Mechanical and Metallurgical Evaluation of 3 Different Nickel-Titanium Rotary Instruments: An In Vitro and In Laboratory Study

Alessio Zanza; Paola Russo; Rodolfo Reda; Paola Di Matteo; Orlando Donfrancesco; Pietro Ausiello; Luca Testarelli

doi:10.3390/bioengineering9050221

Mechanical and Metallurgical Evaluation of 3 Different Nickel-Titanium Rotary Instruments: An In Vitro and In Laboratory Study

Bioengineering (Basel). 2022 May 20;9(5):221. doi: 10.3390/bioengineering9050221.

Authors

Alessio Zanza¹, Paola Russo², Rodolfo Reda¹, Paola Di Matteo², Orlando Donfrancesco^{1

3}, Pietro Ausiello⁴, Luca Testarelli¹

Affiliations

¹ Department of Oral and Maxillo-Facial Sciences, Sapienza University of Rome, Via Caserta 06, 00161 Rome, Italy.
² Department of Chemical Engineering, Materials, Environment DICMA, La Sapienza University of Rome, Via Scarpa, 00161 Rome, Italy.
³ Department of Anatomy, Histology, Forensic Medicine and Orthopedics, Sapienza University of Rome, 00161 Rome, Italy.
⁴ School of Dentistry, University of Naples Federico II, Via S. Pansini 5, 80131 Naples, Italy.

Abstract

An in-depth evaluation of the mechanical and metallurgical properties of NiTi instruments is fundamental to assess their performance and to compare recently introduced instrument with widespread ones. According to this, since there are no data on this topic, the aim of the study was to mechanically and metallurgically evaluate an instrument recently introduced into the market (ZenFlex (ZF)), by comparing it with two well-known instruments with similar characteristics: Vortex Blue (VB) and EdgeSequel Sapphire (EES). According to this, 195 instruments were selected: 65 ZF, 65 VB and 65 EES. Each group was divided in subgroups according to the mechanical tests (i.e., cyclic fatigue resistance, torsional resistance and bending ability; (n = 20)) and the metallurgical test (differential scanning calorimetry (n = 5)). A scanning electron microscopy was performed to verify the causes of fracture after mechanical tests (cyclic fatigue and torsional tests). According to results, VB showed the highest flexibility and cyclic fatigue resistance in comparison to the other instruments, with a statistically significant difference (p < 0.05). Regarding torsional resistance, EES showed the lowest value of torque at fracture, with a statistically significant difference, whilst the comparison between ZF and VB showed no statistically significant difference (p > 0.05). DSC analysis pointed out that VB had the highest austenite start and finish temperatures, followed by ESS and then ZF. ESS sample showed the highest martensite start and finish temperatures followed by VB and ZF. Considering the results, it can be concluded that VB showed the best mechanical performance during static tests in comparison to ESS and ZF. This is fundamentally due to the interaction of parameters such as instrument design and heat-treatments that are able to enhance its mechanical performance.

Keywords: Nickel-titanium Rotary Instruments; bending ability; cyclic fatigue; differential scanning calorimetry; endodontics; scanning electron microscopy; torsional strength.

Grants and funding

This research received no external funding.