The use of low level laser to reduce pain, inflammation and edema, to promote wound, deeper tissues and nerves healing, and to prevent tissue damage has been known for almost forty years since the invention of lasers. This review will cover some of the proposed cellular mechanisms responsible for the effect of visible light on mammalian cells, including cytochrome c oxidase (with absorption peaks in the Near Infrared (NIR)). Mitochondria are thought to be a likely site for the initial effects of light, leading to increased ATP production, modulation of reactive oxygen species, and induction of transcription factors. These effects in turn lead to increased cell proliferation and migration (particularly by fibroblasts).

Based on the studies of the low-power laser in the treatment of non-surgical diseases, it can be concluded that most studies have shown its positive effects on the treatment of such diseases, but lack of consistency in the choice of laser standards such as the wavelength, the amount of energy consumed, the surface of laser contact, and the duration of treatment is seen. Most researchers believe that in relation to each of the diseases, the efficiency of the low-power laser is positive. Standard research with qualitative and quantitative assumptions in the clinical setting should be undertaken to achieve original protocols to treat non-surgical diseases with LLLT and photobiomodulation. It seems that LLLT is a useful therapeutic method with a high degree of capacity for progression in future.

Low-level laser (light) therapy (LLLT) is a fast-growing technology used to treat a multitude of conditions that require stimulation of healing, relief of pain and inflammation, and restoration of function. Although the skin is the organ that is naturally exposed to light more than any other organ, it still responds well to red and near-infrared wavelengths. The photons are absorbed by mitochondrial chromophores in skin cells. Consequently electron transport, adenosine triphosphate (ATP) nitric oxide release, blood flow, reactive oxygen species increase and diverse signaling pathways get activated. Stem cells can be activated allowing increased tissue repair and healing. In dermatology, LLLT has beneficial effects on wrinkles, acne scars, hypertrophic scars, and healing of burns. LLLT can reduce UV damage both as a treatment and as a prophylaxis. 

Lasers devices are widely used in various medical fields (eg, surgery, dermatology, dentistry, rehabilitative medicine, etc.) for different applications, ranging from surgical ablation of tissues to biostimulation and pain relief. Laser is an electromagnetic radiation, which effects on biological tissues strongly depends on a number of physical parameters. Laser wavelength, energy output, irradiation time and modality, temperature and tissue penetration properties have to be set up according to the clinical target tissue and the desired effect.

Low-level laser therapy (LLLT) is a newly developing technique in dentistry, although it has been used among medical, dental, physiotherapy, and veterinary professions in some parts of the world for decades. LLLT can offer tremendous therapeutic benefits to patients, such as accelerated wound healing and pain relief. There is much to be learned about the mechanisms, recognition of the therapeutic window, and how to properly use these cellular phenomena to reach the treatment goals.

LLLT with 915 nm wavelength diode laser promoted intraoral mucosal wound healing histologically, and repeated irradiation of 915 nm laser showed better results than a single irradiation in the animal study. Although there were no significant statistical differences between the LLLT and control groups in all inflammatory parameters in the exploratory clinical study, 915 nm laser, as an adjunct to mucosal wound healing, is safe and decreases the occurrence of adverse events and immediate postoperative discomforts clinically. Therefore, this study has demonstrated that 915 nm LLLT is useful for the reduction of immediate postoperative complications after intraoral surgeries including surgical extraction, which usually involves postoperative pain, trismus, and swelling due to the inflammatory process initiated by surgical trauma. It could be safely applied as an auxiliary treatment for mucosal wound healing and inflammation.

In recent decades, low-level laser therapy (LLLT) has been widely used to relieve pain caused by different musculoskeletal disorders. Though widely used, its reported therapeutic outcomes are varied and conflicting. Results similarly conflict regarding its usage in patients with nonspecific chronic low back pain (NSCLBP). This study investigated the efficacy of low-level laser therapy (LLLT) for the treatment of NSCLBP by a systematic literature search with meta-analyses on selected studies.

We review PBM mechanisms of action and dosimetric considerations. Virtually, all conditions modulated by PBM (e.g., ulceration, inflammation, lymphedema, pain, fibrosis, neurological and muscular injury) are thought to be involved in the pathogenesis of (chemo)radiation therapy-induced complications in patients treated for HNC. The impact of PBM on tumor behavior and tumor response to treatment has been insufficiently studied. In vitro studies assessing the effect of PBM on tumor cells report conflicting results, perhaps attributable to inconsistencies of PBM power and dose. Nonetheless, the biological bases for the broad clinical activities ascribed to PBM have also been noted to be similar to those activities and pathways associated with negative tumor behaviors and impeded response to treatment. While there are no anecdotal descriptions of poor tumor outcomes in patients treated with PBM, confirming its neutrality with respect to cancer responsiveness is a critical priority.

Breast cancer related lymphedema (BCRL) is a prevalent complication secondary to cancer treatments which significantly impacts the physical and psychological health of breast cancer survivors. Previous research shows increasing use of low level laser therapy (LLLT), now commonly referred to as photobiomodulation (PBM) therapy, for BCRL. This systematic review evaluated the effectiveness of LLLT (PBM) in the management of BCRL.

We plan to do a systematic review to assess the effects of low-level laser therapy with exercise and exercise alone in participants who are 18 years and above, with a clinical or radiological diagnosis of various shoulder pathologies. We will search CENTRAL, MEDLINE, CINAHL, PEDro, Science Direct, Scopus and Physiotherapy Choices regardless of publication status. We will hand search for subject-specific journals (PhotoMedicine and Laser Surgery, Lasers in Surgery and Medicine and Journals of Lasers in Medical Science) and conference proceedings of World Association for Laser Therapy. Two review authors will independently screen, select studies, extract data and assess the risk of bias based on a priori criteria. Disagreements between review authors will be resolved either through discussion or consultation with a third review author. If there are at least two clinically homogeneous studies, we will perform meta-analysis.