|Year : 2015 | Volume
| Issue : 1 | Page : 53-56
Low-level laser therapy: A biostimulation therapy in periodontics
Snophia Suresh, Satyanarayana Merugu, Nimisha Mithradas, Sivasankari
Department of Periodontics, Thaimoogambigai Dental College, Chennai, Tamil Nadu, India
|Date of Web Publication||19-Jan-2015|
Department of Periodontics Thaimoogambigai Dental College, Golden George Nager, Chennai, Tamil Nadu
Low-level laser therapy (LLLT) is a light source treatment that generates light of a single wavelength. The low-level lasers do not cause temperature elevation within the tissue, but rather produce their effects from photobiostimulation effect within the tissues. Low-level lasers do not cut or ablate the tissue. The therapy performed with low-level lasers ia called as LLLT. LLLT devices include the gallium arsenide, gallium aluminum arsenide infrared semiconductor (gallium-aluminum-arsenide), and helium-neon lasers. The output powers range from 50 to 500 mW with wavelengths in the red and near infrared of the electromagnetic spectrum, from 630 to 980 nm with pulsed or continuous-wave emission. The application of LLLT has become popular in a variety of clinical applications in periodontics including promotion of wound healing and reduction of pain following nonsurgical and surgical procedures.
Keywords: Lasers, low-level laser therapy, periodontal disease, therapeutic Lasers
|How to cite this article:|
Suresh S, Merugu S, Mithradas N, Sivasankari. Low-level laser therapy: A biostimulation therapy in periodontics. SRM J Res Dent Sci 2015;6:53-6
|How to cite this URL:|
Suresh S, Merugu S, Mithradas N, Sivasankari. Low-level laser therapy: A biostimulation therapy in periodontics. SRM J Res Dent Sci [serial online] 2015 [cited 2018 Sep 22];6:53-6. Available from: http://www.srmjrds.in/text.asp?2015/6/1/53/149595
| Introduction|| |
The use of lasers for the treatment has become a common phenomenon in the medical field. The first laser device was made by Maiman in 1960, based on theories derived by Einstein in the early 1900s.  Dr. Leon Goldman used ruby laser, on the tooth of his dentist brother, and the result was painless surface crazing of enamel.  The first application of laser in maxillofacial surgery was introduced by Lentz et al. in 1977.  LASER is an acronym for light amplification by stimulated emission of radiation. Laser light is monochromatic, coherent and collimated beam. Low-level laser therapy (LLLT) has been investigated and used clinically for over 30 years, which justifies the increasing interest in the effects of laser and the significant amount of scientific publications in the literature.
Mechanism of action of low-level lasers
The biostimulatory and inhibitory effects of LLLT are governed by the Arndt-Schulz law. According to this law, low-dose will increase physiologic processes, and strong stimuli will inhibit physiological activity. The output powers for LLLT range from 50 to 500 mW with wavelengths in the red and near infrared of the electromagnetic spectrum, from 630 to 980 nm with pulsed or continuous-wave emission. The low-level lasers do not cause temperature elevation within the tissue, but rather produce their effects from photobiostimulation effect within the tissues. Low-level lasers do not cut or ablate the tissue. The therapy performed with low-level lasers is called as LLLT or therapeutic laser therapy, and this therapy has been referred as biostimulation and biomodulation. 
Biostimulatory effect of laser irradiation represents a set of structural, biochemical and functional changes in living microorganisms. It acts directly on stimulating components of the so-called antenna pigments of the respiratory chain and manifest as an immediate effect cell vitalization by adenosine triphosphate (ATP) mitochondrial production increase. Laser enhanced biostimulation has been reported to induce intracellular metabolic changes, resulting in faster cell division, proliferation rate, migration of fibroblasts and rapid matrix production. ,
The first commercialized biostimulative laser was a helium-neon (HeNe) laser of <1 mW. The use of HeNe laser for biostimulation is limited by the need for an optic fiber, the size of the machine and the still rather low power option, now typically in the range 5-25 mW. It has generally been replaced by the indium-gallium-aluminum-phosphide laser, a diode producing red laser in the range 600-700 nm and able to deliver as much as 500 mW. The most frequently used laser for LLLT in dentistry is the gallium-aluminum-arsenide laser. It often operates in the spectrum between 780 and 830 nm. The output is typically between 10 and 500 mW. An advantage of the diode lasers is the small size and option for battery operation, making them rather handy and portable. These lasers are work in continuous mode, but can be mechanically or electronically pulsed.
