Temat: 87.85.J- - Prolib Integro

Skocz do pozycji: 1.

Tytuł:: Surface Texturing of Vitamin E Blended UHMWPE for Reduction of Wear
Autorzy:: Sagbas, B.
Durakbasa, M.
Tematy:: 87.85.J-; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1182858.pdf Link otwiera się w nowym oknie
Opis:: Ultra high molecular weight polyethylene (UHMWPE) has been the most commonly used bearing material in artificial hip and knee replacements. But wear and wear debris of UHMWPE has been the most important problem which cause aseptic loosening and revision surgery of these replacements. For enhangement of wear resistance, new generation UHMWPE materials have been developed and different surface modification techniques have been tried. The objective of this study is to determine the effect of surface dimples on wear behavior of conventional UHMWPE and vitamin E blended UHMWPE (VE-UHMWPE) in ultra-pure water lubrication conditions. Pin-on-disc tribotester was used for measurement of friction coefficient and wear. 0.5 mm in diameter dimples were machined on the surfaces of UHMWPE and VE-UHMWPE discs. CoCrMo pins were used as counter surface. Results were evaluated in terms of materials and presence of dimples.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 2.

Tytuł:: Effect of Precipitation Method on Properties of Hydroxyapatite Powders
Autorzy:: Hazar Yoruç, A.
Karakaş, A.
Ayas, E.
Koyun, A.
Tematy:: 87.85.J-; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1399899.pdf Link otwiera się w nowym oknie
Opis:: The aim of this study was the compare the properties of hydroxyapatite as a function of two different methods (chemical and biomimetic precipitation). Powder products were called as chemical hydroxyapatite for chemical method and biomimetic hydroxyapatite for biomimetic method. Precipitated powders with both methods were characterized by Fourier transform infrared, X-ray diffraction, X-ray fluorescence and measurements of hardness and density. Chemical analysis results showed that dried-biomimetic hydroxyapatite sample consists of hydroxyapatite $[Ca_{10}PO_4)_6(OH)_2]$ as main phase and beta-tricalcium phosphate (β-TCP) as secondary phase and dried-chemical hydroxyapatite sample also includes pure hydroxyapatite phase. Chemical hydroxyapatite and biomimetic hydroxyapatite powders were sintered using by spark plasma sintering method. Vickers hardness values of sintered disk samples were measured. Furthermore chemical structure of the final products was analyzed. Also density values of chemical hydroxyapatite and biomimetic hydroxyapatite disks were measured. Finally it is concluded that different precipitation methods affect hydroxyapatite properties and this can be an advantage for biomedical applications.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 3.

Tytuł:: Effect of Different Phosphorus Precursors on Biomimetic Hydroxyapatite Powder Properties
Autorzy:: Karakaş, A.
Hazar Yoruç, A.
Gökçe, H.
Karabulut, A.
Ceylan Erdoğan, D.
Tematy:: 87.85.J-; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1399963.pdf Link otwiera się w nowym oknie
Opis:: Hydroxyapatite is the main component of natural hard tissues, such as teeth and bone. It has been studied extensively as a candidate biomaterial for its use in prosthetic applications. Hydroxyapatite was formulated as $Ca_{10}(PO_4)_6(OH)_2$ and it has a high stability under physiological conditions. Also hydroxyapatite can be synthesized using different calcium and phosphorus precursors. In this study, biomimetic hydroxyapatite powder has been synthesized simulating physiological conditions. Synthetic body fluids which have the same composition as human blood plasma instead of pure water were used as precipitation media to obtain biological conditions. Recent research involved the effect of different Ca-precursors however aim of this study is to determine the effect of phosphorus resources. In this study, the synthesis of hydroxyapatite powder is carried out by using biomimetic method in synthetic body fluids. Calcium acetate $[Ca(CH_3COO)_2, CA]$ and diammonium hydrogen phosphate $[(NH_4)_2HPO_4, DAHP]$, ammonium dihydrogen phosphate $[NH_4H_2PO_4, ADHP]$, dipotassium hydrogen phosphate $[K_2HPO_4, DPHP]$ and orthophosphoric acid $[H_3PO_4, OPA]$ were used as Ca- and P-precursors. Chemical structures of synthesized powders have been examined by Fourier transform infrared and X-ray diffraction. Results showed that synthesized powders have a pure hydroxyapatite structure. However, ADHP precursors have an unfavorable effect on sintered hydroxyapatite powders. Using ADHP phase transition was caused in pure hydroxyapatite structure and apatite and whitlockite were observed as secondary phases. Their particle size, surface area determination and morphological structures have been characterized by Zeta-Sizer, biomimetic hydroxyapatite the Brunauer-Emmett-Teller analysis and scanning electron microscopy images, respectively. As a result different starting materials have affected the structure, particle size and morphological properties of biomimetic hydroxyapatite.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 4.

Tytuł:: Sonochemical Synthesis of Hydroxyapatite Nanoparticles with Different Precursor Reagents
Autorzy:: Hazar Yoruç, A.
İpek, Y.
Tematy:: 87.85.J-; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1491376.pdf Link otwiera się w nowym oknie
Opis:: Different precursor chemicals ($3Ca(OH)_2,$ $Ca(NO_3)_2$ and $CaO$ as $Ca^{2+}$ sources, $H_3PO_4$ and $(NH_4)_2HPO_4$ as $PO_4^{3-}$ sources were used to synthesis of nanosized hydroxyapatite powder with ultrasonic precipitation method. The effect of different chemical precursors was investigated. Sample characterization was achieved by powder X-ray diffraction, the Fourier transformed infrared transmission spectroscopy, zeta sizer, scanning electron microscopy, density and surface area measurements.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 5.

Tytuł:: Comparison of Properties of Hydroxyapatite Powders Synthesized by Chemical and Biomimetic Techniques
Autorzy:: Hazar Yoruç, A.
Karakaş, A.
Koyun, A.
Yildiz, T.
Tematy:: 87.85.J-; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1491408.pdf Link otwiera się w nowym oknie
Opis:: Hydroxyapatite $[HA; Ca_{10}(PO_4)_6(OH)_2]$ which composes inorganic phase of bones and teeth is one of the biomedical materials for artificial bone, reconstruction of broken or disordered bones, coating of metallic biomedical materials and dental surgery with its great biocompatibility. In this study, HA powders were synthesized from aqueous suspensions containing $H_3PO_4$ and $Ca(OH)_2$ with 1.67 Ca/P ratios (chemical HA, CHA) and second process is carried out in simulated body fluids consisting of $(NH_4)_2HPO_4$ and $Ca(NO_3)_2 \cdot 4H_2O$ as biomimetic hydroxyapatite (BHA). Moreover, properties of bovine HA (BoHA) and commercial HA (CoHA) were compared with properties of synthesized HA powders. Chemical structures of synthesized powders have been examined by the Fourier transform infrared technique and X-ray diffraction. The results showed that BHA powders have a pure HA content and no secondary phase, CHA also has monetite phase as secondary phase with HA in its structure. Particle size analysis was carried out with laser particle sizer and zeta-sizer, surface area of powders has been analyzed by the Brunauer-Emmett-Teller technique. Powder morphology is determined using scanning electron microscopy. As a result two different synthesis methods affected properties of HA powders.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 6.

Tytuł:: Comparison of Microstructural and Mechanical Properties of Hydroxyapatite-Al₂O₃ Composites with Commercial Inert Glass (CIG) Addition
Autorzy:: Bulut, B.
Demirkol, N.
Erkmen, Z.
Kayali, E.
Tematy:: 87.85.J; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1401291.pdf Link otwiera się w nowym oknie
Opis:: Hydroxyapatite (HA) is one of the most widely used biomaterials for orthopedic and dental applications. However, HA is a brittle and weak material and this constrains its orthopedic applications. There are several methods for the improvement of mechanical properties of the HA. One of these methods is to strengthen the HA material by a secondary phase (i.e polymer, metal or ceramics), to make a stronger composite material. Alumina (Al₂O₃) is a bioinert material, which has been widely investigated as a reinforcing agent for HA. The aim of this study is to compare the microstructural and mechanical properties of HA-Al₂O₃ composites with the addition of 5 and 10 wt.% of commercial inert glass (CIG). The grain samples were produced according to BS 7253 at 350 MPa. Then, they were sintered at temperatures between 1000-1300°C for 4 hours. The samples were also analyzed by SEM + EDS to determine microstructural properties, phase analysis was done by X-ray diffractometer (XRD), mechanical properties were measured by compression and hardness tests. Results show that HA-Al₂O₃ composites with addition of 5 and 10 wt.% CIG have reached high density values and high mechanical properties, such as compression strength and hardness at 1300°C. The compression strength and hardness of composites has increased with the increasing CIG content.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 7.

Tytuł:: An in Vitro Comparison of the Enamel Remineralisation Potential of Bioactive Glass, Hydroxyapatite and CPP-ACP
Autorzy:: Güçlü, Z.
Gjorgievska, E.
Coleman, N.
Tematy:: 87.85.J-; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1033584.pdf Link otwiera się w nowym oknie
Opis:: The objective of this research was to investigate the comparative in vitro enamel remineralisation potential of commercial toothpastes containing bioactive glass (BG) particles, hydroxyapatite (HAP) particles or casein phosphopeptide - amorphous calcium phosphate (CPP-ACP) nanocomplexes. Eighteen extracted permanent teeth were coated with varnish leaving a window on the buccal surface and placed in demineralising solution for 24 h to create artificial caries-like white spot lesions (WSLs). The teeth were randomly assigned to six groups and sectioned longitudinally through the WSLs. The roots were removed and the teeth were re-varnished, leaving the WSLs exposed. Groups A, B and C were subjected to an optimum remineralisation protocol in which the "control" half of each tooth was incubated in artificial saliva for 24 h at 37°C and the "treatment" half of each corresponding tooth was cyclically exposed to artificial saliva and to 1:2 toothpaste solution containing either BG, HAP or CPP-CAP, respectively. Groups D, E and F were subjected to an acid-challenge remineralisation protocol which was similar to that of Groups A, B and C but which also incorporated cyclic exposure to demineralising solution. Scanning electron microscopy and energy dispersive X-ray analysis were used to compare the remineralisation of the surface and depth of the control and treatment WSLs. Under optimum conditions BG and CPP-ACP provided sub-surface repair by diffusion of calcium and phosphate ions into the WSLs. HAP did not influence remineralisation under neutral pH conditions. Conversely, under acid-challenge conditions, HAP was able to dissolve to release calcium and phosphate ions which diffused in to the WSLs and also protected the enamel surface from further erosion. BG and CPP-ACP both coated the enamel surface under acidic conditions, although their ability to remineralise the body of the lesion was compromised at low pH.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 8.

