• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제26권6호
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• pp.644-651
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• 2000

In cases of severe alveolar bony resorption in the edentulous posterior maxillae, implant placement is limited anatomically due to maxillary sinus. If the ridge is atrophic, the various bone grafting methods are required for the ridge augmentation. But the result of the onlay grafting procedure is not always promising. On the posterior maxilla, maxillary sinus mucosa lifting and bone grafting into the sinus floor, subantral augmentation(SA) technique are recommended. Various SA procedures have been developed for implant installation. We perfer to simultaneous block bone graft and implant installation through the residual alveolar ridge into the grafted block bone to fix the grafted bone and to gain the primary stability of the installed fixture. When a sagittal skeletal discrepancy in present due to the severe alveolar bony resorption of the maxilla, the advancement of the maxilla by Le Fort I osteotomy simultaneously with installation of implant fixtures combined with sinus lifting and interpositional bone graft procedure can be indicated. We applied various SA techniques for implant installtion to the 46 edentulous posterior maxillae, and total 154 implants were installed at our department from 1992 to 1999. Various SA techniques were classified in detail and the indications of each techniques were discussed. The changes of residual bony height following SA procedure were studied. The results were as follows. 1. The SA procedure combined with bone graft and simultaneous fixture installation were performed in 41 cases, 126 fixtures were installed and 5 fixtures were removed out of them. Le Fort I osteotomy procedure combined with sinus lifting and interpositional bone graft simultaneous with fixture installation were performed in 5 cases. Total 28 fixtures were installed and 2 fixtures were removed so far. 2. Autogenous block bone graft into sinus floor were performed in 35 cases, autogenous particulated marrow cancellous bone(PMCB) graft in 9 cases, and demineralized human bone powder in 2 cases. The donor site for bone graft were anterior iliac bone in 39 cases, posterior iliac bone in 3 cases and mandibular symphysis in 1 case and mandibular ramus in 1 case. 3. In 9 cases with which SA procedure had been performed with the block bone graft, the change of pre- and postoperative residual bony height were measured using MPR(multiplanar reformatted)-CT. The mean residual bony height was 8.0mm preoperatively, 20.2mm at 6 months following up operation and we gained average 12.2mm alveolar bony height. So, we can recommend this one-stage subantral augmentation and fixture installation technique as a time conserving, safe and useful method for compromised posterior edentulous maxilla.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제36권5호
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• pp.402-407
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• 2010

Introduction: The planning of implant surgery is an important factor for the implant prosthesis. Stereolithographic (SLA) surgical stents based on a computer simulation are quite helpful for clinicians to perform the surgery as planned. Although many clinical and technical trials have been performed for computed tomography (CT)-guided implant stents to improve the surgical procedures and prosthetic treatment, there are still many problems to solve. We developed a system of a surgical guide based on 3 dimensional (3D) CT for implant therapy and achieved satisfactory results in the terms of planning and operation. Materials and Methods: Fifteen patients were selected and 30 implant fixtures were installed. The preoperative CT data for surgical planning were prepared after obtaining informed consent. Surgical planning was performed using the simulation program, Ondemend3D In2Guide. The stents were fabricated based on the simulation data containing information of the residual bone, the location of the nerve, and the expected design of the prostheses. After surgery with these customized stents, the accuracy and reproducibility of implant surgery were evaluated based on the computer simulation. The data of postoperative CT were used to confirm this system using the image fusion technique and compare the implant fixtures between the planned and implanted. Results: The mean error was 1.18 (${\pm}0.73$) mm at the occlusal center, 1.23 (${\pm}0.67$) mm at the apical center, and the axis error between the two fixtures was $3.25^{\circ}C$ (${\pm}3.00$). These stents showed superior accuracy in maxilla cases. The lateral side error at the apical center was significantly different from the error at the occlusal center but there were no significant differences between the premolars, 1st molars and 2nd molars. Conclusion: SLA surgical stents based on a computer simulation have the satisfactory accuracy and are expected to be useful for accurate planning and surgery if some errors can be improved.

