• Journal of the Korean Society for Precision Engineering
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• v.32 no.6
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• pp.517-521
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• 2015

Recent development of core techniques the IT electronics industry can condense into lightweight and slimmer. In this circumstance, researches for the lightweight materials and subminiature screw have been attracted. In this study, the CFRP was produced by stacking angle to obtain the tensile properties. And Comparing the coated screws and non-coated screws on the specimen, and evaluating the adequacy for the application of CFRP using the result. So The clamping force measured by comparison evaluation. Low screw reverse and Superior torque value at each stacking angle were found the optimum conditions, when Subminiature Screw is applied on smart devices. Both tensile strength and stiffness of $[{\pm}0^{\circ}]_{10}$ is the highest. Followed by $[90^{\circ}/0^{\circ}]_{10}$ is the highest. The largest clamping torque is $[90^{\circ}/0^{\circ}]_{10}$ When Subminiature Screw is applied coating and non-coating to prevent loosening. Based on the above, Subminiature Screw should be applied in smart devices, because $[90^{\circ}/0^{\circ}]_{10}$ meet both tensile properties and clamping force.

• Archives of Plastic Surgery
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• v.38 no.1
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• pp.102-104
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• 2011

Purpose: The standard treatments of hand fractures today are fixations by K -wires, metal plates, wires and lag screws. But it is very difficult to reconstruct fractures by placing implants into small bony fragments especially in the comminuted fractures and intra-articular fractures. This paper describes a simple method of reconstruction with Histoacryl$^{(R)}$ for comminuted and intra-articular fractures in hands. Methods: 2 cases with comminuted and intra-articular fractures by crushing injury were reconstructed with Histoacryl$^{(R)}$. We performed applying Histoacryl$^{(R)}$ with swab on the bone cortex carefully to avoid Histoacryl$^{(R)}$ infiltrating into the medulla. We could rearrange and fixate bony fragments using only Histoacryl$^{(R)}$, in addition, metal plates, K-wires, wires, and lag screws could be used for secondary fixation if needed. Results: Post-operative X-ray finding of 2 patients assured that the bony fragments of the hand fractures maintained their original positions. Significant displacement and deviation, infection, nonunion, and malunion during the follow-up period were not observed. Conclusion: This study showed the possibility of using Histoacryl$^{(R)}$ in addition as a simple method of fixation in the comminuted and intra-articular hand fractures.

• Industrial Engineering and Management Systems
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• v.10 no.3
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• pp.209-220
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• 2011

Self-tapping screws have some operational peculiarities. In spite of their economical advantage that requires no prior tapping operation, a weakness of self-tapping screw-tightening operations is that screws can easily be tightened at a non-right angle, thus resulting in an improper tightening strength. Increases in outsourced workers have reduced labor costs, but the accompanying high worker fluidity means that new workers are more frequently introduced into factories. It is necessary to train new workers for self-tapping screw-tightening operations, which occupies a considerable portion of ordinary assembly works. The purpose of this study is to develop and implement a skill transfer system for the operation. This study (1) proposes a set of characteristic values for evaluating the quality of the operation and develops a device that can measure these values; (2) proposes criteria for evaluating the resultant quality of the tightening; and (3) develops a skill training system for better work performance. Firstly, sets of characteristic values for evaluating the quality of the operation, namely, torque, vertical pressure forces and horizontal vibration forces, are proposed. A device that can measure these values is developed. Secondly, criteria for evaluating the resultant quality of the tightening are identified, involving tightening torque, maximum vertical pressure and timing, vibration area during the processing and tightening period, and work angle. By using such parameters, workers with the proper aptitude can be identified. Thirdly, a skill training system for the operation is developed. It consists of screwdriver operation training and screw-tightening training with feedback information about the results of the operation. Finally, the validity of the training system is experimentally verified using new operators and actual workers.

