Localized corrosion behaviour in simulated human body fluids of commercial Ni-Ti orthodontic wires.
The corrosion performances in simulated human body fluids of commercial equiatomic Ni-Ti orthodontic wires having various shape and size and produced by different manufacturers were evaluated; for comparison purposes wires made of stainless steel and of cobalt-based alloy were also examined. Potentiodynamic tests in artificial saliva at 40 degrees C indicated a sufficient pitting resistance for the Ni-Ti wires, similar to that of cobalt-based alloy wire; the stainless steel wire, instead, exhibited low pitting potential. Potentiodynamic tests at 40 degrees C in isotonic saline solution (0.9% NaCl) showed, for Ni-Ti and stainless steel wires, pitting potential values in the range approximately 200-400 mV and approximately 350 mV versus SCE, respectively: consequently, according to literature data (Hoar TP, Mears DC. Proc Roy Soc A 1996;294:486-510), these materials should be considered potentially susceptible to pitting; only the cobalt-based alloy should be immune from pitting. The localized corrosion potentials determined in the same environment by the ASTM F746 test (approximately 0-200 mV and 130 mV versus SCE for Ni-Ti and stainless steel, respectively) pointed out that for these materials an even higher risk of localized corrosion. Slight differences in localized corrosion behaviour among the various Ni-Ti wires were detected.
Rondelli
G
G
CNR-TEMPE, Milano, Italy.
Vicentini
B
B
D003343:Corrosion; D003722:Dental Alloys; D006801:Humans; D066298:In Vitro Techniques; D007552:Isotonic Solutions; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D009532:Nickel; D009969:Orthodontic Wires; D012464:Saliva, Artificial; D012965:Sodium Chloride; D014025:Titanium
D003722:Dental Alloys; D007552:Isotonic Solutions; D012464:Saliva, Artificial; C040654:titanium nickelide; D012965:Sodium Chloride; D009532:Nickel; D014025:Titanium