• 한국환경보건학회지
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• 제28권2호
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• pp.109-116
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• 2002

The purpose of this study was to evaluate a new sampling and analytical method for the determination of airborne hexavalent chromium, Cr(Ⅵ), in a field plating operation. The procedures of this new method (Shin & Paik's Method) are as the following: Airborne hexavalent chromium is collected on polyvinyl chloride (PVC) filter according to the National Institute iota Occupational Safety and Health (NIOSH) Method 7600, and the filler sample is placed in a screw-capped vial and soaked with 2% NaOH/3% Na₂CO₃ solution immediately after sampling. The Cr(Ⅵ) sample is analyzed by ion chromatography/visible spectrophotometry (IC/VS) according to the U.S. Environmental Protection Agency (EPA) Method 218.6. The airborne Cr(Ⅵ) concentrations measured by this method were compared with those determined by three reference methods: One (NIOSH/EPA Method) consisted of sampling airborne Cr(Ⅵ) on PVC filters and storing the sample filters in strew-capped vials according to the NIOSH method, and analyzing Cr(Ⅵ) in samples using IC/VS according to the EPA method. The second method (Impinger Method/NaHCO₃) consisted of absorbing airborne Cr(Ⅵ) into 0.02 M NaHCO₃ solution in midget impinger, and analyzing the Cr(Ⅵ) in samples using IC/VS. The third method was the OSHA Method ID-215. Using these four different methods, lour replicates of air samples were collected at an electroplating process and analyzed simultaneously. Two-way ANOVA and paired t-test were used to test difference among values determined by the methods. There was no significant difference and a strong correlation (r²:0.99) between Cr(Ⅵ) concentrations measured by the Shin & Paik's Method and an impinger method (p>0.05). However, Cr(Ⅵ) concentrations determined by Shin & Paik's Method were significant1y different from those by the NIOSH/EPA Method (p<0.05) or the OSHA method (p<0.05). The Cr(Ⅵ) concentrations of Shin & Paik's Method were significantly higher than those of the NIOSH/EPA Method or the OSHA method. This result indicated that the Shin & Paik's Method may prevent Cr(Ⅵ) losses caused by reduction and give more reliable results of airborne Cr(Ⅵ) concentrations in work environments.

• Composites Research
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• 제23권6호
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• pp.55-60
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• 2010

본 연구에서는 열가소성 복합재료인 유리섬유/폴리프로필렌 복합재료를 이용한 복합재료 고정판의 적절한 성형조건을 찾기 위해 다양한 성형조건으로 제작된 시편의 인장실험과 굽힘실험을 수행하여 성형조건에 따른 기계적 거동을 비교하였다. 실험 결과 성형온도와 압력이 각각 $230^{\circ}C$, 3MPa일 때 가장 우수한 기계적 특성을 가짐을 확인하였다. 성형실험을 통해 결정된 성형조건을 이용한 복합재료 고정판의 성형방법으로는 고정판의 스크류 구멍을 한번에 성형하는 정형성형방법과 스크류 구멍을 후가공하는 방법을 사용하였으며, 성형실험과 굽힘실험 결과 스크류 구멍을 후가공 하는 경우 우수한 굽힘특성을 가지는 것을 확인하였다. 본 논문에서는 복합재료 고정판의 적절한 성형을 위해 유리섬유/폴리프로필렌 복합재료의 기초 성형정보와 그에 따른 고정판 성형에 대한 연구를 수행하였으며, 이 결과는 해당재료를 이용한 구조물 성형에 중요한 정보를 제공할 것으로 기대된다.

• Clinics in Shoulder and Elbow
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• 제24권3호
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• pp.125-134
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• 2021

