Angle of Insertion and Torsional Resistance of Nickel–Titanium Rotary Instruments

Dario Di Nardo; Alessio Zanza; Marco Seracchiani; Orlando Donfrancesco; Gianluca Gambarini; Luca Testarelli

doi:10.3390/ma14133744

Materials (Jul 2021)

Angle of Insertion and Torsional Resistance of Nickel–Titanium Rotary Instruments

Dario Di Nardo,
Alessio Zanza,
Marco Seracchiani,
Orlando Donfrancesco,
Gianluca Gambarini,
Luca Testarelli

Affiliations

Dario Di Nardo: Department of Oral and Maxillo-Facial Sciences, Sapienza University of Rome, 00161 Rome, Italy
Alessio Zanza: Department of Oral and Maxillo-Facial Sciences, Sapienza University of Rome, 00161 Rome, Italy
Marco Seracchiani: Department of Oral and Maxillo-Facial Sciences, Sapienza University of Rome, 00161 Rome, Italy
Orlando Donfrancesco: Department of Oral and Maxillo-Facial Sciences, Sapienza University of Rome, 00161 Rome, Italy
Gianluca Gambarini: Department of Oral and Maxillo-Facial Sciences, Sapienza University of Rome, 00161 Rome, Italy
Luca Testarelli: Department of Oral and Maxillo-Facial Sciences, Sapienza University of Rome, 00161 Rome, Italy

DOI: https://doi.org/10.3390/ma14133744
Journal volume & issue: Vol. 14, no. 13
p. 3744

Abstract

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Previously published studies have investigated the influence of instrument access on cyclic fatigue resistance. However, no studies have evaluated the relationship between angulated access and torsional resistance. The aim of this study was to investigate the influence of the angle of access on the torsional resistance of endodontic instruments. One hundred and eighty instruments were selected: 90 F-One Blue 25/04 and 90 HeroShaper 25/04 instruments. Three subgroups (n = 30) for each instrument type (A and B) were established according to the angle of insertion of the instruments inside the artificial canal (0°, 10° and 20°). The tests were performed using a custom-made device consisting of the following: a motor that can record torque values of 0.1 s; interchangeable stainless-steel canals with different curvature (0°, 10° and 20°) that allow the instrument’s angulated insertion and keep it flexed during testing procedures; and a vise used to secure the instrument at 3 mm from the tip. Torque limit was set to 5.5 Ncm, and each instrument was rotated at 500 rpm until fracture occurred. Torque to fracture (TtF) was registered by the endodontic motor, and the fragment length (FL) was measured with a digital caliper. Fractographic analysis was performed using a scanning electron microscopy (SEM) evaluation to confirm the cause of failure. TtF values and fragment length (FL) values were statistically analyzed using one-way analysis of variance (ANOVA) test and the Bonferroni correction for multiple comparisons across the groups with significance set to a 95% confidence level. Regarding the F-One Blue instruments, the results showed a higher TtF for group A3 (20°) than for group A1 (0°) and group A2 (10°), with a statistically significant difference between group A3 and the other two groups (p p > 0.05). Regarding the HeroShaper instrument, the results showed the highest TtF for group B3, with a statistically significant difference between the three subgroups B1, B2 and B3 (p < 0.05). The results showed that the torsional resistance increases as the angle of instrument access increases with a varying intensity, according to the crystallographic phase of the instrument selected.

Published in Materials

ISSN: 1996-1944 (Online)
Publisher: MDPI AG
Country of publisher: Switzerland
LCC subjects: Technology: Electrical engineering. Electronics. Nuclear engineering; Technology: Engineering (General). Civil engineering (General); Science: Natural history (General): Microscopy; Science: Physics: Descriptive and experimental mechanics
Website: http://www.mdpi.com/journal/materials/

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