• 한국해양학회지:바다
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• 제14권4호
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• pp.195-204
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• 2009

인공위성 고도계로 측정한 해수면 높이 자료를 사용하여 준 실시간 동해 표층해류를 추정하기 위해, 세 가지 방법으로 평균 역학지형(또는 평균 해류장)을 계산하고 각각의 특징들을 살펴보았다. 프랑스 AVISO(Archiviing, Validation and Interpretation of Satellite Oceanographic data)는 인공위성 고도계 자료와 수치모델을 이용하여 전 지구 해양에 대하여 수평적으로 $0.25^{\circ}$의 해상도를 갖는 평균 역학지형을 계산하고 지형류 방정식을 적용하여 평균 해류장을 만들어 제공하고 있다. 동해에서 장기간 관측한 수온과 염분 자료를 사용하여 500 dbar를 기준면으로 사용한 역학적 해면(steric height)을 계산하고 이를 평균 여각지형으로 환산하였다. 또한 14년 동안 동행의 표층을 이동한 표층뜰개들(ARGOS)의 궤적을 이용하여 평균 해류장을 구하였다. 인공위성 고도계로 관측한 해수면 편차와 세 가지 평균 역학지형을 합하여 절대 역학지형을 얻고, 각각의 절대 역학지형에 지형류 방정식을 적용하여 세 가지 표층해류를 추정하였다. 각 방법으로 추정된 표층해류를 2005년에 동해 남서부 해역에서 선박장착 초음파 해류계(ADCP)로 관측한 해류 자료와 정량적으로 비교하였다. 육지에서 50 km 이상 떨어진 해역에서는 인공위성 고도계로 측정한 해수면 자료에 지형류 방정식을 적용하여 구한 표층해류와 현장 관측 해류의 상관계수(R)가 0.58~0.73이며 두 자료의 제곱 평균 제곱근 편차(Root Mean Square Deviation, RMSD)는 $17.1{\sim}21.8cm\;s^{-1}$이다. 육지에서 50 km 이내의 연안에서 두자료의 R이 0.06~0.46로 상대적으로 낮고 RMSD는 $15.5{\sim}28.0cm\;s^{-1}$이다. 이처럼 연안에서는 인공위성 고도계로 관측한 해수면 높이 자료의 오차가 크므로 향후 연안에 대해서는 새로운 표층해류 추정 방법에 대한 추가 연구가 필요하다.

• 한국정밀공학회지
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• 제19권10호
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• pp.147-155
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• 2002

In the stereolithography process, the accuracy of product depends on laser power, scan speed, scan width, scan pattern, layer thickness, resin characteristics and so on. Therefore, appropriate process parameters are required for an accurate prototype. This paper presents a method to determine the key process parameters, i.e., laser scan speed, hatching space, and layer thickness based on scan length, scan area, and layer slope. In order to determine these parameters, three neural networks are employed to represent operator’s experience and knowledge. Optimum values on scan speed, hatching space and layer thickness are recommended to improve the surface roughness and build time on the developed SLA machine.

• 대한치과보철학회지
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• 제45권6호
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• pp.795-804
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• 2007

