• The Journal of Korean Academy of Prosthodontics
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• v.35 no.3
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• pp.557-565
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• 1997

Screw-shaped implants of commercially pure (c.p.) titanium, c.p. niobium, c.p. zirconium, and stainless steel(Sus 304) were inserted in the rabbit tibial bone over 12 weeks of follow-up. New developed torque gauge instrument was used to evaluate the implant holding power and a image analysis program coupled to a microscope was used for histomorphometry. The three best consecutive threads of each implant were measured. Quantitative analyses at 12 weeks revealed a partial bone contact to the four kinds investigated metals. There were no obvious adverse tissue reactions to any of the biomaterials. At 12 weeks the average removal torques for titanium, niobium and zirconium were better than that needed for Sus 304 screws, on the other hand high score of bony contact ratio of titanium and niobium were showed in comparison to those of zirconium and Sus 304. There was no significant differences in the amount of interfacial bone of zirconium and Sus 304 whereas there was significant difference in the torque forces of niobium and Sus 304. Three months after implant insertion, the average removal torque was 6.64 Ncm for the titanium, 6.57 Ncm for the niobium, 6.38 Ncm for the zirconium, and 4.25 Ncm for the Sus 304. On average bone contacts there were 51.24% in the titanium, 48.19% in the niobium, 31.79% in the zirconium, 23.54% in the Sus 304. Biocompatibility of the titanium, niobium and zirconium was acceptable level in comparison to the Sus 304.

• The Journal of Korean Academy of Prosthodontics
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• v.32 no.4
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• pp.573-592
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• 1994

A two-stage procedure is ideal for getting a successful osseointegration. But if a one-stage procedure can achieve a similar osseointegration, the one-stage procedure has several advantages. The purpose of this study was to observe the initial bone formation and bone remodeling of open type (nonsubmerged) and closed type (submerged) titanium implants. Eight ITI hollow-screws and eight Branemark fixtures were divided into two groups (submerged and nonsubmerged) and were installed on the lower jaws of four mongrel dogs. The animals were sacrificed three months later and bone sections with implants were processed for light microscopic and fluorescent microscopic observation. The results were as follows : 1 There was no significant difference in bone-to-implant contact between submerged and nonsubmerged implants. 2. Smooth surface titanium implants showed more bone-to-implant contact than that of titanium plasma coated implants histologically. 3. Under fluorescent microscopy, the active bone remodeling and new bone formation were observed in the interface zone. 4. Under fluorescent microscopy, submerged and nonsubmerged implants had no difference in bone remodeling pattern, and intramembranous bone formation was more prominent. 5. The connective tissue fibers orienting perpendicularly toward implant surface were oberved in the neck of implants.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.959-962
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• 2005

Servomotors are used as key components of automated system by performing accurate positioning, accurate speed regulation, and precise motion control in response to commands from computers and sensors. Especially linear brushless servomotors have numerous advantages over ball screws, timing belts, rack/pinion drives and friction drives compared with rotary servomotors. This paper proposes the estimation of unknown parameters from the linear brushless DC motor which is operated by sinusoidal commutation. The estimated parameters are used to tune the controller gain and disturbance observer. In order to agree with this purpose, Digital Signal Processor(TMS320F240), developed for implementation of a speed Field Oriented Control(FOC), adopted in this study. The processor playing an important role in controller has A/D converters, PWM generators, riched I/O port internally.

• Clinics in Shoulder and Elbow
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• v.19 no.1
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• pp.33-38
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• 2016

Background: This study was conducted to evaluate the surgical outcomes of plate fixation using autologous iliac bone graft shaped in the form of a matchstick in clavicle nonunion resulting from prior surgical or non-surgical management. Methods: From May 2005 to February 2013, 17 patients underwent surgery for clavicle nonunion. The mean age at the time of surgery was 48.8 years. The iliac bone was harvested and shaped into slivers approximately 3 cm long, which resembled matchsticks. After opening of the medullary canal, the plate and screws were applied and cancellous bone was placed at the nonunion site. Matchstick bone grafts which were longitudinally placed and encircled on the nonunion site were tied with periosteum using 3-4 stitches. Union was determined via postoperative plane X-ray. Clinical status was evaluated using the visual analogue scale score for pain, and Constant and American Shoulder Elbow Surgeon score. Results: All patients had a stable radiological union at the follow-up. The mean duration from index operation to nonunion operation was 13.2 months (7-32 months). The mean follow-up period was 20.1 months (8-56 months), and the mean duration until union was 11.2 weeks (8-16 weeks). All clinical scores were improved at the final follow-up (p<0.001). The mean segmental defect was $3.3{\pm}2.6mm$ (1-18 mm); and the difference in clavicular length between operative and non-operative site was $5.9{\pm}6.9mm$. Conclusions: Matchstick shaped autologous iliac bone grafting technique in clavicle nonunion is acceptable with a high union rate.

