Improved bonding strength between TiO2 film and Ti substrate by microarc oxidation

Titanium (Ti) and its alloys have proved to be very suitable materials for load-bearing bioimplant applications. Unfortunately, Ti and its alloys exhibit poor osteoinductive properties like most metals. This drawback was recently addressed by modified titania (TiO2). However, the bonding strength between TiO2 and substrate is not very strong. Therefore, mechanical properties and biochemical stability are very important. Many techniques have been investigated for modifying the TiO2 layer. Microarc oxidation (MAO) represents a relatively new surface modification technique where thick, hard and anticorrosive oxide coatings can be easily and cost-effectively fabricated. In this study, various chemicals were used as the electrolyte for MAO. Hydroxyapatite (HA) suspension was prepared by dispersing HA powder in distilled water and adjusting the pH in the range of 4-11. Bonding strength between TiO2 film and substrate was determined by modified ASTM C-633 and the ability to form apatite was confirmed after MAO, by soaking in simulated body fluid (SBF). The bonding strength decreased when the electrolyte was changed, but increased with increasing voltage. Bioactivity was only present in NaOH-treated specimens. Copyright (C) 2010 John Wiley & Sons, Ltd.