• The KIPS Transactions:PartB
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• v.10B no.5
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• pp.503-508
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• 2003

Since surgical treatment of the spine should overcome neurological compromises, the operative procedures need to be carefully planned and carried out with high degree of precision. Percutaneous vertebroplasty is a surgical procedure that was introduced for the treatment of compression fracture of the vertebrae. This procedure includes puncturing vertebrae and filling with polymethylmethacrylate (PMMA). Recent studies have shown that the procedure could provide structural reinforcement for the osteoporotic vertebrae while being minimally invasive and safe with immediate relief of pain. However, failures of treatment due to excessive PMMA volume injection have been reported as one of complications in vertebroplasty. It is believed that the control of PMMA volume is one of the most critical factors that can reduce the incidence of complications. Therefore, clinical success of vertebroplasty can be dependent on the volume of PMMA injection for a given patient. In this study, the optimal volume of PMMA injection for vertebroplasty was predicted based on the image analysis of a given patient.

• The Journal of Advanced Prosthodontics
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• v.7 no.2
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• pp.93-97
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• 2015

PURPOSE. Xerostomia can diminish the quality of life, leads to changes in normal chemical composition of saliva and oral microbiata, and increases the risk for opportunistic infections, such as Candida albicans. Various artificial salivas have been considered for patients with xerostomia. However, the knowledge on the antifungal and antiadhesive activity of artificial saliva substitutes is limited. The aim of the present study was to evaluate influence of two artificial salivas on the adhesion of Candida albicans to the polymethylmethacrylate disc specimens. MATERIALS AND METHODS. Two commercial artificial salivas (Saliva Orthana and Biotene Oral Balance Gel) were selected. 45 polymethylmethacrylate disc specimens were prepared and randomly allocated into 3 groups; Saliva Orthana, Biotene-Oral Balance gel and distilled water. Specimens were stored in the artificial saliva or in the sterile distilled water for 60 minutes at $37^{\circ}C$. Then they were exposed to yeast suspensions including Candida albicans. Yeast cells were counted using ${\times}40$ magnification under a light microscope and data were analysed. RESULTS. Analysis of data indicated statistically significant difference in adhesion of Candida albicans among all experimental groups (P=.000). Findings indicated that Saliva Orthana had higher adhesion scores than the Biotene Oral Balance gel and distilled water (P<.05). CONCLUSION. In comparison of Saliva Orthana, the use of Biotene Oral Balance Gel including lysozyme, lactoferrin and peroxidase may be an appropriate treatment method to prevent of adhesion of Candida albicans and related infections in patients with xerostomia.

• Journal of the Korean Chemical Society
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• v.39 no.11
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• pp.848-855
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• 1995

The influence of gravitational effect on the retention behaviors of polystyrene (PS) and polymethylmethacrylate (PMMA) in flat type thermal field flow fractionation (Thermal FFF) was studied. In the case of downward flow of mobile phase, the gravitational effect acting in the same direction of mobile phase flow increases as the angle of the system from the horizontal line (0˚to 60˚) increases. The decreasement of retention time of PS & PMMA was found. Also, the increasement of dimensionless λ values was found. And the difference in the retention time of PS & PMMA having different molecular weight decreases and also the resolution decreases. In the case of upward flow of mobile phase, the gravitational effect acting in the opposite direction of mobile phase flow increases as the angle of the system from the horizontal line (0˚to 60˚) increases. The increasement of retention time of PS & PMMA was found. Also, the decreasement of dimensionless λ values was found. And the difference in the retention time of PS & PMMA having different molecular weight increases and also the resolution increases.

• Korean Chemical Engineering Research
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• v.56 no.2
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• pp.162-168
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• 2018

UV-curable hard coating solutions were prepared by mixing organic or inorganic polysilazane with urethane acrylate. UV-cured hard coating films were also obtained by flow coating, subsequently UV-curing on polymethylmethacrylate (PMMA) sheets. The effect of types and amounts of polysilazane was investigated on properties of obtained coating films. As a result, the coatings obtained by using organic polysilazane showed a high hydrophobic property with water contact angle of $95^{\circ}$, pencil hardness of 7H and high transparency of 92% in the visible wavelength range. On the other hand, the PMMA sheets made by using inorganic polysilazane exhibited a pencil hardness of as high as 8H, good adhesion to the substrate and water contact angle of $82^{\circ}$.