• Clinics in Shoulder and Elbow
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• v.19 no.1
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• pp.2-7
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• 2016

Background: The purpose of this study is to compare the radiological and clinical outcomes after open reduction and plate fixation of midshaft clavicle fractures between patients who achieved successful anatomical reduction and those who had a remaining fracture gap even after open reduction and plate fixation, and were thus treated with additional demineralized bone matrix (DBM). Methods: This retrospective analysis was conducted on 56 consecutive patients who underwent open reduction and internal fixation using a locking compression plate for acute displaced midshaft clavicle fractures, and who underwent radiographic and clinical outcome evaluations at least 6 months postoperatively. The outcomes between those who achieved perfect anatomical reduction without remnant gap (n=32) and those who had a remaining fracture gap even after open reduction and plate fixation treated with additional DBM (n=24) were evaluated. Results: There were no differences in the use of lag screws or wiring and operation time (all p>0.05) between those with and without remnant gap. No difference in the average radiological union time and clinical outcomes (satisfaction and Constant score) was observed between the two groups (all p>0.05). However, significantly faster union time was observed for AO type A fracture compared with other types (p=0.012), and traffic accident showed association with worse clinical outcomes compared with other causes of injury. Conclusions: Surgical outcome of midshaft clavicle fracture was more affected by initial fracture type and event, and re-reduction and re-fixation of the fracture to obtain a perfect anatomical reduction spending time appears to be unnecessary if rigid fixation is achieved.

• Journal of the Korean Society of Safety
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• v.26 no.4
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• pp.41-46
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• 2011

The purpose of this paper is to analyze the causes of accidents related to the 3 phase 170 kV gas insulated switchgear of a power system collected from accident sites to secure data for the prevention of similar accidents and provide important points of view regarding diagnosis for the prevention of accidents involving gas insulated switchgears. The analysis results of the causes of accidents involving gas insulated switchgears showed deformation of the manipulation lever installed at the S-phase, disconnection of the insulation rod connection, melting of the upper conductor, a damaged tulip, damage to the lower spacer and the spacer at the breaker, etc. It is believed from this result that the potential for accidents has expanded due to accumulated energy as a result of repeated deterioration. The carbonization depth of a GIS was formed near the screw (T2, T3) used to secure the lower pole of the S-phase tulip. It is not known what has caused the screws to be extruded and melted. However, it is thought that an unbalanced electromagnetic force, micro-discharge, surface discharge, etc., have occurred at that point. In addition, even though 16 years have passed since its installation, there was no installation defect, act of arson, accidental fire, etc. General periodical inspection and diagnosis failed to find the factors causing the accidents. As a system contained in a closed metal container, it has a high risk factor. Therefore, it is necessary to design, install and operate a GIS in accordance with the standard operational procedure (SOP). In addition, it is necessary to apply conversion technology for periodical SF6 gas analysis and precision safety diagnosis. It is expected that tracking and managing these changes in characteristics by recording the results on the history card will provide a significant accident prevention effect.

• Journal of Chest Surgery
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• v.49 no.1
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• pp.1-8
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• 2016

