Trans-scleral application of a semiconductor diode laser

We used a diode laser with an output power of 1 W through a fiberoptic light pipe (200 microns diameter) to deliver laser energy through the sclera of pigmented rabbits. Ciliary body destruction occurred with energy levels of 300-400 mW and exposure time of 0.5 sec. Retinal photocoagulation was achieved with energy levels of 200-500 mW in 0.5 sec. Histologic examination of acute lesions demonstrated thermal destruction of ciliary body processes and retina. Chorioretinal scar formation was observed clinically and histologically within 2-3 weeks. Our data indicate that the transscleral diode laser may be used for destruction of the ciliary body processes or peripheral retinal coagulation in pigmented eyes.     

Bactericidal effects of different laser wavelengths on periodontopathic germs in photodynamic therapy

 This study was an attempt to clarify whether the bactericidal effects of photodynamic therapy (PDT) are wavelength or dose-dependent. We also attempted to create an optimised protocol for a light-based bactericidal modality to eliminate periodontal pathogens. Cultures of Actinobacillus actinomycetemcomitans, Fusobacterium nucleatum, Porphromonas gingivalis, Prevotella intermedia, and Streptococcus sanguis, were exposed to a He-Ne laser (632.8 nm) with a 30 mW power output, a 100 mW diode laser at 665 nm, or a 100 mW diode laser at 830 nm, in the presence or absence of methylene blue (MB) as a photosensitiser. A control group was also used with exposure to MB alone without laser exposure. The cultures were analysed by viable counts. The results indicated that exposure to the 100 mW laser light could eliminate up to 40% of bacteria on average. In particular, the most effective killing occurred with exposure to laser light in combination with the MB photosensitiser. The results of kinetic studies indicated that the best PDT response rate was achieved with a 60 s (energy density 21.2 J/cm²) exposure to the 665 nm wavelength diode laser in the presence photosensitiser. In this condition, approximately 95% of A. actinomycetemcomitans and F. nucleatum, and 99–100% of the black-pigmented bacteria (P. gingivalis and P. intermedia) and S. sanguis were eliminated. These results showed that both wavelength and energy density are important factors, and that a low power laser of optimal wavelength and dosage, in combination with an appropriate photosensitiser, is a practical bactericidal modality. We concluded that using a diode laser of proper power and wavelength to deliver 60 s of irradiation could be a useful adjunct with mechanical debridement in the prevention of the re-colonisation of subgingival lesions by pathogenic microorganisms. Received: 29 November 2001 / Accepted: 18 June 2002     

The effect of low-level laser irradiation on dog spermatozoa motility is dependent on laser output power

Biological tissues respond to low-level laser irradiation and so do dog spermatozoa. Among the main parameters to be considered when a biological tissue is irradiated is the output power. We have studied the effects on sperm motility of 655 nm continuous wave diode laser irradiation at different output powers with 3.34 J (5.97 J/cm²). The second fraction of fresh dog sperm was divided into five groups: control, and four to be irradiated with an average output power of 6.8 mW, 15.4 mW, 33.1 mW and 49.7 mW, respectively. At 0 min and 45 min after irradiation, pictures were taken and a computer aided sperm analysis (CASA) performed to analyse different motility parameters. The results showed that different output powers affected dog semen motility parameters differently. The highest output power showed the most intense effects. Significant changes in the structure of the motile sperm subpopulation were linked to the different output powers used.     

Low reactive laser therapy

The type, characteristics and effect of low reactive laser equipment used for pain treatment in Japan are described in this section. Currently, low reactive laser therapy equipments marketed and used in Japan include diode laser therapeutic device with semiconductor as a medium consisting of aluminum, gallium and arsenic. Low reactive laser equipment comes in three models, the first type has a capacity of generating 1,000 mW output, and the second type has a capacity of generating 10 W output. The third type has four channels of output, 60, 100, 140 and 180 mW and we can select one channel out of the four channels. This model is also used as a portable device because of its light weight, and we can carry it to wards and to the outside of the hospital. Semiconductor laser has the capacity of deepest penetration and the effect tends to increase proportionally to the increasing output. Low reactive laser therapy is less invasive and lower incidence of complications. Although low reactive laser therapy might be effective for various pain disorders, the effect is different depending on the type of pain. We should keep in mind that this therapy will not give good pain relief equally in all patients with pain.     

