Browsing by Author "Aksakal, Bunyamin"

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Biomechanical Effects of Menopause in Ovariectomized Rats' Femurs
(informa Healthcare, 2014) Okyay, Ayse Guler; Kavak, Servet; Turktas, Ugur; Alkis, Ismet; Guner, Savas; Aksakal, Bunyamin
Objective: To demonstrate the biomechanical changes in rat bones occurred by surgical menopause and to search for correlation between biomechanical test results and bone mineral density (BMD) measurements. Methods: Thirty female Wistar-albino rats aged 6 months and weighed 250-300 g were randomized into ovariectomy, sham and control groups. After 6 months, rats were sacrificed and right femurs were extracted. BMD measurements and three point bending biomechanical tests were made in femurs. Results: The difference among the mean BMD measurements of three groups were found to be statistically significant (Pr>F value <0.0001). Mean elastic module, maximum elongation and femoral diameters were also found to be statistically significantly different (Pr>F value <0.05). Ovariectomised and sham-operated groups were significantly different in terms of elastic modulus. Ultimate force did not differ among the groups significantly. The difference between ultimate strain and maximum elongation of the ovariectomy and sham operated group was statistically significant. Conclusions: Bone quality was deteriorated and fragility was increased in rats 6 months after surgical menopause. Sole BMD measurement might not be reliable in evaluation of osteoporosis and fracture risk. Biomechanical quality of bone is more important than its mineral content in determining fragility.
Biomechanical Effects of Menopause in Ovariectomized Rats' Femurs (Vol 30, Pg 62, 2014)
(informa Healthcare, 2014) Okyay, Ayse Guler; Kavak, Servet; Turktas, Ugur; Alkis, Ismet; Guner, Savas; Aksakal, Bunyamin
Effect of Hydroxyapatite/Sio2 Hybride Coatings on Surface Morphology and Corrosion Resistance of Rex-734 Alloy
(Elsevier Sci Ltd, 2016) Say, Yakup; Aksakal, Bunyamin; Dikici, Burak
REX-734 stainless steel alloy was coated with hydroxyapatite (HA)-silicon dioxide (SiO2) composite (hybride) coatings by using the sol-gel method. Surface morphologies, adhesion resistances and corrosion behaviors of the coatings were examined and the characterization of the coatings was performed by using XRD, SEM, and EDS. It was observed that porous and crack-free surface morphology enhanced adhesion strength of the coatings. Through the shear tests, it was found that the adhesion resistance was 25.14 MPa in HA coatings and 25.47 MPa in HA-SiO2 coatings. Corrosion analyses of the coatings were performed by using potentiodynamic polarization (PDS) tests. It was determined that corrosion dimples formed on the coating surface and the corrosion resistance in HA+SiO2 coatings increased with decreasing porosity; however, in the further steps of corrosion, it reached to the base material by causing a pitting effect on the coated surface. (C) 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved.