• The Journal of Korean Academy of Prosthodontics
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• v.55 no.1
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• pp.61-70
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• 2017

In this case, the impression surface of the existing denture was scanned and was inverted three-dimensionally to express the residual ridge form. Implant planning was performed on the superimposed data of the CT with the scanned image of the denture with radiopaque markers attached. At the day of surgery, customized abutments fabricated in accordance with the form of the gingival margin were linked with fixtures and temporary restorations were set. In the process of fabricating the final prosthesis after the osseointegration of implant fixture, the intraoral scan images at abutment level were merged with images of the abutments scanned and stored before implant surgery. By fabricating the final prosthesis with the abutments obtained by merging can increase the marginal fitness of the final prosthesis and simplify the clinical process.

• Journal of Dental Rehabilitation and Applied Science
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• v.25 no.1
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• pp.41-52
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• 2009

The surface treatment of titanium implant could bring out the biochemical bonding between bone and implant. The purpose of this study was to evaluate the biomechanical bone response of Mg-ion implanted implants with plasma source ion implantation method. Twelve New Zealand white rabbits were included in this study. Each rabbit received one control fixture (blasted with resorbable blasting media, RBM) and three types of Mg ion implanted fixtures in tibiae. The implants were left in place for 6 weeks before the rabbits were sacrificed. Removal torque value and resonance frequency analysis (ISQ) were compared. The repeated measured analysis of variance was used with $P{\leq}0.05$ as level of statistical significance. ISQ was not different among all groups. However, the ISQ was increased after 6 weeks healing. The group had lowest ISQ value showed the greatest increment. Mg-1 implants with 9.4% retained ion dose showed significantly higher removal torque value than that of the other implants. From this results, it is concluded that the Mg-1 implants has stronger bone response than control RBM surface implant.

• Journal of Dental Rehabilitation and Applied Science
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• v.26 no.2
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• pp.205-220
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• 2010

Purpose : To analyze the effect of implant designs on insertion torque and stress by performing a comparative study on von Mises stress, torque and normal force through a three-dimensional finite element analysis. Materials and methods : Models of the screw type implant were used to model the implant as a form placed in the mandibular premolar region applying a three-dimensional finite element method. Screw type implant designs were classified into 4 types of parallel ones and 7 types of tapered ones. Other factors were simulated to represent clinical environment. Results : In parallel implant designs, higher and wider threads resulted in higher insertion torques and higher stress distributions. In tapered implant designs, changes in the taper led to remarkable differences in the insertion torques. It was difficult to determine a certain tendency of stress distribution around the implants since the stress level was too high around them. In tapered implant designs, smaller implants demonstrated lower insertion torques than the original type and were relatively less dependent on the degree of taper. Tapered implants showed higher insertion torques and higher stress distributions than parallel implants. Conclusion : According to this study, although the tapered implant demonstrated a higher insertion torque than the parallel implant, stress tended to be concentrated in the entire fixture of the tapered implant due to the inefficient stress distribution.

• Journal of Dental Rehabilitation and Applied Science
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• v.26 no.2
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• pp.97-109
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• 2010

Purpose : This study was designed to evaluate the influence of implant abutment materials on detorque value and screw joint stability before and after dynamic fatigue test. Materials & Methods : The external hexagonal fixture and three different groups of abutment (titanium abutments, zirconia abutments, and UCLA abutments) were used. The detorque value before loading and after loading (cyclic loading up to $10^5$ cycles) of the abutment screw were measured. Result : 1. There was no significant difference in detorque value before loading among the each group. 2. There was no significant difference in detorque value after loading among the each group. 3. Detorque values before and after cyclic loading in each group were not significantly different. 4. There was no significant difference in loss percentage of removal torque before loading among the each group. 5. There was no significant difference in loss percentage of removal torque after loading among the each group. 6. There was no significant difference in loss percentage of removal torque according to loading among the each group. Conclusion : Short term screw loosening of three types of abutment was not significantly different. When bite force was applied, there was no significant difference in screw loosening between before loading and after loading.