Laser nerve repair by solid protein band technique. I: Identification of optimal laser dose,power, and solder surface area

Thirty-four tibial nerves in 17 adult male wistar rats were repaired by applying protein bands longitudinally across the nerve join. The bands were then irradiated with a fibre-coupled diode laser (λ = 810 nm). The relations among the laser weld breaking force, the power, and the solder surface area were investigated, while maintaining a consistent ratio between the total mass of protein solder in a band and total laser energy delivered (the laser energy dose). When this laser energy dose was held constant, the average breaking force of the laser welds irradiated by 72 mW laser output power was weaker than that reached after 90 mW laser radiation. There is a linear relation between the solder breaking force and the solder surface area when band thickness, laser power, and laser dose are unvaried. © 1998 Wiley-Liss, Inc. MICROSURGERY 18:55–59, 1998.     

Performance of the 808-nm diode laser on equine upper airway tissue is enhanced by intravenous administration of indocyanine green

OBJECTIVE: The objective was to develop a protocol whereby 808-nm diode laser irradiation combined with intravenous (IV) indocyanine green (ICG) could be used in non-contact mode with equal surgical efficacy to the Nd:YAG on equine tissues. BACKGROUND DATA: The 808-nm diode laser, delivering 20-40 W of power, has been produced for veterinary medical applications. This laser's power output is less than that of most neodymium:yttrium-aluminum-garnet (Nd:YAG) lasers. ICG is absorbed at a wavelength of 810 nm, which when concentrated in tissue should be an excellent absorber for the energy produced by the 808-nm diode laser. METHODS: This study compares the depths and widths of thermal penetration achieved with the 808-nm diode laser in equine respiratory tissue after intravenous injection of ICG. ICG was administered at two doses: 1.5 mg/kg and 3 mg/kg. The 808-nm diode laser and Nd:YAG laser were set to deliver 200 J of energy. The depths and widths of thermal penetration obtained were compared. RESULTS: Lesion depth and width tended to be greater in the ICG + 3 mg/kg group than in the ICG + 1.5 mg/kg group. Even so, the 1.5-mg/kg dose substantially increased the efficacy of the diode laser. Plasma ICG concentrations peaked at 5 min post-administration and then dropped markedly; lesion depth decreased after peaking at 7 min post-administration. CONCLUSION: This study demonstrated that the 808-nm diode laser, when augmented with intravenous ICG, will be as effective a surgical tool as the Nd:YAG laser on equine upper airway tissues when applied using a non-contact fiber.     

Infrared laser diode irradiation has no behavioral or biochemical effect on pain in the sciatic nerve ligation-induced mononeuropathy in rat.

