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Influence of sodium hypochlorite on fracture properties and corrosion of ProTaper Rotary instruments
Author(s) -
Berutti E.,
Angelini E.,
Rigolone M.,
Migliaretti G.,
Pasqualini D.
Publication year - 2006
Publication title -
international endodontic journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.988
H-Index - 119
eISSN - 1365-2591
pISSN - 0143-2885
DOI - 10.1111/j.1365-2591.2006.01134.x
Subject(s) - sodium hypochlorite , cyclic stress , fracture (geology) , materials science , corrosion , galvanic cell , nickel titanium , corrosion fatigue , immersion (mathematics) , metallurgy , dentistry , composite material , chemistry , medicine , mathematics , organic chemistry , pure mathematics , shape memory alloy
Aim To evaluate the influence of immersion in NaOCl on resistance to cyclic fatigue fracture and corrosion of ProTaper NiTi Rotary instruments. Methodology A total of 120 new ProTaper NiTi Rotary files (F2) were randomized and assigned to three different groups of 40 each. Group 1 was the control group; 20 mm (excluding the shaft) of group 2 instruments were immersed in 5% NaOCl at 50 °C for 5 min; instruments in group 3 were completely immersed in 5% NaOCl at 50 °C for 5 min. All instruments were then tested for cyclic fatigue, recording the time in seconds to fracture. Data were analysed by the Kruskall–Wallis test and post‐hoc multiple comparisons ( P < 0.05). Micromorphological and microchemical analyses were also completed by means of a field emission scanning electron microscopy (SEM) on those instruments in group 3 that had undergone early fracture. Results Instruments in group 3 had a significantly lower resistance to fracture because of cyclic fatigue than those in groups 1 and 2 ( P < 0.001). In some instruments in group 3, early fracture occurred after only a few seconds of fatigue testing. SEM observations revealed evident signs of corrosion of the fractured instruments. Conclusion Group 3 had significantly reduced resistance to cyclic fatigue compared with instruments in groups 1 and 2. The phenomenon of early fracture may be attributed to galvanic corrosion induced by the presence of dissimilar metals, where one acts as the cathode of a galvanic couple, established when the instrument is immersed in NaOCl solution. The NiTi alloy may acts as the anode and thus undergoes corrosion.