The effect of near-infrared MLS laser radiation on cell membrane structure and radical generation

The therapeutic effects of low-power laser radiation of different wavelengths and light doses are well known, but the biochemical mechanism of the interaction of laser light with living cells is not fully understood. We have investigated the effect of MLS (Multiwave Locked System) laser near-infrared irradiation on cell membrane structure, functional properties, and free radical generation using human red blood cells and breast cancer MCF-4 cells. The cells were irradiated with low-intensity MLS near-infrared (simultaneously 808 nm, continuous emission and 905 nm, pulse emission, pulse-wave frequency, 1,000 or 2,000 Hz) laser light at light doses from 0 to 15 J (average power density 212.5 mW/cm², spot size was 3.18 cm²) at 22 °C, the activity membrane bound acetylcholinesterase, cell stability, anti-oxidative activity, and free radical generation were the parameters used in characterizing the structural and functional changes of the cell. Near-infrared low-intensity laser radiation changed the acetylcholinesterase activity of the red blood cell membrane in a dose-dependent manner: There was a considerable increase of maximal enzymatic rate and Michaelis constant due to changes in the membrane structure. Integral parameters such as erythrocyte stability, membrane lipid peroxidation, or methemoglobin levels remained unchanged. Anti-oxidative capacity of the red blood cells increased after MLS laser irradiation. This irradiation induced a time-dependent increase in free radical generation in MCF-4 cells. Low-intensity near-infrared MLS laser radiation induces free radical generation and changes enzymatic and anti-oxidative activities of cellular components. Free radical generation may be the mechanism of the biomodulative effect of laser radiation.     

Central nervous system transplantation benefitted by low-power laser irradiation

The effect of low-power laser irradiation on mammalian central nervous system (CNS) transplantation is reported. Fetal brain allografts were transplanted into the brain (fornix region) of 20 adult rats and spinal cord allografts were transplanted into the spinal cord of eight dogs. For 21 days, the closed operated wounds of 10 rats and four dogs were exposed daily to transcutaneous low-power laser irradiation cw HeNe laser (16 mW, 632.8 nm, spot size 2 mm², energy density of 30 J cm⁻² for rats and 70 J cm⁻² for dogs). This study shows that the low-power laser irradiation prevents extensive glial scar formation (a limiting factor in CNS regeneration) between neural transplants and host brain or spinal cord. Abundant capillaries developed in the laser-irradiated transplants, this being of crucial importance for their survival. The results of the present study and our previous investigations suggest that low-power laser irradiation is a novel tool for treatment of CNS injuries and disorders.     

Effect of low-power laser irradiation on cell growth and procollagen synthesis of cultured fibroblasts

BACKGROUND AND OBJECTIVES: In dentistry, low-power lasers have been used in the treatment of dentin hypersensitivity, gingivitis, periodontitis, and different forms of oral ulcers. This in vitro study focuses on the biostimulation of NIH-3T3 fibroblasts by a low-power Ga-As-pulsed laser. STUDY DESIGN/MATERIALS AND METHODS: We have studied cell growth and procollagen synthesis of cultured fibroblasts submitted to low-power laser irradiation with energy densities varying from 3 to 5 J/cm(2) over a period of 1-6 days. The light source was a 120 mW Ga-As diode laser (lambda = 904 nm). Growth curves and procollagen immunoprecipitation were obtained. RESULTS: Irradiation of 3 and 4 J/cm(2) increased the cell numbers about threefold to sixfold comparing to control cultures. However, this effect was restricted to a small range of energy densities since 5 J/cm(2) had no effect on cell growth. The energy density of 3 J/cm(2) remarkably increased cell growth, with no effect on procollagen synthesis, as demonstrated by the immunoprecipitation analysis. CONCLUSIONS: Our results showed that a particular laser irradiation stimulates fibroblast proliferation, without impairing procollagen synthesis.     