The aim of this study was to evaluate the effect of acute and repeated (5 days) treatment with various types of infrared (IR) diode lasers and probes (single- vs cluster-beam) on the pain response in rats with peripheral mononeuropathy produced by sciatic nerve ligation. Male Sprague-Dawley rats were anesthetized with sodium pentobarbital, and the mid-thigh was surgically exposed to reveal the sciatic nerve, around which four ligatures were loosely tied. On postoperative day 5, the skin over the sciatic nerve lesion was subjected to a 30-min daily local exposure from a 904-nm IR diode laser (700 Hz, average output power 10 mW) with a single-beam probe, a 830-nm IR diode laser (700 Hz) with either a single-beam (average output power 50 mW) or cluster-beam probe (average output power 15 mW), or placebo for 5 consecutive days. Two pain responses (foot-withdrawal time and the hind-paw elevation time) were measured on both sides using the radiant heat method on days 5 and 9. In addition, cold allodynia was measured on day 9 of treatment by placing the rats on a chilled metal plate (4 degrees C) and measuring the duration of elevation of either of the hind paws. On day 9, the animals were sacrificed for collection of the samples of brain and lumbar spinal cord for the determination of the tissue concentrations of dynorphin A1-8-like immunoactivity (DYN) using specific radioimmunoassay (RIA). The hind-paw withdrawal and elevation times on the right side in all groups subjected to the various methods of IR laser irradiation did not differ significantly as compared with the placebo-treated group when measured on days 5 and 9 after surgery. No statistically significant differences in withdrawal response and elevation time of the unaffected left hind paw were noted either. The measurement of cold allodynia similarly failed to reveal any effect in laser-treated groups versus placebo. The RIA analysis found that tissue concentrations of DYN were significantly elevated in the spinal cord ipsilaterally to the ligation side, as compared with the contralateral side, in all rats with sciatic nerve ligation. All modalities of IR diode laser treatment did not produce any significant difference in the brain and spinal cord level of DYN on postoperative day 9 in all treatment groups. It is concluded that repeated IR diode laser treatment did not reduce hyperalgesia induced by sciatic nerve ligation in rats.     

Microvascular anastomosis using a new diode laser system with a contact probe

The aim of the present study was to demonstrate the usefulness of our newly produced diode laser device (an 830-nm output of 190 mW CW) for microvascular end-to-end anastomoses. In the device, diode laser energy is delivered to a contact ceramic tip with a 200-microns diameter output end. Its wavelength is 830 nm and its power 60 mW. This device is small (30 x 25 x 10 cm), lightweight (gross weight 3kg), and easy to manipulate. Compared with conventional microvascular suture anastomosis (CMSA), the time required for the laser-assisted vascular anastomoses (LAVA) was reduced by almost half. Anastomosed portions of both methods were examined 1, 2, 4, 12, and 24 weeks later for patency and aneurysm formation. The patency rate and incidence of aneurysmal formation were the same in both groups. Histological examination revealed that LAVA is superior to CMSA in the smoothness of the inner surface, less inflammatory reaction, and normal collagen and elastic reorientation. The tensile strength and bursting pressure measured immediately after anastomosis demonstrated no significant difference between the two groups. It was concluded that this diode laser contact method may be clinically useful for microvascular surgery.     

AnIn-Vitro analysis of two laser doppler flowmetry systems for evaluation of bone perfusion

Summary Laser Doppler Flowmetry (LDF) has been shown to be a useful tool in the experimental and clinical measurement of bone blood flow. Two LDF receiving fiber channel systems, one with a 2mW He−Ne tube laser source and the other with an infrared diode laser source, were compared with specific reference to their light attenuation through three types of bone as well as their threshold thickness for the same specimens. The threshold thickness was higher for the infrared diode system for all three bone types whereas the attenuation was identical. The demonstrated differences were most likely due to the criteria established for flow detection; the infrared diode system has a greater degree of amplification of the output signal, yielding a higher value at each thickness of bone. The two systems will produce similar output data when used for experimental analysis of bone blood flow.     

In vitro analysis of human tooth pulp chamber temperature after low-intensity laser therapy at different power outputs

In vitro studies have provided conflicting evidence of temperature changes in the tooth pulp chamber after low-level laser irradiation of the tooth surface. The present study was an in vitro evaluation of temperature increases in the human tooth pulp chamber after diode laser irradiation (GaAlAs, λ = 808 nm) using different power densities. Twelve human teeth (three incisors, three canines, three premolars and three molars) were sectioned in the cervical third of the root and enlarged for the introduction of a thermocouple into the pulp chamber. The teeth were irradiated with 417 mW, 207 mW and 78 mW power outputs for 30 s on the vestibular surface approximately 2 mm from the cervical line of the crown. The highest average increase in temperature (5.6°C) was observed in incisors irradiated with 417 mW. None of the teeth (incisors, canines, premolars or molars) irradiated with 207 mW showed temperature increases higher than 5.5°C that could potentially be harmful to pulp tissue. Teeth irradiated with 78 mW showed lower temperature increases. The study showed that diode laser irradiation with a wavelength of 808 nm at 417 mW power output increased the pulp chamber temperature of certain groups of teeth, especially incisors and premolars, to critical threshold values for the dental pulp (5.5°C). Thus, this study serves as a warning to clinicians that “more” is not necessarily “better”.     

