• Journal of Korean Orthopaedic Sports Medicine
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• v.8 no.1
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• pp.26-32
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• 2009

Purpose: This study was performed to compare the strength of ligamentous attached sites of cadaveric distal femur and to obtain reliable biomechanical data to use in ligamentous reconstruction or augmentation. Materials and Methods: Fifteen cadaveric distal femurs were used for this study. After measuring the bone density, 5.0 mm cannulated screw (Experiment 1) or reconstructed porcine ligament (Experiment 2) was inserted into the each ligamentous attached sites of anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), medial collateral ligament (MCL) and lateral collateral ligament (LCL). In experiment 2, reconstructed porcine graft was fixed with bioabsorbable screw in ligamentous insertion sites. And we measured the maximal pullout force of each ligamentous attached sites of cadaveric distal femur. Results: Average bone mineral density was $1.205{\pm}0.137\;g/cm^2$ in experiment 1, $1.236{\pm}0.089\;g/cm^2$ in experiment 2, which showed no statistically significant differences. In experiment 1, average pull-out strength of ACL, PCL, MCL and LCL group were $519.1{\pm}111.7$ N, $638.9{\pm}144.4$ N, $169.7{\pm}56.0$ N, $225.6{\pm}61.5$ N respectively. In experiment 2, the average pull-out strength were $310.6{\pm}31.0$ N, $379.9{\pm}47.4$ N, $104.0{\pm}14.4$ N, $131.5{\pm}21.9$ N respectively. In experiment 1, there was no significant difference between ACL and PCL group and between MCL and LCL group. However, the maximal pullout strength of MCL and LCL group were significantly lower than that of ACL and PCL group (p<0.01). Experiment 2 showed the same results of experiment 1. Conclusion: Because stiffness of MCL and LCL attached sites are much lower than that of ACL and PCL attached sites, we may consider augmented fixation in ligamentous reconstructions of MCL and LCL.

• Journal of Welding and Joining
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• v.14 no.3
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• pp.41-47
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• 1996

The spot weldability of coated steels for automobile has been investigated. Coated steels of SPC-Zn DC, SPC Zn-Ni SC, SPC Zn-Ni DC, SPC Zn-Fe DC and OCCS were welded under different conditions of welding current, force and time. Coating thickness at the welded surface was reduced as increased welding current. Tensile shear strength(TSS) and cross tensile strength (CTS) were increased up to expulsion began, then dropped as increased current. Optimum conditions of welding force and time were different, however 200~250kgf and 15~20cycle were optimum for coated SPC (Steel Plate Cold). Weldability lobes were measured for each coated steel and they showed narrow range of working welding current. The organic composite coated steel (OCCS) had the highest current to get $\sqrt5{t}$ nugget size and narrowest working welding current range.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.06a
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• pp.77-78
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• 2009

• Journal of the Korean Arthroscopy Society
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• v.14 no.2
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• pp.92-101
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• 2010

The Hamstring autograft and the bone patellar bone tendon autograft have been widely used for anterior cruciate ligament reconstruction. In recent years, use of hamstring autograft for ACL reconstrution has been increased. The reason seems to be the advantages of the hamstring tendon such as high ultimate tensile load, low donor site morbidity and development of graft fixation method. These theoretical advantages have been increased as studies have shown that hamstring tendons actually regenerate after harvesting for ACL reconstruction. However, the concerns have arisen regarding the disadvantages of hamstring harvest, which were weakness of tibial internal rotation, the loss of flexion strength. The flexion strength loss has been controversial, therefore it needs to study whether restoration of flexion strength after hamstring regeneration is or not. In this study, we reviewed the current research of concerns on the advantage and disadvantage of hamstring tendon autograft and the hamstring regeneration. Furthermore, we compared the earlier studies and experiences regarding Hamstring regeneration with our research.

• The Journal of Korean Academy of Prosthodontics
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• v.46 no.2
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• pp.148-156
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• 2008

