Introduction

One of the major challenges to a successful orthodontic treatment especially while dealing with crowding cases type of malocclusion is the prolonged duration of treatment.1 Prolonged orthodontic management prods a lot of patients, exclusively grown-ups, to either evade treatment or to pursue diminutive alternate elucidations with conceded consequences. Hence there is a continuous search for those types of treatment modalities which without altering the quality outcome of the said intervention are able to render the same in a shorter time span. 2

Orthodontists are trying since long to develop certain approach strategies that will actually assist to increase the rate at which the tooth movement takes place during orthodontic treatment. 2, 3 The rate of tooth movement per se can be accelerated by administration of drugs such as prostaglandins, electrical stimulations, vitamin D and osteocalcin, use of ultrasound around the sockets in the jaws. The injection method is always accompanied by certain degree of pain as well as discomfort to the patients.3 So the orthodontists is faced with a challenge of not only completing the treatment faster but also avoiding pain as well as use of user friendly and affordable equipments in the daily practise. With this intention a lot of research has been carried out with relation to Low Level Laser Therapy (LLLT) and it has been reported to be highly useful and successful in different forms of treatment modalities in dentofacial orthopaedics.

Laser lights cause stimulation of the proliferation process of osteoblasts and fibroblasts and regulate the bone remodelling process and in turn accelerate the movement of the teeth. 3, 4 An essential component to understand the entire process of bone remodelling is the explanation of the role that cytokines play and reshape the bone. there is a beginning of inflammatory process of the surrounding periodontium, the cytokine bring about pro inflammatory reactions, mainly Tumour necrosis factor, Interleukin 1β and б. These three are involved with the procedure involved in the acute inflammation too apart from the metabolism, resorption as well as bone deposition inhibition.

When orthodontic forces are applied, the cytokines create Nitrogen oxide that is a known element for bone remodelling procedure. The production of this oxide requires two enzymes- nitrogen- oxide synthesis and endothelial nitrogen- oxide synthesis. When the gene expression of the two enzymes is activated by an array of pro- inflammatory mediators as well as anti- inflammatory mediators that are released as a response to bone resorption and deposition or repair. 3

In case the mechanical forces applied are much greater; then the pulpal tissue response is high enough to cause root resorption also. More studies are essential to see if there is actually any shift in these mediators and what role they can play to be used as markers for understanding the effect of lasers on the tooth movements. 5 The pro- inflammatory cytokines are much higher in the tension zone than that of the pressure zone. Also this helps to conclude that these cytokines thus have a role to play in the osteoclastic activities mediated via different pathological pathways. The number of these mediators is definitely higher as compared to that of the control teeth. 6, 4

The aim of this study was to not only evaluate the effect of low level laser therapy on canine movement but also co relate it with the mediators in the GCF (Gingival Crevicular Fluid) and assess if this can be a better alternative to conventional mechanical procedures that are practiced for bringing about accelerated tooth movement in the patient.

Aim

To assess acceleration of tooth movement using low level laser therapy. To assess the acceleration of tooth movement in canine retraction. To assess the interleukin 1β level in Gingival Crevicular Fluid.

Materials and Methods

Materials

1. 0.022 slot MBT brackets

2. 0.018 inch stainless steel arch wire

3. Low level laser (Gallium-Aluminium-Arsenide Laser)

4. ELISA kit

5. Micro-capillary tube

6. Digital Vernier calliper

7. Dontrics gauge

8. NiTi closed coil springs

Figure 1

Stainless steel arch wire

Figure 2

NiTi closed coil springs

Figure 3

Methodology

After the patient selection, a written informed consent was obtained from all the participants. All ethical norms as per the Helsinki guidelines for human experiments were followed. By coin toss method, each of the participant’s mouth was randomly assigned either to the laser therapy (group 1) and 40 reference sites (group 2), where only NiTi closed coil spring was used for canine retraction by the conventional method without any additional laser therapy.

The initial alignment was done using NiTi wires and 0.022 slot MBT bracket. A 0.018 inch passive stainless steel archwire with molar stops placed mesial to maxillary molars was used for retracting canine using NiTi closed coil spring in reference and experimental site with a force of 150 gms which was measured using a dontrics gauge. On the experimental site orthodontic treatment with fixed appliance, a combination with low level laser therapy (Gallium-Aluminium-Arsenide laser) to the canine on the days 3,7,14 and then every 15 days for 2 months was initiated. 7 The laser had a wavelength of 940nm, energy density was 80 Joules/cm ² and power output was 100 mW that was applied to the root of canine bucally and palatally. The laser was applied at 5 points immediately after the spring attachment for 15 seconds. 8

Figure 4

A: Laser application points on the buccal side; B : Laser application points on the palatal side; C: Force of 150 gms measured using dontrix gauge; D: Collection of GCF before retraction is initiated Collection; E: Collection og GCF after 2 months of initiaiton of retraction

Then 5µL of Gingival Crevicular Fluid (GCF) was collected using a calibrated microcapillary tube from the distal sites of the canines in both the groups and transferred to transport media containing phosphate buffer saline (PBS) which was kept in a box containing dry ice. The collection of GCF was done at baseline and then after 2 months. The GCF was sent to the laboratory to analyse the interleukin 1β levels using the ELIZA kit.

