Wavelength Of Laser Radiation Research Articles

Interference mechanism of plasma self-organization in transparent dielectrics under the intense femtosecond laser pulse exposure

A new mechanism of plasma self-organization in transparent dielectrics with wide bandgap exposed to the intense tightly focused laser radiation was revealed, which causes the generation of 3D periodic ring structures with subwavelength period both along the laser pulse propagation and in the radial direction. The mechanism involves formation of dense plasma burst in the pre-focal region that provides efficient scattering of the incident wave. The interference of a plane incident laser wave in the focal region and a divergent reflected one will form the standing wave pattern with local minima and maxima of laser field both in the direction of the incident wave propagation and perpendicular to it producing the ring patterns of effective ionization regions in the dielectric volume. Analytical and numerical simulations of the process of laser wave scattering on a near-spherical plasma object with dimensions both smaller and larger than the laser radiation wavelength are performed to verify the proposed model.

The bacterial flagellum as an object for optical trapping.

This letter considers the possibility of using the optical trap to study the structure and function of the microbial flagellum. The structure of the flagellum of a typical gram-negative bacterium is described in brief. A standard mathematical model based on the principle of superposition is used to describe the movement of an ellipsoidal microbial cell in a liquid medium. The basic principles of optical trapping based on the combined action of the light pressure and the gradient force are briefly clarified. Several problems related to thermal damage of living microscopic objects when the latter gets to the focus of a laser beam are shortly discussed. It is shown that the probability of cell damage depends nonlinearly on the wavelength of laser radiation. Finally, the model systems that would make it possible to study flagella of the free bacteria and the ones anchored or tethered on the surface of a solid material are discussed in detail.

Application of vacuum-laser therapy in complex treatment of chronic gingivitis

The high prevalence of chronic forms of gingivitis among young individuals is an urgent problem of modern dentistry, the solution of which requires new approaches and methods. Thus, this study aimed to investigate the clinical and functional state of the periodontium at the initial inflammatory processes in the tissues and its correction using physical methods of treatment. Clinical examination, index assessment, laser Doppler flowmetry, and video registration of vacuum test in a patient with chronic gingivitis revealed an increase in gingival capillary resistance and improvement of microcirculation in the periodontium at the end of vacuum therapy combined with exposure to laser radiation of red wavelength on periodontal tissues in the complex of standard treatment measures. The results of the functional methods of research after the end of physical influence on periodontal tissues are confirmed by the decrease of bleeding and increase of oral hygiene level according to the clinical instrumental examination and by the absence of patient complaints. Thus, the clinical case demonstrates the promising application of vacuum-laser therapy in the complex treatment of chronic gingivitis.

Влияние режимов лазерной наплавки на геометрические размеры стального трека

Introduction. Laser surfacing is one of the leading trends in the field of additive technologies, which consists in layer-by-layer build of material using a laser as an energy source. To obtain a high-quality product, it is necessary to select the optimal building parameters correctly. The problem is that such optimization is necessary for all equipment, since minor differences in its characteristics can make significant changes in the parameters of layer-by-layer build. In order to determine the optimal build mode, it is enough to analyze the effect of various equipment parameters on the characteristics of single tracks. Therefore, the purpose of this work is to determine the most important parameters of laser radiation that affect the surfacing process and the optimal mode for building a single track of chromium-nickel steel. The work investigated single tracks obtained by laser surfacing of powder from austenitic chromium-nickel steel AISI 316L. The optimization factors included such characteristics as laser power, beam speed, flow rate of supplied powder and laser spot size. The wavelength of laser radiation was 1.07 μm. Research methods. To determine the quality and geometric dimensions of single tracks, the macrostructure of cross sections of specimens was studied using metallography and scanning electron microscopy methods. Results and discussion. It is established that the optimal mode for growing single tracks of steel AISI 316L is characterized by a laser radiation power of 1,250 W and a scanning speed of 25 mm/s. In this case, the optimal powder consumption rate is 12 g/min, and the laser spot size is 4.1 mm. The work shows that the powder consumption and laser spot size have the greatest influence on the coefficient of effective use of powder material. By changing it, the surfacing performance can be increased by 10–15 %.

