The effect of diode superpulsed low-level laser therapy on experimental orthodontic pain caused by elastomeric separators: a randomized controlled clinical trial Ida Marini, Maria Lavinia Bartolucci, Francesco Bortolotti, Giulio Innocenti, Maria Rosaria Gatto & Giulio Alessandri Bonetti Lasers in Medical Science ISSN 0268-8921 Volume 30 Number 1 Lasers Med Sci (2015) 30:35-41 DOI 10.1007/s10103-013-1345-y
1 23
Your article is protected by copyright and all rights are held exclusively by SpringerVerlag London. This e-offprint is for personal use only and shall not be self-archived in electronic repositories. If you wish to self-archive your article, please use the accepted manuscript version for posting on your own website. You may further deposit the accepted manuscript version in any repository, provided it is only made publicly available 12 months after official publication or later and provided acknowledgement is given to the original source of publication and a link is inserted to the published article on Springer's website. The link must be accompanied by the following text: "The final publication is available at link.springer.com”.
1 23
Author's personal copy Lasers Med Sci (2015) 30:35–41 DOI 10.1007/s10103-013-1345-y
ORIGINAL ARTICLE
The effect of diode superpulsed low-level laser therapy on experimental orthodontic pain caused by elastomeric separators: a randomized controlled clinical trial Ida Marini & Maria Lavinia Bartolucci & Francesco Bortolotti & Giulio Innocenti & Maria Rosaria Gatto & Giulio Alessandri Bonetti
Received: 25 October 2012 / Accepted: 1 May 2013 / Published online: 11 May 2013 # Springer-Verlag London 2013
Abstract The aim of this study was to evaluate the efficacy of diode superpulsed low-level laser therapy (SLLLT) in reducing experimentally induced orthodontic pain. Overall, 120 subjects (23.01±1.39 years) were enrolled for a clinical trial. Subjects were randomly assigned to upper (U, N=60) or lower (L, N=60) jaw groups. All subjects received 4 elastomeric separators mesial and distal to the upper (U group) or lower (L group) right first molar and bicuspids. Each subject of the U and L groups was randomly assigned to laser (Ul, N= 20 and Ll, N=20), placebo (Up, N=20 and Lp, N=20) or control (Uc, N=20 and Lc, N=20) sub-groups. Subjects in laser groups received a single GaAs diode SLLLT application (910 nm, 160 mW, beam diameter of 8 mm, applied for 340 s) immediately after placing orthodontic separators. Placebo groups received a simulated SLLLT and controls did not receive any therapy. All participants compiled a survey on pain duration and a 100-mm visual analogue scale immediately after the separators placement and after 12, 24, 36, 48, 72, and 96 h. Pain intensity of laser groups was significantly lower compared to placebo and control groups (p=0.0001). In the laser group, 70 % of subjects felt pain, while in the placebo and control groups all subjects felt pain (p=0.0001). The end of pain occurred earlier in laser compared to placebo and control groups (p=0.021). A single-diode SLLLT application appeared to be effective in reducing the intensity and duration I. Marini : G. Innocenti : M. R. Gatto : G. Alessandri Bonetti (*) Department of Biomedical Sciences, Section of Orthodontics, University of Bologna, Italy, via san Vitale, 59 40125 Bologna, Italy e-mail:
[email protected] M. L. Bartolucci : F. Bortolotti Department of Neurosciences, Section of Orthodontics, University of Naples “Federico II”, Italy, via Pansini, 5 80100 Naples, Italy
of experimentally induced orthodontic pain and could be used in daily orthodontic practice. Keywords Superpulsed laser . LLLT . Orthodontics . Orthodontic pain . Orthodontic separators
Introduction Orthodontic pain represents an important clinical issue, often underestimated by the clinicians but is considered extremely important by patients. The concern about pain can induce patients to forego orthodontic treatment and the experience of pain during initial stage of therapy can negatively influence patients’ cooperation and cause treatment interruptions [1–3]. The pain sensation is a subjective experience dependent upon physical and psychological factors such as age, gender, stress, present emotional state, cultural differences, previous pain experiences, and the magnitude of orthodontic force applied [4]. According to the literature, pain starts 2 h after the application of orthodontic fixed appliance, raises over