• Journal of Periodontal and Implant Science
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• v.26 no.2
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• pp.531-541
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• 1996

Periodontal disease is characterized by destruction of supporting tissues caused by invasion of plaque bacteria and defense mechanism of host. Many dentists are very interested in laser therapy on various intraoral soft tissue lesions including inflammatory periodontal pocket. In order to determine the therapeutic effect of intrapocket irradiation of a pulsed- Nd : YAG laser on the inflammatory periodontal pockets, bilateral 60 teeth with 4-6mm in probing pocket depth and gingival inflammation were selected and evaluated by sulcus bleeding index(SBI), and plaque index(pI) for baseline record. Intrapocket irradiation($300{\mu}m$ fiber optic, I.5W power, for 2 min.) of a pulsed-Nd : YAG laser(EL.EN.EN060, Italy) was applied on half of them. As the control group, the same procedure except power-off was repeated on the contralateral 30 teeth. At 1-, 2-, 3-, and 4-week after intrapocket manipulation, every tooth was reevaluated by the same clinical indices. And the difference between the lased group and control group was statistically analyzed by paired t-test and Chi-square test in Microstat program. Following results were obtained: 1. Until I-week and 2-week after intrapocket manipulation, SBI was lowered in both lased group and control group, compared to baseline SBI, but from 3-week after, the recovering tendency toward baseline was noted, and at only 2-week after, the number of teeth showing lowered SBI was significantly more in lased group than in control group(p<0.05). 2. PI of both lased group and control group was lowered through whole experimental period from I-week to 4-week after, compared to baseline PI(p<0.05), but there was no significant difference between lased group and control group(p>0.1). The results suggest that intrapocket irradiation of a pulsed-Nd:YAG laser may lead somewhat remission of gingival inflammation, but for more favorable therapeutic result the thorough root planing should be necessarily accompanied with gingival curettage.

• Journal of Oral Medicine and Pain
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• v.22 no.2
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• pp.261-282
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• 1997

This study was undertaken to compare and investigate the wound healing process following Nd:YAG laser wounds and scalpel incisions of the rat tongue dorsal mucosa. Laser wounds were made parallel on the right side of tongue dorsum and scalpel incisions were made on the left side with 5mm length, respectively Visual inspection and immunohistochemistry with CD44 antibody after immediately, 6 hours, 1 day, 2, 4, 7, 11, 21 days after surgery were carried out. The results were as follows : 1. There was macroscopically no treat difference between laser wounds and scalpel incisions. 2. Laser wounds appeared as dry, bloodless and irregular grooves with carbonization and whitening of superficial tissues compared to sharp, straight and bleeding incisions using scalpel. 3. In the epithelium of rat tongue mucosa, CD44 expression in healing laser wounds and scalpel incisions were similar. 4. In the lamina propria and muscle layer, CD44 expression in healing laser wounds gradually increased earlier and decreased faster than scalpel incisions. Conclusively, it is suggested that pulsed Nd:YAG laser has more beneficial effect on the healing of wounded oral mucosa than scalpel in knew of CD44 expression.

• Nuclear Engineering and Technology
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• v.33 no.2
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• pp.175-183
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• 2001

Various welding processes are now available for end cap closure of nuclear fuel element such as TG(Tungsten Inert Gas) welding, magnetic resistance welding and laser welding. Even though the resistance and TIG welding processes are widely used for manufacturing commercial fuel elements, they can not be recommended for the remote seal welding of a fuel element at a hot cell facility due to the complexity of electrode alignment, difficulity in the replacement of parts in the remote manner and a large heat input for a thin sheath. Therefore, the Nd:YAG laser system using optical fiber transmission was selected for Zircaloy-4 end cap welding inside hot cell. The laser welding apparatus was developed using a pulsed Nd:YAG laser of 500 watt average power with optical fiber transmission. The weldability of laser welding was satisfactory with respect to the microstructures and mechanical properties comparing with TIG and resistance welding. The optimum operation processes of laser welding and the optical fiber transmission system for hot cell operation in a remote manner have been developed The effects of irradiation on the properties of the laser apparatus were also being studied.

• Laser Solutions
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• v.8 no.2
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• pp.13-20
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• 2005

Weldability is largely dependent on the phase evolution and the microstructure of the weld. For the weldability of the $Cu_{54}Ni_6Zr_{22}Ti_{18}$ bulk metallic glass, the crystallization affects the sensitivity of the weld to the brittle failure. In order to suppress the irreversible crystallization, Nd:YAG laser welding was chosen. The pulsed Nd:YAG laser was irradiated onto the BMG plate and the effects of the pulse shape [peak power intensity and pulse duration time] on the crystallinity were evaluated.