• Journal of Korean Neurosurgical Society
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• v.54 no.1
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• pp.25-29
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• 2013

Objective : To clarify the landmark for deciding the entry point for C1 lateral mass screws via the posterior arch by using 3-dimensional (3D) computed images. Methods : Resnick insisted that the C1 posterior arch could be divided into pure posterior and lateral lamina (C1 pedicle). Authors studied where this transition point (TP) is located between the posterior lamina and the C1 pedicle and how it can be recognized. The 3D computed images of 86 cadaver C1s (M : F=45 : 41) were used in this study. Results : The superior ridge of the C1 posterior arch had 2 types of orientation. One was in the vertical direction in the C1 posterior lamina and the other was in the horizontal direction in the C1 pedicle. The TP was located at the border between the 2 areas, the same site as the posterior end of the groove of the vertebral artery. On posterior-anterior projection, the posterior arch was sharpened abruptly at TP. We were unable to identify the TP in 6.4% of specimens due to complete or partial osseous bridges. A total of 93.8% of the TP were located between the most enlarged point of the spinal canal and the medial wall of the vertebral artery. Conclusion : The anatomic entry zone of C1 lateral laminar screws was clarified and identified based on the TP by using preoperative 3D computed images.

• The Journal of Korean Academy of Prosthodontics
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• v.35 no.4
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• pp.767-780
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• 1997

One of the most common problems of implant prosthesis is the screw loosening of abutment screws. This brings on discomfort in mastication, inflammation in the peri-implant tissue due to poor oral hygiene and fracture of prosthesis or loss of osseointegration. To prevent screw loosening, appropriate implantation to direct the occlusal force to the long axis of the implant, accurate design of the superstructure, decrease of the occlusal table, and adequate torque on the abutment screw are necessary. In this study the screw loosening torque was evaluated in implants with dimples or flutes in the internal surface of abutment screw holes. The abutments were fastened with slot type and hexagonal type abutment screws and were sealed with vinyl poly siloxane impression and bite registration material respectively. The screw loosening torque was evaluated after 1,800 and 12,600 times loading under a loading machine. The results were as follows. 1. The flute form group showed significantly higher loosening torque compared to the dimple form group and the group with no inner surface treatment (p<0.05). 2. There was no statistical difference in loosening torque according to the sealing materials. 3. The loosening torque according to the types of abutment screw showed no significant difference. 4. The loosening torque was significantly higher after 1800 times loading compared to 12600 times loading(p<0.05). From the above results. it is thought that formation of a flute in the internal surface of the screw hole decreases the chance of screw loosening, but the sealing materials and types of abutment screw did not show significant difference in prevention of screw loosening.

• Journal of Korean Foot and Ankle Society
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• v.14 no.1
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• pp.79-83
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• 2010

Purpose: To compare the clinical and radiological results between the anterior and posterior screw fixation for the treatment of talar neck fracture. Materials and Methods: Among 30 patients who received surgical treatment for talar neck fracture from 2001 to 2008. Twenty-seven patients with a follow-up period of more than 1 year were divided into two groups. Twelve patients were treated with anterior screw fixation and 15 patients with posterior approaches. We analyzed preoperative, postoperative and follow-up radiographs. Clinical results were evaluated by Hawkins criteria. Results: The posteriorly inserted screws were placed across the more central portion of the talar neck and perpendicular to the plane of fracture (p<0.05). There were no difference in clinical results, the duration of union, and complications including avascular necrosis between two groups. However, 2 patients complained of pain around the talonavicular joint in the anterior insertion group. Conclusion: Although the clinical results were good irrespective of insertion methods, the posterior approach of screw fixation for talar neck fractures allows for a better mechanical advantage than anterioly placed screws. This may allow early motion with a reduced risk of failure of fixation or of displacement of the fracture.

• Journal of Biomedical Engineering Research
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• v.23 no.1
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• pp.17-26
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• 2002

The purpose of this study was to investigate the important Parameters of the Pedicle screw by estimating the mechanical characteristics of screws under static and dynamic loads. Methodology for estimating Parameters under static load was proposed. It was also shown that the fatigue life of the one-level system could be increased by changing the shape of screws. Load parameters of the single pedicle screw were friction force. bending moment. and holding force. The test results of the one-level system could be inferred from teat results of the sin91e screw under bending force Fatigue life of the one-level system with flexible rod was longer than that of the upper Part test without rod . Considering the drop of flexibility of the rod due to muscles and ligament, fatigue life of the one-level system could be estimated b? that of the single screw.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.29 no.6
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• pp.438-443
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• 2003

