• Journal of the korean academy of Pediatric Dentistry
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• v.30 no.2
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• pp.272-285
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• 2003

This study was conducted to observe the microscopic structures of cavities formed after ablation of primary teeth, permanent teeth, enamel and dentin in using a bur and cavities formed after ablation using laser and the following results were obtained after comparing the effects of ablation. Using a #330 bur and Er:YAG laser irradiated at 150 mJ, 200 mJ, 250 mJ and 300 mJ all at the frequency of 5 Hz, 1 mm enamel and dentin samples were ablated and the ablation time was measured. In order to measure the surfaces ablated, 5 each of primary teeth and permanent teeth were ablated using a #330 bur and Er:YAG laser at 150 mJ, 200 mJ, 250 mJ and 300 mJ for 1 sec and the cross section and vertical section were observed. The following results were obtained : 1. Cutting time of Er:YAG laser was longer than that of conventinal high-speed bur regardless of teeth type. 2. Cutting on enamel, Cutting time of conventional high-speed bur in deciduous teeth was longer than in permanent teeth(P<0.05). But Er:YAG laser was not showed any difference between the deciduous and permanent teeth(P>0.05). 3. Cutting on dentin, Cutting time of conventional high-speed bur in permanent teeth was longer than deciduous teeth. Er:YAG laser of 150 mJ, 5 Hz in permanent teeth was longer than in deciduous teeth(p<0.05). But laser of other power did not showed mean difference. 4. The cavity surface treated with the convetional high-speed bur revealed a relatively flat appearance, almost covered with a debris-like smear layer. Cavity wall showed striped appearance because of blade of bur. 5. The cavity surface treated by the Er:YAG laser system was irregular or rough surface with the absence charring, carbonization, or cracking of the dentin. In addition, there was an absence of a smear layer. Cavity floor was round and relatively smooth. According to these results, cutting time of Er:YAG laser was almostly same in permanent and deciduous teeth, but more effective in dentin than enamel. Cutting the sample, Er:YAG laser was needed more time than conventional bur. But SEM findings suggested that laser device produced favorable surface characteristic(i.e, no smear layer, irregular surface, cracking).

• Korean Journal of Optics and Photonics
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• v.15 no.5
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• pp.469-474
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• 2004

We have fabricated and designed wavelength-tunable sampled grating distributed Bragg reflector laser diodes(SGDBR-LD) by using, for the first time, planar buried heterostructures(PBH). The diodes have low threshold current values and high-performance of laser operation. Growth condition using metal organic chemical vapor deposition(MOCVD) was optimized for the formation of a good butt-coupling at the interface. A maximum output power of the fabricated device was 20 mW under 200 mA continuous wave(CW) operation at $25^{\circ}C$. Average threshold current and voltage were 12 mA and 0.8 V, approximately. This output power is higher than those of ridge waveguide(RWG) and buried ridge stripe(BRS) structures by amounts of 9 mW and 13 mW, respectively. We obtained a tuning range of 44.4nm which is well matched with the target value of our design. The side mode suppression ratio of more than 35 dB was obtained for the whole tuning range. Optical output power variation was less than 5 dB, which is 4 dB smaller than that of RWG structures.

• Journal of Biomedical Engineering Research
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• v.30 no.1
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• pp.18-22
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• 2009

