• 대한치과교정학회지
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• 제37권4호
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• pp.283-292
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• 2007

새로운 접착 시스템의 개발로 브라켓의 접착 과정이 단순화되고 있는 추세이다. 본 연구에서는 통상적인 산 부식 방법과 더불어 수종의 교정용 및 수복용 self etching primer를 이용하여 브라켓을 접착한 후 전단결합강도를 측정하고 접착 파절 양상을 비교함으로써 self etching primer 유용성을 평가하였다. 교정 치료를 위해 발거한 상, 하악 소구치 75개를 레진 블록에 매몰하여 시편을 제작하였고, 산 부식이 필요한 Transbond XT primer와, 4종의 self etching primer (Transbond Plus Self Etching Primer, Unifill Bond, Clearfil SE bond, Adhese)를 각각 이용하여 브라켓을 접착한 후, 만능시험기로 전단결합강도를 측정하고, 브라켓 기저면을 광학현미경으로 관찰하여 접착 파절 양상을 관찰하였다. 접착제 잔류지수를 비교한 결과, 통계적으로 유의한 차이는 없었으나, 인산 처리군이 self etching primer 처리군에서 보다 낮은 값을 보여, self etching primer 처리군이 인산 처리군 보다 법랑질-레진 접착계면 부위에서의 파절이 많이 일어나는 경향이 있었음을 알 수 있었다. Self etching primer 처리군에서의 전단결합강도는 37% 인산 처리군의 전단결합강도보다 낮았지만(p < 0.05), 임상적으로 유용한 수준 이상이었으며, self etching primer 처리군 내에서 각각의 전단결합강도는 유의한 차이를 보이지 않았다 (p > 0.05). 따라서 self etching primer를 이용할 경우, 기존의 산 부식법에 비하여 다소 낮은 전단결합강도를 보이지만 임상적으로 충분히 사용 가능하다고 생각된다.

• 대한치과보철학회지
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• 제17권1호
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• pp.23-34
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• 1979

In this study, the adhesive strength of three commercial polycarboxylate cements to ten types of dental casting alloys, such as gold, palladium, silver, indium, copper, nickel, chromium, and human enamel and dentine were measured and compared with that of a conventional zinc phosphate cement. The $8.0mm{\times}3.0mm$ cylindrical alloy specimens were made by casting. The enamel specimens were prepared from the labial surface of human upper incisor, and the dentine specimens were prepared from the occulusal surface of the human molar respectively. Sound extracted human teeth, which had been kept in a fresh condition since, extraction, were mounted in a wax box with a cold-curing acrylic resin to expose the flattened area. The mounted teeth were then placed in a Specimen Cutter (Technicut) and were cut down under a water spray, and then the flat area on the all specimens were ground by hand with 400 and 600 grit wet silicone carbide paper. Two such specimens were then cemented together face-to-face with freshly mixed cement, and moderate finger pressure was applied to squeeze the cement to a thin and uniform film. All cemented specimens were then kept in a thermostatic humidor cabinet regulated at $23{\pm}2^{\circ}C.$ and more than 95 per cent relative humidity and tested after 24 hours and 1 week. Link chain was attached to each alloy specimen to reduce the rigidity of the jig assembly, and then all the specimens were mounted in the grips of the Instron Universal Testing Machine, and a tensile load was delivered to the adhering surface at a cross head speed of 0.20 mm/min. The loads to which the specimens were subjected were recorded on a chart moving at 0.50 mm/min. The adhesive strength was determined by measuring the load when the specimen separated from the cement block and by dividing the load by the area. The test was performed in a room at $23{\pm}2^{\circ}C.$ and $50{\pm}10$ per cent relative humidity. A minimum of five specimens were tested each material and those which deviated more than 15 per cent from the mean were discarded and new specimens prepared. From the experiments, the following results were obtained. 1) It was found that the adhesive strength of the polycarboxylate cement to all alloys tested was considerably greater than that of the zinc phosphate cement. 2) The adhesive strength of the polycarboxylate cements was superior to the non precious alloys, such as the copper, indium, nickel and chromium alloys, but it was inferior to the precious gold, silver and palladium alloys. 3) Surface treatment of the alloy was found to be an important factor in achieving adhesion. It appears that a polycarboxylate cement will adhere better to a smooth surface than to a rough one. This contrasts with zinc phosphate cements, where a rough helps mechanical interlocking. 4) The adhesion of the polycarboxylate cement with enamel was found superior to its adhesion with dentine.