• Journal of Dental Rehabilitation and Applied Science
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• v.25 no.1
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• pp.53-59
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• 2009

The purpose of this study was to clarify the clinical efficiency of tungsten carbide/carbon coating on obtaining optimal preload of abutment screw compared with non-coated screw in external-hex implant system. In the present work, rotational value and the compressive force between abutment and fixture of abutment screws without coating and with coating tightened to 30Ncm were measured. Mean compressive force of coated screw was 504.6N. Then uncoated screw was tightened to clamping the abutment and the implant to 504.6N, and the tightening torque value and the rotational value was recorded. The following conclusions were drawn within the limitation of this study. Compressive force of coated screw was higher than that of uncoated screw after tightening at 30Ncm. The tightening torque that was nedeed to clamping the uncoated screw equal to coated screw tightened to 30Ncm was 55.6Ncm. In case of equal compressive force, there was no significant difference in rotation value between coated and uncoated screw.

• Journal of Welding and Joining
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• v.34 no.2
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• pp.1-10
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• 2016

The use of materials for modern lightweight auto-bodies is becoming more complex than hitherto assemblies. The high strength materials nowadays frequently used for more specific fields such as the front and rear sub frames, seat belts and seats are mounted to the assembled body structure using bolt joints. It is desirable to use nuts attached to the assembled sheets by projection welding to decrease the number of loose parts which improves the quality. In this study, nut projection welding was carried out between a nut of both boron steel and carbon steel and ultra-high strength hot-stamped steel sheets. Then, the joints were characterized by optical and scanning electron microscope. The mechanical properties of the joints were evaluated by microhardness measurements and pullout tests. An indigenously designed sample fixture set-up was used for the pull-out tests to induce a tensile load in the weld. The fractography analysis revealed the dominant interfacial fracture between boron steel nut weld which is related to the shrinkage cavity and small size fusion zone. A non-interfacial fracture was observed in carbon steel nut weld, the lower hardness of HAZ caused the initiation of failure and allowed the pull-out failure which have higher in tensile strengths and superior weldability. Hence, the fracture load and failure mode characteristics can be considered as an indication of the weldability of materials in nut projection welding.

• Korean Journal of Digital Imaging in Medicine
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• v.13 no.2
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• pp.63-69
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• 2011

Table strapis patient fixture for securing the patient movements and falls. if it designed to measure the abdominal circumference and used as an indicator of dose selection at CT scan. it will prevent the overexposure of dose without degradation of image quality and efficiently manage dose of each type of body to technician to deal with CT. First, in order to compare the dose used in CT image and qualitative characteristics. reference image is obtained by examining the abdominal phantom in same conditions with the hospital 120 kVp, 200 mAs, D-Dom (Dynamic Dose Of Modulation). SNR, PSNR, RMSE, MAE, CTDIvol of CT images are compared with reference image. for comparing with reference image, the image that Umbilicus level image of Abdomen CT is stored in the PACS were used. For comparison, the top 12 o'clock portion of the air drawn from the same ROI was measured. CTDIvol, mAs, etc. In order to analyze the characteristics of the image, by measuring the length of the umbilicus circumference, pattern of the dose was analyzed. by using the analyzed perimeter and dose information, To be identified visually, fixed band that scale marked were produced. Use them, If the length of circumference of less than 60 cm 100 mAs, Case of 61~80 cm 120 mAs, Case of 80~100 cm 150 mAs, more than 100 cm 200 mAs, dose selection based on the perimeter, the image was applied. by compare analyzed with the Reference Image, image quality was assessed. by compare with existing tests that equally 200 mAs applied, How much was confirmed that the dose reduction. 1. Depending on the Abdominal circumference, the average PSNR(dB) of the image that differently dose applied was 45.794. 2. Comparing with existing test. the dose of scan that adjusted the mAs depending on the circumference was decreased about 40%. SNR and PSNR of the image that obtained by adjusting the standard mAs based on dose modulation were not much different. Therefore, By choosing a low mAs. dose reduction can be obtained. and the dose selection method that measured Abdominal circumference using a fixed band can protect the overexposure and uniformly apply dose of each type of body to technician to deal with CT.

• Journal of architectural history
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• v.21 no.5
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• pp.33-46
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• 2012