• Korean Journal of Optics and Photonics
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• v.6 no.4
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• pp.288-295
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• 1995

We have studied about spatial wavefront analysis of a pulsed laser output beam by means of an imaging unstable ring resonator with an infinite Fresnel number. We have constructed a Newtonian telescope type NBUR (Negative Branch Unstable Ring) Nd:YAG laser with 4 plane mirrors. Provided that the NBUR resonator is under self imaging condition, the resonator could be reduced diffraction effects which were occuring to the beam transmitting through the circular aperture of scraper mirror in the resonator. We have observed enhancement in the spatial coherence of wavefronts of laser beam due to the iterative round trips of the self imaging beam inside the ring resonator. The information on the spatial wavefronts was determined by the fringe patterns from Mach-Zehnder interferometer and the fringe analysis by means of the Fourier transform method showed the distortion of wavefronts of less than 0.2), In comparison with a standing wave type resonator, we have confirmed that the spatial coherence of the NBUR Nd:YAG laser output beam was enhanced as much as 75%. s 75%.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.6 no.1
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• pp.58-63
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• 2005

PTFE (polytetrafluoroethylene) thin films were prepared from the pellets of the graphite doped PTFE via pulsed laser ablation with 1064 nm Nd:YAG laser. The graphite powder converts the absorbed photon energy into thermal energy which is transmitted to nearby PTFE. The PTFE is decomposed by thermal process. The deposited films were transparent and crystalline. SEM (scanning electron microscopy) and AFM (atomic force microscopy) analyses indicated that the film surface morphology changed to fibrous structure with increasing thickness. The fluorine to carbon ratios of the film were 1.7 and molecular axis was parallel with (100) Si-wafer substrate. These results obtained by XPS (X-ray photoelectron spectroscopy), FTIR (fourier transform infrared spectroscopy) and XRD (X-ray diffraction).

• Journal of Oral Medicine and Pain
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• v.22 no.1
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• pp.125-135
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• 1997

The Author examined the clinical and histological changes on the dorsal tongue mucosa of the adult rats after lasing by pulsed Nd:YAG laser and incising with scalpel. The dorsal tongue was lased through 320$\mu\textrm{m}$optic fiber moving 2.5mm/second to make linear incision 5mm. The five conditions of lasing were three application with 1.0W, 1.75W, 3.0W and 3.0W under saline cooling, and single application with 3.0W at 20Hz. With scalpel, linear incisions through the surface epithelium were performed to 5mm in length. After observing the clinical changes of the incised wounds, the animals were sacrified and the tissues were excised to make the tissue specimens. The stained microscopic tissue slide were observed histologically under the microscope. The following results were obtained : 1. While incision with scalpel causes severe bleeding, lasing does not cause bleeding. 2. In three applications with 1.75W and 20Hz, tissue ablation was limited to areas contacted with optic fiber. 3. In three applications with 3.0W and 20Hz, deep incised wound, extensive destruction of the adjacent epithelium and charring were observed. 4. In three applications with 3.0W and 20Hz under saline cooling, tissue ablation was limite to the superficial mucosa and charring was not observed. 5. In single application with 3.0W and 20Hz, the shape of the incised wound was similar to that of the scalpel incision.

• Medical Lasers
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• v.9 no.2
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• pp.159-165
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• 2020

Background and Objectives The ultimate goal in current skin rejuvenation practice is to achieve a good result with minimal pain and downtime. Nonablative skin rejuvenation (NSR) is one technique. The efficacy of the long-pulsed 1064 nm Nd:YAG laser (LPNDY) has not been assessed in NSR. Materials and Methods Three target areas were selected (bilateral cheeks and glabellar region) in six volunteer subjects. A LPNDY with an integral skin temperature monitor delivered three stacked shots to each target area (1064 nm, 12 mm spot, 13 J/cm², 1 Hz) without any skin cooling or anesthesia. The skin temperature was recorded before, during, and after each set of shots using the system monitor and in real-time using a high-sensitivity (±0.001℃) near-infrared video camera. The skin reaction was observed with the naked eye, and pain and discomfort were assessed by the subjects during and after treatment. Results The subjects reported a mild feeling of heat with no discomfort during or after the test treatments. Mild erythema was observed around the treatment areas, without noticeable edema. A series of three ascending skin temperature stepwise peaks, with a decrease in skin temperature towards the baseline after the third shot, was observed consistently. The mean temperatures for shots 1, 2, and 3 for the cheeks were 39.5℃, 42.0℃, and 44.4℃, respectively, and for the glabella, 40.8℃, 43.9℃, and 46.2℃, respectively. Similar ranges were indicated on the system integral temperature monitor. Conclusion A set of three stacked pulses with the LPNDY at a low fluence achieved ideal dermal temperatures to achieve some dermal remodeling but without any downtime or adverse events. The temperature data from the integral thermal sensor matched the video camera measurements with practical accuracy for skin rejuvenation requirements. These data suggest that LPNDY would satisfy the necessary criteria to achieve effective NSR, but further studies will be needed to assess the actual results in clinical practice.