More than a century ago, the first scientific report was published about fracture fixation with plates. During the 1950's, open reduction and plate fixation for fractures were standardized by the founders of Arbeitsgemeinschaft $f{\ddot{u}}r$ osteosynthesefragen/Association for the Study of Internal Fixation. Since the introduction of plate fixation for fractures, several plates and screws have been developed, all with their own characteristics. To accomplice more fracture stability, it was thought the bigger the plate, the better. The counter side was a compromised blood supply of the bone, often resulting in bone necrosis and ultimately delayed or non-union. With the search and development of new materials and techniques for fracture fixation, less invasive procedures have become increasingly popular. This resulted in the minimally invasive plate osteosynthesis (MIPO) technique for fracture fixation. With the MIPO technique, procedures could be performed with smaller incisions and thus with less soft tissue damage and a better preserved blood supply. The last 5 years rib fixation has become increasingly popular, rising evidence has becomeavailable suggesting that surgical rib fixation improves outcome of patients with a flail chest or isolated rib fractures. Many surgical approaches for rib fixation have been described in the old literature, however, most of these techniques are obscure nowadays. Currently mostly large incisions with considerable surgical insult are used to stabilize rib fractures. We think that MIPO deserves a place in the surgical treatment of rib fractures. We present the aspects of diagnosis, preoperative planning and operative techniques in regard to MIPO rib fixation.

• Fire Science and Engineering
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• v.26 no.4
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• pp.82-88
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• 2012

To analyze the thermal characteristics of wire connection part that is connected to a screw-clamping terminal block depending on screw torque, the normal screw torque defined in KS C 2625 and the abnormal screw torque that can occur due to loosened screws resulting from defective work or aged deterioration were used as experimental variables. After the same load was applied to normal and abnormal screw torques, the thermal characteristics of the wire connector were measured and compared with a thermal imaging camera. The findings from this study will be used to detect heating due to defective screw torque at terminal block connections during electric safety inspection in the future and minimize the hazard of electric fire.

• Archives of Craniofacial Surgery
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• v.12 no.1
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• pp.33-36
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• 2011

Background: In a frontal sinus reconstruction, the literature primarily recommends a surgical approach for definite treatment with the exception of for anterior wall fractures with no dislocation. Many studies have assessed a range of methods for the reduction of frontal sinus fractures. This paper presents a case, in whom the anterior wall of the frontal sinus was reconstructed using an outer table calvarial bone graft in an en bloc manner. Patient and methods: A 36-year-old male visited the emergency room with a heavy injury to the forehead. He was diagnosed with fractures of the anterior and posterior wall of the frontal sinus. The neurosurgeon removed the fractured area and repaired the meninges. Afterwards, cranialization was performed and the opening of the nasofrontal duct was obstructed. After fixing the removed bone to its original location, all fragments of fractured anterior wall were purged out and the anterior wall reconstructed using an en bloc calvarial bone graft. Results: In the post-operative 8 months period, there were no complications, the round contour of the forehead was expressed well and the patient was satisfied with the result. Conclusion: There are many methods for reconstructing the anterior wall of the frontal sinus. On the other hand, in cases of large fracture sites with many fractured bone fragments, en bloc harvesting of the outer table calvarial bone could be a better choice than making use of only plates and screws because this method shows a good results in terms of aesthetics with a low complication rate.

• Archives of Craniofacial Surgery
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• v.16 no.1
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• pp.11-16
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• 2015

Background: Source material used to fill calvarial defects includes autologous bones and synthetic alternatives. While autologous bone is preferable to synthetic material, autologous reconstruction is not always feasible due to defect size, unacceptable donor-site morbidity, and other issues. Today, advanced three-dimensional (3D) printing techniques allow for fabrication of titanium implants customized to the exact need of individual patients with calvarial defects. In this report, we present three cases of calvarial reconstructions using 3D-printed porous titanium implants. Methods: From 2013 through 2014, three calvarial defects were repaired using custom-made 3D porous titanium implants. The defects were due either to traumatic subdural hematoma or to meningioma and were located in parieto-occipital, fronto-temporo-parietal, and parieto-temporal areas. The implants were prepared using individual 3D computed tomography (CT) data, Mimics software, and an electron beam melting machine. For each patient, several designs of the implant were evaluated against 3D-printed skull models. All three cases had a custom-made 3D porous titanium implant laid on the defect and rigid fixation was done with 8 mm screws. Results: The custom-made 3D implants fit each patient's skull defect precisely without any dead space. The operative site healed without any specific complications. Postoperative CTs revealed the implants to be in correct position. Conclusion: An autologous graft is not a feasible option in the reconstruction of large calvarial defects. Ideally, synthetic materials for calvarial reconstruction should be easily applicable, durable, and strong. In these aspects, a 3D titanium implant can be an optimal source material in calvarial reconstruction.