Background: To evaluate clinical and radiological outcomes of bony increased offset-reverse total shoulder arthroplasty (BIO-RSA) in the Asian population at mid-term follow-up. Methods: From June 2012 to August 2017 at a single center, 43 patients underwent BIO-RSA, and 38 patients with minimum 2 years follow-up were enrolled. We evaluated the clinical and radiological outcomes, and complications at the last follow-up. In addition, we divided these patients into notching and no-notching groups and compared the demographics, preoperative, and postoperative characteristics of patients. Results: Visual analogue scale, American Shoulder and Elbow Surgeons, University of California-Los Angeles Shoulder Scale, and Simple Shoulder Test scores improved significantly from preoperative (5.00, 3.93, 1.72, 3.94) to postoperative (1.72, 78.91, 28.34, 7.66) (p<0.05) outcomes. All range of motion except internal rotation improved significantly at the final follow-up (p<0.05), and the bone graft was well-incorporated with the native glenoid in all patients (100%). However, scapular notching was observed in 20 of 38 patients (53%). In the comparison between notching and no-notching groups (18 vs. 20 patients), there were no significant differences in demographics, radiological parameters, and clinical outcomes except acromion-greater tuberosity (AT) distance (p=0.003). Intraoperative complications included three metaphyseal fractures and one inferior screw malposition. Postoperative complications included ectopic ossification, scapular neck stress fracture, humeral stem relaxation, and late infection in one case each. Conclusions: BIO-RSA showed improved clinical outcomes at mid-term follow-up in Asian population. However, we observed higher scapular notching compared to the previous studies. In addition, adequate glenoid lateralization with appropriate humeral lengthening (AT distance) might reduce scapular notching.

• 핵의학기술
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• 제19권1호
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• pp.51-56
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• 2015

Purpose As medical radiation exposures on patients are being social issues an interest in a relief of radiation exposures on patients is increasing. Further, there are many cases where some patients among who are getting PET/CT tests choose to get implanted with metal artifacts in their bodies. This study is to find out effects of presence or absence of metal artifacts when dose change or CT attenuation correction for the relief of radiation exposures are applied using phantoms through changes in standard uptake value (SUV). Materials and Methods GE company's Discovery 710 machine was used for PET/CT test equipments. We used NEMA IEC body phantoms. We also used screw and mesh cage made of titanium which are used in real clinical processes for the metal artifacts. Two experiments were conducted: One is to test and measure repeatedly about SUV about differences in CT attenuation corrections according to dose changes and another is to do the same procedure for SUV about the presence and absence of the metal artifacts. We injected $^{18}F-FDG$ into NEMA IEC body phantoms with a TBR ratio of 4:1 and then put the metal material into the transformation phantoms. Once a scanning for the metal artifacts was done we eliminated the metal artifacts and went on non-metal artifacts. For the each two experiments, we scanned repeatedly with CT kVp (140, 120, 100, 80) and mA (120, 80, 40, 20, 10) for an experimental condition. For PET, we reconstructed each with standard AC (STD) technique and quantitation achieved cnsistently QAC) technique among CT attenuation correction methods. We conducted a comparative analysis on measured average values and variations which were measured through repeated measure of SUV of region 1, 2, 3 spheres for each conditions of non-metal /metal scan. Results For each kVp, 120, 80, 40 (mA) of non/metal (screw, mesh cage) showed low frequency of fluctuation rates of above 2%. In 20, 10 mA above 2% of fluctuation rates appeared in high frequency. Also, when we compared the fluctuation rates of STD and QAC techniques in non/metal (screw, mesh cage) tests QAC technique showed about 1-10% of differences for each conditions compared to STD technique. In addition, metal types did not have significant effects on fluctuation rates. Conclusion We confirmed that SUV fluctuation rates for both STD and QAC techniques increase as dosage is lower. We also found that the SUV of PET data was maintained steadily in a low dosage for QAC technique when compared with STD technique. Hence, when the low dosage is used for the relief of radiation exposures on patients QAC technique may be exploited helpfully and this could be applied in the same way for patients with metal artifacts implanted in their bodies.

• 대한치과보철학회지
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• 제44권5호
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• pp.594-605
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• 2006

Statement of problem: Modification of titanium implant surface has potential to ensure clinically favorable performance that several surface modification technologies have been introduced. Among the methods. anodizing method and sol-gel hydroxyapatite coating method have gained much interest due to its roughness and chemical composition of the coating layer, but more of its biocompatibility result is required. Purpose : The purpose of this study was to compare bone-implant interface shear strength of four different surface treated implants as time elapsed. Resonance frequency analysis(RFA) and removal torque measurement methods were employed to measure implant stability at one week and six week after implantation. Material and method: A total of 80 screw-shaped implant [20 machined, 20 resorbable media blasted(RBM), 20 anodized, and 20 anodized+hydroxyapatite sol-gel coated] were prepared, and one of each group was implanted in the tibia of a New Zealand white rabbit that total 20 of them were used. In order to test the implant stability and implant-tissue interface contact changing in the bone bed, each 10 rabbit were sacrificed 1 week and 6 week later while resonance frequency and removal torque were measured. One-way analysis of variance and the Tukey test were used for statistical analysis. Results : The results were as follows. 1. There was no statistically significant difference of implant stability quotients(ISQ) value in RFA between individual groups after 1 week of implantation and 6 weeks(p>0.05). But, there was statistically significant increase of ISQ value in 6 weeks group compared to 1 week group(p<0.05). 2. There was no statistically significant difference in removal torque analysis between individual groups after 1 week of implantation and 6 weeks(p>0.05). but there was statistically significant increase in all 4 groups after 6 weeks compared to 1 week later(p<0.05). 3. There was no statistically significant difference in removal torque analysis between anodized group and HA coating after anodic oxidation 6 weeks later(p>0.05), but significant difference was appeared in both groups compared to RBM group and smooth-machined group(p<0.05). Conclusions : It can be suggested that changes in surface characteristics affect bone reactions. Anodized and anodized+hydroxyapatite sol-gel coating showed significantly improved bone tissue response to implants, but further study on the effect of hydroxyapatite dissolution is needed.

• 대한치과보철학회지
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• 제43권3호
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• pp.352-362
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• 2005

Statement of problem. Accurate impression is essential to success of implant prostheses. But there have been few studies about the accuracy of fixture-level impression techniques in internal connection implant systems. Purpose. The purpose of this study was to compare the accuracy of two fixture-level impression techniques in two conditions (parallel and divergent) and to assess the effect of tightening sequences and forces on stresses generated on superstructures in internal connection implant system (Astra Tech). Material and methods. Two metal master frameworks made from two abutments (Cast-to Abutment ST) each and a corresponding, passively fitting, dental stone master cast with four fixture replicas (Fixture Replica ST) were fabricated. Ten dental stone casts for each impression techniques (direct unsplinted & splinted technique) were made with vinyl polysiloxane impressions from the master cast. Strain gauges for each framework were fixed midway between abutments to measure the degree of framework deformation on each stone cast. Pairs of strain gauges placed opposite each other constituted one channel (half Wheatstone bridge) to read deformation in four directions (superior, inferior, anterior, and posterior). Deformation data were analyzed using one-way ANOVA and the Tukey test at the .01 level of significance. And the effect of tightening sequences (right-to-left and left-to-right) and forces (10 Ncm and 20 Ncm) were assessed with ten stone casts made from parallel condition by the splinted technique. Deformation data were analyzed using paired t-test at the .01 level of significance. Conclusions. Within the limitations of this study, the following conclusions could be drawn. 1. Frameworks bent toward the inferior side on all casts made by both direct unsplinted and splinted impression techniques in both parallel and divergent conditions. 2. There was no statistically significant difference of accuracy between the direct unsplinted and splinted impression techniques in both parallel and divergent conditions (P>.01). 3. There was no statistically significant difference of stress according to screw tightening sequences in casts made by the splinted impression technique in parallel condition (P>.01). 4. Greater tightening force resulted in greater stress in casts made by the splinted impression technique in parallel condition (P<.01).

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
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• pp.2090-2100
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• 2011

Railway rail fastening system is the critical device which gives big influences to not only the vehicle driving stability and the orbit's structural stability against the impulsive load, but also the noise vibration and the ride comfort. As a part of the low-carbon green growth, the importance of the railroad industry is getting highlights on its excellent energy-efficiency and eco-friendliness. However, so far the Korea's domestic rail fastening system technology is not so good and the technical reliance to abroad is very heavy. In this study, we conducted comparative analysis on the rail fastening system with new and used one of the same type. And those systems are imported by Seoul Metro and are being used by it. With this basis, we developed the components and the materials and then, established the durability assessment methods appropriate to the Korean domestic circumstances. And through the reliability qualification test on the 7 parts of the rail fastening system, we've improved the reliability and guaranteed the 15 years of service lifetime. ($B_{10}Life15$) Establishment and standardization of Reliability Standard on the parts of the rail fastening system such as anti-vibration pads, guide-plate, screw spike made it possible to perform the internationally fair assessment. And it is thought that we can satisfy the manufactures' and consumers' needs of cost-cutting and qualification security by shortening of assessment period on rail fastening system.