Statement of problems: Self-etch adhesives exhibit some clinical benefits such as ease of manipulation and reduced technique-sensitivity. Nevertheless, some concern remains regarding the bonding effectiveness of self-etch adhesives to enamel, in particular when so-called 'mild' self-etch adhesives are employed. This study compared the microtensile bond strengths to ground enamel of the two-step self-etch adhesive Clearfil SE Bond (Kuraray) to the three-step etch-and- rinse adhesive Scotchbond Multi-Purpose (3M ESPE) and the one-step self-etch adhesive iBond (Heraeus Kulzer). Purpose: The purpose of this study was to determine the effect of a preceding phosphoric acid conditioning step on the bonding effectiveness of a two-step self-etch adhesive to ground enamel. Material and methods: The two-step self-etch adhesive Clearfil SE Bond non-etch group, Clearfil SE Bond etch group with prior 35% phosphoric acid etching, and the one-step self-etch adhesive iBond group were used as experimental groups. The three-step etch-and-rinse adhesive Scotchbond Multi-Purpose was used as a control group. The facial surfaces of bovine incisors were divided in four equal parts cruciformly, and randomly distributed into each group. The facial surface of each incisor was ground with 800-grit silicon carbide paper. Each adhesive group was applied according to the manufacturer's instructions to ground enamel, after which the surface was built up using Light-Core (Bisco). After storage in distilled water at $37^{\circ}C$ for 1 week, the restored teeth were sectioned into enamel beams approximately 0.8*0.8mm in cross section using a low speed precision diamond saw (TOPMET Metsaw-LS). After storage in distilled water at $37^{\circ}C$ for 1 month, 3 months, microtensile bond strength evaluations were performed using microspecimens. The microtensile bond strength (MPa) was derived by dividing the imposed force (N) at time of fracture by the bond area ($mm^2$). The mode of failure at the interface was determined with a microscope (Microscope-B nocular, Nikon). The data of microtensile bond strength were statistically analyzed using a one-way ANOVA, followed by Least Significant Difference Post Hoc Test at a significance level of 5%. Results: The mean microtensile bond strength after 1 month of storage showed no statistically significant difference between all adhesive groups (P>0.05). After 3 months of storage, adhesion to ground enamel of iBond was not significantly different from Clearfil SE Bond etch (P>>0.05), while Clearfil SE Bond non-etch and Scotchbond Multi-Purpose demonstrated significantly lower bond strengths (P<0.05), with no significant differences between the two adhesives. Conclusion: In this study the microtensile bond strength to ground enamel of two-step self-etch adhesive Clearfil SE Bond was not significantly different from three-step etch-and-rinse adhesive Scotchbond Multi-Purpose, and prior etching with 35% phosphoric acid significantly increased the bonding effectiveness of Clearfil SE Bond to enamel at 3 months.

• Journal of Korean Society of Steel Construction
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• v.11 no.3 s.40
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• pp.319-327
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• 1999

This study makes mechanism of the fatigue strength improvement by the processing of weld toe clear for the vertical cross rib specimens which was made fillet weld joint, also it proposes to the appropriate later processing. As a result of tension fatigue test, the fatigue strength improvement could have been seen in later processed specimens than as-weld specimens. Especially fatigue crack initial life $N_c$ increased in specimens which processed grinder after hammer-peening. Also, fatigue crack propagation life $N_p$ improved more in hammer-peening specimens than as-weld or TIG specimens. It thinks that $N_c$ is because of the geometrical shape of weld toe, i.e. the relaxation of the stress concentration and also that $N_p$ is because the big compression residual stress which was introduced in the surface by hammer-peening is restraining the propagation of fatigue crack.

• Journal of the Society of Naval Architects of Korea
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• v.33 no.3
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• pp.1-7
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• 1996

The stress concentration factor gives the significant effect the fatigue strength of welded joints. The model used herein is the type of the load carrying fillet welded cruciform joint with full or partial penetration. In order to obtain the stress concentration factor at the weld toe of fillet joint, the reasonable element size of the toe part is investigated and the stress analysis for the series models by FEM under tensile load is performed. On the basis of the calculation results, the estimated formulae for the stress concentration factor(Kt) at weld toe part of the fillet welded joint, which the effect of toe radius, flank angle and other parameters are taken into account, is derived.

• Journal of the Korean Arthroscopy Society
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• v.9 no.2
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• pp.222-231
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• 2005

Purpose: This article describes a double-bundle ACL reconstruction technique using a five-strand hamstring tendon autograft with conventional anteromedial bundle reconstruction and additional posterolateral bundle reconstruction. Operative technique: For the tibial tunnel, the conventional single tunnel technique is performed and for the femoral tunnel, the double tunnel technique is performed with the anteromedial and posterolateral bundle. After minimal notchplasty, the anteromedial femoral tunnel is prepared with leaving one milimeter of posterior femoral cortex within the over-the-top, which if positioned at the 11-o'clock orientation for the right knee or at the 1-o'clock position for the left knee. The posterolateral femoral tunnel that is located 5 to 7 mm superior to the inner margin of the lateral meniscus anterior horn at $90^{\circ}$ of flexion is prepared with tile outside-in technique using a 4.5 cannulated reamer. The graft material for the double bundle reconstruction is made of the conventional four-strand hamstring autograft in the anteromedial bundle and of a single-strand semitendinosus tendon in the posterolateral bundle. The anteromedial bundle is fixed with using a rigid fix system on the femoral side and the posterolateral bundle is fixed to tie with the miniplate from the outside femur. Then, with the knee in $10^{\circ}\;to\;20^{\circ}$ of flexion, a bioabsorbable screw is simultaneously applied to achieve tibial fixation with tensioning of both bundles. Conclusion: A double bundle reconstruction with five-strand hamstring autograft, which is designed with a favorable conventional anteromedial bundle and an additional posterolateral bundle to restore rotation stability, seems to be a very effective method for the treatment for ACL instabilities.