Statement of problem. Nano-scale calcium-phosphate coating on the anodizing titanium surface using ion beam-assisted deposition (IBAD) has been recently introduced to improve the early osseointegration. However, not much is known about their surface characteristics that have influence on tissue-implant interaction. Purpose. This study was aimed to investigate microtopography, surface roughness, surface composition, and wettability of the titanium surface modified by the anodic oxidation and calcium phosphate coating using IBAD. Material and methods. Commercially pure titanium disks were used as substrates. The experiment was composed of four groups. Group MA surfaces represented machined surface. Group AN was anodized surface. Group CaP/AN was anodic oxidized and calcium phosphate coated surfaces. Group SLA surfaces were sandblasted and acid etched surfaces. The prepared titanium discs were examined as follows. The surface morphology of the discs was examined using SEM. The surface roughness was measured by a confocal laser scanning microscope. Phase components were analyzed using thin-film x-ray diffraction. Wettability analyses were performed by contact angle measurement with distilled water, formamide, bromonaphtalene and surface free energy calculation. Results. (1) The four groups showed specific microtopography respectively. Anodized and calcium phosphate coated specimens showed multiple micropores and tiny homogeneously distributed crystalline particles. (2) The order of surface roughness values were, from the lowest to the highest, machined group, anodized group, anodized and calcium phosphate deposited group, and sandblasted and acid etched group. (3) Anodized and calcium phosphate deposited group was found to have titanium and titanium anatase oxides and exhibited calcium phosphorous crystalline structures. (4) Surface wettability was increased in the order of calcium phosphate deposited group, machined group, anodized group, sandblasted and acid etched group. Conclusion. After ion beam-assisted deposition on anodized titanium, the microporous structure remained on the surface and many small calcium phosphorous crystals were formed on the porous surface. Nanoscale calcium phosphorous deposition induced roughness on the microporous surface but hydrophobicity was increased.

• 대한치과보철학회지
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• 제46권2호
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• pp.125-136
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• 2008

골유착 개념에 기반한 치과용 임플랜트가 $Br{\aa}nemark$ 등에 의해 도입된 이후로 치과 치료에서 임플랜트를 이용한 방법은 장기적으로 높은 성공률을 보여 왔다. 임플랜트를 이용한 치료법이 상실된 치아의 수복을 위해 우선적으로 고려되어야 할 중요한 방법으로 인식되면서 임플랜트를 이용한 방법을 선호하게 되었고 적용 범위 및 사용 빈도도 급증하였다. 예전에 비해서 국산 임플랜트의 사용도 증가하였으나 장기간의 임상적, 객관적인 자료를 가진 국산 임플랜트의 수는 많지 않은 상태이다. 본 연구는 SLA 표면 처리 및 외측 연결형의 국산 임플랜트에 관하여 18개월에서부터 57개월까지의 임상적, 방사선학적 결과에 대한 후향적 분석을 실시하였다. 연세대학교 치과대학병원에서 네오플란트$^{(R)}$ 임플랜트 (네오바이오텍, 서울, 한국)를 이용하여 치료받은 25명의 환자에게 식립된 96개의 임플랜트를 대상으로 하였고, 대상자 중 남성의 평균 연령은 63.5세, 여성의 평균 연령은 44.3세였다. 진료기록부를 통해 성별, 연령, 무치악 유형, 식립 위치, 식립된 임플랜트의 직경 및 길이, 2차 수술 여부, 보철물의 유형, 대합치의 유형, 임상적 합병증의 종류 및 빈도 등을 조사하여 그에 따른 분포 및 생존율의 차이와 함께 이들 항목이 변연골 흡수량에 미치는 영향을 조사하여 다음과 같은 결과를 얻었다. 1. 총 25명에게 식립된 96개의 임플랜트 중 2개가 실패하여 누적 생존율은 97.9%로 나타났다. 2. 정기검진이 가능했던 88개의 임플랜트에 대해서는 상악에서의 생존율이 96.2%, 하악에서의 생존율은 98.4%였고, 구치부에서의 생존율은 97.5%였으며 전치부에서의 생존율은 100%였다. 3. 보철물 장착 후 1년과 1년 이후의 연간 흡수량에서 남성이 여성보다 변연골 흡수량이 많았다 (P<0.05). 4. 임플랜트 지지 보철물 후방에 자연치가 존재하는 경우가 존재하지 않는 경우보다 보철물 장착 후 첫 1년과 1년 이후 모두에서 연간 흡수량이 적었다 (P<0.05). 5. 보철물 장착 1년 이후의 연간 흡수량은 전치보다 구치에서 더 많은 변연골 흡수를 보였다 (P<0.05). 6. 악궁 간, 보철물의 유형, 대합치의 유형, 2차 수술 여부에 따른 변연골 흡수량의 차이는 보이지 않았다 (P>0.05). 이상의 결과를 토대로 변연골 흡수량에 영향을 주는 요소로 성별, 무치악의 유형, 악궁 내 위치였으며, 악궁 간, 보철물의 유형, 대합치의 유형, 2차 수술 여부에 따른 변연골 흡수량 차이는 없었다. 본 연구에서 최대 57개월까지의 기간 동안 SLA 표면 처리 및 외측 연결형의 국산 임플랜트의 임상적인 성공률은 만족스러운 결과를 보였으며 변연골 흡수량도 임플랜트 성공기준에 부합하였으나, 이보다 더 장기적인 평가가 필요하며 다양한 국산 임플랜트 시스템에 대한 중장기적인 연구가 지속되어야 할 것이다.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제38권
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• pp.42.1-42.7
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• 2016

Background: The purpose of this retrospective study was to evaluate the clinical utility of an implant with a sandblasted, large-grit, acid-etched (SLA) surface and internal connection. Methods: Six patients who received dental implants in the Department of Oral and Maxillofacial Surgery, Chonnam National University Dental Hospital, were analyzed by factors influencing the success rate and marginal bone loss. Factors included patient's age, sex, implant installation site, whether bone graft was done, type of bone graft materials, approaching method if sinus lift was done, and the size of the fixture. In addition, the marginal bone loss was analyzed by using a radiograph. Results: All implants were successful, and the cumulative survival rate was 100 %. Average marginal bone loss of 6 months after the installation was 0.52 mm and 20 months after the functional loading was 1.06 mm. Total marginal bone resorption was 1.58 mm on average. There was no statistically significant difference in mesial and distal marginal bone loss. Conclusions: The short-term clinical success rate of the implant with an SLA surface and internal connection was satisfactory. Moreover, the marginal bone loss was also consistent with the implant success criteria.

• Journal of Periodontal and Implant Science
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• 제38권2호
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• pp.191-198
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• 2008

Purpose: Guided bone regeneration(GBR) has emerged as a treatment in the management of osseous defects associated with dental implants. But several studies have reported different degrees of success of guided bone regeneration, depending upon the type of barrier selected, presence or absence of an underlying graft material, types of graft material, feasibility of technique, and clinician's preference. The aim of the present study was to evaluate bone formation following dental implant placement with augmentation materials at dehiscence defects in dogs. Material and Methods: Standardized buccal dehiscence defects($3{\times}5\;mm$) were surgically 2 Mongrel dog's mandibles, each 8 SLA surface, 8 anodizing surface implants. Each buccal dehiscence defect received flap surgery only(no treatment, control), $Cytoflex^{(R)}$ membrane only, Resolut $XT^{(R)}$ membrane only, Resolut $XT^{(R)}+Osteon^{TM}$. Animals were sacrificed at 8 weeks postsurgery and block sections were harvested for histologic analysis. Resuts: All experimental group resulted in higher bone formation than control. Resolut $XT^{(R)}+Osteon^{TM}$ group resulted appeared highest defect resolution. There was no difference between SLA and anodizing surface, nonresorbable and resorbable membrane. Conclusion: GBR results in rapid and clinically relevant bone closure on dehiscence defects of the dental implants.

• 대한기계학회논문집A
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• 제26권11호
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• pp.2409-2414
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• 2002

The surfaces of prototypes become rough due to the stair-stepping which is the inevitable phenomenon in the Rapid Prototypes are not used only for the verification of feature. The grinding, coating, or the composition of them is a main operation in post-processing in which lots of costs and long build time are needed. The solution is proposed to increase the efficiency of rapid prototyping by minimizing or removing the composition of them is a main operation in post-processing in which lots of costs and long build time are needed. the solution is proposed to increase the efficiency of rapid prototyping by minimizing or removing the regions for post-processing. the factors to cause the surface roughness and their effects are analyzed through the experiments. Software modules are developed to predict the surface roughness of each face in the prototyping with the result. An experimental compensation method is developed to apply the modules to various RP equipments, materials and build styles. The build direction is searched with use of genetic algorithm to maximize the total areas of the surface of which roughness is better than the user-defined value.

