• Journal of Oral Medicine and Pain
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• v.30 no.1
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• pp.131-140
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• 2005

The purpose of this study was to examine the ablation rate of Er: YAG laser irradiation on dentin and enamel and to observe the microscopic structures of cavities formed after ablation of enamel and dentin in using a bur and cavities formed after ablation using laser. Er:YAG laser irradiated at 200 mJ, 250mJ, 300mJ at the frequency of 20Hz, 15Hz. The following results were obtained : 1. The ablation rate of dentin groups at power of 3 W-6 W was about $1.103{\sim}2.639mm^3/sec$ and there were no significant differences between power of 4.5 W$\sim$6 W. 2. The ablation rate of enamel groups at power of 3 W-6 W was about $0.413{\sim}0.969mm^3/sec$ and there were no significant differences between power of 4 W$\sim$6 W. 3. With SEM examination of the cavity surface treated with the conventional high speed bur revealed relatively flat appearance almost covered with a debris like smear layer. 4. With SEM examination of the lased surface of dentin groups revealed no smear layer and no debris and openings of dentinal tubules were clearly opened. But the lased surfaces of the groups over 3 W were irregular and particles were loosely attached on it. 5. With SEM examination of the lased surface of enamel groups revealed severely destructed surface at the 6 W group and melting drop materials at the 3 W group. But the lased surface of 4 W group revealed clearly ablated surface. Therefore when cutting teeth using Er:YAG laser, the lasing power which can make effective ablation rate and minimize the thermal effect could be 3W at dentin and 4W at enamel. But, further studies and additional data collection will be necessary for appropriate lasing condition of Er:YAG laser.

• Applied Chemistry for Engineering
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• v.32 no.3
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• pp.299-304
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• 2021

This study focuses on the preparation of acetaminophen (AP) imprinted functional biomaterials for a transdermal drug delivery using mung bean starch (MBS), polyvinyl alcohol (PVA), sodium benzoate (S) as a crosslinking agent, glycerol (GL) as a plasticizer, and melanin (MEL) as a photothermal agent. The prepared AP imprinted biomaterials were characterized using FE-SEM and their physical properties were evaluated. The photothermal effect and AP release property for functional biomaterials were examined with the irradiation of near infrared (NIR) laser (1.5 W/cm²). When the NIR laser was irradiated on functional biomaterials with/without the addition of MEL, the temperature of MEL added biomaterial increased from 25 ℃ to 41 ℃, whereas the biomaterial without MEL increased from 25 ℃ to 28 ℃. Results indicate that there is the photothermal effect of prepared biomaterial with the addition of MEL. Based on the results, AP release properties were evaluated using standard buffer solutions and artificial skin. It was found that AP release rates of MEL added AP loaded biomaterials were 1.2 times faster than those of MEL non-added AP loaded biomaterials when irradiating with NIR laser. We envision that the developed functional biomaterials can be utilized for an acute pain-killing treatment.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.1
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• pp.157-171
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• 1990

The heat transfer problem associated with pulse technique for measuring thermal diffusivity was solved by means of Green function. The obtained general solution was discussed so as to apply for all possible cases; kinds of boundary condition and heat source, irradiation positions of heat pulse, radius of heat pulse, one-and two-dimensional heat flow, finite pulse time effects and radiation heat loss systems. Experimentally, the laser flash lamp was used as heat source for measuring thermal diffusivity of low carbon, aluminium chilled steel plate, which was heavily rolled in order to measure the variation of thermal diffusivity in the temperature range from room temperature through 500.deg. C. The derived results are (1) materials produced from same furnace showed a somewhat different thermal diffusivity values. (2) the thermal diffusivity value of rolled material was smaller than unrolled material and the difference decreased as increasing temperature. (3) the thermal diffusivity value of an annealed and temper rolled material was larger than the value of a cold rolled material, even thought smaller than unrolled material. (4) In case of heavy rolled material, there was no consistent relationships between the thermal diffusivity and the reduction in thickness.

• Journal of the Korean Society of Radiology
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• v.14 no.6
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• pp.833-839
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• 2020

Globally, infection prevention and social awareness have been greatly changed by the severe acute respiratory syndrome coronavirus, and as a result, the infection control guidelines and procedures for patients with high exposure to hospital-acquired infection are further strengthened and management and monitoring are more thorough. In order to prevent infection, sterilization should be carried out with the highest priority, and we will find a sterilization method that is low in cost, easy to install, and easy to operate, to present appropriate sterilization effects. In this study, the UV sterilizer was used to contaminate the caries bacteria with an output of 4 W and irradiation time of 60, 150, and 300 sec, and the laser was irradiated with outputs of 0.8 and 1.5 W at wavelengths of 266 and 355 nm, respectively. Ultraviolet sterilizer showed safety in infection prevention at over 150 sec, and laser showed safety in prevention at 1.5 W, 0.8 W, and 266 nm. As a result, the higher the output and the wavelength closer to 253.7 nm, the better the sterilization effect.

