• Journal of the Korean Ceramic Society
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• v.43 no.3 s.286
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• pp.156-161
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• 2006

Impedance spectroscopy was applied to the initial hydration of calcium phosphate bone cements in order to investigate the electrical/dielectric properties. Hydration or equivalently setting was monitored as a function of the amount of water and initial powder characteristics. Higher amounts of water produced more open microstructures, leading to higher conductivity and enhanced dielectric constant. The effects of the initial characteristics in the powder were investigated using bone cement powder prepared with and without granulation. Granulated powder exhibited a significant change in resistance and produced a higher dielectric constant than those of conventional powder. Through a simplified modeling, the effects of thickness in reaction products and pore sizes were estimated by the frequency-dependent impedance measurements. Furthermore, impedance spectroscopy was proven to be a highly reliable tool for evaluating the continuous change in pore structure occurring in calcium phosphate bone cements.

• Journal of Technologic Dentistry
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• v.38 no.3
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• pp.143-149
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• 2016

Purpose: The purpose of this study is to evaluate the effect of two different oblique mechanical loading to occlusal surfaces of cement retained implant on the stress distributions in surrounding bone, using 3-dimensional finite element method. Methods: A 3-dimensional finite element model of a cement retained implant composed of three unit implants, simplified ceramic crown and supporting bone was developed according to the design of ement retained implant for this study. two kinds of surface distributed oblique loads(100 N) are applied to following occlusal surfaces in the single crowns; 1) oblique load on 2 occlusal points(50N for each buccal cusp, 2 buccal cusps exist), 2) oblique load on 4 occlusal points(25N for each buccal and lingual cusp, 2 buccal and 2 lingual cusps exist) Results: The results of the comparison of the stress distributions on surrounding bone are as follows. In the condition of oblique load on 2 occlusal points, VMS was 741.3 Mpa in the M1(Ø$4.0{\times}13mm$) model and 251.2 Mpa in the M2(Ø$5.0{\times}13mm$) model. It means the stress on the supporting bone is decreased. The results of oblique load on 4 occlusal points are similar to this one. Conclusion: Increasing the diameter of the implant fixture is helpful to distribute the stress on the supporting bone. Also, to obtain the structural stability of the supporting bone, it is effective to distribute the load evenly on the occlusal surface of crown in producing single crown implant.

• Journal of Biomedical Engineering Research
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• v.24 no.4
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• pp.369-373
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• 2003

The compressed fracture of spine caused by osteoporosis is one of the most frequent diseases in bone fracture. Recently the vertebroplasty has drawn much attention as a medical treatment for the compressed fracture of spine, which strengthens the vertebral body and corrects deformity, and relieves pain in patients by injecting bone cement. But because there were no research about strengthening of mechanical properties of verbral body in bone cement injection, in this study, based on the properties of PMMA, we had measured the Young's modulus for different apparent densities of intact trabecular bone and PMMA injected one from a porcine and a cadaver. Young's modulus to apparent density had a form of a power series in intact trabecular bone and had a linear relation in PMMA injected bone.

• Journal of Korean Neurosurgical Society
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• v.52 no.4
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• pp.353-358
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• 2012

Objective : The purpose of this study was to determine the efficacy of bone cement-augmented short segment fixation using percutaneous screws for thoracolumbar burst fractures in a background of severe osteoporosis. Methods : Sixteen patients with a single-level thoracolumbar burst fracture (T11-L2) accompanying severe osteoporosis treated from January 2008 to November 2009 were prospectively analyzed. Surgical procedures included postural reduction for 3 days and bone cement augmented percutaneous screw fixation at the fracture level and at adjacent levels without bone fusion. Due to the possibility of implant failure, patients underwent implant removal 12 months after screw fixation. Imaging and clinical findings, including involved vertebral levels, local kyphosis, canal encroachment, and complications were analyzed. Results : Prior to surgery, mean pain score (visual analogue scale) was 8.2 and this decreased to a mean of 2.2 at 12 months after screw fixation. None of the patients complained of pain worsening during the 6 months following implant removal. The percentage of canal compromise at the fractured level improved from a mean of 41.0% to 18.4% at 12 months after surgery. Mean kyphotic angle was improved significantly from $19.8^{\circ}$ before surgery to 7.8 at 12 months after screw fixation. Canal compromise and kyphotic angle improvements were maintained at 6 months after implant removal. No significant neurological deterioration or complications occurred after screw removal in any patient. Conclusion : Bone cement augmented short segment fixation using a percutaneous system can be an alternative to the traditional open technique for the management of selected thoracolumbar burst fractures accompanied by severe osteoporosis.