Biostimulatory effect of laser irradiation is determined by the magnitude of the absorbed light energy. Energy depth of penetration depends on factors such as wavelength, optical and temperature characteristics, power, energy values, exposure time, wave shape, and optical characteristics of tissue-absorption and scattering coefficient.
The mechanisms of LLLT are complex, but essentially rely upon the absorption of particular visible red and near infrared wave lengths in photoreceptors within sub-cellular components, particularly the electron transport (respiratory) chain within the membranes of mitochondria. Photon absorption causes shift in the molecular configuration of the photoacceptor, accompanying with an associated alteration in the molecular signal of the cell. The alterations in photoacceptor function are the primary reactions and subsequent alterations in cellular signaling, and cellular functions are secondary reactions.
Primary reactions after light absorption
The first mechanism, proposed in 1981 for the action of LLLT was the singlet oxygen hypothesis.  Certain photo- absorbing molecules like porphyrins after absorption of laser light lead to the generation of singlet oxygen, which are needed for stimulation of RNA and DNA synthesis rate. The next mechanism proposed in 1988 was redox properties alteration hypothesis. According to this hypothesis, photoexcitation of certain chromatophores in the cytochrome c oxidase molecule influences the redox state and consequently, the rate of electron flow in the molecule. The latest development proposed NO hypothesis that stated that laser irradiation and activation of electron flow in the molecule of cytochrome c oxidase could reverse the partial inhibition of the catalytic center by NO. Transient local heating hypothesis states that local transient rise in temperature of absorbing biomolecules may cause structural changes and trigger biochemical activity.  In 1993, superoxide anion hypothesis suggested that activation of the respiratory chain by irradiation would also increases the production of superoxide anions.
Secondary reactions after light absorption (cellular signaling)
The secondary reactions that occur after light absorption are cellular signaling pathways and mitochondrial retrograde signaling. The mitochondrial retrograde signaling is the communication in cells from mitochondria to the nucleus that influences many cellular activities, under both normal and pathophysiological conditions. The low-intensity red and near-infrared light act on cells through a primary photoacceptor, cytochrome C oxidase, the terminal enzyme of the mitochondrial electron transport chain. Absorption of light by cytochrome C oxidase can increase the mitochondrial membrane potential, thereby releasing ATP and reactive oxygen species, which leads to increased energy availability and signal transduction.
The overall redox state of a cell represents the net balance between stable and unstable reducing and oxidizing equivalents. Recent studies have revealed that many cellular signaling pathways are regulated by the intercellular redox state. , Oxidants stimulate cell signaling systems, and reductants suppress the upstream signaling cascades, resulting in suppression of transcription factors. The redox based gene expression is a fundamental mechanism in cell biology.
In phagocytic cells, irradiation initiates a non-mitochondrial respiratory burst (production of reactive oxygen species, especially superoxide anion) through activation of nicotinamide adenine dinucleotide phosphate-oxidase located in the plasma membrane of these cells. The irradiation effects on phagocyte cells depend on the physiological status of the host organism as well as on radiation parameters.
Clinical applications of low-level laser therapy
The application of low-level lasers in medicine was introduced in the 1970s and 1980s. Since then considerable scientific work including the use of cell cultures, animal models and clinical studies has been undertaken to evaluate its potentially beneficial effects. The application of LLLT has become popular in a variety of clinical applications, including promotion of wound healing and reduction of pain. Low-level laser applications in dentistry include the promotion of wound healing in a range of sites, like surgical wounds, extraction sites, recurrent aphthous ulcerations, etc. 
Applications of LLLT in dental and periodontal treatments represent the subject of many in vivo and in vitro studies, which recommend the use of laser therapy after gingivectomy and gingivoplasty procedures due to its ability to speed up the healing process. , The low-level lasers facilitate fibroblast and keratinocyte motility, collagen synthesis, angiogenesis and growth factors release, thus facilitating the healing process. This therapy has been used in pain management protocols following gingivectomies, and as an adjunct treatment in nonsurgical periodontal procedures. 