the next 24– 36 h, starts to decrease on day 3, and disappears within 6– 7 days [5, 6]. This nociceptive response is caused by compression of periodontal ligament that induces the release of algogens (i.e., prostaglandins, histamine, bradykinin, serotonin, and substance P), which lead to delayed hyperalgesia [4, 7, 8]. The non steroidal anti-inflammatory drugs (NSAIDs) are commonly administered to interrupt the algogens release and reduce pain perception [9]; however, there is some evidence that NSAIDs reduce the rate of tooth movement [10]. The analgesic efficacy of low-level laser therapy (LLLT) has been investigated and several mechanisms for pain relieving have been proposed, including the gate theory, the
Author's personal copy 36
modulation of endorphin production, the anti-inflammatory effect, and the direct inhibition of neural activity [11]. Many studies investigated the efficacy of diode LLLT also for orthodontic pain relief testing a continuous wave LLLT; some authors concluded that LLLT did not significantly reduce orthodontic pain [12, 13], while other studies found that it is effective for orthodontic pain relief [14–18]. Furthermore, a recent literature review reports that continuous wave LLLT can bring about an increase in tissue temperature and suggests that this adverse effect could be avoided by using a pulsed wave LLLT [19]. The principal characteristic of pulsed light is represented by pulse on and off periods. This allows shorter pulses and LLLT therapy with higher peaks of power compared to those allowed in continuous wave mode lasers as well as reaching a deeper penetration depth, and avoiding the unpleasant effects of continuous wave (such as thermal damage) [19]. To date, the effect of a pulsed-wave diode laser for orthodontic pain relief has not been investigated; in addition, a recent meta-analysis indicates that well-designed randomized controlled trials are needed [20]. The aim of the present study is to evaluate the efficacy of diode superpulsed LLLT (SLLLT) in reducing experimentally induced orthodontic pain. The null hypothesis The null hypothesis was that no difference existed between SLLLT and placebo in reducing experimental orthodontic pain caused by elastomeric orthodontic separators.
Subjects and methods A sample size of at least 18 subjects for each group was set with a precision of 0.05 and a power of 95 %, using as standard deviation estimate the length of the visual analogue scale (VAS) scale. One hundred fifty-eight students of the University of Bologna were recruited for this study. The inclusion criteria were age from 20 to 25 years and the presence of a complete dentition excluding third molars. Exclusion criteria were pregnant subjects or patients in menstrual and perimenstrual phase, the presence of systemic or oral diseases, orofacial pain, migraine, orthodontic treatment in the last 5 years, diastema and crowding in the first and sixth sextant (bicuspids and molars of right upper and lower arches). Conditions that could alter nociception were excluded, such as concurrent and previous (a month prior to the investigation) use of anti-inflammatory and analgesic drugs, antidepressants, anticonvulsants, and oral contraceptives. An anamnestic questionnaire was administered to all subjects and a clinical examination was performed to verify the fulfillment
Lasers Med Sci (2015) 30:35–41
of the inclusion and exclusion criteria. The study protocol was explained to all participants. One hundred twenty subjects (64 males and 56 females, mean age 23.01±1.39 years) were enrolled for this study. All participants signed an informed consent. A clinical trial with parallel branches was conducted in the first 4 months of 2012 and each subject was randomly assigned to upper (U, 60 subjects) or lower (L, 60 subjects) jaw group by using a coin flip. An investigator (G.I.) placed four elastomeric separators using dental floss for all participants to create an experimental orthodontic pain. Subjects of U group received the separators mesial and distal to the upper right first molar as well as first and second bicuspids (Fig. 1); subjects of the L group received the separators mesial and distal to the lower right first molar as well as first and second bicuspids. Each subject of the U and L groups was randomly assigned to one of the following three groups: laser group (Ul, N=20; Ll, N=20), placebo group (Up, N=20; Lp, N=20) and control group (Uc, N=20; Lc, N=20). The