Tissue reactions to implanted orthodontic wires in rabbits

Area of Science:

• Biomaterials Science
• Orthodontics
• Toxicology

Background:

• Orthodontic treatments commonly utilize metal alloys like iron-chromium-nickel (Fe-Cr-Ni) and cobalt-chromium-nickel (Co-Cr-Ni) wires.
• Soldering is sometimes used to join or modify orthodontic appliances, potentially altering material properties and biocompatibility.

Purpose of the Study:

• To investigate the tissue response to Fe-Cr-Ni and Co-Cr-Ni orthodontic wires, both in their original state and after silver soldering.
• To evaluate the cytotoxic effects of these materials, particularly in relation to nickel sensitization.

Main Methods:

• Subcutaneous implantation of wire specimens (Fe-Cr-Ni, Co-Cr-Ni, and polytetrafluoroethylene as control) in rabbits.
• Grouping of rabbits included nickel-sensitized, sham-sensitized, and untreated.
• Agar overlay cell culture tests were performed on retrieved implants.

Main Results:

• As-received wires showed no significant tissue reaction compared to the control material.
• Soldered specimens induced moderate to extreme tissue reactions around the joints and wire portions.
• The soldered Co-Cr-Ni wire caused the most severe reactions, particularly in nickel-sensitized rabbits.
• Cell culture tests revealed pronounced cytotoxicity of the soldered specimens.

Conclusions:

• Silver soldering significantly increases the adverse tissue response to orthodontic wires.
• Leachable toxic components from the silver solder are the primary cause of cytotoxicity and tissue reactions.
• Nickel sensitization exacerbates the negative effects of soldered orthodontic materials.