Effects of nimodipine and dexamethasone on low-level co2 laser-induced release of 51chromium from canine 2c5 gliosarcoma cells

Low-energy penumbral irradiation of surgical lasers may produce undesirable effects on surrounding tissues. This study used a ⁵¹Cr cell labeling technique to determine if gliosarcoma cells could be therapeutically protected prior to their exposure to low-power laser irradiation. Canine 2C5 gliosarcoma cells with intra-cellular ⁵¹Cr were treated with nimodipine and/or dexamethasone and then exposed to low-power levels of CO₂ laser. The ⁵¹Cr was released from the cells in a dose-dependent fashion following exposure to laser energy. Correlative analysis of the data indicated that a strong direct relationship between laser fluence and ⁵¹Cr release did exist for controls and drug-treated groups with coefficients of correlation r ≥ +0.90 and coefficients of determination r² ≥ 0.82. However, comparison of the data from the drug-treated and control groups found that there was no significant difference between them (P >.05). Therefore, no protective or detrimental effects were observed with the use of nimodipine and/or dexamethasone on the gliosarcoma cells as tested in this system. Further investigation is necessary in order to define the mechanisms by which low-power level lasers affect these cells. These effects do not appear to be mediated through localization of mechanisms to the cell membranes or their constituent Ca²⁺channels. © 1994 Wiley-Liss, Inc.     

Effect of low-energy laser irradiation on colony formation capability in different human tumor cells in vitro

Fibroblasts and lymphocytes are the most widely used cells for studying the so-called biostimulative effect of low-power laser in vitro. In contrast, stimulation of cancer cells by laser light has not been investigated extensively. The present study attempted to evaluate whether or not human tumor cells could exhibit an increase in colony-forming capability following low-watt laser irradiation. LoVo and HT29 (colon carcinoma), MCF7 (breast carcinoma), M14 and JR1 (malignant melanoma) cell lines were irradiated at different doses of light delivered from an argon or an argon-dye laser. Radiant exposures between 4.2 and 150 kJ/m² at irradiances ranging from 35 to 500 W/m² were delivered. Results were mixed. Of the 41 experiments performed, five showed a significant statistical increase in the number of colonies (P< 0.05), whereas three showed a decrease (P < 0.05). Nevertheless, the trend of most data was toward an increase in colony formation, and Wilcoxon's signed-ranks test suggested that light increases tumor cell culture growth (P < 0.03).     

Comparison of the photodynamic fungicidal efficacy of methylene blue, toluidine blue, malachite green and low-power laser irradiation alone against Candida albicans

This study was to evaluate specific effects of photodynamic therapy (energy density 15.8 J/cm², 26.3 J/cm² and 39.5 J/cm²) using methylene blue, toluidine blue and malachite green as photosensitizers and low-power laser irradiation on the viability of Candida albicans. Suspensions of C. albicans containing 10⁶ cells/ml were standardized in a spectrophotometer. For each dye, 120 assays, divided into four groups according to the following experimental conditions, were carried out: laser irradiation in the presence of the photosensitizer; laser irradiation only; treatment with the photosensitizer only; no exposure to laser light or photosensitizer. Next, serial dilutions were prepared and seeded onto Sabouraud dextrose agar for the determination of the number of colony-forming units per milliliter (CFU/ml). The results were subjected to analysis of variance and the Tukey test (P < 0.05). Photodynamic therapy using the photosensitizers tested was effective in reducing the number of C. albicans.. The number of CFU/ml was reduced by between 0.54 log₁₀ and 3.07 log₁₀ and depended on the laser energy density used. Toluidine blue, methylene blue and malachite green were effective photosensitizers in antimicrobial photodynamic therapy against C. albicans, as was low-power laser irradiation alone.     

