• Archives of Plastic Surgery
• /
• v.32 no.6
• /
• pp.739-743
• /
• 2005

Subcondylar fractures have generally been treated by intermaxillary fixation except in cases where there is an absolute indication for open reduction. The reason behind a less aggressive surgical approach lies on the inherent difficulties in manipulating fragments in such a small area at the risk of damaging facial nerves or vessels such as the internal maxillary artery. However, long-term follow-up studies showed that conservative treatment of subcondylar fractures results in disturbances of occlusal function, deviation of the mandible, internal derangement of the temporomandibular joint, and ankylosis of the joint. We carried out open reduction of dislocated subcondylar fractures in 14 patients from 2000 to 2004 by a retromandibular approach. After the reduction of fractured bone, two H-shaped miniplates with 6 holes were fixed with screws at the anterior and posterior surfaces of the subcondyle. The retromandibular approach allowed good access and easy manipulation of the subcondyle. Immediate relief from malocclusion and correction of mandibular midline shifting were observed in all patients. Late temporomandibular dysfunction and ankylosis were not observed. Open reduction with plate osteosynthesis made it possible to avoid IMF in 7 of the 14 patients. The present study shows that open reduction through this retromandibular approach can produce good outcome in adult patients with subcondylar fracture.

• Archives of Plastic Surgery
• /
• v.36 no.6
• /
• pp.735-742
• /
• 2009

Purpose: The management of fractures of mandibular subcondyle continues to be controversial between open and closed treatment. The purpose of this article is to explain the endoscopic assisted open reduction and internal fixation and minimize the controversy. Methods: Nine patients of mandibular subcondylar fracture were reduced and fixed by using intraoral endoscopic - assisted open reduction and internal fixation and were followed up for 14 ~ 24 months after surgery. Results: Eight patients of mandibular subcondylar fracture had been treated without significant complications. One patient, whose malocclusion had been remained, was recovered normal occlusion by maxillomandibular fixation using intermaxillary screws for 3 weeks. Conclusion: The advantages of endoscopic - assisted open reduction and internal fixation are direct visualization, accurate fracture repair, minimized scar, decreased morbidity. And maxillomandibular fixation is not needed when it is done by accurate reduction and rigid fixation with one miniplate in the region of subcondylar fracture. With the above consideration, endoscopic - assisted open reduction and internal fixation can be considered as one of the best treament for subcondylar fracture of the mandible.

• Biomaterials and Biomechanics in Bioengineering
• /
• v.5 no.1
• /
• pp.37-50
• /
• 2020

Development of lightweight implant plates are important to reduce the stress shielding effect for a prosthesis of femur bone fractures. Stainless steel (SS-316L) is a widely used material for making implants. Stress shielding effect and other issues arise due to the difference in mechanical properties of stainless steel when compared with bone. To overcome these issues, composite materials seem to be a better alternative solution. The comparison is made between two biocompatible composite materials, namely Ti-hydroxyapatite and Ti-polypropylene. "Titanium (Ti)" is fiber material while "hydroxyapatite" and "polypropylene" are matrix materials. These two composites have Young's modulus closer to the bone than stainless steel. Besides the variety of bones, present paper constrained to femur bone analysis only. Being heaviest and longest, the femur is the most likely to fail among all bone failures in human. Modelling of the femur bone, screws, implant and assembly was carried out using CATIA and static analysis was carried out using ANSYS. The femur bone assembly was analyzed for forces during daily activities. Ti-hydroxyapatite and Ti-polypropylene composite implants induced more stress in composite implant plate, results less stress induced in bone leading to a reduction in shielding effect than stainless steel implant plate thus ensuring safety and quick healing for the patient.

• Clinics in Shoulder and Elbow
• /
• v.2 no.2
• /
• pp.133-137
• /
• 1999

Purpose: There are so many different methods with the their own advantages and disadvantages for acute AC dislocation and distal unstable clavicle fracture. We evaluated the usefulness of temporary Bosworth's coracoclavicular fixations using the cannulated screw and reviewed our clinical results. Materials and Methods: We evaluated 34 cases of temporary coracoclavicular fixations with cannulated screw and washer for acute AC dislocation(25cases in the Type V, Ⅲ) and distal unstable clavicle fracture(9cases in the Type ⅡB, Ⅱ+Ⅲ). All cases were fixed by the same techniques, guided cannulated screw under C-arm after the repair of the CC ligament within 1 week. Bases on the regular check, screws were removed at the 6-12 weeks under local anesthesia. The final clinical and radiological results(average 14 months follow-up) were rated with the UCLA scale. Results : All shoulders were gained nearly full ROM passively at the 3-4 weeks. The overall satisfactory resuIts(excellent or good) were achieved 88%(22/25) in the acute AC dislocation and all in the distal unstable clavicle fracture. There were no definite complications except three initial fixations loosening. Conclusion: Temporary Bosworth's coracoclavicular fixation using the cannulated screw with guided pin was simple precedure and provided enough initial stability for acute AC dislocation and distal unstable clavicle fracture.

• Journal of the Korean Society of Industry Convergence
• /
• v.23 no.4_1
• /
• pp.531-539
• /
• 2020

When injection mold is repeatedly used for mass production, fatigue phenomenon due to cyclic stress may occur. The surface and interior of structure might be damaged due to cyclic stress or strain. The objective of this study was to analyze failure of SCM435 high-tension bolts connecting upper and lower parts of a three-stage injection molding machine. These bolts have to undergo an accurate heat treatment to prevent the formation of chromium carbide and the action of dynamic stresses. Bolts were fractured by cyclic bending stress in the observation of ratchet marks and beach marks. Damaged specimen showed an acicular microstructure. Impurity was observed. Chromium carbide was observed near the crack origin. Both shape parameters of the Vickers hardness were similar. However, the scale parameter of the damaged specimen was about 20% smaller than that of the as-received specimen. Much degradation occurred in the damaged specimen. Bolts should undergo an accurate heat treatment to prevent the formation of chromium carbide. They must prevent the action of dynamic stresses. Bolts need accurate tightening and accuracy of heat treatment and screws need compression residual stress due to peening.

