Abstract
Background. This study aimed to evaluate the effects of repeated sterilization cycles on the surface alterations of various nickel-titanium instruments, including ProTaper Next (PTN), TF Adaptive (TFA), HyFlex CM (HCM), and 2Shape (2S). Methods. Twenty-four new NiTi files of four different alloys were selected. The instruments in each group were divided into two equal groups, as follows: control and sterilization. The first group was chosen as the control without applying any sterilization procedure, while in group 2, five cycles of sterilization procedures were applied. The surface topographies were evaluated using scanning electron microscope (SEM) and atomic force microscope (AFM). The root mean square (RMS) and maximum height (MH) values and three-dimensional images were recorded. The data were analyzed with the Shapiro-Wilk test, one-way ANOVA, and post hoc Tukey tests. The statistical significance level was set at P ≤ 0.05. Results. Before the experiment, HCM demonstrated the highest RMS value, and 2S showed the lowest. After the procedures, the RMS and MH values deteriorated on the surface of PTX, TFA, and 2S (P < 0.001). The HCM was not affected by sterilization processes (P > 0.05). Conclusion. The initial irregularity on the surface did not affect the rate of alteration. The HCM files demonstrated superior surface properties after several cycles of sterilization. The PTN, TFA, and 2S presented similar surface responses after five cycles of autoclave sterilization.
Highlights
The infection control protocol is the most critical factor that makes instruments safe for re-use
TF Adaptive (TFA: SybronEndo, Orange, CA, USA) is a multi-file system manufactured by a twisting method using a special heat treatment R-phase of NiTi alloy.[5]
This study aimed to evaluate and compare the effects of repeated sterilization cycles on the surface alterations of ProTaper Next (PTN), TFA, HyFlex CM (HCM), and 2S instruments made of different alloys with different properties and production methods
Summary
The infection control protocol is the most critical factor that makes instruments safe for re-use. Different thermally treated NiTi alloys, like CM-Wire, M-Wire, T-Wire, and R-phase, have been introduced to optimize the transformation behavior of NiTi alloy microstructure, which affects the mechanical structure.[6,7,8] ProTaper (PTN: Dentsply Tulsa Dental Specialties, Tulsa, OK) is a multi-file preparation system manufactured by M-wire alloy that underwent a specific thermomechanical process.[9] TF Adaptive (TFA: SybronEndo, Orange, CA, USA) is a multi-file system manufactured by a twisting method using a special heat treatment R-phase of NiTi alloy.[5] HyFlex CM (HCM: Coltene/Whaledent, Inc, Cuyahoga Falls, OH, USA) is a multi-file preparation system and manufactured by CMWire, which is a shape memory NiTi termed ‘Controlled Memory.’ This file system is produced by a lower percentage of the nickel weight than most commercially available NiTi and recommended for multi-use after sterilization as claimed by the manufacturer.10,11 2Shape (2S; Micro‐Mega, Besancon, France) is a double-file system manufactured by T-Wire alloy, produced with proprietary heat treatment.[6]. The PTN, TFA, and 2S presented similar surface responses after five cycles of autoclave sterilization
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