Laser has been widely used in various fields of medicine. Recently, noninvasive low-level laser therapeutic medical devices have been introduced in market. However, low-level laser cannot deliver enough photon density to expect positive therapeutic results in deep tissue layer due to the light scattering property in tissue. In order to overcome the limitation, this study was aimed to develop a negative pressure applied low-level laser probe to optimize laser transmission pattern and therefore, to improve photon density in soft tissue. In order to evaluate the possibility of clinical application of the developed laser probe, ex-vivo experiments were performed with porcine skin samples and laser transmissions were quantitatively measured as a function of tissue compression. The laser probe has an air suction hole to apply negative pressure to skin, a transparent plastic body to observe variations of tissue, and a small metallic optical fiber guide to support the optical fiber when negative pressure was applied. By applying negative pressure to the laser probe, the porcine skin under the metallic optical fiber guide is compressed down and, at the same time, low-level laser is emitted into the skin. Finally, the diffusion images of laser in the sample were acquired by a CCD camera and analyzed. Compared to the peak intensity without the compression, the peak intensity of laser increased about $2{\sim}2.5$ times and FWHM decreased about $1.67{\sim}2.85$ times. In addition, the laser peak intensity was positively and linearly increased as a function of compression. In conclusion, we verified that the developed low-level laser probe can control the photon density in tissue by applying compression, and therefore, its potential for clinical applications.

• Korean Journal of Acupuncture
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• v.22 no.2
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• pp.163-181
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• 2005

Objective: The purpose of this study is to review research papers on low level laser therapy (LLLT) and to improve the knowledge of LLLT field. Methods: For introduction, laser characteristics, including wavelength, medium, beam size, power, and unit power were explained. In order to understand LLLT, tissue optics and light-biomatter interaction were briefly mentioned. We reviewed 21 Korean papers on laser acupuncture and LLLT on the viewpoint of laser apparatus. Results and Conclusion: We found that the description of laser apparatus employed for LLLT experiments were not fully written. Laser wavelength and power which are the most crucial parameters, were omitted in several papers. No paper had information on beam size. In order to have high efficacy, laser should be used with proper laser parameters. Conditions of irradiation area or acupoints should be considered too. Some future technology on laser acupuncture were mentioned.

• The Korean Journal of Pain
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• v.7 no.1
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• pp.74-77
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• 1994

Since its introduction, low level lasers have been utilized in many varied clinical applications for the treatment of musculoskeletal and body surface lesions. Due to the laser beams specific characteristic-coherence, monochromaticity and unidirectionality, without adverse reaction with neighbouring tissue, physicians have used it with relative ease. We observed accelerating effects of healing process of some intractable skin wound, improvement of graft survival, as well as reduction of pain on ulcerating tissues, by treating twice weekly with low level Helium-Neon(He-Ne) and Infrared(IR) laser. The laser's energy density was set at $1\;J/cm^2$ and a fixed frequency of 600 Hz by continuous scanning. Irradiating time was calculated according to the cross diameter of the wound. Further clinical work will be required to evaluate the accelerated healing processes by biostimulating mechanisms of laser ray, especially for the intractable(diabetic) skin ulceration.

• Journal of Korean Medicine Rehabilitation
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• v.20 no.1
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• pp.183-192
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• 2010

Objectives : The purpose of this study is to investigate the clinical effects of low level laser therapy on shoulder pain. Methods : From October 1, 2009 to November 14, 2009, we applied 15 participants who consented to an assignment had a shoulder pain to low level laser therapy(LLLT). We treated LLLT 8 times on both upper trapezius, levator scapular, pectoralis, suboccipital, rhomboid, rotator cuff tender point for 2 weeks. To evaluate the efficiency of low level laser therapy, we used questionnaire of shoulder pain symptom, questionnaire of a day living discomfort scale, shoulder pain and disability index(SPADI) and pressure pain threshold(PPT) at before treatment and after treatment 4 times and 8 times. Results : There was a significant difference in questionnaire of shoulder pain symptom, questionnaire of a day living discomfort scale, SPADI and PPT after 8th treatment. Conclusions : Low level laser therapy for shoulder pain is effective to improve patients' symptoms measured with questionnaire of pain and a day living discomfort score, SPADI and PPT significantly.