Purpose : This study evaluated the usefulness of resorbable plate and screw for treatment of maxillofacial bone fractures. Patients and methods : From july, 2000 to july, 2002, we used resorbable plates and screws($Biosorb^{(R)}$ FX, Bionix Inc, Finland) on 126 patients for treatment of maxillofacial bone fractures. Among them, 80 patients were capable of periodic following up to present season. We evaluated these patients with clinical, radiographic findings and subjective satisfaction. Results : 80 patients composed of 63 men and 17 women. Complication rates are 7.5%(6/80) recorded. 1 of bulging sensation, 3 of infection sign, 2 of the plate detachment were shown. The plates involved in such complications were removed. The other patients(92.5%) were not shown any problems. We could not find complete resorption of screw holes in the mandibular symphysis area even though two years later after surgery. Conclusion : Bioresorbable plates and screws are useful as fixation material at maxillofacial fractures although strength is thought to be weaker than titanium plate. But to reduce the possible complicaions, need to careful clinical and radiographical evaluations.

• The Journal of Advanced Prosthodontics
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• v.11 no.6
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• pp.350-357
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• 2019

PURPOSE. This study aims to evaluate the loosening torque on the implant fixture, and to assess the accuracy of difference electronic torque drivers. MATERIALS AND METHODS. Three electronic torque drivers were used to measure the loosening torque on the implant system (AnyOne; MegaGen). The implant fixtures were divided among the 3 electronic torque driver types (W&H, SAESHIN, and NSK group) and 9 for each group. The screws were fastened at the implant fixture by three electronic torque drivers using the tightening torques recommended by the manufacturers of the drivers. After 10 minutes, the screws were again fastened at the implant fixture with equal torque. Then, the loosening torques were measured with an MGT12 torque gauge (MARK-10, Inc.). This measurement procedure was repeated 10 times under loosening torques of 15 Ncm, 25 Ncm, and 35 Ncm. In the statistical analysis, all values of loosening torque were analyzed with the one-way ANOVA and Kruskal-Wallis test (α=.05) for comparative evaluation. RESULTS. There were significant inter-group differences at loosening torques of 15 Ncm and 25 Ncm (P<.05). The accuracy of the NSK driver was the highest, followed by SAESHIN and W&H. There was no significant difference between NSK and W&H at 35 Ncm (P>.05). The SAESHIN driver showed the closest loosening torque at 35 Ncm. CONCLUSION. The most accurate loosening torques were SAESHIN at 35 Ncm, and NSK at 15 Ncm and 25 Ncm. Since the loosening torque may vary depending on the tightening torques and electronic torque drivers, periodic calibration of the electronic torque driver is recommended.

• Corrosion Science and Technology
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• v.7 no.3
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• pp.162-167
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• 2008

Degradable implants have been in use for bone surgery for decades. However, degradable metal implants are one of the new research areas of biomaterials science. Magnesium has good biocompatibility due to its low toxicity, and it is a corroding, i.e. dissolvable, metal. Furthermore, magnesium is needed in human body, and naturally found in bone tissue. There have been some published reports also asserting the potential bone cell activation or bone healing effect of high magnesium ion concentrations. The classic method for achieving intertransverse process fusion involves autogenous iliac crest bone graft. Several investigations have been performed to enhance this type of autograft fusion. However, there is no research which has been undertaken to investigate the efficiency of pure magnesium particles in posterolateral spinal fusion. In this study, corrosion behavior of magnesium metal at the bone interface, the possibility of new bone cell formation and the degree of effectiveness in producing intertransverse process lumbar fusion in a sheep model have been investigated. Cortical bone screws were machined from magnesium alloy AZ31 extruded rod and implanted to hip-bones of sheep via surgery. Three months after surgery, the bone segments carrying these screws were removed from the sacrificed animals. Samples were sectioned to reveal Mg/bone interfaces and investigated using optical microscope, SEM-EDS and radiography. Optical and SEM images showed that there was a significant amount of corrosion on the magnesium screw. The elemental mapping results indicate, due to the presence of calcium and phosphorus elements, that there exists new bone formation at the interface. Furthermore, sixteen sheep were subjected to intertransverse process spinal fusions with pedicle screw fixation at various locations along their spines. Each animal was treated with 5cc autograft bone at one fusion level and 1cc magnesium+5cc autograft bone at the other. Six months after surgery, bone formation was evaluated by gross inspection and palpation, and radiological, histological, scanning electron microscopic and x-ray diffraction analyses. It may be stated that the potential for using useful corrosion of magnesium alloys in medical applications is expected to be significant.