• Journal of Periodontal and Implant Science
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• 제29권1호
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• pp.233-249
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• 1999

Primary fixation is one of the most important factor in establishing adequate osseointegration between implant and bone. To evaluate the initial healing response of bone around implants without primary bone contact, this study was designed to create considerable space between implant and bone in 5 mongrel dogs, about 1-year old. After 3 holes of 6.0mm in diameter were prepared at the femur neck of the dogs, commercially pure titanium thread type implants(STERI-$OSS^{(R)}$), 8mm in length and 3.8mm, 5.0mm and 6.0mm in diameter, were inserted. Implants were supported by only nonresorbable membrane($Teflon^{(R)}$), and the penetration of upper soft tissue into the gap was inhibited by it. The each implant was positioned in the center of the drilled hole. 9 implants with different diameters were inserted in 3 dogs for histologic observation, and 12 were inserted in 2 dogs for mobility test and removal torque test.Fluorescent dyes were injected in order of Doxycycline, Alizarin Red S, and Calcein at intervals of 2 weeks. At 4-, 8-, and 12-week after placement, 3 dogs were sacrificed for histologic observation, and at 8- and 12-week after placement, 2 dogs were sacrificed for mobility test using $Periotest^{(R)}$ (Simens AG, Bensheim, Germany) and torque test using Autograph AGS-1000D $series^{(R)}$(Japan). The result were as follows: 1. The wider the gap between bone and implant was, the less bone maturity was, and the later osseointegration was occurred. Trabecular direction of new bone around implant was changed from parallel to perpendicular to the implant, and the gap was filled with new bone, over time. 2. There was a decreasing tendency over time in the mobility of all implants, but the wider gap between bone and implant was, the smaller decrease of the mobility was. 3. There was a increasing tendency over time in the removal torque gauge of all implants, and the wider gap was, the smaller increase of the removal torque gauge was. The results suggest that osseointegration in case of implant without primary bone contact may be obtained by guided bone regeneration technique with prolonged healing period, but the time of second surgery should be considered carefully.

• Journal of Periodontal and Implant Science
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• 제41권2호
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• pp.86-91
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• 2011

Purpose: The aim of this study was to analyze the short-term predictability and reliability of Astra Tech implants according to the demographical distribution of patients and condition of implant sites and location of implants. Methods: Among patients treated with Astra Tech implant (Astra Tech AB) in the Department of Periodontology at the Dental Hospital of Yonsei University of College of Dentisry and K Dental Clinic from May 2004 to March 2009, 195 implants in 98 patients which had been restored more than 6 months ago were reviewed in this study. Following data were reviewed from patient charts and implants success rate was examined: 1) patient type and implant location, 2) bone status at the implant site, 3) diameter and length of the placed implants, 4) presence or absence of bone augmentation and types of the augmentation. Results: The results from this study are as follows: 1) most implants were placed in the molar area, especially 1st molar area of maxilla, 2) most implants were placed at $D_2$ and $D_3$ bone type, 3) most implants were placed in areas of B and C bone quantity, 4) autogenous and alloplastic bone graft and artificial membrane were used for placement of 74 implants. Conclusions: Short-term survival rate of Astra Tech implants was 100%.

• Journal of Korean Neurosurgical Society
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• 제49권6호
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• pp.351-354
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• 2011

Objective : This investigation was conducted to evaluate a new, safe entry point for the C2 pedicle screw, determined using the anatomical landmarks of the C2 lateral mass, the lamina, and the isthmus of the pars interarticularis. Methods : Fifteen patients underwent bilateral C1 lateral mass-C2 pedicle screw fixation, combined with posterior wiring. The C2 pedicle screw was inserted at the entry point determined using the following method : 4 mm lateral to and 4 mm inferior to the transitional point (from the superior end line of the lamina to the isthmus of the pars interarticularis). After a small hole was made with a high-speed drill, the taper was inserted with a 30 degree convergence in the cephalad direction. Other surgical procedures were performed according to Harm's description. Preoperatively, careful evaluation was performed with a cervical X-ray for C1-C2 alignment, magnetic resonance imaging for spinal cord and ligamentous structures, and a contrast-enhanced 3-dimensional computed tomogram (3-D CT) for bony anatomy and the course of the vertebral artery. A 3-D CT was checked postoperatively to evaluate screw placement Results : Bone fusion was achieved in all 15 patients (100%) without screw violation into the spinal canal, vertebral artery injury, or hardware failure. Occipital neuralgia developed in one patient, but this subsided after a C2 ganglion block. Conclusion : C2 transpedicular screw fixation can be easily and safely performed using the entry point of the present study. However, careful preoperative radiographic evaluation, regardless of methods, is mandatory.