• Journal of Korean Physical Therapy Science
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• v.13 no.1
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• pp.7-20
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• 2006

Purpose: This study was to find that what mechanism take effects that was Adjuvant Induced Arthritis in Sprague-Dawley rat and then treated the swimming and low power laser. Methods: Adjuvant Induced Arthritis was induced 24 Sprague-Dawley rat by the subcutaneous injection of a 0.2ml Freund's Complete Adjuvant into the right hind paw and right knee joint. Second injection used of 0.05ml Freund's Complete Adjuvant by same method. Arthritic rat were divided 3 groups; arthritic swimming group, arthritic laser group and case control group. The author performed several experimental tests which were the hind paw thickness, step length, knee joint space, activity of enzyme. Results: Hind paw thickness decreased in swimming and laser group. Left step length and knee joint space increased in swimming and laser. Conclusion: Swimming and low power laser therapy on the Adjuvant Induced Arthritis in rats does effective for the rheumatic arthritis therapy by decrease of hind paw thickness, increase of opposite side step length, increase of activity of albumin and IgG and increase of knee joint space.

• Journal of Oral Medicine and Pain
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• v.10 no.1
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• pp.91-104
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• 1985

In order to study the effects of the low power density laser (AsGa) on the wound healing of tongue and skin, thirty two healthy rats were anesthetized with pentothal. The tongue wound, approximately 1 mm in depth and 2mm in diameter, was created on the anterior of the tongue and the skin wound, approximately, 2mm in depth and 6-8mm in diameter, was created on the back of rat with the tip of small rongeur forcep. Wounds of experimental groups were irradiated with AsGa laser (Stomalaser, SEDATELEC Co., France) every other day by ninth day. The areas of wounds were measured at 1, 3, 5, 7, 9 days after wounding and the specimens were sectioned, stained, and observed with light microscope. The results were as follows : 1. In the AsGa laser irradiated wound of tongue, the epithelial and fibroblastic regeneration were accelerated when compared with controls. 2. In the AsGa laser irradiated wound of skin, the epithelial and fibroblastic regeneration were accelerated when compared with controls. 3. When the wound areas were compared, there was a significant difference between control group and experimental group (P < 0.01: 2-Way NOVA).

• The Journal of Korean Physical Therapy
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• v.18 no.3
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• pp.47-58
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• 2006

Purpose: This study was to find that what mechanism take effects that was Adjuvant Induced Arthritis in Sprague-Dawley rat and then treated the swimming and low power laser. Methods: Adjuvant Induced Arthritis was induced 24 Sprague-Dawley rat by the subcutaneous injection of a 0.2ml Freund's Complete Adjuvant into the right hind paw and right knee joint. Second injection used of 0.05ml Freund's Complete Adjuvant by same method. Arthritic rat were divided 3 groups; arthritic swimming group, arthritic laser group and case control group. The author performed several experimental tests which were the hind paw thickness, step length, knee joint space, activity of enzyme. Results: Hind paw thickness decreased in swimming and laser group. Left step length and knee joint space increased in swimming and laser. Conclusion: Swimming and low power laser therapy on the Adjuvant Induced Arthritis in rats does effective for the rheumatic arthritis therapy by decrease of hind paw thickness, increase of opposite side step length, increase of activity of albumin and IgG and increase of knee joint space.

• Journal of Biomedical Engineering Research
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• v.37 no.4
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• pp.147-151
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• 2016

Tibial defect, or fracture is very routine musculoskeletal case which brings fully uncomfortable and painful situations to patient. Moreover, it has long hospitalization period because of its risk of non-union. There are many studies using ultrasound, vibration, and laser for bone regeneration to figure out fast bone healing. Among them, Low Level Laser Therapy (LLLT) is already known that it is very easy to treat and may have positive effect for bone regeneration. However, LLLT has uncertain energy dose because of scattering and absorption of laser in tissue. In this study, we used interstitial LLLT to treat tibial defect in animal study. The Interstitial LLLT can overcome some limitations caused by laser scattering or absorption in tissue medium. The results were evaluated using u-CT which can calculate X-ray attenuation coefficient and bone volume of bone defect area. These results showed that interstitial LLLT may affect fast bone healing process in early phase.