Examination of laser radiation effect on silk fabrics dyed with different concentrations of cochineal using iron and alum mordants

The present study was conducted to investigate the effect of laser radiation on the color of the silk fabric dyed with cochineal insects. Silk fabrics mordanted with ıron (II) sulfate (FeSO4.7H2O) and potassium aluminum sulfate (KAl(SO4)212.H2O) at different ratios were separately dyed at different concentrations using 5%, 7.5% and 10% owf of cochineal (Dactylopius coccus Costa). Then, by applying two different wavelengths of laser radiation with different pulses to the dyed silk fabric samples, the modification of the laser radiation on the fiber and dye on the fabric was examined. During laser radiation applications, a thermal infrared camera was used to measure temperature changes. The dyed fabrics were analyzed by different analytical and technical methods. The color characteristics of all the dyed silk fabrics were measured by CIEL*a*b* spectrophotometer. The color coordinates and fastness values of rubbing and light also were investigated. Morphological analysis was performed using optical and scanning electron microscopy. Elemental analysis was performed using SEM-EDX (scanning electron microscopy -energy-dispersive X-ray spectroscopy) to identify mordants. A reserved phase high-performance liquid chromatography (RP-HPLC) with the diode-array detection (DAD) method was utilized for the identification of the components of dyes present in the silk samples.

PtTe2 photodetectors with negative photoconductivity under different wavelength laser irradiation

Platinum telluride (PtTe2), as a newly emerged type II Dirac semimetal, has attracted much attention. Due to its excellent linear dispersive band structure and ultra-high carrier mobility, PtTe2 show great potential in the new quantum phenomena, topological phase transitions, unconventional superconductivity and other photodetecting fields. In this paper, we report the negative photoelectric effect of photodetectors based on the type II Dirac semimetal PtTe2 film under the laser irradiation of 405 nm, 532 nm and 808 nm. Under the condition of applying 1 V voltage, the R of the PtTe2 device under 405 nm laser irradiation was 20 A/W and the D* was 6.9×109 Jones; the R of the PtTe2 device under 532 nm laser irradiation was 1.3 A/W and the D* was 4.1×108 Jones; the R of the PtTe2 device under 808 nm laser irradiation was 0.6 A/W and the D* was 2.1×108 Jones. Under normal atmospheric pressure and room temperature conditions, we observed a negative photoconductivity phenomenon for the PtTe2 device, where the change in photoconductivity is attributed to the light-induced desorption of O or H2O molecules from the surface of the material. In addition, a single-site scanning imaging system based on a PtTe2 photodetector was designed to test the detection capability of the device. The analysis of the photocurrent effect produced by the PtTe2 device further deepens the understanding of the photoconductivity mechanism in the field of photodetection.

Photodynamic therapy repairs medication-related osteonecrosis of the jaw by reducing NF-kB protein in rats.

To evaluate whether antimicrobial photodynamic therapy (aPDT) repairs bisphosphonate-related osteonecrosis of the jaw (BRONJ) modulated by the reduction of NF-kB protein in a murine model. Male Wistar rats (N=30) were divided into the following groups (n=6/group): negative control (NC); experimental osteonecrosis (ONE); ONE + photosensitizer (PS); ONE + photobiomodulation (PBM); and ONE + aPDT. Over 8 weeks, ONE was induced by zoledronic acid 250 µg/kg injections, except in the NC group, which received sterile 0.9% saline, followed by extraction of the lower left first molar. Red light laser irradiation (wavelength ~660 nm, power 50 mW, energy of 2 J, energy dose of 66.67 J/cm2 for 40 s) was performed once a week for 4 weeks. Methylene blue 0.3% was used as PS. The animals were euthanized and examined macroscopically for the presence of exposed bone and epithelial repair and microscopically by histochemical (hematoxylin-eosin and Masson's trichrome staining) and immunohistochemical (anti-NF-kB) methods. Macroscopic and histomorphometric data were analyzed by one-way ANOVA and Tukey's post-test (p<0.05). Mucosal repair, viable osteocytes, and NF-kB immunostaining were observed in the NC, ONE+PS, ONE+PBM, and ONE+aPDT groups. The ONE group showed no mucosal repair, showing empty lacunae and multifocal immunostaining for NF-kB. The ONE+PBM and ONE+aPDT groups had greater deposition of extracellular matrix and less necrotic bone tissue (p<0.05). PBM and aPDT treatments for BRONJ were effective for bone and epithelial repair, in addition to reducing inflammation mediated by the decrease of NF-kB protein in the irradiated regions.