Tytuł:: Biological Evaluation of Anodized Biodegradable Magnesium-Calcium Alloys
Autorzy:: Kim, J.
Lee, J.
Lee, K.
Park, S.
Lim, H.
Park, C.
Bae, J.
Yun, K.
Tematy:: 87.85.jj
87.85.J-; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1398763.pdf Link otwiera się w nowym oknie
Opis:: The objective of this study was to evaluate the biocompatibility of studied binary magnesium-calcium (Mg-Ca) alloys for biodegradable intraosseous implants. Mg is necessary for health and is a non-toxic biodegradable material that decomposes naturally in the body. Nevertheless, Mg has been implicated in problems including diminished physical properties and corrosion resistance when degradation is too rapid prior to bone healing. This study has explored the effect of Ca on the corrosion resistance and biological evaluation after anodizing treatment with different contents of Ca alloy. Binary Mg-0.5Ca, Mg-1Ca and Mg-5Ca alloys were prepared by the casting method under an argon atmosphere and cut into disc-shaped pieces. Pure Mg alloy was used as the control. Anodic oxidation was performed for 15 minutes at a voltage of 120 V using an electrolyte solution containing Ca gluconate, sodium hexametaphosphate, and sodium hydroxide at room temperature. Corrosion resistance was analyzed using a corrosion tester. After a hydrogen evolution test, the surface pattern and phase changes were observed on a scanning electron microscop (SEM) and energy dispersive spectroscop (EDS). Microscopic evaluation of the adhesion and cell biological functions of Mg was conducted by observing the response of human fetal osteoblastic 1.19 cells with regard to changes in surface film properties, depending on the amount of Ca. Our results support the view that in Mg-xCa alloys (x=0.5, 1, 5 wt.%) treated using anodic oxidation, the increasing Ca content controls the rate of decomposition and improves corrosion resistance.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 9.

Tytuł:: Bioactivity Properties and Characterization of Commercial Synthetic Hydroxyapatite - 5 wt.% Niobium (V) Oxide - 5 wt.% Magnesium Oxide Composite
Autorzy:: Demirkol, N.
Tematy:: 87.85.J-; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1031119.pdf Link otwiera się w nowym oknie
Opis:: Hydroxyapatite is widely used for bone grafts due to its chemical and structural similarities to the mineral phase of hard tissues and due to its bioactivity and biocompatibility. However, hydroxyapatite has poor mechanical properties due to its brittleness. To improve mechanical properties of hydroxyapatite-ceramics, ceramic oxides, whiskers or fibers have been suggested. In this study, commercial synthetic hydroxyapatite composite reinforced with 5 wt.% Nb₂O₅ and 5 wt.% MgO was characterized. Microstructural properties of all samples sintered at different temperatures were characterized using scanning electron microscopy technique. Phase analysis was carried out using X-ray diffraction technique. Mechanical properties were measured by compression and hardness tests. The bioactivity property was determined by in vitro bioactivity test. The best obtained values of density, compression strength and Vickers Microhardness were 3.01 g/cm³, 96 MPa and 393 HV, for composite sintered at 1300°C for 4 hours. Bioactivity results for composite, sintered at 1300°C, show that apatite formation has started after two weeks in a simulated body fluid. At the end of the fourth week, the dense apatite layer and clusters were observed on the surface of the composite.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 10.

Tytuł:: Investigating Effects of Testing Parameters on Frictional Heating of UHMWPE by Taguchi Method
Autorzy:: Sagbas, B.
Durakbasa, M.
Tematy:: 87.85.J-; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1195287.pdf Link otwiera się w nowym oknie
Opis:: Frictional heating makes detrimental effects on surrounding tissue and lubricant around the artificial hip joint. For reduction of this thermal damage, testing parameters and their effects were investigated by using the Taguchi method and analysis of variance. Ultra high molecular weight polyethylene (UHMWPE) acetabular liners and CoCrMo femoral head artificial hip joint components were used as samples. Frictional heating measurements of the joints were carried out on a custom made hip joint friction experimental setup. Surface dimples in different sizes were machined on the inner surface of acetabular insert samples. The tests were conducted under different loading conditions with different testing time. Bovine calf serum was used as lubricant with different amount of third body wear particles in it. Temperature rise in acetabular and femoral component was recorded with embedded thermocouples. The experimental results demonstrated that the surface dimples were the major parameter on frictional heating, followed by applied load, amount of third body particles and time. The optimal combination of the testing parameters was predicted and validated by doing experiments.
Dostawca treści:: Biblioteka Nauki

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