The effect of polarized light on the organization of collagen secreted by fibroblasts

Recent studies have demonstrated the beneficial effect of low-power lasers and polarized light on wound healing, inflammation, and the treatment of rheumatologic and neurologic disorders. The overall effect of laser irradiation treatment is still controversial due to the lack of studies on the biochemical mechanisms and the optimal parameters for the incident light that should be chosen for particular applications. Here, we study how NIH/3T3 fibroblasts respond to irradiation with linearly polarized light at different polarization angles. In particular, we examined vascular endothelial growth factor (VEGF) secretion, differentiation to myofibroblasts, and collagen organization in response to 800 nm polarized light at 0°, 45°, 90°, and 135° with a power density of 40 mW/cm² for 6 min every day for 6 days. Additional experiments were conducted in which the polarization angle of the incident was changed every day to induce an isotropic distribution of collagen. The data presented here shows that polarized light can upregulate VEGF production, myofibroblast differentiation, and induce different collagen organization in response to different polarization angles of the incident beam. These results are encouraging and demonstrate possible methods for controlling cell response through the polarization angle of the laser light, which has potential for the treatment of wounds.     

Comparative effects of wavelengths of low-power laser in regeneration of sciatic nerve in rats following crushing lesion

Peripheral nerves are structures that, when damaged, can result in significant motor and sensory disabilities. Several studies have used therapeutic resources with the aim of promoting early nerve regeneration, such as the use of low-power laser. However, this laser therapy does not represent a consensus regarding the methodology, thus yielding controversial conclusions. The objective of our study was to investigate, by functional evaluation, the comparative effects of low-power laser (660 nm and 830 nm) on sciatic nerve regeneration following crushing injuries. Twenty-seven Wistar rats subjected to sciatic nerve injury were divided into three groups: group sham, consisting of rats undergoing simulated irradiation; a group consisting of rats subjected to gallium–aluminum–arsenide (GaAlAs) laser at 660 nm (10 J/cm², 30 mW and 0.06 cm² beam), and another one consisting of rats subjected to GaAlAs laser at 830 nm (10 J/cm², 30 mW and 0.116 cm²). Laser was applied to the lesion for 21 days. A sciatic functional index (SFI) was used for functional evaluation prior to surgery and on days 7, 14, and 21 after surgery. Differences in SFI were found between group 660 nm and the other ones at the 14th day. One can observe that laser application at 660 nm with the parameters and methods utilised was effective in promoting early functional recovery, as indicated by the SFI, over the period evaluated.     

Effect of blood on lethal photosensitization of bacteria in subgingival plaque from patients with chronic periodontitis

The purpose of this study was to determine whether bacteria in subgingival plaque samples from patients with chronic periodontitis could be sensitized to killing by low-power laser light in the presence of blood. Toluidine blue O (45 μg ml⁻¹) was added to the plaque samples which were then exposed to light from a 7.3 mW HeNe laser for 30 or 120 s in the presence and absence of 10% horse blood. Viable counts of various groups and species of bacteria were determined before and after irradiation. A substantial bactericidal effect was obtained after irradiation for 30s regardless of whether or not blood was present. However, in most cases irradiation in the absence of blood resulted in greater decreases in the viable counts of aerobes, anaerobes, streptococci and blackpigmented anaerobes. When the samples were irradiated for 120s, 10% blood had little effect on the kills attained and elimination of periodontopathogenic species (black-pigmented anaerobes andFusobacterium nucleatum) was achieved both in the presence and absence of blood.     

Helium-Neon laser irradiation inhibits the growth of kidney epithelial cells in culture

We have investigated the in vitro action of helium-neon (He-Ne) laser light on the cell cycle and the growth of rat kidney epithelial cell cultures. Dose-response studies showed that repeated He-Ne irradiation (dose rate 40 mW/cm²) once a day in a dose range between 11.9 and 142 J/cm² significantly inhibited cell growth, while daily irradiation with 4.7 J/cm² had no effect. Microscopic examination of nuclear spreads revealed an increased number of cells in mitosis after a single irradiation with 142 J/cm². These results support previous observations suggesting that laser light of low thermal energy interferes with cell cycling and may inhibit cell growth when irradiation is performed at doses of 11.9 J/cm² or more.     