Effectiveness of Complex Medical Rehabilitation of Patients with Postthrombophlebitic Syndrome of Lower Extremities and Obesity: a Randomized Clinical Study

INTRODUCTION. The relevance of the development of comprehensive rehabilitation programmes for patients with postthrombophlebitic syndrome (PTPS) is due to the high frequency of disability and a significant reduction in their quality of life. Since obesity and excessive body weight are proven risk factors for the development and progression of chronic vein diseases, weight reduction is one of the important tasks of rehabilitation measures in patients with PTPS and concomitant obesity.&#x0D; AIM. Comparative study of the influence of complex methods of medical rehabilitation, including various methods of laser blood irradiation (supravascular and intravenous), pulse magnetotherapy and dry carbon baths, on the dynamics of indicators of composite body composition according to bioimpedance measurements in patients with postthrombophlebitic syndrome of the lower extremities and obesity.&#x0D; MATERIALS AND METHODS. A randomized prospective study was conducted on the basis of the Department of Medical Rehabilitation of Patients with Somatic Diseases of National Medical Research Center of Rehabilitation and Balneology of the Ministry of Health of Russia. The study included 40 patients with PTS of the lower extremities and accompanying obesity, the average age of which was 58.3 [51.5; 68.0] year), randomized to two groups. The patients of the 1st group received Intravenous laser blood irradiation (ILIB) (“Lazmik”, Russia), impulse magnetotherapy and dry carbon baths, as well as therapeutic gymnastics in the hall. The patients of the 2nd group received a complex that included supravascular laser irradiation of blood (“Azor-2K”, Russia), pulse magnetic therapy, and dry carbon baths, as well as therapeutic gymnastics in the gym. Anthropometric measurements (body mass, malleolar volume) were used for the evaluation of anti-edema and lipolytic effects after a comprehensive course of medical rehabilitation, as well as bioimpedance measurement of body composition (“MEDASS”, Russia).&#x0D; RESULTS. In patients with PTS of the lower extremities and obesity, after carrying out a course of medical rehabilitation using preformed physical factors, including various methods of laser irradiation of the blood (supravascular and intravenous), a significant decrease in body weight indicators was observed (p 0.001), a decrease in BMI (p 0.001), total and extracellular fluid (p 0.001) without significant differences between groups. A significant decrease in the index of fat mass (kg) (p = 0.007) was found in patients of the main group.&#x0D; DISCUSSION. Maintaining a healthy body weight as well as combating obesity are first-line secondary prevention measures recommended for all patients with PTS of the lower extremities. For the control of the dynamics of the composite composition of the body, an effective and sensitive method is the method of bioimpedance measurement, which allows to estimate the reduction of extracellular fluid (anti-flow effect) and fat mass of the body (lipolytic effect).&#x0D; CONCLUSION. The method of bioimpedance measurement, used for the evaluation of the composite composition of the body, showed high sensitivity and allowed to establish the greater effectiveness of the developed complex, which includes ILIB with a wavelength of low-intensity laser radiation (NILI) of 635 nm in reducing fat mass.

Effect of Nd:YAG pulsed laser on the antibacterial activity and physical properties of newly synthesized composites, CdO/Co3O4 and Ag/CdO/Co3O4

Two compounds were prepared: cadmium oxide/cobalt oxide (referred to as oxide A) and silver decorated cadmium oxide/cobalt oxide (referred to as oxide B). Yttrium aluminium garnet (Nd:YAG) lasers, doped with neodymium, were used to irradiate the samples at 532 nm and 1064 nm. The effect of the Nd:YAG laser on the morphological, optical, structural, and antibacterial properties was investigated. The XRD data shows that both oxides are polycrystalline, and the laser irradiation increases the crystal size. Additionally, scanning electron microscopy results (SEM) show that particle size increases with laser irradiation and laser wavelength. While both oxides expand under the influence of a laser, oxide A has a larger optical band gap than oxide B. The intensity of PL increases with the pulsed laser effect and the addition of Ag. The antibacterial test shows that silver is quite effective in eliminating germs and other harmful microbes for human health. Moreover, the results show that, after adjusting the other laser parameters, the wavelength of 1064 nm performed better compared to the wavelength of 532 nm in pure water.