• The Journal of Advanced Prosthodontics
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• 제12권3호
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• pp.167-172
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• 2020

PURPOSE. The aim of the present study was to investigate the passive fit of metal substructure after repetitive firing processes in implant-supposed prosthesis. MATERIALS AND METHODS. Five implants (4 mm diameter and 10 mm length) were placed into the resin-based mandibular model and 1-piece of screw-retained metal substructure was produced with the direct metal laser sintering (DMSL) method using Co-Cr compound (n = 10). The distance between the marked points on the multiunit supports and the marginal end of the substructure was measured using a scanning electron microscope (SEM) at each stage (metal, opaque, dentin, and glaze). 15 measurements were taken from each prosthesis, and 150 measurements from 10 samples were obtained. In total, 600 measurements were carried out at 4 stages. One-way ANOVA test was used for statistical evaluation of the data. RESULTS. When the obtained marginal range values were examined, differences between groups were found to be statistically significant (P<.001). The lowest values were found in the metal stage (172.4 ± 76.5 ㎛) and the highest values (238.03 ± 118.92 ㎛) were determined after glaze application. When the interval values for groups are compared with pairs, the differences between metal with dentin, metal with glaze, opaque with dentin, opaque with glaze, and dentin with glaze were found to be significant (P<.05), whereas the difference between opaque with metal was found to be insignificant (P=.992). CONCLUSION. Passive fit of 1-piece designed implant-retained fixed prosthesis that is supported by multiple implants is negatively affected by repetitive firing processes.

• Journal of Periodontal and Implant Science
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• 제50권2호
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• pp.97-105
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• 2020

Purpose: The present retrospective clinical study aimed to evaluate and compare the clinical and radiographic parameters, complications, and satisfaction in patients who received fixed prostheses supported by narrow-diameter implants (NDIs) in the anterior and posterior jaw. Methods: Patients aged ≥30 years who had NDI-supported fixed prostheses in the anterior or posterior region of either jaw for at least 2 years were included. Complications such as chipping of the crown; loosening or fracture of the screw, crown abutment, or implant; and loss of retention were recorded. Clinical peri-implant outcomes and crestal bone loss (CBL) were measured. A questionnaire was used to record responses regarding the aesthetics and function of the fixed restorations. Analysis of variance was used to assess the significance of between-group mean comparisons. The log-rank test was performed to analyze the influence of location and prosthesis type on technical complications. Results: Seventy-one patients (mean age: 39.6 years) provided informed consent with a mean follow-up duration of 53 months. Only bleeding on probing showed a statistically significant difference between NDIs in the anterior and posterior regions. The complication rate for NDIs in the posterior region was significantly higher than that for NDIs in the anterior region (P=0.041). For NDIs, CBL was significantly higher around splinted crowns than single crowns (P=0.022). Overall mean patient satisfaction was 10.34±3.65 on a visual analogue scale. Conclusions: NDIs in the anterior and posterior jaws functioned equally well in terms of periimplant soft and hard tissue health and offered acceptable patient satisfaction and reasonable complication rates.

• The Journal of Advanced Prosthodontics
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• 제6권6호
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• pp.491-497
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• 2014

PURPOSE. This study evaluated the influence of abutment materials on the stability of the implant-abutment joint in internal conical connection type implant systems. MATERIALS AND METHODS. Internal conical connection type implants, cement-retained abutments, and tungsten carbide-coated abutment screws were used. The abutments were fabricated with commercially pure grade 3 titanium (group T3), commercially pure grade 4 titanium (group T4), or Ti-6Al-4V (group TA) (n=5, each). In order to assess the amount of settlement after abutment fixation, a 30-Ncm tightening torque was applied, then the change in length before and after tightening the abutment screw was measured, and the preload exerted was recorded. The compressive bending strength was measured under the ISO14801 conditions. In order to determine whether there were significant changes in settlement, preload, and compressive bending strength before and after abutment fixation depending on abutment materials, one-way ANOVA and Tukey's HSD post-hoc test was performed. RESULTS. Group TA exhibited the smallest mean change in the combined length of the implant and abutment before and after fixation, and no difference was observed between groups T3 and T4 (P>.05). Group TA exhibited the highest preload and compressive bending strength values, followed by T4, then T3 (P<.001). CONCLUSION. The abutment material can influence the stability of the interface in internal conical connection type implant systems. The strength of the abutment material was inversely correlated with settlement, and positively correlated with compressive bending strength. Preload was inversely proportional to the frictional coefficient of the abutment material.