Investigation of boundary conditions for biomimetic HA deposition on titanium oxide surfaces

• Published in: Journal of materials science. Materials in medicine Vol. 20; no. 7; pp. 1401 - 1408
• Main Authors: Lindgren, M., Åstrand, M., Wiklund, U., Engqvist, H.
• Format: Journal Article
• Language: English
• Published: Boston Springer US 01.07.2009; Springer Nature B.V
• Subjects: Biomaterials; Biomedical Engineering and Bioengineering; Biomedical materials; Biomimetics - methods; Ceramics; Chemistry and Materials Science; Coated Materials, Biocompatible - chemistry; Composites; Crystallization - methods; Durapatite - chemistry; Glass; Materials Science; Materials Testing; Natural Materials; Oxidation-Reduction; Polymer Sciences; Regenerative Medicine/Tissue Engineering; Surface Properties; Surfaces and Interfaces; TECHNOLOGY; TEKNIKVETENSKAP; Temperature; Thin film coatings; Thin Films; Titanium - chemistry; Transplants & implants; Simulated Body Fluid; Titanium Oxide Surface; Rutile; Oxidise Sample; Physical Vapour Deposition
• ISSN: 0957-4530; 1573-4838; 1573-4838
• DOI: 10.1007/s10856-009-3709-1

To improve the clinical outcome of metal implants, i.e. earlier loading and reduction of the incidence of revision surgery, better bone bonding ability is wanted. One method to achieve this is to change the surface chemistry to give a surface that facilitates bone bonding in vivo, i.e. a bioactive surface. Crystalline titanium oxide has recently been proven to be bioactive in vitro and is an interesting option to the more common hydroxylapatite (HA) coatings on implants. A materials possible in vitro bioactivity is tested through soaking in simulated body fluid and studies of possible HA formation on the surface. For bioactive materials, the formed HA layer can also be used as a coating. The aim of the current paper is to investigate some boundary conditions for HA formation on crystalline titanium oxide surfaces regarding influence from coating thickness, soaking time and soaking temperature. The influence from soaking time and temperature on the HA growth were investigated on oxidised Ti samples, (24 h at 800°C) resulting in a rutile surface structure. The oxidised samples were tested at three temperatures (4, 37 and 65°C) and four times (1 h, 1 day, 1 week and 4 weeks). The influence from titanium coating thickness on the HA growth was investigated via depositing thin films of crystalline titanium dioxide on Ti plates using a reactive magnetron sputtering process. Four different PVD runs with coating thicknesses between 19 and 74 nm were tested. The soaking temperature had an effect on the HA formation and growth on both rutile surfaces and native oxide on Ti substrates. Higher temperatures lead to easier formation of HA. It was even possible, at 65°C, to grow HA on native titanium oxide from soaking in PBS. The coating quality was better for HA formed at 65°C compared to 37°C. All PVD-coatings showed HA growth after 1 week in PBS at 37°C, thus even very thin coatings of crystalline titanium oxide coatings are bioactive.