Tissue reaction around metal implants observed by X-ray scanning analytical microscopy

The soft tissues implanted with Cu, Ni, Fe, Ag, Ti, Ni–Ti, SUS304 and SUS316 wires were investigated with XSAM and compared with histological observation. The relationship between the distribution of dissolved metal elements and the tissue response was evaluated. Of the metals whose dissolution was clearly observed by XSAM, severe tissue damage was observed around Ni and Cu implants, while fibrous connective tissue was formed around the Fe implant. The concentration in surrounding tissue was estimated by XSAM using the newly prepared standard specimens. The dissolved concentration was approximately 10–20 m for Ni and Cu and was considered to be in the order of ten times higher in Fe. The results indicated that the toxicity at the same concentration was from greater Ni>Cu>Fe. For Ag, Ti, Ni–Ti, SUS304 and SUS316 implants, significant dissolution and severe tissue damage were not observed. The XSAM was especially useful to obtain the information of dissolution and distribution behavior of rare content of toxic and chemically unstable metals in the soft tissue.