• Journal of Oral Medicine and Pain
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• v.26 no.4
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• pp.395-406
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• 2001

지난 수십년동안, 다양한 레이저기기를 이용하여 치아 경조직에 대한 응용 실험을 수행되었다. 그러나, 발생한 주요한 문제는 열발생과 플라즈마 형성과 같은 부작용이 지속된다는 점이었다. 실망스러운 실험결과에 따라 치아 삭제에 대한 레이저의 응용에 대한 연구가 거의 진행되지 못하였다. 본 연구의 목적은 국내에서 처음으로 개발된 얼비움레이저기기를 사용하여 다양한 에너지 수준과 다양한 펄스빈도에서 법랑질의 삭제율을 비교하고자 하였다. 본 연구에 사용된 레이저기기는 국내에서 최초로 개발된 $2.94{\mu}m$ 펄스를 $250{\mu}s$ 방출하는 얼비움야그레이저 기기이다. 기기의 에너지는 20 mJ에서 350 mJ까지 다양하게 방출하며, 최대 출력은 3.5 W이다. 22개의 치아를 에폭시 레진에 포매하고 경화하였다. 치아의 법랑질을 회전 다이아몬드 칼을 흐르는 물과 함께 사용하여 협측 또는 설측으로 평탄하게 삭제하였다. 제작된 법랑질표면은 6개의 구획으로 구분하여 에너지 수준과 펄스빈도에 따라 조사하였다. 본 연구에서 사용된 표본 수는 132개이며, 삭제율을 조사하기 위한 모든 표본은 22개의 실험 군으로 분류하였다. 실험결과는 다음과 같다. 1. 에너지 수준간에는 유의한 삭제율의 차이가 있었다. 2. 40 및 80 mJ로 조사한 경우에는 펄스빈도 간에 차이가 없었지만, 120 mJ의 출력으로 동일한 에너지를 조사한 경우에는 20 Hz가 40 또는 80 mJ로 조사한 경우 보다 가장 삭제효과가 높았다. 3. 연속조사 한 경우 조사시간 경과에 따라 법랑질의 삭제율은 증가되지 않았다. 결론적으로 효과적으로 법랑질을 삭제하기 위해서는 적절한 에너지와 펄스의 레이저를 사용해야 하며, 또한 항상 정확한 초점거리를 유지해야 할 것으로 사료된다.

• Journal of the Optical Society of Korea
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• v.9 no.1
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• pp.16-21
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• 2005

Using a cantilever type nanoprobe having a 100㎚m aperture at the apex of the pyramidal tip of a near-field scanning optical microscope (NSOM), nanopatterning of polymer films are conducted. Two different types of polymer, namely a positive photoresist (DPR-i5500) and an azopolymer (Poly disperse orange-3), spincoated on a silicon wafer are used as the substrate. A He-Cd laser with a wavelength of 442㎚ is employed as the illumination source. The optical near-field produced at the tip of the nanoprobe induces a photochemical reaction on the irradiated region, leading to the fabrication of nanostructures below the diffraction limit of the laser light. By controlling the process parameters properly, nanopatterns as small as 100㎚ are produced on both the photoresist and azopolymer samples. The shape and size variations of the nanopatterns are examined with respect to the key process parameters such as laser beam power, irradiation time or scanning speed of the probe, operation modes of the NSOM (DC and AC modes), etc. The characteristic features during the fabrication of ordered structures such as dot or line arrays using NSOM lithography are investigated. Not only the direct writing of nano array structures on the polymer films but also the fabrication of NSOM-written patterns on the silicon substrate were investigated by introducing a passivation layer over the silicon surface. Possible application of thereby developed NSOM lithography technology to the fabrication of data storage is discussed.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.51 no.6
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• pp.229-235
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• 2002

This paper presents the fabrication of polycrystalline thin film transistor(TFT) using sequential lateral solidification(SLS) of amorphous silicon. The fabricated SLS TFT showed high Performance suitable for active matrix liquid crystal display(AMLCD). The SLS process involves (1) a complete melting of selected area via irradiation through a patterned mask, and (2) a precisely controlled pulse translation of the sample with respect to the mask over a distance shorter than the super lateral growth(SLG) distance so that lateral growth extended over a number of iterative steps. The SLS experiment was performed with 550$\AA$ a-Si using 308nm XeCl laser having $2\mu\textrm{m}$ width. Irradiated laser energy density is 310mJ/$\textrm{cm}^2$ and pulse duration time was 25ns. The translation distance was 0.6$\mu$m/pulse, 0.8$\mu$m/pulse respectively. As a result, a directly solidified grain was obtained. Thin film transistors (TFTs) were fabricated on the poly-Si film made by SLS process. The characteristics of fabricated SLS p -type poly-Si TFT device with 2$\mu\textrm{m}$ channel width and 2$\mu\textrm{m}$ channel length showed the mobility of 115.5$\textrm{cm}^2$/V.s, the threshold voltage of -1.78V, subthreshold slope of 0.29V/dec, $I_{off}$ current of 7$\times$10$^{-l4}$A at $V_{DS}$ =-0.1V and $I_{on}$ / $I_{off}$ ratio of 2.4$\times$10$^{7}$ at $V_{DS}$ =-0.1V. As a result, SLS TFT showed superior characteristics to conventional poly-Si TFTs with identical geometry.y.y.y.