• 한국방사선학회논문지
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• 제7권3호
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• pp.175-179
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• 2013

파노라마와 CBCT 같은 회전하는 방사선 발생장치에서 방사선작업종사자와 보호자의 적절한 피폭 방어 대책을 알아보고자 위치에 따른 방사선 조사선량을 비교 분석하였다. 사용된 장치로는 파노라마 DP-90-P PAX-500(Vatech, Korea)와 CBCT DCT-90-P IMPLAGRAPHY Dental CT system (Vatech, Korea)을 사용하였다. 조사선량 측정기는 Ion chamber model 2026과 Reader기 20X5-60E를 사용하였다. 촬영조건은 임상에서 사용하는 인자와 동일하게 설정하였다. 실험결과 파노라마는 검사가 처음 시작하는 A지점이 81${\mu}R$ 으로 가장 높게 나왔고, 검사가 끝나는 D점이 53${\mu}R$ 으로 가장 낮게 나왔다. CBCT의 경우는 검사가 끝나는 D지점이 1,021${\mu}R$ 으로 가장 높게 나왔고, 검사가 시작하는 A지점이 809.67${\mu}R$ 으로 가장 높게 측정되었다. 부득이하게 보호자나 방사선작업종사자가 환자를 잡고 검사해야 할 경우에는 피폭선량이 가장 많은 지점을 피해서 X선관이 회전하기 시작하는 지점과 끝나는 지점의 가운데 위치해야 할 것이다. 그리고 장비의 특성상 기계의 반대편이며, 환자의 측면에서 지지하는 것보다 후방에서 지지하는 것이 가장 안전할 것이고, 적절한 방호기구를 착용해야 할 것이다.

• 전기학회논문지
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• 제67권5호
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• pp.635-643
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• 2018

This paper propose a method to identify the motor parameters and improve input voltage error which affect the low speed position error of the back-emf(back electromotive force) based sensorless algorithm and to secure the operation reliability and stability even in the case where the load fluctuation is severe and the start and low speed operation frequently occurs. In the model-based observer used in this paper, stator resistance, inductance, and input voltage are particularly influential factors on low speed performance. Stator resistance can cause resistance value fluctuation which may occur in mass production process, and fluctuation of resistance value due to heat generated during operation. The inductance is influenced by the fluctuation due to the manufacturing dispersion and at a low speed where the change of the current is severe. In order to find stator resistance and inductance which have different initial values and fluctuate during operation and have a large influence on sensorless performance at low speed, they are commonly measured through 2-point calculation method by 2-step align current injection. The effect of voltage error is minimized by offsetting the voltage error. In addition, when the command voltage is used, it is difficult to estimate the back-emf due to the relatively large distortion voltage due to the dead time and the voltage drop of the power device. In this paper, we propose a simple circuit and method to detect the voltage by measuring the PWM(Pulse Width Modulation) pulse width and compensate the voltage drop of the power device with the table, thereby minimizing the position error due to the exact estimation of the back-emf at low speed. The suitability of the proposed algorithm is verified through experiment.

• 한국산학기술학회논문지
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• 제13권6호
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• pp.2458-2464
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• 2012

최근 디스플레이용 부품소재는 국가 산업 경쟁력을 강화시킬 수 있는 고부가가치 산업분야로 발전하고 있다. 하지만 디스플레이용 부품소재 생산을 위한 시스템은 대부분 수입에 의존하며 개발이 미비한 상태이다. 그러므로 디스플레이용 부품소재인 스페이서 테이프 생산을 위한 엠보싱 처리 시스템의 국산화 및 생산성 증대를 위한 시스템 향상이 시급한 실정이다. 따라서 본 논문에서는 엠보싱처리 시스템의 국산화 및 생산성 증대를 위한 스페이서 테이프 생산을 위한 회전형 엠보싱 처리 시스템을 제안한다. 시스템은 권출부, 성형부, 권치부, 세정부, 검사부로 구성된다. 이 중, 성형부의 금형을 회전형 방식으로 설계하였고, 각 구성품들을 설계하고 시제작품을 제작하여 성능 실험을 하였다. 성능 실험은 삼차원 측정기를 통해 엠보싱 형상, 직경, 엠보싱 간격 및 반대편 엠보싱과의 거리를 측정하였다. 오염물 검출 실험을 하기 위해, 검사부를 통해 첫 번째 샘플과 반복 생산한 후의 샘플에 대해 이물질 레벨을 측정하였다. 그리고 샘플에 이물질을 부착한 후 세정부를 통해 샘플을 세정한 후의 이물질 개수를 측정하여 오염물 세정 실험을 하였다. 또한, 시제작품에 의해 생산되는 스페이서 테이프의 생산성을 측정하였다.

