Effect of mechanical surface pretreatment on metal ion release

The degree of metal ion dissolution from Ti-6Al-4V alloy hip replacement st ems subjected to various mechanical and chemical surface pretreatments was analysed in vitro. High-dissolution rates were observed for nitric acid pas sivated samples that had been mechanically surface treated to increase the implant surface area. Significantly lower ion release levels were observed for mechanically treated samples which had been aged in de-ionised water. T he application of an hydroxyapatite coating decreased the metal ion release from the nitric acid passivated samples (compared to the uncoated sample) and increased the metal ion dissolution from the aged samples. The dissolut ion behaviour of the samples is explained in terms of the diffusion process es occurring at the stem/solution interface and the morphological and chemi cal characteristics of the surface treated stems. (C) 2000 Elsevier Science Ltd. All rights reserved.