title: Mechanical performance and osteoblast-like cell responses of fluorine-substituted hydroxyapatite and zirconia dense composite.
abstract: A fluorine-substituted hydroxyapatite (FHA) and zirconia (ZrO(2)) dense composite (50:50 by volume) was fabricated, and its feasibility for hard tissue applications was investigated in terms of its mechanical properties and osteoblast-like cell (MG63) responses in vitro. The incorporation of fluorine into the hydroxyapatite (HA) structure was highly effective in producing a completely dense apatite-ZrO(2) composite through a pressureless sintering route, by preventing the thermal degradation of the apatite and ZrO(2). The resultant FHA-ZrO(2) dense composite had excellent mechanical properties, such as flexural strength (310 MPa), fracture toughness (3.4 MPam(1/2)), hardness (10 GPa), and elastic modulus (160 GPa). The flexural strength and fracture toughness of the composite showed a noticeable improvement by a factor of approximately 4 with respect to the pure apatites (HA and FHA). The MG63 cellular responses to the composite were assessed in terms of the cell proliferation (cell number and [(3)H]-thymidine incorporation) and differentiation (alkaline phosphatase activity, osteocalcin, and collagen production). The cells on the FHA-ZrO(2) composite spread and grew well, and proliferated actively during the culture period. The expression of alkaline phosphatase, osteocalcin, and collagen by the cells on the composite showed a similar trend to that on the pure apatites, although slight down-regulations were observed, implying that the FHA-ZrO(2) 50:50 composite retains the osteoblastic functionality and traits of the pure HA ceramics to a high degree. This finding, in conjunction with the considerable improvements in mechanical properties, supports the extended use of this composite for hard tissue applications.
authors.affiliation: School of Materials Science and Engineering, Seoul National University, Seoul 151-742, Korea. hwkim@snu.ac.kr
authors.forename: Hae-Won
authors.initials: HW
authors.lastname: Kim
authors.forename: Jonathan C
authors.initials: JC
authors.lastname: Knowles
authors.forename: Long-Hao
authors.initials: LH
authors.lastname: Li
authors.forename: Hyoun-Ee
authors.initials: HE
authors.lastname: Kim
mesh_terms: D001672:Biocompatible Materials; D002454:Cell Differentiation / Q000502:physiology; D049109:Cell Proliferation; D017886:Durapatite / Q000737:chemistry; D005461:Fluorine / Q000737:chemistry; D006801:Humans; D008855:Microscopy, Electron, Scanning; D010006:Osteoblasts / Q000502:physiology*; D013997:Time Factors; D015040:Zirconium
chemical_list: D001672:Biocompatible Materials; D005461:Fluorine; D017886:Durapatite; D015040:Zirconium; C028541:zirconium oxide