• 한국생산제조학회지
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• 제24권3호
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• pp.334-341
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• 2015

This paper summarizes the results of an investigation into the environmental factors that have an indirect impact on parts quality, as well as those process variables and modeling information that have a direct impact. The effects of strength, surface hardness, roughness, and accuracy of shape, that is, qualities that users generally need to know, were evaluated with laminating direction experimentally. The 3D printing methods used in this experiment were fused deposition modeling (FDM), stereolithography apparatus (SLA), selective laser sintering (SLS), 3D printing (3DP) and laminated object manufacturing (LOM). The goal was to achieve a high standard of quality control and product quality by optimizing the fabrication process.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제41권6호
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• pp.317-321
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• 2015

Objectives: The purpose of this study is to evaluate five-year radiographic follow-up results of the Korean sandblasting with large grit, and acid etching (SLA)-treated implant system. Materials and Methods: The subjects of the study are 54 patients who have been followed-up to date, of the patients who underwent implant surgery from May 1, 2009 to April 30, 2011. In all, 176 implant placements were performed. Radiographs were taken before the first surgery, immediately after the first and second surgeries, immediately and six months after the final prosthesis installation, and every year after that. Bone loss was evaluated by the method suggested by Romanos and Nentwig. Results: A total of 176 implant placements were performed - 122 in men and 54 in women. These patients have been followed-up for an average of 4.9 years. In terms of prosthetic appliances, there were 156 bridges and 20 single prostheses. Nine implants installed in the maxillary molar area, three in the mandibular molar area and two in the maxillary premolar area were included in group M, with bone loss less than 2 mm at the crestal aspect of the implant. Of these, eight implants were single prostheses. In all, six implants failed - four in the mandible and two in the maxilla. All of these failures occurred in single-implant cases. The implant survival rate was 98.1% on the maxilla and 94.3% on the mandible, with an overall survival of 96.6%. Conclusion: Within the limitations of this study, implants with the SLA surface have a very superior survival rate in relatively poor bone environments such as the maxilla.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제31권1호
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• pp.41-45
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• 2009

Background: Reduced bone height is one of the major problems faced in restoring tooth loss with implants. By the use of short implants, it is possible to reduce complicated and invasive treatment such as bone graft, allowing more simple surgery. But short implants are generally considered to have lower success rates than that of standard implants. Purpose: To assess the results of short Straumann implants by a retrospective study of short Straumann implants with TPS(titanium plasma-sprayed) and SLA(sandblasted, large grit, acid etched) surfaces. Materials and methods: 173 implants in 106 patients who received short Straumann implant surgery(${\le}8\;mm$) in the department of oral and maxillofacial surgery, Kyunghee Dental Hospital, from February 1996 to October 2006 were selected and studied. All of the implants were followed up after prosthetic rehabilitation. The average follow-up period was 34 months with 119 months as the longest follow up period. The average follow-up period after prosthetic rehabilitation was 31 months. 64 females(60.4%) and 42 males(39.6%) participated in the research with the age range of 19 to 85(mean age 47). 20 patients(18.9%) were under 40, 85 patients(80.2%) were over 40 and under 70, and only one patient(0.9%) was over 70 years old. Results: 27 implants(15.6%) had TPS surface while 146 implants(84.4%) had SLA surface. 9 implants(5.2%) were 3.3, 108 implans(62.4%) were 4.1mm and 56 implants(32.4%) were 4.8mm in diameter. 167 implants(96.5%) were 8mm and 6 implants(3.5%) were 6mm in length. There were 24 implants(13.9%) on the maxillas and 149 implants(68.8%) on the mandibles. 119 implants(68.8%) were rehabilitated with FPD(fixed partial denture), 47 implants(27.2%) with single crowns and 4 implants(2.3%) with overdentures. Among the fixed partial dentures, 30 of them were splinted with short implants only. After over an year of follow-up period, 139 implants(96.5%) out of 144 implants showed marginal bone loss of less than 1mm. 3 out of 173 implants failed showing 98.27% survival rate. Conclusions: The use of short Straumann implants(${\le}8mm$) can be a simple and reliable treatment method in minimal residual bone height.