Designing the Surface of Medical Devices

The most important properties of metal medical devices are i) biocompatibility, ii) mechanical strength and, in some cases, iii) reliable osseointegration. The surface of biodevices can be designed and then modified to improve these properties. After a brief review of the technologies used to modify the surface of metallic biodevices, some examples of surface treatments used to improve their properties are given. The effect of acid etching on the surface shape of the metal material to improve implant osseointegration, to produce a surface with more ‘valleys’ than ‘peaks’, a requirement for improved osseointegration, is shown. It is demonstrated that the “shape” of the surface can be easily and quantitatively measured by using appropriate roughness parameters. In addition, to reduce the risk of implant rejection, nanoscale reservoirs for controlled drug delivery can be formed on the previously acid-etched implant surface. To this end, the methods used to grow titania nanotube dental screws from commercially pure titania are presented. The shape and length of the nanotubes can be varied to increase or decrease the duration of drug delivery as required.