Activation of latent TGF-β1 by low-power laser in vitro correlates with increased TGF-β1 levels in laser-enhanced oral wound healing

The term Laser "Photobiomodulation" was coined to encompass the pleiotropic effects of low-power lasers on biological processes. The purpose of this study was to investigate whether transforming growth factor (TGF)-beta had a role in mediating the biological effects of low-power far-infrared laser irradiation. We assayed for in vitro activation using various biological forms of cell-secreted, recombinant, and serum latent TGF-beta using the p3TP reporter and enzyme-linked immunosorbent assays. We demonstrate here that low-power lasers are capable of activating latent TGF-beta1 and -beta3 in vitro and, further, that it is capable of "priming" these complexes, making them more amenable to physiological activation present in the healing milieu. Using an in vivo oral tooth extraction-healing model, we observed an increased TGF-beta1, but not beta3, expression by immunohistochemistry immediately following laser irradiation while TGF-beta3 expression was increased after 14 days, concomitant with an increased inflammatory infiltrate. All comparisons were performed between laser-irradiated wounds and nonirradiated wounds in each subject essentially using them as their own control (paired T-test p<0.05). Low-power laser irradiation is capable of activating the latent TGF-beta1 complex in vitro and its expression pattern in vivo suggests that TGF-beta play a central role in mediating the accelerated healing response.     

Laser irradiation affects enzymatic antioxidant system of streptozotocin-induced diabetic rats

The aim of the present study was to analyze the effect of low-power laser irradiation in the antioxidant enzymatic system of submandibular (SMG) and parotid (PG) salivary glands of streptozotocin-induced diabetic rats. The animals were randomly divided into six groups: three diabetic groups (D0, D5, and D20) and three non-diabetic groups (C0, C5, and C20), according to laser dose received (0, 5, and 20 J/cm², respectively). Areas of approximately 1 cm² were demarcated in the salivary glands (each parotid and both submandibular glands) and after irradiated according to Simões et.al. (Lasers Med Sci 24:202–208, 2009). A diode laser (660 nm/100 mW) was used, with laser beam spot of 0.0177 cm2. The group treated with 5 J/cm² laser dose was subjected to irradiation for 1 min and 4 s (total irradiation time) and the group treated with 20 J/cm² laser dose was subjected to irradiation for 4 min and 16 s. Twenty-four hours after irradiation the animals were euthanized and the salivary glands were removed for biochemical analysis. The total antioxidant values (TA), the activity of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase enzymes were determined. SOD and CAT activities, as well as TA were higher in SMG of irradiated diabetic rats. However, in SMG of non-diabetic rats, laser irradiation decreased TA values and led to an increase in the CAT activity. In addition, there was a decrease in the activity of CAT in PG of diabetic and non-diabetic animals after laser irradiation. According to the results of the present study, low-power laser irradiation can affect the enzymatic antioxidant system of salivary glands of streptozotocin-induced diabetic rats.     

Low-level Er:YAG laser irradiation enhances osteoblast proliferation through activation of MAPK/ERK

Although the use of high-level Er:YAG laser irradiation has been increasing in periodontal and peri-implant therapy, the effects of low-level Er:YAG laser on surrounding tissues and cells remain unclear. In the present study, the effects of low-level Er:YAG laser irradiation on osteoblast proliferation were investigated. Cells of the osteoblastic cell line MC3T3-E1 were treated with low-level Er:YAG laser irradiation with various combinations of laser settings (fluence 0.7–17.2 J/cm²) and in the absence or presence of culture medium during irradiation. On day 1 and/or day 3, cell proliferation and death were determined by cell counting and by measurement of lactate dehydrogenase (LDH) levels. Further, the role of mitogen-activated protein kinase (MAPK) pathways in laser-enhanced cell proliferation was investigated by inhibiting the MAPK pathways and then measuring MAPK phosphorylation by Western blotting. Higher proliferation rates were found with various combinations of irradiation parameters on days 1 and 3. Significantly higher proliferation was also observed in laser-irradiated MC3T3-E1 cells at a fluence of approximately 1.0–15.1 J/cm², whereas no increase in LDH activity was observed. Further, low-level Er:YAG irradiation induced the phosphorylation of extracellular signal-regulated protein kinase (MAPK/ERK) 5 to 30 min after irradiation. Although MAPK/ERK 1/2 inhibitor U0126 significantly inhibited laser-enhanced cell proliferation, activation of stress-activated protein kinases/Jun N-terminal kinase (SAPK/JNK) and p38 MAPK was not clearly detected. These results suggest that low-level Er:YAG laser irradiation increases osteoblast proliferation mainly by activation of MAPK/ERK, suggesting that the Er:YAG laser may be able to promote bone healing following periodontal and peri-implant therapy.     

