title: In vitro stability of plasma-sprayed hydroxyapatite coatings on Ti-6Al-4V implants under cyclic loading.
abstract: The success of hydroxyapatite (HA)-coated Ti-6Al-4V implants relies on the long-term stability of HA coatings. In this study, the mechanical stability of plasma-sprayed HA coatings on Ti-6Al-4V implants under four-point cyclic bending was systematically investigated in both air and simulated body fluid (SBF) environments at room temperature. To have a clear view of the microscale damage evolution, the surface morphology change of HA coatings during cyclic loading was carefully examined by scanning electron microscopy at the same locations on the coating surfaces after four-point bending for 4, 6.5, 8.5, and 10 million cycles. Also, possible changes of other characteristics such as thickness, weight, crystallinity, and residual stress of HA coatings were measured as a function of loading cycles. Up to 10 million cycles of bending in air and SBF, we found no significant microcracking or coating spalling on the surface of coatings, and no significant changes in thickness, weight, crystallinity, or residual stress of the plasma-sprayed HA coatings. The experiment results indicate that thickness and crystallinity had no effects on the stability of the HA coatings. HA coating resistance to the cyclic four-point bending might result from the stress shielding effects of preexisting microcracks in the coatings.
authors.affiliation: Department of Mechanical Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.
authors.forename: C
authors.initials: C
authors.lastname: Zhang
authors.forename: Y
authors.initials: Y
authors.lastname: Leng
authors.forename: X
authors.initials: X
authors.lastname: Zhang
mesh_terms: D001672:Biocompatible Materials; D020099:Coated Materials, Biocompatible; D006882:Hydroxyapatites; D019736:Prostheses and Implants; D019919:Prosthesis Implantation; D013499:Surface Properties
chemical_list: D001672:Biocompatible Materials; D020099:Coated Materials, Biocompatible; D006882:Hydroxyapatites