lukestik
for the laboratory work and Prof Dr Dieter Drescher,
Orthodontic Unit, Dental School, Heinrich-Heine University, Düsseldorf, Germany, for his help in designing
the study.
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