assignment was carried out by using a block randomization (block size=3); each subject received an envelope containing the number of the group he was assigned to. The randomization plan was carried out by a biostatistician (M.R.G.) who was blinded to the analysis. Two observers respectively enrolled subjects (M.L.B.) and assigned them to the groups (F.B.). Table 1 and Fig. 2 describe the sample and study design. Laser irradiation Subjects of groups Ul and Ll received a SLLLT application that started immediately after placing orthodontic separators. The device that was used was a GaAs diode laser unit (Lumix 2 HFPL, Fisioline, Verduno, Italy), operating with a superpulsed wave and a wavelength of 910 nm. The average radiant power was 160 mW and the beam area and beam shape were 0.5 cm2 and 8 mm, respectively. The exposure duration was of 340 s, with a total power applied of 54.4 J, with a frequency of 30 kHz and a duty cycle of 80 % (4 s of active pulsation and 1 s of quench period). The laser probe was applied on the cervical third of buccal and lingual
Fig. 1 Elastomeric separators placed in the right maxillary posterior region
Author's personal copy Lasers Med Sci (2015) 30:35–41
37
Table 1 Sample description Mean Age Gender Mean Age (SD) Gender
Group U (N=60)
Group L (N=60)
23.03±1.43 29 M; 31 F Ul (N=20) 23.1±1.48 11 M; 9 F
22.98±1.37 35 M; 25 F Ll (N=20) 23.3±1.56 12 M; 8 F
gingival covering of each root. When the laser unit was operating, it emitted a sound every 2 s. Placebo groups received a simulated SLLLT application in which the laser unit did not work and the probe emitted only a continuous red light without making any sound. The wavelength and power of the red light were 650 nm and 3 mW, respectively. In order to guarantee the blindness of both the operator and patient, they wore headphones not to hear the sound emitted and the laser probe was delivered to the operator (I.M.) by another experimenter (G.A.B.). Control group subjects did not receive any therapy. According to bio-safety rules, the patients and the operator wore safety
Fig. 2 Study design description
Up (N=20) 22.95±1.36 8 M; 12 F
Uc (N=20) 23.05±1.5 10 M; 10 F
Lp (N=20) 23±1.08 13 M; 7 F
Lc (N=20) 22.65±1.42 10 M; 10 F
glasses during laser irradiation and simulated laser application (placebo groups). All participants were instructed to report their spontaneous pain perception compiling a 100-mm VAS [21] immediately after the placement of separators and after 12, 24, 36, 48, 72, and 96 h. Furthermore, all subjects were instructed to complete a survey at home over the next 4 days and they were told not to take any medicine. In the questionnaire, which was the modified version of those used by Harazaki [22] and Tortamano [14], subjects were requested to indicate if they felt pain or not during the investigation (occurrence of pain), when they started to feel pain (initial pain), the day
Author's personal copy 38
Lasers Med Sci (2015) 30:35–41
Fig. 3 VAS median values trend during the study. The differences in VAS values were statistically significant among groups at T12, T24, T36, T48, T72, and T96 (p=0.0001)
in which they felt the most serious pain (most painful day), and the day in which the pain disappeared (end of pain). After 4 days, elastomeric separators were removed and questionnaires collected. The biostatistician, operator, and patients who performed the study were blinded.
used to compare each couple of treatments. The α level was a priori set at 0.05.
Statistical analysis
No significant differences in VAS values were observed between the arches for different treatment groups (Ul and Ll, Up and Lp, Uc and Lc). Consequently, the results of upper and lower arches were combined according to the treatment and the analysis was carried out on three groups: laser group (L), placebo group (P), and control group (C). No significant differences in VAS values were observed at baseline among the three groups: this guaranteed the comparability between groups. There were statistically significant differences between groups at T12, T24, T36, T48, T72, and T96 (p=0.0001); the mean VAS values of the laser groups were significantly lower when compared with those of placebo and control groups (Fig. 3). The interquartile ranges of placebo and control groups were much larger than those of laser group, indicating a high variability (from 8 to 54 VAS units). Therefore, the null hypothesis for this study was fully rejected.