• Journal of Korean Neurosurgical Society
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• v.29 no.3
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• pp.365-371
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• 2000

Objectives : To describe a technique for percutaneous vertebroplasty of osteoporotic vertebral body compression fractures and to report preliminary results of its use. Methods : The technique was used over a 8-month period in 9 patients with 10 painful vertebral fractures. The technique involves percutaneous puncture of the involved vertebrae with a Jamshidi needle via a transpedicular approach followed by injection of polymethylmethacrylate(PMMA) into the vertebral body. Results : The procedure was technically successful in all patients, with an average injection amount of 5.9 cc per vertebral body. One patient complained of flank pain postoperatively in spite of improvement in back pain caused by the fractured vertebra. Remaining eight patients reported significant pain relief early after treatment. The patients were followed up for 3 to 15 months(average 7.2 months) and demonstrated no recurrence of pain or aggravation of deformity. Conclusion : Vertebroplasty appears to be a valuable tool in the treatment of painful osteoporotic vertebral fractures, providing acute pain relief and early mobilization in appropriate patients. However, it needs to have more extensive prospective clinical study to confirm its definitive role in the management of this condition.

• The korean journal of orthodontics
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• v.49 no.6
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• pp.404-412
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• 2019

Objective: To assess shear bond strength and failure mode (Adhesive Remnant Index, ARI) of orthodontic brackets bonded to polymethylmethacrylate (PMMA) blocks for computer-aided design/manufacture (CAD/CAM) fabrication of temporary restorations, following substrate chemical or mechanical treatment. Methods: Two types of PMMA blocks were tested: $CAD-Temp^{(R)}$ (VITA) and $Telio^{(R)}$ CAD (Ivoclar-Vivadent). The substrate was roughened with 320-grit sandpaper, simulating a fine-grit diamond bur. Two universal adhesives, Scotchbond Universal Adhesive (SU) and Assure Plus (AP), and a conventional adhesive, Transbond XT Primer (XTP; control), were used in combination with Transbond XT Paste to bond the brackets. Six experimental groups were formed: (1) $CAD-Temp^{(R)}/SU$; (2) $CAD-Temp^{(R)}/AP$; (3) $CAD-Temp^{(R)}/XTP$; (4) $Telio^{(R)}$ CAD/SU; (5) $Telio^{(R)}$ CAD/AP; (6) $Telio^{(R)}$ CAD/XTP. Shear bond strength and ARI were assessed. On 1 extra block for each PMMA-based material surfaces were roughened with 180-grit sandpaper, simulating a normal/medium-grit ($100{\mu}m$) diamond bur, and brackets were bonded. Shear bond strengths and ARI scores were compared with those of groups 3, 6. Results: On $CAD-Temp^{(R)}$ significantly higher bracket bond strengths than on $Telio^{(R)}$ CAD were recorded. With XTP significantly lower levels of adhesion were reached than using SU or AP. Roughening with a coarser bur resulted in a significant increase in adhesion. Conclusions: Bracket bonding to CAD/CAM PMMA can be promoted by grinding the substrate with a normal/medium-grit bur or by coating the intact surface with universal adhesives. With appropriate pretreatments, bracket adhesion to CAD/CAM PMMA temporary restorations can be enhanced to clinically satisfactory levels.