Potentiation of laser-tissue interactions of the 805 nm laser with indocyanine green

A high power 805 nm diode laser with advantages of compact size, portability and ease of installation and use has recently been introduced. This unit has comparable laser-tissue interactions to the Nd-YAG in contact mode, however the maximum power output of 25 W has limited its clinical applications. We have compared 805 nm with 1064 nm laser energy in noncontact mode before and after the addition of a chromophore (intravenous indocyanine green). There is equivalency of laser-tissue interactions of 805 and 1064 nm in non-contact mode up to a maximum power output of 20 W. Laser-tissue interactions of the 805 nm laser are significantly potentiated by indocyanine green, as shown by a significant increase in diameter of tissue thermal injury. The 805 nm diode may therefore provide an alternative to the 1064 nm laser in non-contact as well as contact mode.     

Surgical application of low-power laser: experimental study, development of equipments and clinical application

We carried out experimental and clinical studies with low-power laser to perform the surgical application. The developed device for microvascular anastomosis with semiconductor laser diode made of In-Ga-As-P was used to perform 15 end-to-end laser assisted microvascular anastomoses of carotid arteries in rabbits. In four of 7 cases which were irradiated with power output 50mW showed patency immediately after surgery with no wound disruption. A new medical device with Ga-A1-As semiconductor laser diode was developed for pain relief. A double-blind evaluation of the test was initiated in 124 patients suffering from chronic inflammatory pain. Result is that of 63 patients irradiated laser, 45(71%) were effective and of 61 cases not irradiated laser, 8(13%) were relieved pain. The data were analyzed statistically by chi square, and criterion for statistical significance was the 0.01 level. The spectral properties of laser-excited fluorescence of three photosensitizers, namely tetracycline, hematoporphyrin free base and chlorin e6Na, taken up in human arterial intima were detected. Photosensitizers were administrated to resected human arteries for 2 hours in vitro. The main results are following: 1) Photosensitizers are confirmed to be taken up in arterial intima and the fluorescence intensity decreases as the time goes on. 2) The fluorescence intensity from atheromatous plaque is usually stronger than that from normal region.     

Diode laser and microvascular carotid anastomosis: A preliminary study

A crossed carotid end-to-end anastomosis was performed in 20 Wistar rats by means of a diode laser device (wavelength 830 nm and power output 3 W in continuous wave). The diode laser energy was delivered into a micromanipulator coupled to an OPMI 1 Zeiss operating microscope with a focused spot of 300 μm diameter. The vessel sealing was effected on common carotids (0.8–1.2 mm) using laser shots (average 9) of 680 mW power and 4.5 s duration and 962 W cm⁻² irradiance each. The good vascular flow was confirmed by Doppler spectral analysis and angiography performed on days 0, 10 and 30. Light and scanning electron microscopy showed that reendothelialization was complete on day 10 whilst collagenous fusion of media and adventitia was obvious. The patency rate was 90% impaired by a lethal thrombosis. The efficiency of the diode laser was compared to that of other types of LAVA and to manual microanastomosis.     

