Effects of Autoclave Sterilization on Cyclic Fatigue Resistance in 5 Types of Rotary Endodontic Instruments: An In Vitro Study

Abstract

The research was supported by the funds of the scientific research project of the Faculty of Medicine of the University of Niš, which is financed by the Ministry of Education, Science and Technological Development of the Republic of Serbia (451-03-68/2022-14/200113) Conflict of interest: None declared Background:Rotary endodontic instruments are increasingly used in root canal treatment and have replaced stainless steel manual files. Cyclic fatigue is the cyclic loading of stress to produce deformation or fracture. This study aimed to evaluate and compare the effects of autoclave sterilization on cyclic fatigue in 5 types of rotary endodontic instruments. Material/Methods:ProTaper Universal, BioRace, ProTaper Next, Twisted File, and HyFlex CM instruments were included in this study. Each type included 96 instruments, divided into 4 groups according to the number of sterilization cycles (0, 1, 3, 5). After sterilization, each group of instruments was divided into 2 subgroups and tested for cyclic fatigue in 2 simulated canals (45 degrees both and 2 radii, 2 mm and 5 mm). The number of cycles to failure (NCF) was calculated, and statistical analyses were carried out using the t test, Mann-Whitney U test, and ANOVA, followed by the Tukey post hoc test (p<0.05). Fracture surfaces were analyzed using scanning electron microscopy (SEM). Results:Within the group of non-sterilized instruments, ProTaper Universal showed significantly lower resistance to cyclic fatigue compared to the other types of instruments (p<0.001). After repeated sterilization, a significantly higher mean of NCF was observed for BioRace (p<0.001), ProTaper Next (p<0.001), Twisted File (p<0.001), and HyFlex CM (p<0.001) compared to ProTaper Universal. The resistance of HyFlex CM was significantly higher compared to the other types of instruments (p<0.001). Conclusions:The findings from this study showed that autoclave sterilization of newer rotary endodontic instruments could increase resistance to cyclic fatigue.

Comparing the impact of various sterilization methods on the cyclic fatigue resistance, bending strength, and torsional fatigue properties of NiTi rotary files

“…These SS files have a higher risk of perforation, canal ledge or zip formation and even separation of file in the canal. This risk is more frequently observed in curved root canals [2][3][4]. In comparison to the SS file system, the NiTi file has not only reduced the working time but also effective in canal preparation [5].…”

“…The sterilization process for endodontic rotary files is absolutely crucial in eliminating bacteria, viruses, spores, and other microorganisms to avoid the risk of cross-infection [12]. Currently, the prevalent sterilization methods include the use of 5.25% of sodium hypochlorite, dry heat sterilization, glass bead sterilization and autoclaving [4,13]. Although, the researchers have conducted studies to investigate the impact of sterilization on the physico mechanical properties of rotary endodontic files, it is however still debatable whether it renders any detrimental effects on their physical and mechanical properties [14].…”

Scanning Electron Microscopic Analysis of Deformation of TruNatomy File Systems: An Ex-vivo Study

“…Thermal processing methods changed NiTi alloy transition temperatures [ 6 ]. The inherent properties of nickel-titanium endodontic instruments have been found to be enhanced by heat treatment by altering their transformation behaviour [ 7 ]. The preparation techniques have also been modified to prevent inherent procedural errors [ 8 ].…”