• Restorative Dentistry and Endodontics
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• 제38권3호
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• pp.119-127
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• 2013

The purpose of a root-end filling is to establish a seal between the root canal space and the periradicular tissues. As root-end filling materials come into contact with periradicular tissues, knowledge of the tissue response is crucial. Almost every available dental restorative material has been suggested as the root-end material of choice at a certain point in the past. This literature review on root-end filling materials will evaluate and comparatively analyse the biocompatibility and tissue response to these products, with primary focus on newly introduced materials.

• Journal of Oral Medicine and Pain
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• 제22권2호
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• pp.309-325
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• 1997

In order to set the lasing variables and evaluate, clinically, the therapeutic effects of a pulsed Nd:YAG laser on oral lesion, the author applied the laser energy from a fiberoptic delivered, free running, pulsed Nd:YAG laser (wavelength 1064nm, Pulse duration 120$\mu$sec, fiber diameter 200$\mu$m/320$\mu$m) to 22 cases of oral soft tissue lesions and 6 cases of oral hard tissue lesions. The obtained results were as follows : 1. The effective excision with contact mode and the effective hemostasis of accompanied bleeding with noncontact mode were occurred by lasing on oral soft tissue lesions with fiber diameter of 320$\mu$m under the variables of 2.0~4.0W and 20~50Hz which were controlled into high power/low pulses for excision, low power/high pulses for hemostasis, low power in granulation tissue and high power in fibrous tissue according to therapeutic goals and tissue conditions. 2. About 50% of decreasing effect on hypersensitivity was occurred by lasing with non-contact and contact mode on cervical abrasion which caused dentinal hypersensitivity with fiber diameter of 320$\mu$m under the variables of 0.7 - 1.0W and 10Hz which were applied 2~3 times with 1 week interval. 3. The effective sterilization of infected root canal and lesion of periapical abscess was occurred by lasing with contact and spiral modes on wall of root canal and periapical abscess with fiber diameter of 200$\mu$m of which the tip was placed about 1mm shorter than root canal length under the variables of 1.OW and 10Hz.

• 드라이브 ㆍ 컨트롤
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• 제17권4호
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• pp.141-151
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• 2020

The aim of this study was to analyze the safety factor of range-shift gear pairs on multi-purpose agricultural implement machinery for an optimal design of a transmission system. Gear-strengths such as bending and contact stress and safety factors were analyzed under three load conditions: an equivalent engine torque at plow tillage, a rated engine torque, and the maximum engine torque. Root and contact safety factor were calculated to be 3.88, 5.14, 2.24, 2.11, 2.21, 0.99 and 0.78, 0.94, 0.65, 0.68, 0.84, 0.85, respectively, under equivalent engine torque condition at the plow tillage. The root and contact safety factor were calculated to be 1.91, 2.53, 1.10, 1.04, 1.07, 0.48 and 0.55, 0.66, 0.46, 0.48, 0.59, 0.59, respectively, under rated engine torque condition. The root and contact safety factor were calculated to be 1.60, 2.11, 0.92, 0.87, 0.90, 0.40 and 0.51, 0.61, 0.42, 0.44, 0.54, 0.54, respectively, under the maximum engine torque condition. The multi-purpose agricultural implement machinery could be conducted under plow tillage operation. However, gear specifications for tooth surface need modification because the gear surface would be broken at all driving conditions as safety factors are lower than 1.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1989년도 한국자동제어학술회의논문집; Seoul, Korea; 27-28 Oct. 1989
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• pp.1080-1084
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• 1989

The motion of an workpiece to be manipulated is determined by the forces applied to the workpiece. During the contact between the robot hand and the workpiece, impulsive forces may dominate all other forces, and determine the ultimate success or failure of a task. Therefore, one of the important problems in the robot hands is the control of the initial impact force. In this paper, the problem of the force control of robot hand under system with contact force is presented. The principle of energy can be applied in the modelling of the impact force. In order to achieve stable contact and avoid bounces and vibrations, VSS is adopted in the design of the contact force controller. Some simulations are carried out for a pushing operation to control the contact force.

