Lasers in Medical Science (2019) 34:281–286 https://doi.org/10.1007/s10103-018-2583-9 ORIGINAL ARTICLE Low-level laser therapy (830 nm) on orthodontic pain: blinded randomized clinical trial Isabela Parsekian Martins 1 & Renato Parsekian Martins 1 & Sergei Godeiro Fernandes Rabelo Caldas 2 & Ary dos Santos-Pinto 1 & Peter H. Buschang 3 & Hermes Pretel 4,5 Received: 16 February 2018 / Accepted: 5 July 2018 / Published online: 12 July 2018 # Springer-Verlag London Ltd., part of Springer Nature 2018 Abstract The objective of this research was to compare the effect single low-level laser therapy (LLLT) irradiation on pain perception in patients having fixed appliance treatment in the clinic of orthodontics. Sixty-two patients were recruited to participate in this randomized, double-blinded, placebo-controlled study. The patients were assigned to four groups: group I—laser on the right side; group II—placebo on the right side; group III—laser on the left side; group IV—placebo on the left. The laser or placebo was applied before separation, 24 and 48 h after separation of their first permanent molars in the lower arch. Just after the separation, the average of the pain for the placebo group was 1.6, significantly greater than the average of 1.1 registered for the laser group (p = 0.013). After 24 h and before the new irradiation, the values registered among the different groups did not show any differences. In relation to the gender, only after the first irradiation in placebo group, the female had a level of pain (0.1) significantly higher (p = 0.04) compared to male, and after 48 h, the group where the laser was applied had a difference (p = 0.04) among the gender with a value of lower pain for men (0.6) than for women (1.6). The laser irradiation to minimize the pain was only effective when applied immediately after treatment and separation. In general way, there were no differences between the genders, except after the first placebo group irradiation in which the female had a significantly higher level of pain compared to male and after 48 h. The pain cycle observed in this study had its peak in 24 h, both for laser’s and placebo’s group. Keywords LLLT . Laser therapy . Facial pain . Orthodontic Introduction Approximately 95% of patients report pain 24 h after their orthodontic appointments [1, 2]. The pain felt by patients can be characterized as a short-time acute pain, which lasts * Hermes Pretel hpretel@hotmail.com 1 Department of Orthodontics, Araraquara School of Dentistry, UNESP–Univ Estadual Paulista, Araraquara, São Paulo, Brazil 2 Department of Dentistry, UFRN, Natal, Rio Grande do Norte, Brazil 3 Department of Orthodontics, Baylor College of Dentistry, Dallas, TX, USA 4 Department of Restorative Dentistry, Araraquara School of Dentistry, UNESP–Univ Estadual Paulista, Araraquara, São Paulo, Brazil 5 Department of Restorative Dentistry, Araraquara School of Dentistry, São Paulo State University–UNESP, Rua Humaitá, 1680, Centro Araraquara, São Paulo 14801-903, Brazil up to 6–7 days and peaks around 24 h [1, 3–6]. Pain is important because it discourages people from seeking orthodontic treatment [7]. Pain can also cause patients to interrupt their treatments, even at the beginning of treatment [8, 9]. Different pharmacological and non-pharmacological methods have been proposed in order to enhance the control of orthodontic pain [6, 10–18]. Low-level laser therapy (LLLT) is one of the newer approaches proposed to control pain [19]. Lasers have been used in the medical and dental areas as an alternative to control pain [20–22]. They hold promise in controlling orthodontic pain because lasers do not have the side effect of the non-steroidal anti-inflammatory drugs. Lasers are thought to control pain by hyperpolarization of the nerve cell membrane, which increases the patient’s pain threshold, coupled with the lowest cell depolarization, among other factors [23]. Even though lasers hold potential for the treatment of pain, they remain controversial. There are only a few papers pertaining to the subject and their results. While two 282 Lasers Med Sci (2019) 34:281–286 Fig. 1 Laser application in the molar region papers describe lasers as ineffective tools for controlling pain [19, 24], most studies have reported reductions of pain [25–29]. Because there are several kinds of lasers with different dosages, wavelengths, and power, comparisons are difficult. The four studies that have used true placebos and a visual analog scale (VAS) [19, 28, 29] also remain controversial. The aim of this paper was to evaluate the ability of a lowlevel laser in diminishing orthodontic pain, using a doubleblind, split-mouth randomized clinical trial, using a VAS. Materials and methods This sample consisted of 62 patients (26 males and 36 females with an average age of 19.8 years) who were about to begin orthodontic treatment. All of them provided informed consent, which was approved by the University’s IRB (protocol number 23/10 FOAr-UNESP). In order to access pain, orthodontic separators were placed on the mesial and distal interproximal spaces of the first lower permanent