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Abstract
Titanium implants were occasionally found to be strongly discoloured after autoclaving.
The discolouration is shown to be due to an accelerated growth of the surface oxide
that covers the implants. Oxide thicknesses up to 650 A have been observed, i.e. more
than ten times thicker than on normal implants. By applying surface sensitive spectroscopies
(SIMS and XPS or ESCA) it is also shown that these oxide films contain considerable
amounts of fluorine, alkali metals and silicon. Screening tests with alkali-halide
solutions identify fluorine as the impurity responsible for the accelerated oxide
growth. Discolouration after autoclaving can be observed for fluorine contaminations
down to the ppm level. In those cases where discolouration was observed in the clinical
situation, the source of fluorine was the textile cloths in which the titanium implant
storage box had been wrapped during the autoclaving procedure. The cloths contained
residual Na2SiF6 which had been used as an additive to the rinsing water used in the
last step of the cloth laundry procedure. Since the biocompatibility of titanium implants
is closely related to their surface oxides it is advisable to avoid all sources of
fluorine in the implant preparation procedures.