High-frequency low-level diode laser irradiation promotes proliferation and migration of primary cultured human gingival epithelial cells

In periodontal therapy, the use of low-level diode lasers has recently been considered to improve wound healing of the gingival tissue. However, its effects on human gingival epithelial cells (HGECs) remain unknown. The aim of the present study was to examine whether high-frequency low-level diode laser irradiation stimulates key cell responses in wound healing, proliferation and migration, in primary cultured HGECs in vitro. HGECs were derived from seven independent gingival tissue specimens. Cultured HGECs were exposed to a single session of high-frequency (30 kHz) low-level diode laser irradiation with various irradiation time periods (fluence 5.7–56.7 J/cm²). After 20–24 h, cell proliferation was evaluated by WST-8 assay and [³H]thymidine incorporation assay, and cell migration was monitored by in vitro wound healing assay. Further, phosphorylation of the mitogen-activated protein kinase (MAPK) pathways after irradiation was investigated by Western blotting. The high-frequency low-level irradiation significantly increased cell proliferation and [³H]thymidine incorporation at various irradiation time periods. Migration of the irradiated cells was significantly accelerated compared with the nonirradiated control. Further, the low-level diode laser irradiation induced phosphorylation of MAPK/extracellular signal-regulated protein kinase (ERK) at 5, 15, 60, and 120 min after irradiation. Stress-activated protein kinases/c-Jun N-terminal kinase and p38 MAPK remained un-phosphorylated. The results show that high-frequency low-level diode laser irradiation promotes HGEC proliferation and migration in association with the activation of MAPK/ERK, suggesting that laser irradiation may accelerate gingival wound healing.     

Evaluation of a nanocomposite of PEG-curcumin-gold nanoparticles as a near-infrared photothermal agent: an in vitro and animal model investigation

Hyperthermia is a promising alternative modality for the conventional cancer treatments. Nanoparticle-mediated photothermal therapy (PTT) has been widely applied for hyperthermia cancer therapy by a near-infrared light irradiation. Some special nanoparticles can convert light energy into heat and destroy the tumor cells. Inspired from the photothermal efficacy of the gold nanoparticles, here we synthesized, characterized, and applied novel photothermal polyethylene glycol-curcumin-gold nanoparticles (PEG-Cur-Au NPs) in cancer PTT. The effect of PEG-Cur-Au NPs upon irradiation by an 808-nm laser on C540 (B16/F10) cell line as well as implanted (bearing) melanoma tumor in inbred C57 mice was investigated. In vitro temperature increment, cell viability evaluation, and histological analyses were performed. The results showed a dose-dependent cytotoxicity of PEG-Cur-Au NPs toward C540 (B16/F10) cell line at concentrations ≥ 25 μg mL^?1 with an IC₅₀ value of 42.7 μg mL^?1 in dark (and with no toxicity for 10 μg mL^?1). On the other hand, 808-nm laser irradiation alone (without using PEG-Cur-Au NPs) for 10 min induced killing effect on the C540 (B16/F10) cell line in a laser power-dependent manner at power density >?0.5 W cm^?2 (no toxicity for 0.5 W cm^?2). However, PPT using PEG-Cur-Au NPs was tremendously observed after laser illumination. Even under laser irradiation at a power density of 0.5 W cm^?2 of PEG-Cur-Au NPs of concentrations <?10 μg mL^?1, PTT of the cells was substantial. Histological analyses and volume measurements of the induced tumors in the mice revealed an appropriate control of the tumors upon PTT by PEG-Cur-Au NPs. Combination of PEG-Cur-Au NP administration and 808-nm diode laser irradiation destroyed the melanoma cancer cells in the animal model.     