• Journal of the Korean Wood Science and Technology
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• 제7권1호
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• pp.8-11
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• 1979

못의 보지력(保持力)인 정적인발저항(靜的引拔抵抗)에 관(關)하여 Pinus Koraiensis Sieb. et. Zucc. 재(材)와 Larix leptolepis Gord.재(材)의 두 수종(樹種)에 대하여 못 박은 후(後) 시간별(時間別) 차이(差異), 재(材)의 함수율별(含水率別) 및 Radial, Tangential, Longitudinal, 등(等)의 재(材)의 방향별(方向別)에 대해 실험(實驗)한 결과(結果)를 요약(要約)하면 다음과 같다. 1) 못을 박은 후(后) 인발저항(引拔抵抗)은 Larix leptolepis Gord. 재(材)에서는 Tangential이 최대(最大)였다.(Fig 3.) Pinus koraiensis Sieb. et. Zucc. 재(材)는 Tangential이나 Radial의 인발저항(引拔抵抗)은 차이(差異)가 없다.(Fig 2) 2) Longitudinal의 인발저항(引拔抵抗)은 두 수종(樹種) 모두 최소(最小)이다. (Fig 2, 3.) 3) 일정(一定)한 시간후(時間后)에는 Radial 및 Tangential는 두 수종(樹種)이 모두 감소(減少)한다. 4) 재(材)의 함수율(含水率)이 증가함에 따라 두 수종(樹種)이 인발저항(引拔抵抗)은 직선적(直線的)으로 감소(減少)한다. (Fig 4, 5) 5. Larix leptoleis Gord. 재(材)의 인발저항(引拔抵抗)의 감소상태(減少狀態)은 섬유포화점(纖維飽和点) 부근(附近)에서 변곡점으로 나타났다. (Fig 5)

• 대한치과보철학회지
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• 제38권2호
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• pp.226-241
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• 2000

Recently a new generation of crown and bridge veneering resins containing submicron glass fillers was introduced. These ultrasmall particle hybrid composite materials distinguish themselves, compared with conventional microfill crown and bridge resins, through improved mechanical properties. It is claimed that these composites are suitable for metal free crowns and even bridges using fiber reinforcement. The purpose of this study was to evaluate the effect of thermal cycling on the tensile strength of the following veneering composites: Artglass(Heraeus Kulzer Co., Wehrheim, Germany), Estonia(Kuraray Co.. Japan), Sculpture(Jeneric Pentron Co., Wallingford, U.S.A.), and Targis(Ivoclar Co., Schaan Liechenstein). According to manufacturer's instructions, rectangular tensile test specimens measuring $1.5{\times}2.0{\times}4.5mm$ were made using a teflon mold. Whole specimens were divided into two groups. One group was dried in a desiccator at $25^{\circ}C$ for 10 days, and another group was subjected to thermal cycling($10,000{\times}$) in water($5/55^{\circ}C$). All test specimens were placed in a universal testing machine and loaded until fracture with a crosshead speed of 0.5mm/min. Weibull analysis and Tukey's test were used to analyze the data. The fracture surfaces of specimens were observed in SEM and the aliphatic C=C absorbance peak of Estenia and Targis resin was analyzed using Fourier transform infrared(FTIR) spectroscopy. Within the limitations imposed in this study, the following conclusions can be drawn: 1. Both in drying condition and thermal cycling condition, the highest tensile strength was observed in Estenia testing group(p<0.05). 2. The strength data were at to single-mode Weibull distribution, and the Weibull modulus of all veneering composite resin specimens increased after thermal cycling treatment. 3. After thermal cycling test, the highest tensile strength was observed in the Estenia group, and the lowest value was observed in the Targis group. The tensile strength values showed the significant differences between each group(p<0.05) 4. The aliphatic C=C absorbance peak of Estonia and Targis resin was decreased after light curing, and there was no distinct change after thermal cycling.

• 대한치과보철학회지
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• 제42권3호
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• pp.280-293
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• 2004

