Abstract
Background: The aim of this study was to analyze the influence of NiTi alloy in endodontic rotary instruments on cyclic fatigue resistance. Methods: One hundred and sixty-four (164) sterile endodontic rotary files were selected and distributed into the following study groups: A: 25.08 F2 ProTaper Universal (PTU) (n = 41); B: 25.06 X2 ProTaper Next (PTN) (n = 41); C: 25.08 F2 ProTaper Gold (PTG) (n = 41), and D: 25.06 ProFile Vortex Blue (PVB) (n = 41). A cyclic fatigue device was designed to conduct the static cyclic fatigue tests with stainless steel artificial root canals systems with 250 µm apical diameter, 60° curvature angle, 5 mm radius of curvature, 20 mm length, and 6% (25.06) and 8% taper (25.08). Failure of the endodontic rotary instrument was detected by a single operator through direct observation and was also filmed to allow measurement of the exact time to failure. Results were analyzed using the ANOVA test and Weibull statistical analysis. Results: All pairwise comparisons presented statistically significant differences between the time to failure for the NiTi alloy study groups (p < 0.001), except between the PTN and PVB study groups (p = 0.379). In addition, statistically significant differences between the number of cycles to failure for the NiTi alloy study groups (p < 0.001) were also observed. Conclusions: The NiTi CM-Gold wire alloy of the ProTaper Gold endodontic rotary files resulted in greater resistance to cyclic fatigue than ProFile Vortex Blue, ProTaper Next, and ProTaper Universal endodontic rotary files.
Highlights
Endodontic rotary files have experienced continuous development since nickel–titanium (NiTi) files were introduced in the 1980s [1]
This alloy improved the flexibility and strength properties of endodontic rotary files compared with conventional stainless-steel endodontic instruments [2], and it simplified the treatment of root canals by improving the speed, accuracy, and safety of root canal shaping [3]
Machado et al retrospectively reported a fracture incidence of ProTaper Universal endodontic rotary files of 4.4% in 1031 teeth, mainly in mandibular first (8.8%) and second (9.6%) molars [5]; Bueno et al reported no fractures in any of the 1104 Wave One Gold endodontic reciprocating files [6]
Summary
Endodontic rotary files have experienced continuous development since nickel–titanium (NiTi) files were introduced in the 1980s [1] This alloy improved the flexibility and strength properties of endodontic rotary files compared with conventional stainless-steel endodontic instruments [2], and it simplified the treatment of root canals by improving the speed, accuracy, and safety of root canal shaping [3]. The more martensitic crystalline structure of the NiTi alloy of Wave One Gold endodontic reciprocating files allows higher flexibility and resistance than conventional austenitic endodontic rotary files. Conclusions: The NiTi CM-Gold wire alloy of the ProTaper Gold endodontic rotary files resulted in greater resistance to cyclic fatigue than ProFile Vortex Blue, ProTaper and ProTaper Universal endodontic rotary files
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