EFFECT OF PASSIVATION AND DRY HEAT-STERILIZATION ON SURFACE-ENERGY AND TOPOGRAPHY OF UNALLOYED TITANIUM IMPLANTS

The effects of nitric acid passivation (P) and dry heat-sterilization (S) on the surface topography and energy of unalloyed titanium were ex amined. Surfaces were treated using the following sequences: cleaned i n phosphoric acid (C), C and passivated (CP), CP and dry heat-steriliz ed (CPS), CPS and resterilized (CPSS), and C and dry heat-sterilized ( CS). Surface roughnesses were examined with atomic force microscopy (A FM) and mechanical profilometry. Critical surface tensions gamma(c) an d solid surface tensions gamma(t) were determined from contact angles of distilled water and diiodomethane. Analysis of micro-roughness usin g AFM revealed no statistically significant differences among most rou ghness parameters for the various treatment conditions. However, the C S samples had a lower ratio of real to projected surface area. Macro-r oughness analysis using mechanical profilometry showed that CPSS had l ower peak count (PC, i.e. number of peaks above the mean line) values than CP and CS; PC values for C surfaces were also lower than CS. Also , CPSS had higher macro-R-q values than C and CPS. Values of gamma(c) correlated positively with the non-polar/dispersive components of gamm a(t); values were highest with the CS specimens. Higher gamma(t) value s were found for the CPSS and CPS treated surfaces, reflecting greater polar contributions on these surfaces. Thus, P and S together resulte d in increased surface energy, which is thought to be a desirable surf ace property for bone implants. (C) 1998 Elsevier Science B.V.