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REVIEW ARTICLE
Year : 2019  |  Volume : 22  |  Issue : 10  |  Page : 1313-1318

Low-level laser therapy in dentistry: Extra-oral applications


1 Department of Pediatric Dentistry, Faculty of Dentistry, King Abdulaziz University, Jeddah, Saudi Arabia
2 Department of Pediatric Dentistry, Faculty of Dental Medicine for Girls, Al Azhar University, Cairo, Egypt

Date of Acceptance19-Mar-2019
Date of Web Publication14-Oct-2019

Correspondence Address:
Dr. N M Alamoudi
Department of Pediatric Dentistry, King Abdulaziz University, Faculty of Dentistry, KSA, Jeddah
Saudi Arabia
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/njcp.njcp_53_19

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   Abstract 


Low-level laser therapy (LLLT) is considered as a recent technique in the dental field. Nowadays, it is used by many clinicians in dentistry. The stimulation of the healing process and pain relief are among its most popular uses. The purpose of this paper is to discuss and review the latest extra-oral applications of LLLT in the dental field. An electronic search of English scientific papers from 2000 to 2018 was accomplished using PubMed and Google Scholar search engines. The following key words were used extra-oral, applications, LLLT, and dental field. This review demonstrates the marked effectiveness of LLLT in the management of many conditions and how it could improve the quality of life of many patients. However, LLLT is still considered a recent alternative and requires more understanding of its mechanism of action by conducting more high-quality randomized clinical trials with larger sample sizes and longer follow-up periods.

Keywords: Dental field, extra-oral, low-level laser therapy


How to cite this article:
Nadhreen A A, Alamoudi N M, Elkhodary H M. Low-level laser therapy in dentistry: Extra-oral applications. Niger J Clin Pract 2019;22:1313-8

How to cite this URL:
Nadhreen A A, Alamoudi N M, Elkhodary H M. Low-level laser therapy in dentistry: Extra-oral applications. Niger J Clin Pract [serial online] 2019 [cited 2019 Nov 19];22:1313-8. Available from: http://www.njcponline.com/text.asp?2019/22/10/1313/269021




   Introduction Top


A laser could be defined as a device that produces light energy through a process of optical amplification according to the stimulated emission of electromagnetic radiation.[1] It is considered a great innovation that serves many fields including medicine, surgery, dentistry, and cosmetics. “Laser” as a word is an abbreviation for light amplification by stimulated emission radiation. In dentistry, it is used as an adjunct that supplements many hard and soft tissue procedures.[2] In 1960, the laser was used in dentistry for the first time by Maiman during the treatment of carious enamel and dentine.[3] With the current technical advance, many types of laser are introduced, such as argon,[4] carbondioxide (CO2),[5] neodymium-aluminum-garnet (Nd:YAG),[6] or erbium-yatrium-garnet (Er:YAG), and diode laser.[7]

Laser irradiation offers many advantageous features as hemostasis and absence of mechanical contact and its regenerative capacity is proven in the literature.[8] It also could reduce the bacterial cell count at the site of application.[9],[10],[11],[12] A soft tissue laser-like diode laser results in minimal or no bleeding, more rapid healing and reduced tendency for infection postoperatively.[13]

Nowadays, low-level laser therapy (LLLT) becomes a technique of interest by many researchers because its many advantageous characteristics. One of these characteristics is its anti-inflammatory action. This treatment has the ability of increasing collagen production, reducing the inflammatory exudation and enhancing revascularization and epithelization.[8],[14],[15],[16],[17] The aim of this paper is to review the literature regarding the latest applications of LLLT in the field of dentistry.


   Materials and Methods Top


An electronic search of English scientific papers from 2000 to 2018 was accomplished using PubMed and Google Scholar search engines. The following key words were used extra-oral applications, LLLT, and dental field.


   Discussion Top


Diode laser

A diode laser is considered a semi-conductor laser and it is also called “soft” or “cold” laser. Its cost is less than its “hot” laser counterparts.[18] Diode lasers are most commonly applied in procedures termed as “low-level-laser therapy (LLLT).” These procedures are according to the concept of bio-stimulation.[19]

Low-level-laser therapy

As mentioned above, the use of diode lasers in bio-stimulation procedures is what the term “low-level-laser therapy” means. It is also known as low-light therapy or photo-bio-modulation “PBM.” This technique includes the use of a low-intensity light to stimulate non-thermal biochemical changes within cells.[1] Among the applications of LLLT are an acceleration of wound healing process, enhancing bone repair and remodeling, restoring normal neural function after nerve injury, pain reduction, stimulation of endorphin release, and modulation of the immune system.[20],[21]