• The Journal of Advanced Prosthodontics
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• 제9권6호
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• pp.470-475
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• 2017

PURPOSE. The purpose of this study was to identify the complex course of the mandibular canal using 3D reconstruction of microCT images and to provide the diagram for clinicians to help them understand at the interforaminal region in Korean. MATERIALS AND METHODS. Twenty-six hemimandibles obtained from cadavers were examined using microCT, and the images were reconstructed. At both the midpoint of mental foramen and the tip of anterior loop, the bucco-lingual position, the height from the mandibular inferior border, the horizontal distance between two points, and position relative to tooth site on the mandibular canal were measured. The angle that the mental canal diverges from the mandibular canal was measured in posterior-superior and lateral-superior direction. RESULTS. The buccal distance from the mandibular canal was significantly much shorter than lingual distance at both the mental foramen and the tip of anterior loop. The mandibular canal at the tip of anterior loop was significantly located closer to buccal side and higher than at the mental foramen. And the mental canal most commonly diverged from the mandibular canal below the first premolar by approximately $50^{\circ}$ posterior-superior and $41^{\circ}$ lateral-superior direction, which had with a mean length of 5.19 mm in front of the mental foramen, and exited to the mental foramen below the second premolar. CONCLUSION. These results suggest that it could form a hazardous tetrahedron space at the interforaminal region, thus, the clinician need to pay attention to the width of a premolar tooth from the mental foramen during dental implant placement.

• 구강회복응용과학지
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• 제34권1호
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• pp.46-55
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• 2018

치조골의 흡수와 치주조직의 염증을 동반한 심한 치주질환 환자에서 임플란트를 통한 구강 회복은 임상적으로 어려움이 있다. 하지만 골 형태에 따른 적절한 임플란트 식립 위치를 선정한다면 불필요한 골 이식이나 연조직 수술을 최소로 할 수 있다. 최근에는 cone beam CT 촬영과 소프트웨어를 이용하여 환자의 해부학적 형태와 보철적인 위치를 고려하여 임플란트 식립 위치를 선정할 수 있게 되었고 3D printing 기술을 통해 제작된 surgical guide를 통해 계획된 위치로 정확한 수술이 가능하게 되었다. 본 증례는 70세 여성 환자로 심한 치주질환으로 인해 전악 치아의 발치가 필요하였으며 임플란트 지지 고정성 보철물로 전악 구강회복을 시행하였다. 수술 시에는 보철적인 위치를 고려한 surgical guide를 이용해 flapless 방식으로 임플란트를 식립하였고 수술 전에 CAD/CAM 방식으로 제작된 임시보철물을 즉시 부하하였다. 이후 맞춤형 지대주와 지르코니아를 이용한 보철물을 제작하였으며, 만족스러운 심미 및 기능 회복을 보였기에 보고하는 바이다.

• 대한치과보철학회지
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• 제57권1호
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• pp.57-65
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• 2019

Computer guided implant surgery와 computer-aided design/computer-aided manufacturing, computer guided implant surgery (CAD/CAM) 기술의 발전은 수복 기반 임플란트 치료의 완성도를 한층 더 높였으며, 3D printing을 통한 국소의치의 제작도 빈도가 늘고 있다. 본 증례는 디지털 치의학의 작업 흐름을 따라서 콘빔컴퓨터단층촬영을 통한 치료 계획 수립 및 수술용 스텐트의 제작과 그를 바탕으로 한 임플란트 식립을 하였으며, 맞춤 지대주와 보철물을 제작하였다. 그 후 전자 서베잉과 3D printing을 통한 국소의치 금속 구조물 및 최종적으로 지르코니아 온레이의 제작을 통해 전악 수복을 완성하여 기능과 심미적으로 만족스러운 결과를 얻을 수 있었다.