• 대한치과교정학회지
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• 제41권1호
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• pp.6-15
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• 2011

마이크로 임플란트 시술의 중요한 위험요인 중 하나로 치근접촉 문제가 있으나, 관련 연구는 결과 분석에 치중되어 있고, 치근접촉이 마이크로 임플란트 안정성 상실로 이어지는 기전에 대한 연구는 아직 미흡한 것으로 보인다. 이에, 본 연구에서는 생역학적 측면에서 그 영향을 분석하였다. Absoanchor 마이크로 임플란트(SH1312-7, Dentos Inc., Daegu, Korea) 첨부가 치근에 접촉되어 있을 때, 저작압 전달에 의한 마이크로 임플란트 변위가 인접골에 가하는 압축응력을 축대칭 유한요소모델을 사용하여 계산하였다. 요소별 응력이 해면골의 최대압축강도나, 치밀골의 비정상 골개조 임계능력을 넘을 경우 해당 요소를 순차적으로 해석모델에서 제거하며 실행한 6단계해석의 결과, 마이크로 임플란트에 인접한 해면골의 전체적인 파절과 과부하에 따른 치밀골의 비정상 골개조가 임플란트 지지력 상실에 주 요인이 될 것으로 평가되었다. 치밀골의 과부하 영역은 초기에는 치밀골판의 하부에 존재하였으나 상부로 확장되었고, 응력 재분포로 인한 감소효과 없이 양성 되먹임(positive feedback)으로 결국 치밀골 전 두께로 확대됨을 관찰하였다. 본 연구를 통해 치근접촉된 마이크로 임플란트가 인접골을 훼손시켜 안정성 상실로 이어지는 과정을 모사할 수 있었으며, 이로부터 치근접촉에 따른 마이크로 임플란트의 불량한 예후에 대한 생역학적 측면의 원인을 파악할 수 있었다.

• KSBB Journal
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• 제13권5호
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• pp.530-534
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• 1998

The addition of the ceramic powder as state of bare in culture medium has stimulated the growth of Achyranthes japonica in both the disorganized cell and the plantlet. The grwoth rate of Hyoscyamus niger adventitious root and Pylatycodon grandiflorum hairy root was enhanced up to 100 and 250%, respectively, even though Scopolia parviflora hairy root and Hyoscyamus albus adventitious root were not. The ceramic powder has enhanced the growth of H. niger adventitious root even in a test tube immersed into its culture medium to irradiate alone without any direct contact. The ceramic powder seems to have a significant role on both the growth and the physiological action of some plants.

• 대한소아치과학회지
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• 제24권3호
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• pp.710-717
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• 1997

Autotransplantation is the transplantation of embeded, impacted, or unerupted tooth, into extraction socket or surgically prepared socket in the same individual. Clinically, successful autotransplantation must show radiolucent space(periodontal ligament space) between transplanted tooth and supporting bone, lamina dura, no root resorption, no ankylosis, no inflammatory change, and physiologic tooth mobility. It is important that procedure is atraumatic, and the instruments should not contact the root surface during procedure. We performed autotransplantation of impacted mandibular canine that transversely located beneath the apices of the mandibular incisors with uncompletely developed apex. In radiographs and clinical evaluation, this transplant showed successful clinical finding except irregularity of mesial root surface after 14 months. It is conclued that transplantation of canine with $\frac{1}{2}{\sim}\frac{3}{4}$ root development provides a good chance of pulp survival, limited risk of root resorption and ensures sufficient final length, and is thus recommended.