History of LLLT

The Russian literature reported a 30-year experience with LLLT technique.[22],[23] In addition, the technique has been commonly used in Japan [24] and Europe.[25],[26]

The era of LLLT has started with Dr. Nils Finsen, who has won a Nobel Prize in 1903, for his achievement in treating diseases as lupus vulgaris using concentrated light energy.[27] The first working ruby laser was developed by Professor Maiman TH in 1960. It was used for healing wounds, activation of the immune system, and proliferation of endothelial cells.[3],[28],[29],[30] In 1960 also, Helium-Neon (He-Ne) laser was used in different wavelengths (633 nm as a basic wavelength) for erythropoiesis (red blood cells production).[31],[32] Semi-conductor (diode) laser started to be used in 1962 for its anti-inflammatory effect and its ability to induce proliferation and activate micro-circulation.[33] In 1963, an in vitro trial was conducted using Nd:YAG laser with a wavelength of 532 nm to oxygenate red blood cells.[28],[34] One year after, in 1964, another in vitro trial was carried out using a higher wavelength (1064 nm) of Nd:YAG laser to enhance proliferation and collagen synthesis.[35],[36],[37] In the same year, CO2 laser healing ability was tested on purulent wounds.[38],[39] Then in 1968, Helium-Cadmium laser beam was used in a trial to induce changes in hemodynamics.[40] In addition, in that year, Mester E et al. came up with the phenomenon of “laser bio-stimulation.”[29],[30] [Table 1] mentions the main parameters of LLLT.
Table 1: LLLT parameters (Original)

Click here to view


Effects of LLLT in the dental field

1/Wound healing

Two studies were carried out on rats to test the effects of LLLT on the healing of skin wounds by secondary intention. Daily application of LLLT following operation, stimulated collagen synthesis and increased the strength of the wound scar. Increasing the laser power density up to 9.3 J/cm 2 had slowed down the reparative process.[41],[42] Many in vivo and in vitro trials studied the effect of LLLT on wound healing and showed conflicting results. All of these studies reported that LLLT at low doses had a stimulatory effect while at high doses it exerted an inhibitory effect.[43],[44] When LLLT is applied before wounding, no significant benefits have been shown.[45],[46]

Khadra conducted another experiment to study the effects of gallium-aluminum arsenate laser (GaAlAs), which is a diode laser, on the healing of bone defects in 10 rats. After 4 weeks of treatment, the rats were euthanized for histological assessment. A significant increase in the calcium, phosphorus, and protein was observed. In conclusion, LLLT plays a positive role in bone formation to fill bony defects.[47]

In 2006, Rocha Jr. et al. studied the effect of LLLT (Twin laser) on cutaneous wounds created on rats. They were divided into a laser group and a control group. In the laser group, the wounds were exposed for 15 s to a 3.8 J/cm 2 laser dose, 15 mW of potency. The laser applied three timesimmediately after operation, 2 days, and 7 days later. Ten days following surgery, histopathology and histomorphology were performed. In the laser group, there was increased vascularization, fibroblast proliferation, and decreased inflammatory infiltrate. However, the control group showed epithelial proliferation and areas of ulceration and granulation tissue. The healing in the control group included the formation of a whitish crust and a scar with elevated rims and a red core, whereas in the wounds submitted to laser therapy, the scar had more evident rims and a slightly unleveled central portion. This experiment concluded that tissue repair modulation using LLLT resulted in faster and more organized healing.[48]

After its use had succeeded in animal models, LLLT started to be used on human subjects in the 1970s (Nussbaum et al. 1999). A study was carried out on human patients to test the efficacy of LLLT in burn healing. Nineteen patients were included, and in each patient, one burn was considered as control and another burn was treated with a soft laser device (Helbor, Gallspach, Austria) with a circular application of a continuous diode laser using a 400-mw potency emitting a red laser light with a 670 nm wavelength. A dose of 4 J/cm 2 was applied two times a week. All burns treated with laser showed visible improvement except two lesions. As a conclusion, LLLT could be beneficial for burn patients.[49]

One hundred fifty-two diabetic patients with purulent wounds of skin underwent LLLT. Results of this study demonstrated that the healing period was shortened following laser application.[50] In another study, 512 patients with corneal wounds, burns, and ulcers were treated using LLLT. Compared to the control group, LLLT accelerated and enhanced healing of injuries.[51] Both studies found that daily application of LLLT resulted in better effects than single or weekly exposures.