Diode laser-induced thermal damage evaluation on the retina with a liposome dye system

BACKGROUND AND OBJECTIVES: The aim of the study was to evaluate the feasibility of retinal thermal damage assessment in a rabbit eye model by using laser-induced release of liposome-encapsulated dye. STUDY DESIGN/MATERIALS AND METHODS: After anesthesia, thermosensitive liposomes (DiStearoyl Phosphatidyl Choline: DSPC) loaded with 5,6-carboxyfluorescein were injected intravenously to pigmented rabbits. Retinal photocoagulations were performed with a 810nm diode laser (P=100-400 mW, laser spot=500 microm, 1s) (OcuLight, IRIS Medical Instruments, Mountain View, CA). Fluorescence measurements in the area of the laser exposures were then realized with a digitized angiograph (CF-60UVi, Canon-Europe, The Netherlands; OcuLab, Life Science Resources, UK). RESULTS: Fluorescent spots were observed for power ranging from 100 +/- 5 mW to 400 +/- 5 mW. The fluorescence intensity increased linearly with the power and reached a plateau at 280 +/- 5 mW. The fluorescence intensity was correlated to the maximum temperature at the center of the laser spot with a linear increase from 42 +/- 3 degrees C to 65 +/- 3 degrees C. These results are in agreement with our two previous studies with DSPC liposomes for temperature measurements in a tissue model and then in a vascular model. CONCLUSION: This preliminary study demonstrates the possibility of a laser-induced release of liposome-encapsulated dye for a quantification of diode laser induced thermal damage in ophthalmology. Such a method could be useful for a real-time monitoring of laser photocoagulation for conditions such as choroidal neovascular membranes when a precise thermal damage is required near the foveolar area.     

Laser phototherapy effect on protein metabolism parameters of rat salivary glands

The aim of this study was to evaluate the effects of infrared diode laser phototherapy (LP) on tissues of the submandibular gland (SMG) and parotid gland (PG). Wistar rats were randomly divided into experimental (A and B) and control (C) groups. A diode laser, 808 nm wavelength, in continuous wave mode, was applied to the PG, SMG and sublingual gland in the experimental groups on two consecutive days. The doses were 4 J/cm² and 8 J/cm², and total energy was 7 J and 14 J, respectively. The power output (500 mW) and power density (277 mW/cm²) were the same for both experimental groups. In order to visualize the area irradiated by the infrared laser, we used a red pilot beam (650 nm) with 3 mW maximum power for the experimental groups. For the control group, the red pilot beam was the only device used. The SMG and PG were removed after 1 week of the first irradiation. Total protein concentration, amylase, peroxidase, catalase and lactate dehydrogenase assays were performed, as well as histological analysis. Statistical tests revealed significant increase in the total protein concentration for groups A and B in the parotid glands (P < 0.05). Based on the results of this study, LP altered the total protein concentration in rats’ parotid glands.     

Coagulation of blood at the tip of optical fibres used for light delivery in photodynamic therapy

Optimal delivery of light to the tumour is of considerable importance in photodynamic therapy. The most effective way of delivering laser light to the tumour tissue is through an implanted optical fibre. In order to investigate the possible effects taking place at the tips of fibres implanted in tissue, fibres were used to deliver light to human blood and the transmission of light by the blood was measured at different power levels. The maximum power level which could be delivered without charring or coagulation at the fibre tip was measured for five different fibres. Three plane cut fibres and two with 1.5 cm long diffusing tips were studied. Charring and coagulation, which resulted in practically no light being delivered more than 0.5 mm from the fibre tip, were observed at relatively low-output powers (70-130 mW) for all the plane-cut fibres. This is less than the level required to deliver a clinically useful dose in a reasonable time. In contrast, neither charring nor coagulation was observed at the diffusing tips for output powers up to 1.1 W and consequently these should be the fibres of choice for interstitial photodynamic therapy. Observed changes in light transmission through the blood with increasing output power indicate that, for accurate light dosimetry, a means of monitoring delivered light in vivo during photodynamic therapy is essential.     

