Production and Characterization of a Bone-Like Porous Ti/Ti-Hydroxyapatite Functionally Graded Material
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JMEPEG https://doi.org/10.1007/s11665-020-05165-2
Production and Characterization of a Bone-Like Porous Ti/Ti-Hydroxyapatite Functionally Graded Material Eren Yılmaz, Feyza Kabatas¸ , Azim Go¨kc¸e
, and Fehim Fındık
(Submitted June 11, 2020; in revised form September 2, 2020; Accepted: 19 September 2020) A new kind of functionally graded material (FGM) that mimics the inner porous structure and outer dense layer of human bone was produced using powder metallurgy. The inner part of the FGM material (16 mm in diameter) has porosity of approximately 60%, and its mechanical properties are compatible with cortical bone; however, the shell (1.8 mm in thickness) is composed of a layer of Ti-10% wt. hydroxyapatite (HA) and shows hydrophilic behavior and improved biofunction. Elastic moduli of the core and shell layer were calculated as 18.99 and 42.98 GPa, respectively, and those values are compatible with that of cortical bone. Addition of HA to the shell had a significant effect on the wettability (81.6% decrease) and cell viability (46% increase). Furthermore, the porosity of the shell layer (28.88%) is similar to that of human cortical bone. It is concluded that the developed Ti-HA FGM has promising properties for implant applications. Keywords
functionally graded materials, implants, porous titanium/hydroxyapatite, powder metallurgy
1. Introduction Dental or orthopedic implants might be the only restoration option for those who suffer from joint inflammation, osteoporosis, cancer, trauma, or gum disease (Ref 1). Biomaterials used in implant applications must have various properties such as biocompatibility, high mechanical compatibility with bone, good binding with the surrounding tissues, support for new bone cell formation, and high resistance to biocorrosion (Ref 2). Titanium and its alloys are preferred over other metallic biomaterials (stainless steel, Co-Cr, etc.) because of properties such as comparatively low elastic moduli (80-140 GPa), high strength (transverse rupture strength 300-1000 MPa), relatively low density, non-toxicity, and high corrosion resistance. Although b-Ti alloys with relatively low elastic moduli have been studied in depth in recent years, the achieved elastic modulus values are still above that of bone, and this difference causes damage to the tissues surrounding the implant and results in the problem of implant loosening (Ref 3, 4). Recently, this problem has been overcome with the development of porous Ti and its alloys. However, another disadvantage of Ti and its alloys as biomaterials is the spontaneous formation of a biologically inert oxide layer on their surfaces. Therefore, Eren Yılmaz, Department of Welding Technology, Arifiye Vocational High School, Sakarya Applied Sciences University, 54187 Sakarya, Turkey; and Sakarya Applied Sciences University Materials Research Center (SUMAR), 54187 Sakarya, Turkey; Feyza Kabatas¸ and Fehim Fındık, Faculty of Technology, Department of Metallurgical and Materials Engineering, Sakarya Applied Sciences University, 54187 Sakarya, Turkey; and
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