There are several mechanisms by which LLLT may stimulate the proliferation of fibroblasts. LLLT has been shown to stimulate the production of basic fibroblast growth factor (bFGF), a multifunctional polypeptide which supports fibroblast proliferation and differentiation. Fibroblasts irradiated with low dose LLLT show both increased cell proliferation and enhanced production of bFGF, while high dose LLLT suppresses both parameters.
A further effect of LLLT on fibroblasts that can influence the wound healing process is the transformation of fibroblasts into myofibroblasts, which are responsible for wound contraction. 
Ozawa et al. showed that laser therapy significantly inhibits the increase of plasminogen activator (PA) induced in human periodontal ligament cells in response to mechanical tension force. PA is capable of activating latent collagenase, the enzyme responsible for cleaving collagen fibers. Laser therapy was also efficient in the inhibition of prostaglandin E2 (PGE2) synthesis. In human gingival fibroblast culture, leicestershire partnership NHS trust (LPT) significantly inhibited PGE2 production stimulated by lipopolysaccharide through a reduction of cyclooxygenase-2 gene expression in a dose dependent manner. 
Mizutani et al. suggested that LLLT inhibits the arachidonic acid cascade in damaged tissue, leading to decreased production of PGE2. Later, this phenomenon interferes with the production of bradykinin and many kinds of inflammatory cytokines. In addition, the increase in local blood flow improves acidosis and simultaneously, promotes both the release and removal of substances related to pain. 
A study done by Lui et al. suggested that the combined course of photodynamic therapy with LLLT could be a beneficial adjunct to nonsurgical treatment of chronic periodontitis on a short term basis. 
Regeneration of new bone is of major importance in several surgical procedures and also in periodontal therapy. LLLT should be used in the surgical site after suturing and during the initial healing period when the proliferative activity is high. Repeated irradiation for 2-weeks needed for a pronounced effect. LLLT can also be used in combination with guided tissue regeneration and different bone substitutes. ,
Low-level laser therapy may be used as additional treatment for accelerating implant healing in bone. The use of LLLT at a range of doses between 1.5 and 3 J/cm 2 may modulate the activity of cells interacting with an implant thereby enhancing tissue healing and ultimate implant success. 
Leicestershire partnership NHS trust has been suggested as an alternative method for postoperative pain control. Compared to oral analgesics and non-steroidal anti-inflammatory drugs, LPT can be advantageous because the therapeutic window for its anti-inflammatory action overlaps with its ability to improve tissue.
Repair. Some authors describe a possible stabilization of nerve cell membranes, probably due to the more stable conformation of the lipid bilayers induced by LPT, and the associated integral proteins of the nerve cell membrane, which have already been reported in the literature.  The enhanced redox systems of the cell and an increase in ATP production have also been shown to restore neuronal membranes and decrease pain transmission. 
A systematic review by Bjordal et al. concluded that LPT can modulate the inflammatory process in a dose-dependent manner and that it can be titrated to significantly reduce acute inflammatory pain in the clinical setting.  The author confirmed that, in acute pain, the optimal effects of LPT can be achieved when it is administered in higher energy densities during the first 72 h in order to reduce inflammation, followed by lower dosages to the target tissue during the following days with the aim of promoting tissue repair.
Laser units used for LLLT are generally classified as class III or class IIIb in terms of the optical hazard, which they pose to staff and patients. Because a low power treatment beam can be focused by the eye to give a high power density on the retina the optical hazard is sufficiently great that laser safety standards mandate the wearing of appropriate protective glasses by patients and clinicians during treatment.
| Conclusion|| |
The positive effect of LLLT is due to unspecific stimulatory action of laser beam by increasing the collagen production, enzyme activity, micro- and lymph-circulation, fibroblast proliferation, decrease of local hypoxia, anti-inflammatory effect, and pain reduction. There is a good evidence that the enhanced cell metabolic functions seen after LLLT are the result of activation of photo-receptors within the electron transport chain of mitochondria. Future trials of new LLLT applications in dentistry should make use of standardized, validated outcomes, and should explore how the effectiveness of the LLLT protocol used may be influenced by wavelength, treatment duration, dosage, and the site of application.
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