Effects of sodium hypochlorite on nickel-titanium Lightspeed® instruments

Sodium hypochlorite is a major irrigant in endodontics, and nickel-titanium instruments are gaining in popularity, This paper investigated the corrosion of nickel-titanium Lightspeed(R) instruments in 1% and 5% NaOCl solutions, The instruments were immersed in ultrasonicated NaOCl solutions for varying times up to 1 h, Corrosion was determined by electrothermal absorption spectrometry in 100 mu L, aliquots of NaOCl. Background contamination of nickel in the 1% and 5% NaOCl solutions used was low, but high enough to interfere in detecting any increases in nickel after immersing the instruments. The amounts of titanium recorded in the 1% NaOCl solutions were insignificant. However, a statistically significant amount of titanium was detected from the Lightspeed instruments after immersion times of 30 and 60 min in 5% NaOCl, Clinically such instruments do not have an 'in situ' time of 30 min, and this corrosion map be considered irrelevant clinically.