Improved tribo-mechanical behavior of CaP-containing TiO2 layers produced on titanium by shot blasting and micro-arc oxidation

Abstract

The combination of shot blasting (SB) and micro-arc oxidation (or anodic oxidation--AO) in titanium surfaces was shown to provide enhanced conditions for cell differentiation and osseointegration than those provided by SB or AO alone. This study associated both methods aiming to attain titania layers on Ti with adequate tribo-mechanical features for bone implants. SB was performed using alumina particles, and titania layers were grown by AO using a CaP-based electrolyte. Mechanical properties and scratch resistance were characterized at nanoscale by instrumented indentation and nanoscratch, and correlated with morphological and microstructural changes (XRD, SEM, EDS, AFM, and profilometry). Analytical methods were employed to correct roughness and substrate effects on the indentation results. CaP-containing TiO2 layers were produced on AO and SB + AO. The latter presented small pore size and inhomogeneous layer thickness and Ca/P ratios, caused by the non-uniform surface straining by SB that affects the oxide growth kinetics in the electrochemical process. Elastic modulus of SB + AO layer (37 GPa) were lower than the AO one (45 GPa); both of them were smaller than bulk Ti (130 GPa) and close to bone values. The hardness profiles of AO and SB + AO were similar to the substrate ones. Because of the improved load bearing capacity and unique layer features, the critical load to remove the SB + AO titania coating in scratch tests was three times as much or higher than in AO. Results indicate improved mechanical biocompatibility and tribological strength of anodic titania layers grown on sand blasted Ti surfaces.

Surface-treated commercially pure titanium for biomedical applications: Electrochemical, structural, mechanical and chemical characterizations

“…Depassivation zones were noted for the sandblasted groups in the potentiodynamic curves. According to Szesz et al [54] sandblasting procedure forms numerous defects onto the Ti surface. The higher the number of defects at the surface, the more the nucleation sites for the formation of defective passive layer [55].…”

“…The non-uniform surface caused by sandblasting method creates irregular surface roughening, and some regions are more susceptible do oxidation. After the passive layer is established, saliva ions can degrade the oxide layer, dominating the corrosion process [54].…”

Corrosion resistance and cytocompatibility studies of zinc-doped fluorohydroxyapatite nanocomposite coatings on titanium implant

“…Moreover, these implants may not promote osteoconductive and osteoblastic phenomena in the host body. Fortunately, the Ti-cp implant osseointegration can be stimulated by surface treatments, such as sand blasting [4], acid etching [5], plasma electrolytic oxidation [6] and hydroxyapatite [HA, Ca 10 (PO 4 ) 6 (OH) 2 ] coatings [7]. Amongst these treatments, artificial HA coatings are widely employed to promote bone ingrowth because of their osteoconductivity and bioactivity.…”

“…Improvement of biological and physicochemical properties of HA can be achieved by doping with ions that are usually present in natural apatites of vertebrate skeletal systems [8]. A wide variety of anions, cations and functional groups, such as Na + [9], Sr 2+ [10], Zn 2+ [11], Mn 2+ [12], SiO 4 4− [13], F − [14], Cl − [15], and CO 3 2− [16], can be introduced into the single phase HA lattice. Amongst these substitutions, zinc and fluorine are widely considered as potential substituents because of their biological relevance [17].…”

“…Fluorine equally acts as a good nucleation agent for apatite; this element promotes skeletal formation process [20]. Therefore, fluoridated hydroxyapatite [FHA, Ca 10 (PO 4 ) 6 (OH) 2-x F x , where 0 < x < 2] was designed as a probable candidate for HA replacement in orthopaedic 4 applications [14]. FHA shows high phase stability that is caused by OH − replacement by F − , which leads to contraction in the a-axis without changing the c-axis.…”