• Clinics in Shoulder and Elbow
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• v.13 no.2
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• pp.237-243
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• 2010

Purpose: In arthroscopic rotator cuff repair, the crucial step is secure fixation of Anchor to bone. However, osteoporosis of the tuberosity is frequently encountered in old patients, and can cause insecure fixation of anchors. The Aim of our study was to introduce a technique for anchor hole augmentation with bone cement when fixation failure of an anchor occurs, and to investigate the outcome. Materials and methods: Among 223 rotator cuff repairs performed between 2005 and 2009, anchor hole augmentation with polymethylmethacrylate was performed in 15 cases (all females; mean age of 65 years: range 49~77). Bone cement was injected into the anchor hole in a thick fluid state and the procedure was repeated to make a pot-like cement mantle. The anchor was inserted into the cement mantle while the cement hardened. The outcome was investigated, on average, at 16 months (6~32). Results: Radiographs showed cystic changes of the tuberosity. On follow-up radiographs and MRI, a change in the cement mantle was not noted. The final average UCLA score was 31 (28~35); 6 had excellent, 8 good and 1 fair results (p=0.008). Age-sex matched Constants score was 90 (74~98) (p=0.008). Conclusion: Anchor hole augmentation with bone cement is useful when fixation failure of an anchor is encountered due to bone atrophy. Anchor hole augmentation with bone cement does not negatively influence the outcome.

• Journal of Korean Neurosurgical Society
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• v.38 no.5
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• pp.350-354
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• 2005

Objective : The aim of this study is to assess the immediate and long-term efficacy of percutaneous vertebroplasty for treating painful vertebral osteoporotic fractures. Methods : A retrospective review of 149patients who had undergone 167 vertebroplasty procedures for osteoporotic fractures was performed. Clinical, radiologic, and procedural datas were analyzed as parameters of prognostic significance, including age, sex, bone marrow density score, symptom duration, bone cement filling grade, number of fractured vertebrae, compression grade of vertebrae, leakage of bone cement, volume of bone cement injected and complications. Results : In 158 of the 167 procedures assessed, immediate pain relief was obtained [94.6%]. The extent of collapse of the vertebral body was assessed as a parameter for prognostic significance [p=0.015]. Three months postoperatively, no improvement of the pain was observed in four of the 167 procedures that had undergone the vertebroplasty [2%]. At long-term follow-up, the improvement of pain was not correlated with the compression grade of vertebrae [p=0.420]. Conclusion : The immediate outcome of vertebroplasty are less effective in vertebrae more collapsed.

• The Journal of the Korean dental association
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• v.21 no.2 s.165
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• pp.167-172
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• 1983

This study was to investigate the effects of mynol cement on the periapical tissues of 40 molars in ten dogs. Root canal fillings were placed with mynol cement and the animals were killed at different post operative periods ranging from 1 to 5 weeks. The teeth examined on the basis of microscipic findings. The following results may be drawn; 1. 1 week after root canal fillings, the necrosis of cementum and dentin including alveolar bone was to be seen. There were severe inflammatory changes in the periodontal ligament. 2. 2 weeks after root canal fillings, edematous changes and fibrosis in the periodontal ligament were revealed. 3. After 3-4 weeks, fibrosis was more prominent than 2 weeks. 4. 5 weeks after root canal fillings, the osteoblastic activity was found abundantly surrounding the alveolar bone.

