Low-Level Laser Therapy: A Noninvasive Method of Relieving Postactivation Orthodontic Pain-A Randomized Controlled Clinical Trial.

INTRODUCTION: Pain is an unavoidable squeal of orthodontic treatment and it is known to decrease patient compliance and eventually affects treatment results. Numerous methods are available in literature to manage orthodontic pain after activation but they have their own limitations. This has led to exploring further options for management of pain. AIM: The aim of this study was to evaluate the effectiveness of low-level laser therapy (LLLT) in alleviating orthodontic pain after activation.
MATERIALS AND METHODS: 20 subjects were randomly divided into an experimental and a control group. Each participant was given a retraction force of 200 gm/cm2/side. Subjects in the experimental group were exposed to low-level laser light at 980 nm and those in the control group were exposed to red LED light as placebo. The pain perceived after 0 hour, 1 hour, 3 hours, 48 hours, and 1 week of activation was recorded by patient using Visual Analog Scale. Statistical analysis was done using Mann-Whitney test.
RESULTS: Results of the study showed that pain experienced by the subjects after orthodontic activation was higher in experimental group at T0 than in placebo group. At T1, T2, T4, and T5, the pain experienced by the subjects was less in the experimental group compared to the placebo group. Pain experienced by the subjects in the experimental group at T3 was significantly less as compared to those in the placebo group.
CONCLUSION: A single dose of LLLT at 980nm, 2.5 W/cm2, and 600 J is effective in relieving orthodontic pain after activation.

INTRODUCTION

Pain can be defined as an unpleasant sensory or emotional stimuli associated with actual or potential tissue damage.[1] Pain is experienced by a patient when force is applied on tooth; this alters blood supply and an inflammatory response is initiated in periodontal tissues, which releases mediators such as leukotrienes and prostaglandins that produce hyperalgesia. This noxious stimulus is known to increase discomfort and reduce patient compliance.[2] Treatment strategies available in the literature to manage orthodontic pain include use of pharmacological agents such as nonsteroidal anti-inflammatory drugs (NSAIDs) imparting vibratory stimuli, but they have their own limitation. NSAIDs are associated with decrease in the rate of tooth movement as they inhibit prostaglandin synthesis. Effects of other methods used are limited as they have poor tolerance, unclear effects, and scanty evidence in their favor of efficiency of action.[3]

Low-level laser therapy (LLLT) is a noninvasive technique that stimulates the host cells. The photobiomodulatory effect of this technique is shown to reduce the severity of pain perceived after orthodontic activation with minimum side effects.[4] Literature supporting these claims are plenty, but in most of the studies, parameters used for laser application and time of exposure were not standardized. The aim of this study was to clinically evaluate the efficiency of LLLT in relieving pain after orthodontic appliance activation.

MATERIALS AND METHODS

The sample comprised 20 patients (16 girls and 4 boys) of age between 18 to 24 years with a mean age of 21.3 years who required bilateral canine retraction. Patients with chronic systemic diseases were excluded. All the subjects were treated with preadjusted edgewise appliance of standard 0.022 mclaughlin, bennett and trevisi prescriptions and had a passive 0.019 × 0.025 stainless-steel archwires as working wire. To each group, a retraction force of 200 g/cm2 per side was applied to maxillary right and left quadrants using type 1 active tiebacks. Force was measured using a Dontrix gauge [Figure 1]. Participants were single blinded and were randomly allocated into two groups.

Figure 1

Dontrix gauge measuring 200 gm/cm2

The first group (G1) was experimental group in which participants were exposed to a single dose of LLLT at 980nm, 2.5 W/cm2, and 600 J for 30 seconds using a diode laser on labial and palatal sides of each tooth in the arch [Figure 2]. The second group (G2) was placebo group in which participants were exposed to red LED light for 30 seconds on labial and palatal sides of each tooth in the arch [Figure 3]. This red LED light mimicked laser, but tissues were not exposed so no molecular changes would occur.

Figure 2

Diode laser unit with photobiomodulation handpiece

Figure 3

Application of low level laser therapy on buccal and palatal mucosa

Patients were asked to rate intensity of pain experienced by them on a Visual Analog Scale (VAS) at six time intervals: immediately after activation (T0), 1 hour after activation (T1), 3 hours after activation (T2), 24 hours after activation (T3), 48 hours after activation (T4), and 7 days after activation (T5). The scores on VAS were from “0 to 10,” where a score of “0” indicated minimum pain and “10” indicated maximum pain. The values were tabulated and were sent for statistical analysis.