Laser phototherapy (780 nm), a new modality in treatment of long-term incomplete peripheral nerve injury: a randomized double-blind placebo-controlled study

OBJECTIVE: The authors conducted this pilot study to prospectively investigate the effectiveness of low-power laser irradiation (780 nm) in the treatment of patients suffering from incomplete peripheral nerve and brachial plexus injuries for 6 months up to several years. BACKGROUND DATA: Injury of a major nerve trunk frequently results in considerable disability associated with loss of sensory and motor functions. Spontaneous recovery of long-term severe incomplete peripheral nerve injury is often unsatisfactory. METHODS: A randomized, double-blind, placebo-controlled trial was performed on 18 patients who were randomly assigned placebo (non-active light: diffused LED lamp) or low-power laser irradiation (wavelength, 780 nm; power, 250 mW). Twenty-one consecutive daily sessions of laser or placebo irradiation were applied transcutaneously for 3 h to the injured peripheral nerve (energy density, 450 J/mm(2)) and for 2 h to the corresponding segments of the spinal cord (energy density, 300 J/mm(2)). Clinical and electrophysiological assessments were done at baseline, at the end of the 21 days of treatment, and 3 and 6 months thereafter. RESULTS: The laser-irradiated and placebo groups were in clinically similar conditions at baseline. The analysis of motor function during the 6-month follow-up period compared to baseline showed statistically significant improvement (p = 0.0001) in the laser-treated group compared to the placebo group. No statistically significant difference was found in sensory function. Electrophysiological analysis also showed statistically significant improvement in recruitment of voluntary muscle activity in the laser-irradiated group (p = 0.006), compared to the placebo group. CONCLUSION: This pilot study suggests that in patients with long-term peripheral nerve injury noninvasive 780-nm laser phototherapy can progressively improve nerve function, which leads to significant functional recovery.     

Low-power 808-nm laser irradiation inhibits cell proliferation of a human-derived glioblastoma cell line in vitro

It has been reported that low-power laser irradiation (LLI) can modulate various biological processes including cell proliferation. Some reports suggest that LLI interferes with the cell cycle and inhibits cell proliferation, while others suggest that LLI has a stimulatory effect. Mechanisms underlying the effects of LLI remain unclear. Since the effects of LLI on cancer cells are not well understood, with the aim of developing an LLI therapy for malignant glioblastoma, we investigated the effects of LLI on the cell proliferation of the human-derived glioblastoma cell line A-172. Glioblastoma cell cultures were irradiated with a diode laser at a wavelength of 808 nm and the effects on cell viability and proliferation were examined. Cell counting at 24 and 48 h after irradiation showed that LLI (at 18, 36 and 54 J/cm²) suppressed proliferation of A-172 cells in a fluence-dependent manner (irradiation for 20, 40 and 60 min). A reduction in the number of viable cells was also demonstrated by a fluorescent marker for viable cells, calcein acetoxymethylester (calcein-AM). The reduction in cell viability was not associated with morphological changes in the cells or with necrotic cell death as demonstrated by propidium iodide staining. LLI also had little effect on cell proliferation as shown by 5-bromo-2′-deoxyuridine staining. We discuss possible mechanisms underlying the suppressive effect of 808-nm LLI on the viability of human-derived glioblastoma A-172 cells.     

