Person: OKTAR, FAİK NÜZHET
Loading...
Email Address
Birth Date
Research Projects
Organizational Units
Job Title
Last Name
OKTAR
First Name
FAİK NÜZHET
Name
16 results
Search Results
Now showing 1 - 10 of 16
Publication Metadata only Hydroxyapatite-TiO2 composites(ELSEVIER SCIENCE BV, 2006) OKTAR, FAİK NÜZHET; Oktar, FNThis article reports the mechanical properties, the microstructure, and the crystallography of composite materials made of hydroxyapatite, obtained from natural bovine bone, and TiO2 (5 and 10 wt.%), which were sintered at different temperatures between 1000 and 1300 degrees C. Higher sintering temperatures resulted in better densification. The samples sintered at 1300 degrees C had the highest microhardness. The best compressive strengths were obtained after sintering at 1300 degrees C for the samples containing 5% TiO2, and at 1200 degrees C for the samples with 10% TiO2. (c) 2005 Elsevier B.V. All rights reserved.Publication Metadata only Hydroxyapatite nano-powders produced hydrothermally from nacreous material(ELSEVIER SCI LTD, 2006) OKTAR, FAİK NÜZHET; Lemos, A. F.; Rocha, J. H. G.; Quaresma, S. S. F.; Kannan, S.; Oktar, F. N.; Agathopoulos, S.; Ferreira, J. M. F.Nano-powders of pure AB-type carbonated hydroxyapatite (HA) sized of similar to 100 nm were successfully produced via hydrothermal transformation (HT) of milled oyster shell powders at 200 degrees C. Low production cost, worldwide availability and natural-biological origin of raw materials are important features of the investigated process. When fine shell powders were used, the transformation reaction from aragonite to hydroxyapatite was accomplished within about 24 h. Calcite, concentrated at the outer surface of the shells, was less prone to transform into hydroxyapatite under the investigated hydrothermal conditions, even after prolonged reaction time (72 h) or in highly concentrated phosphate solutions. (c) 2006 Elsevier Ltd. All rights reserved.Publication Metadata only Sintering effect on mechanical properties of composites of bovine hydroxyapatite (BHA) and Li2O(Trans Tech Publications Ltd, 2006) OKTAR, FAİK NÜZHET; Oktar F.N., Demirer M.R., Gunduz O., Genc Y., Agathopoulos S., Peker I., Ozyegin L.S., Salman S.In this study, hydroxyapatite (HA) material, obtained from calcinated bovine bone (BHA), was mixed with 0.25, 0.50, 1.00, and 2.00 wt% Li 2CO3. The pressed pellets were sintered at various sintering temperatures between 900°C and 1300°C. Measurements of compression strength, microhardness, and density, along with SEM observation and X-ray diffraction analysis were performed. The experimental results showed that the samples with 0.25 and 0.50% Li2CO3. reached a maximum of densification and the highest values of compression strength and microhardness were achieved after sintering at 1300°C. The wetting effect of a Li2O-associated glassy phase was observed even from 900°C.Publication Metadata only Effect of yttria-doping on mechanical properties of bovine hydroxyapatite (BHA)(SAGE PUBLICATIONS LTD, 2008) OKTAR, FAİK NÜZHET; Gunduz, O.; Daglilar, S.; Salman, S.; Ekren, N.; Agathopoulos, S.; Oktar, F. N.Sintered bodies of hydroxyapatite, derived from calcinated bovine bone (BHA) and doped with 0.5 and 1wt% Y2O3, were prepared. Measurements of density, compression strength, and microhardness, along with scanning electron microscopy (SEM) and X-ray diffraction (XRD) were carried out. The experimental results showed that BHA doping with yttria favors formation of glassy phase, which advances sintering and results in a dense and reinforced BHA matrix. The best mechanical properties were achieved after sintering at 1200 degrees C for compressive strength (82 MPa) and 1300 degrees C for microhardness (672 HV). These results are better than pure BHA or composites of hydroxyapatite with Y2O3-stablized zirconia, qualifying yttria (as dopant of BHA) for further in vitro and in vivo experimentation.Publication Metadata only Microstructural and mechanical properties of hydroxyapatite-zirconia composites(WILEY, 2007) OKTAR, FAİK NÜZHET; Erkmen, Z. E.; Genc, Y.; Oktar, F. N.This work focuses on the improvement of the mechanical properties of hydroxyapatite (HA) through the addition of 3 mol% yttria partially stabilized zirconia (PSZ). Enamel-derived HA (EHA) from freshly extracted human teeth and commercial HA (CHA) were chosen as the matrix. The effects of addition up to 10 wt% of PSZ and of sintering temperature (1000 degrees-1300 degrees C) on the density, microhardness, and compression strength were evaluated. For EHA-PSZ composites, the density and mechanical properties were generally enhanced by adding 5 wt% PSZ, especially after sintering at 1200 degrees C, whereas CHA-PSZ composites showed lower strength values at sintering temperatures of 1200 degrees and 1300 degrees C with respect to EHA-PSZ composites. This may be due to the lower stability of CHA-PSZ composites with higher amounts of calcium zirconate formed over 1100 degrees C when compared with EHA-PSZ composites.Publication Metadata only Microstructure and mechanical properties of sintered enamel hydroxyapatite(ELSEVIER SCI LTD, 2007) OKTAR, FAİK NÜZHET; Oktar, F. N.The influence of sintering temperature on the microstructure and the mechanical properties (i.e. compressive strength and microhardness) of samples of calcinated human enamel was investigated. The experimental results indicate a low densification regime after sintering at low temperatures (1000 degrees C, 1100 degrees C) and a high densification regime after sintering at higher temperatures (1200 degrees C, 1300 degrees C). With respect to earlier studies, high mechanical properties were achieved. The enhancement of mechanical properties was attributed to the presence of fluorine traces in enamel. (c) 2006 Elsevier Ltd and Techna Group S.r.l. All rights reserved.Publication Metadata only Biological activities of bioceramic powders of various natural biological origins(ELSEVIER SCIENCE BV, 2009-09) TOKSOY ÖNER, EBRU; Tuyel, A. U.; Valerio, P.; Oner, E. Toksoy; Oktar, F. N.Publication Metadata only Histomorphometric evaluation of implants coated with enamel or dentine derived fluoride-substituted apatite(SPRINGER, 2008) OKTAR, FAİK NÜZHET; Kurkcu, Mehmet; Benlidayi, Mehmet Erme; Ozsoy, Serhat; Ozyegin, Luetfiye Sevgi; Oktar, Faik Nuzhet; Kurtoglu, CemObjectives The aim of this study was to compare osseous healing characteristics of titanium implants coated with enamel-derived fluoride-substituted apatite (EFSA) or dentin-derived fluoride-substituted apatite (DFSA). Methods Fluoride-substituted apatite was derived from extracted human teeth with calcination method at 850 degrees C. DFSA and EFSA were separated and carefully ground with a blade grinder. Twenty-four titanium implants were prepared from a 99.99% pure titanium bar. EFSA and DFSA powders were sprayed separately on implants. As control group, unsprayed and sandblasted pure titanium implants were used. Eight adult rams were used in the study. One EFSA coated, 1 DFSA coated and 1 control implants were placed into right tibia of each rams. The rams were sacrificed after 6 months of healing. Undecalcified sections were prepared according to Donath's method and histomorphometric evaluation of implants was made. Results The mean bone contact percentage of DFSA-coated, EFSA-coated and control implants was 89.88% +/- 2.34, 70.19% +/- 13.11 and 53.12% +/- 5.76 respectively. This study suggests that DFSA-coated implants achieved better bone contact than EFSA-coated implants (P < 0.05). Also study groups presented better bone contact than control group (P < 0.05). Conclusions The results of this study show that although DFSA-coated implants achieved better bone contact, both DFSA and EFSA can be considered as appropriate coating materials.Publication Metadata only Sintering effect on mechanical properties of composites of natural hydroxyapatites and titanium(ELSEVIER SCI LTD, 2009) OKTAR, FAİK NÜZHET; Salman, S.; Gunduz, O.; Yilmaz, S.; Ovecoglu, M. L.; Snyder, Robert L.; Agathopoulos, S.; Oktar, F. N.This study presents the fabrication and characterization of composite materials of hydroxyapatite and Ti. Hydroxyapatite (HA) powder was obtained from bovine bones (BHA) and human enamel (EHA) via calcination technique. Fine powders of HA were admixed with 5 and 10 wt.% fine powder of metallic Ti. Powder-compacts were sintered at different temperatures between 1000 and 1300 degrees C. Compression strength, Vickers microhardness and elastic modulus as well as density were measured. SEM and X-ray diffraction studies were also conducted. The experimental results showed that addition of Ti to EHA and BHA decreases the elastic modulus, comparing to samples of pure BHA. The best mechanical properties for BHA-Ti composites were obtained after sintering in the range of 1200-1300 degrees C and for EHA-Ti composites in the range of 1100-1300 degrees C. (C) 2009 Elsevier Ltd and Techna Group S.r.l. All rights reserved.Publication Metadata only Sintering effect on mechanical properties of composites of enamel derived hydroxyapatite (EHA) and titanium(Trans Tech Publications Ltd, 2006-05-15) OKTAR, FAİK NÜZHET; Gunduz O., Oktar F.N., Oz B., Altundal H., Agathopoulos S., Salman S., Ovecoglu L.Hydroxyapatite (HA) is one of the most promising biomaterials, which is on use since decades in biomedicine. Because of the known mechanical weakness of HA in load carrying situations, various dopants, like ceramic oxides and metallic particles, have been used to produce HA-composite materials. In this study, Ti powders were admixed with enamel derived HA at 5 and 10 wt %. After ball milling, the mixtures were uniaxially pressed into pellets of a cylindrical form. The composites were sintered at temperatures between 1000°C and 1300°C. Microhardness, compression strength, and density measurements together with X-ray diffraction analysis and SEM studies were performed. The best mechanical values were obtained for the samples sintered between 1100°C and 1300°C.