• The Journal of Advanced Prosthodontics
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• 제10권5호
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• pp.381-387
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• 2018

PURPOSE. Cement-retained implant prostheses can lack proper retrievability during repair, and residual cement can cause peri-implantitis. The purpose of this in vitro study was to evaluate the influence of abutment height and convergence angle on the retrievability of cement-retained implant prostheses with lingual slots, known as retrievable cement-type slots (RCS). MATERIALS AND METHODS. We fabricated six types of titanium abutments (10 of each type) with two different heights (4 mm and 6 mm), three different convergence angles ($8^{\circ}$, $10^{\circ}$, and $12^{\circ}$), a sloped shoulder margin (0.6 mm depth), a rectangular shape ($6mm{\times}6.5mm$) with rounded edges, and a rectangular ledge ($2mm{\times}1mm$) for the RCS. One monolithic zirconia crown was fabricated for each abutment using a dental computer-aided design/computer-aided manufacturing system. The abutments and crowns were permanently cemented together with dual-curing resin cement, followed by 24 hours in demineralized water at room temperature. Using a custom-made device with a slot driver and torque gauge, we recorded the torque ($N{\cdot}cm$) required to remove the crowns. Statistical analysis was conducted using multiple regression analysis and Mann-Whitney U tests (${\alpha}=.05$). RESULTS. Removal torques significantly decreased as convergence angles increased. Multiple regression analysis showed no significant interaction between the abutment height and the convergence angle (Durbin-Watson ratio: 2.186). CONCLUSION. Within the limitations of this in vitro study, we suggest that the retrievability of cement-retained implant prostheses with RCS can be maintained by adjusting the abutment height and convergence angle, even when they are permanently cemented together.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2013년도 추계 학술논문 발표대회
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• pp.68-71
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• 2013

Reactive Powder Concrete (RPC) is an ultra high strength and high ductility cement-based composite material and has shown some promise as a new generation concrete in construction field. It is characterized by a silica fume-cement mixture with very low water-binder (w/b) ratio and very dense microstructure, which is formed using various powders such as cement, silica fume and very fine quartz sand (0.15~0.4mm) instead of ordinary coarse aggregate. However, the unit weight of cement in RPC is as high as 900~1,000 kg/㎥ due to the use of very fine sand instead of coarse aggregate, and a large volume of relatively expensive silica fume as a high reactivity pozzolan is also used, which is not produced in Korea and thus must be imported. Since the density of RPC has a heavy weight at 2.5~3.0 g/㎤. In this study, the modified RPC was made by the combination of ternary pozzolanic materials such as blast furnace slag and fly ash, silica fume in order to economically and practically feasible for Korea's situation. The fire resistance and structural behavior of the modified RPC exposed to high temperature were investigated.

• 한국지반신소재학회논문집
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• 제22권4호
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• pp.51-61
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• 2023

본 연구는 건축·건설물에서의 화재 시 구조물의 내화성능을 향상 시키기 위하여 시멘트 모르타르에 다공성 나노실리카(MSNs)에 ZnO입자가 결합된 형태의 분말과 PVA 섬유를 혼입한 공시체를 20~1100℃의 온도 영역에 노출 시켜 잔존압축강도 및 중량변화율을 측정하여 내화성능의 변화 여부를 알아보았다. 연구 결과, 시멘트 모르타르의 내화성능 향상에 나노실리카와 PVA 섬유를 같이 혼입한 경우 내화성능 향상에 기여는 없는 것으로 나타났다. 반면, 각각 나노실리카를 0.5% 혼입하는 경우와 PVA 섬유를 0.1vol% 혼입하는 경우 가장 양호한 내화성능 향상 실험결과를 나타내어 내화에 유리한 것으로 나타났다.

• 한국구조물진단유지관리공학회 논문집
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• 제20권4호
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• pp.9-18
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• 2016

이 연구에서는 태양열 에너지 저장용도로 사용하기 위한 시멘트 기반 복합재료의 열적 및 역학적 특성을 파악하였다. 다양한 시멘트 재료의 배합이 섬유보강 시멘트 기반 복합재료의 열적 및 역학적 특성에 미치는 영향을 파악하기 위한 실험연구를 수행하였다. 시멘트 기반 복합재료의 역학적 특성으로써 열싸이클 전과 후의 압축강도 및 인장강도를 측정하였다. 또한, 섬유보강 시멘트 기반 복합재료의 열적 특성으로써 열전도율과 비열을 측정하였다. OPC와 슬래그를 포함한 배합의 잔류압축강도가 가장 크게 나타난다. 그라파이트를 혼합한 배합의 열전도율이 크게 나타나며, 이는 그라파이트가 열저장 시스템의 효율적인 축열과 방열에 유리함을 의미한다. 또한, CSA 또는 지르코늄의 첨가는 섬유보강 복합재료의 비열을 증가시킨다. 실험연구결과는 잡광형 태양열 발전소에서 고성능 복합재료를 사용하는 열저장 시스템 설계에 기초자료로 활용될 수 있다.