• The Journal of Korean Academy of Prosthodontics
• /
• v.42 no.1
• /
• pp.83-93
• /
• 2004

Statement of problem : Since the concept of osseointegrated dental implant by $Br{\aa}nemark$ et al was first applied to mandibular full edentulous patients. Recently it is considerated the first treatment option on missing teeth. A common problem associated with dental implant restorations is loosening of screws that retain the prosthesis to the abutment and the abutment to the implant fixture. Purpose : This study is to examine the influence on screw loosening of implant-abutment designs. Material and methods : External hex, cone screw, beveled hex, cam cylinder, cylinder hex by means of evaluating the loosening torques, with respect to a range of tightening torques after repeated loading. Result : 1. Cone screw, beveled hex groups are the highest initial tightening rate and cylinder hex, external hex groups are the lowest initial tightening rate (p < 0.05). 2. Cone screw groups are the highest after repeated loading tightening rate and cylinder hex groups are lowest after repeated loading tightening rate(p < 0.05). 3. Cone screw groups have the highest initial stability and anal stability. 4. All groups are decreased tightening rate after repeated loading.

• Steel and Composite Structures
• /
• v.19 no.5
• /
• pp.1145-1165
• /
• 2015

A behavior model for screw connections is developed to provide a better representation of the nonlinear response of thin steel plate shear walls (TSPSWs) with infill plates attached to the boundary frame members via self-drilling screws. This analytical representation is based on the load-bearing deformation relationship between the infill plate and the screw threads. The model can be easily implemented in strip models of TSPSWs where the tension field action of the infill plates is represented by a series of parallel discrete tension-only strips. Previously reported experimental results from tests of two different TSPSWs are used to provide experimental validation of the modeling approach. The beam-to-column connection behavior was also included in the analyses using a four parameter rotational spring model that was calibrated to a test of an identical frame as used for the TSPSW specimens but without the infill plates. The complete TSPSW models consisting of strips representing the infill plates, zero length elements representing the load-bearing deformation response of the screw connection at each end of the strips and the four parameter spring model at each beam-to-column connection are shown to have good agreement with the experimental results. The resulting models should enable design and analysis of TSPSWs for both new construction and retrofit of existing buildings.

• The Journal of Korean Academy of Prosthodontics
• /
• v.45 no.3
• /
• pp.345-353
• /
• 2007

Statement of problem. Implant abutment screw joints tend to loosen under clinical conditions. Abutment screw loosening results in loss of preload in function. Purpose. Anti-rotational inner post screw (ARIPS) systems were compared with conventional abutment screws to reduce screw loosening. Reverse torque values were evaluated. Material and methods. 32 implant assemblies (Warentec, Co, Ltd, Seoul, Korea) were organized as the 30-Ncm-torque conventional groups and 30-Ncm-torque ARIPS groups in external and internal system. The specimens were tested to 106 cycles at a load of 200N. Preload reverse torque, postload reverse torque, and the ratio of postload reverse torque to preload reverse torque were evaluated. The data were analyzed with unpaired t-test in external and internal systems. Results. In the ratio of postload reverse torque to preload reverse torque, the ARIPS groups showed significant differences than the conventional screw group in both external and internal system. Conclusion. Within the limitations of this study, abutment screw loosening was effectively reduced using ARIPS system.

• Archives of Craniofacial Surgery
• /
• v.15 no.3
• /
• pp.129-132
• /
• 2014

Facial skeletal remodeling was revolutionized more than 30 years ago, by the work of Tessier and other craniofacial surgeons. However, the need to correct the skeleton in the upper third of the face is not frequently diagnosed or treated in aesthetic facial surgery. Here, we report on the aesthetic correction of a protrusive forehead. A patient visited our hospital for aesthetic contouring with a prominent forehead. The anterior wall of the frontal sinus was removed with a craniotome via the bicoronal approach. After the excised bone was repositioned, it was fixed with a titanium mesh plate and screws. An electric burr was used to contour the supraorbital rim and frontal bone. Once the desired shape was achieved, the periosteum was replaced, and the wound was closed in layers. When performed properly, frontal sinus contouring could significantly improve the appearance in patients with a prominent forehead. Plastic surgeons must carefully evaluate patients with a prominent forehead for skeletal remodeling that involves the accurate and safe repositioning of the anterior wall of the frontal sinus.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.53 no.4
• /
• pp.213-223
• /
• 2004

In the machine tool industry, direct drive linear motor technology is of increasing interest as a means to achieve high acceleration, and to increase reliability. The advantages of such a motor are that it has a good linearity and has no need of such mechanical energy conversion parts, which change rotary motion into linear motion, as screws, gears, chains etc In this paper, two structures of LOA are analyzed. One is the moving-coil type LOA and the other is moving-magnet type LOA. Two types of LOA are analyzed, with reference to the following parameters as variables: magnetic field, flux linkage, motor thrust and back emf. These variables are derived by the use of analytical method in terms of two-dimensional rectangular coordinate system. The maximum values of thrust according to such design parameters as air-gap length and magnet height for each model is also represented. The results are validated extensively by comparison with finite element method. In particular, we experiment moving-coil LOA which is already manufactured and confirm that the experimental results are shown in good agreement with analysis through the comparison of between analytical and experimental results