• Computers and Concrete
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• 제26권2호
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• pp.107-114
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• 2020

In this study, a two dimensional model of receding contact problem has been analyzed using finite element method (FEM) based software ANSYS and ABAQUS. For this aim finite element modeling of elastic layer and two homogeneous, isotropic and symmetrical elastic quarter planes pressed by means of a rigid circular punch has been presented. Mass forces and friction are neglected in the solution. Since the problem is examined for the plane state, the thickness along the z-axis direction is taken as a unit. In order to check the accuracy of the present models, the obtained results are compared with the available results of the open literature as well as the results of two software are compared using Root Mean Square Error (RMSE) and good agreements are found. Numerical analyses are performed considering different values of the external load, rigid circular radius, quarter planes span length and material properties. The contact lengths and contact stresses of these values are examined, and their results are presented. Consequently, it is concluded that the considered non-dimensional quantities have noteworthy influence on the contact lengths and contact stress distributions, additionally if FEM analysis is used correctly, it can be an efficient alternative method to the analytical solutions that need time.

• 대한소아치과학회지
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• 제42권4호
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• pp.291-301
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• 2015

본 연구의 목적은 다양한 MTA 재료(ProRoot MTA, RetroMTA, Endocem Zr)에 대한 유치 치수 세포의 생활력 및 분화능을 비교 평가하는 것이다. 유치 치수세포는 각 재료별로 경화된 원형 디스크를 이용하여 직접법 및 간접법으로 세포 생활력을 관찰하였다. 또한 재료별 추출물을 이용하여 pH를 측정하였으며, alkaline phosphatase(ALP) 활성도 및 Alizarin Red S 염색법을 통하여 세포의 분화능을 관찰하였다. 직접법에서 유치 치수세포는 ProRoot MTA와 RetroMTA에서 Endocem Zr에 비해 높은 세포 생활력을 보였으나, 반면 간접법에서는 Endocem Zr에서 다른 재료에 비해 높은 세포 생활력이 관찰되었다. pH의 경우 Endocem Zr가 다른 두 재료에 비해 낮은 알칼리성을 나타냈다. 모든 재료에서 ALP 활성도는 대조군에 비해 증가하지 않았으며, Alizarin Red S 염색결과 유치 치수세포의 분화능이 대조군에 비해 낮았다. 본 실험에서 재료별 차이는 있었으나 모든 재료에서 어느 정도의 세포 독성이 관찰되었으며, 유치 치수세포의 생활력과 분화능을 증진시키지 못하였다. 하지만 Endocem Zr의 경우 ProRoot MTA나 RetroMTA에 비해 낮은 알칼리성과 높은 생활력을 보였다.

• Journal of Periodontal and Implant Science
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• 제32권2호
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• pp.303-314
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• 2002

This study was performed to evaluate the usability of Er:YAG laser for periodontal therapy. Forty dental root slabs ($5{\times}5{\times}2mm^3$) were prepared from human periodontally diseased extracted teeth and grouped into 4 groups: 1) control (root planing only), 2) root planing and irradiated with laser at 30mJ, 3) root planing and irradiated with laser at 60mJ, and 4) root planing and irradiated with laser at 100mJ. The root slabs were embedded in resin block before laser treatment. Er:YAG laser was irradiated under water irrigation with the tip held perpendicular to the root surface in contact mode. After Er:YAG laser irradiation or planing on the root surface, morphological changes have been observed under SEM, and the micro-hardness and Ca/P ratio were compared. 1. In the Control group, the root surface showed the directional change caused by root planing instrumentation, and the presence of smear layer, and no exposure of dentinal tubule was observed. Laser irradiated group showed surface changes with rough dentin surface of niche and depression and dentinal tubule exposure by the elimination of smear layer. 2. The micro-hardness of root surface in the laser irradiated group was higher than the control group. The higher energy output was applied, the higher micro-hardness on root surface was resulted. 3. The higher energy output was applied, the higher Ca/P ratio was observed. The higher Ca/P ratio in 60mJ group and 100mJ group was statistically significantly compared to the control group and the 30mJ group. These results suggest that Er:YAG laser irradiation on the periodontally diseased root surface could remove smear layer and increase the micro-hardness on root surface and Ca/P ratio which contribute to enhance the acid resistance of periodontally treated root surface.