Effect of Helium-Neon (He-Ne) Laser Irradiation on Dog Neoplasm Cells in Culture

The effects of laser light on the cellular proliferation have been extensively characterised. Low-power laser sources, such as the helium–neon (He-Ne) laser irradiation with a wavelength of 632.8 nm, have been found to produce photobiological and photodamaging effects with evidence of interference with cell proliferation functions. The present study has investigated the in vitro effect of He-Ne laser irradiation on the proliferative action of dog tumour cells in culture. Dose–response studies showed that repeated He-Ne irradiation (irradiance 12.8 mW/cm²) once a day for 4 consecutive days in a dose range between 0.13 and 2.08 J/cm² significantly increased with increasing energy density up to a laser dose of 0.26 J/cm², whereas at >1.04 J/cm², the cell proliferation decreased with increasing energy densities. It is concluded that the application of He-Ne laser irradiation at energy densities ranging from 0.13 J/cm² to 2.08 J/cm² produced different effects on cell proliferation in dog tumour cells in culture. Paper received for publication 27 June 1997; accepted following revision 6 February 1998.     

Evaluation of different treatment protocols for dentin hypersensitivity: an 18-month randomized clinical trial

This randomized and longitudinal in vivo study aimed to assess different protocols for the treatment of dentin hypersensitivity with low-power laser (with different doses), high-power laser, and a desensitizing agent, for a period of 12 and 18 months. The lesions from 32 patients (117 lesions), who were submitted to the inclusion and exclusion criteria, were divided into nine groups (n = 13): G1: Gluma Desensitizer (Heraeus Kulzer), G2: low-power laser with low dose (three points of irradiation in vestibular portion and an apical point 30 mW, 10 J/cm², 9 s per point with the wavelength of 810 nm, with three sessions with an interval of 72 h), G3: low-power laser with high dose (one point in the cervical area, and one apical point 100 mW, 40 J/cm², 11 s per point with the wavelength of 810 nm in three sessions with an interval of 72 h), G4: low-power laser with low dose + Gluma Desensitizer, G5: low-power laser with high dose + Gluma Desensitizer, G6: Nd:YAG laser (Power Laser? ST6, Research® in contact 1.0 W, 10 Hz and 100 mJ, ≈85 J/cm², with the wavelength of 1064 nm), G7: Nd:YAG laser + Gluma Desensitizer, G8: low-power laser with low dose + Nd:YAG laser, and G9: low-power laser with high dose + Nd:YAG laser. The level of sensitivity of each volunteer was assessed by visual analog scale of pain (VAS) with the aid of air from the triple syringe and exploration probe, 12 and 18 months after treatment. All analyses were performed separately for air and probe stimulus. The level of significance was considered for values of p < 0.05. After statistical analysis, all treatments were shown to be effective in reducing dentinal hypersensitivity, and the results were considered not statistically different from those at 12 months. Therefore, until the 18-month evaluation, it could be said that no statistical differences were observed in the sensitivity levels for all treatments.     

Effects of low-power laser irradiation on survival of random skin flap in rats

This research was designed to study the effects of low-power helium–neon (He–Ne) laser irradiation on random skin flap survival in rat. Fifty 50 male rats were randomly divided into five groups. On the dorsum of each rat, one full thickness random skin flap which contained no specific vessel was elevated. Groups 1 to 4 were exposed to different models of a low-power He–Ne laser. Group 5 rats received no laser treatment and were considered as the control group. The energy density of the He–Ne laser used was 0.2 J/cm². Immediately after surgery and at day 7, the surface area of all flaps was determined. Histological and tensiometrical studies on the surviving part of the flaps were also performed. The data obtained were analyzed by ANOVA. The results showed a significant difference in the surface area of survival parts of flaps and density of blood vessels on day 7 between group 3 rats and the other groups (P=0.0188, P=0.0455). Low-power He–Ne laser irradiation of flaps without recognized blood vessels in rats, reduced vasospasm, produced vasodilation, and caused a significant increase in the surviving surface area.Presented at the 14th World Congress of the International Society for Laser Surgery and Medicine, India, 27–30th August, 2001