The purpose of this study lies on reinterpreting the geography books in Joseon dynasty as records of the cities and consequently suggesting directions for further urban research. Geography books of Joseon dynasty are valuable references to understand the national policy, and imply that the focus of the contents is on the system. Especially, military system is an important concept to understand city type in that period, relationships between cities, selection of location, etc. The results of review are as following: First, military system is not a permanent fixture and therefore reflects changes in urban policies along with the history. The system suggests valuable clues on urban development as it is state-run, and closely associated with national land development. Second, counties and prefectures under jurisdiction of district called Eupchi(邑治) had cities as important as or even more important than local government such as Yeong-a(營衙), Jinbo(鎭堡), Yeok(驛: administrative cities). Such special regions need to be studied as other type of cities in Joseon dynasty by defining their architectural characteristics and roles. Third, the relationship of cities such as Eupch, Yeong-a, and Jinbo, was reorganized according to the local military system. Eupchi, administrative city, along with Yeong-a and Jinbo evolved into a military city as it became systematically organized. The characteristics of Yeok needs to be reconsidered in the context of such new inter-city relationship. Fourth, considerations which should be reviewed in the geography based on this concept can be mainly classified into architecture and landscape. This will also lay the foundation, and suggest new directions for further research for Eupchi, Yeong-a, Jinbo, and Yeok. Fifth, description of the geography looks simple at first sight, but with thorough understating on the system, there are chances to interpret objective reasoning of position and landscape in the overall flow of region, area, etc. Bongsu(烽燧), signal-fire, can be an object of comparison with geographical features and position. Furthermore, advantageous position is a historical and geographical element showing the major context of the region.

• The Journal of Korean Academy of Prosthodontics
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• v.45 no.6
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• pp.780-786
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• 2007

Statement of problem. The performance and maintenance of implant-supported prostheses are primarily dependent upon load transmission both at the bone-to-implant interface and within the implant-abutment-prosthesis complex. The design of the interface between components has been shown to have a profound influence on the stability of screw joints. Purpose. The Purpose of this study was to compare the strength and the fatigue resistance of 1-piece and 2-piece abutment connected to oral implant, utilizing an internal conical interface. Material and methods. Twenty $Implatium^{(R)}$ tapered implants were embedded to the top of the fixture in acrylic resin blocks. Ten $Combi^{(R)}$(1-piece) and $Dual^{(R)}$(2-piece) abutments of the same dimension were assembled to the implant, respectively. The assembled units were mounted in a testing machine. A load was applied perpendicular to the long axis of the assemblies and the loading points was at the distance of 7mm from the block surface. Half of 1-piece and 2-piece abutment-implant units were tested for the evaluation of the bending strength, and the others were cyclically loaded for the evaluation of the fatigue resistance until plastic deformation occurred. Nonparametric statistical analysis was performed for the results. Results. Mean plastic and maximum bending moment were $1,900{\pm}18Nmm,\;3,609{\pm}106Nmm$ for the 1-piece abutment, and $1,250{\pm}31Nmm,\;2,688{\pm}166Nmm$ for the 2-piece abutment, respectively. Mean cycles and standard deviation when implant-abutment joint showed a first plastic deformation were $238,610{\pm}44,891$. cycles for the 1-piece abutment and $9,476{\pm}3,541$ cycles for the 2-piece abutment. A 1-piece abutment showed significantly higher value than a 2-piece abutment in the first plastic bending moment (p<.05), maximum bending moment (p<.05) and fatigue strength (p<.05). Conclusion. Both 1-piece and 2-piece conical abutment had high strength and fatigue resistance and this suggests long-term durability without mechanical complication. However, the 1-piece conical abutment was more stable than the 2-piece conical abutment in the strength and the fatigue resistance.

• Journal of Dental Rehabilitation and Applied Science
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• v.31 no.3
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• pp.203-211
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• 2015

Purpose: The purpose of this study was to investigate the reosseointegration periods when the rough surface implants, which had complete bone-implant ankylosis, suddenly losed the osseointegration. Materials and Methods: The implants with RBM surface treatment were inserted into both tibias of 23 rabbits. Two implants were submerged into each side. After six weeks, the primary removal torque was measured by Digital torque gauge, and then the implants were replaced and submerged to estimate the level of reosseointegration. After assigned healing periods for each group, the removal torque was measured again. BIC (Bone-Implant contact, %) ratio was measured through histomorphometric analysis.Paired t-test was processed by SPSS 14.0. One-way ANOVA and Tukey's post-hoc test was processed to analyze statistically significant differences among the groups. Results: In comparison with the primary removal torque, the secondary removal torque was increased after 11 days and significantly increased from 2 weeks. In fluorochrome labeling, the origin of mineralization was observed after 7 days, which showed as fluorescent bands around the bone-implant interfaces. After 11 days, the bone formation was apparent, and it is increased continuously with the passage of the time. Conclusion: In 11 days after the implant replacement, the secondary removal torque was almost as same as the primary value, and was significantly higher from 2 weeks. The mineralized shapes were observed in 7 days after the implant replacement, and then the bone formation appeared visibly in 11 days.