Shapiro–Wilk test denoted that VAS values at different times deviated from normality and therefore, comparisons between the arches for each treatment (Ul and Ll, Up and Lp, Uc and Lc) were performed using the Mann–Whitney U test. The pain perception at each of the seven time intervals (immediately after the insertion, after 12, 24, 36, 48, 72, and 96 h) in the experimental, placebo and control groups have been described as median and interquartile range and compared using the Kruskal–Wallis non parametric analysis of variance. Bivariate analysis was carried out on occurrence of pain and χ2 was performed to test the association with the treatments. The ANOVA test was used to analyze the initial pain, most painful day and the end of pain, with treatment as a fixed factor and arch as a random factor; when differences were significant, Bonferroni test was
Results
Table 2 Questionnaire outcomes reported as number of patients Occurrence of pain
Initial pain
Group
NA
Immediately
12 h
Day 1
Day 2
Day 2
Day 3
ND
12(30 %) 13(32.5 %) 5(12.5 %)
13(32.5 %) 14(35 %) 6(15 %)
15(37.5 %) 26(65 %) 34(85 %)
7(17.5 %) 3(7.5 %) 1(2.5 %)
9(22.5 %) 11(27.5 %) 6(15 %)
12(30 %) 26(65 %) 33(82.5 %)
NA never appeared, 12h after 12 h, ND never disappeared
Author's personal copy Lasers Med Sci (2015) 30:35–41
39
Table 3 ANOVA results for questionnaire outcomes Variable
Factor
F value
p value
Initial pain
Treatment Arch Treatment Arch Treatment Arch
2.228 0.189 4.038 0.197 46.778 0.250
0.310 0.706 0.198 0.701 0.021a 0.667
Most painful day End of pain
a
Statistically significant
The outcomes of the questionnaire are reported in Table 2. Concerning the occurrence of pain, it emerged that 30 % of subjects in the laser group did not feel pain, while in the placebo and control groups all subjects felt pain (χ2 = 26.667, p=0.0001). ANOVA results for questionnaire outcomes (Table 3) indicated the initial pain and the most painful day were not significantly different neither among the groups nor between the arches, while the end of pain was significantly different among the groups (p=0.021). The pain never disappeared in 10 % of subjects in laser group, in 70 % of the placebo group, and in 80 % of subjects in the control group. The Bonferroni test showed that for this variable the differences were significant between laser and placebo as well as between laser and control, but not between placebo and control (Table 4).
Discussion Pain experience caused by tooth movement represents an important concern for patients. It can induce them to forego orthodontic treatment and can negatively influence their cooperation [1–3]. The efficacy of diode LLLT in reducing orthodontic pain [12–18] is still controversial and diode SLLLT has not been previously tested for this purpose. The present study used superpulsed wave laser since pulsed light could be safely used at a higher peak of power compared to continuous wave lasers and a pulsed laser irradiation did not cause an increase in tissue temperature. Although diode laser has a low upper state life time, the super-pulse permits reaching high peaks of power by means of the generation of extremely short pulses (in the range of nanoseconds) and of the modulation of the electric pumping system; this aspect allows to operate with a current five to Table 4 Differences between groups about “end of pain” (Bonferroni test)
a
Statistically significant
ten times higher than continuous wave. The laser penetration through tissues is directly related to its wavelength, that achieves optimal results in the optical window of 500 to 1,200 nm [23]; taking this data into account, the present study used 910 nm wavelength. To this regard, even if the parameter that mainly influences the penetration depth is the wavelength, it is important to underline that the pulsation permits more deep penetration than continuous wave laser with the same average power as superpulsed laser can reach high peaks of power [19, 24]. A biological explanation of the improved efficacy of pulsed light depends on some biological processes that have a time scale of few milliseconds: there is evidence that ion channels are involved in the subcellular effects of LLLT and the time scale for opening and closing the ion channels is in the range of few milliseconds [11, 25, 26]. In addition, LLLT could act on a cellular level photodissociating nitric oxide from a protein binding site [27]; if the light is pulsed, multiple photodissociation events can occur, while in continuous wave mode, the number of dissociations may be much smaller [19]. The present clinical trial demonstrated that Gab–As diode SLLLT is effective in reducing the intensity of orthodontic pain, being VAS values of the laser group significantly lower than those of placebo and control groups at each time interval of the study. The absence of significant differences in VAS values at baseline among the groups guarantees the comparability. It was interesting to observe that in the laser group, VAS values were close to 0, as shown in Fig. 