Statistical analysis

Statistical analysis was performed using SPSS software, version 10.5, with a 5% level of significance. P value was computed using Mann–Whitney test.

RESULTS

Results of the study show that the mean pain experienced by subjects after orthodontic activation was higher in the experimental group at T0 than the placebo group. Table 1 and Graph 1 show the mean difference in pain experienced by subjects at different time intervals. At T1, T2, T4, and T5, the mean pain experienced by subjects was less in patients exposed to LLLT than the placebo group, but the values were not statistically significant. At T0, higher mean pain was recorded in the experimental group as compared to the placebo group, but the difference between them was not statistically significant (P > 0.05). Intensity of pain experienced by subjects in the experimental group at T3 was less as compared to the placebo group and the difference was statistically significant P < 0.05. At T5, the experimental group experienced no pain but the placebo group experienced mild pain. This value was not statistically significant but was clinically significant.

Table 1

Mean VAS score between G1 and G2 at different time intervals

Time interval	Group	n	Mean VAS score	Standard deviation	Standard error of mean	Mean difference	z	P Value
T0	Study group (G1)	10	4.90	1.60	0.50	0.200	−0.311	0.756
	Placebo group (G2)	10	4.70	1.49	0.47
T1	Study group (G1)	10	4.20	1.75	0.55	0.100	−0.579	0.563
	Placebo group (G2)	10	4.70	1.57	0.50
T2	Study group (G1)	10	3.10	1.65	0.52	0.000	−0.354	0.723
	Placebo group (G2)	10	3.40	1.27	0.40
T3	Study group (G1)	10	1.20	1.17	0.37	−1.30	−2.840	0.048
	Placebo group (G2)	10	2.50	0.97	0.31
T4	Study group(G1)	10	0.60	0.84	0.27	−0.600	−1.370	0.171
	Placebo group (G2)	10	1.20	1.03	0.33
T5	Study group (G1)	10	0.00	0.00	0.00	−0.100	−1.000	0.317
	Placebo group (G2)	10	0.10	0.32	0.10

VAS = visual analog scale

Graph 1

Mean pain between G1 and G2 at different time intervals

DISCUSSION

LLLT uses photobiomodulation to stimulate the host tissues that produce biological effects. This does not cause any raise in temperature of the tissue as compared to conventional lasers so it is relatively safer.[5] Photobiomodulatory effects reduce the inflammatory response and provide relief from pain.[6] Light of this wavelength is absorbed by nocioreceptors and produces an inhibitory effect on Aδ fibers and C fibers that tend to decrease the conduction velocity and reduce the magnitude of pain.[78]. The peak pain was experienced immediately after activation (T0) and 1 hour after activation (T1). There was no change in pain perception between both the groups at T1, but at T2 the study group was less susceptible to pain as compared to T2. Results of this study were different from those of the study conducted by Sobouti et al.[9] as they used different irradiation parameter of 632.8 nm and energy of 7.2 J/cm2 for exposing the tissue and observed pain perception after 24, 48, 64, and 168 hours of activation. It was observed that the pain subsided over time from the time of activation and was minimal at 1 week after activation. Their study subjects did not experience pain at 1 week after activation in both test and placebo groups.[9] On the other hand, in our study a small amount of pain was experienced even after 1 week of activation in the placebo group but no pain was experienced in the study group.

Domínguez and Velásquez[10] conducted a study that showed the peak pain was observed 24 hours after activation and subsequently the pain reduced. The irradiation values of 830 nm, 100 mW at 80 J/cm2 for 22 seconds were used, and the results showed that in the study group the pain perception was less as compared to the placebo group with the maximum pain experienced during 24 hours after activation.[1011] To overcome these flaws, the current study projected a randomized clinical model with standardized parameters to check the effectiveness of LLLT to relieve orthodontic pain after activation.

CONCLUSION

The study concluded that a single dose of LLLT at 980 nm, 2.5 W/cm2, and 600 J was capable of relieving post activation orthodontic pain. It was most effective in relieving pain experienced 24 hours after activation as it produced a statistically significant difference in the pain experienced between both the groups.

The pain experienced at T1, T2, T3, and T4 was less in the experimental group as compared to the placebo group except at T0, which was immediately after activation. Further studies with larger sample size and mixed age group of population are needed to quantify the findings of this study for a larger population.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.