Effect of various single file systems on microcrack formation in root canals: Scanning electron microscope study

Abstract

Background: The aim of this study was to compare dentinal crack formation in root canal walls
following 3 single file systems with continuous rotation under a scanning electron microscope (SEM).
Materials and Methods: In this SEM study, seventy mandibular premolars were randomly divided
into 5 groups. 3 experimental groups (n = 20) and 2 control groups (n = 5) as follows: Group I:
Neolix NiTi file system, Group II: OneShape systems, Group III: OneCurve file system, positive
control: conventional Hand File system, negative control: unprepared. After root canal preparations,
the roots were sectioned at 3, 6, and 9 mm from the apex with water irrigation. The sections were
inspected in all directions under SEM at × 100 magnification to determine the presence of cracks.
The Chi‑square test was used to analyze the data. There is a statistically significant difference in
the crack formation between the apical third (P = 0.012) and coronal third (P = 0.002) when
comparing all the 5 groups. No significant difference is found in the middle third (P = 0.46). P < 0.05
is considered statistically significant.
Results: Maximum cracks in the apical third were seen with One Shape file 11 (55%) and in the
coronal third with Neolix NiTi 14 (70%). There is a statistically significant difference in the crack
formation only in OneCurve when comparing the apical, middle, and coronal third for the individual
group (P = 0.042).
Conclusion: There was a significant difference in crack formation in apical and coronal third.
OneCurve caused the least incidence of cracks when compared to other file systems. OneCurve
file system can be a choice for canal preparation over Neolix Niti and OneShape.
Key Words: Dentin, electron scanning microscopy, endodontics, nickel–titanium alloy, root
canal