molars. Since applying separator to both sides at the same time could confound patient’s sensitivity and confound the results, the separators were placed 1 week apart (Fig. 1 and Table 1). One week was needed in order to ensure that no underling pain existed from one separation placement to the other. In order to control for bias, patients were given one of four protocols, according to which treatment was given first and what side was treated first (Table 1). One group of patients had separators placed and the laser applied on their right lower first Table 1 Distribution of application of laser or placebo for bias control molars and 1 week later, separators were placed on their left side and placebo laser treatment was applied (protocol 1). In the second group, the placebo was applied first on the right side and the laser was applied on the left side 1 week later (protocol 2). In the third and fourth groups, the same respective procedures were performed as in the first two groups, but the left side was experimented first (protocols 3 and 4). The data from the four groups were merged and grouped as LASER or PLACEBO. The combination of initial and 1 week treatment time points was performed because there were no significant differences detected between sides over time (Table 2). Both the laser and the placebo treatments were applied by the same device, which was custom made for this research (Therpapy XT—DMC Equipamentos, São Carlos, SP, Brazil). The operator, by turning on or off a switch on the device, could apply either laser or only a light, and the sound that came out on the device was always the same. The laser and the placebo lights were red (guide light) and only the operator knew whether the laser or the placebo light had been applied. The laser used was a gallium-aluminum-arsenide diode, applied continuously, with a wavelength of 830 nm and the tip’s area is 0.03 cm2. The device was set to a power of 100 mW, producing 3 J of energy and a power density of 95 J/cm2. The application on each group was realized in different times (laser and placebo), because of the possible systemic effect that the laser might have done on the placebo’s group. The laser was applied perpendicular to and in contact with the gingiva at eight locations on either side of the separators: two mesial and two distal interproximally on the buccal side and two mesial and two distal of the lingual side. Each application took 30 s, producing a total of 24 J of energy per molar. Applications were performed immediately before and after the separators were placed, as well as 24 and 48 h after the separators were placed (Fig. 2). Pain was evaluated using a visual analog scale (VAS) at seven different time points once and 1 week later switching the side of treatment: 1 and 8—before the first application, 2 and 9—immediately after the application, 3 and 10—after the separators were placed, 4 and 11—24 h after separator placement, but before laser application, 5 and 12—24 h after separator and laser application, 6 and 13—48 h afterwards, before Protocol First experimented side (treatment) Second experimented side (treatment) 1 2 3 4 Right (laser) Right (placebo) Left (laser) Left (placebo) Left (placebo) Left (laser) Right (placebo) Right (laser) Lasers Med Sci (2019) 34:281–286 283 Table 2 VAS average scores and standard deviations for both groups and significance level Time period Placebo Laser p Initial Before treatment 0.0* (0.0) 0.0* (0.0) a 24 h After treatment After separators were placed Before treatment 0.1* (0.2) 1.6 (1.5) 2.6 (2.2) 0.0* (0.1) 1.1 (1.3) 2.2 (2.2) 0.182 0.013 0.133 After treatment 1.8 (2.0) 1.6 (1.8) 0.351 Before treatment After treatment 1.2 (1.6) 1.1 (1.4) 1.2 (1.8) 0.8 (1.4) 0.834 0.132 48 h respectively, with no statistically significant (p = 0.133) group differences. After the treatment, pain levels decreased to 1.8 in the placebo group and 1.6 in the laser group, again with no significant (p = 0.351) group differences (Table 2). After 48 h and before the last treatment, VAS scores dropped to 1.2 in both groups (p = 0.834). After treatment, VAS scores had a further drop to 1.1 in the placebo group and to 0.8 in the laser group, with no significant (p = 0.0132) difference between them (Table 2). *Insignificant values a p value could not be computed laser application, and 7 and 14—48 h after separator and laser application (Table 2). The VAS ranged from 0 to 10, with zero representing Bno pain at all^ and 10 representing Bthe greatest pain they ever felt.