• Journal of the Korean Society of Radiology
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• v.13 no.5
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• pp.773-778
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• 2019

Images using X-rays are essential to diagnosis, but noise is inevitable in the image. To compensate for this, a total variation (TV) algorithm was presented to reduce the patient's exposure dose while increasing the quality of the images. The purpose of this study is to verify the effect on the image quality in radiographic imaging according to the thickness of the additional filtration plate through simulation, and to evaluate the usefulness of the TV algorithm. By using the Geant4 Application for Tomographic Emissions (GATE) simulation image, the actual size, shape and material of the Polymethylmethacrylate (PMMA) phantom were identical, the contrast to noise ratio (CNR) and coefficient of variation (COV) were compared. The results showed that the CNR value was the highest and the COV the lowest when applying the TV algorithm. In addition, we can acquire superior CNR and COV results with 0 mm Al in all algorithm cases.

• Korean Journal of Materials Research
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• v.30 no.12
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• pp.650-654
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• 2020

A combination of Polycarbonate (PC) material and Polymethylmethacrylate (PMMA), fabricated using an injection molding machine, has been investigated to determine its advantages, as studied in Ref. 1). This paper aims to investigate the optimization of PMMA/PC blend for both tensile yield strength and impact strength. Furthermore, interaction effects of process conditions on mechanical properties including tensile yield strength and impact strength of PMMA/PC blend by injection molding process are interpreted in this study. Tensile and impact specimens are designed following ASTM, type V, and are fabricated by injection molding process. The processing conditions such as melt temperature, mold temperature, packing pressure, and cooling time are applied; each factor has three levels. As a result, in comparison with optimization of separated responses, mechanical properties of PMMA/PC are found to decrease when optimizing both tensile and impact strengths simultaneously. The melt temperature is found to be the most significant interaction parameter with the mold temperature and packing pressure. In addition, there is more interaction between the mold temperature and cooling time. This investigation provides a useful understanding of the control of injection molding processing of polymer blends in optical application.

• Journal of the Korean Orthopaedic Association
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• v.54 no.4
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• pp.327-335
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• 2019

Purpose: To investigate the radiological efficacy of polymethylmethacrylate (PMMA) augmentation of pedicle screw operation in osteoporotic vertebral compression fractures (OVCF) patients. Materials and Methods: Twenty OVCF patients, who underwent only posterior fusion using pedicle screws with PMMA augmentation, were included in the study. The mean follow-up period was 15.6 months. The demographic data, bone mineral density (BMD), fusion segments, number of pedicle screws, and amount of PMMA were reviewed as medical records. To analyze the radiological outcomes, the radiologic parameters were measured as the time serial follow-up (preoperation, immediately postoperation, postoperation 6 weeks, 3, 6 months, and 1 year follow-up). Results: A total of 20 patients were examined (16 females [80.0%]; mean age, 69.1±8.9 years). The average BMD was -2.5±0.9 g/cm². The average cement volume per vertebral body was 6.3 ml. The mean preoperative Cobb angle of focal kyphosis was 32.7°±7.0° and was improved significantly to 8.7°±6.9° postoperatively (p<0.001), with maintenance of the correction at the serial follow-up, postoperatively. The Cobb angle of instrumented kyphosis, wedge angle, and sagittal index showed similar patterns. In addition, the anterior part of fractured vertebral body height averaged 11.0±5.0 mm and was improved to 18.5±5.7 mm postoperatively (p=0.006), with maintenance of the improvement at the 3-month, 6-month, and 1-year follow-up. Conclusion: The reinforcement of pedicle screws using PMMA augmentation may be a feasible surgical technique for OVCF. Moreover, it appears to be appropriate for improving the focal thoracolumbar/lumbar kyphosis and is maintained well after surgery.

• Biomaterials and Biomechanics in Bioengineering
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• v.2 no.4
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• pp.197-206
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• 2015

This paper presents three-dimensional finite element method analyses of the distribution of equivalents stress of Von Mises. Induced around a cavity located in the bone cement polymethylmethacrylate (PMMA). The presences and effect of its position in the cement was demonstrated, thus on the stress level and distribution. The porosity interaction depending on their positions, and their orientations on the interdistances their mechanical behaviour of bone cement effects were analysed. The obtained results show that micro-porosity located in the proximal and distal zone of the prosthesis is subject to higher stress field. We show that the breaking strain of the cement is largely taken when the cement, containing the porosities very close adjacent to each other.