• 한국인터넷방송통신학회논문지
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• 제10권5호
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• pp.271-276
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• 2010

본 연구에서는 무대 방송용 LED 스폿 조명기구를 자체적으로 설계, 제작하여 조도, 배광 및 색온도를 측정하였으며, 동일한 피사체를 LED 조명과 텅스텐 할로겐 조명을 번갈아 설치하여 인물의 영상을 카메라로 촬영한 영상을 비교하여 LED 조명기구의 대체 가능성을 연구하였다. 촬영한 피사체를 분석한 결과 LED 144[W] 조명기구가 텅스텐 할로겐 1[kW] 조명기구보다 더 영상이 밝기와 색감 면에서 더 우수하였다. 144[W] LED조명기구와 텅스텐 할로겐 1[kW] 조명기구의 사용 에너지를 측정한 결과 동일 조도기준으로 LED가 80[%] 이상의 에너지 절약효과가 있는 것으로 나타났다. 할로겐 텅스텐 1[kW] 조명기구와 LED 144[W] 조명기구의 배광과 조도 분포를 비교 검토한 결과 피사체를 집중적으로 조명하는 경우, 피조면의 조도가 높아 효과적인 조명이 가능하다. 6[m]정도 천고의 공연장이나, 스튜디오에서는 LED144[W] 조명기구는 조도 문제가 없어, 기존의 텅스텐 할로겐 1[KW] 조명기구를 1:1로 대체하는 것이 가능하다.

• 구강회복응용과학지
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• 제26권3호
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• pp.323-337
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• 2010

본 연구는 임플란트 상부 구조물 제작을 위한 pick-up 인상 채득시 flag type의 새로운 인상용 코핑을 이용하여 제작된 모형과 기존에 사용되고 있는 인상용 코핑에 의해 제작된 모형의 정확성을 3차원적으로 비교하여 새로운 형태의 인상용 코핑을 사용한 인상법의 유용성을 알아보고자 하였다. 아크릴릭 레진 블록으로 좌측은 전부 무치악, 우측은 제 2 소구치가 상실된 상악 기준 모형을 제작하였다. 상악 우측 제 2소구치, 좌측 중절치, 좌측 견치, 좌측 제 2 소구치, 좌측 제 2 대구치 부위에 외부 육각 연결 방식의 임플란트 고정체를 식립하였다. 기준 모형에 사용된 인상용 코핑 및 코핑 간에 연결 여부에 따라 세 가지 실험군으로 분류하였다; 임플란트 고정체에 flag type 의 인상용 코핑을 체결한 경우 (실험군 I), 기존 형태인 원통형의 인상용 코핑을 체결한 후 인상용 코핑을 자가 중합 아크릴릭 레진으로 연결한 경우 (실험군 Ii), 원통형 인상용 코핑을 체결한 후 자가 중합 레진으로 연결하지 않은 경우 (실험군 III). 총 15개의 모형을 제작하여 인상 채득하여 작업 모형을 제작한 후 기준 모형 및 작업 모형을 5번씩 측정하여 통계 처리하였다. flag type의 인상용 코핑을 이용하여 인상 채득한 군, 기존의 인상용 코핑을 자가 중합 레진으로 splinting하여 인상 채득한 군, 기존의 인상용 코핑을 splinting 하지 않고 인상 채득한 군의 작업 모형에서 각 임플란트 유사체 간 거리 차이는 통계적으로 유의하지 않았다(P >.05). 또한 동일 수평면에 대한 수직적 거리를 비교한 결과 flag type의 인상용 코핑을 사용하여 제작한 작업 모형이 Point 2에서는 기준 모형에 가장 근접한 수치를 보였고 Point 3에서는 오차가 가장 컸으며 이는 통계적으로 유의하였다(P <.05). 그 외 Point에서는 세 가지 방법 간에 통계적으로 유의한 차이는 없었다(P >.05). 새로운 인상용 코핑을 사용한 인상법은 기존의 인상용 코핑을 사용한 인상법과 비교적 유사한 정확성을 보여주었다.