^ The data collected for laser and placebo sides were grouped and paired and the values were blinded to whom analyzed the data. The SPSS software v.16.0 (Chicago, IL, EUA) was used for statistical analysis. Since the data presented normality, a paired t test was used with significance (0.01) to compare the VAS values of the experimental sides to the placebo sides. Results Before and after the treatment was applied, the average VAS scores for both the laser and placebo groups were insignificant. After the separators were placed, the VAS scores were significantly (p = 0.013) higher in the placebo (1.6) group than in the laser (1.1) group (Table 3). After 24 h, and before the new treatment, the VAS scores averaged 2.6 and 2.2 for the placebo and laser groups, Discussion The laser was effective in diminishing pain, but only immediately after the separators were initially placed, suggesting a limited effect. The studies that have found that laser therapy decreases [25–31] or does not decrease [19, 24, 32] pain are difficult to directly compare with the present results. Among the four studies that used a VAS and true placebo controls, two detected significant laser effects on pain agreeing with our results [28, 29], while the remaining reported no treatment effect [19, 24, 32, 33]. The differences among the studies are probably due to the different power, energy, and wavelength settings used (Table 3) [19, 29]. One study evaluating different dosages reported no differences [19]. More research is required with different designs to determine the best protocol to use the laser. Since our application was before the placement of separators, maybe there is a preemptive effect of infrared lasers on pain that has yet to be confirmed. The bioelectric effect of laser modifying the membrane potential due to changes in the sodium and potassium channels may explain this effect. Hyperpolarization of the membrane hinders depolarization and thus increases the patient’s pain threshold, decreasing Fig. 2 Research design—laser application, insertion of retractors, and data collection **Considered up to the third day (dosage changed after that) *Descriptive statistics only Significant effect Significant effect No effect Yes Yes Yes Yes Yes Yes 30 mW/16 s 30 mW/15, 30, and 60 s Immediate Immediate through the 5th day 120 60 0.48 0.45, 0.9, and 1.8 – 830 830 CO2 Tortamano et al. Lim et al. Fujiyama et al. Al-Ga-As Al-Ga-As 4.8 0.45, 0.9, and 1.8 Significant effect Yes No 100 mW/10 and 20 s 2000 mW/30 s 8 1 or 2 809 Al-Ga-As Immediate, at 3, 7, and 14 days after each activation Immediate No Yes No Yes No Yes Yes Yes 6 mW/30 s 20 mW/10 s 75 mW/30 s 0.7 mW/30 s Immediate Immediate and at 3rd day Immediate Immediate, at 2nd and 3rd days 0.36 2 2.25 0.042 0.18 0.2 2.25 0.021 632.8 780 670 810 He-Ne Al-Ga-As In-Ga-Al-P Al-Ga-As Harazaki et al. Angelieri et al. Turhani et al. Doshi-Mehta and Bhad-Patil Youssef et al. No No 6 mW/30 s Immediate 0.36 0.18 632.8 Harazaki and Isshiki He-Ne VAS Split-mouth placebo Dosage Applications Total energy per tooth per day (J) Wavelength Energy per (nm) application (J) Laser type Paper Calculation were made for the analgesic effect only whenever the study has subsequent applications but not pain registration Table 3 Reduction of pain was found* Significant effect No effect Significant effect Significant effect** Lasers Med Sci (2019) 34:281–286 Result 284 sensitivity [11]. No research has moved towards that direction, and maybe after the most effective dosages are found, a research evaluating regimen of application might be necessary. The literature clearly shows a difference of laser parameters in the treatments for pain and orthodontic movement [10, 11, 13, 29, 33–35]. In the treatment of pain, both potency and higher doses have presented better results. On the other hand, when compared to the treatments of orthodontic movement, the parameters with better results are of potencies and lower doses with more frequency of applications. The bioelectric effect described above explains one of the main mechanisms of action of the laser in the control of pain [10, 11, 13, 35]. In orthodontic movement, the stimulations to cellular metabolism, angiogenesis, cell proliferation, and fibronectin are the events stimulated by the LLLT that explain the acceleration [29, 33, 34]. The cycle of pain observed in this study had its peak around 24 h, and the pain values decreased afterwards, in both groups. This cycle of pain is in agreement with the one reported by the literature [3–5, 10, 19], where after the second day, the pain slowly decreases and is minimal after the sixth day [5, 6, 11, 13]. Moreover, an interesting placebo effect was detected, since after the application of the laser or the placebo light, the VAS scores decreased. In our methodology, we included the comparative groups placebo, and laser treatment. This methodology truly evaluates the effect of 830 nm on controlling pain. The results showed a significant initial effect of the decrease of the pain of the laser group in comparison placebo. This fact may stimulate orthodontists to at least apply laser before insertion of the spacers. After the initial time, what may explain the non-difference between the laser group and placebo is the patient’s difficulty in reporting specifically where they feel the pain, since the sensation of pain can be radiated. In addition, each patient presents a different degree and tolerance for pain, making it difficult to homogenize the responses [24, 32, 34, 35]. However, we have been able to clinically present a pain control effect with the therapeutic laser in the preparation of the teeth to receive orthodontic treatment. 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