Efficacy of low-level laser therapy in nerve injury repair-a new era in therapeutic agents and regenerative treatments

Neural Development and Repair Induced by Femtosecond Laser Stimulation

Dendritic spines function as postsynaptic sites, receiving excitatory signals from presynaptic axons. The synaptic plasticity of spines underlies the refinement of neuronal circuits. Neural cognitive disorders are commonly associated with the impairment and elimination of dendritic spines. In this study, we report an all-optical method to activate dendritic spine growth and regeneration by a single short flash of femtosecond laser stimulation. The inhibited development and loss of spines can be rescued by a transient illumination of the laser inside a micrometer region of the soma by activating the extracellular signal-regulated kinase (ERK) signaling pathway. The rescued neurons exhibit function. Hence we provide a potential noninvasive method for the regeneration of dendritic spines.

Adjunctive Effect of Photobiomodulation Therapy with Nd:YAG Laser in the Treatment of Inferior Alveolar Nerve Paresthesia

Background: Disruption of peripheral branches of the trigeminal nerve in the field of maxillofacial surgery is a known risk due to the close connection of these branches with the bony structures of the maxilla and mandible. As a result, injuries of the lingual nerve and inferior alveolar nerve take place within routine maxillofacial surgery procedures, including local anesthetic injection, wisdom tooth surgery, and dental implant placement, resulting in paresthesia and dysesthesia. During the last three decades, low-level lasers (LLL) have been frequently used in various medical fields. Lately, this application has increased in several sectors. Methods and materials: This experiment was designed to explore the effect of low-level laser therapy (LLLT) with Nd:YAG on the paresthesia and dysesthesia of the lower lip. This ethics committee of Tbzmed, Tabriz, Iran, proved the present experiment with ethical code: IR.TBZMED.REC.1401.839. Results: After completing 10 sessions of laser therapy for the case group consisting of 25 patients with lower lip anesthesia, the visual analog scale index results revealed that following six sessions of laser therapy, a significant difference appeared in contrast to the control group. Also, according to the two-point tests, significant difference among the experimental and the control group appeared after ninth session of the laser therapy. Conclusions: Altogether, these data suggested LLLT with Nd:YAG as an effective treatment option for decreasing the anesthesia of the lower lip.

Photobiomodulation Therapy for Managing Motor and Sensory Dysfunctions Following Temporomandibular Joint Surgery: A Case Report

Introduction: Surgical procedures involving the temporomandibular joint (TMJ) are frequently associated with nerve injuries and subsequent dysfunctions. Considering that traumatic peripheral nerve injuries may resolve slowly and their prognosis is generally unpredictable, the current study aimed to report a clinical case in which both motor (affecting the temporal and zygomatic branches of the facial nerve) and sensory dysfunctions (affecting the auriculotemporal nerve of the trigeminal nerve) following TMJ surgery were effectively treated by using photobiomodulation therapy (PBMT). Case Report: PBMT sessions, involving a total of 30 facial points, were administered twice a week for 10 weeks. The following parameters were utilized: wavelength of 808 nm, energy density of 75 J/cm2, power output of 100 mW, total energy of 3 J, and duration of 30 seconds per point. A considerable improvement in both facial asymmetry and muscle function was achieved within 5 weeks, along with a total restoration of cutaneous sensitivity. By the 10th week of PBMT, the facial movement dysfunction was completely resolved. Conclusion: According to the current case, PMBT seems to be an effective intervention to manage motor and sensory nerve dysfunctions following TMJ surgery.

Nerve Injury and Photobiomodulation, a Promising Opportunity: A Scoping Review on Laser Assisted Protocols for Lesions in the Oral Region

The currently available therapeutic options for restoring function and sensitivity in long-term nervous injuries pose challenges. Microsurgery interventions for direct nerve repair often lead to serious complications and limited success. Non-surgical methods, although somewhat effective, have limited benefits. These methods involve drug administration, such as with analgesics or corticosteroids. Photobiomodulation therapy (PBMT) has emerged as a promising approach based on clinical and laboratory studies. PBMT stimulates the migration and proliferation of neuronal fiber cellular aggregates, as reported in the literature. Experimental studies on animal models with peripheral nerve compression injuries have shown that PBMT can enhance the functionality of damaged nerves, preserving their activity and preventing scar tissue formation. The mechanism of action depends on the wavelength, which can positively or negatively affect photo acceptor resonances, influencing their conformation and activities. These findings suggest that photobiomodulation may accelerate and improve nerve regeneration. This review explores various methodologies used in photobiomodulation for regenerating nerve sensitivity after surgical trauma involving nerve structures, in the oral and peri-oral region. Research was conducted to evaluate which laser-assisted therapeutic protocols are used to improve the recovery of nervous sensitivity, using the JBI methodology for scoping reviews and following the PRISMA methodology.