Pulpal response following photo-biomodulation with a 904-nm diode laser: a double-blind clinical study

The aim of this study was to evaluate pulpal responses in healthy human teeth to photo-biomodulation therapy (PBMT) with 904-nm GaAs diode laser. The study followed a double-blind split mouth design, with a randomly selected maxillary first premolar acting as a sham-irradiated control tooth, and the contralateral tooth receiving active laser treatment. Two coded but otherwise identical laser probes (Irradia?, SpectraMedics Ltd., NC, USA) were used to deliver the sham (placebo) and laser radiation, with both the operator and patient unaware of each probe’s identity. The selection of teeth for sham or laser irradiation was randomised for each treatment. Pulpal responses were assessed using electric pulp testing (EPT), 2 min prior to exposure, and immediately after laser irradiation (60 s, 30 mW average power, 25 Hz pulse frequency, 3.6 J/cm²). Treatment effects were analysed using the Wilcoxon-signed rank test. A total of 30 participants provided written informed consent. Majority of the participants (66.7 %) demonstrated an analgesic effect following PBMT (elevated EPT scores); however, nine participants (30 %) reported the lower EPT scores than the control. Both the treatment effects (stimulation and analgesia) were significant compared to the placebo. In most individuals, PBMT of healthy teeth with a 904-nm GaAs diode laser can induce analgesia, as witnessed by elevated EPT scores. A converse effect can occur in a minority of subjects.     

The effect of low level laser irradiation on adult human adipose derived stem cells

This study investigated the effect of low level laser irradiation on primary cultures of adult human adipose derived stem cells (ADSC) using a 635-nm diode laser, at 5 J/cm(2) with a power output of 50.2 mW and a power density of 5.5 mW/cm(2). Cellular morphology did not appear to change after irradiation. Using the trypan blue exclusion test, the cellular viability of irradiated cells increased by 1% at 24 h and 1.6% at 48 h but was not statistically significant. However, the increase of cellular viability as measured by ATP luminescence was statistically significant at 48 h (p < 0.05). Proliferation of irradiated cells, measured by optical density, resulted in statistically significant increases in values compared to nonirradiated cells (p < 0.05) at both time points. Western blot analysis and immunocytochemical labeling indicated an increase in the expression of stem cell marker beta1-integrin after irradiation. These results indicate that 5 J/cm(2) of laser irradiation can positively affect human adipose stem cells by increasing cellular viability, proliferation, and expression of beta1-integrin.     

Microbial reduction in periodontal pockets under exposition of a medium power diode laser: an experimental study in rats

BACKGROUND AND OBJECTIVE: This work evaluates the application of a 810 nm diode laser operating in the range of 400-1,200 mW for bacterial reduction at periodontal treatment. The aim of this study is to examine the immediate effect of the diode medium power laser in reducing the bacterial concentration at periodontal pockets induced in Wistar rats. STUDY DESIGN/MATERIALS AND METHODS: Two bacterial collections were performed on each animal. Microbiological samples were collected before and immediately after laser irradiation. In each group of laser power, eight animals were used, totaling 40 animals. RESULTS: The initial and the final bacterial count revealed that laser irradiation induces considerable bacterial elimination, especially for Prevotella sp, Streptococcus beta-hemolitico, Fusobacterium sp, Pseudomonas sp. CONCLUSIONS: Our results indicate that this laser can constitute an alternative device to traditional infrared systems for bacterial reduction, with some advantage when economical and practical standpoints are considered.     

Laser light combined with a photosensitizer may eliminate methicillin-resistant strains of Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is a major cause of hospital acquired infection throughout the world especially in wound and burn infections, pneumonia, septicaemia and endocarditis. We describe the effect of a HeNe laser in combination with a TBO dye on the viability of MRSA. A total of 34 isolates of S. aureus were obtained from 100 patients suffering from burns or wounds and from the nasal vestibulum of medical and nonmedical staff as carriers; eight isolates were methicillin-resistant. The isolates were exposed for 5, 10 and 15 min to a HeNe laser at a wavelength of 632.8 nm and 7.5 mW output power in the presence of 50 μg/ml toluidune blue O photosensitizer. The viable count was substantially decreased as determined by the plate count method for the three exposure times, with 100% killing with the 15-min exposure time. No significant effect was observed on MRSA isolates exposed to the laser alone. So MRSA was completely eradicated following 15 min exposure to a 632.8-nm HeNe laser in the presence of 50 μg/ml toluidune blue O photosensitizer under in vitro conditions.