Analysis of the rate of orthodontic tooth movement

The pre and post retraction cast models were prepared. The tips of the canine and that of the mesiobuccal cusp of the first molar on each quadrant were considered to be the points of reference. The measurements were made with the help of a digital Vernier calliper. The pre and post measurements were compared to see if any difference in the tooth movement was observed across both the groups.

Figure 5

Dental casts before and after retraction

Results

The total sample size in the present study was 80 (40 bilateral participants). Table 1 shows the measurements on the cast model at baseline and after 2 months of the treatment of Group 1 and 2. The mean values of the distance measured initially was 19.977 (±1.63) in group 1 and it was 19. 854 (±2.19) in group 2 (Table 2). The mean values of the distance measured after 2 months was 16.469 (±1.719) in group 1 and it was 16.857 (±2.438) in group 2 (Table 2). In this study, we are interested whether there is significant difference between the difference in measurements on the cast model at baseline and after 2 months of the treatment of Group 1 and 2. Unpaired t-test was performed and we observed that the mean difference of the cast model in group 1 was significantly greater than that of group 2 (p= 0.028) (Table 3). Table 04 shows the interleukin 1β levels at baseline and after 2 months of the treatment of Group 1 and 2. The Table 5 shows the mean and standard deviation of the 2 groups for the interleukin 1 β levels at baseline and after 2 months. The mean values of interleukin 1 β levels initially was 289.4 (±9.4) in group 1 and it was 290.3 (±9.4) in group 2 (Table 5). The mean values of interleukin 1β levels after 2 months was 354.5 (±14.33) in group 1 and it was 323.9 (±9.6) in group 2 (Table 5). Also, we are interested whether there is significant difference between the difference in interleukin 1 β levels at baseline and after 2 months of the treatment of Group 1 and 2. The results showed at 95% Confidence Interval for the difference between the 2 groups was between 25.43 and 37.72. Unpaired t-test was performed and we observed that the mean difference of the interleukin 1 β levels in group 1 was significantly greater than that of group 2 (p= 0.00) (Table 6).

Graph 1

Mean values of the initial distance measurement in the two groups at baseline.

Graph 2

Mean values of the initial distance measurement in the two groups after 2 months.

Graph 3

Mean values of the interleukin levels in the two groups at baseline and after 2 months

Summary of Results

The study involved 80 sites in 40 patients. No difference in the mean values of the initial distance between the canine and the molar was observed before the start of the retraction. After 2 months, the laser group showed a significant greater reduction in the canine to molar distance than the site treated with conventional technique. The interleukin 1 β levels raised significantly for the site treated with laser as compared to the other.

Overall we observed that:

Discussion

The major issue with orthodontic treatment is the time involved. More the time, more the follow ups and patient compliance is compromised at times with such a long duration. At times, reinforcing the post treatment measures is also a challenge for the orthodontist. The average active treatment time of two years approximately tests the patience of the patient to a great extent. Hence to attain faster results, it is imperative that bone remodelling occurs at a faster speed and with more consistency to prevent the problem of relapse. The entire treatment time is dictated by the complexity of the condition and the type of treatment plan meted out by the orthodontist. Faster and effective aesthetic results are the needs of the hour. A vigorous attempt to design and execute various forms of accelerated teeth movements is currently on the rise since many decades. Some of these include the use of magnets; current therapies such as photobiomodulation, accelerated orthodontics, chemicals, distraction osteogenesis are among the others. With none of these proving to be highly effective, evidence is being sought to help understand the best, option or if any; a totally different option if available. Light emitting diodes, which came into existence in 1980s when applied to the gingival tissues, seem to activate the PDL cells and the surrounding osteoblasts. This localized effect helps to concentrate only on areas that need to be treated. 2 At times, corticotomies has proven to improve the orthodontic movements by increased stimulation; but with a disadvantage that they can be performed only along the areas with cortical portions of the alveolar bone. Also there is lesser patient compliance due to the surgical procedure involved merely for an accelerated tooth movement. Distraction osteogenesis involve intervention by use of burs along the canines and these holes created around the roots are used further for canine retraction. This has been a proven technique that is not only successful in terms of patient acceptance but also with time. It reduced the time of treatment by a great extent. Low level laser therapy is now the answer to the issue of non-surgical and bloodless intervention with quicker results. This has been directed more towards soft tissues and has a greater potential to provide an impetus to better results compared to the rest. This therapy has been documented extensively in literature. It is an effective method to ensure bone regeneration and modulation to assist in the tooth movements; that is the biggest challenge in clinical practise. Initial experiment was performed on the midpalatal suture regions to bring about the accelerated palatal expansion by means of collagen synthesis. Shimizu et al reported their experiment outcomes on rats. They observed that with LLLT, there was increased vascularization that could serve as an essential factor in tissue repair. An overall effect of more than 30% was observed in these rats with respect to tooth movements. 9 Nonetheless, sparse data is available with respect to human comparative studies, especially in terms of clinical evidence of the same therapy among the Indian population. Certainty of the same with respect to local set up has not been successfully established and is an important gap in the existing literature that we tried to address in the present study. For the present study, only adult patients were chosen as participants and those with any medical history, on anti-inflammatory drugs and with previous orthodontic treatments were excluded to avoid any impending bias with the study results. We used Stainless steel wire (Captain Ortho SS wire) of 0.018 inch diameter which was placed in the arch and retraction was initiated. It is known that teeth movement can be influenced by the type of material and diameter of orthodontic archwire especially during sliding mechanics. It is known that stiffer wires can better resist the tendency of teeth tilting during sliding. Moreover, friction increases as bracket slots are filled. For these reasons, a round, 0.018-inch SS arch wire was selected. The canine bracket was secured tightly with stainless steel ligatures as elastomeric modules tend to lose its elasticity and cause rotation during retraction. The Ezlase 940 (Biolase) diode laser was used to irradiate the canines prior to retraction. According to the International Electrotecnical Commission (IEC) 60825 – 1 standard this laser was classified as class 4 lasers. It had a standardized wavelength of 940 nm, with an output power of 100 mW, and an exposure time of 15 seconds per spot (mesio-cervical, disto-cervical, middle, mesio-apical, disto-apical areas of the canine root). The 940 nm wavelength works efficiently at low power. The low power was well absorbed by hemoglobin and oxyhemoglobin. Hence reduced amount of heat was produced. Laser emitted at the particular wavelength penetrates the tissue depths with ease. Different substance matter preferentially absorbs light at varying wavelengths. Laser photons that travel through a given material with a high absorption coefficient for its specific wavelength will lose energy through absorption more readily than a material with a lower coefficient for that material. Because these photons are readily absorbed, this light travels much shorter distances than those light wavelengths that are not absorbed. The absorption of photons from a laser’s initial ray effectually degrades the power of light with distance travelled. It has been reported that only a fraction of the photons are actively able to reach the desired depth and bring about the required effect. 10 The extent of penetration and the number of photons reaching the desired site was beyond the scope of the present study outcomes. We did a laser irradiation for 3,7,14 and then every 15 days for 2 months of the treatment period in the participants. 7 Five areas were irradiated on the periodontal ligament of the canines for 15 seconds according to the previous published literature. 8 This method helped us cover all the PDL fibres and the alveolar bone around the canine. The wavelength used was 940 nm and this allowed for a penetration of light upto a depth of 0.0001 mm. This also ensured that the exposure of the light was negligible and would not result in any carcinogenic results to the patient at a later stage and also help us avoid unnecessary stimulation and excessive bone and surrounding tissue damage. Nickel titanium closed coil springs were used for retraction of the canines on both laser and non-laser sides. These springs provide a force level that could be maintained for a longer period of time. Nickel-titanium closed coil springs produce a more consistent force when compared with elastomeric chains as a method of force delivery to close extraction space along a continuous arch wire. 11 The force selected for retraction of canines was 150 gms which was measured using a Dontrix gauge (Ormco, Italy). We ensured that light forces were applied to induce better movements, less damage to the tissues and also to reduce pain to the patient. Literature suggests use of lighter forces and also use of intermittent forces if needed rather than greater implied forces for a better result and lesser tissue damage. The retraction spring was reactivated on day 21 for all sides. 11 We prepared study model casts before and at the end of retraction for a better understanding and measurement was made using a digital Vernier calliper for assessing canine retraction. The measurements were compared with two experts to avoid observational bias although there are computer software options available for the same. This use of physical measurement is one of the limitations of our study. The softwares usually are based on the diagnostic casts prepared for scanning images and they are superimposed upon each other to see the amount of difference in the teeth positioning post treatment. Study in the West reports that measurement by calliper is equally effective in reaching a conclusion. 4 In the present study the mean values of the distance measured after 2 months was 16.469 (±1.8) in group 1 and it was 16.857 (±2.5) in group 2. When unpaired t-test was performed, we observed that the mean measurement in group 1 was significantly greater than that of group 2 (p= 0.028) (Table 03). This was similar to the studies reported previously in literature. 8 A 2004 study showed that the irradiated canines were retracted at a rate 34% greater than the control canines over 60 days. The author reported that LLLT significantly accelerates orthodontic movement in humans with a healthy response from periodontal tissues. Therefore it can be considered in order to shorten the treatment duration. 8 The mechanisms of LLLT rely on the red and near‑infrared wavelengths in the electron transport chain in the mitochondria of the cells. The light absorption causes an activation of respiratory chain and oxidation of the NADH pool. The electron transport chain promotes cell changes by increasing ATP supply, and increased electrical potential of the mitochondria membrane, alkalization of the cytoplasm, and activation of nucleic acid synthesis. Mast cells are triggered ultimately. It has been proved that 660, 820, and 940 nm light triggers mast cell degranulation and release TNF. TNFα promotes leukocyte infiltration of tissues. 12, 13, 14, 11, 15, 16, 17