3, and the maximum VAS value was 3.5. Furthermore, there was a significant difference in the occurrence of pain between subjects treated with SLLLT, placebo, and control groups. Besides, the end of pain occurred significantly earlier in laser group when compared with placebo and control groups (Tables 3 and 4). To this regard, analyzing mean VAS values, it was remarkable that at day 4 placebo and control groups reported to still have pain, while in laser group pain was not registered any more (Fig. 3). These data confirm the efficacy of SLLLT in reducing orthodontic pain duration and that more patients treated with SLLLT did not feel any pain in comparison with the placebo and control groups. The average pain scores for the present study were higher compared to recent studies with similar set-up [17, 18, 28]. This could be due to the differences among study populations as well as using four elastomeric separators instead of two in each quadrant. Since elastomeric separators were commonly used in research
Variable
Comparison
End of pain
Laser—placebo Laser—control Placebo—control
Mean difference (days) −2.10 −2.00 0.10
SE
p
0.294 0.294 0.294
0.0001a 0.0001a 0.025
Author's personal copy 40
protocols to induce orthodontic pain [12, 13, 18, 29], in the present study, four separators were applied to provoke an experimental orthodontic pain as similar as possible to the pain caused by the placement of the first archwire in a fixed appliance. The registrations were carried out for 4 days since the aim of the present study was to verify the efficacy of SLLLT in reducing the intensity of experimental orthodontic pain, that has been shown to reach its peak after 24–36 h after the application of an orthodontic force [30]. Orthodontic tooth movement is due to the periodontal ligament inflammation mechanisms [31] that induce algogens release (i.e., prostaglandins, histamine, bradykinin, serotonin, and substance P) and lead to delayed hyperalgesia [4, 7, 8]. A recent meta-analysis concluded that even if the administration of NSAIDs for orthodontic pain control was advocated, their efficacy was debatable as compared with placebo group, no significant pain reduction was present at 24 h after the application of the orthodontic force, when pain reached its maximum value [32]. In addition, it has been shown that NSAIDs inhibit the action of cyclooxygenase (COX) and the production of prostaglandins, resulting in a depletion of osteoclasts and reduction of tooth movement [10]. Paracetamol (acetaminophen) however did not influence the rate of orthodontic tooth movement since it lacked anti-inflammatory properties [10], but a recent study showed that it was not more effective than placebo in reducing orthodontic pain [9]. Furthermore, the COX-1 and COX-2 inhibition could have important systemic side effects, such as gastrointestinal, renal and hepatic toxicity as well as increased risk of cardiovascular disease [33, 34]. Since laser therapy lacks all these side effects, it would be preferable to use it as a substitute for NSAIDs for orthodontic pain control in daily clinical practice. Since literature does not provide data concerning SLLLT for orthodontic pain relief, the irradiation protocol used in the present study was set following the instructions of the manufacturer. With the laser parameters used in this study, the duration of SLLLT application for pain relief on five teeth was 5 min and 40 s. In order to avoid excessive discomfort to the patient, it is preferable to bond upper and lower jaw at separate sessions. Since the presented SLLLT protocol would have a duration of about 15 min if applied on one bonded arch, it could be clinically applicable and acceptable, considering its efficacy in reducing orthodontic pain intensity and duration. SLLLT should be used in the most painful phases of fixed orthodontic treatment: at the beginning of the therapy and at every archwire replacement. It was interesting to notice the considerable reduction of VAS pain values registered in placebo group compared with controls. From our point of view, this is remarkable, considering the importance of the psychological aspect of pain
Lasers Med Sci (2015) 30:35–41
perception and the entity of psychological contribution to the laser group VAS values. The use of the red light was important as it guaranteed the blindness of the patient and the operator. Nevertheless, a possible influence of the red light in placebo group can be hypothesized since it expresses a power of 3 mW that can produce pain reduction after an irradiation of 340 s. However, we assume the remarkable difference of power between laser and placebo groups (average 160 versus 3 mW) ensures the reliability of the results for the present study. Considering the present findings, it may be concluded that diode SLLLT can be used in the clinical practice for pain relief. Further studies could investigate the possibility to find different laser parameters to further reduce the application time while maintaining the efficacy of laser.