Photodynamic therapy for arthritis: A promising therapeutic strategy

AbstractPhotodynamic therapy (PDT) is a novel therapy that combines photosensitizers, light, and oxygen molecules to treat diseases such as joint lesions and microbial infections through photodynamic reactions. The photosensitizers are activated under specific wavelengths of laser radiation to generate reactive oxygen species, which alter the microenvironment of the diseased tissue, cause ischemia and target cell death, and thus effectively treat cancer. Now that there is growing evidence that nonlethal doses of PDT reduce inflammation and treat infections in multiple animal models of arthritis, PDT should be considered as a new option for the treatment of arthritis. This article presents a literature review of published original articles and review articles concerning photodynamic therapy and arthritis. We conducted a comprehensive literature search in PubMed, Web of Science and Google Scholar databases, excluding duplicated and irrelevant studies. In cases of duplicated research, we selected articles with higher impact factors for the review. In this review, we summarize the application and progress of PDT in the treatment of rheumatoid arthritis, osteoarthritis, psoriatic arthritis, and infectious arthritis, and clarify the advantages and limitations of PDT for arthritis. PDT offers therapeutic value for patients with inflammatory and infectious arthritis through promoting vascular occlusion, cell death, and antibacterial therapy.

The Use of Multi-Probe Modulated Laser Radiation for the Identification of Substances' Clots in the Fluid Flow

Modern tools of water supply systems monitoring at enterprises or in the housing sector use laser liquid sensing systems. In this case, as a rule, laboratory analyses of the obtained liquid samples are used, as well as spectral analysis methods when scanning the liquid with light for different wavelengths. These approaches do not allow for real-time analysis of a moving fluid flow (flow analysis). The paper considers a version for constructing of a system for online detecting and identifying emergency clots of pollutants in a liquid stream using laser radiation. The basic principles of the system construction, the block diagram of the system structure and parameters for identification of clots of substances under study flowing in the pipelines of the sewage or water treatment system at industrial enterprises are given. When constructing the system, several wavelengths of laser radiation are used, simultaneously directed to the one point of the studied clot of the studied fluid flow. Light wavelengths are determined at the stage of preparation for the study. At this initial stage of the process, optical transmission spectra of substances that are a priori possible in the studied fluid flow are analyzed. The main criterion for wavelengths choose is difference in substances optical transmission spectra at the se selected wavelengths. For the possibility of technical separation of signals at different wavelengths of the emitting radiation, the radiation fluxes are modulated. Creation of standards for identification substances in fluid flow clusters is carried out in the form of lattice functions containing the components of the substance optical transmission spectrum at certain wavelengths of laser radiation. Modulation of radiation is proposed to be carried out by controlling the pumping of each emitters of the system. The proposed system will find application in the oil and gas, processing industry, water filtration and purification systems, industrial enterprises and agricultural processing enterprises.

Optical Properties of Light-Scattering Standards for CCD Photometry.

This paper analyzes the light-scattering standards currently used for calibration (verification) and systematic research in photo and spectrophotometry tools. The application specificities in studying the diffuse reflected and transmitted light during biomedical CCD photometry are considered. The advantages of a new class of photometers with non-spherical reflectors as ellipsoids of revolution truncated along the focal planes with the internal mirror surface are presented. The ellipsoid first focal plane is combined with the surface of the under-study media, and the second is optically coupled to the CCD image sensor plane. The principles of zone analysis of spatial distribution reproduced in photometric images on a CCD sensor are substantiated. The illuminance levels of photometric image areas in reflected and transmitted light from the thickness of the standard for the wavelength of laser radiation of 650 nm of different power was experimentally investigated. Polynomial dependences were obtained, and regression coefficients of the illuminance of the external and middle rings in photometric images for the reflected and transmitted light on the laser power were determined.

Variation of Nonlinear Refraction and Three-Photon Absorption of Indium-Tin Oxide Quantum Dot Thin Films and Solutions in Near Infrared Range.

We characterize the nonlinear optical properties of indium-tin oxide (ITO) quantum dots (QDs) in the IR range using the Z-scan method. We present results of three-photon absorption (3PA), third harmonic generation (3HG), and Kerr-effect-induced nonlinear refraction in ITO QDs. Z-scan measurements were carried out for the QDs solution, while 3HG was demonstrated using QD thin films. The Kerr-induced nonlinear refractive index was analyzed along the 800-950 nm range showing an increase in this parameter from -6.7 × 10-18 to -1.5 × 10-17 m2 W-1. At longer wavelengths (1000-1100 nm), the higher-order effects started to contribute to a nonlinear refractive index. The 3PA coefficient at 950 nm was measured to be 1.42 × 10-25 m3/W2. We discuss the peculiarities in the wavelength-dependent variation of the coefficient of nonlinear absorption responsible for 3PA in the range of 800-1150 nm. Third harmonic generation was analyzed in the 1200-1550 nm spectral range. The absolute value of 3HG conversion efficiency in the 150 nm thick film at the wavelength of laser radiation (1350 nm) was estimated to be ~10-5.