• The Journal of Advanced Prosthodontics
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• v.11 no.4
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• pp.223-231
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• 2019

PURPOSE. The purpose of this study was to evaluate the shear bond strength (SBS) of an indirect resin composite (IRC) to the various resin matrix ceramic (RMC) blocks using different surface treatments. MATERIALS AND METHODS. Ninety-nine cubic RMC specimens consisting of a resin nanoceramic (RNC), a polymer-infiltrated hybrid ceramic (PIHC), and a flexible hybrid ceramic (FHC) were divided randomly into three surface treatment subgroups (n = 11). In the experimental groups, untreated (Cnt), tribochemical silica coating (Tbc), and Neodymium-Doped Yttrium Aluminum Garnet (Nd:YAG) laser irradiation (Lsr) with 3 W (150 mJ/pulse, 20 Hz for 20 sec.) were used as surface treatments. An indirect composite resin (IRC) was layered with a disc-shape mold ($2{\times}3mm$) onto the treated-ceramic surfaces and the specimens submitted to thermal cycling (6000 cycles, $5-55^{\circ}C$). The SBS test of specimens was performed using a universal testing machine and the specimens were examined with a scanning electron microscope to determine the failure mode. Data were statistically analyzed with two-way analysis of variance (ANOVA) and Tukey HSD test (${\alpha}=.05$). RESULTS. According to the two-way ANOVA, only the surface treatment parameter was statistically significant (P<.05) on the SBS of IRC to RMC. The SBS values of Lsr-applied RMC groups were significantly higher than Cnt groups for each RMC material, (P<.05). Significant differences were also determined between Tbc surface treatment applied and untreated (Cnt) PIHC materials (P=.039). CONCLUSION. For promoting a reliable bond strength during characterization of RMC with IRC, Nd:YAG laser or Tbc surface treatment technique should be used, putting in consideration the microstructure and composition of RMC materials and appropriate parameters for each material.

• Journal of Periodontal and Implant Science
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• v.52 no.1
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• pp.39-53
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• 2022

Purpose: This study evaluated the systemic and local effects of doxycycline (DOX) and low-intensity laser (LIL) treatment as adjuvants to scaling and root planing (SRP) in the treatment of experimental periodontitis in rats. Methods: The sample consisted of 180 male rats (Rattus norvegicus albinus, Wistar), of which 30 did not receive induction of periodontal disease (negative control [NC] group) and 150 received induction of periodontal disease in the lower first molar. After 7 days, the ligature was removed, and the animals were divided into the following groups: NT (no treatment), SRP (SRP), DOX (SRP and DOX irrigation), LIL (SRP and laser irradiation), and DOX+LIL (SRP, DOX, and LIL). The animals were euthanized at 7, 15, and 30 days; thereafter, biochemical, radiographic, histological, and immunohistochemical analyses were performed. Results: In the intragroup analysis, lower concentrations of α-1-glycoprotein acid (α-1-Ga) and complement 3 (C3) were observed in the DOX+LIL group than in all other groups at all time points, as well as lower levels of complement 4 (C4) at 15 and 30 days (P<0.001). Less bone loss was observed in the DOX, LIL, and DOX+LIL groups than in the NC and SRP groups at all time points (P<0.001). There was a smaller number of tartrate-resistant acid phosphatase (TRAP)-positive cells in the DOX+LIL group than in the other groups at all time points (P<0.001). Positive correlations were observed between the systemic levels of α-1-Ga, C3, and C4 and the number of TRAP-positive cells. Conclusions: The combination of DOX with LIL as SRP adjuvants was effective both systemically and locally for the treatment of experimental periodontitis in rats.

• The Korean Journal of Pain
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• v.5 no.2
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• pp.258-262
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• 1992

Herpes zoster is an acute infectious viral disease which affects the posterior spinal root ganglion of the spinal nerve. A single posterior spinal root ganglion or a small number of adjacent ones may be affected, usually on the same side. The corresponding ganglia of the cranial nerve may also be similarly affected. The causative virus, varicella zoster, belongs to the group of host-specific DNA viruses. Postherpetic neuralgia is a continuation of herpes zoster in older patients. Although spontaneous resolution of herpes zoster may be expected in most patients, a significant number experience intractable pain. Postherpetic neuralgia is one of the most difficult problems encountered by physicians. There are many methods for management of postherpetic neuralgia, but there is no method that results in complete remission. Laser has lately come into use to reduce several acute or chronic pains. In order to determine the degree of pain relief by laser, 27 patients of postherpetic neuralgia were irradiated with He Ne, Infrared, and $CO_2$ combine scan moded lasers two to three times per week. The results were as follows: 1) The most frequent site was thoracic vertebral nerve area. 2) Patients younger than 70 years of age showed an improvement rate of 57% vs 27% for those patients older than 70 years of age. 3) Laser therapy proved effective of those patients who received the laser treatment within one month of the onset of the disease. 4) For those patients who received treatment within one month of the disease and reflecting a 50% improvement rate, the average irradiation time was 5.7.