LLLT also stimulates differentiation to myofibroblasts and accelerates wound healing. LLLT given for a short duration can significantly promote proliferation and promote differentiation of human osteoblasts in vitro as compared to non - irradiated cells. Osteoblasts proliferate and differentiate at a higher rate at the site of injury and accelerate the rate of calcium accumulation and bone repair. Abi-Ramia et al stated that LLLT showed reversible hyperaemia with orthodontic tooth movement and faster repair due to an increased pulpal response. 6 Limpanichkul et al reported a clinical trial showing no appreciable effect on LLLT over 4 months in a split mouth study design. This was in complete contrast to the findings of the present study. They concluded that possibly the energy density produced by the laser was way too low and had no effect on the orthodontic tooth movement. 12 Another study reported that there was no statistical difference in the rate of canine movement or canine angulation between laser and conventional technique. In fact when the authors assessed pain via the VAS pain score participants on the laser side were more sensitive than that on the conventional side. Another study conducted in 2014 study used 810 nm galliumaluminium-arsenide (Ga-Al-As) laser, which showed no effect on velocity of canine retraction and on pain perception in adults.7 A study on rabbits cautions the use of LLLT because even though the movements are accelerated, the chances of relapse are significantly higher with the same as compared to that of the conventional therapy.[55] In the present study we observed increased levels of interleukin in GCF at the laser site compared to the controls. The GCF collection was on the distal aspect of the canine as per previous published literature. A 2006 study reported that an increased level coincided with a raised biologic activity with the periodontal tissue during orthodontic tooth movement.[62] The mean values of interleukin 1 beta levels initially was 289.4 (±9.4) in group 1 and it was 290.3 (±9.4) in group 2 (Table 05). The mean values of the interleukin 1 beta levels after 2 months was 354.5 (±14.33) in group 1 and it was 323.9 (±9.6) in group 2 (Table 05). Our findings were similar to that by Bicacki et al and Yassaei where an increase in mediators of inflammation was seen. Another study with use of aligners reported that bone modulators were raised significantly with laser application. A 2016 study in Turkey reported a significant raise in Interleukin levels with application of gallium-aluminium-arsenide diode laser of 20mW. The authors argue that IL-1β levels increase on the compression side is indication of osteoblastic activity while L-1β levels on compression side indicated raised osteoclastic activity during canine retraction. Altan et al reported that even though the biomarkers of inflammation were higher on the laser side it need not reflect always as an accelerated tooth movement. Hence with such contrasting findings, more robust measures are needed to evaluate the biological prospects of LLLT on canine retraction.

Conclusion

We observed that there was a clinically appreciable amount of retraction seen resulting in faster space closure between the canine and the first permanent molar in the group that had low level laser than the other group that was treated by the conventional therapy. We also observed a considerable rise in the interleukin 1β levels in the laser group. This shows that faster tooth movement can be easily achieved with good appreciable results by adding low level laser treatment as a part of the plan for orthodontic patients. Also a need to appreciate the pertinent role that lasers can play in successful yet faster treatment modalities should be explored especially in this field that needs a long term association with the patient for achieving an aesthetic and functional smile.

Conflict of Interest

The authors declare that they have no conflict of interest.

Source of Funding

None.

Ethical Approval

Study is approved by ethical committee of institute and MUHS research committee.

Acknowledgement

I would like to express my sincere gratitude to my mentor and guide Dr. Ajit Kalia (HOD and Professor, department of orthodontics, M. A. Rangoowala College of Dental Science and Resarch Centre, Pune) who provided inspiration and guidance behind the idea of the study.