High Harmonic Generation near the Low-Frequency Edge of a Plateau under Nonlinear Propagation of 1.24-μm Near-Infrared Femtosecond Laser Radiation in a Dense Argon Jet

High (15–25) harmonic generation in the vacuum ultraviolet spectral range (83–50 nm) has been realized by focused (NA = 0.033) near-infrared femtosecond laser radiation (wavelength λ = 1.24 μm) with a vacuum intensity of ~7.5 × 1014 W/cm2 irradiating a dense gas jet. It has been shown experimentally that the use of such a high-numerical aperture focusing requires high (up to 10 bar) gas jet pressures to optimize phase matching. The use of the dense gas jet results in a noticeable manifestation of nonlinear propagation effects for generating radiation, which affect the generation process through the change in the phase matching conditions. Furthermore, it has been shown that the prechirping of the generating pulse makes it possible to compensate a chirp appearing due to self-phase modulation and to increase the harmonic generation efficiency because of the nonlinear compression of the generating pulse. This approach has allowed 17th (73 nm) harmonic generation with an energy of 2 pJ in a pulse and a generation efficiency of 5.4 × 10–9. The estimates obtained have shown that this radiation can be used for single-pulse maskless photolithography in the extreme ultraviolet range.

Clinical outcomes of diode laser as an adjunct to nonsurgical periodontal therapy for residual periodontal pockets in mandibular second molars-a randomized controlled clinical trial.

The aim of this study was to evaluate the clinical outcomes of diode laser as an adjunct to nonsurgical periodontal therapy (NSPT) for residual periodontal pockets in mandibular second molars. Sixty-seven mandibular second molars (154 residual periodontal pockets) were recruited into the study and randomly assigned to the Laser + NSPT group and the NSPT group. The Laser + NSPT group underwent NSPT adjunct with diode laser radiation (wavelength: 810nm, power: 1.5 W, 40s maximum), while the NSPT group underwent nonsurgical periodontal therapy alone. Clinical parameters were measured at baseline (T0) and 4(T1), 12(T2), and 24(T3), weeks after treatment. Periodontal pocket depth (PPD), clinical attachment loss (CAL), and bleeding on probing (BOP) in both groups showed significant improvements at the end of study compared to baseline. The reductions of PPD, CAL, and BOP in the Laser + NSPT group were significantly greater than NSPT group. At T3, the Laser + NSPT group had a mean PPD of 3.06 ± 0.86mm, CAL of 2.58 ± 0.94mm and BOP of 15.49%, while the NSPT group had a mean PPD of 4.46 ± 1.57mm, CAL of 3.03 ± 1.25mm and BOP of 64.29%. The diode laser as an adjunct to nonsurgical periodontal therapy may contribute to clinical outcomes for residual periodontal pockets. However, the approach may cause reductionof keratinized tissue width. This study was registered in the Chinese Clinical Trial Registry ChiCTR2200061194. Diode laser as an adjunct to nonsurgical periodontal therapy may contribute to the clinical outcomes for residual periodontal pockets in mandibular second molars.

Surface Vertical Multi-Emission Laser with Distributed Bragg Reflector Feedback from CsPbI3 Quantum Dots.

Quantum dots (QDs) laser has become an important way to solve micro-application problems in many fields. However, single wavelength distributed Bragg reflector (DBR) has many limitations in practical applications, such as signal transmission. How to realize multiwavelength DBR lasing output simply is a challenge. To achieve a stable multi-wavelength quantum dots laser in the near-infrared region, the perovskite CsPbI3 QDs laser with DBR structure is developed in this paper. A tetragonal crystal structure with complete bonding information and no defect is explained by X-ray diffractions (XRD) and Raman spectrum. The cross-section morphology of the DBR laser and the surface morphology of QDs is measured by scanning electron microscope (SEM) and transmission electron microscope (TEM), respectively. An elliptical light propagation field and a double wavelength laser radiation are obtained from the finite-difference time-domain (FDTD) simulation. The output of the three wavelength lasers at 770 nm, 823 nm, and 873 nm is measured. The emission time of a DBR laser is about 2 h, and the average fluorescence quantum yield is 60%. The cavity length selection and energy level model are put in place to clearly see the working mechanism. All the results suggest that an effective and stable CsPbI3 quantum dots DBR laser is realized.