• Journal of Periodontal and Implant Science
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• 제37권1호
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• pp.137-150
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• 2007

CADIA(Computer-assisted densitometric image analysis) method is used to analyze bone density changes around the implants. The usefullness and reproducibility of the method was assessed. We tried to find out if there is any possibility to quantitiate and qualitify peri-implant bone density change as time passes. And we concluded that this newly developed linear analysis is efficient for analyzing peri-implant bone density change non-Invasively. In this study, 2152 machined $Br{\aa}nemark$ fixtures installed from 1994 to 2002 in the department of Periodontics, Dental hospital of College of Dentistry, Yonsei University were included. Of these fixtures 22 radiographically analyzable failed fixtures were used as experimental group, and 22 successful implants placed in the same patient were used as control group. 1. 57 out of 1635 machined $Br{\aa}nemark$ standard and Mk II implants system failed, the survival rate was 96.5%. And 11 out of 517 machined $Br{\aa}nemark$ Mk III and Mk IV implants system failed, the survival rate was 97.9%. Total survival rate was 96.8%. 2. 22 failed implants were used for the analysis, 10 of which failed before prosthetic treatment due to infection and overheating. 12 failed due to overload after prosthetic treatment, 63.6% of which failed during the early phase of functional loading, i, e. before 1 year of loading. 3. Bone density change values around coronal region of the failed implants were $-6.54{\pm}6.35$, middle region were $-3.53{\pm}5.78$, apical region were $-0.75{\pm}10.33$, resulting in average of $-3.71{\pm}8.03$. 4. Bone density change values around coronal region of the successful implants were $4.25{\pm}4.66$, middle region were $6.33{\pm}5.02$, apical region were $9.89{\pm}4.67$, resulting in average of $6.27{\pm}5.29$. 5. There was a statistically significant difference between two groups (p<0.01). In conclusion, the linear analysis method using computer-assisted densitometric image analysis could be a useful method for the analysis of implants, and could be used for future implant researchs.

• 대한치과보철학회지
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• 제43권1호
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• pp.105-119
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• 2005

Statement of problem. As the effects of the various diameters of fixture and abutment screw on stress distribution was not yet examined, this study focused on the different design of single implant restoration using three dimensional finite element analysis. Purpose. This study was to compare five different fixture-abutment combinations for single implant supported restorations with different fixture and abutment screw diameters. Material of methods. The five kinds of finite element models were designed by 3 diameter fixtures ($\oslash$3.3, 3.75, 5.0 mm) with 3 different abutment screws $\oslash$1.5, 1.7, 2.0 mm). The crown for mandibular first molar was made using UCLA abutment according to Wheeler's anatomy. 244 N was applied at the central fossa with two different loading directions, vertically and obliquely (30$^{\circ}$) and at the buccal cusp vertically. Maximum von Mises stresses were recorded and compared in the supporting bone, crowns, fixtures, and abutment screws. Results. 1. The stresses in supporting bone and implant-abutment structure under oblique loading were greater than those under vertical or offset loading. The stresses under vertical loading were the least among 3 loading conditions regardless of the implant and abutment screw diameters. 2. The stresses in the narrow implants were greater than the wider implants. The narrow implant with narrow abutment screw showed highest stresses in the lingual crest, but the narrow implant with standard abutment screw showed highest stress in abutment screw. 3. The stresses of abutment screws were influenced by the diameter of fixtures and loading conditions. The wide implants showed least difference between two different abutment screw diameters. Conclusions. The wide implants showed lesser stresses than the narrow implants and affected least by the different abutment screw diameters. The narrow implants with standard abutment screw showed highest stresses in the lingual bony crest under oblique loading.

• 대한치과보철학회지
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• 제43권1호
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• pp.120-131
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• 2005

