Tissue reactions to implanted orthodontic wires in rabbits.

Tissue response to a Fe-Cr-Ni and a Co-Cr-Ni orthodontic wire, in the as-received state and with silver soldered joints, was investigated. Specimens with polytetrafluoroethylene (PTFE) as a reference material were implanted in the subcutaneous tissue of rabbits. Six rabbits were sensitized to nickel, four animals were sham-sensitized, and two were left untreated. The results showed that the as-received wires gave no tissue response relative to the PTFE control. In soldered specimens that were moderate to extreme reactions adjacent to the soldered joint and around the wire portion as well. The soldered Co-Cr-Ni wire elicited the most severe reactions, most pronounced in the nickel-sensitized animals. The agar overlay cell culture test of some retrieved implants showed pronounced cytotoxicity of the soldered specimens. Leachable toxic components of the silver solder seemed to be of major importance in the observed cell culture and tissue response to the soldered specimens.