2/Musculoskeletal pain

LLLT has been used successfully for the treatment of many types of pain such as rheumatoid arthritis, chronic pain, and muscle strain.[52] However, the results were conflicting regarding its use in synovitis [53] and musculoskeletal injuries.[54] A meta-analysis collected the results of many papers studied the effects of LLLT on musculoskeletal pain. This meta-analysis included 23 trials, of which 17 used a controlled design with 10 of them being double-blinded. Although studies considered for pooling used different methodologies, pooling pain score data from 13 of these studies revealed small differences between study and control groups.[55] Many studies have shown that LLLT has a positive effect in relieving acute and chronic musculoskeletal pain, however, the follow-up periods were short (not more than 2 years). Moreover, the American Academy of Orthopedic Surgeons is not with or against its use. According to FDA, its use is approved as adjunct method for temporary reduction of pain. These facts suggest more clinical trials that are well-designed.[1]

3/Trigeminal neuralgia

Trigeminal neuralgia (TN) is considered one of the most painful conditions that could affect old people, younger people, or even children. It is defined as an episodic, sharp, unilateral, and electric-shock-like pain that affects the branches of trigeminal nerve and feels in the eyes, lips, nose, forehead, and jaws.[56]

LLLT was used in many studies to evaluate its effects on the pain associated with TN. Walker recruited 26 patients with post-herpetic neuralgia (PHN), TN, sciatica, and osteoarthritis. These patients were exposed to low-power He-Ne laser with the parameters set on 1 mW power, 632.5 nm wavelength, 20 Hz frequency, and application time of 30 to 90 s, 3 days weekly for 10 weeks. Nineteen patients showed significant improvement in the pain intensity and frequency.[57]

In 1988, Walker et al. evaluated patients with a history of TN to low-power He-Ne laser (1 mW, 632.5 nm, 20 Hz). It was applied to the skin overlying the painful areas for 20 s, 3 days weekly for 10 weeks. In addition, the patients showed significant reduction in the pain intensity and frequency.[58]

Iijima et al., conducted a trial examining 36 patients suffering from PHN after exposure to low-power He-Ne laser. The laser was applied 2 to 3 times weekly. The study resulted in 88.9% efficacy and 55.3% pain relief.[59] In another study by Iijima et al., a group of 18 patients with PHN treated using low-power He-Ne laser were included. The examiners used four-grade estimation, visual analogue scale (VAS), and modified McGill pain questionnaire (MPQ) after every 10 of 50 irradiations to evaluate the effectiveness of treatment. The study concluded that low-power He-Ne laser is a safe and effective therapy for PHN.[60]

The efficacy of LLLT was also evaluated by Kemmotsu et al., where they assessed the effectiveness of continuous waves of GaAlAs laser (830 nm, 60 mW) in 63 patients with PHN. The study results described the immediate effect of LLLT as very good in 26 patients and good in 30 patients. After complete exposure, the long-term effects of LLLT in this study resulted in the absence of pain in 12 patients and the presence of slight pain in 46 patients with no reported side effects or complications.[61]

A study by Kim et al. involved the use of CO2, GaAlAs, and He-Ne laser devices at low power in patients with TN. The patients were divided into two groups; a group was treated using laser and another group was treated with both laser and medication. The study concluded that the group with combined treatment revealed more pain relief.[62]

Inspite all these successful positive results, a study by Hansen and Thorøe showed that there was no significant difference in the analgesic effect between laser group and control group.[63]

4/Temporomandibular joint disorders (TMDs)

Temporomandibular joint disorders (TMDs) is a term including disorders affecting the temporomandibular joint (TMJ), muscles of mastication, and their surrounding structures; characterized by pain, joint noise, and limited mandibular movement.[64],[65] The etiology is known to be multifactorial including parafunctional habits, trauma, emotional stress, hereditary, and occlusal factors.[64]

LLLT use for TMDs is beneficial because of its ease of application, analgesic, anti-inflammatory, and regenerative effects.[66],[67],[68] However, studies on the efficiency of LLLT in treating TMDs demonstrated conflicting results. This may be caused by the great variations in the parameters and methodology used among studies.[69]

Kulekcioglu et al., conducted a double-blinded clinical trial to assess the efficiency of LLLT in the treatment of patients with TMDs. Thirty-five patients were included, where 20 patients were randomly assigned to the laser group and 15 patients received placebo laser. The patients in the laser group underwent 15 sessions of LLLT. Patients in both groups were instructed to perform certain exercises. Pain, joint motion, number of joint sounds, and tender points were evaluated. Regarding pain, both groups showed significant reduction in pain. Only the patients who received LLLT, demonstrated significant improvement in the mouth opening, lateral motion, and number of tender points. LLLT could be considered as an alternative treatment modality to manage TMDs.[70]