• Polymer(Korea)
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• v.29 no.4
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• pp.350-356
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• 2005

Poly(methyl methauylate)/montmorillonite nanocomposites were incorporated into acrylic bone cement in order to improve the mechanical properties and reduce the exotherm of acrylic bone cement. The nanocomposites were prepared using a suspension polymerization and characterized by scanning electron microscopy, X-ray diffraction, trans-mission electron microscopy, gel permeation chromatography, particle size analyzer and electron dispersive spectroscopy. The acrylic bone cements with poly (methyl methacrylate)/nanocomposite s were prepared and their thermal and mechanical properties were characterized. The prepared polymeric beads were composed of polymer-intercalated nanocomposites with partially exfoliated MMT layers, and the mean diameter of them was $50\~60$ fm with the spherical shape. The maximum setting temperature of the acrylic bone cements decreased from 98 to $81\~87^{circ}C$. The mechanical strengths and moduli of the acrylic bone cement with 0.1 $wt\%$ MMT were increased. compared to that without MMT. However, the mechanical properties were generally decreased with increasing incorporated MMT amounts. It is presumably due to the bubbles in nanocomposite beads generated during polymerization.

• Structural Engineering and Mechanics
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• v.89 no.5
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• pp.539-547
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• 2024

This study examines crack behavior within orthopedic cement utilized in total hip replacements through the finite element method. Its main goal is to compute stress intensity factors (SIF) near the crack tip. The analysis encompasses two load types, static and dynamic, applied to a crack starting from the interface between the cement and bone. Specifically, it investigates SIFs under mixed mode conditions during three activities: normal walking, climbing upstairs, and downstairs. The results highlight that a crack originating from a micro-interface under substantial loading can cause cement damage, leading to prosthetic loosening. Stress intensity factors in modes I, II, and III are influenced by the crack tip's orientation and location in the bone cement, with a 90° orientation yielding notably higher values across all three modes.

• The Journal of the Korean bone and joint tumor society
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• v.1 no.2
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• pp.145-153
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• 1995

Giant cell tumor is most frequently found in juxtaarticular region, and difficult to treat because of local recurrence. Although primary resections reduce recurrence, the joint function will be markedly impaired. Techniques involving physical adjuncts(high speed burr and electric cauterization), acrylic cement or en bloc resection with VFG(vascularized fibular graft) have been employed to reduce local recurrence. From October 1984 to April 1994, twenty-nine patients diagnosed as giant cell tumor were treated at department of Orthopaedic Surgery, School of Medicine, Kyung Hee University. There were eleven men and 18 women, ranging in age from 17 to 52 years(mean: 34 years). The average follow-up period was four years and five months. The location of the lesion was around the knee in 15, distal radius in three, femoral head in three, and others in eight patients. Fifteen patients around the knee joint were treated with several modalities; curettage with bone graft in five, curettage with cement filling in three, curettage with bone graft and physical adjuncts in five, en bloc resection with VFG in one and en bloc resection with arthroplasty in one patient. The functional results, according to the Marshall's knee score, were excellent in one, good in two, and fair in two after the curettage with bone graft, good in three after the curettage with bone cement filling, excellent in one, good in four after the curettage with bone graft and physical adjuncts, and good in two after the en bloc resection with VFG or arthroplasty. Three patients had local recurrence among 15 patients with giant cell tumor around knee. Vascularized fibular graft around wrist joint provided good functional restoration without local recurrence in all three patients who had giant cell tumor in distal radius. Although there is no statistical significance, it seems that curettage with bone graft using physical adjuncts or acrylic cement reveals better results than simple curettage with bone graft. Excellent functional result were obtained without local recurrence by using vascularized fibular graft after en bloc resection.