Ultrastructural Analysis of the Surface of Endodontic Instruments after Immersion in Irrigating Solutions

Summary Introduction Separation (fracture) of endodontic instruments in the root canal during chemomechanical instrumentation is a complication that can compromise the final outcome of endodontic treatment. One of the most common factors that cause fatigue of endodontic instruments and consequent fracture is surface corrosion. The aim of this study was to investigate the ultrastructure of surface corrosion of endodontic instruments made of stainless steel and nickel-titanium after immersion in the most commonly used root canal irrigants. Material and Methods The study included 48 nickel-titanium and stainless steel endodontic hand files. All instruments were immersed in 5.25% sodium hypochlorite, 0.2% CHX and 17% EDTA. Surface corrosion was analyzed using a scanning electron microscope (SEM). Results Nickel-titanium instruments showed significantly higher susceptibility to corrosion after immersion in 5.25% sodium hypochlorite compared to stainless steel instruments (p<0,001). After immersion in 0.2% CHX corrosion damage was observed on both nickel-titanium and stainless steel instruments but the difference was not statistically significant (p=0.096). No corrosion was observed in both types of instruments after immersion in 17% EDTA. Conclusion The use of 5.25% NaOCl and 0.2% CHX as root canal irrigating solutions can cause serious corrosion changes on the surface of nickel-titanium and stainless steel endodontic instruments.