Conclusions The present study showed the effectiveness of a single Ga– As diode SLLLT application, in reducing the intensity and duration of experimental orthodontic pain caused by elastomeric separators. The clinical relevance of the present results suggests the possibility of using this SLLLT protocol in daily orthodontic practice.
References 1. Oliver RG, Knapman YM (1985) Attitudes to orthodontic treatment. Br J Orthod 12:179–88 2. Brown DF, Moerenhout RG (1991) The pain experience and psychological adjustment to orthodontic treatment of preadolescents, adolescents, and adults. Am J Orthod Dentofacial Orthop 100:349–56 3. Bergius M, Broberg AG, Hakeberg M, Berggren U (2008) Prediction of prolonged pain experiences during orthodontic treatment. Am J Orthod Dentofacial Orthop 133:339.e1–8 4. Krishnan V (2007) Orthodontic pain: from causes to management—a review. Eur J Orthod 29:170–9 5. Erdinç AM, Dinçer B (2004) Perception of pain during orthodontic treatment with fixed appliances. Eur J Orthod 26:79–85 6. Jones M, Chan C (1992) The pain and discomfort experienced during orthodontic treatment: a randomized controlled clinical trial of two initial aligning arch wires. Am J Orthod Dentofacial Orthop 102:373–81 7. Alhashimi N, Frithiof L, Bridvik P, Bakhiet M (2001) Orthodontic tooth movement and de novo synthesis of proinflammatory cytokines. Am J Orthod Dentofacial Orthop 119:307–12 8. Walker JB, Buring SM (2001) NSAID impairment of orthodontic tooth movement. Ann Pharmacother 35:113–5 9. Patel S, McGorray SP, Yezierski R, Fillingim R, Logan H, Wheeler TT (2011) Effects of analgesics on orthodontic pain. Am J Orthod Dentofac Orthop 139:e53–8 10. Bartzela T, Türp JC, Motschall E, Maltha JC (2009) Medication effects on the rate of orthodontic tooth movement: a systematic literature review. Am J Orthod Dentofac Orthop 135:16–26
Author's personal copy Lasers Med Sci (2015) 30:35–41 11. Chow RT, David MA, Armati PJ (2007) 830 nm laser irradiation induces varicosity formation, reduces mitochondrial membrane potential and blocks fast axonal flow in small and medium diameter rat dorsal root ganglion neurons: implications for the analgesic effects of 830 nm laser. J Peripher Nerv Syst 12:28–39 12. Esper MA, Nicolau RA, Arisawa EA (2011) The effect of two phototherapy protocols on pain control in orthodontic procedure–a preliminary clinical study. Lasers Med Sci 26:657–63 13. Lim HM, Lew KK, Tay DK (1995) A clinical investigation of the efficacy of low level laser therapy in reducing orthodontic postadjustment pain. Am J Orthod Dentofac Orthop 108:614–22 14. Tortamano A, Lenzi DC, Haddad AC, Bottino MC, Dominguez GC, Vigorito JW (2009) Low-level laser therapy for pain caused by placement of the first orthodontic archwire: a randomized clinical trial. Am J Orthod Dentofac Orthop 136:662–7 15. Turhani D, Scheriau M, Kapral D, Benesch T, Jonke E, Bantleon HP (2006) Pain relief by single low-level laser irradiation in orthodontic patients undergoing fixed appliance therapy. Am J