• International Journal of Korean Welding Society
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• v.3 no.1
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• pp.39-44
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• 2003

The welded specimens were made by butt welding of the 2 wires of 50mm length using the pulsed YAG laser. The laser welded wires were tested for investigating the shape memory effect and the ability of super elasticity. The fatigue properties of the welded wires were investigated using the rotary bending fatigue tester specially designed for wires. Moreover, the effect of defocusing distance during laser welding on the static and fatigue properties was Investigated. The shape memory effect and super elasticity of the laser welded wires were approximately identical with that of base metal at the test temperature below 353K. However, the welded wires were broken within elastic limit at the test temperature above 353k. Under the cyclic bending loading conditions, the welded wires could be useful only below the elastic limit, while the base metal had sufficient fatigue life even the stress induced M-phase region. The fatigue strength of the welded wires was about half of that of the base metal. The deterioration of the static and fatigue properties in the welded wires was proven to be from the large difference of the transformation behavior between the base metal and welded part that is caused by vaporization of Ni-content at the welded part during the welding process. The defocusing distance below 3mm acted more largely on lowering the strength of the welded wires than that of 6mm or 8mm.

• Journal of Oral Medicine and Pain
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• v.20 no.2
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• pp.429-447
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• 1995

This study was designed to determine the most effective concentration of fluoride and levels of laser irradiation for the remineralization of decayed teeth. After irradiation with a pulsed Nd:YAG laser and the topical application of fluoride, phosphate and fluoride concentration in enamel were measured. And then the changes on surface enamel using an scanning electron microscope were observed. Samples by extraction healthy, permanent, mandibular bovine teeth with no caries were obtained. Among them 371 healthy samples were selected and artificial carious lesions were made. 20 samples were assigned to each experimental group. After irradiation with a pulsed Nd:YAG laser with total energy densities of 10J/$\textrm{cm}^2$, 20J/$\textrm{cm}^2$ for each group. On the teeth, 2% NaF, 1.9% NH4F, 1.6% TiF4 Elmex gel(amine fluoride) and 1.23% APF gel were applied. After pH circulatory procedures, concentrations of fluoride with and Ionalyzer (Orion Research, Model 901, USA) and phosphates with an Uv/V is spectrophotometer (Uvikon 860, Kontrom Co, Switzerland) were measured. By etching the teeth in layers and measuring fluoride concentrations, a profile of fluoride penetration according to depth could be developed. And also the changes on the surface of the enamel using an electron scanning microscope were observed. The comparative analysis yielded the following results : 1. Phosphate concentration was low in all groups compared with the control group except for teeth treated Elmex gel, irradiated with 10J/$\textrm{cm}^2$ and 30J/$\textrm{cm}^2$ energy densities. Teeth treated with APF gel and 30J/$\textrm{cm}^2$ irradiation gad the lowest phosphate concentration. 2. Among all groups, fluoride concentrations in tooth enamel were highest in APF gel and NaF groups irradiated at 30J/$\textrm{cm}^2$. The APF gel group had the highest fluoride concentrations across all energy densities. 3. In the APF gel group, and the NaF group, the greater the energy density of the laser, the higher the fluoride concentrations in the enamel. 4. In all groups, the concentration of fluoride in the enamel by depth tended to decrease with depth. 5. Under the scanning electron microscope, under the condition of irradiation with 20J/$\textrm{cm}^2$, enamel crack was detected for the first time. In the NH4F group, spherical deposits were found on the surface of the enamel, and in the TiF4 group the surface of enamel was covered with an irregular, thin membranous mass in places. In the APF gel and NaF groups irradiated with 10J/$\textrm{cm}^2$, spherical and irregular particles covered the teeth. When these groups were irradiated at 20J/cm2, they were covered with amorphous crystals. These results suggest that one could obtain more effective anticariogenic effects without damage to teeth when less than 20J/$\textrm{cm}^2$ energy densities and APF gel are used.