Treating Nerve Injury After Endodontic Microsurgery Using Laser Photobiomodulation: A Report of Two Cases

The purpose of this case report was to inform dentists and dental specialists about a non-invasive, viable treatment option that could aid in the recovery of patients who have experienced iatrogenic nerve injuries. Nerve injury is an inherent risk of many dental procedures, and a complication that can negatively impact a patient's quality of life and activities of daily living. Managing neural injuries presents a challenge for clinicians as there are no standard protocols reported in the literature. While spontaneous healing of these injuries can occur, the duration and degree of healing can vary greatly between individuals. Photobiomodulation (PBM) therapy is used as an adjunct in medicine for functional nerve recovery. Once target tissues are illuminated with a low-level laser during PBM, the light energy is absorbed by the mitochondria causing ATP production, modulation of reactive oxygen species, and the release of nitric oxide. These cellular changes explain why PBM has been shown to aid in cell repair, vasodilation, reduction in inflammation, accelerated healing, and an improvement in postoperative pain. This case report presents two patients with neurosensory alterations after endodontic microsurgery with significant improvement in their condition after PBM treatment using a 940 nm diode laser.

Biphasic dose response in the anti-inflammation experiment of PBM

Non-invasive laser irradiation can induce photobiomodulation (PBM) effects in cells and tissues, which can help reduce inflammation and pain in several clinical scenarios. The purpose of this study is to review the current literature to verify whether PBM can produce dose effects in anti-inflammatory experiments by summarizing the clinical and experimental effects of different laser parameters of several diseases. The so-called Arndt-Schulz curve is often used to describe two-phase dose reactions, assuming small doses of therapeutic stimulation, medium doses of inhibition, and large doses of killing. In the past decade, more and more attention has been paid to the clinical application of PBM, especially in the field of anti-inflammation, because it represents a non-invasive strategy with few contraindications. Although there are different types of lasers available, their use is adjusted by different parameters. In general, the parameters involved are wavelength, energy density, power output, and radiation time. However, due to the biphasic effect, the scientific and medical communities remain puzzled by the ways in which the application of PBM must be modified depending on its clinical application. This article will discuss these parameter adjustments and will then also briefly introduce two controversial theories of the molecular and cellular mechanisms of PBM. A better understanding of the extent of dualistic dose response in low-intensity laser therapy is necessary to optimize clinical treatment. It also allows us to explore the most dependable mechanism for PBM use and, ultimately, standardize treatment for patients with various diseases.

Raman spectroscopy and sciatic functional index (SFI) after low-level laser therapy (LLLT) in a rat sciatic nerve crush injury model

Axonotmesis causes sensorimotor and neurofunctional deficits, and its regeneration can occur slowly or not occur if not treated appropriately. Low-level laser therapy (LLLT) promotes nerve regeneration with the proliferation of myelinating Schwann cells to recover the myelin sheath and the production of glycoproteins for endoneurium reconstruction. This study aimed to evaluate the effects of LLLT on sciatic nerve regeneration after compression injury by means of the sciatic functional index (SFI) and Raman spectroscopy (RS). For this, 64 Wistar rats were divided into two groups according to the length of treatment: 14 days (n = 32) and 21 days (n = 32). These two groups were subdivided into four sub-groups of eight animals each (control 1; control 2; laser 660 nm; laser 808 nm). All animals had surgical exposure to the sciatic nerve, and only control 1 did not suffer nerve damage. To cause the lesion in the sciatic nerve, compression was applied with a Kelly clamp for 6 s. The evaluation of sensory deficit was performed by the painful exteroceptive sensitivity (PES) and neuromotor tests by the SFI. Laser 660 nm and laser 808 nm sub-groups were irradiated daily (100 mW, 40 s, energy density of 133 J/cm²). The sciatic nerve segment was removed for RS analysis. The animals showed accentuated sensory and neurofunctional deficit after injury and their rehabilitation occurred more effectively in the sub-groups treated with 660 nm laser. Control 2 sub-group did not obtain functional recovery of gait. The RS identified sphingolipids (718, 1065, and 1440 cm^-1) and collagen (700, 852, 1004, 1270, and 1660 cm^-1) as biomolecular characteristics of sciatic nerves. Principal component analysis revealed important differences among sub-groups and a directly proportional correlation with SFI, mainly in the sub-group laser 660 nm treated for 21 days. In the axonotmesis-type lesion model presented herein, the 660 nm laser was more efficient in neurofunctional recovery, and the Raman spectra of lipid and protein properties were attributed to the basic biochemical composition of the sciatic nerve.