In 2005, de Medeiros et al. evaluated 15 patients with pain related to the masseter muscle. Those patients were exposed to LLLT to relief their pain. The laser was applied from a distance of 2 mm. After treatment, measurement of the bite strength showed improvement in the muscle strength on both sides. The study concluded that LLLT is an effective method to treat subjects with orofacial pain.[71]

Venancio et al., conducted a double-blinded clinical trial on 30 patients diagnosed with a TMD. Fifteen patients were subjected to the treatment with an infrared laser (780nm, 30mW, 10s, 6.3J/cm 2) at three TMJ points. The other 15 patients served as a control group. The treatment was evaluated by using VAS, range of mandibular movements, and TMJ pain threshold. There was no significant differences observed between both groups and more studies are needed.[66]

In another double-blinded clinical trial, 39 patients with myogenic orofacial pain, limited mandibular movements, chewing difficulties, and tender points were involved in this study. Twenty-four patients were exposed to LLLT for 10 sessions daily and the remaining 15 patients received non-operating placebo laser. There was a significant improvement in the chewing ability and maximum mouth opening and significant reduction in pain and the number of tender points. In conclusion, LLLT should be considered as an alternative treatment method for TMDs.[72]

Emshoff et al., in 2008, utilized a randomized double-blinded design to carry out a trial examining the effectiveness of LLLT in the treatment of TMDs. Fifty-two patients were evenly randomly assigned into two groups. The test group received LLLT using He-Ne laser (632.8 nm, 30 mW), 2 to 3 times per week for 8 weeks. The control groups were subjected to placebo laser. Comparing the two groups, the improvement in the functions was not shown to be significant. They concluded that LLLT is not better than the placebo in managing pain.[67]

Shirani et al., aimed in their double-blinded clinical trial to evaluate the efficiency of LLLT in relieving myofascial pain. Sixteen subjects diagnosed to have myofascial pain dysfunction syndrome were recruited. Half of the patients were irradiated using two probes of diode laser (660 nm, 6.2 J/cm2, 6 min) continuous wave and (890 nm, 1J/cm2, 10 min, 1500 Hz). The other 8 patients were not irradiated. The results showed that the pain in the laser group was significantly reduced in comparison with the control group. LLLT system used in the study was effective in reducing myofascial pain.[73]

In 2010, Carvalho et al. studied the effect of different laser wavelengths on the pain related to TMDs. Seventy-four patients were treated using laser phototherapy set on the following wavelengths 780 nm, 790 nm or 830 nm, and/or 660 nm. The treatment included laser application for 3 sessions in the week for 6 weeks. The VAS was used to assess pain after 12 sessions of treatment. After data analysis, 64% of the patients showed significant improvement. The use of red and infra-red laser beams was significantly effective in pain reduction.[68]

Mazzetto et al., conducted a clinical trial aimed to investigate the improvement of mandibular movements and TMD painful symptoms, after LLLT application. Twenty out of forty patients were treated using GaAlAs laser (830 nm, 40 mW, 5J/cm 2) two times a week for 4 weeks. The other 20 patients received placebo laser. There was a significant improvement in the pain and mandibular movements, suggesting that LLLT can be considered as a supportive treatment of TMDs.[74]

A recent review of literature was performed on the application of LLLT in patients with TMDs. It included 3 literature reviews and 13 clinical trials. After analysis, it was concluded that the literature on the use of LLLT in treatment of TMDs is still limited and shallow, and more double-blinded clinical trials are needed to prove its efficacy. Moreover, the great differences in the methodologies and laser parameters used among the studies indicate that results of these studies should be taken with caution.[69]


   Conclusion Top


The field of laser dentistry is endlessly expanding and LLLT continues to be a promising modality through its several extra-oral applications in different dental specialties. However, LLLT is still considered a recent alternative and requires more understanding of its mechanism of action by conducting more high-quality trials with larger sample sizes and longer follow-up periods.

Acknowledgment

The authors acknowledge with thanks Deanship of Scientific Research (DSR) for their technical and financial support.

Financial support and sponsorship

This project was funded by the Deanship of Scientific Research (DSR) at King Abdulaziz University (Jeddah, Saudi Arabia) under grant number G-52-165-38.

Conflicts of interest

There are no conflicts of interest.



 
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