Statement of problem. More than 70% of patients who need the implant supported restoration are parially edentulous. The principles of design for implant supported fixed partial denture in mandibular posterior region are many and varied. Jurisdiction for their use is usually based on clinical evaluation. There are several areas or interest regarding the design of implant supported fixed partial denture in mandibular posterior region. 1) Straight and tripod configuration in implant placement, 2) Two restoration types such as individualized and splinted restorations. Purpose. The purpose of this study was to compare the amount and distribution of stress around the implant fixtures placed in the mandibular posterior region with two different arrangements and to evaluate the effects of splinting using the photoelastic stress analysis. Material & methods. 1) Production of study model: Mandibular partially edentulous model was waxed-up and duplicated with silicone and two models were poured in stone. 2) Fixture installation and photoelastic model construction: Using surveyor(Ney, USh), 3 fixtures(two 4.0 $\times$13 mm, one 5.0$\times$10 mm, Lifecore, USA) were insta)led in straight & tripod configurations. Silicone molds were made and poured in photoelastic resin (PL-2. Measurements group, USA). 3) Prostheses construction: Four 3-unit bridges (Type III gold alloy, Dongmyung co., Korea) were produced with nonhexed and hexed UCLA abutments and fitted with conventional methods. The abutments were tightened with 30 Ncm torque and the static loads were applied at 12 points of the occlusal surface. 4) Photoelastic stress analysis : The polarizer analyzer system with digital camera(S-2 Pro, Fujifilm, Japan) was used to take the photoelastic fringes and analysed using computer analysis program. Results. Solitary hexed UCLA restoration developed different stress patterns between two implant arrangement configurations, but there were no stress transfer to adjacent implants from the loaded implant in both configurations. However splinted restorations showed lesser amount of stresses in the loaded implants and showed stress transfer to adjacent implants in both configurations. Solitary hexed UCLA restoration with tripod configuration developed higher stresses in anterior and middle implants under loading than implants with straight configurations. Splintied 3 unit fixed partial dentures with tripod configuration showed higher stress development in posterior implant under loading but there were no obvious differences between two configurations. Conclusions. The tripod configuration of implant arrangement didn't show any advantages over the straight configuration. Splinting of 3 unit bridges with nonhexed UCLA abutments showed less stress development around the fixtures. Solitary hexed UCLA restoration developed tilting of implant fixture under offset loads.

• 대한치과보철학회지
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• 제44권3호
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• pp.295-313
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• 2006

Statement of problem. Higher fracture rates were reported for Branemark implants placed in the maxilla and for 3.75 mm diameter implants installed in the posterior region. Purpose. The purpose of this study was to investigate the fracture of a fixture by finite element analysis and to compare different diameter of fixtures according to the level of alveolar bone resorption. Material and Methods. The single implant and prosthesis was modeled in accordance with the geometric designs for the 3i implant systems. Models were processed by the software programs HyperMesh and ANSA. Three-dimensional finite element models were developed for; (1) a regular titanium implant 3.75 mm in diameter and 13 mm in length (2) a regular titanium implant 4.0 mm in diameter and 13 mm in length (3) a wide titanium implant 5.0 mm in diameter and 13 mm in length each with a cementation type abutment and titanium alloy screw. The abutment screws were subjected to a tightening torque of 30 Ncm. The amount of preload was hypothesized as 650 N, and round and flat type prostheses were 12 mm in diameter, 9 mm in height were loaded to 600 N. Four loading offset points (0, 2, 4, and 6 mm from the center of the implants) were evaluated. To evaluate fixture fracture by alveolar bone resorption, we investigated the stress distribution of the fixtures according to different alveola. bone loss levels (0, 1.5, 3.5, and 5.0 mm of alveolar bone loss). Using these 12 models (four degrees of bone loss and three implant diameters), the effects of load-ing offset, the effect of alveolar bone resorption and the size of fixtures were evaluated. The PAM-CRASH 2G simulation software was used for analysis of stress. The PAM-VIEW and HyperView programs were used for post processing. Results. The results from our experiment are as follows: 1. Preload maintains implant-abutment joint stability within a limited offset point against occlusal force. 2. Von Mises stress of the implant, abutment screw, abutment, and bone was decreased with in-creasing of the implant diameter. 3. With severe advancing of alveolar bone resorption, fracture of the 3.75 and the 4.0 mm diameter implant was possible. 4. With increasing of bending stress by loading offset, fracture of the abutment screw was possible.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1993년도 한국자동제어학술회의논문집(국내학술편); Seoul National University, Seoul; 20-22 Oct. 1993
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• pp.1089-1094
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• 1993

A pilot system for flexible automatic assembly has been built at ASRI in Seoul National University. The system is designed for being capable of assembling different variants and products. The system consists of three industrial robots, four free-flow conveyors, automatic tool changers, RCC and fixtures. This paper describes the concept and the technical solutions of the developed flexible assembly cell. Results of performance evaluation using colored petri net are also presented and discuss.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2008년도 International Meeting on Information Display
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• pp.1109-1111
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• 2008

High efficacy white OLEDs with low voltage, high quantum efficiency and outcoupling fixtures achieve total power efficacies of 89 lm/W to 102 lm/W, operating voltages between 2.8 V and 3.5 V at correlated color temperatures of 2,800 - 3,900 K and color rendering ~70, at 1,000 nits.