Statement of problem. Glass fiber post is one of recent developments to accommodate esthetic restoration for endodontically treated teeth. This has many advantages over conventional post system in physical properties, esthetic factor, risk of root and restoration fracture, adhesion to core, radiopacity, removal and retrievabilty, biocompatibility and chemical stability. Purpose. This in vitro study was to evaluate the most suitable type of resin core for the glass fiber post through surveying the fracture modes and the maximum load that fractures the tooth. Material and methods. 50 sound maxillary premolars restored with glass fiber posts($ParaPost^{(R)}$ Fiber White) and different types of resin cores(ParaCore, $Z100^{TM}$, $Rebilda^{(R)}$ and $Admira^{(R)}$) were prepared and loaded to faiure in a universal test machine. The maximum fracture load and fracture mode were investigated in the specimens that were restored with resin and those of metal cast and core. With the data, Wilcoxon rank sum test was used to validate the significance between the test groups, and Tukey' s studentized range test was used to check if there is any significant statistical difference between each test group. Every analysis was approved with 95% reliance. Results. On measuring the maximum fracture load of teeth specimens, there was a significant difference between the maximum fracture loads of the tooth specimens. ParaCore showed the highest mean maximum fracture load followed by $Z100^{TM}$. And, the distribution of fracture mode of tooth specimens showed generally Type D, the three parted fracture of the core around the post was mostly seen(62.5%), and specifically, ParaCore showed 90% and $Z100^{TM}$ showed 100% Type D fracture. Conclusion. Referring to the values of maximum fracture load and mean compressive fracture load, ParaCore and $Z100^{TM}$ had high values and are recommended as tooth colored resin core material for glass fiber post. CLINICAL IMPLICATIONS. This study was carried out intending to be of aid in selecting the appropriate resin core for the glass fiber post. The dual cure type composite resin ParaCore and light cure type composite resin $Z100^{TM}$ have good properties and are recommended as tooth colored resin core material for glass fiber post.

• 한국치위생학회지
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• 제12권3호
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• pp.611-620
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• 2012

Objectives : This study evaluated the changes in surface roughness of denture base resin according to the types of denture cleansers. Methods : A denture base resin(Vertex RS, Dentimax, Netherland) was used. Two toothpaste(Antiplaque, Bukwang, Korea; 2080, Aekyung, Korea) and a kitchen detergent(Trio, Aekyung, Korea) were used as a denture cleanser. The specimens were put on the V8 crossbrushing machine(Sabri enterprises, Downers grove, IL, USA) to reproduce toothbrushing and the toothbrushes were flat, round end and soft type. The surfaces of denture base resin specimens were observed by profilometer(SJ-400, MITUTOYO, Japan) and SEM(S-3000N, Hitachi Co., Ibaraki, Japan). Results : 1. According to the result of measuring surface roughness, there was statistically significant difference in Ra, Rq, and Rz(p<0.05). 2. As for Ra, Rq and Rz, Antiplaque toothpaste showed the highest roughness, and there was significant difference from other groups(p<0.01). 2080 toothpaste, Trio, and distilled water were classified as the same group. 3. According to the result of observation with the SEM, the surfaces of the Antiplaque toothpaste group after toothbrushing showed the greatest roughness, and the surfaces of 2080 toothpaste, Trio, and distilled water groups were rough in order. Trio and distilled water had the surfaces similar to those before toothbrushing. Conclusions : Studies to compare the efficacy of denture management methods and examine the effects of denture cleansers on denture materials will be helpful for dental hygienists and dentists providing patients with proper information and education. And it will be also useful for denture users' oral health.

• 대한치과보철학회지
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• 제42권6호
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• pp.664-670
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• 2004

Statement of problem. One of the common problems of dental implant prosthesis is the loosening of the screw that connects each component, and this problem is more common in single implant-supported prostheses with external connection. Purpose. The purpose of this study was to examine the changes of detorque values of abutment screws with external connection in different abutment heights. Materials and methods. After cyclic loading on three different abutment heights, detorque values were measured. Abutments were retained with titanium abutment screws tightened to 30 Ncm (30.5 kgmm) with digital torque gauge as recommended by the manufacturer. Replacing abutments, implants and titanium abutment screws with new ones at every measurement, initial detorque values were measured six times. In measuring de torque values after cyclic loading, Avana Cemented Abutments of 4.0 mm collar, 7.0 mm height (Osstem Co., Ltd., Seoul, Korea) were used with three different lengths of 5.0, 8.0, 11.0 mm. Shorter abutments were made by milling of 11.0 mm abutment to have the same force-exercised area of 4.5 mm diameter. Sine curve force (20N-320N, 14Hz) was applied, and detorque values were measured after cyclic loading of 2 million times by loading machine. Detorque values of initial and after-loading were measured by digital torque gauge. One-way ANOVA was employed to see if there was any influence from different abutment heights. Results. The results were as follows: 1. The initial detorque value was 27.8$\pm$0.93 kgmm, and the ratio of the initial detorque value to the tightening torque was 0.91(27.8/30.5). 2. Measured detorque values after cyclic loading were declined as the height of the abutment increased, that was, 5.0 mm; 22.3$\pm$0.82 kgmm, 8.0 mm; 21.8$\pm$0.93 kgmm, and 11.0 mm; 21.3$\pm$0.94 kgmm. 3. One-way ANOVA showed no statistically significant differences among these (p>0.05). 4. Noticeable mobility at the implant-abutment interface was not observed in any case after cyclic loading at all.