Orthod Dentofac Orthop 130:371–7 16. Doshi-Mehta G, Bhad-Patil W (2012) Efficacy of low-intensity laser therapy in reducing treatment time and orthodontic pain: a clinical investigation. Am J Orthod Dentofac Orthop 141:289–97 17. Artés Ribas M, Arnabat-Dominguez J, Puigdollers A (2013) Analgesic effect of a low-level laser therapy (830 nm) in early orthodontic treatment. Lasers Med Sci 28:335–41 18. Eslamian L, Borzabadi-Farahani A, Hassanzadeh-Azhiri A, Badiee MR, Fekrazad R. (2012) The effect of 810-nm low-level laser therapy on pain caused by orthodontic elastomeric separators. Lasers Med Sci. doi:10.1007/s10103-012-1258-1 19. Hashmi JT, Huang Y, Sharma SK, Kurup DB, Taboada LD, Carroll JD, Hamblin MR (2010) Effect of pulsing in low-level light therapy. Lasers Surg Med 466:450–66 20. He WL, Li CJ, Liu ZP, Sun JF, Hu ZA, Yin X, Zou SJ (2012) Efficacy of low-level laser therapy in the management of orthodontic pain: a systematic review and meta-analysis. Lasers Med Sci. doi:10.1007/s10103-012-1196-y 21. Huskisson E (1974) Measurement of pain. Lancet 304:1127–31
41 22. Harazaki M, Isshiki Y (1997) Soft laser irradiation effects on pain reduction in orthodontic treatment. Bull Tokyo Dent Coll 38:291–5 23. Harris DM (1991) Biomolecular mechanisms of laser biostimulation. J Clin Laser Med Surg 8:277–80 24. Marini I, Gatto MR, Bonetti GA (2010) Effects of superpulsed low-level laser therapy on temporomandibular joint pain. Clin J Pain 26:611–6 25. Karu TI (2008) Mitochondrial signaling in mammalian cells activated by red and near-IR radiation. Photochem Photobiol 84:1091– 9 26. Karu TI, Pyatibrat LV, Afanasyeva NI (2004) A novel mitochondrial signaling pathway activated by visible-to-near infrared radiation. Photochem Photobiol 80:366–72 27. Lane N (2006) Cell biology: power games. Nature 443:901–903 28. Eslamian L, Borzabadi-Farahani A, Edini HZ, Badiee MR, Lynch E, Mortazavi A (2012) The analgesic effect of benzocaine mucoadhesive patches on orthodontic pain caused by elastomeric separators, a preliminary study. Acta Odontol Scand. doi:10.3109/ 00016357.2012.757358 29. Michelotti A, Farella M, Martina R (1999) Sensory and motor changes of the human jaw muscles during induced orthodontic pain. Eur J Orthod 21:397–404 30. Bondemark L, Fredriksson K, Ilros S (2004) Separation effect and perception of pain and discomfort from two types of orthodontic separators. World J Orthod 5:172–6 31. Krishnan V, Davidovitch Z (2006) Cellular, molecular, and tissuelevel reactions to orthodontic force. Am J Orthod Dentofacial Orthop 129:e1–32 32. Angelopoulou MV, Vlachou V, Halazonetis DJ (2012) Pharmacological management of pain during orthodontic treatment: a metaanalysis. Orthod Craniofac Res 15:71–83 33. Süleyman H, Demircan B, Karagöz Y (2007) Anti-inflammatory and side effects of cyclooxygenase inhibitors. Pharmacol Rep 59:247–58 34. Farkouh ME, Greenberg BP (2009) An evidence-based review of the cardiovascular risks of nonsteroidal anti-inflammatory drugs. Am J Cardiol 103:1227–37
