Effect of Sterilization on Cyclic Fatigue Resistance of Proflexendo Endodontic Rotary Files

Effect of autoclave sterilization on the cyclic fatigue resistance of EdgeFile X7, 2Shape, and F-one nickel-titanium endodontic instruments

Background

Rotary nickel-titanium files have become the most commonly used engine-powered endodontic instruments due to their improvement in fatigue resistance and flexibility. The autoclaving is the most commonly used method for sterilization. However, the risk of instrument fracture, mainly due to cyclic fatigue during rotation within a curved canal, is still a matter of critical concern.

Aims

This study aimed to measure and compares the cyclic fatigue resistance of EdgeFile X7, 2Shape, and F-One files in a single curved simulated canal before and after autoclave sterilization.

Materials and Methods

Twenty-four files each of EdgeFile X7, 2Shape, and F-One files were used in this study. They were grouped as group A: EdgeFile X7, group B: 2Shape, and group C: F-One files. Then, each group was subdivided into two, sterilized and nonsterilized, subgroups. The files were tested using a custom-made artificial canal. The number of cycles to fracture (NCF) was calculated.

Statistical Analysis Used

One-way analysis of variance, post hoc Tukey's test, and independent t-test were used.

Results

In nonsterilized instruments, the NCF of the EdgeFile X7 group was significantly higher than that in the other groups (P < 0.05). In sterilized instruments, there was a nonsignificant difference in NCF between EdgeFile X7 and F-One files (P > 0.05). The NCF of 2Shape was significantly lower than other files (P ≤ 0.05) in sterilized and nonsterilized groups. The autoclaving significantly decreased (P ≤ 0.05) the cyclic fatigue resistance of the tested files.

Conclusions

EdgeFile X7 was the most fatigue resistant. Autoclaving reduced the cyclic fatigue resistance of the tested files.

Nitinol Type Alloys General Characteristics and Applications in Endodontics

A very extensive literature review presents the possibilities and needs of using, in endodontics, the alloys commonly known as nitinol. Nitinol, as the most modern group of engineering materials used to develop root canals, is equilibrium nickel and titanium alloys in terms of the elements’ atomic concentration, or very similar. The main audience of this paper is engineers, tool designers and manufacturers, PhD students, and students of materials and manufacturing engineering but this article can also certainly be used by dentists. The paper aims to present a full material science characterization of the structure and properties of nitinol alloys and to discuss all structural phenomena that determine the performance properties of these alloys, including those applied to manufacture the endodontic tools. The paper presents the selection of these alloys’ chemical composition and processing conditions and their importance in the endodontic treatment of teeth. The results of laboratory studies on the analysis of changes during the sterilization of endodontic instruments made of nitinol alloys are also included. The summary of all the literature analyses is an SWOT analysis of strengths, weaknesses, opportunities, and threats, and is a forecast of the development strategy of this material in a specific application such as endodontics.

Effect of autoclaving on the cyclic fatigue resistance of nickel-titanium rotary instruments: An in vitro study

Aim:

The aim of the study is to determine the effect of autoclaving on the cyclic fatigue resistance (CFR) in respect to three different rotary nickel-titanium (NiTi) systems.

Methods:

Three rotary NiTi files with different manufacturing process were selected and arranged into three groups. Group 1: Neolix Neoniti files (n = 15), Group 2: Edge Files (n = 15), Group 3: NeoendoFlex files (n = 15). Each group was then subdivided into three subgroups containing 5 samples each based on the number of cycles of autoclaving (0, 1, 5 cycles). The instruments were subjected to autoclave without usage. The files of size 25, taper 6%, and 25 mm length were taken. After the autoclaving cycles, the files were rotated in cyclic fatigue testing device with simulated canal curvature of 60° until file separation. Time taken for the instrument separation (in minutes) was multiplied by the number of rotations per minute to attain the mean number of cycles to failure for every file. The obtained results were subjected to statistical analysis using two-way ANOVA and Newman–Keuls multiple post hoc procedures.

Results:

Neolix Neoniti files exhibited the maximum CFR (98.80) than EdgeFiles (80.47) and Neoendo Flex files (41.80) (P = 0.0001). Reduction in CFR was observed with increase in the number of cycles of autoclaving (i.e., 0, 1, 5 cycles).

Conclusion:

Autoclaving has a negative influence on the CFR of the rotary NiTi files used. Neolix Neoniti files exhibited greater CFR than EdgeFiles and Neoendo Flex files.