• Geomechanics and Engineering
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• 제29권4호
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• pp.471-486
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• 2022

The effect of segmental joints is one of main importance for the segmental lining design when tunnels are excavated by a mechanized process. In this paper, segmental tunnel linings are analyzed by two numerical methods, namely the Beam-Spring Method (BSM) and the Solid-Interface Method (SIM). For this purpose, the Tehran Subway Line 6 Tunnel is considered to be the reference case. Comprehensive 2D numerical simulations are performed considering the soil's calibrated plastic hardening model (PH). Also, an advanced 3D numerical model was used to obtain the stress relaxation value. The SIM numerical model is conducted to calculate the average rotational stiffness of the longitudinal joints considering the joints bending moment distribution and joints openings. Then, based on the BSM, a sensitivity analysis was performed to investigate the influence of the ground rigidity, depth to diameter ratios, slippage between the segment and ground, segment thickness, number of segments and pattern of joints. The findings indicate that when the longitudinal joints are flexible, the soil-segment interaction effect is significant. The joint rotational stiffness effect becomes remarkable with increasing the segment thickness, segment number, and tunnel depth. The pattern of longitudinal joints, in addition to the joint stiffness ratio and number of segments, also depends on the placement of longitudinal joints of the key segment in the tunnel crown (similar to patterns B and B').

• Journal of Trauma and Injury
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• 제27권2호
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• pp.33-37
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• 2014

Central venous catheterization through a subclavian approach is indicated for some special purposes but it may cause many complications such as infection, bleeding, pneumothorax, thrombosis, air embolization, arrhythmia, myocardial perforation, and nerve injury. A case involving a mistaken central venous catheterization into the right vertebral artery through the subclavian artery is presented. A 33-year-old man who had deteriorated mentality after head injury underwent an emergency craniotomy for acute epidural hematomas on the right frontal and temporal convexities. His mentality improved rapidly, but he complained of continuous severe pain in the right posterior neck even though he had no previous symptom or past medical history of such pain. Three-dimensional cervical spine computed tomography (3D-CT) was performed first to rule out unconfirmed cervical injuries and it revealed a linear radiopaque material intrathoracically from the level of the 1st rib up to the level of C6 in the right vertebral foramen. An additional neck CT was performed, and the subclavian catheter was indwelling in the right vertebral artery through right subclavian artery. For the purpose of proper fluid infusion and central venous pressure monitoring, the subclavian vein catheterization had been performed in the operation room after general anesthesia induction before the craniotomy. Sufficient anatomical consideration and prudence is essential because inadvertent arterial cannulation at a non-compressible site is a highly risky iatrogenic complication of central venous line placement.

• 대한치과의사협회지
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• 제54권2호
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• pp.134-141
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• 2016

Use of ready-made orthodontic appliance can lead to inefficiencies in the final stages of the orthodontic treatment. Because patients' teeth have anatomic variations, brackets that have been designed to fit on average tooth surface may result in positional discrepancies when leveling and alignment is completed. As a result, additional steps such as rebonding, wire bending and use of auxiliaries may be needed. Even in patients who have normal tooth anatomy and proper tooth size relationships, precise bracket placement is crucial in order to efficiently control the tooth positions. Digital models can provide advantages in clinical orthodontics as virtual tooth setup could be performed, and clinicians can easily visualize the predicted final occlusion. Through this setup model, customized brackets with individualized prescription and archwires that optimally fit with the patients' dental arches can be produced using CAD/CAM technology. Also, the brackets can be accurately placed with an aid of 3D-printed jigs. The purpose of this article is to introduce the commonly used labial and lingual customized orthodontic appliance systems using digital technology.

• 한국해양공학회지
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• 제23권1호
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• pp.109-113
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• 2009

Several tidal current power plants are being planned and constructed in Korea utilizing the strong tidal currents along the west and south coasts. A tidal current reaches 9.7 m on the west coast; there are few potential regions for tidal current power generation. The construction of a dam to store water can prevent the circulation of water, causing a great environmental impact on the coast and estuary. The tidal barrage could produce a large amount of power, but it should be carefully considered. The purpose of developing renewable energies is to minimize the environmental impact and to maximize the utilization of clean energy. To produce a great quantity of power, tidal current farms require the placement of numerous units in the ocean. The power generation is very dependent on the size of the rotor and the incoming flow velocity. Also, the interactions between devices contribute greatly to the production of power. The efficiency of a power farm is estimated to determine the production rate. This paper introduces 3 D interaction problems between rotating rotors, considering the axial, transverse, and diagonal distances between horizontal axis tidal current devices.