A Method to Monitor Corrosion of Chromium-iron Alloys by Monitoring the Chromium Ion Concentration in Urine

摘要

Binary alloys of chromium-iron (Cr-Fe) are no longer used in dental and orthopaedic applications, and were used only for comparative purposes in the present study. Four kinds of Cr-Fe binary alloys, namely, 10 mass percent, 15 mass percent, 20 mass percent and 30 mass percent Cr in Fe, and 100 percent Cr and SUS316L were prepared. These metals were subcutaneously implanted into rats for four months. There was no significant difference in body weights and organ weights among control (sham-operation) and implant-groups, and no significant accumulation of Cr and Fe in the blood, liver or kidney of the alloy implant groups. To clarify the usefulness of urinary monitoring, the Cr and Fe concentrations in rat urine after implantation were analyzed. Alloy implant groups, including the SUS316L group, intended to excrete higher urinary Cr amounts than the control group during the 3 weeks after implantation. Urinary Cr and Fe amounts of the 15 percent Cr-alloy group showed especially high values in comparison not only with the control level but also the other alloy groups. The visual corrosion extents of the retrieved implants showed the following order: 10 percent Cr> 15 percent Cr> 20 percent Cr > 30 percent Cr > 100 percent Cr, SUS316L, and did not always correlate with the levels of the urinary amounts of Cr and Fe. From these findings, monitoring of urinary metal amounts is considered to he useful to monitor the in viva elution property non-invasively.