Effect of post laser annealing on stacked structure of CZTS thin film solar cells

Cu2ZnSnS4 (CZTS) is an attractive material for thin film solar cells because all its constituents are Earth-abundant elements, and it’s a direct transition semiconductor with a band gap energy of 1.5 eV that is suitable for absorbing solar light spectrum effectively. CZTS is generally formed by precursor formation followed by heat treatment at 500 °C–600 °C to enhance the growth of crystal grain. In this work, a novel CZTS crystal grain re-growth process using post-laser annealing was investigated. 445 nm wavelength laser irradiation was performed on the Al-doped ZnO/CdS/CZTS/Mo/substrate stacked structure. X-ray diffraction and scanning microscope showed the CZTS crystal grain enlargement. Solar cells were fabricated on those structures and the external quantum efficiency was found to be improved especially at 500–1000 nm wavelength light absorption. That resulted in a short circuit current improvement.

Conditioning of Scots pine (Pinus sylvestris L.) sowing material

ABSTRACT Scots pine is the main forest forming species in Poland. Despite the great importance of natural reconditioning of forest trees, a substantial source of reforestation is the nursery production of seedling material. Pre-sowing seed conditioning, consisting of chemical and physical treatments, is commonly used to improve seed quality as well as to advance uniform development and increase plant efficiency. The influence of semiconductor laser irradiation wavelength on Scots pine seeds (Pinus sylvestris L.) was tested in both laboratory and pot experiments. Irradiation rates used in trials were (D3) three-, (D6) six- and (D9) nine-fold of the basic rate of 2.5·10−1 J·cm−2 with a control (D0) of non-irradiated seeds. Irradiation accelerated emergence and increased seedling numbers. The germination energy and capacity of tested Scots pine genotypes were reduced under higher (D6) doses of laser irradiation. Stimulation of morphological traits and increase in chlorophyll contents was observed under the lowest (D3) irradiation rate, while an increase in polyphenol contents occurred under the highest, nine-fold rate of irradiation.

Femtosecond laser Wavelength-Dependent formation of plasmonic gold nanostructures

Complex gold nanostructures fabricated on the surface of metal have a high potential for being used as plasmonic nanostructures. The precise shape and dimensions management of the structures enables accurate control of plasmonic properties. In this work, the formation of gold nanobumps, nanocones, and nanojets by laser direct writing technique was investigated using different laser wavelengths by changing harmonics. The used wavelength of laser irradiation impacts the size and shape of the formed structures. Additionally, the achievable minimal grating period, the layer modification fluence, and the formation fluence range change with the used laser harmonic. Experiments indicate that the reduction of the wavelength provides a more precise fabrication process and management of properties. The gratings of the wavelength-dependent nanostructures excite surface lattice resonances with high quality and have significant potential for practical uses.

Comparative evaluation of photobiomodulation therapy at 660 and 810 nm wavelengths on the soft tissue local anesthesia reversal in pediatric dentistry: an in-vivo study.

Local anesthesia has been reliably used to control pain during dental procedures and is important in pediatric dentistry. However, children occasionally complain of prolonged numbness after dental treatment, leading to several problems. Studies conducted to reverse the effect of local anesthesia using phentolamine mesylate and photobiomodulation therapy (PBM) are encouraging but limited. PBM is a type of light therapy that utilizes visible and near-infrared non-ionizing electromagnetic spectral light sources. Hence, this study used this modality to compare the reversal of local anesthesia at two different wavelengths. This study compared the effect of PBM at 660 and 810 nm wavelengths on the reversal of soft tissue local anesthesia using a diode LASER in pediatric dentistry. Informed consent and assent were obtained, and the participants were then divided randomly into three groups of 20 children each: control group-without LASER irradiation, LASER irradiation at 660 nm, and LASER irradiation at 810 nm. Sixty children aged 4-8 years with deciduous mandibular molars indicated for pulp therapy were administered an inferior alveolar nerve block. After 45 min of injection, a duration that was similar to the approximate duration of treatment, they were exposed to 660- and 810-nm LASER irradiation according to their groups until reversal of local anesthesia was achieved. The control group did not undergo LASER irradiation. The reversal of the soft tissue local anesthetic effect was evaluated using palpation and pin prick tests every 15 min, and the LASER irradiation cycle continued until reversal of the soft tissue local anesthesia was achieved. A significant reduction of 55.5 min (27.6%) in the mean soft tissue local anesthesia reversal time was observed after the application of 810 nm wavelength PBM and 69 min (34.7%) after 660 nm wavelength LASER irradiation. PBM with a 660 nm wavelength was more effective in reducing the mean soft tissue local anesthesia reversal duration, and thus can be used as a reversal agent for soft tissue local anesthesia in pediatric dentistry.