• 구강회복응용과학지
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• 제32권3호
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• pp.240-245
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• 2016

치은 연하 변연을 갖는 임플란트 수복물 장착시 잔여 합착제의 제거는 임플란트 생물학적 합병증을 예방하기 위해 매우 중요하다. 치은 연하 잔여 합착제를 최소화하기 위해 인상용 실리콘이나 자가중합형 레진을 이용하여 복제 지대주를 제작하는 여러 방법이 소개되었다. 본 증례에서는 열가소성 접착제(hot melt adhesive material)를 이용하여 복제 임플란트 지대주(abutment replica)제작하는 방법을 소개하고자 한다. 이 방법은 간단하고 부가적인 기공과정이 필요 없어 진료실에서 쉽게 이용할 수 있어 이에 보고하는 바이다.

• 한국세라믹학회지
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• 제22권1호
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• pp.5-10
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• 1985

The effect of calcium lignosulfonate (CLS) on the early hydration characteristics for clinker minerals was investigated. In the presence of CLS and unsufficient gypsum The hydration of $C_3$A lowered CLS adsorption to form ettrin-gite and the residual CLS in the liquid phase accelerated the solubility of C4AF hydration. As the result unreacted $Fe^{3+}$ in the liquid phase would be precipitated gelatinously on $C_3$ hydrates and the hydration of $C_3$ could be retarded. But by addition of optimum gypsum into the cement with CLS the presence of $Fe^{3+}$ in the liquid phase were lowered and $C_3$ hydration would be normallized.

• 대한치과기공학회지
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• 제41권2호
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• pp.149-156
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• 2019

Purpose: Prosthodontics for edentulous patients is a treatment technique using implant, which has impactful results in retention and support effects. Methods: As a retention technique, SCRP (screw and cement retained implant prosthesis) has reported in many studies as a beneficial method for both patients and curers, which can reduce errors in process of making abutment and top implant. Results: Prosthesis manufacturing, as polymerization method of hardened resin teeth with thermoplastic resin, is helpful for patients with aesthetic and financial situations regarding residual ridge and interocclusal relationship, also indicates reliable results in both retention and care. Conclusion: Using SCRP technique, we notably obtained a clinical and aesthetic outcome from five implants in anterior tooth, which are half fixable and detachable implants on screw of implant abutment by the technicians at anytime.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2023년도 봄 학술논문 발표대회
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• pp.315-316
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• 2023

In the present investigation, the chloride ion penetration resistance of nuclear power plant concrete with varying water-to-cement ratios was assessed. A comparative analysis was conducted on concretes that do not incorporate supplementary cementitious materials, such as fly ash, using permanently decommissioned nuclear structures as a reference. The objective is to employ this acquired data as a fundamental resource for the evaluation of the residual service life of nuclear power plant structures in subsequent studies.

• Steel and Composite Structures
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• 재36권6호
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• pp.657-669
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• 2020

This study investigates the fire resistance characteristics of reactive powder concrete according to changes in the cement content per unit area, mixing ratio of metakaolin (MK), and content of polypropylene fiber. A fire test was conducted, and the resulting residual strength characteristics were investigated through flexural and compressive strength measurements, as well as condition rating classification based on visual evaluation. MK effectively reduced the initial high content of calcium hydroxide, thereby reducing the water vapor pressure generated during pyrolysis and slowing spalling. Furthermore, the pore structure and loose tissue were effective for relieving the water vapor pressure in the event of a fire.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 세계 도시지반공학 심포지엄
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• pp.1378-1382
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• 2009

This study is conducted to investigate the possibility of the utilization of the mixed soil formed by mixing stone sludge, bentonite, and residual soil as a soil sealant sustaining both stability and capacity in the barrier system. And the mixed soil formed by mixing stone sludge, river sand is conducted to investigate the possibility of recycle. A series of tests were performed on the mixed soil(stone sludge, bentonite, Cement and residual soil) to evaluate basic properties such as compaction, compressive strength, permeability of these materials. and the stone sludge-river sand mixed soil were performed the discharge capacity tests.